September 2024

Anterior Cruciate Ligament Repair Bears Consideration

By: Theodore Shybut, M.D., FAANA

Member, AANA Communications and Technology Committee

 

Anterior Cruciate Ligament (ACL) repair, as opposed to reconstruction, has emerged as a viable treatment for a subset of ACL-injured patients. Primary repair offers potential advantages compared to reconstruction including: avoidance of autograft harvest site morbidity, native bone preservation, faster healing, accelerated rehabilitation, faster return to sport, closer restoration of native ACL micro-architecture and fiber orientation (“bundles”) and potential proprioceptive benefits due to preservation of innervation. In the case of recurrent tear, revision from a repair is technically simpler than in the setting of prior reconstruction. Potential for quicker healing, return to work and return to sport can decrease the socioeconomic burden of ACL surgery.1 In North America, the two most common modes of repair are direct repair for proximal tears and a scaffold technique which utilizes a peripheral blood seeded collagen implant which “bridges” the ACL stump to the lateral wall of the femoral notch.

 

Direct repairs can be accomplished with cortical suspensory fixation or suture anchors. These techniques are best utilized in the setting of proximal (Sherman 1) ACL tears and rely on the ability to reduce the avulsed ACL back to its origin on the lateral wall. This can be assessed intra-operatively with a “Figure 4 test.” One technique involves high tensile strength suture passed through the ACL, tensioned and affixed to the femur using a femoral cortical button, with an accompanying internal brace tape suture affixed on both the femoral and tibial sides.2 The most recent iteration of this technique incorporates adjustable closed loop fixation for the repair sutures. Other surgeons have reported a suture anchor-based repair, which has been similarly updated to accommodate a bracing tape alongside the ligament repair.3 Other suspensory and anchor-based technique variations have been described.

 

The biomechanical performance of direct repair techniques has been studied. Adjustable closed loop fixation with preconditioning was reported to improve time zero ACL tensioning and minimized gap formation compared to both single suture knotted closed loop on button construct and a suture anchor based repair construct.4 Adding an internal brace suture reduced peak loads on the repaired ACL and restricted gap formation.5 Another study reported that adjustable closed loop femoral cortical button repairs, independent bundle suture anchor based repairs, and bone patellar tendon bone autograft reconstruction all restored native anteroposterior and rotational laxity, and there were not find significant differences between the groups.6

 

Multiple case series limited to proximal repairs have shown encouraging short-term results with relatively low rates of revision surgery. For example, an in-press prospective study comparing patients who underwent tape suture augmented direct repair for Sherman 1 tears within 8 weeks of injury to both acute and nonacute ACL reconstruction patients found similar KT-1000 stability, patient-reported outcomes (PROs), range of motion and re-tear rates at two year followup.7 Another recent study retrospectively comparing prospectively collected outcomes on 20 proximal repairs to 20 reconstructions also found no significant differences in PROs or patients achieving quadriceps strength criteria, while repair patients had a greater rate of achieving hamstring strength criteria and underwent return to sport testing significantly earlier at 8.2 +/- 2.8 versus 10.6 +/- 1.4 months.8 However, a systematic review that included a focused analysis on ACL repair studies for proximal tears only found that in 11 studies published from 2006-2018 that rates of revision surgery were as high as 12.9% and reoperation rates as high as 18.2%.9 Of note, a number of those studies were done in Europe using dynamic intraligamentary stabilization (DIS). The best direct repair candidates appear to be adults (>25 years old) who are not involved in high-level athletics with acute proximal tears that retain a high-quality tissue remnant on the tibial side.

 

Both proximal and mid-substance ruptures can be treated when a scaffold is utilized in the repair. Utilization of a scaffold requires a relatively acute tear to harness the accompanying cellular migration and vascular proliferation and a sufficient tibial stump for suture purchase. A collagen scaffold seeded with autologous blood is guided via arthrotomy over sutures into the defect between the tibial stump of the ACL and the origin on the lateral wall of the femoral notch. This technique also incorporates sutures spanning the femur to the tibia affixed to cortical buttons.10 As with direct repair, surgeons have developed variants of the original technique employing suture anchors instead of cortical buttons, adjustable closed loop suture for the ACL stump, different sutures for the collagen scaffold and different spanning sutures and/or tapes for the spanning material. The team behind the most-studied scaffold-based technique has reported extensively on their experience, from preclinical and an early clinical feasibility cohort to two-year outcomes of a randomized prospective trial comparing scaffold-based repair to ACL reconstructions, primarily with four-stranded semitendinosis gracilis autograft. Important findings from this trial include earlier resolution of knee symptoms and increased patient satisfaction in the repair group, with no significant difference in time for medical clearance for return to sport or patient-reported outcomes at two years. The reinjury rate requiring revision ACL surgery was 14% in the repair group compared to 6% in the reconstruction group.11 Further clinical trials are ongoing, including a hotly anticipated comparison of scaffold repair to bone patella tendon bone autograft reconstruction.

 

Postoperative rehabilitation is a critical element in the outcome following ACL surgery. An evidence-based postoperative rehabilitation protocol has been developed for direct repair.12 However, some studies have utilized standard reconstruction protocols to avoid variation between study groups. Rehabilitation following scaffold-based repair is inherently slower in the early postoperative period as the clot connecting the ACL stump to the femur is relatively fragile in comparison to a tendon graft. The knee is typically locked in extension for 24 hours and only partial weight bearing and limited motion are allowed, with gradual progressions to protect healing across the scaffold then tissue maturation.13

 

Despite the wave of enthusiasm, older studies using varied ACL repair techniques have been reported to show relatively high failure rates, relatively high rates of other complications or subsequent surgery or decreases in activity level postoperatively. A 2019 systematic review concluded that “The literature on clinical outcomes of primary arthroscopic ACL repair is limited. The reported rates of repair failure and reoperation are highly inconsistent. Most studies report relatively high failure rates.”14 Another 2019 systematic review concluded that ACL reconstruction resulted in better survivorship and patient perceived postoperative improvement compared with ACL repair and suggested that reconstruction remains the treatment of choice for most cases.9 Therefore, there remains a need for better data on direct repairs, specifically larger scale prospective research comparing contemporary techniques for proximal tears with excellent remnant tissue to autograft reconstruction. Outcomes specific to athlete populations need to be more thoroughly investigated, as do a number of other variables such as effect of concurrent pathology/concurrent surgery at the time of ACL surgery, the role of lateral extra-articular augmentation with repair and so on.

 

To date my experience with carefully indicated repair has been quite positive. Thus, I consider repair when I see ACL-injured patients, just as I routinely measure tibial slope, and consider whether or not a lateral-sided augmentation may be indicated. As with these other surgical considerations, repair is not yet for every ACL-injured patient, but it has served my carefully indicated patients quite well thus far, and so I think warrants inclusion in the surgical discussion when appropriate, with the caveat that a graft-based reconstruction may still be performed pending operative findings. Autograft reconstruction remains the gold standard for anterolateral rotatory instability of the ACL-injured athlete’s knee. However, a growing body of contemporary literature supports the concept that repair can be a viable treatment strategy in carefully selected patients as there is evidence suggesting the repaired ACL can heal and stabilize the knee. Concern remains about variability in published failure rates, and the need for longer term follow-up in larger repair cohorts. In time, additional factors may be identified as important relative indications for choosing direct repair, scaffold augmented repair, repair augmented reconstruction or reconstruction alone to treat ACL-injured patients. Surgeons must pay close attention to indications and patient selection, implants and fixation techniques and follow ongoing research to help counsel ACL-injured patients regarding their treatment options.

 

References:

  1. Heusdens, C.H.W. ACL Repair: A Game Changer or Will History Repeat Itself? A Critical Appraisal. Journal of Clinical Medicine. 2021;10(5):912.
  2. Heusdens, C.H.W., Hopper, G.P., Dossche, L., Mackay, G.M.M. Anterior Cruciate Ligament Repair Using Independent Suture Tape Reinforcement. Arthroscopy Techniques. 2018;7(7):e737-e753.
  3. van der List, J.P., DiFelice, G.P. Arthroscopic Primary Anterior Cruciate Ligament Repair With Suture Augmentation. Arthroscopy Techniques. 2017;6(5):e1529-e1534.
  4. Bachmaier, S., DiFelice, G.S., Sonnery-Cottet, B., Douoguih, W.A., Smith, P.A., Pace, L.J., Ritter, D., Wijdicks, C.A. Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 1: Gap Formation and Stabilization Potential of Repair Techniques. Orthopaedic Journal of Sports Medicine. 2020;8(1):2325967119897421.
  5. Bachmaier, S., DiFelice, G.S., Sonnery-Cottet, B., Douoguih, W.A., Smith, P.A., Pace, L.J., Ritter, D., Wijdicks, C.A. Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 2: The Role of Internal Bracing on Gap Formation and Stabilization of Repair Techniques. Orthopaedic Journal of Sports Medicine. 2020;8(1):2325967119897423.
  6. Meunch, L.N., Berthold, D.P., Archambault, S., Slater, M., Mehl, J., Obopilwe, E., Cote, M.P., Arciero, R.A., Chahla, J., Pace, J.L. Anterior Cruciate Ligament (ACL) Repair Suing Cortical Or Anchor Fixation With Suture Tape Augmentation vs ACL Reconstruction: A Comparative Biomechanical Analysis. Knee. 2022;34:76-88.
  7. Simard, S.G., Greenfield, C.J., Khoury, A.N. ACL Repair With Suture Tape Augmentation of Proximal Tears and Early ACL Reconstruction With Suture Tape Augmentation Result in Comparable Clinical Outcomes to ACL Reconstruction at 2-Year Follow-Up. Arthroscopy. E pub July 26, 2024 org/10.1016/j.arthro.2024.07.021
  8. Duong, J.K.H., Bolton, C., Murphy, G.T., Fritsch, B.A. Anterior Cruciate Ligament Repair Versus Reconstruction: A Clinical, MRI and Patient-Reported Outcome Comparison. Knee. 2023;45:100-109.
  9. Nwachukwu, B.U., Patel, B.H., Lu, Y., Allen, A.A., Williams, R.J. Anterior Cruciate Ligament Repair Outcomes: An Updated Systematic Review of Recent Literature. Arthroscopy. 2019;35(7):2233-2247.
  10. Murray, M.M., Flutie, B.M., Kalish, L.A., et al. The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study. Orthopaedic Journal of Sports Medicine. 2016;4(11):2325967116672176.
  11. Murray, M.M., Fleming, B.C., Badger, G.J., et al. Bridge Enhanced Anterior Cruciate Ligament Repair is Not Inferior to Autograft Anterior Cruciate Ligament Reconstruction at 2 Years: Results of a Prospective Randomized Clinical Trial. American Journal of Sports Medicine. 2020;48(6):1305-1315.
  12. Irfran, A., Kerr, S., Hopper, G., Wilson, W., Wilson, L., Mackay, G.M. A Criterion Based Rehabilitation Protocol for ACL Repair With Internal Brace Augmentation. International Journal of Sports Physical Therapy. 2021;16(3):870-878.
  13. BEAR® Implant Rehabilitation Protocol. Miach Ortho. https://miachortho.com/healthcare-professionals/rehabilitation-protocol/_PDFs/ML-1014%20Rev%20H%20BEAR%20Rehab%20Protocol.pdf
  14. Houck, D.M., Kraeutler, M.J., Belk, J.K., Goode, J.A., Mulcahey, M.K., Bravman, J.T. Primary Arthroscopic Repair of the Anterior Cruciate Ligament: A Systematic Review of Clinical Outcomes. Arthroscopy. 2019;35(12):3318-3327.
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