Repair of Acute Grade 3 Combined Posterolateral Corner Avulsion Injuries Using an Enhanced Fixation Technique

At a level 1 trauma center, the case log of a single surgeon (M.J.M.) was reviewed for patients who had MLKIs between the years of 2007 to 2018. Patients were retrospectively identified within the electronic medical record using Current Procedural Terminology (CPT) and International Classification of Disease (ICD) procedural codes. Coding for ICD included those that pertained to the management of lateral (fibular) collateral ligament (LCL) injury, and the following CPT code was utilized: 27427.

A total of 68 patients with MLKI treated surgically for a combined PLC injury were identified. All injuries were classified via the Schenck classification, and by definition, all patients had combined PLC and cruciate injuries. A grade 3 PLC injury was defined as a complete disruption of the LCL (complete midsubstance tear or avulsion) and a complete tear or avulsion of at least one of the following: biceps femoris tendon, popliteofibular ligament, or popliteus tendon.⁷ Inclusion criteria from this data set included any acute MLKI treated with surgical repair without graft augmentation of an avulsion-type grade 3 PLC injury without midsubstance tearing within 3 weeks of injury. This was done by reviewing the operative records for each patient, with a review of the magnetic resonance imaging (MRI) scan to confirm presence of a grade 3 PLC avulsion injury. All injuries were initially identified by a board-certified musculoskeletal radiologist on MRI, which was then reviewed by a board-certified orthopaedic sports medicine surgeon (M.J.M.). Ligament injuries of the PLC were categorized according to the classification described by Kahan et al.⁷ For a given MRI scan, if a discrepancy existed, or documentation was unclear, the operative description of the injury was used for the definitive diagnosis. This identified 28 patients who sustained a MLKI with a grade 3 PLC avulsion injury. Exclusion criteria included additional, unrelated simultaneous knee surgery (n = 0), prior ipsilateral knee surgery (n = 0), follow-up of <2 years (n = 4), or missing patient-reported outcome data (n = 3).

The indications for performing the same uniform acute PLC repair technique in this study included the following: (1) <3 weeks from initial injury; (2) only avulsion-type injury; and (3) no evidence of midsubstance injury on MRI nor on intraoperative assessment. In contrast, patients with MRI and/or intraoperative evidence of midsubstance tearing, and those with chronic injuries, were considered potentially irreparable and were treated with a PLC reconstruction. Patients with evidence of both avulsion and midsubstance injuries were treated with combined repair and graft augmentation and were excluded from the study cohort. The extent and location of injury was recorded intraoperatively, and procedural technicalities were well-documented by the senior author, a board-certified orthopaedic sports medicine surgeon with over 20 years of experience (M.J.M.). Repair failure was defined as any of the following: (1) subsequent or revision or salvage surgery on the ipsilateral knee; (2) comparative lateral joint-space widening ≥4 mm with subjective clinical varus stress; or (3) documentation noting both subjective and objective varus instability.

Findings from the preoperative physical examination and subsequent follow-up were collected, including varus instability at 30° of flexion with manual estimated lateral compartment opening measurements (0, 3, 6, 9, 12, or 15 mm). When present, peroneal nerve injuries were defined as a deficit in at least one of the following measures: tibialis anterior or extensor hallucis longus strength or peroneal nerve distribution sensory deficits.

This study demonstrates that timely acute repair of grade 3 combined PLC avulsion-type injuries in select patients can result in significantly lower failure rates (10.7%) than reported for PLC injuries in general, regardless of how the cruciate injury is addressed. Furthermore, patients who underwent PLC repair with a staged bi-cruciate reconstruction had significantly higher subjective PROMs than patients with PLC repairs who had untreated bi-cruciate injuries. In addition, the presence of a peroneal nerve injury was associated with significantly worse PROMs compared to those without a nerve injury. In this series, there was an acceptable failure rate for acute repair of grade 3 combined PLC injuries at an average of 7 years of follow-up (range, 9 months to 10.6 years), suggesting that acute repair may result in a satisfactory outcome in carefully selected patients.

The current literature available is suggestive of reconstruction providing lower failure rates in comparison to repair for acute grade 3 PLC injuries. In one of the largest studies, Stannard et al²¹ reported a 37% (13 of 35) repair failure rate compared to 9% (2 of 22) for the reconstruction failure rate. Similarly, Levy et al¹⁵ described a 40% (4 of 10) repair failure rate compared to a 6% reconstruction failure rate in their cohort. Both of these study populations consisted of a majority of patients who underwent a staged cruciate or bi-cruciate reconstruction after their PLC repair as treatment for their MLKI. These reports of repair outcomes, in contrast to our study, were not restricted to a collection of patients who underwent a relatively uniform procedure for a similar pattern of injury and lacked a detailed description of the repair technique. Despite their utility, these studies still have limitations in power, follow-up, and/or repair techniques.^10,15,21 Our study demonstrated a significantly lower rate of failure (10.7%) in patients with acute repair of combined PLC avulsion type injuries than the repair failure rates of 37% to 40% that have been suggested.^6,15,21 It is important to note that all of the 3 patients who met the definition of failure (>4 mm lateral joint laxity on clinical exam and/or underwent subsequent revisional surgery) had a cruciate injury(s) that was not reconstructed, which could have contributed to the persistent laxity on physical exam that defined 2 out the 3 failures. While the ACL and PCL are secondary stabilizers to varus stress and external rotation and untreated injuries can stress the repaired PLC, it is important to note that 2 of the patients had complete peroneal nerve palsies with a foot drop, and the third had severe knee osteoarthritis before her injury that precluded bi-cruciate reconstruction. Each patient had several risk factors to impart undue stress on their repair, and it is also important to consider whether a combined PLC and cruciate reconstruction would have fared better in these clinical scenarios. Likely, it is a confluence of a few factors that contributed to the failures reported in this study.

The assessment and repair technique were conducted on a relatively uniform group of patients with similar avulsion-type injuries (without any evidence of midsubstance injury). Heterogeneous techniques for PLC repair in isolated and combined cases are reported throughout the literature, making these difficult to interpret findings outside of the technique used.^5,6,17,19,21 These techniques include “en masse surgical repairs” of the avulsed posterolateral structures with staple fixation to the tibia,¹⁹ direct repair of LCL and popliteus tendon avulsions with suture anchors,¹⁵ direct repair of biceps femoris tendon avulsions with fibular head bone tunnels,^4,5 and internal screw fixation of fibular head avulsions.²¹ In the present study, the same uniform technique was applied for every repair performed. This consisted of multiple locking Krackow sutures placed in the biceps and LCL, which were passed through remaining intact fibula and tibia, then fixed on the anteromedial tibial cortex. This repair technique has been conducted by the senior author for over 20 years and the reported findings from this study serve as outcome data for this technique.

It is also important to denote the potential mode of failure for this technique. While the reported failure rate (10.7%) and persistent clinical laxity in the 2 patients who did not undergo cruciate reconstruction may provide important information, it is difficult to determine the technical mode of repair failure, as these patients had untreated cruciate injuries and did not undergo a subsequent revision PLC procedure. Stannard et al²¹ reported that most repairs in their series failed from subsequent tendinous or midsubstance ligamentous tearing, which was attributed to inadequate soft tissue quality of the repaired structure. Contrary to the findings of Stannard et al, Levy et al reported no correlation between the site of injury and failure; however, this was based on an assessment of only 4 failures, some of which involved anchor failure¹⁵. The technique described in the current study potentially offers several potential biomechanical advantages against several modes of failure. First, there is added suture security acquired placing the fixation over the dense anterior tibial cortical bone, in comparison to fibular fixation alone. This potentially confers a decreased likelihood of suture or anchor pull-out through bone, which is especially important when dealing with PLC injuries with fragile fibular bone or in situations involving fibular head fractures or arcuate fractures.^5,6 Second, the use of multiple Krackow sutures may potentially have also conferred some degree of protection against suture pull-out from the soft tissue; however, this cannot be concluded from the results of our study. Future studies would be needed to validate the possible biomechanical benefits of this fixation technique. Another potential explanation for the lower failure rate could be the meticulous evaluation of soft tissue quality of the non-avulsed portion of each structure to identify any midsubstance tearing, before proceeding with a repair.

Results with regard to PROMs were modest, with a mean IKDC score of 73.4 ± 24.0 and 55% of patients reaching an IKDC score of ≥75. While these scores seem to fall within a similar range as those reported for PLC reconstruction within the literature,⁵ our patients who sustained a peroneal nerve injury from the initial trauma had worse IKDC and Tegner scores compared to those without peroneal nerve injury. This discrepancy is likely the result of the disability associated with the peroneal nerve injury rather than a reflection of the PLC repair. Prior studies have demonstrated poor functional recovery in patients with a complete peroneal nerve palsy in the setting of an MLKI.^1,7,18 In our study, 1 patient developed a complete peroneal nerve palsy with no recovery at the 3-year follow-up. This patient used an ankle foot orthosis and declined any additional surgical intervention such as tendon transfers to address the foot drop. There were 3 patients with partial peroneal nerve palsies, all reporting a subjective degree of improvement or full improvement in function and/or sensation at the 2-year follow-up. Currently, there are limited outcome data on patients treated for acute PLC repair with concomitant peroneal nerve palsy. When other injury characteristics were assessed, there were no differences in PROMs for comparing patients with and without associated fractures, vascular injury, and knee dislocations.

Repair of acute grade 3 combined PLC avulsion injuries using a transosseous Krackow suture pull-through technique demonstrated a failure rate of 10.7%. Patients who underwent a staged cruciate reconstruction(s) had higher subjective outcome scores than those who had cruciate injuries left untreated. Peroneal nerve injury was associated with lower outcome scores. Surgical repair of PLC avulsion injuries using the proposed technique is best utilized acutely and in those without evidence of midsubstance injuries.