Tag Archive for: anterior cruciate ligament

Meniscus Ramp Lesion

Bertrand Sonnery Cottet, Sanesh Tuteja, Nuno Camelo Barbosa, Mathieu Thaunat

Volume 1 | Issue 2 | Aug – Nov 2016 | Page 28-34.

Author: Bertrand Sonnery Cottet[1], Sanesh Tuteja[1], Nuno Camelo Barbosa[1], Mathieu Thaunat[1].

[1] Investigation performed at the Centre Orthopédique Santy, FIFA medical center of Excellence, Groupe Ramsay-Générale de Santé, Lyon, France

Address of Correspondence

Dr Bertrand Sonnery-Cottet
Centre Orthopédique Santy, 24 Avenue Paul Santy, Lyon, 69008, France
Email: sonnerycottet@aol.com.

Abstract

Ramp Lesions of the Medial Meniscus (MM) are associated with 9 to 17% of ACL Tears and are seldom recognized on preoperative magnetic resonance imaging (MRI) scans. They also often remain undiagnosed when viewing from the standard anterior compartment arthroscopic portals. Improved visualization is the key to achieving good meniscal repair results as it improves diagnosis of longitudinal tears in posterior horn MM, safeguards better debridement prior to repair and ensures good approximation of the torn ends under vision. A systematic posteromedial exploration allows discovery of and debridement of the hidden MM lesion and repair with a suture hook device is associated with low morbidity and must be undertaken whenever possible.
Keywords: Medial meniscus, Ramp lesion, Repair, Healing, Anterior cruciate ligament, Knee.

Introduction

Meniscal lesions of the posterior horn of medial meniscus (MM) are very often associated with an ACL rupture (16,32,49). Certain specific lesions of the Medial Meniscus (MM) such as meniscosynovial or meniscocapsular tears and meniscotibial ligament lesions are associated with 9 to 17% of ACL Tears (8,21) and are seldom recognized on preoperative magnetic resonance imaging (MRI) scans (8,38). They also often remain undiagnosed when viewing from the standard anterior compartment arthroscopic portals including a probing. They were named in the 1980s by Strobel et al (42) as ‘‘Ramp’’ lesions of the meniscus and have drawn a lot of attention over the past few years (3,8,21,38,42). The aim of this article will be to write a narrative review of this Ramp meniscal lesion.

History
Hamberg et al (15) first described “a peripheral vertical rupture in the posterior horn of the medial or lateral meniscus with an intact body” in 1983. They repaired these lesions through a postero-medial vertical arthrotomy; with the belief that the capillary blood supply from the capsule aids healing of the meniscus. They reported promising results (84% healing) in old and new lesions alike, thus providing some valuable insight into the philosophy of meniscal conservation. Morgan et al (25) in 1991 described the first arthroscopic vertical suture of the PHMM using Polydioxanone (PDS) sutures with an outside-to-inside technique. They reported a 16% failure rate occurring in patients with a concurrent ACL injury. They proposed that the rotation axis of the knee joint was altered in an ACL deficit knee thus placing excessive loads on the posterior horn of the medial meniscus. The kinematics of the posterior horn of the medial meniscus in the ACL deficient knee was therefore not conducive to meniscal healing after repair despite a peripheral blood supply. They also noted that, when combined with an ACL reconstruction, peripheral meniscal repair healing rates improved and approached those obtained in an ACL intact knee (25). Ahn et al (5) in 2004 described the first clinical series of an arthroscopic all-inside suture technique for tears in posterior horn of medial meniscus. Using a suture hook thorough 2-posteromedial portals, PHMM tears were repaired with concurrent reconstruction of the ACL. They concluded that the arthroscopic all-inside vertical suture using a hook resulted in a high healing rate even in large and complex vertical tears. Seil et al (38) in 2009 highlighted the indications for meniscal repairs based on the presence of associated ligamentous injuries and morphology of the lesion.
They advocated that Meniscal repairs be ‘‘ideally’’ carried out in:
1. Young patients (< 40 years)
2. No associated joint degeneration.
3. Vertical lesions in the peripheral third of the meniscus (3mm of the meniscosynovial junction) (4) and in conjunction with an ACL reconstruction.
4. Significantly displaced bucket-handle tear or an MMPH tear with vertical step off (5).

Epidemiology
The prevalence for a meniscal lesion with an ACl tear has been reported between 47% to 61% (13,14). In 2010, S. Bollen et al (8) reported menisco-capsular lesions in 9.3% of their prospective series of 183 ACL reconstructions whereas Liu et al (21) described a prevalence of 16.6% in a series of 868 consecutive ACL reconstructions. In our series (40) on ACL deficient knees, a meniscal tears was identified in 125 out of the 302 patients. Following a systematic algorithm for exploration of the knee joint (Figure. 1), we found that; 75 (60%) medial meniscal body lesions were diagnosed through a standard anterior portal exploration, 29 (23.2%) ramp lesions were diagnosed during exploration of the posteromedial compartment, and 21 (16.8%) were discovered by probing the tear through a posteromedial portal and after minimal debridement of a superficial soft tissue layer with a motorized shaver. All-in-all, 42% (21/50) of the lesions diagnosed via inspecting the posterior compartment appeared only after superficial soft tissue debridement and were classified as ‘‘hidden lesions.’’ An ACL injury with an age at presentation above 30 years, male sex and a delay between injury and surgery are considered risk factors for concomitant meniscal lesions (8).

Biomechanical Implication on ACL
The importance of the meniscus in stabilizing the knee joint in chronically ACL-deficient knees has been validated by multiple studies (9, 39). A Peripheral posterior horn tear is caused by the recurrent trauma sustained by the Medial Meniscus, which acts as a ‘‘bumper’’ in ACL-deficient knees (2). In addition, contraction of the semimembranosus at its insertion along the posteromedial capsule may stress the peripheral meniscus, resulting in meniscocapsular tearing (17). This could occur at the time of injury or during subsequent instability episodes in the subacute or chronic situation (43). A capsular injury might also occur during the so-called medial contrecoup injury (18) after subluxation of the lateral tibial plateau and during subsequent reduction of the tibia (41).  A longitudinal tear of the PHMM in ACL-deficient knees increases the anterior translation of the tibia and a repair of this lesion reduces Anteroposterior tibial translation significantly at most flexion angles (17) and most prominently at 30 degrees of flexion (12, 30).  Peltier et al (30) observed that the PHMM was stabilised by the meniscotibial ligament posteriorly, which in turn inserted onto the posterior aspect of the proximal tibia. The capsule of the knee joint inserts more distally on this posterior surface. The posterior capsule hence lacks insertion onto the posterior aspect of the PHMM. Detachment of the ligament therefore results in an abnormal mobility of the entire PHMM, producing rotational instability. The authors observed that the division of the menisco-tibial ligament resulted in a statistically significant increase in internal tibial rotation. Such lesions occur either in the mid-substance (repairable) or as a bony avulsion (irreparable). Stephen et al (41) reported that the anterior tibial translation and external rotation were both significantly increased compared with the ACL-deficient knee after posterior meniscocapsular sectioning and these parameters were not restored after ACL reconstruction alone but were restored with ACL reconstruction combined with posterior meniscocapsular repair.
Classification [46] (Figure. 2)
We have proposed a classification for ramp lesions which is as follows:
Type 1: Ramp lesions. Very peripherally located in the synovial sheath. Mobility at probing is very low. (B)
Type 2: Partial superior lesions. It is stable and can be diagnosed only by trans-notch approach. Mobility at probing is low. ©
Type 3: Partial inferior or hidden lesions. It is not visible with the trans-notch approach, but it may be suspected in case of mobility at probing, which is high. (D)
Type 4: Complete tear in the red-red zone. Mobility at probing is very high. (E)
Type 5: Double tear.

figure-1-and-2

Surgical Technique (46)
With the patient supine on the operating table, a tourniquet is placed high on the thigh, and the knee placed at 90º of flexion with a foot support to allow full range of knee motion.  Using standard arthroscopy portals, high lateral as viewing and medial portal for instrumentation, articular inspection is performed and we engage a probe in the posterior segment of the meniscus and force an anterior excursion of the meniscus. If the meniscus subluxates under the condyle, it is an indicator for instability and an indirect sign of a ramp lesion. Direct visualization of the posteromedial compartment is mandated to diagnose and repair these lesions. Even if the meniscus appears stable on probing, a systematic exploration of the posterior segment must be performed using the protocol in (Figure.1) Through a Guillquist maneuver, the arthroscope in the anterolateral portal is advanced in the triangle formed by the medial femoral condyle, the posterior cruciate ligament, and the tibial spines. With valgus force applied initially in flexion followed by knee extension, the arthroscope is pass through the space at the condyle border of the medial femoral condyle. Internal rotation applied to the tibia further enhances visualization; this causes subluxation of the posterior tibial plateau causing a posterior translation of the middle third segment. Almost two-thirds of peripheral lesions can be diagnosed with this maneuver. Tears of the posterior segment must be approached posteromedially. The posteromedial portal is placed superior to the hamstring tendons and posterior to the medial joint line, also trans illumination allows observation of the great saphenous vein, that is in close relation to the infra-patellar branch of the internal saphenous nerve, that must be avoided.  The needle is introduced from outside to inside, in the direction of the lesion. The portal is prepared with a number 11blade scalpel under arthroscopic control. The all-inside suture is accomplished with or without a working cannula, depending on the surgeons choice. Using a shaver the lesion is debrided and the intervening fibrous tissue is excised. Suturing is carried out using a 25º curved hook (Suture Lasso, Arthrex): a left curved hook is used for a right knee and vice versa. The curved hook is loaded with a no. 2 non-absorbable braided composite suture (Fiberwire, Arthrex) or a absorbable no.1 PDS introduced through the posteromedial portal. The curved hook must penetrate the peripheral wall of the MM, and then the inner wall of the MM. The free end of the suture in the posteromedial space is grasped and brought out through the posteromedial portal. A sliding knot (fishing knot type) is applied to the most posterior part of the meniscus with the help of a knot pusher and then cut. The sutures are repeated as required depending on the length of the tear (usually we place a knot every 5 mm of the tear). During suturing, care must be taken to not splinter the meniscus that can occur with multiple failed attempts to pass the curved hook. Additionally, entangling of the sutures must be avoided. In some patients, the tear may extend to the mid-portion of the meniscus requiring further repair through the standard anterior portal with meniscal suture anchor and/or an outside-in suture. The stability of the suture is then tested with the probe.

figure-3

Post-operative
Post operatively, active and passive range of motion is limited to 0-90º in the first six weeks. Full weight bearing is allowed by six weeks post-operatively. Jogging is permitted after 4 months, pivoting activity at 6 months, and unrestricted activities by 9 months.

Results
Ahn et al (4) in 140 patients showed complete healing in 118, incomplete healing in 17 and failure 5 repairs. The clinical success rate was 96.4% (135 of 140). Healing was associated with the type of tear and location. Incomplete healing and failures had complex tears or tears involving the red-white zone. Seventeen patients had incomplete healing at second-look arthroscopy but had no clinical sign of a meniscal tear. The mean Lysholm score and HSS scores improved post surgery (Table. 1) and 134 (95.7 %) patients had a normal (104 patients, 74.3%) or nearly normal (30 patients, 21.4%) the objective IKDC scores. In our prospective evaluation (46) of 132 patients undergoing a MM repair through a posteromedial portal in conjunction with ACL reconstruction, fifteen patients were found to be symptomatic according to Barret’s criteria on follow-up (6). The clinical failure rate was 9%, 4.9% in the subgroup “limited tear” and 15.7% in the subgroup “extended tear.” A limited tear was defined as one restricted to the posterior segment whereas those with a tear that extended to the mid-portion of the meniscus were classified as an extended tear. The extended tears required an additional repair through the standard anterior portal with meniscal suture anchor and/or an outside-in suture. The extended lesions had an increased risk of clinical failure. Out of the fifteen, 9 patients underwent revision surgery. Nine patients (6.8%) had failure of the meniscal repair; 3.7% (3/81) occurred in the subgroup of limited tears and 11.7% (6/51) in the subgroup extended tears. In the subgroup of extended tears, the cumulative survival rate did not decrease significantly and were not associated with a significant increased risk of revision of the MM. The average subjective IKDC improved at last follow-up and The Tegner activity scale at the last follow-up was slightly lower than before surgery (Table. 1).

table-1

Complications
The main complications may be related to the posteromedial portal placement. Damage to the infra-patellar branch of the saphenous nerve due to a posteromedial portal has been reported owing to the proximity of the nerve to the portal site causing hypoesthesia or paresthesia below the patella (27). Having said that, hypoesthesia resulting from harvesting the Semi-tendinous and Gracilis tendons in a concomitant ACL reconstruction may be responsible for 74% of the times (35). Transient hypoesthesia of the Sartorial branch of the saphenous nerve has also been reported probably due to an access portal situated too anteriorly (24). McGinnis et al (23) studied the neurovascular safety zone for the posteromedial access and recommended a portal through the posterior soft spot located formed by the medial head of the gastrocnemius, the tendon of the semimembranosus and the medial collateral ligament at the posterior aspect of the joint line for creation of the posteromedial portal. Hemarthrosis due to the long saphenous vein injury may occur in the postero medial approach (27). Among other complications, an iatrogenic medial meniscus tear may occur from repeated attempts at suturing the meniscus with a curved hook, rending suture impossible. Also, to our knowledge no popliteal artery, common peroneal and tibial nerve lesions has been reported, however they are at risk of damage during creation of the posterior portals. These complications may be avoided by placing the posterior portals with knee in 90 degrees of flexion. This moves the neurovascular structures posteriorly, away from the posteromedial portal site. Also, the Guillquist maneuver that provides trans-illumination may help visualize the course of the superficial veins and the accompanying nerves thus preventing inadvertent damage (35). Our series (46) also has a low complications rate with only two cases of hemarthrosis post operatively. Also, no patient developed a neuroma around the location of the posteromedial approach, although it was difficult to be accurately determining the incidence of saphenous nerve lesions due to the posteromedial approach as the hamstring tendon harvesting can cause hypoesthesia in the different territories of the saphenous nerve.

table-2

Discussion
The forces acting on the MM increase by as much as 200% after an ACL injury. Furthermore, forces acting on the ACL replacement graft increase by 33% to 50% after a medial meniscectomy (12,28). Deficiency of the medial meniscus has therefore been proposed as a secondary cause of ACL failure. It has thus been recommended that an ACL-deficient knee be reconstructed to protect the menisci (39,50). Conversely, identification and repair of a ramp lesion during an ACL reconstruction is imperative to reduce the risk of secondary graft failures, as these lesions may increase the anterior tibial translation (2,12, 30) and subsequently the strain on the graft.  The success rates for meniscal repairs have been reported to be from 70% to 90% in vascular regions (11,13,16,36). Anh et al (12) reported a clinical successful healing rate of 96.4% in PHMM repairs with concomitant ACL reconstruction. Tenuta and Arciero (45) reported higher healing rates in concomitant ACL reconstruction than for isolated repairs (90% vs 57%). Meniscal repair in conjunction with ACL reconstruction has been reported to create a favorable environment for meniscal healing because of fibrin clot formation associated with intra-articular bleeding generated during ACL reconstruction (44).  Multiple techniques for suturing the meniscus are available. The indications, advantages and disadvantages of each are mentioned in (Table.2). The all-inside suture repair technique using a hook is especially useful in a ramp lesion, as the use of newer devices makes the repair procedure blind and placing a suture in the vertical configuration is technically challenging. In addition Choi et al reported that the use of meniscal devices failed to provide sufficient strength of fixation. They recommended that during suturing, the posteromedial capsule should be elevated and approximated to the PHMM to ensure precise approximation of tear site (10). In spite of the development of the newer all-inside suture devices, the failure rate of the repair of PHMM tears continues to remains high, (19) which may be attributed to various factors that include inadequate visualization and debridement of the lesions of the PHMM; failure to confirm the reduction of the lesion with the all inside technique (48) and tissue failure due suture pullout through the meniscal tissue (45).
The mechanical strength of the vertical suture is greater than that of the horizontal suture (45). Having said that, most meniscal fixators cannot facilitate meniscal repair in a vertical mattress fashion (7,34) especially in the posteromedial corner of the medial meniscus, small or tight knee joints. Sutures spaced at every 3 to 5 mm have been recommended however; the optimal number is unknown (44). Pujol et al (33) using meniscal devices reported an overall healing rate of 73.1%. van Trommel et al (47) reported similar results (76%) with the outside-in technique. (Table. 3) Both studies observed a strong trend toward a relatively lower healing rate of the posterior horn (Zone A), as compared with the body (Zone B). (Table. 4) They also observed that, partial healing in all tears extending from the posterior to the middle third of the medial meniscus. We observed similar results in our study with a higher failure rate in the extended tear subgroup (6/51) (46). Pujol et al (33) attributed this to the difficulty in performing an adequate abrasion of the posterior segment using standard anterior arthroscopic portals whereas van Trommel et al (47) attributed that same to the relatively anterior placement of the needles with the outside-in technique, making a perpendicular repair extremely difficult. This resulted in a decrease in the coaptation force of the sutures. In addition, they observed that an oblique suture placement in the posterior zone with the outside-in technique made the sutures enter more anterior than they exit. Ahn et al (5) postulated that a torn posterior menisco-capsular structure moved inferiorly against the remaining meniscus, displacing the tear during knee flexion. They suggested that this motion of the torn medial meniscus can partially explain the slow healing observed in MMPH peripheral rim tears despite a rich vascular supply to the red-red zone. Pujol et al (31) in 2011 reported a secondary meniscectomy rate of 12.5%. The authors observed that the volume of meniscus removed decreased in 35% of cases, with respect to the initial tear and noted that a secondary meniscectomy following repair can partially save the meniscus and the failure called a ‘‘partial’’ failure. They recommended that suturing a tear therefore preserved the meniscal volume in a subsequent meniscectomy performed for a failure of repair or repeat tears. Tachibana et al (44) reported newly formed meniscal tears occurring in an area different from the initial repair site, on the surface of 34.5% of the healed and incompletely healed menisci. These new injuries were 1 to 3 mm in length partial- or full-thickness lesions and located central to the peripheral repair. In our series (46), the high rate of recurrent tear was as a result of newly formed tears that were confirmed on the surface of 5 menisci. It is conceivable that these injuries were attributable to a residual cleft left by the path of the Suture Lasso and maintained by the use of a strong no. 2 non-absorbable suture.

table-3

These clefts on the avascular meniscal substance may remain in situ without healing and would favor the recurrence of a more centrally located lesion in the white-white zone. Using a small suture hook device may therefore be desirable as it may reduce the size of the clefts created during suturing. In addition, the ‘cheese wiring effect’ due to the higher co-efficient of friction of a non-absorbable suture may contribute to a failure. We therefore decided to change our suture from a strong non-absorbable suture to a number 0 or 1 PDS suture, which are recommended to reduce the risk of these newly formed injury (37).
Nepple et al (26) observed that the time between injury and repair was the most important factor influencing healing. The zone of tear in reference to blood supply is another major factor affecting the results of a meniscal repair and ramp lesions in the red-red zone are expected to heal more readily than are those in the red-white zone (20). The criteria for healing based on follow-up arthro-CT corresponding to thickness of healing was suggested by Henning et al (36) can supplement clinical evaluation to improve diagnostic accuracy (Figure 3). The clinical failure rate in a systematic review ranged from 0% to 43.5%, with a mean failure rate of 15% (22). Failures after two years represented nearly 30% (26). Although numerous studies have reported short-term outcomes of various techniques of meniscal repair, relatively few have reported medium to long-term outcomes. The rate of meniscal repair failure appears to increase from short-term follow-up to medium to long-term follow-up regardless of the technique (26). There are limited numbers of studies assessing the outcomes of meniscal repair using the PM approach (4,5,10,46). Further prospective analysis with long – term follow-up is required to validate the promising early results of meniscal repairs performed with this approach.  Finally, improved visualization is the key to achieving good meniscal repair results as it improves diagnosis of longitudinal tears in posterior horn MM (30), safeguards better debridement prior to repair and ensures good approximation of the torn ends under vision (1). It is thus important to perform a systematic exploration of the knee during an ACL reconstruction (Figure 1). A transnotch visualization combined with palpation of the meniscus with a needle or probe through the postero-medial portal aids in diagnosis of ramp lesions, which may otherwise be missed. Hidden lesions furthermore may be either very peripheral, covered by a layer of synovial or scar tissue or may not be reachable with a probe. It is therefore essential to identify these lesions during an ACL reconstruction and repair them whenever they are found to be unstable (40).

table-4

Conclusions
A systematic posteromedial exploration allows discovery of and debridement of the hidden MM lesion and repair with a suture hook device is associated with low morbidity. Failure Rates following a ramp lesion repair are low and occurs during the first 20 months. Even if a failure occurs the subsequent meniscectomy is limited and the volume of meniscal tissue debrided is reduced. An arthroscopic repair of meniscal ramp lesions should therefore be undertaken whenever possible.

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How to Cite this article:. Sonnery-Cottet B, Tuteja S, Barbosa NC, Thaunat M. Meniscus Ramp Lesion. Asian Journal of Arthroscopy  Aug – Nov 2016;1(2):28-34.

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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.

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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

 

(Abstract)      (Full Text HTML)      (Download PDF)

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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