Abstract
ObjectiveMedial patellofemoral ligament (MPFL) injury occurs in the majority of the cases of acute patellar dislocation. The role of concomitant lateral retinaculum release with MPFL reconstruction is not clearly understood. Even though the lateral retinaculum plays a role in both medial and lateral patellofemoral joint stability in MPFL intact knees, studies have shown mixed clinical outcomes following its release during MPFL reconstruction surgery. Better understanding of the biomechanical effects of the release of the lateral retinaculum during MPFL reconstruction is warranted. We hypothesize that performing a lateral release concurrent with MPFL reconstruction will disrupt the patellofemoral joint biomechanics and result in lateral patellar instability.MethodsA previously developed and validated finite element (FE) model of the patellofemoral joint was used to understand the effect of lateral retinaculum release following MPFL reconstruction. Contact pressure (CP), contact area (CA) and lateral patellar displacement were recorded. abstract.ResultsFE modeling and analysis demonstrated that lateral retinacular release following MPFL reconstruction with tibial tuberosity-tibial groove distance (TT-TG) of 12 mm resulted in a 39% decrease in CP, 44% decrease in CA and a 20% increase in lateral patellar displacement when compared to a knee with an intact MPFL. In addition, there was a 45% decrease in CP, 44% decrease in CA and a 21% increase in lateral displacement when compared to a knee that only had an MPFL reconstruction.ConclusionThis FE-based analysis exhibits that concomitant lateral retinaculum release with MPFL reconstruction results in decreased PF CA, CP and increased lateral patellar displacement with increased knee flexion, which may increase the risk of patellar instability.
Highlights
Acute patellar dislocations primarily occur in active young patients [1], with a recurrence rate of 17% after the first dislocation episode and up to 49% after recurrent dislocations [2]
finite element (FE) modeling and analysis demonstrated that lateral retinacular release following medial patellofemoral ligament (MPFL) reconstruction with tibial tuberosity-tibial groove distance (TT-TG) of 12 mm resulted in a 39% decrease in Contact pressure (CP), 44% decrease in contact area (CA) and a 20% increase in lateral patellar displacement when compared to a knee with an intact MPFL
This FE-based analysis exhibits that concomitant lateral retinaculum release with MPFL reconstruction results in decreased PF CA, CP and increased lateral patellar displacement with increased knee flexion, which may increase the risk of patellar instability
Summary
Acute patellar dislocations primarily occur in active young patients [1], with a recurrence rate of 17% after the first dislocation episode and up to 49% after recurrent dislocations [2]. Many authors have advocated for acute treatment of the medial patellofemoral ligament (MPFL) after a first-time patellar dislocation [9,10,11]. Bedi et al measured the force required to displace the patella 1 cm laterally in eight fresh-frozen human cadaveric knees when the MPFL was transected, upon repair, and when lateral release was added. They noticed that lateral release reduced the required force by 7% to 11% compared with the MPFLrepaired knee Their findings support the hypothesis that lateral release cannot be routinely performed in primary repair of the MPFL ligament for acute patellar instability. The role of lateral retinacular release in MPFL reconstruction surgery as the treatment for patellar instability should be investigated
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