Biology of Graft Incorporation

Elmar Herbst, Marcio B. V. Albers, Michaela Kopka, Humza Shaikh, Freddie H. Fu

Volume 1 | Issue 1 | April – Jun 2016 | Page 20-24

Author: Elmar Herbst [1], Marcio B. V. Albers [1], Michaela Kopka [1], Humza Shaikh [1], Freddie H. Fu [1]

[1] Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Pittsburgh, PA 15213-0802

Address of Correspondence

Prof. & Chair. Dr. Freddie H. Fu
Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Pittsburgh, PA 15213-0802.
E-mail: ffu@upmc.edu

Abstract

In order to achieve good long-term results after anterior cruciate ligament (ACL) reconstruction, appropriate graft-to-bone healing is essential. The ACL graft is most vulnerable to re-injury during the early post-reconstruction phase. This is due to the decrease in biomechanical properties that occurs throughout the remodeling and graft-to-bone healing process. These processes are highly dependent on the biological and mechanical environment of the knee. The majority of the evidence regarding graft-to-bone healing is based on animal research. However, radiographic and histologic studies in humans reveal a slow incorporation process, which must be respected in post-operative rehabilitation planning. Significant differences between the healing behavior of soft tissue and bone-tendon-bone grafts, as well as between auto- and allografts have been identified. While tendon-to-bone healing occurs with dense fibrous tissue, bone blocks become incorporated into the surrounding tunnels via primary bone healing. Consequently, bone-tendon-bone grafts reveal a different microscopic appearance and slightly faster tunnel incorporation than soft tissue grafts. In anatomic ACL reconstruction, postoperative rehabilitation protocols should be tailored to allow optimum graft-to-bone healing, thereby minimizing tunnel enlargement and risk of graft failure.
Key Words: anterior cruciate ligament, graft, healing, tendon to bone, bone to bone, biology

Introduction

The bony insertion of the anterior cruciate ligament (ACL) is comprised of four distinct zones: ligamentous tissue, non-calcified fibrocartilage, calcified fibrocartilage, and bone. This “enthesis” is responsible for effectively transmitting the forces from the elastic ligament to the stiff bone. Despite its well organized structure, the enthesis has limited vascularity and thereby poor healing capacity(16, 40). As a result, primary repair of a torn ACL has been shown to be ineffective in restoring knee kinematics and stability, and reconstruction of the ligament (with autogenous or allogenous tissue) has become the standard of care. Although the outcomes following ACL reconstruction are generally good, there remains a 7-10 % overall re-rupture rate which warrants further evaluation(11). Technical errors (most frequently malposition of the femoral tunnel) are the most common cause of graft failure(18). However, 3 – 27% of ACL re-ruptures are considered “biologic” graft failures, which occur due to inappropriate graft ligamentization and inadequate graft-to-bone tunnel healing(18).
In the early post-operative phase, the primary strength of an ACL graft is afforded by the means of femoral and tibial fixation. However, long-term stability and the ultimate success of ACL reconstruction are dependent mainly on the secondary mechanical properties of the graft – instilled through the remodeling and graft-to-bone incorporation processes28. The purpose of this review is to discuss the important aspects of graft-to-bone healing and highlight their clinical relevance in anatomic ACL reconstruction.

Figure 1: Magnetic resonance imaging (MRI) of a left knee of a 21-years old male patient one year after ACL reconstruction with an autologous quadriceps tendon grafts. A) Coronal T2-weighted coronal image with the arrow indicating the fibrous interface between the soft tissue graft and the bone tunnel. B) T1-weighted coronal cut with a homogenous intra-tunnel portion of the graft (arrow). C) T1-weighted sagittal image. At the distal part of the tibial bone tunnel the interference screw is visible. The arrow proximal to the interference screw highlights the fibrous interface in the anterior part of the bone tunnel.

Figure 1: Magnetic resonance imaging (MRI) of a left knee of a 21-years old male patient one year after ACL reconstruction with an autologous quadriceps tendon grafts. A) Coronal T2-weighted coronal image with the arrow indicating the fibrous interface between the soft tissue graft and the bone tunnel. B) T1-weighted coronal cut with a homogenous intra-tunnel portion of the graft (arrow). C) T1-weighted sagittal image. At the distal part of the tibial bone tunnel the interference screw is visible. The arrow proximal to the interference screw highlights the fibrous interface in the anterior part of the bone tunnel.

The four stages of graft incorporation
Analogous to the intra-articular graft remodeling process, graft-to-bone healing can be subdivided into four stages: 1) inflammatory phase, 2) proliferative phase, 3) matrix synthesis, and 4) matrix remodeling(16). The similarity ends there, however, as each stage is distinctly different between the two processes. During the initial inflammatory response, the ACL graft undergoes partial necrosis. This stimulates the release of a cocktail of growth factors, which induce the proliferative phase and promote neovascularization and nerve ingrowth. The matrix synthesis and remodeling phases result in bone or collagen fiber formation at the bone-tendon-bone (BTB) and soft tissue graft-tunnel interface, respectively(6, 16, 28, 39). This complex process is affected by a variety of biologic and technical factors. Of the technical – and thereby controllable – factors, graft type and tunnel position are likely the most important(5, 37).

The influence of different graft types
Animal studies
In general, both the ACL graft remodeling and incorporation processes are different and faster in animals compared to humans. Therefore, histologic and biomechanical data from animal studies cannot be directly transferred to humans and must be interpreted in the appropriate context.

Soft tissue graft incorporation
Incorporation of soft tissue ACL grafts begins with the development of granulation tissue and perpendicular collagen (Sharpey-like) fibers at the tendon-bone interface. This process usually occurs during the first 3-4 weeks. The granulation tissue surrounding the graft expresses high levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF), which leads to an increase in the amount of fibroblasts and blood vessels(14, 23). This rudimentary scar tissue is characterized by loose and poorly organized collagen types I, II, and III fibers. Over time, the amount of type II collagen decreases, and the remaining type I and III fibers become more dense and organized(14, 16, 26, 33).
The biology of the later stages of graft incorporation is less consistently reported in the literature. Some authors suggest that the graft becomes incorporated into the tunnel by woven bone as early as six weeks(19), while others have shown that dense collagen fibers predominate at the interface during this time33. The majority of the studies agree that bony ingrowth begins between 6-8 weeks(19, 23, 26). However, despite the formation of distinct cartilaginous (type-II collagen) tissue at the graft-tunnel interface, no direct insertion of fibrocartilaginous tissue is present at this time. Furthermore, the expression of VEGF, b-FGF, and collagen types II and III remains similar to the earlier stages of the incorporation process(13, 15, 26). At 12 weeks, a calcified cartilage zone similar to the native ACL insertion can be observed at the intra-articular tunnel aperture(19). This was demonstrated by Weiler et al., who showed that a mature fibrocartilaginous tendon-to-bone junction was present at 12 weeks in an interference-fit fixation study(29, 35). Others have disputed these findings, suggesting instead that the fibrocartilaginous tissue becomes more dense leading to bone tunnel sclerosis(33). The late stages of soft tissue graft incorporation are characterized by a decrease in cartilage metaplasia and resultant bony ingrowth (26). At six months following ACL reconstruction, significant ossification and formation of a four phase insertion can be observed at the graft-bone interface(19,35). This process continues along the length of the tunnel well beyond one year post-operatively. In a sheep model, Hunt et al. demonstrated that the intra-tunnel portion of the soft tissue ACL graft loses its tendinous structure and begins to show evidence of bony ingrowth at 2 years following reconstruction(10).

Bone-tendon-bone graft incorporation
Bone-to-bone healing is a different and much faster process than tendon-to-bone healing. During the first four weeks, granulation tissue develops at the bone graft-tunnel interface, and partial necrosis of the bone block occurs due to increased osteoclast activity(23, 33). Unlike soft tissue graft incorporation, only a small amount of fibrous tissue is formed(23). Studies have shown that BTB ACL grafts are at least partially incorporated into the tunnels after only 6 weeks(19, 23, 33). At 24 weeks, a fibrocartilaginous ligament-like insertion develops at the tunnel aperture, and by 6 months the graft is completely incorporated into the surrounding bone(38,19, 29).

Allograft incorporation
The intra-articular remodeling as well as the graft incorporation processes are much slower in allografts compared to autografts(3). Harris et al. investigated the graft-to-bone incorporation of BTB allografts in goats. At 18 weeks following surgery, they found no evidence of bony incorporation and only a connective tissue interface at the graft-tunnel junction. Not until 36 weeks did the bone blocks become fully incorporated(9).

Biomechanical consequences of graft incorporation and remodeling
Several studies have shown that the biomechanical properties of ACL grafts decrease steadily during the first few months following reconstruction(19). It is well documented that the intra-articular portion of the graft undergoes a distinct remodeling process that results in an initial decrease in strength and load to failure. However, the graft-to-bone incorporation must also be considered as a contributing factor to the overall decrease in the biomechanical properties seen in the early stages of graft healing.
In a canine model, the load to failure at three weeks following surgery was significantly lower in soft tissue compared to BTB grafts (p = 0.021). No significant difference was identified at six weeks. Interestingly, at 12 weeks, the soft tissue grafts exhibited a higher load to failure than the BTB grafts(33). Mayr et al. showed that all failures occurred in the mid-substance at six weeks and at the graft-tunnel junction at 3-6 months, regardless of graft type(19). These findings are supported by other studies, and suggest that intra-articular graft remodeling is more important early on, while graft incorporation becomes significant at the later stages of healing(23, 33). Given that graft remodeling and incorporation continue well beyond one year following surgery, the biomechanical properties correspondingly increase in this later time frame(14, 36).

Figure 2: Sagittal and coronal computed tomography image of a left knee of a patient six months after ACL reconstruction with an aoutologous quadriceps tendon with a patellar bone block in the femoral tunnel. The bone block is partially integrated in the surrounding bone (arrow). The bone tunnel is surrounded by a thin sclerotic wall (arrow).

Figure 2: Sagittal and coronal computed tomography image of a left knee of a patient six months after ACL reconstruction with an aoutologous quadriceps tendon with a patellar bone block in the femoral tunnel. The bone block is partially integrated in the surrounding bone (arrow). The bone tunnel is surrounded by a thin sclerotic wall (arrow).

Figure 3: T2-weighted MRI of a left knee of a patients four years following ACL revision with soft tissue allograft and a bony reaction with consecutive tibial bone tunnel widening due to a fixation device. The graft in the bone tunnel is not homogenous and surrounded by irregular fibrous tissue. At the proximal part of the bone tunnel an evident synovial influx is visible.

Figure 3: T2-weighted MRI of a left knee of a patients four years following ACL revision with soft tissue allograft and a bony reaction with consecutive tibial bone tunnel widening due to a fixation device. The graft in the bone tunnel is not homogenous and surrounded by irregular fibrous tissue. At the proximal part of the bone tunnel an evident synovial influx is visible.

Histological findings in humans
The evidence surrounding graft-to-bone healing in humans is limited to a few case series, and therefore it is difficult to draw definitive conclusion from the data. Nevertheless, it is important to consider some of the key differences observed in human patients.

Hamstring tendon grafts
The process of soft tissue autograft incorporation into the surrounding bone tunnel is through formation of woven bone, which is penetrated by type I and III collagen fibers(24). In the first three months following reconstruction, the graft-bone interface consists primarily of dense, vascularized fibrous tissue surrounded by a layer of calcified osteoid. In this early phase, the fibrous tissue has no direct contact to the surrounding lamellar bone(25). At 5-6 months, the graft becomes surrounded by irregular fibrovascular granulation tissue with some areas of woven bone. Sharpey-like fibers begin to connect the graft to the bone, however, there is no evidence of bony ingrowth at this time(20, 25). Histological analyses of the graft-bone interface at 8-12 months following ACL reconstruction with hamstring tendon autograft show a firm attachment of the tendinous graft to the bone in some studies, and a persistent fibrous attachment in others(25,20). At one year following surgery, histological analyses show ongoing maturation of the graft-bone interface with an increase in Sharpey-like fibers and some evidence of peripheral bony ingrowth(20, 25).

Bone-tendon-bone grafts
In bone-tendon-bone grafts, the four-phase insertion of fibrocartilage can be preserved by ensuring that the bone plug rests flush with the intra-articular tunnel aperture. In this instance, the BTB graft becomes incorporated into the tunnel by direct bone healing. When the bone plug is recessed within the tunnel, the tendon-bone interface becomes incorporated via fibrocartilage(24). Ishibashi et al. performed histological analyses on the BTB graft-tunnel interface in patients who had undergone primary ACL reconstruction. Prior to one year from the time of surgery, granulation tissue was present between the tendinous portion of the graft and the bone tunnel. After one year, the granulation tissue was replaced by fibrous tissue containing collagen fibers, but without an obvious fibrocartilaginous insertion. The bone block, in contrast, was completely incorporated and could not be distinguished from the surrounding bone by one year postoperatively(12).

Imaging of graft incorporation
The incorporation of BTB grafts into the surrounding bone can be readily evaluated by computed tomography (CT) and magnetic resonance imaging (MRI) (Fig. 1, Fig. 2). Suzuki et al. used CT scans to show that the majority of BTB grafts were near-completely incorporated within the bone tunnel by eight weeks post-operatively(31). In contrast, the use of imaging to assess graft-to-bone healing of soft tissue grafts is much more demanding. A high resolution MRI can often be helpful in visualizing the remodelling and bone incorporation process8. However, accurate assessment of graft revascularization requires the use of contrast-enhaced MRI or MR angiography.
MRI studies have shown that the revascularization process peaks at two months following ACL reconstruction and then decreases steadily over time(32). Interestingly, revascularization of BTB grafts is significantly faster in the intra-articular portion of the graft compared to the intra-tunnel segment. A recent MRI study revealed that revascularization of the intra-tunnel portion of the BTB graft persists beyond one year after surgery, suggesting that bone-to-bone incorporation may be slower than initially demonstrated by histological studies(21). Similar results were obtained when investigating the revascularization of soft tissue autografts(22, 27).

Clinical implications of incomplete graft incorporation
Early return to function is a common goal following ACL reconstruction and modern rehabilitation protocols have been tailored accordingly. Range of motion exercises and gentle strengthening are important to maintain quadriceps function and mitigate the risk of arthrofibrosis. While femoral and tibial fixation techniques are responsible for maintaining graft strength in the early postoperative period, it is the graft remodeling and graft-to-bone incorporation processes that determine the long-term stability success of an ACL reconstruction4.
An important clinical problem in graft-to-bone incorporation is tunnel enlargement (Figure 3). Although this is a multi-factorial issue, one contributing factor is the discrepancy of the healing process across different segments of the bone tunnel. Studies show that the number of osteoclasts as well as their activity level is higher at the intra-articular bone tunnel aperture1. Consequently, bony ingrowth occurs preferentially at the peripheral end of the bone tunnel(2). This in combination with an increased graft motion near the intra-articular tunnel aperture can result in tunnel widening and impaired graft-to-bone healing(26). This finding is corroborated by a number of clinical studies(34), whereas others found that bone tunnel widening does not influence graft incorporation(17).
Another issue which may predispose to tunnel enlargement is the graft bending angle. In anatomic ACL reconstruction, a bend develops as the graft transitions from the intra-articular portion into the tunnel. Particularly with soft tissue grafts, this results in an asymmetric position of the graft at the tunnel aperture and formation of a gap between the graft and the tunnel wall(7). Synovial fluid and osteoclasts can enter this space and stimulate tunnel widening.
Finally, the position of the bone socket plays a critical role in the motion of the graft within the tunnel(30). This was demonstrated by Ekdahl et al., who showed that bone tunnel enlargement is significantly decreased in anatomic ACL reconstruction compared to non-anatomic tunnel placement. The non-anatomic reconstructions revealed an increased amount of osteoclasts and a decreased amount of vascularization compared to the anatomic reconstructions(5).

Conclusions

Successful graft-to-bone incorporation plays an integral role in the long-term outcomes following ACL reconstruction. Animal studies provide some understanding of this complex process and highlight the differences between graft and tissue types. However, the results of animal studies are not analogous to human data, which reveals a distinct and much slower incorporation process. The available evidence suggests that anatomic ACL reconstruction and likely a less aggressive rehabilitation protocol are both important variables in optimizing graft incorporation and improving patient outcomes.

References

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13. Kanazawa T, Soejima T, Murakami H, Inoue T, Katouda M, Nagata K. An immunohistological study of the integration at the bone-tendon interface after reconstruction of the anterior cruciate ligament in rabbits. J Bone Joint Surg Br. 2006;88(5):682-687.
14. Kondo E, Yasuda K, Katsura T, Hayashi R, Kotani Y, Tohyama H. Biomechanical and Histological Evaluations of the Doubled Semitendinosus Tendon Autograft After Anterior Cruciate Ligament Reconstruction in Sheep. Am J Sports Med. 2012;40(2):315-324.
15. Liu SH, Panossian V, al-Shaikh R, et al. Morphology and matrix composition during early tendon to bone healing. Clin Orthop Relat Res. 1997(339):253-260.
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17. Lui PPY, Lee YW, Mok TY, Cheuk YC. Peri-tunnel bone loss: does it affect early tendon graft to bone tunnel healing after ACL reconstruction? Knee Surg Sports Traumatol Arthrosc. 2013;23(3):740-751.
18. Magnussen RA, Trojani C, Granan LP, et al. Patient demographics and surgical characteristics in ACL revision: a comparison of French, Norwegian, and North American cohorts. Knee Surg Sports Traumatol Arthrosc. 2015;23(8):2339-2348.
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22. Ntoulia A, Papadopoulou F, Zampeli F, Ristanis S, Argyropoulou M, Georgoulis A. Evaluation with contrast-enhanced magnetic resonance imaging of the anterior cruciate ligament graft during its healing process: a two-year prospective study. Skeletal Radiol. 2012;42(4):541-552.
23. Papageorgiou CD, Ma CB, Abramowitch SD, Clineff TD, Woo SL. A multidisciplinary study of the healing of an intraarticular anterior cruciate ligament graft in a goat model. Am J Sports Med. 2001;29(5):620-626.
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How to Cite this article:. Herbst E, Albers M,  Kopka M, Shaikh H, Fu FH, . Biology of Graft Incorporation. Asian Journal of Arthroscopy  Apr- June 2016;1(1):20-24 .

Dr. Elmar Herbst

Dr. Elmar Herbst

Dr. Marcio B. V. Albers

Dr. Marcio B. V. Albers

Dr. Michaela Kopka

Dr. Michaela Kopka

Dr. Humza Shaikh

Dr. Humza Shaikh

Prof. Freddie H. Fu

Prof. Freddie H. Fu

 

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Synthetic Grafts in Anterior Cruciate Ligament Reconstruction

Jonathan Herald, Sagar Kakatkar

Volume 1 | Issue 1 | April – Jun 2016 | Page 16-19

Author: Jonathan Herald [1], Sagar Kakatkar [1]

[1] Orthoclinic, Sydney, Australia.
[2] Dr. Vasantrao Pawar Medical College and Hospital, Nashik, India.

Address of Correspondence

Dr. Sagar Kakatkar
Orthoclinic Sydney, Suite 1606, Level 16, 109 Pitt Street
Sydney NSW 2000 Sydney, Australia

Abstract

Immediate post-operative knee stability and early return to pre-injury activities are two goals of ACL reconstruction today. Autografts and Allografts when used for the ACL reconstruction are based on a principle of graft incorporation in the tunnels which renders them inefficient in providing immediate stability after the surgery. Since post-operative rehabilitation protocols after allograft or autograft ACL reconstruction are designed to protect the grafts for a certain period, early return to pre-injury functional status is not possible. Apart from these disadvantages, graft related complications and availability of the grafts are problems for both autografts and allografts. Synthetic ACL substitutes have been developed, modified and re-modified according to the clinical outcomes and reported complications. And although few of them have shown early promising results, whether they can stand the test of time or not is still to be seen.
Key words: Anterior cruciate Ligament (ACL), Ligament Advanced Reinforcement System (LARS), Synthetic grafts, Tissue engineering, Leeds-Keio artificial ligament, ligament augmentation device(LAD)

Introduction

Improving the quality of life has been the principle focus of modern health care. Correspondingly, evaluation criteria for surgical outcomes have also changed. Achieving post-operative stability is no longer the only goal after ACL reconstruction; but ‘Early’ and ‘Sustained’ return to pre injury levels of activities is now considered as the measuring tool for success. ACL injury is the most common knee ligamentous injury in sports related activities and a delay in returning to sports is enough to ruin a sportsman’s career. Autografts and Allografts have been the main graft choices for ACL reconstruction. Autografts have shortcomings such as inadequate graft length or diameter and donor site morbidity while; allografts on the other hand have problems of allogenicity, insufficient supply of grafts, high costs, etc. A common disadvantage that both these grafts share is the requirement of integration of the graft in the osseous tunnels. Time required for this integration process is variable and subjective and is more for allografts than autografts (14).
Extensive research has been done to overcome these problems associated with autografts and allografts and to develop a suitable synthetic substitute for ACL reconstruction. But since 1918 when Alwyn- Smith tried ACL reconstruction with silk sutures for the first time, use of synthetic grafts for the ACL reconstruction has been a tale of failures(16).

Expectations from Synthetic grafts and the their Evolution
Synthetic graft technology has evolved from non-biological to biological grafts. The grafts are developed so as to have better strength compared to native ACL. Their use is designed to reduce not only the donor site morbidity but surgical time also. The greatest function which they are supposed to serve is to provide immediate post-operative stability to the knee thus promoting early mobilization, faster rehabilitation and quicker return to pre injury level activities.
The synthetic replacements that have been used for the ACL can be broadly classified into three types which also follows their chronological order(16).
Class 1: Graft Fibers:
These include fibers of polyethylene, PTFE (Polytetrafluoroethylene). These were one of the few earlier graft substitutes and had high failure rates because of graft breakage.
Class 2: Ligament Augmentation devices (LAD):
These include polypropylene polyesters which were strong. These devices were used along with ACL autografts or allografts and were supposed to provide immediate structural support to the grafts so that to enhance their integration. But unfortunately these augments caused ‘stress shielding’ and led to delayed graft integration thus leading to higher incidences of graft failures.
Class 3: Prosthetic materials:
The earlier generations of these prostheses did not allow any soft tissue ingrowth and thus although they had good early functional results, the long term follow ups reported high failure rates. Second generation prostheses developed were based on the principles of combining structural properties of prosthetic material with tissue engineering to develop scaffolds for ACL reconstruction. These were supposed to provide good initial strength and then allow gradual soft tissue ingrowth for longevity. Following are the different types of prosthetic materials used clinically:

 

Figure 1 & 2: Show how the graft passage for the LARS should be sequential and gradual so as to correctly position the intraarticular and intraosseous parts of the LARS in their proper positions.

4. fig1 n2

Figure 1 & 2: Show how the graft passage for the LARS should be sequential and gradual so as to correctly position the intraarticular and intraosseous parts of the LARS in their proper positions.

a) Carbon based prosthetic devices: These allowed collagen ingrowth but histopathological studies of the tissues tested showed accumulation of carbon particles in the lymphatic system of the individuals. Also these had high incidences of graft ruptures, disintegration and failures, so were discontinued.
b) Gore-Tex: These were probably the strongest synthetic graft substitutes which included expanded Polytetrafluoroethylene fiber looped on itself. Their use in ACL reconstruction had good functional outcomes and hence gained the FDA approval for use in patients with failed autologous intraarticular graft procedures i.e. for revision cases. However long term follow up showed increased incidences of loosening of the grafts which led to detrimental functional outcomes.
c) Leeds- Keio Artificial Ligament: Was developed by Fujikawa and Seedhom. This was one of the most popular synthetic substitute for the ACL reconstruction because of good early functional outcomes. The ligament was composed of a polyester mesh with tibial and femoral bone plugs attached for anchorage in the tunnels. It provided good soft tissue ingrowth and had good shear resistance. But because of its high tensile strength it acted as mainly a load bearing prosthesis and had poor long term results. There were many clinical studies reporting long term graft failures (8).
d) Kennedy ligament augmentation device (LAD): The good clinical results of LAD as reported by its developers were non reproducible and this synthetic substitute led to post-operative synovitis due to its Polypropylene structural units. The implant graft interface when used as an augmentation device was the weakest area of the construct and thus had graft failures.
A Landmark study done by Marie –France Guidoin, et al.(13) reported causes of failures in 117 synthetic ligamentous prosthesis which had failed either because of the rupture or recurrent synovitis. The type of prostheses excised include Gore-Tex, Kennedy LAD, PET based prostheses, etc. These prostheses were tested under scanning electron microscope (SEM) and following three mechanisms involved in the failure of these ACL prostheses were noted. 1) Failure because of inadequate fiber abrasion resistance against osseous structure 2) Flexural and rotational fatigue of the fibers 3) Loss of integrity of the textile structure due to tissue infiltration during healing. The second and third mechanism of failure were the most difficult problems to address.
e) LARS (Ligament Advanced reinforcement system): This is the latest development in the synthetic ligament substitutes. It consists of polyethylene tetraphthalate (PET) as the structural component. The LARS has been designed to mimic ligamentous anatomy. It has 2 parts i.e. intra articular and intraosseous part. The intraosseous part is composed of longitudinal fibers of PET held together with transverse knitted structure. While the intraarticular part has parallel longitudinal fibers of PET twisted perpendicular to each other. These parts should be aligned perfectly while doing the ACL reconstruction to avoid early graft failures (Figure 3). The orientation of the fibers is modified to be side specific i.e. different for left and right knees thus mimicking the 3D cross-sectional anatomy of intraarticular part the native ACL. This is supposed to help overcome rotational fatigue of the synthetic ligament. Although this is a far superior structural construct compared to other synthetic substitutes, getting the LARS intraosseous part and intraarticular part exactly in their place during the surgery requires excellent surgical skill (Figure 1 and 2). The LARS also promotes tissue ingrowth(17).

Figure 3: Arrangement of the LARS-autograft construct during ACL reconstruction (Figure3 Courtesy: Athens Sports Medicine, Greece)

Figure 3: Arrangement of the LARS-autograft construct during ACL reconstruction (Figure 3 Courtesy: Athens Sports Medicine, Greece)

 

Figure 4 & 5: Ruptured LARS with Secondary arthritis of the knee joint evident on MRI films

fig4

Figure 4 & 5: Ruptured LARS with Secondary arthritis of the knee joint evident on MRI films

 

Several studies considering the outcomes following LARS for the ligamentous reconstruction showed good to excellent functional outcomes and good patient satisfaction (4, 7, 9, 10, 12, 15). A few of the papers even rated LARS as better than the autograft ACL reconstructions (9,6, 18). Histopathological studies do support the cellular ingrowth with LARS acting as a scaffold (17).
If return to pre injury level is considered as the criteria for success, few studies report LARS enabling patients to go back to active sports related activities within 2-3 months of the surgery (19). But the study done by Zuzana Makotka et al. in 2010 which was a meta-analysis of the literature published on LARS for ACL reconstruction from year 2000 to 2010 showed that none of the studies done on LARS autologous ‘ligamentous’ healing along the synthetic meshwork of LARS. Even though LARS is thought to reduce the surgical time, none of the studies had commented about the duration of surgery with the LARS ACL reconstruction. None of the study compared return to previous level of function with LARS and with traditional ACL reconstruction. This metaanalysis was based on the 4 studies and also stated that LARS may not be good for chronic ACL injuries as in such cases quality of remnant of the ACL i.e. ACL stump is not good and LARS may not have good ligamentous ingrowth on fibrotic stump.
Considering the latest literature, Alberto et al. in their study published in 2014 showed that a few patients with failed reconstruction with Polyethylene tetraphthalate (PET) synthetic grafts (1). Fourteen of such patients underwent revision surgery performed as two-staged revision. All these patients has histopathological evidence of granulomatous reaction due to PET. And even the revision surgeries done with the autografts did not improve functional status of these patients or stop the progressive Osteoarthritis occurring in these patients. In another study the rate of failure of LARS in a 19 year outcome study was reported to be 27.5% with 100% patients presenting with degenerative arthritis (2).A few other studies report disabling synovitis secondary to LARS ACL reconstructions (5).
Hence till date, the literature regarding the LARS remains controversial and there are no studies comparing early on long term outcomes of the LARS and those with autograft/ Allograft ACL reconstructions.
In authors practice, several cases treated by LARS ACL reconstruction elsewhere, which are symptomatic either because of graft loosening or graft failure have been encountered(Figure 4,5,6). Of those patients who underwent revision surgeries, histopathological examination of the synovial tissue collected during surgery showed chronic granulomatous inflammation and the patients, in spite of attaining knee stability continued to have symptoms due to inflammatory synovitis and progression of arthritis. When tested using new battery of tests which used to evaluate return to sports status of the patients with ACL reconstruction; patient’s ability to return to sports related activities was better in patients treated with autograft ACL reconstruction than LARS ACL reconstruction and further evaluation of these patients is being done (4).
Apart from studies on LARS, latest literature which is a randomized study with or without synthetic degradable augmentation device to support autograft in ACL reconstruction, no significant difference in clinical outcomes in short, intermediate and long term prospective was found in between the two groups i.e. one group with the use of poly (urethane urea) augmentation device and other without it (11).

Figure 6: Arthroscopic picture of ruptured LARS stump with visible particulate debris of the LARS visible on the background of PCL

Figure 6: Arthroscopic picture of ruptured LARS stump with visible particulate debris of the LARS visible on the background of PCL

Future Prospects
Development of ideal synthetic scaffold for the ACL reconstruction is a difficult task to achieve. Efforts are in place to create a synthetic substitute which can provide immediate functional stability and which can degrade at a rate similar to that of the tissue ingrowth. With advancements in tissue engineering, several polymers with a variety of different cell types have been developed for the scaffolds. Since the Fibroblast added collagen scaffolds had problems of immunogenicity and variable physical properties, biodegradable polymers such as Polyglycolic acid scaffolds have been developed and have been tested on animal models. Several studies using bone marrow stromal cells for formation of fibroblasts and smooth muscle cells with slow degrading properties of the scaffolds have been done (16).
With constant improvements in the tissue engineering techniques, future seems to be bright for synthetic ligamentous substitutes but for now, we are yet to supersede the biological grafts for the ACL reconstruction.

References

1. Alberto Venturo, Claudio Legnani, Clara Terzaghi, Enrico Borgo, Walter Albisetti “Revision surgery after failed ACL reconstruction with artificial ligament: Clinical, Histological and Radiographic Evaluation’. Eur Journal Orthop Surgery Traumatol 2014 24:93-98.
2. Alberto Venturo, Claudio Legnani, Clara Terzaghi, Enrico Borgo, Walter Albisetti “Synthetic graft for anterior cruciate ligament rupture 19 year outcome study” The Knee 17 (2010) 108–113.
3. Caroline Hildebrandt, Lisa Muller, Barbara Zisch, Reinhard Huber, Christian Flink, Christian Raschner “ Functional Assessment for decision making regarding return to sports following ACL reconstruction Part 1: development of new test battery. Knee Surg Sports Traumatol Arthrosc 2015 23: 1273-1281.
4. Cerulli, G. et al. (2007). ACL reconstruction using artificial ligaments: Five years follow-up. S.I.O.T, 33 (3suppl. 1), pp. 8238-8242.
5. Constantine M. Glezos, Alison Waller, Henry E. Bourke, Lucy J. Salmon and Leo A. Pinczewski “Disabling Synovitis Associated With LARS Artificial Ligament Use in Anterior Cruciate Ligament Reconstruction: A Case Report” Am J Sports Med 2012 40: 1167.
6. Fan, Q. et al. (2008) Comparison between four-strand semitendinosus tendon autograft and ligament advanced reinforcement system for anterior cruciate ligament reconstruction by arthroscopy. Chinese Journal of Reparative and Reconstructive Surgery 2008 June (6): 676-9 2008.
7. Huang Jian-ming et al (2010) cruciate ligament reconstruction using LARS artificial ligament under arthroscopy: 81 cases report. Chinese Medical Journal, 2010; 132(2):160-164.
8. Jan Riding, Lars Peterson “ Clinical experience with the Leeds-Keio Artificial Ligament in Anterior cruciate ligament reconstruction: A prospective 2 year follow-up study The American Journal of sports medicine Vole 23, no 3,1995.
9. Jiao Chen ,AquinoGU, Haiti Jiang, Winnie Zhang ,Xian Grong Yu “A comparison of acute and chronic anterior cruciate ligamentreconstruction using LARS artificial ligaments: a randomizedprospective study with a 5-year follow-up” Arch Northup Trauma Surge (2015) 135:95–102.
10. Kai Ago, M.D., Shay Chen, M.D., Ph.D., Lied Wang, M.D., Weiguo Zhang, M.D.,Yifan Kang, M.D., Qirong Dong, M.D., Haibin Zhou, M.D., and Linan Li, M.D. “Anterior Cruciate Ligament Reconstruction with LARS ArtificialLigament: A Multicenter Study With 3- to 5-Year Follow-up” Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 4 (April), 2010: pp 515-523.
11. Lars Peterson, Ulf Eklund, Bjorn Engstorm, Magnus Forssblad “ Long term results of a randomized study on ACL reconstruction with or without a synthetic degradable augmentation device to support autograft” KSSTA 2014,22: 2109-2120.
12. Lavoie, P. et al. (2000). Patient satisfaction needs as related to knee stability and objective findings after ACL reconstruction using LARS artificial ligament. The Knee, 7, pp. 157-163.
13. Marie-France Guidoin, Yves Marois, Jaques Bejui, Nicolas Poddevin, Robert Guidoin,et al. “ Analysis of retrieved polymer fibers based replacement” Biomaterials 21(2000), 2461-2474.
14. Meinolf Goertzen, M.D. PhD “Donor tissue choices in ACL revision” Sports Medicine and Arthroscopy review 5: 128-135,1997.
15. Papadopoulos, G. et al. (2005). Long – Term Results In The Treatment Of Acl Ruptures Using The LARS – Artificial Ligament. A.L.S. , Salzburg, June , 10-12 , 2005.
16. Saccomanni Bernardino “ ACL prosthesis- Any promise for future” Knee Surg Sports Traumatol Arthros 2010 18: 797-804.
17. Trieb, K. et al. (2004). In vivo and in vitro cellular ingrowth into a new generation of artificial ligament, Eur Surg Res. May-Jun;36(3):148-51.
18. Zhong-tang Liu & Xian-long Zhang & Yao Jiang & Bing-Fang Zeng “Four-strand hamstring tendon autograft versus LARSartificial ligament for anterior cruciateligament reconstruction” International Orthopaedics (SICOT) (2010) 34:45–49.
19. Zuzana Makotka, Ian Scarborough, Sarvana Kumar, Luke Parraton, et al. “Anterior cruciate ligament repairs with LARS: A systemic review. Sports Med Arthroscopy, Rehab, Therapy and technology 2010, 2: 29.

How to Cite this article:. Herald J, Kakatkar S. Synthetic Grafts in Anterior Cruciate Ligament Reconstruction. Asian Journal of Arthroscopy  Apr- June 2016;1(1):16-19 .

Dr. Jonathan Herald

Dr. Jonathan Herald

Dr. Sagar Kakatkar

Dr. Sagar Kakatkar

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BTB Vs Hamsrtings – Is There a Winner Yet ?

Sachin Tapasvi, Sachin Jain, Ashok Shyam

Volume 1 | Issue 1 | April – Jun 2016 | Page 11-15

Author: Sachin Tapasvi [1 ], Sachin Jain [2], Ashok Shyam [2],[3]

[1] Orthopaedic Specialty Clinic, Pune, Maharashtra. India
[2] Sancheti Institute for Orthopaedics & Rehabilitation, Pune, India
[3] Indian Orthopaedic Research Group, Thane, India

Address of Correspondence

Dr Sachin Tapasvi
Orthopaedic Specialty Clinic, Pune Maharashtra. India.
Email: stapasvi@gmail.com

Abstract

Bone patella tendon bone (BPTB) graft versus Hamstring (HT) Graft is still an issue that is debated. Both the graft have stood the test of time with high patient satisfaction however each have their own advantages and disadvantages. BPTB has advantages of good stability and bone to bone healing and disadvantage of anterior knee pain, numbness and quadriceps weakness. HT graft have advantage of less donor site morbidity, less extension deficit and disadvantage of having a slightly higher failure rate and hamstring weakness. Irrespective of these named advantages and disadvantages the patient reported outcomes are similar with both graft and difference in choice of graft is poorly understood. In this review we simply try to bring our reader up-to-date with the current literature on this controversy
Keywords: Bone patella tendon bone graft, hamstring graft, anterior cruciate ligament reconstruction.

Introduction

Anterior cruciate ligament (ACL) is required for static and dynamic stabiliser of the knee joint and purpose of ACL reconstruction is to stabilize and to resume function to maximum extent (1, 2). The ideal graft for use in anterior cruciate ligament reconstruction should have structural and biomechanical properties similar to those of the native ligament, permit secure fixation and rapid biologic incorporation, and limit donor site morbidity (3). Moreover, these properties should be present at the time of graft implantation and persist throughout the incorporation period too (3).
Graft options available are broadly grouped into autograft such as bone patellar bone tendon graft (BPTB), hamstring graft, Quadriceps graft and allograft such quadriceps, patellar, Achilles, hamstring, and anterior and posterior tibialis tendon graft (3-6). Allografts are useful to minimize donor site morbidity but are associated with increased cost, slower incorporation time, increased risk of disease transmission, and a higher failure rate (2). The synthetic grafts are yet to prove themselves and currently the most commonly used graft used for ACL reconstruction are autografts namely hamstring or BPTB graft. With BPTB graft comes with advantages of excellent initial fixation, biomechanical properties, durability, success at long- term follow-up with reduced pivot shift test (7, 8) and disadvantage of few reports suggesting donor site morbidity of patellofemoral osteoarthritis, scar formation with shortening of the patellar tendon, loss of terminal knee extension, and patellofemoral pain(2,9,10).
Semitendinosus and gracilis tendons (quadrupled hamstring tendon [HT]) have found to minimize donor site morbidity causing less anterior pain(8) with disadvantage of numbness of the anterior knee caused by injury to the infrapatellar branch of the saphenous nerve during graft harvest(2), longer rehabilitation period(3,10) and persisting pivot shift test at long term follow up(7). There are multiple extrinsic and intrinsic confounding variables(11) while studying the results of ACL reconstruction out of which isolated effects of a single extrinsic variable of graft choice is to be made.

Method of Review
There are several review articles published in literature including Pubmed, Medline and Cochrane database to compare of graft superiority (hamstring versus BPTB) in ACL reconstruction. We primarily did a pubmed search with Bone-Patellar Tendon-Bone Grafting as the Mesh major keyword. Two hundred and eighty five article were found and reviewed. There were 51 articles that either compared the two grafts or were meta-analysis of such articles. These 51 articles were then further reviewed to construct this review. There were 9 metanalysis among these 51 articles and 3 additional systematic reviews (1,4,7, 11-20). The Cochrane review of 2011 and a systematic summary of systematic reviews was also added to this list (21,22). Results of all these reviews were compiled and presented in Table 1. Other relevant articles were added to the review depending on the significance of their findings. It was noted that in most article the main areas of comparison between the two grafts were stability, donor site morbidity, complications, rehabilitation status, functional outcomes and revision rates due to graft. The present review is also arranged in this format.

Functional outcome
Functional outcome was measured in most of the articles using scores like Lysholm knee score, Tegner activity level, International Knee Documentation Committee (IKDC) scores etc. None of the studies found any difference in functional outcome measured (1,4,7,11-19,23-25) and hence both the grafts are equally effective in terms of restoring the functional ability of the patients. Pinczewski et al noted that Level 1 and 2 sports activities were significantly reduced from 73 to 85% (short term) to 45-57% (long term results) in both HT and BTPB groups (11). Recent review mentions that patients with HT graft are almost twice more likely to return to sports but patient with BPTB Graft are more likely to return or exceed the preoperative sports level (22). Other also indicate that patients with BPTB graft return to activity earlier than the HT graft (12). This may be probably because BPTB graft provide more static and rotational stability (1,15). Poolman et al (17) commented that modern techniques of HT graft will further increase stability and improve return to activity. However this is not confirmed by recent articles and possibly better controlled trials will be needed to eventually answer the question.

Donor site morbidity and complication after graft harvesting
When overall incidence of morbidity was reviewed, HT graft patient have lower incidence of morbidity (12,15). Anterior knee pain and kneeling pain was significant in BTPB group as compared with HT group(1–3,11,23). Anterior knee pain is related to the secondary chondromalacia patella which happens after ACL reconstruction regardless of graft type but it is noted that it can be five times greater in BPTB group versus HT group(2). There was a significant extension loss of >5 degrees in BPTB group versus HT group(1). It is noted that there was a concentric and eccentric reduction in Quadriceps power which was related to poor satisfaction rates (23). The Cochrane review in 2011 noted that BPTB Graft resulted in loss of knee extension range and strength while HT graft showed trend toward loss of flexion range and strength (21). There was a slight risk of patellar fracture which was mainly related to the errors in the surgical technique or use of unnecessary deeper saw cuts or osteotomes(23). Other donor site problems noted are patellar tendinitis, rupture of patellar tendon, increased joint stiffness, late chondromalacia and injury to infrapatellar branch of saphenous nerve(2,3,23). Reduced ultimate range of motion may be related to the rigid construct used in fixing BPTB graft (2). Other disadvantage of hamstring graft are injury to the superficial branch saphenous nerve and weakness of the hamstring muscles after operation (23, 24).

Stability
Stability has shown varied results in different studies and possible is a function of surgical technique and rehabilitation [Table 1].

Table 1: Comparative analysis of meta-analysis comparing BPTB and HT autograft

Table 1: Comparative analysis of meta-analysis comparing BPTB and HT autograft

Stability was assessed by Lachman test, pivot shift test and KT -1000 arthrometer in most series. Some authors reported no significant difference between either HT or BPTB group at long term follow up (11, 2). However, in mid-term follow up the side-to-side instrumented laxity (>2 mm) was greater in HT group as compared to BPTB group (7). BTPB is also found to be more rotationally stable with respect to pivot shift test (1).
Stability in case of HT graft was based on the number of strands used during surgery when compared with BPTB graft (1). When a 2 strand HT graft was used a statistical difference was noted in case of KT – 1000 and pivot shift test in favour of BPTB graft whereas Lachman test was not significant in both groups. If a 4 strand HT graft with a suspensory fixation like endobutton was used then the statistical difference was not significant in both the groups and had near normal Lachman, pivot shift tests and KT – 1000 testing(1,10,26–28). There is a slightly higher degrees of laxity noted in quadrupled hamstring graft as compared with BPTB graft especially in females in long term studies(2,20). Cochrane review noted that BPTB reconstructions are more likely to result in statically stable knees but they are also associated with more anterior knee problems. However there is insufficient evidence to predict superiority of one graft over other in long results in respect to functional outcome(21). In a study, comparing double bundle reconstruction with HT graft and anatomical BPTB graft positioning equal results are found with respect to stability and laxity throughout the range of motion(29). The recent summary of meta-analysis however concluded that BPTB graft are more stable as per the current available evidence (22)

Rehabilitation
It is noted that integration of bone to bone healing with direct insertion is much faster in BPTB graft as compared to bone to soft tissue healing by means of indirect insertions with sharpey’s fibres in case of HT graft(23). So with rapid incorporation with graft healing to bone, there is potential for accelerated rehabilitation in BPTB graft and may be earlier return to play sports activities(3,23). It usually takes 6 weeks for a BPTB to incorporate in the host bone whereas around 8 to 12 weeks with HT graft(3). Short term studies showed mixed results of quadriceps strength with HT graft harvest whereas long term studies shows no difference in quadriceps strength with BPTB versus HT graft(8,20). Evaluation of functional capacities: power, strength, velocity and dynamic stability of knee extensor and flexor muscles after ACL reconstruction showed that use of a BPTB autograft achieved better muscular and functional capacities than the HT autograft(6). During rehabilitation with hamstring graft requires less supervision with less risk of complications such as the infrapatellar contracture syndrome, arthrofibrosis or persisting pain(23).

Osteoarthritis Risk
Radiographic assessment showed no significant differences between the two groups in terms of osteoarthritic findings classified according to the Fairbank and Ahlback rating systems in short term studies(26) and mild osteoarthritic changes in BPTB group at mid and long term follow up as compared with HT group(11). Overall, osteoarthritis was identified in 16% (BPTB 19%; ST 13%.) according to the Ahlback rating system and 68% (BPTB 67%; ST 70%; ) according to the Fairbank rating system(26). Xie et al found the risk of development of OA was around 61% greater in BPTB graft as compared to HT Graft (14). Early osteoarthritic changes are also function of primary injury and associated injuries like meniscal injuries and cartilage injuries (30). However late onset osteoarthritis will require much longer follow up and none of the current studies offer much insight into development of OA in long term (22)

Failure rates
There is no obvious difference in the occurrence of ligament failure between HT group and the BPTB group after ACL reconstruction in long term studies but a few studies demonstrate reduced failure rates with BPTB graft(1). Hamstring graft harvest weakens the knee flexor strength leading to slightly higher degrees of graft failure (2,4). However, these studies had a selection bias which had included studies using double or triple strand graft which gave slightly higher failure rates. Long term studies have shown to have equal success rates with quadrupled hamstring graft or BPTB graft(8,20). Moreover, it is also noted that the fixation modality and anatomical placement of ACL is responsible for low failure rates(20) It has been noted that contralateral ACL tear with BPTB graft is statistically significant as compared to HT graft in short term studies whereas in long term studies there is no increase in contralateral ACL tear(8). A risk factor for contralateral ACL rupture was a return to sports that involved sidestepping, pivoting, and jumping (8). In a registry study based on 45,998 primary ACL Reconstructions in Scandinavi it was found that patients receiving patellar tendon autografts have a statistically significantly lower risk of revision compared with patients receiving hamstring autografts(5).

Conclusions

As per current reviews and evidence, both graft achieve good functional outcome in patients. BPTB graft may offer a more stable knee and possible achieve rapid and effective return to preinjury activity level. HT graft have less donor site morbidity and with new effective fixation modalities, they may also match the stability achieved by BPTB grafts. However there is insufficient evidence to clearly establish a winner and probably more robust future studies will be better able to define the role of each of these autograft options

References

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2. Shelton WR, Fagan BC. Autografts Commonly Used in Anterior Cruciate Ligament. J Am Acad Orthop Surg. 2011;19(5):259–64.
3. West R V, Harner CD. Graft Selection in Anterior Cruciate Ligament Reconstruction. J Am Acad Orthop Surg. 2005;13(3):197–207.
4. Reinhardt KR, Hetsroni I. Graft Selection for Anterior Cruciate Ligament Reconstruction : A Level I Systematic Review Comparing Failure Rates and Functional Outcomes. Orthop Clin NA [Internet]. Elsevier Ltd; 2010;41(2):249–62.
5. Gifstad T, Foss OA, Engebretsen L, Lind M, Forssblad M, Albrektsen G. Lower Risk of Revision With Patellar Tendon Autografts Compared With Hamstring Autografts A Registry Study Based on 45 , 998 Primary ACL Reconstructions in Scandinavia. Am J Sports Med. 2014;42(10):2319–28.
6. Baur C, Mathieu N, Delamorclaz S, Hilfiker R, Blatter S, Siegrist O, et al. Anterior cruciate ligament reconstruction : Hamstring Tendon autograft versus Bone Patellar Tendon Bone autograft : what about muscular and functional capacities ? Schweizerische Zeitschrift für Sport und Sport. 2015;63(2):18–22.
7. Biau DJ, Katsahian S, Kartus J, Harilainen A, Feller JA, Sajovic M, et al. Patellar Tendon Versus Hamstring Tendon Autografts for Reconstructing the Anterior Cruciate Ligament : A Meta-Analysis Based on Individual Patient Data. Am J Sports Med. 2009;37(12):2470–8.
8. Macaulay AA, Perfetti DC, Levine WN, Macaulay AA, Perfetti DC, Levine WN. Anterior Cruciate Ligament Graft Choices. Sport Heal A Multidiscip Approach. 2012;4(1).
9. Dahm DL. A Meta-analysis of Patellar Tendon Autograft Versus Patellar Tendon Allograft in Anterior Cruciate Ligament Reconstruction. Arthrosc J Arthrosc Relat Surg. 2008;24(3):292–8.
10. Siebold R, Webster ÆKE, Feller ÆJA, Sutherland AG, Elliott ÆJ. Anterior cruciate ligament reconstruction in females : a comparison of hamstring tendon and patellar tendon autografts. Knee. 2006;14:1070–6.
11. Pinczewski LA, Lyman J, Salmon LJ, Russell VJ, Roe J, Linklater J. A 10-Year Comparison of Anterior Cruciate Ligament Reconstructions With Hamstring Tendon and Patellar Tendon Autograft A Controlled , Prospective Trial. Am J Sports Med. 2007;10(10):1–11.
12. Xie X, Liu X, Chen Z, Yu Y, Peng S, Li Q. A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction. Knee. 2015 Mar;22(2):100-10
13: Yao LW, Wang Q, Zhang L, Zhang C, Zhang B, Zhang YJ, Feng SQ. Patellar tendon autograft versus patellar tendon allograft in anterior cruciate ligament reconstruction: a systematic review and meta-analysis. Eur J Orthop Surg Traumatol. 2015 Feb;25(2):355-65.
14. Xie X, Xiao Z, Li Q, Zhu B, Chen J, Chen H, Yang F, Chen Y, Lai Q, Liu X. Increased incidence of osteoarthritis of knee joint after ACL reconstruction with bone-patellar tendon-bone autografts than hamstring autografts: a meta-analysis of 1,443 patients at a minimum of 5 years. Eur J Orthop Surg Traumatol. 2015 Jan;25(1):149-59.
15. Li S, Chen Y, Lin Z, Cui W, Zhao J, Su W. A systematic review of randomized controlled clinical trials comparing hamstring autografts versus bone-patellar tendon-bone autografts for the reconstruction of the anterior cruciate ligament. Arch Orthop Trauma Surg. 2012 Sep;132(9):1287-97
16. Biau DJ, Katsahian S, Nizard R. Hamstring tendon autograft better than bone-patellar tendon-bone autograft in ACL reconstruction – a cumulative meta-analysis and clinically relevant sensitivity analysis applied to a previously published analysis. Acta Orthop. 2007 Oct;78(5):705-7
17. Poolman RW, Farrokhyar F, Bhandari M. Hamstring tendon autograft better than bone patellar-tendon bone autograft in ACL reconstruction: a cumulative meta-analysis and clinically relevant sensitivity analysis applied to a previously published analysis. Acta Orthop. 2007 Jun;78(3):350-4.
18. Biau DJ, Tournoux C, Katsahian S, Schranz PJ, Nizard RS. Bone-patellar tendon-bone autografts versus hamstring autografts for reconstruction of anterior cruciate ligament: meta-analysis. BMJ. 2006 Apr 29;332(7548):995-1001.
19. Harilainen A, Linko E, Sandelin J. Randomized prospective study of ACL reconstruction with interference screw fixation in patellar tendon autografts versus femoral metal plate suspension and tibial post fixation in hamstring tendon autografts: 5-year clinical and radiological follow-up results. Knee Surg Sports Traumatol Arthrosc. 2006 Jun;14(6):517-28.
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22. Anderson MJ, Browning WM 3rd, Urband CE, Kluczynski MA, Bisson LJ. A Systematic Summary of Systematic Reviews on the Topic of the Anterior Cruciate Ligament. Orthop J Sports Med. 2016 Mar 15;4(3):2325967116634074.
23. Bartlett RJ, Clatworthy MG, Nguyen TN V. Review article GRAFT SELECTION IN RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT. J Bone Joint Surg Br. 2001;83(July):625–34.
24. Matjaz S, Andrej S, Radko K, Mojca D. The effect of graft choice on functional outcome in anterior cruciate ligament reconstruction. Int Orthop. 2008;32:473–8.
25. Martin NJ, Shishir SM, Kanagasabai R, Najimudeen S, Gnanadoss JJ. “ Quadruple hamstring tendon graft versus Bone-Patellar- Tendon-Graft for arthroscopic Anterior Cruciate Ligament reconstruction- comparison study with follow up of 2 years .” IOSR J Dent Med Sci. 2014;13(11):6–13.

26. Ahlde M. Knee laxity measurements after anterior cruciate ligament reconstruction , using either bone – patellar – tendon – bone or hamstring tendon autografts , with special emphasis on comparison over time. Knee. 2009;17:1117–24.
27. Svensson M, Ejerhed L, Kartus T. A prospective comparison of bone-patellar tendon-bone and hamstring grafts for anterior cruciate ligament reconstruction in female patients. Knee Surgery, Sport Traumatol Arthrosc. 2006;14:278–86.
28. Gauti L, Ninni S, Lars E, Jon K, Juri K. A prospective comparison of bone-patellar tendon-bone and hamstring tendon grafts for anterior cruciate ligament reconstruction in male patients. Knee. 2007;15:115–25.
29. Ishibashi Y, Tsuda E, Fukuda A, Tsukada H. Intraoperative Biomechanical Evaluation of Anatomic Anterior Cruciate Ligament Reconstruction Using a Navigation System Comparison of Hamstring Tendon and Bone – Patellar Tendon – Bone Graft. Am J Sports Med. 2008;36(10):1903–12.
30. Andersson D, Samuelsson K, Karlsson J. Treatment of anterior cruciate ligament injuries with special reference to surgical technique and rehabilitation: an assessment of randomized controlled trials. Arthroscopy. 2009 Jun;25(6):653-85

How to Cite this article:. Tapasvi S, Jain S, Shyam AK. BTB Vs Hamsrtings – Is There a Winner Yet ?. Asian Journal of Arthroscopy  Apr-June 2016;1(1):11-15 .

 

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ACL Treatment in 2016 – Controversy and Consensus

Renato Andrade, Hélder Pereira, João Espregueira-Mendes

Asian Journal of Arthroscopy | Volume 1 | Issue 1 | April – Jun 2016 | Page 3-10

Author: Renato Andrade[1],[2],[3], Hélder Pereira[3],[4],[5],[6],[7], João Espregueira-Mendes[2],[3],[5],[6],[8]

[1] Faculty of Sports, University of Porto, Porto, Portugal
[2] Clínica do Dragão, Espregueira-Mendes Sports Centre – FIFA Medical Centre of Excellence, Porto, Portugal
[3] Dom Henrique Research Centre, Porto, Portugal.
[4] Orthopedic Department, Centro Hospitalar Póvoa de Varzim – Vila do Conde, Póvoa de Varzim, Portugal
[5] 3B’s Research Group – Biomaterials, Biodegradables and Biomimetics, Univ. Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Avepark – Parque de Ciência e Tecnologia, Zona Industrial da Gandra, 4805-017 Guimarães, Portugal;
[6] ICVS/3B’s–PT Government Associate Laboratory, Braga/Guimarães, Portugal
[7] Ripoll y De Prado Sports Clinic FIFA Medical Centre of Excellence, Murcia-Madrid, Spain
[8] Orthopaedics Department of Minho University, Minho, Portugal

Address of Correspondence

Dr João Espregueira-Mendes
Via Futebol Clube do Porto – F. C. Porto Stadium, Porto, Portugal
Email: espregueira@dhresearchcentre.com

Abstract

The incidence of anterior cruciate ligament (ACL) injuries has been increasing in the last few decades and, along with it, the number of ACL reconstruction failures has also been growing. To overcome the surgical complications and failures, several developments have been made in regard to the ACL treatment. Nowadays, the ACL reconstruction has become more anatomic and individualized, aiming for the closest replication of the native ACL anatomy and biomechanics. As the knowledge regarding the ACL anatomy and biomechanics moves forward, novel surgical techniques and fixation devices have been developed to keep up the patient’s demands and further prevent the early onset of osteoarthritis. Nonetheless, a considerable number of controversies are still under debate. This review will outline the current concepts of ACL treatment, focusing its consensus and controversies.
Key-words: ACL; Anterior cruciate ligament; Reconstruction; Treatment; Current concepts

Introduction

Anterior cruciate ligament (ACL) ruptures are a common injury worldwide, with an estimated incidence of 80,000 to more than 250,000 every year(1), affecting mostly the young athletes under 25 years old. Several risk factors seems to be predisposing the individuals to a higher risk of injury, such as, environmental (meteorological conditions, field surface and footwear), anatomical (Q angle, knee valgus, foot pronation, body mass index, bone morphology – e.g. narrow intercondylar notch, and steeper tibial slopes) and neuromuscular risk factors (altered movement patterns and muscle activation patterns and inadequate muscle stiffness)(1-3). In addition, it was suggested that greater anteroposterior (AP) lengths and height of the lateral femoral condyle in relation to a smaller AP diameter of the lateral tibial plateau can predispose the higher risk of ACL injury (4). If these injuries are left without proper treatment, it will result in increased knee laxity and instability, decreased levels of physical and sporting activities and, eventually lead to degenerative changes of the knee joint(5-8). In this sense, the ACL reconstruction aims to restore the knee stability and function, the normal knee kinematics and prevent the early onset of osteoarthritis.
Traditionally, ACL ruptures were surgically treated through non-anatomic ACL reconstructions, with the graft in the isometric position and out of the femoral footprint. However, the non-anatomic ACL reconstruction often resulted residual rotational laxity(9, 10). Nowadays, the focus has shifted towards the anatomic reconstruction highlighting the importance of the correct tunnel position in the native ACL footprint. This concept relies upon the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites, taking into account the individual anatomical, morphological characteristics and biomechanical demands of each patient(11). In this sense, Karlsson, Irrgang (12) identified four key principles: restoration of the native insertion site anatomy by placing the tunnels in the correct position; restoration of the two functional bundles (anteromedial and posterolateral; Figure 1); provide the appropriate tension; individualize the surgical procedure for each patient in terms of graft type, tunnel size and graft diameter.
In this review, it will be presented an overview of the current concepts and state-of-art of ACL treatment, focusing the consensus and controversies related to this topic.

fig1

Figure 1: Arthroscopic view of intact native ACL, where it is displayed the two functional bundles, anteromedial (AM) and posterolateral (PL).

Diagnostic procedures and laxity measurement
A comprehensive medical history, musculoskeletal physical examination and imaging procedures play a crucial role in the diagnosis of an ACL injury(13). The taking of medical history should be comprehensive enough to provide information regarding the time and mechanism of injury, rupture pattern and the patient’s activity level(14, 15). The physical examination should comprise valid and reproducible examination tests in order to accurately lead the diagnostic process including the Lachman, pivot-shift and anterior drawer tests. In this sense, the Lachman test is the most sensitive test (87%) and the pivot-shift the most specific (98%)(16). The magnetic resonance imaging (MRI) has been reported to be useful in the ACL injury diagnostics, often capable of identifying complete and partial ACL ruptures (17). In addition, it is helpful in identifying concomitant knee pathology such as other ligament, meniscal, or articular cartilage injury(13). Nonetheless, the abovementioned procedures fail to provide an objective quantitative measure of the ACL laxity. To overcome this issue, several mechanical testing devices have been used in order to measure tibiofemoral AP translation and rotational laxity (18). However, the reliability and diagnostic accuracy of some of them, such as, the KT-1000™, has been questioned(19, 20). Therefore, the ideal tool should be able to assess both “anatomy” and “function” on the same examination. In this sense, the Porto-Knee Testing Device (PKTD) is a safe and MRI-compatible knee laxity testing device, capable of measuring the AP tibial translation and tibial internal and external rotation (Figure 2)(21).

Figure 2: Demonstrative image of PKTD assessment. Left arrow indicates the tibial AP translation induced by the pressure applied in the posterior proximal calf region through the actuators pressurizing. Right arrow indicates the tibial internal rotation through pressure applied at the footplate axis.

Figure 2: Demonstrative image of PKTD assessment. Left arrow indicates the tibial AP translation induced by the pressure applied in the posterior proximal calf region through the actuators pressurizing. Right arrow indicates the tibial internal rotation through pressure applied at the footplate axis.

Case 1
A twenty-year-old male athlete presented to the sports clinic 4 months following a motorcycle fall. There was no knee effusion evident, however the patient reported residual pain on his right knee. During the physical examination, the patient showed positive Lachman (+/++) and lateral pivot-shift (+) tests, suggesting an increased ACL laxity. Given the medical history and physical examination, the patient was directed for conventional and PKTD MRI examination to assess the presence of further lesions.
The conventional MRI showed bony contusions on the lateral femoral condyle and lateral tibial plateau. In addition, there was evidence of increased signal in one of the bundles, suggesting an ACL partial rupture (Figure 3A). During the PKTD MRI examination, there was tibial PA subluxation (Figure 3B), which increased by 7 mm when submitted to PA stress and internal rotation of the foot (Figure 3C). The conventional MRI examination showed evidence of potential partial rupture, which was confirmed by the PKTD examination, revealing a non-functional ACL.

Figure 3: Knee conventional and PKTD MRI examination, with sagittal images of the lateral femoral condyle and lateral tibial plateau of the right knee. A) Knee conventional MRI examination; B) PKTD without stress (13 mm); C) PKTD with PA stress and internal rotation of the foot (20 mm).

Figure 3: Knee conventional and PKTD MRI examination, with sagittal images of the lateral femoral condyle and lateral tibial plateau of the right knee. A) Knee conventional MRI examination; B) PKTD without stress (13 mm); C) PKTD with PA stress and internal rotation of the foot (20 mm).

In partial ACL ruptures, there is often loss of the functional integrity of the remaining ligamentous fibers, resulting in knee instability and symptomatology of impaired knee function. In cases where the remaining fibers retain their functional capacity, an augmentation procedure will be more suitable

Surgical indications
The decision upon the surgical treatment must be made taking into account the patient’s age, demands of their sports or physical activities, expectation and presence of concomitant injuries(22). In this sense, the indications for ACL reconstruction are young and active adults (18-35 years old) that have sustained an acute ACL injury and signs of instability(13). At this point, concomitant injuries (such as, meniscus, ligamentous or cartilaginous injuries) must be addressed in combination with the ACL reconstruction in order to improve the surgical outcomes(13, 23).

Time-to-surgery
As soon as the decision to operate is made, the surgeon must consider the ideal time to perform the reconstruction. Several prognosis variables (pre-operative range of motion, swelling and quadriceps strength) should be analyzed before proceeding to surgery as these will affect the ACL reconstruction outcome and success(24, 25). Moreover, delaying tACL reconstruction will increase the possibility for the development of other concomitant injuries, such as, cartilage lesions or meniscal lesions(26, 27). In this sense, it has been recommended to perform the ACL reconstruction as soon as pre-operative problems are resolved (no pain, no swelling and at least 90º of flexion)(28) and within 5 months from injury to preserve from further meniscus and/or cartilage damage(13, 29).
ACL reconstruction techniques
The technique for the ACL reconstruction should be taolored to the needs of the patient-tailored and follow the anatomic reconstruction concept. A consensus on which is the best approach, either single-bundle or double-bundle reconstructions, has not been reached however both techniques achieve similar results(13, 30, 31). Thus, the choice of one of these techniques should be based upon different criteria, mostly related to the visualization of the insertion sites and length of tibial and femoral insertion sites (cut-off at 14 mm), which was proposed in ACL reconstruction flowchart by Lesniak et al (11)
Partial ACL ruptures are known to be multifactorial and a consensus on its definition has not been determined (32). In cases which a single bundle (anteromedial or posterolateral) is ruptured or non-functional and the other bundle is well-preserved, a single-bundle augmentation surgery may be deliberated (17, 33, 34). The augmentation technique for the remnant bundle may provide greater vascularization and proprioception, optimize the accuracy of the reconstruction and enhance greater stability and clinical and functional outcomes (33-35). In cases of partial ACL ruptures, the PKTD can be useful in evaluating the individual biomechanical contribution of the remaining bundle functionality (17).

Tunnel placement
Nowadays the anatomic position of the graft within the native footprint has gain increasing popularity and, therefore, the proper tunnel placement plays a crucial role. A 3-portal approach comprising the standard anterolateral and central medial portals and, in addition, an accessory anteromedial portal (superior to the medial joint line approximately 2 cm medial to the medial border of the patellar tendon) has been suggested(36).
Performing the ACL reconstruction with the 3-portal approach will allow the surgeon to visualize the entire ACL and its femoral and tibial insertions(12). In this sense, several landmarks to identify the ACL femoral native footprints have been suggested including lateral intercondylar ridge (most anterior border), lateral bifurcate ridge (division into anteromedial and posterolateral bundles) and the posterior cartilage border (37). If these landmarks are absent, the ACL femoral footprint is known to be at the lower 30-35% of the notch wall with the knee at 90º of flexion. The ACL tibial native footprint can be found through the tibial spines, anterior and posterior horns of the lateral meniscus and posterior cruciate ligament insertion site(12).
Since graft malposition has been reported as one of the most common technical errors(38), several femoral tunnel drilling techniques have been developed, such as, the anteromedial portal, the outside-in and outside-in retrograde drilling techniques(39). It has been shown that transtibial technique yields more subjectively poorly positioned tunnels than the two-incision and medial portal techniques(40). Nevertheless, excellent outcomes have also been reported with a modified transtibial technique(41). In this sense, all the four techniques have shown different advantages and disadvantages, and a clear consensus on which is the best technique for creating the femoral ACL socket has not been reached so far(39). Our recommendations, based on daily practice, is to use the anteromedial and the possibility to add an accessory anteromedial portal.
The accuracy of the tunnel position (tunnel angle and implant position and length) can be further evaluated through radiography, MRI or three-dimensional computed tomography (CT). In this sense, the three-dimensional CT (Figure 4) is considered gold-standard since its measurements provide the highest reliability (42, 43).

Figure 4: Three-dimensional CT image demonstrating the tibial (image on the left) and femoral (image on the right) tunnel placement in single-bundle ACL reconstruction.

Figure 4: Three-dimensional CT image demonstrating the tibial (image on the left) and femoral (image on the right) tunnel placement in single-bundle ACL reconstruction.

Graft choice
The choice of the correct graft for the ACL reconstruction plays an essential role in the success of the surgery. Regarding the graft choice there is “no one-size-fits-all” concept and, therefore, the decision of the graft should be based on the patient age, size and gender, physical demands, associated injuries, degree of laxity, patient’s anatomy, patient’s choice and expectations and, ultimately, the surgeon preferences, experiences and beliefs. Moreover, the chosen graft should replicate the anatomical and biomechanical properties of the native ligament, guarantee a safe and longstanding fixation, and provide rapid biological integration and low donor-site morbidity(44). In this sense, three different types of graft can be considered including the autografts, allografts and synthetic grafts.
Autografts usually include the bone-patellar tendon-bone (BPTB), the hamstrings tendons (HS) and the quadriceps tendon (QT). The autografts have the advantage of being immediately available and biological healing potential, without risk of additional disease transmission and without additional costs(45). Strong evidence has been shown towards the use of BPTB (Figure 5) or HS grafts once the overall reported follow-up measured outcomes are similar(13). The central QT graft is not recommended for primary ACL reconstruction but often considered for revision cases(45). Recent studies show promising results and low donor-site morbidity levels(46). When comparing the BPTB and HS autografts, the most recent systematic reviews show no significant differences regarding the return to activity, clinical, functional and subjective outcomes (47-50). Nonetheless, the BPBT seems to cause more morbidity (anterior knee and kneeling pain) but increased knee stability, with higher levels of activity(47-50). In addition, other advantages and disadvantages have been pointed out to the different available autografts(15, 22, 44).
The allografts have advantage over the autografts regarding donor-site harvesting morbidity, less operative time and have no limits regarding the number, size and shape(45). Nevertheless, they can result in disease transmission (low risk), higher costs, longer healing time frame and increased risk of failure (specially in young patients and irradiated grafts)(22, 51). The tibialis posterior/anterior, peroneous longus and Achilles tendon allografts are the most commonly used, however the patellar tendon and HS are also easily available(45). Indications for allograft usually included athletes that might be affected by the harvesting symptomatic and functional deficits, ACL revision surgeries and complex multiligament reconstructions(52). When compared to autografts, the current scientific evidence show no significant differences regarding the re-rupture rate, clinical, functional and subjective outcomes(53, 54).
The synthetic grafts are often seen as intra-articular braces and are now into their third generation with several synthetic devices under development. The Ligament Advanced Reinforcement System (LARS) device has shown some favorable outcome in selected patients(55). Their role in ACL reconstruction still remains to be defined(55), however usual indications are rare including healing augmentation in symptomatic and active individuals (>40 years) with an acute ACL injury requiring a fast post-operative recovery(44, 56).

Figure 5: BPBT autograft preparation to single bundle ACL reconstruction. By twisting the autograft 90 degrees, it is possible to approximate the autograft to the native ACL anatomy and biomechanics, resembling the ACL double-bundle anatomy concept (AM, anteromedial bundle; PL, posterolateral bundle).

Figure 5: BPBT autograft preparation to single bundle ACL reconstruction. By twisting the autograft 90 degrees, it is possible to approximate the autograft to the native ACL anatomy and biomechanics, resembling the ACL double-bundle anatomy concept (AM, anteromedial bundle; PL, posterolateral bundle).

Graft fixation
Over the last decade, we have been witnessing significant developments concerning the bone plug and soft tissue fixation devices. These fixation devices can be further divided into aperture fixation and suspensory fixation(57). The fixation device for the ACL reconstruction graft should be secure and maintain the optimal tension until full integration of the graft has occurred. In addition, it should provide strength enough to prevent graft failure, stiffness enough to restore stability and provide biomechanical properties to the graft that replicate the native ACL(15, 45). The strength provided should be enough to allow immediate range of movement and weight bearing exercises and permit an early return to sports(57).
The most common bone plug fixation devices for the tibial and femoral fixation are the metal or bio-interferences screws (Figure 6)(15, 45). The bioabsorbable screws have the advantage of faster degradation, promoting the bone ingrowth, incorporation of the graft into the surround tissue, lower need for implant removal and reduced MRI interference(45). Nevertheless, caution should be taken upon the the possible migration of the bioabsorbable screws(58). When considering bioabsorbable against metallic interference screws, both provide similar clinical and functional outcomes, however the bioabsorbable interference screws are more associated with prolonged knee effusion, increased femoral tunnel widening, and increased screw breakage(59).

When considering soft tissue fixation devices, the suspensory devices are more commonly used for the femoral tunnel fixation and the interference screws for the tibial side(15). In regard to the suspensory devices, they have been widely used for graft fixation, providing reduced stiffness than interference screws and higher load to failure. Moreover, it avoids disruption of the insertion site (Figure 7)(15). However, there have been reports of tunnel enlargement(60). When comparing the interference screws with suspensory fixation, corticocancellous fixation and cross biodegradable pins for femoral soft tissue fixation, it was shown that interference screws resulted in decreased risk of surgical failure but no differences were found when postoperative functional outcomes are compared(61). Mechanical properties of cortical suspension and screws fixation for the soft tissue femoral and tibial side are already available in the literature(62, 63).

Biological enhancement of the ACL primary repair
During the past decade, several bio-enhancement tissue engineering regenerative medicine (TERM) approaches have been reported for the primary reconstruction of ACL ruptures, including cell-based therapy, artificial ligament systems, platelet-rich plasma (PRP), growth factors and cytokines, calcium phosphate (hybridized tendon), biodegradable biomaterials and mechanical stimulation (low-intensity pulsed ultrasound). These TERM approaches have been showing promising results as they can work in synergy with the ACL reconstruction and have the potential advantages of enhancing better ligamentization and faster recovery(64). The addition of PRP to ACL treatment has shown promising results in accelerating the graft maturation. However, there is no clear evidence of the benefits of PRP on tunnel and tendon-to-bone healing and enhancing better clinical and functional outcomes(65, 66).

Rehabilitation and prevention
The rehabilitation plays an important role in the success of the ACL reconstruction. In this sense, current trends are towards individualized, patient-tailored, progression-based accelerated (or non-accelerated) rehabilitation protocols in order to achieve better clinical and functional outcomes, as well as, returning faster to the competition. Along this line, the patient adherence and compliance to the rehabilitation protocol are crucial. Moreover, the timeframe of the tissue healing must be respected(67, 68). In addition, these protocols must be adapted to the graft type and concomitant surgical procedures (such as, meniscal or cartilage repair)(69). They include immediately knee full extension, immediate partial weight bearing (in exception when associated lesions are present and a concurrent surgical procedure was performed, such as, meniscus or cartilage repair). Full description of criteria progression-based rehabilitation protocols have already been published in the scientific literature(69, 70).
Prevention programs are the keystone for reducing the rate of non-contact ACL injuries and should focus in adjusting the neuromuscular and biomechanical modifiable risk factors. These often include sportive technique modification, neuromuscular training, stretching, plyometric training, balancing the hamstring/quadriceps ratios, and trunk/core control training(71). A wide range of prevention programs have been developed, with good results being reported(13, 71, 72). In addition, a comprehensive follow-up of the patient’s neuromuscular and biomechanical potential deficits (such as, dynamic knee valgus and high abduction loads) after ACL reconstruction plays a critical role in preventing recurrence of the ACL injury (secondary prevention)(73).

Return to sports
Returning to pre injury level of sports is the main goal of every young athlete but still a controversial issue in the sports medicine community. The timing of returning to competition is multifactorial and therefore several preoperative (age, preoperative rehabilitation, full knee extension and neuromuscular control), intraoperative (graft choice) and postoperative factors (rehabilitation protocol and psychological factors) have been suggested to influence the return to play(74). Clearance to return to competition should be a multidisciplinary decision and take into account objective criteria instead of time frames(67). In this sense, several objective criteria have been proposed and the most important are: no pain or swelling; full active knee range of motion; isokinetic unilateral and bilateral balance and functional hop testing (side-to-side difference <15%); functional and static knee stability(67, 70). In a meta-analysis, comprising a total of 5770 patients (from 48 studies) and a mean follow-up of 41.5 months, 82% of the participants returned to some kind of sports participation, while only 63% returned to their pre-injury level and 44% to competitive sports(75).

Case 2
A 21-years-old amateur male football player presented to the sports clinic reporting symptoms of knee instability (give-away). During the medical history taking, the patient reported that he had 3 years ago an ACL rupture, which was reconstructed with a HS autograft on the 20th day from injury. The surgery and subsequent rehabilitation underwent without any complications and the football player returned to play at the 9th month. During the physical examination, there was present an increased tibial PA and rotation laxity, evidenced by the Lachman (+) and lateral pivot-shift (++) tests, specially when compared to the contralateral healthy knee. There was no knee effusion, stiffness or loss of range of motion. In light of these clinical findings, the patient was referred for MRI with PKTD examination to assess the autograft status and the presence of pathological laxity.
Although the football player underwent all the rehabilitation phases and had returned to competition without complications, three years after the ACL reconstruction he begin to feel symptomatology of instability. The MRI exam with the PKTD showed that he had significant residual laxity on his right knee, with side-to-side differences of 6 mm on the medial side and 10 mm on the lateral side (Figure 8).
Despite the several developments in the orthopaedic surgery, residual laxity after ACL reconstruction is still an issue to overcome. This residual laxity often results from permanent deformation of the graft tissue that precluded the restoration of the normal knee stability. This residual laxity may result from technical errors, such as, graft undertensioning, graft slippage or micromotion (due to improper tibial fixation), incomplete healing (integration of the graft), incorrect tunnel placement, inadequate graft fixation, missed associated laxities (specially, the posterolateral corner laxity) and divergent screws placed (>15º). In addition, traumatic re-rupture, aggressive rehabilitation or early return to play may also lead to residual laxity.

Conclusions

A great deal of focus from the orthopaedic and sports medicine communities has been on the ACL treatment. There is still an open debate in many features of the ACL injury management, while considerable developments have been made over the past few decades. In this review it is outlined and discussed the current consensus and controversies of the ACL treatment and the summary of the key points is presented below.
A complete and reliable diagnostic process should comprise a comprehensive medical history, musculoskeletal physical examination and imaging procedures (radiography and MRI). This can be complemented with laxity measurements with arthrometers (KT-1000) or better with MRI-compatible devices (PKTD).
Young and active adults with acute ACL injury and signs of instability are candidates for ACL reconstruction.
The surgery should be performed after the acute signs are resolved and within the first five months of injury.
Current trends of ACL reconstruction are towards the anatomic and individualized reconstruction.
In partial ACL ruptures, single-bundle augmentation surgery may be an option.
Femoral tunnel placement should be made through a tibial independent approach.
No consensus regarding the graft type (autograft vs. allograft) or autograft source (BPTB vs. HS).
No consensus concerning the graft fixation. For bone plugs fixation, metal or bio-screws are more commonly used. For soft tissue fixation, suspension devices for the femoral side and interference screws for the tibial side.
Although the promising results, the additional value of TERM approaches is not still well established in the literature.
The postoperative rehabilitation should be made through individualized, patient-tailored, progression-based accelerated (or non-accelerated) rehabilitation protocols.
Prevention programs are effective in reducing the rate of non-contact ACL injuries and a comprehensive follow-up of neuromuscular and biomechanical deficits is crucial for the secondary prevention.
The return to competition should be a multidisciplinary decision and be based in objective criteria.

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How to Cite this article:. Andrade R, Pereira H, Mendes JE. ACL Treatment in 2016 – Controversy and Consensus. Asian Journal of Arthroscopy  Apr- June 2016;1(1):3-10 .

Dr. Renato Andrade

Dr. Renato Andrade

Dr. Hélder Pereira

Dr. Hélder Pereira

Prof. Dr. João Espregueira-Mendes

Prof. Dr. João Espregueira-Mendes

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