Fifty shades of knee instability: a commentary on “Repair of intraoperative injury to the medial collateral ligament during primary total knee arthroplasty”

Instability following total knee arthroplasty (TKA) can be the source of residual pain, swelling, and is a leading cause for early revision following knee replacement surgery (1). While the true definition and causes for instability are not well defined, intraoperative injury to the medial collateral ligament (MCL) without proper management can result in dysfunction and dissatisfaction following TKA.

Injury to the MCL during primary TKA is not uncommon with reported incidences ranging from 1.2% to 2.7% (2). The ligament can either be avulsed from the femoral or tibial insertions or injured by a stray saw in its mid-substance. While there is agreement that recognition and treatment to minimize instability are critical for successful outcome, there is no consensus or guidelines to the best practice to managing these injuries should they occur.

Options for treatment include: (I) repair; (II) constrain; and/or (III) increase the polyethylene thickness to tighten the flexion gap. All these techniques have been reported successful in the literature (2). However, the degree of intervention maybe dependent on the location and severity of the ligament injury and prosthesis design. While primary repair of the MCL during cruciate retaining (CR) TKA has been shown to yield satisfactory results (3), there is controversy with regards to the management of the injured collateral during a posterior cruciate substituting (PS) TKA. Institutionally, we reported on a series of 37 intraoperative MCL injuries (1,650 knees) undergoing PS TKA and found that attempts at ligament repair resulted in high failure rates (2). Based on these findings, we concluded that MCL injuries in the setting of a PS knee design should be managed by increasing prosthesis constraint. However, others have not found constraint to be absolutely necessary to insure a good clinical outcome. Koo and Choi reported successful treatment of MCL avulsions by simply increasing the thickness of the polyethylene insert without high revision rates (4). Finally, Bohl et al. also reported successful treatment of MCL disruptions in PS knees treated with primary repair without increasing prosthetic constraint (5). With so many options, so what is one to do?

The reliability of increasing prosthetic constraint should be balanced against the possibility of increased wear and loosening. However, whether the ligament is injured or not during TKA, the achievement of a balanced flexion and extension gap remains a principal goal. How this is accomplished depends on surgical technique, experience and most importantly, governed by the concept that no compromises should be made with regards knee stability with hopes of subsequent ligament healing or tightening. This concept is illustrated by Siqueira et al. who evaluated a series of MCL disruptions during TKA treated with various methods and found that clinical outcomes did not differ so long as intraoperative stability could be achieved (6).

In summary, intraoperative MCL injury during TKA is not uncommon and failure to recognize and appropriately manage it can result in postoperative instability. The degree of laxity following ligament injury can be variable and successful outcomes can be achieved with primary repair, increasing polyethylene thickness, and/or increasing prosthetic constraint so long as balanced flexion and extension gaps can be achieved without compromises.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned and reviewed by the Executive Editor-in-Chief, Dongquan Shi, MD, PhD (Department of Sports Medicine and Adult Reconstruction, Drum Tower Hospital, Medical School, Nanjing University, Nanjing, China).

Conflicts of Interest: The author has completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/aoj.2016.07.03). The author has no conflicts of interest to declare.

Ethical Statement: The author is accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Sharkey PF, Lichstein PM, Shen C, et al. Why are total knee arthroplasties failing today--has anything changed after 10 years? J Arthroplasty 2014;29:1774-8. [Crossref] [PubMed]
2. Lee GC, Lotke PA. Management of intraoperative medial collateral ligament injury during TKA. Clin Orthop Relat Res 2011;469:64-8. [Crossref] [PubMed]
3. Leopold SS, McStay C, Klafeta K, et al. Primary repair of intraoperative disruption of the medical collateral ligament during total knee arthroplasty. J Bone Joint Surg Am 2001;83-A:86-91. [PubMed]
4. Koo MH, Choi CH. Conservative treatment for the intraoperative detachment of medial collateral ligament from the tibial attachment site during primary total knee arthroplasty. J Arthroplasty 2009;24:1249-53. [Crossref] [PubMed]
5. Bohl DD, Wetters NG, Del Gaizo DJ, et al. Repair of Intraoperative Injury to the Medial Collateral Ligament During Primary Total Knee Arthroplasty. J Bone Joint Surg Am 2016;98:35-9. [Crossref] [PubMed]
6. Siqueira MB, Haller K, Mulder A, et al. Outcomes of Medial Collateral Ligament Injuries during Total Knee Arthroplasty. J Knee Surg 2016;29:68-73. [Crossref] [PubMed]