Summary

In the setting of grade III PCL injury there is a high incidence of concomitant popliteus injury that is commonly missed on imaging and evaluation, and thus clinicians must have an understanding of this known injury pattern.

Abstract

Background

Historically, posterior cruciate ligament (PCL) grade I and II injuries have been treated non-operatively with good functional results, while the treatment of grade III PCL injuries is more controversial. It has been reported that the majority of PCL injuries undergoing operative management have concomitant ligament injuries. The popliteus and PCL act in synergy to prevent external rotation and posterior translation of the tibia. The most common cause of PCL failure is unrecognized associated PLC injury due to increased forces placed on the PCL. The PLC injuries commonly discussed are LCL or lateral structures but do not specify which structures are being repaired or reconstructed. The aim of this study is to highlight the management of grade III PCL injuries with a new novel description called the PCL plus, which is a PCL and concomitant popliteus injury. We hypothesize that an isolated grade III PCL injury may not frequently exist, rather an undiagnosed and untreated concurrent popliteus injury can lead to less successful outcomes.

Methods

The cohort consisted of 38 patients and knees that were treated at our institution from 1/1/2005 through 12/31/14 by the senior author. Data was prospectively gathered and retrospectively reviewed and extracted from a multi-ligamentous knee injury database that we created. Inclusion data was comprised of patients who underwent a PCL reconstruction for a grade III PCL tear and a minimum of 1-year follow-up. Exclusion criteria included an associated ACL injury and insufficient follow up. The patients in the study were seen postoperatively at 2 weeks, 6-8 weeks, 4-6 months, 6-9 months, 1 year, and 1+ years.

Results

38 patients and knees met inclusion criteria. All patients had grade III posterior drawer on physical exam. 89.5% (n=34) of these patients had an associated popliteus injury as seen during surgery. MRI findings were reviewed with respect to the popliteus and of those with an MRI (n=24) 63% either had no comment or incorrectly stated it was intact. Of the 4 knees without a popliteus injury, all had medial meniscal tears. Complications included 5% (n=2) with recurrent instability and underwent revision surgery.

Conclusions

In the setting of grade III PCL injury there is a high incidence of popliteus injury that is commonly missed on imaging and evaluation. The clinician must have a high suspicion for this injury pattern to ensure optimal outcomes for patients with PCL injuries. This has not been previously described in the literature, and thus further evaluation of this concomitant injury is necessary. Missing a popliteus injury could lead to sub-optimal long-term outcomes in patients that present with a PCL injury.