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Outside -in Meniscus repair

Sachin Tapasvi, Anshu Shekhar

Volume 1 | Issue 2 | Aug – Nov 2016 | Page 19-22


Author: Sachin Tapasvi[1], Anshu Shekhar[1]

[1] The Orthopaedic Speciality Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004.

Address of Correspondence

Dr Sachin Ramchandra Tapasvi
The Orthopaedic Speciality Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004
Email: stapasvi@gmail.com


Abstract

Meniscus tears are common knee injuries presenting to an arthroscopy surgeon. Repairing the meniscus to salvage knee function and biomechanics is indicated where ever possible, since the problems after meniscectomy are well established now. Inside-out meniscus repair is a very useful technique to repair tears in the posterior and middle third of both menisci. Proper adherence to technique and safety incisions reduce the risks and complications to almost the level of an all-inside meniscus repair. The technique allows precise placement of sutures, causes minimal meniscus tissue trauma, has produced good healing rates, is cost-effective and is basically, an indispensable tool in the armamentarium of any knee surgeon.
Key Words: Meniscus, Meniscus repair, Inside-out, Safety incision, Complications.


Introduction

Meniscus injuries are one of the most common findings in an orthopaedic practice. These injuries lead to a devastating effect on knee dynamics ultimately leading to arthritis. Studies by Fairbanks [1] suggest that the contact stresses after meniscectomy increase considerably leading to symptoms and knee dysfunction. The main function of meniscus, which is to increase surface area for contact of femur over tibia and also to act as a shock absorber for impact activities makes it mandatory to try and save the meniscus whenever possible. Since then the main focus of arthroscopists is to repair and preserve the meniscus. Ikeuchi described the first technique of meniscus repair in Tokyo in 1979 [2]. Over the years, many surgeons have developed techniques for meniscus repairs. The focus of this article is to have an overview of outside-in repair technique for meniscus repair. The outside-in meniscus repair is basically a technique where suture material is passed from outside the knee, retrieved inside the joint and then looped around the tear, again tunneled outside the joint where free ends are tied over the joint capsule. This technique requires the least expensive material and also gives the surgeon modularity to modify the technique to his liking. Many modifications have been done to reduce the cost and simplify the procedure which we will be looking at in details.

Indications
Meniscus repair probability depends on site, size and type of tear. The ideal indication of outside-in meniscus repair is vertical or longitudinal tear in peripheral third of meniscus in a young patient with a stable knee or if the patient is going to have a concomitant ligament reconstruction. For outside-in technique, because we insert a sharp instrument blindly into the joint, the indications are
1: Anterior horn tears
2: Vertical and Longitudinal tears in anterior 2/3rd of meniscus.
* Posterior horn tears may also be tackled by outside-in technique but it has a risk of neuro-vascular injury.

figure-1

Techniques
Many techniques for outside-in meniscus repair are proposed, each one following the same principle but tweaked by authors to make it either efficient or simpler. General preparation for meniscus repair includes high tourniquet, a leg stopper to keep the leg in 90 degree flexed position [3]. After painting and draping the leg, arthroscopy is performed to identify the site and type of the tear. Medial meniscus tear should be tackled in 10o degree flexion with valgus stress to tighten the capsule. Transillumination can be used to identify the saphenous vein and nerve before a needle is inserted, thus avoiding damage to those structures. Anterior horn tears are repaired in 60o to 90o of knee flexion and the needle insertion site is kept anterior to the pes anserinus to avoid saphenous nerve and vessels. Lateral meniscus tears are repaired in figure-of-4 position so that the peroneal nerve shifts posterior to the joint-line. Posterior horn tears of medial meniscus are best repaired when the needle is placed just posterior to pes anserinus tendons in 10-15o flexion, for lateral meniscus posterior horn tears the knee is kept in figure of 4 or 90o flexion. Abrading the torn surfaces of meniscal fragments with a meniscal rasp helps increase the healing potential. A needle is placed in the torn fragments, one in the femoral side and other in the tibial side in horizontal tears, piercing both fragments in a longitudinal tear and one in anterior and other in posterior part of a radial tear. The orientation of suture can be vertical mattress or horizontal mattress sutures depending upon the type of the tear and accessibility. Vertical mattress sutures have more pull-out strength as they are able to co-apt the circumferential fibres of the meniscus. Reduction and suturing of fragments have various techniques which have been described by many authors. One of the earliest of the techniques described was the Mulberry knot technique, where two separate non absorbable suture thread are passed in the superior and inferior portion of the torn meniscus using a bold needle. The sutures are pulled out from the anterior viewing portal, a mulberry knot is tied to each suture thread and then the sutures are pulled out along with the needles through which they were inserted thus reducing the meniscus tear. The free suture ends are then tied over the capsule from the point where they were inserted. Other technique is when a knot is tied with a few throws of simple suture to the 2 sutures outside the joint and then 1 end is pulled back in the joint with the knot piercing the meniscus and finally forming a loop suture around meniscus. A dilator knot which is a small sized knot may be tied preceding the big knot to help it pass through the meniscus and not tear it when it is pulled. The suture ends are tied over the capsule. A monofilament steel loop which is commercially available may be used to retrieve sutures as well. In this technique a loop is passed through the needles in the joint and the sutures are sewn into the loop hole from the portals using a grasper. The sutures are then retrieved over the capsule by retracting the loop. The procedure is repeated with other end of the same suture and the loop coming in through other fragment of the meniscus and the 2 free ends are tied on the capsule. A non-absorbable suture loop may be used instead of readymade loops. The progression of sutures is advised to be consistent in a way that superior and inferior fragments in a cleavage tear are reduced in sequence of superior first then inferior with repetition of the same sequence to have a uniform reduction of meniscus. Bucket handle tears are first stabilised by a central reduction sutures, followed by an anterior and a posterior sutures in sequence for uniform reduction. Many modified outside-in techniques have been described by various authors. Keyhani et al [4] have described a technique for vertical and horizontal loop sutures for anterior and middle third meniscus tears. A No. 0 PDS suture is passed through meniscus tibial end with a bold needle and the intra-articular end is retrieved through the joint. The procedure is repeated with other free end of the suture passed through femoral surface of meniscus and retrieved through same portal as the first suture end. A sliding knot is tied with few simple knots over the meniscus and the free ends are cut. Ahn et al [5] described a technique for reducing and repairing a free unstable end of anterior horn of the meniscus after decompression of cyst. They used a Linvatec hook, used for all inside suturing, to pierce the anterior free end of the horn using the loop from anterior portal. A suture is passed within the hook and the end is retrieved from the portal. With both the free ends now out from the same portal a loop is passed with a needle from capsule piercing the meniscus from outside -In. Loop is retrieved through same portal as sutures. The sutures are retrieved over the capsule by passing them from the loop and then retracting the loop and the needle. The suture ends are then tied over the capsule using a small stab incision.Yiannakopoulis et al [6] showed a simple technique where they used a spinal needle / suture hook to pierce longitudinal tears at first posteriorly, retiring the suture through portal. Keeping the same suture in the needle, the meniscus is pierced again a bit anterior-ly and the free end again retrieved through portal anteriorly. The free ends are tied with sliding knot over the meniscus giving a simple and effective configuration. Landsiedl [7] used needles to introduce two suture loops, one anterior and other a bit posterior to the first one. Both loops are retrieved outside the joint through portal and tied together and then one end is pulled gain bringing the knot inside the joint, the knot passing through the meniscus and thus forming a loop suture over the meniscus. The free ends are tied over the capsule. Chong et al [8] wrote about a technique where they passed a Loop through needle piercing both fragments of the meniscus and through the anterior portal introduced a reverse loop via needle with free ends inside the joint and loop end outside the joint . The free end is passed through the loop and loop is pulled with the suture. The process is repeated with the other free end of the reverse too and then when the 2 ends are re-trieved outside the joint they are tied over the capsule leaving no knot in the joint.

figure-2

Complications
The technique of outside-in meniscus repair can be challenging and demanding. It may not always be possible to get the needles in right part of the meniscus or perpendicular to the tear in the first place. These techniques require a longer learning curve and patience to get sutures and needles placed in right spot. The outside-in technique has two stages which are critical. One is when a sharp pointed instrument is inserted in the joint and other while securing the suture by tying a knot over the capsule. Though techniques and landmarks are defined by many authors to avoid these injuries clinical practice not being perfect leads to these complications. Peroneal nerve injury is common if the knee is not placed in enough flexion and needle is inserted posterior while doing lateral meniscus repair. Saphenous nerve is at risk of injury during medial meniscus repairs. Posterior neurovascular structures are at risk of injury while performing Posterior horn medial meniscus (PHMM) repair. Hassad Sobhy [9] and colleagues carried out cadaveric dissections to evaluate the safety of outside-in meniscus techniques while performing PHMM repairs. They concluded that inserting a needle through a slit in the skin just over the semitendinosus has significant lower risk of damaging either popliteal vessels or saphenous nerve. Chondral damage during insertion of needles into the joint is a well-known complication. This can be avoided by carefully placing the needles and not thrusting them in. Intra-articular knots which are used to secure the repair in some techniques are also a cause of problems. Kelly IV and colleagues [10] carried out a second look arthroscopy in patients who had synovitis after meniscal repair with mulberry knot technique. They evaluated the prevalence of aseptic synovitis and evidence of chondral damage. The synovitis and clinical symptoms subsided after partial meniscectomy. Retears and healing problems are also part of the complications spectrum. Healing problems are most common in the posterior third of the meniscus since it is difficult to get the coaptation right due to improperly oriented needles. Posterior capsule tightness in a repair done in excessive flexion may also lead to extension loss.

Results
The results for outside in meniscus have been extremely promising. Out of the studies which have evaluated healing rates and outcome of meniscal repair, all of them have good healing rates with outside-in technique. This may be due to modularity that the surgeon has while placing the sutures. In a study by Morgan and Casscells [11] which evaluated clinically their patients who underwent outside-in repair for posterior horn tears, the authors reported 98% good to excellent clinical outcomes. The fallacy of this study was that it was only a clinical as-sessment. Morgan et al [12] did a study of 353 meniscus repairs done by outside-in technique. He performed second look arthroscopy on 74 of them at average 1 year post op and found out of the 84 % patients who had asymptomatic healing, 65 % had complete healing and 19% had incomplete healed meniscus. Interestingly all of the failures were in ACL deficient knees. They also concluded that it takes around 4 months to have visual evidence of healing.
Van Trommell et al [13] evaluated patients with outside-in repairs at a mean duration of 15 months by second look arthroscopy, arthrogram or MRI. They found 74% patients had complete or partial healing. All the Re-tears were in posterior and middle third of meniscus. Posterior third of meniscus is notorious for poor healing. They attributed improperly placed sutures for these failures. Mariani et al [14] gave accelerated rehabilitation to their patients of ACL reconstructions with outside-in meniscus repair and found 77% good to excellent results. All the new and modified techniques described above in techniques section also showed good to excellent clinical outcomes in their respective study at mid-term follow up. Hantes et al [15] published the only study available where they evaluated and compared outside-in, inside-out and all inside meniscus repair techniques. They clinically evaluated 57 patients who underwent meniscus repair. 17 out of 57 were in outside-in cohort and showed 100% clinical healing rate as compared to 95 % of Inside-out and 65% of All-inside cohort. Only one patient had saphenous palsy which resolved over 4 months, as compared to inside-out cohort which had four incidences of nerve palsy. The only downside attributed to outside-in cohort is longest surgical time as compared to other cohorts with and average surgical time of 38.5 minutes.

Conclusions
Outside-in meniscus repair have stood the test of time to be the most effective meniscus repair techniques. It provides surgeons the ability to modify the procedure to their liking and giving certain modularity helps in perfecting the suture placement techniques. This has resulted in better co-aptation of torn fragments leading to stable repairs and better healing rates. This is a demanding technique  but has equally good proven results to make the steep learning curve worthwhile. The other advantage is less likelihood of complications if the identified landmarks and prescribed guidelines from previous studies are followed.  The material and equipment required for the surgery is  inexpensive and thus provides  good cost-cutting in patient care without compromise in the results. New and modified Outside-in repair technique still have to be explored but the existing ones provide for repairing most of the tears giving equally good if not better outcomes than other techniques.


References

1.FairbankTJ.Kneejointchangesaftermeniscectomy.JBoneJointSurg1948;30B(4): 664 –70
2. Ikeuchi H. Trial and error in the development of instruments for endoscopic knee surgery. Orthop Clin North Am. 1982;13(2):255.
3. Rodeo SA. Arthroscopic meniscal repair with use of the outside-in technique. Instr Course Lect. 2000;49:195-206.
4. Keyhani S, Abbasian MR, Siatiri N, Sarvi A, Kivi MM, Esmailiejah AA. Arthroscopic Meniscal Repair: “Modified Outside-In Technique”. Arch Bone Jt Surg. 2015 Apr;3(2):104-8.
5. Ahn JH, Wang JH, Yoo JC, Kim SK, Park JH, Park JW. The modified outside-in suture: vertical repair of the anterior horn of the meniscus after decompression of a large meniscal cyst. Knee Surg Sports Traumatol Arthrosc. 2006 Dec;14(12):1288-91. Epub 2006 Jul 5.
6. Yiannakopoulos CK, Chiotis I, Karabalis C, Babalis G, Karliaftis C, Antonogiannakis E. A simplified arthroscopic outside-in meniscus repair technique. Arthroscopy. 2004 Jul;20 Suppl 2:183-6.
7. Landsiedl F. Improved outside-in technique of arthroscopic meniscal suture. Arthroscopy. 1992;8(1):130-1.
8. Chong KC, Chan BK, Chang HC. A simple method of meniscus repair using the arthroscopic outside-in technique. Arthroscopy. 2006 Jul;22(7):794.e1-5.
9. Sobhy MH, AbouElsoud MM, Kamel EM, Desouki AM. Neurovascular safety and clinical outcome of outside-in repair of tears of the posterior horn of the medial meniscus. Arthroscopy. 2010 Dec;26(12):1648-54.
10. Kelly JD 4th, Ebrahimpour P. Chondral injury and synovitis after arthroscopic meniscal repair using an outside-in mulberry knot suture technique. Arthroscopy. 2004 May;20(5):e49-52.
11. Morgan CD, Casscells SW. Arthroscopic meniscus repair: a safe approach to the posteri-or horns. Arthroscopy 1986;2(1):3–12.
12. Morgan CD, Wojtys EM, Casscells CD, et al. Arthroscopic meniscal repair evalu- ated by second-look arthroscopy. Am J Sports Med 1991;19(6):632–7 [discus- sion: 637–8].
13. van Trommel MF, Simonian PT, Potter HG, Wickiewicz TL. Different regional healing rates with the outside-in technique for meniscal repair. Am J Sports Med.1998 May-Jun;26(3):446-52.
14. Mariani PP, Santori N, Adriani E, et al. Accelerated rehabilitation after arthroscopic me-niscal repair: a clinical and magnetic resonance imaging evaluation. Arthroscopy 1996;12(6):680 – 6.
15. Hantes ME, Zachos VC, Varitimidis SE, Dailiana ZH, Karachalios T, Malizos KN. Arthroscopic meniscal repair: a comparative study between three different surgical techniques. Knee Surg Sports Traumatol Arthrosc. 2006 Dec;14(12):1232-7.Epub 2006 Jul 21.
16. Dave LY, Caborn DN. Outside-in meniscus repair: the last 25 years. Sports Med Arthrosc. 2012 Jun;20(2):77-85..


How to Cite this article:. Tapasvi SR, Shekhar A. Outside -in Meniscus repair. Asian Journal of Arthroscopy. Aug – Nov 2016;1(2):19-22 .

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Inside-Out Meniscus Repair – A Review

Sachin Ramchandra Tapasvi, Anshu Shekhar, Shantanu Sudhakar Patil

Volume 1 | Issue 2 | Aug – Nov 2016 | Page 14-18


Author: Sachin Ramchandra Tapasvi [1], Anshu Shekhar [1], Shantanu Sudhakar Patil [1]

[1] The Orthopaedic Specialty Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004.

Address of Correspondence

Dr Sachin Ramchandra Tapasvi
The Orthopaedic Speciality Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004
Email: stapasvi@gmail.com


Abstract

Meniscus tears are common knee injuries presenting to an arthroscopy surgeon. Repairing the meniscus to salvage knee function and biomechanics is indicated where ever possible, since the problems after meniscectomy are well established now. Inside-out meniscus repair is a very useful technique to repair tears in the posterior and middle third of both menisci. Proper adherence to technique and safety incisions reduce the risks and complications to almost the level of an all-inside meniscus repair. The technique allows precise placement of sutures, causes minimal meniscus tissue trauma, has produced good healing rates, is cost-effective and is basically, an indispensable tool in the armamentarium of any knee surgeon.
Key Words: Meniscus, Meniscus repair, Inside-out, Safety incision, Complications.


Introduction

Once considered expendable, the vital role of meniscus in knee biomechanics is firmly established now. They are known for contributing to knee stability and congruity, resisting capsular and synovial impingement, load distribution and contribution towards screw home mechanism[1]. With advances in arthroscopy in terms of technique, instrumentation, optics and biomaterials, meniscus salvage has become a thrust area in this field today. The three basic techniques of meniscus repair: outside-in, inside-out and all-inside each have their indications, advantages and pitfalls. Henning et al first described the inside-out technique of meniscus repair, involving meniscal and meniscosynovial abrasion to promote healing, cannulated suture-needle delivery system for suture placement, a posteromedial or lateral skin incision for suture needle retrieval[2]. Here, we review the inside-out technique of meniscus repair.

Indications For Inside-out Repair And Technique
A meniscus tear must first be deemed suitable for repair, before deciding on the technique to be used. A non-degenerated, longitudinal tear, less than 3 centimeter and in the peripheral vascular zone is most amenable to repair[3]. An inside-out meniscus repair can be performed for the mid-third and posterior-third longitudinal tear of both the menisci[4]. With advances in all-inside meniscus repair implants and technique, this has gradually become the standard method of repair for posterior third longitudinal meniscus tears, replacing the “gold standard” method of inside-out repair[5]. Middle third tears, however, are readily amenable to repair by the inside-out technique without significant risk to neurovascular structures and possibly, without the need for a safety incision. Radial tears repaired by an all-inside or an inside-out horizontal construct have similar maximum failure loads [6]. The most recent systematic review comparing all-inside with inside-out isolated meniscus repairs did not reveal any difference in the failure rates, functional outcomes, and complications between the two methods[7]. However, the inside-out techniques has some distinct advantages. The zone specific suture needle delivery cannulae facilitate more precise and controlled suture placement, while allowing for revision and improvisation[8]. Also, the finer needles cause less iatrogenic damage to meniscus tissue, compared with the heavier all-inside implant insertion needles. This is especially vital when the meniscus tissue is tenuous, or in case of a complex tear. The finer needles also provide greater number of fixation points and captures more collagen tissue[8]. Another important advantage of inside-out repair technique is the significant savings in terms of implant cost of expensive all-inside repair devices [8].

Surgical technique
Patient position for inside-out meniscus repair can be either with a leg holder and table broken or on a flat table with thigh side support. A proximal thigh tourniquet is used for good visualization. A diagnostic arthroscopy is first performed via an anterolateral portal. A high anterolateral portal is useful if a meniscus repair is planned, to allow the needles to pass over the tibial spines without struggle. The anteromedial portal is created under vision with the aid of a spinal needle to allow easy access to medial and lateral menisci[8]. Typically, for a lateral meniscus repair, the anteromedial portal is higher to allow needles to negotiate the tibial spine[9].

figure-1

A 70 degree scope placed through the notch is helpful in viewing far posterior tears[9]. Assessment of the tear is done to decide whether to proceed with a repair or to resect the meniscus. Preparation of the meniscus tear is done next to potentiate healing. Granulation tissue must be debrided from both sides of the meniscus tear. Abrading the meniscal and peri-meniscal synovium, both superiorly and inferiorly, with a meniscus rasp (Acufex, Andover, MA) is an useful augment and aids in healing response[10]. Trephination is believed to create vascular channels and increase blood flow from a more vascular to a less vascular area[11][12]. A useful trick in bucket handle tears is to prepare the edges of the tear while the meniscus is still displaced and access to both sides is easy[8] (Figure 1). Fibrin clot prepared from the patient’s own blood is also widely used to enhance healing. It not only provides a scaffold, but also acts as an initiator and activator of the healing process[13]. When a meniscus repair is being performed in isolation, performing a limited notchplasty of the lateral femoral condyle with a shaver to create postoperative hemarthrosis and deliver marrow elements is another method of biological augmentation[9].

  figure-2

A. Technique for Medial meniscus inside-out repair[9]:
A 3-4 centimeter vertical “safety incision” (Figure 2) in the posteromedial aspect of the joint, posterior to the medial collateral ligament is first made with the knee in 60-900 flexion, to relax the hamstrings and popliteal neurovascular bundle. Transillumination aids in precise placement of this incision, with two-thirds being distal to the joint line and one-third proximal to it. The saphenous vein is carefully protected and sartorius fascia is incised and split proximally and distally with Metzenbaum scissors to preserve the Sartorius, Gracilis, Semitendinosus and the Saphenous nerve, which lies posterior to the Sartorius. Deep dissection is carried out bluntly with Metzenbaum scissors to create a plane between the medial head of gastrocnemius and capsule. This dissection is better performed from distal to proximal. Dorsiflexion and plantar flexion of the foot aids is location of the proper plane. A Henning retractor or a small bent spoon is then inserted anterior to the gastrocnemius, which protects the popliteal neurovascular bundle, retracts the pes and gastrocnemius and deflects the needle medially for retrieval. Repair can then begin, starting posteriorly and working anteriorly, with the knee in 10-200 flexion. Visualization of posterior meniscus can be improved by pie-crusting of the medial collateral ligament just below the joint line, while applying a valgus-external rotation force. Zone specific single and double lumen cannulae (Acufex, Andover, MA) inserted from the anterolateral portal are used to keep the meniscus reduced and for precise placement of the needles. For tears very close to the posterior root, it might become necessary to insert a curved cannula from the anteromedial portal, the curvature being directed away from the midline, to achieve proper trajectory for the suture needle. Non-absorbable multi-strand, long chain ultra-high molecular weight polyethylene (UHMWPE) sutures on 10 inch long needles (No. 2-0 FiberWire, Arthrex, Naples, FL) are used for the repair. The cannula is retracted 3-5 mm when the needle is pierced to increase the accuracy. This is done for the femoral side first, attempting to achieve a vertical mattress configuration, as this provides greater capture of strong circumferential fibers of the meniscus[8] (Figure 3).

figure-3

This might create a puckering of the meniscus, which subsides when tibial sided sutures are passed in a similar fashion to create a stacked repair and provide better coaptation of the tear area[14] (Figure 4). The needles are passed by one assistant, while a second assistant retrieves them using a needle driver, clips it using a hemostat and cuts the needles, taking care to avoid needle stick injury to anybody. If the needle is not visible after passing 1-1.5 centimeter, it must be withdrawn and reinserted at the same or different location with a different trajectory. Multiple sutures maybe passed at 3-5 mm intervals. The sutures may be tied sequentially as they are passed or at the end, after all have been passed out. When tying the knots, the knee must be kept in near or full extension to avoid imbricating the capsule, effectively causing a capsulorrhaphy and consequent flexion contracture. Drains may or may not be used and closure of the safety incision is done in layers.

figure-4

B. Technique for Lateral meniscus inside-out repair[9]:
The general principles remain the same as for a medial meniscus repair, with some important differences. The lateral vertical safety incision is made in a similar fashion, posterior to the fibular collateral ligament, two-thirds distal and one-third proximal to the joint line. The interval between biceps femoris and iliotibial band is dissected bluntly with a pair of Metzenbaum scissors, the common peroneal nerve being posteromedial to the biceps tendon (Figure 5). Dissection between the lateral gastrocnemius head and posterolateral capsule is similarly begun distally and a finger is used to assess the proper plane by flexing and extending the ankle. Staying anterior to the biceps and gastrocnemius lateral head reliably protects the common peroneal nerve A Henning retractor or bent spoon is placed as for the medial side, between the capsule and gastrocnemius. The anteromedial portal is made higher to avoid the eminence of the tibial spine, under vision over a spinal needle with the knee in a figure-of-4 position. If need be, accessory high anteromedial portal can be made to improve suture needle trajectory. The cannula is never inserted from the anterolateral portal due to the potential risk to the popliteal vessels, which lie just posterior to the posterior horn of the meniscus. Though no problems have been reported, it is best to avoid the popliteus tendon and pass sutures adjacent to this structure[9]. Capsular capture is not a problem on the lateral side and hence, knot tying can be done with the knee in flexion.

figure-5

Discussion

Result
The inside-out repair technique offers a success rate of 60% to 80% for isolated meniscus repairs and between 85% and 90% when performed with a concomitant ACL reconstruction[5]. Horibe et al performed second look arthroscopy for 132 meniscus repairs by inside-out technique. They report 74% excellent (completely healed) and 17% good (incomplete healing, partial thickness defect, stable on probing) result in their cohort[14]. Choi et al compared the results of suture repair of meniscus tears with concomitant ACL reconstruction, by all-inside and inside-out techniques using polydioxanone sutures. They found no difference in the healing rates on magnetic resonance imaging and no difference in Lysholm scores or Tegner activity scales between the two groups[15]. A systematic review by Grant et al was done to compare the effectiveness and complications of isolated inside-out and all-inside meniscus repairs. There was no statistical difference in clinical failure rate- 17% for all-inside and 19% for inside-out techniques. Subjective outcome, as measured by Lysholm score and Tegner activity scale was also comparable between the two groups. Inside-out repairs however, require 50% greater operative time. Nerve related symptoms were commoner (9%) in the inside-out group than in the all-inside group(2%). Upon pooling of all complication data, the Odd’s ratio was 0.55 (95% confidence interval = 0.27, 1.10). 0.55 (95% confidence interval = 0.27, 1.10)[16]. In a more recent systematic review, Fillingham et al compared current all-inside repair devices with the classical inside-out repair for isolated meniscus tears. They reported no significant differences in clinical or anatomic failure rates (clinical failure: 11% for inside-out versus 10% for all-inside, respectively, p=.58; anatomic failure: 13% for inside-out versus 16% for all-inside repairs, p=.63). Mean ± SD Lysholm score and Tegner score for inside-out repair were 88.0 ± 3.5 and 5.3 ± 1.2, while the respective scores for all-inside repair were 90.4 ± 3.7 and 6.3 ± 1.3. Complications occurred at a rate of 5.1% for inside-out repairs compared to 4.6% for all-inside repairs[7].

Complications and Problems:
The various anatomic structures in the needle trajectory can potentially be injured. By deploying safe surgical practices, they can be avoided. These are some of the commonly encountered problems:
1. Saphenous nerve injury- It can be avoided by the medial safety incision and keeping the nerve, which lies posterior to the Sartorius, retracted behind the pes tendons.
2. Common peroneal nerve injury- The nerve lies posteromedial to the biceps femoris. Injury is avoided by keeping the knee in flexion while making the lateral skin incision and carefully developing the plane between the biceps femoris and iliotibial band.
3. Popliteal vessels- are most at risk while doing a posterior lateral meniscus repair. Careful placement of retractor and always passing suture needles from the anteromedial portal with careful retrieval, avoids injury to the vessels.
4. Flexion contracture may develop- when the medial side sutures are tied with the knee in flexion, thus over tightening the posteromedial capsule.
5. Needle stick injury to the surgeon or assistants- avoided by careful, unhurried movements[8].
The inside-out technique also has an increased operative time, compared to all-inside technique by about 50%[16].

Conclusions
The inside-out method of meniscus repair is an excellent technique to repair tears in the middle and posterior-third of both menisci. With the rapid development of all-inside meniscus repair devices, this technique may not remain the “gold standard” but still has an important role, especially in repairing large and complex tears. When care is taken to protect the neurovascular structures posteriorly, and with due diligence to correct surgical technique, it is a safe, cost effective and proven method to salvage the menisci whenever possible.


References

1. Renstrom P, Johnson RJ. Anatomy and biomechanics of the menisci. Clin Sports Med. 1990 Jul;9(3):523-38.
2. Henning CE. Arthroscopic repair of meniscus tears. Orthopedics 1983; 6: 1130–1132.
3. Taylor S.A., Rodeo S.A. Augmentation techniques for isolated meniscal tears. Curr Rev Musculoskelet Med. 2013 Jun; 6(2): 95–101.
4. Yoon KH, Park KH. Meniscal Repair. Knee Surg Relat Res. 2014;26(2):68-76
5. Turman KA, Diduch DR. Meniscal repair: indications and techniques. J Knee Surg. 2008 Apr;21(2):154-62.
6. Branch EA, Milchteim C, Aspey BS, Liu W, Saliman JD, Anz AW. Biomechanical comparison of arthroscopic repair constructs for radial tears of the meniscus. Am J Sports Med. 2015 Sep;43(9):2270-6
7. Fillingham YA, Riboh JC, Erickson BJ, Bach BR Jr, Yanke AB. Inside-Out Versus All-Inside Repair of Isolated Meniscal Tears: An Updated Systematic Review. Am J Sports Med. 2016 Mar 17. pii: 0363546516632504. [Epub ahead of print]
8. Nelson C.G., Bonner K.F. Inside-out meniscus repair. Arthrosc Tech. 2013 Nov; 2(4): e453–e460.
9. Bonner KF. Meniscus repair: Inside-out suture technique. In: Jackson DW, editor. Master techniques in orthopaedic surgery: Reconstructive knee surgery. Ed 3. Philadelphia: Lippincott, Williams & Wilkins; 2008:71-88.
10. Ritchie JR, Miller MD, Bents RT, Smith DK. Meniscal repair inthe goat model. The use of healing adjuncts on central tears and the role of magnetic resonance arthrography in repair evaluation. Am J Sports Med. 1998;26:278–84.
11. Zhang Z, Arnold JA, Williams T, McCann B. Repairs by trephination and suturing of longitudinal injuries in the avascular area of the meniscus in goats. Am J Sports Med. 1995;23:35–41.
12. Fox JM, Rintz KG, Ferkel RD. Trephination of incomplete meniscal tears. Arthroscopy. 1993;9:451–5.
13. Ra HJ, Ha JK, Jang SH, Lee DW, Kim JG. Arthroscopic inside-out repair of complete radial tears of the meniscus with a fibrin clot. Knee Surg Sports Traumatol Arthrosc. 2013;21:2126–2130
14. Horibe S, Shino K, Maeda A, Nakamura N, Matsumoto N, Ochi T. Results of isolated meniscal repair evaluated by second-look arthroscopy. Arthroscopy. 1996;12(2):150-155
15. Choi NH, Kim TH, Victoroff BN. Comparison of arthroscopic medial meniscal suture repair techniques: Inside out versus all-inside repair. Am J Sports Med 2009;37:2144-2150.
16. Grant JA, Wilde J, Miller BS, Bedi A. Comparison of inside-out and all-inside techniques for the repair of isolated meniscal tears: A systematic review. Am J Sports Med 2012;40:459-468.


How to Cite this article:. Tapasvi SR, Anshu S,  Patil SS. Inside-Out Meniscus Repair – A Review. Asian Journal of Arthroscopy  Aug – Nov 2016;1(2):14-18.

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Meniscectomy-Outcomes and Complications

Shantanu Sudhakar Patil, Sachin Ramchandra Tapasvi, Anshu Shekhar

Volume 1 | Issue 2 | Aug – Nov 2016 | Page 53-55.


Author: Shantanu Sudhakar Patil[1], Sachin Ramchandra Tapasvi[1], Anshu Shekhar[1].

[1] The Orthopaedic Speciality Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004.

Address of Correspondence

Dr Sachin Ramchandra Tapasvi
The Orthopaedic Speciality Clinic, 16 Status Chambers, 1221/A Wrangler Paranjpe Road, Pune 411004
Email: stapasvi@gmail.com


Abstract

The menisci, once considered expendable remnants have been conclusively proven to be of extreme vitality in the biomechanics and biology of the knee joint. Though meniscus repair is being increasingly performed to preserve knee function, not all tears are amenable to repair and partial meniscectomy in such cases is an acceptable treatment option. The poor outcomes following partial meniscectomy are due to the shrinking of contact areas and rise in peak stresses. These changes and their consequences are more pronounced in the lateral compartment of the knee. Pre-existing chondral damage, instability and higher BMI compound the problem.
Key words: Meniscus, meniscectomy, meniscus repair, arthritis.


Introduction

The menisci of the knee joint are fibrocartilagenous semilunar tissues that perform a critical function of stabilising the joint and aiding in efficient load transfer as a shock absorber. Though once considered vestigial and hence disposable, the role of healthy menisci in delaying the normal attrition of the articular cartilage cannot be understated. Meniscectomy was thought to be a benign procedure and as late as 1975 [1] the importance of doing a complete removal was being reiterated. The functions of the meniscus were recognised much earlier [2] and eventually the potential harms of its excision were gaining attention. Meniscal tears are one of the commonest injuries of the knee, for which treatment is sought, with an incidence rate of 61 per 100000 population per year.[3] Most acute tears are commoner in younger patients, with the medial meniscus affected at a 2:1 ratio with the lateral side. The acute tears are described as per their orientation and extent along the meniscus. They are usually classified as vertical longitudinal, oblique, circumferential, complex, transverse or radial, and horizontal cleavage tears. Radial tears of the posteromedial compartment are the most frequently seen tears and vertical longitudinal tears are most often associated with acute ACL injury. Degenerative tears have a varied pattern and are complex in their morphology.[4]. The direction of the meniscus tears is explained by the orientation of collagen fibrils within the structure. The cross section of the meniscus reveals three distinct layers: a superficial thin layer on both tibial and femoral surfaces; a lamellar layer below this with the fibrils arranged in a radial manner and a main central region where the fibrils are orientated in a circular manner. The circular arrangement of the collagen bundles explains why majority of the tears have a longitudinal orientation. [5](Fig. 1). With our growing understanding of the anatomy , vasculature, biomechanics and the biology of the meniscus, and with improved arthroscopic techniques and instrumentation, the goal of management of meniscal tears has shifted towards achieving repair. However, not all tears are amenable to repair and at least a partial meniscectomy might be indicated to alleviate the patients symptoms. We will take a look at the outcomes and complications of arthroscopic meniscectomy in this article.

Sequelae of articular cartilage changes following Meniscectomy

The effects of meniscectomy on the stability and pressures inside the knee joint were studied using pressure sensitive films in cadavers. Medial meniscectomy caused the contact areas to shrink by almost 75% leading to more than twofold increase in peak contact pressures. [6] The articular cartilage responds unfavourably to the higher loads, with disruption of the proteoglycan matrix, causing swelling and inflammation throughout the joint. The heightened catabolic state with increased hydration leads to breakdown of the collagen matrix, thus accelerating the normal wear and tear within the joint.[7]

Radiological changes:
The radiological changes in the knee joint following medial meniscectomy are well documented.[8]Joint space narrowing, flattening of the marginal part of the medial femoral condyle and sclerosis of the articulating condyles is seen. These radiological signs were indicative of early osteoarthritic changes in the knee. Multiple clinical and radiological studies have documented these sequelae, but the correlation between the symptoms of the patient and severity of these changes is not always seen in the results. It is not easy to determine the correlations as many reports have studied the consequences after an open meniscectomy. Moreover, a meniscal tear rarely presents in isolation and the concomitant ligament or articular injuries play a role in subsequent degeneration and development of Osteoarthritis.

Partial Versus Total meniscectomy

With the advent of arthroscopic surgery and advances in instrumentation for the various surgical procedures, it was possible to resect only the offending parts of the torn meniscus. It is uncommon these days to perform a total resection, with partial meniscectomy being the more widely reported procedure. Once a meniscal tear is identified and deemed unsuitable for repair, a meniscectomy is the recommended surgical option. The basic principles for this were described by Metcalf. They are as follows: Remove all mobile fragments; Avoid sudden changes in rim contour; a perfectly smooth rim is unnecessary as some remodelling may occur; re-evaluate the tear often with a probe; Avoid damage to the meniscus-capsular junction to avoid the loss of hoop stresses; Use both manual and motorized instruments to maximize efficiency and when uncertain if an area should be resected, err on the side of leaving more meniscus intact rather than compromising biomechanical properties[9]. Salata in a meta-analysis showed the significantly higher risk of developing radiographic OA in the patients undergoing total meniscectomy as compared to the partial meniscectomy. [10] Though the patients with either partial or total meniscectomy report similar early clinical results, there was no significant difference in the radiographic outcomes at the final 7.8 years average follow-up[11]. Only 68% of the patients who had undergone a total meniscectomy and followed up for up to 30 years showed good or excellent results while at least 2/3rd had some post-operative symptoms.[12] There exists a direct correlation with the meniscal tissue left behind and peak contact stress on the tibial surfaces following partial resections[13]. A finite element study quantifying the amount of resected meniscus to peak pressures showed that with as little as 20% resection of meniscus, a detrimental increase of forces is seen which may hasten the osteoarthritic changes. Maximum shear stress in the articular cartilage is seen with 65% partial meniscectomy[14]. The orientation of collagen fibril bundles within the meniscus determines the development of hoop strains as they are axially loaded. A radial tear disrupts the continuity of the circularly oriented fibrils and thus prevents the hoop strains from forming, causing dysfunction of the meniscus. A horizontal or vertical tear will not disrupt this continuity, preserving the load-bearing and shock-bearing function of the meniscus.[15] This needs to be borne in mind while determining the extent of the meniscectomy. The medial and lateral tibio-femoral articulations are anatomically different and the absence of menisci which afford a degree of congruity can lead to increased point loading and higher contact pressures. This is more prominent on the lateral side where a convex lateral femoral condyle articulates on a flat or convex tibial plateau. This translates to poorer outcomes with lateral meniscectomy as compared to medial as reported in multiple studies. Patients with a lateral meniscectomy have a much higher functional deterioration and increased instability than the medial meniscectomy patients[11,3,16].

figure-1

Influence of other concomitant factors

The ACL-deficient knee with a meniscal tear has a significantly higher radiographic grade changes after meniscectomy as compared with ACL-intact knees.[17] Consequences of meniscectomy in an unstable knee are worsened by the combination of higher contact forces inducing early pathological changes due to the elevated shear stresses within the articular cartilage.[18] The presence of pre-existing chondral damage at the time of meniscectomy predisposes the knee to a significant increase in development of OA leading to poor clinical outcomes. However, contradicting findings have also been reported with there being no significant changes in knee functions and activity level following the meniscectomy. [19]. Chondral lesions can cause similar symptoms as that of a meniscal tear and meniscectomy may not fully alleviate the patients’ complaints, thus leading to poor outcomes. Degenerative tears are more often seen in older subjects with varus alignment. However, the evidence that meniscectomy in this group leads to higher rate of radiographic OA is not conclusive. These patients do show a decreased level of activity along with poorer outcomes based on subjective and functional measures following the surgery.[19, 20]While there is consensus about patients with increased BMI predisposing to a higher risk of OA post meniscectomy, the exact level of BMI that placed the patient at risk is not conclusive.[11], [21].

Complications

These can be classified as those related to knee arthroscopy in general and those associated specifically with arthroscopic partial meniscectomy. In the hands of an experienced arthroscopy surgeon, the complication rates were low. (1.78% and 1.48% for medial and lateral meniscectomy) [22], [23]. Some of the enumerated complications include instrument failure or breakage, injuries to nerves and blood vessels, accidental damage to chondral surfaces and ligament injury. Instrument failure rates have dropped from 18.1% to 2.9% over the years, due to improvement in surgical techniques, better designs as well as better skill levels of the surgeons[22]. The medial collateral ligament may get injured due to excessive valgus forces while attempting access to the medial compartment. Similarly, nerves and vessels may get damaged during insertion of sharp instruments. Improper and clumsy handling of instruments during the surgery can gouge the articular surface causing damage. Incomplete removal of the torn pieces can cause persistent pain along with coexistent knee pathology. Proper adherence to basic principles of partial meniscectomy can help avoid all these complications.

Conclusion

There exist a large number of studies which have studied the consequences of meniscectomy as a surgical procedure. Many of these have incomplete or inaccurate information along with varying heterogeneous criteria for evaluation of outcomes. The functional and clinical outcomes do not necessarily match the radiological outcomes in most of the studies. The multiple imaging modalities add to data which is not uniform for evaluation. This lack of homogenous data and lack of standardization of methodological issues, makes it difficult to conclude if the findings represent true differences or are simply artefact related to measurement bias or other errors. It is probably safe to conclude that a minimally invasive procedure with attention to sparing bulk of meniscal tissue seems to reduce the subsequent incidence of arthritic changes, as compared with open invasive and radical procedures..


References

1. Hughston, J.C., A simple meniscectomy. J Sports Med, 1975. 3(4): p. 179-87.
2. King, D., The healing of semilunar cartilages. 1936. Clin Orthop Relat Res, 1990(252): p. 4-7.
3. Jones, J.C., et al., Incidence and risk factors associated with meniscal injuries among active-duty US military service members. J Athl Train, 2012. 47(1): p. 67-73.
4. Pauli, C., et al., Macroscopic and histopathologic analysis of human knee menisci in aging and osteoarthritis. Osteoarthritis Cartilage, 2011. 19(9): p. 1132-41.
5. Petersen, W. and B. Tillmann, Collagenous fibril texture of the human knee joint menisci. Anat Embryol (Berl), 1998. 197(4): p. 317-24.
6. Baratz, M.E., F.H. Fu, and R. Mengato, Meniscal tears: the effect of meniscectomy and of repair on intraarticular contact areas and stress in the human knee. A preliminary report. Am J Sports Med, 1986. 14(4): p. 270-5.
7. Lanzer, W.L. and G. Komenda, Changes in articular cartilage after meniscectomy. Clin Orthop Relat Res, 1990(252): p. 41-8.
8. Fairbank, T.J., Knee joint changes after meniscectomy. J Bone Joint Surg Br, 1948. 30b(4): p. 664-70.
9. Metcalf, R.W., Arthroscopic meniscal surgery., in Operative Arthroscopy., M. JB, Editor. 1991, Raven Press: New York. p. pp. 203–236.
10. Salata, M.J., A.E. Gibbs, and J.K. Sekiya, A systematic review of clinical outcomes in patients undergoing meniscectomy. Am J Sports Med, 2010. 38(9): p. 1907-16.
11. Hede, A., E. Larsen, and H. Sandberg, Partial versus total meniscectomy. A prospective, randomised study with long-term follow-up. J Bone Joint Surg Br, 1992. 74(1): p. 118-21.
12. Tapper, E.M. and N.W. Hoover, Late results after meniscectomy. J Bone Joint Surg Am, 1969. 51(3): p. 517-26 passim.
13. Ihn, J.C., S.J. Kim, and I.H. Park, In vitro study of contact area and pressure distribution in the human knee after partial and total meniscectomy. Int Orthop, 1993. 17(4): p. 214-8.
14. Vadher, S.P., et al., Finite element modeling following partial meniscectomy: effect of various size of resection. Conf Proc IEEE Eng Med Biol Soc, 2006. 1: p. 2098-101.
15. Jones, R.S., et al., Direct measurement of hoop strains in the intact and torn human medial meniscus. Clin Biomech (Bristol, Avon), 1996. 11(5): p. 295-300.
16. Petty, C.A. and J.H. Lubowitz, Does arthroscopic partial meniscectomy always cause arthritis? Sports Med Arthrosc, 2012. 20(2): p. 58-61.
17. Burks, R.T., M.H. Metcalf, and R.W. Metcalf, Fifteen-year follow-up of arthroscopic partial meniscectomy. Arthroscopy, 1997. 13(6): p. 673-9.
18. McDermott, I.D. and A.A. Amis, The consequences of meniscectomy. J Bone Joint Surg Br, 2006. 88(12): p. 1549-56.
19. Rockborn, P. and J. Gillquist, Long-term results after arthroscopic meniscectomy. The role of preexisting cartilage fibrillation in a 13 year follow-up of 60 patients. Int J Sports Med, 1996. 17(8): p. 608-13.
20. Chatain, F., et al., The natural history of the knee following arthroscopic medial meniscectomy. Knee Surgery, Sports Traumatology, Arthroscopy, 2000. 9(1): p. 15-18.
21. Englund, M. and L.S. Lohmander, Risk factors for symptomatic knee osteoarthritis fifteen to twenty-two years after meniscectomy. Arthritis Rheum, 2004. 50(9): p. 2811-9.
22. Small, N.C., Complications in arthroscopic surgery performed by experienced arthroscopists. Arthroscopy, 1988. 4(3): p. 215-21.
23. Allum, R., Complications of arthroscopy of the knee. J Bone Joint Surg Br, 2002. 84(7): p. 937-45.
24. Papalia, R., et al., Meniscectomy as a risk factor for knee osteoarthritis: a systematic review. Br Med Bull, 2011. 99: p. 89-106.


How to Cite this article: Patil SS, Tapasvi SR, Shekhar A. Meniscectomy-Outcomes and Complications. Asian Journal of Arthroscopy  Aug – Nov 2016

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Menisci: Structure and Function

Ankit Chawla, Amite Pankaj Aggarwal

Volume 1 | Issue 2 | Aug – Nov 2016 | Page 3-7


Author: Ankit Chawla[1], Amite Pankaj Aggarwal[1]

[1] Unit of Joint Replacement, Arthroscopy and Orthopaedics, Fortis Hospital, Shalimar Bagh, New Delhi, India.

Address of Correspondence

Dr. Amite Pankaj Aggarwal
Fortis Hospital Shalimar Bagh
New Delhi, India.
Email: amitepankaj@gmail.com.


Abstract

Meniscal injuries are recognized as a cause of significant musculoskeletal morbidity. The menisci are vital for the normal function and long-term health of the knee joint. And loss of a meniscus increases the risk of subsequent development of degenerative changes in the knee. A review of anatomy and ultrastructure of the meniscus, and its relationship to normal function in terms of load transmission, shock absorption, joint stability, lubrication and nutrition is a necessary prerequisite to understanding pathologies associated with the knee.
Keywords: Meniscus, Medial meniscus, lateral meniscus, Anatomy, Function.


Introduction

The word meniscus comes from the Greek word me-niskos, meaning “crescent,” diminutive of me-ne-, meaning “moon.” The menisci are semilunar discs of fibrocartilaginous tissue which are vital for the normal biomechanics and long-term health of the knee joint [1]. The characteristic shape of the lateral and medial menisci is attained between the 8th and 10th week of gestation. They arise from a condensation of the intermediate layer of mesenchymal tissue to form attachments to the surrounding joint capsule[2,3].

Gross Anatomy
These crescent-shaped wedges of fibrocartilage are located on the medial and lateral aspects of the knee joint (Fig. 1A,1B). The peripheral, vascular border of each meniscus is thick, convex, and attached to the joint capsule. The innermost border tapers to a thin free edge. The superior surfaces of menisci are concave, enabling effective articulation with their respective convex femoral condyles. The inferior surfaces are flat to accommodate the tibial plateau [4,5].

Medial Meniscus
The medial meniscus is a C-shaped structure larger in radius than the lateral meniscus, with the posterior horn being wider than the anterior. The anterior horn is attached firmly to the tibia anterior to the intercondylar eminence and to the anterior cruciate ligament. The posterior horn is anchored immediately in front of the attachments of the posterior cruciate ligament posterior to the intercondylar eminence. Its entire peripheral border is firmly attached to the medial capsule and through the coronary ligament to the upper border of the tibia. At its midpoint, the medial meniscus is more firmly attached to the femur through a condensation in the joint capsule known as the deep medial collateral ligament [5]. The transverse, or “intermeniscal,” ligament is a fibrous band of tissue that connects the anterior horn of the medial meniscus to the anterior horn of the lateral meniscus [5,6].

Lateral Meniscus
The lateral meniscus is more circular in form, covering up to two thirds of the articular surface of the underlying tibial plateau [7]. The anterior horn is attached to the tibia medially in front of the intercondylar eminence, whereas the posterior horn inserts into the posterior aspect of the intercondylar eminence and in front of the posterior attachment of the medial meniscus. The lateral meniscus is loosely attached to the capsular ligament; however, these fibers do not attach to the lateral collateral ligament. The posterior horn of the lateral meniscus attaches to the inner aspect of the medial femoral condyle via the anterior and posterior meniscofemoral ligaments of Humphrey and Wrisberg, respectively, which originate near the origin of the PCL (Fig. 1A) [8]. Their estimated prevalence is 74 % for Humphrey ligament, 69 % for Wrisberg ligament, and both ligaments found together in around 50 % of knees [9]. The lateral meniscus is smaller in diameter, thicker in periphery, wider in body, and more mobile than the medial meniscus.

figure-1-and-2

Extracellular matrix and cellularity
Considering composition by wet weight, the meniscus has high water content (72 %). The remaining 28 % consists of an organic component, mostly ECM and cells.10 Collagens comprise the majority (75 %) of the organic matter, followed by GAGs (17 %), DNA (2 %), adhesion glycoproteins (<1 %), and elastin (<1 %) [10,11]. These proportions vary according to age, injury, or pathological conditions [12]. Collagen is the main fibrillar component of the meniscus. Different collagen types exist in various quantities in each region of meniscus. In the red–red zone, type I collagen is predominant (80 % composition in dry weight). In the white–white zone, 60 % is type II collagen and 40 % is type I collagen [13]. The major orientation of collagen fibers in the meniscus is circumferential; radial fibers and perforating fibers also are present.(Fig. 3) [13]. Proteoglycans are heavily glycosylated molecules that constitute a major component of the meniscus ECM [14]. These molecules are comprised of a core protein which is decorated with glycosaminoglycans (GAGs). The main types of GAGs found in normal human meniscal tissue are chondroitin 6 sulfate (60%), dermatan sulfate(20-30%), chondroitin 4 sulfate (10-20%), and keratin sulfate(15%) [15]. Their main function is to enable the meniscus to absorb water, whose confinement supports the tissue under compression [10]. Adhesion glycoproteins are also important components of the meniscus matrix, as they serve as a link between ECM components and cells [16]. The main adhesion glycoproteins present in the human meniscus are fibronectin, thrombospondin, and collagen VI [16,17]. Outer zone cells have an oval, fusiform shape and are similar in appearance and behaviour to fibroblasts, described as fibroblast-like cells [18]. The matrix surrounding the cells is mainly comprised of type I collagen, with small percentages of glycoproteins and collagen types III and V present. In contrast, cells in the inner portion have rounded appearance and are embedded in an ECM comprising largely type II collagen intermingled with a smaller but significant amount of type I collagen and higher concentration of GAGs [18]. This relative abundance of collagen type II and aggrecan in the inner region is more reminiscent of hyaline articular cartilage. Therefore, cells in this region are classified as fibrochondrocytes or chondrocyte like cells. In summary, cell phenotype and ECM composition render the outer portion of the meniscus akin to fibrocartilage, while the inner portion possesses similar, but not identical, traits to articular cartilage [19,20].

figure-3

Vascularity and Innervation
The vascular supply to the medial and lateral menisci originates predominantly from the lateral and medial geniculate vessels (both inferior and superior). Branches from these vessels give rise to a perimeniscal capillary plexus within the synovial and capsular tissue. (Fig. 2) Radial branches from the plexus enter the meniscus at intervals, with a richer supply to the anterior and posterior horns. Vessels supplying the body are limited to the meniscus periphery with a variable penetration of 10–30 % for medial meniscus and 10–25 % for lateral one. This has important implication for meniscal healing [21]. The remaining portion of each meniscus (65% to 75%) receives nourishment from synovial fluid via diffusion or mechanical pumping (ie, joint motion) [22, 23]. The knee joint is innervated by the posterior articular branch of the posterior tibial nerve and the terminal branches of the obturator and femoral nerves. The lateral portion of the capsule is innervated by the recurrent peroneal branch of the common peroneal nerve. These nerve fibers penetrate the capsule and follow the vascular supply to the peripheral portion of the menisci and the anterior and posterior horns, where most of the nerve fibers are concentrated. The inner menisci core has no nerve fibers [21].

Biomechanical Function
­­­The biomechanical function of the meniscus is a reflection of the gross and ultrastructural anatomy and of its relationship to the surrounding intra-articular and extra-articular structures. The meniscus withstands many different forces such as shear, tension, and compression. It also plays a crucial role in load-bearing, load transmission, shock absorption, stability, propioception as well as lubrication and nutrition of articular cartilage [24-27]. They also serve to decrease contact stresses and increase contact area and congruity of the knee [28,29].

Meniscal Biomechanics
The biomechanical properties of the knee meniscus are appropriately tuned to withstand the forces exerted on the tissue. Many studies have helped to quantify the properties of the tissue both in humans and in animal models. According to these studies, the meniscus resists axial compression with an aggregate modulus of 100-150 kPa [30]. The tensile modulus of the tissue varies between the circumferential and radial directions; it is approximately 100-300 MPa circumferentially and 10 fold lower than this radially [31]. Finally, the shear modulus of the meniscus is approximately 120 kPa [31]. The contact forces on the meniscus within the human knee joint have been mapped. It has been calculated that the intact menisci occupy approximately 60% of the contact area between the articular cartilage of the femoral condyles and the tibial plateau, while they transmit >50% of the total axial load applied in the joint [32,33]. However, these percentages are highly dependent on degree of knee flexion and tissue health. For every 30o of knee flexion, the contact surface between the two knee bones decreases by 4% [34]. When the knee is in 90o of flexion the applied axial load in the joint is 85% greater than when it is in 0o of flexion [33]. In full knee flexion, the lateral meniscus transmits 100% of the load in the lateral knee compartment, whereas the medial meniscus takes on approximately 50% of the medial load [29]. Studies confirm that there is a significant difference in segmental motion during flexion between the medial and lateral menisci. The anterior and posterior horn lateral meniscus ratio is smaller and indicates that the meniscus moves more as a single unit [35]. Alternatively, the medial meniscus (as a whole) moves less than the lateral meniscus, displaying a greater anterior to posterior horn differential excursion. Thompson et al found that the area of least meniscal motion is the posterior medial corner, where the meniscus is constrained by its attachment to the tibial plateau by the meniscotibial portion of the posterior oblique ligament, which has been reported to be more prone to injury [35,36]. A reduction in the motion of the posterior horn of the medial meniscus is a potential mechanism for meniscal tears, with a resultant “trapping” of the fibrocartilage between the femoral condyle and the tibial plateau during full flexion. The greater differential between anterior and posterior horn excursion may place the medial meniscus at a greater risk of injury [35]. The differential of anterior horn to posterior horn motion allows the menisci to assume a decreasing radius with flexion, which correlates to the decreased radius of curvature of the posterior femoral condyles [35]. This change of radius allows the meniscus to maintain contact with the articulating surface of both the femur and the tibia throughout flexion.

Load Transmission
Fairbank described the increased incidence and predictable degenerative changes of the articular surfaces in completely meniscectomized knees [37]. Weightbearing produces axial forces across the knee, which compress the menisci, resulting in “hoop” (circumferential) stresses [38]. Hoop stresses are generated as axial forces and converted to tensile stresses along the circumferential collagen fibers of the meniscus. Firm attachments by the anterior and posterior insertional ligaments prevent the meniscus from extruding peripherally during load bearing [39]. Medial meniscectomy decreases contact area by 50% to 70% and increases contact stress by 100%. Lateral meniscectomy decreases contact area by 40% to 50% but dramatically increases contact stress by 200% to 300% because of the relative convex surface of the lateral tibial plateau [40,41]. This significantly increases the load per unit area and may contribute to accelerated articular cartilage damage and degeneration [42].

Shock absorption
The menisci play a vital role in attenuating the intermittent shock waves generated by impulse loading of the knee with normal gait [43,44]. Voloshin and Wosk showed that the normal knee has a shock-absorbing capacity about 20% higher than knees that have undergone meniscectomy [38]. As the inability of a joint system to absorb shock has been implicated in the development of osteoarthritis, the meniscus would appear to play an important role in maintaining the health of the knee joint [45]

Joint stability
The geometric structure of the menisci provides an important role in maintaining joint congruity and stability. The superior surface of each meniscus is concave, enabling effective articulation between the convex femoral condyles and flat tibial plateau. When the meniscus is intact, axial loading of the knee has a multidirectional stabilizing function, limiting excess motion in all directions [46]. The studies for effects of meniscectomy on joint laxity for anteroposterior and varus-valgus motions and rotation have indicated indicated that the effect on joint laxity depends on whether the ligaments of the knee are intact and whether the joint is bearing weight. In the presence of intact ligamentous structures, excision of the menisci produces small increases in joint laxity. In an anterior cruciate ligament–deficient knee, medial meniscectomy has been shown to increase tibial translation by 58% at 90o, whereas primary anterior and posterior translations were not affected by lateral meniscectomy [47]. Shoemaker and Markolf demonstrated that the posterior horn of the medial meniscus is the most important structure resisting an anterior tibial force in the ACL-deficient knee. [48] Recently, Musahl et al reported that the lateral meniscus plays a role in anterior tibial translation during the pivot-shift maneuver [49].

Joint Nutrition and Lubrication
The menisci may also play a role in the nutrition and lubrication of the knee joint. The mechanics of this lubrication remains unknown; the menisci may compress synovial fluid into the articular cartilage, which reduces frictional forces during weightbearing [50]. There is a system of microcanals within the meniscus located close to the blood vessels, which communicates with the synovial cavity; these may provide fluid transport for nutrition and joint lubrication [51,52].

Conclusions
Mechanoreceptors have been identified in the anterior and posterior horns of the menisci, middle and outer third of the meniscus. The identification of these neural elements indicates that the menisci are capable of detecting proprioceptive information (joint motion and position) in the knee joint, thus playing an important afferent role in the sensory feedback mechanism of the knee [53,54].


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How to Cite this article:. Chawla A, Aggarwal AP. Menisci: Structure and Function. Asian Journal of Arthroscopy  Aug – Nov 2016;1(2):3-7 .

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