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The structure of the femoral ACL enthesis is complex and a major determinant of ACL function. The variation in its structure suggests that its function may be developmentally determined. An understanding of its complex structure has implications for normal ACL function and the challenges of ACL reconstruction
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Biomechanically sound beats pseudo-anatomic MCL reconstruction
Andy Williams, Fortius Clinic / Imperial College, London, UK
At the 2022 Herodicus Society meeting I presented: ‘Time to stop pretending ligament reconstructions are ‘anatomic’! Better to be honest- biomechanically sound beats ‘pseudo-anatomic’.’ The 2024 presentation summarises work from Imperial College and my almost exclusively pro-sport practice supporting the philosophy presented in 2022 for MCL reconstruction.
Our anatomy study findings differ from commonly held views- eg the superficial MCL (sMCL) attaches the center of the medial femoral epicondyle and not posterior to it as is often popularised, and the deep MCL (dMCL) is an oblique structure passing anterodistal from posterior and distal to the sMCL femoral attachment fanning out to a relatively wide tibial attachment, and not just a short ligament parallel and deep to the sMCL (1).
Furthermore, our biomechanics studies (2,3) show the dMCL is a very important structure. The dMCL is the primary restraint to ER in 0-30? and then load shares with sMCL into deeper flexion. The posterior oblique ligament (POL) only provides restraint to internal rotation close to full extension and is only rarely of importance. These study findings account for the isolated dMCL lesions in soccer players having ER injury (4), and frequent injury to dMCL associated with ACL rupture (5), as well as having implications for MCL reconstruction.
Regarding MCL reconstruction, popular ‘anatomic’ techniques are sometimes fundamentally flawed. Typically, they include grafts to reproduce the sMCL and POL. All but one (6) never include a dMCL component. Biomechanical studies of them justifying their use can be unsound- one of the most popular (7) showed its sMCL graft controlled not only valgus but also ER, despite having no dMCL component- the results of the lab study reflect the fact that in the specimens tested the native dMCL was not cut before nor after sMCL reconstruction- no wonder it seemed to control ER when the primary restraint to ER remained intact! Testing this popular technique in cadavers with MCL division including cutting the dMCL shows the technique does not control ER at all (8). Adding a dMCL component restores ER control in our studies (8,9,10).
Finally, with regard to MCL reconstruction, cadaveric study (10) data showing excellent results justify a non-anatomic short isometric construct MCL reconstruction (11) to protect anatomy restoration by suture techniques, repairing torn structures in acute injuries and re-tensioning of the components of the MCL in chronic cases. This technique is easy and reproducible and rarely requires additional POL. To make it even more controversial a polyester graft is used! Nevertheless, good clinical outcomes data in elite athletes supports this technique’s efficacy and safety (12).
The POL is grossly overrated! The only indication for its reconstruction is in cases of PCL + MCL injury to control posteromedial rotatory instability, or excess hyperextension associated with MCL injury. Reconstructing the POL as part of an MCL reconstruction with concomitant ACL reconstruction in anteromedial rotatory instability is not easy, and is pointless in most cases, as well as illogical! The POL is aligned in the opposite direction to the ACL, whereas the dMCL is parallel to it. Since persisting, and even minor, MCL laxity increases ACL graft re-rupture (13, 14, 15), the need to add MCL reconstruction to ACL reconstruction will likely be more frequent (16) and rather analogous to additional anterolateral procedures. Unlike making the decision to add lateral tenodesis to ACL reconstruction which is somewhat arbitrary, there are very clear clinical signs and MRI appearances which are indications for MCL reconstruction to protect ACL grafts.
References:
1 Athwal KK, Willinger L, Shinohara S, et al. The bone attachments of the medial collateral and posterior oblique ligaments are defined anatomically and radiographically. Knee Surg Sports Traumatol Arthrosc. 2020;28(12):3709-3719.
2 Willinger L, Shinohara S, Athwal KK, Ball S, Williams A, Amis AA. Length change patterns of the medial collateral ligament and posterior oblique ligament in relation to their function and surgery Knee Surg, Sports Traumatol, Arthrosc 2020;28:3720-3732.
3 Ball S, Stephen JM, El-Daou H, Williams A, Amis AA. The medial ligaments and the ACL restrain anteromedial laxity of the knee. Knee Surg Sports Traumatol Arthrosc. 2020;28(12):3700-3708.
4 Narvani A, Mahmud T, Lavelle J, Williams A. Injury to the proximal deep medial collateral ligament: a problematical subgroup of injuries. J Bone Jt Surg (Br) 2010;92:949-953.
5 Willinger L, Balendra G, Pai V, et al. High incidence of superficial and deep medial collateral ligament injuries in 'isolated' anterior cruciate ligament ruptures: a long overlooked injury. Knee Surg Sports Traumatol Arthrosc. 2022;30(1):167-175.
6 Kim MS, Koh IJ, In Y. Superficial and deep medial collateral ligament reconstruction for chronic medial instability of the knee. Arthrosc Tech. 2019;8(6):e549-e554.
7 LaPrade RF, Wijdicks CA. Surgical technique: development of an anatomic medial knee reconstruction. Clin Orthop Relat Res. 2012;470(3):806-814
8 Miyaji N, Holthof SR, Bastos RPS, et al. A Triple-Strand Anatomic Medial Collateral Ligament Reconstruction Restores Knee Stability More Completely Than a Double-Strand Reconstruction: A Biomechanical Study In Vitro. Am J Sports Med. 2022;50(7):1832-1842.
9 Miyaji N, Holthof SR, Ball SV, Williams A, Amis AA. Medial collateral ligament reconstruction for anteromedial instability of the knee: a biomechanical study in vitro. Am J Sports Med 2022;50:1823-1831.
10 Jobe Shatrov, Petra Bonacic-Bartolin, Sander R Holthof, Andy Williams, Simon V Ball, and Andrew A Amis. A Comparative Biomechanical Study of Alternative Medial Collateral Ligament Reconstruction Techniques. Am J Sp Med 2024 – in press
11 Borque KA, Ball S, Sij E, et al. A ‘short isometric construct’ reconstruction technique for the medial collateral ligament of the knee. Arthrosc Tech 2023;12(2):e167-e171.
12 Borque KA, Jones M, Balendra G, Willinger L, et al. High return to play rate following treatment of multiple-ligament knee injuries in 118 elite athletes.
Knee Surg Sports Traumatol Arthrosc 2022; 30(10):3393-3401.
13 Ahn JH, Lee SH. Risk factors for knee instability after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2016;24(9):2936-2942.
14 Alm L, Krause M, Frosch KH, Akoto R. Preoperative medial knee instability is an underestimated risk factor for failure of revision ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2020;28(8):2458-2467.
15 Svantesson E, Hamrin Senorski E, Alentorn-Geli E, et al. Increased risk of ACL revision with non-surgical treatment of a concomitant medial collateral ligament injury: a study on 19,457 patients from the Swedish National Knee Ligament Registry. Knee Surg Sports Traumatol Arthrosc. 2019;27(8):2450-2459.
16 Williams A, Becker R, Amis AA. The medial collateral ligament: the neglected ligament. Knee Surg Sports Traumatol Arthrosc 2020;28:3698–3699.
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