Background

The role of a lateral retinaculum release (LRR) in medial patellofemoral ligament (MPFL) reconstruction remains controversial. While an isolated LRR has been demonstrated to reduce forces required to displace the patella in biomechanical studies, it may also reduce the ability of dynamic stabilization in maintaining patellar tracking and counterintuitively contributing to an increased tendency towards lateralization. Criteria for LRR in combination with MPFL reconstruction remain heterogeneous & surgical indications are not uniformly applied. Prior studies have primarily been composed of small case series or a single prospective study with limited follow-up and no reported complications. The purpose of this study was to compare clinical outcome scores and failure rates of MPFL reconstruction between those with or without LRR.

Methods

A retrospective review identified all patients with lateral patellar instability and no prior surgical intervention who underwent either an isolated MPFL reconstruction or MPFL reconstruction with LRR between 2013 and 2019 at a single center. Demographic variables and preoperative imaging were analyzed with Kujala, Patient-Reported Outcomes Measurement Information System (PROMIS), International Knee Documentation Committee (IKDC), Single Assessment Numeric Evaluation (SANE), and Knee injury and Osteoarthritis Outcome Scores (KOOS) obtained at a minimum follow-up of 1-year.

Results

We identified 49 patients with isolated lateral patellar instability, where 31 underwent MPFL reconstruction and LRR with an average follow-up of 36.0 months & 18 underwent isolated MPFL reconstruction with an average follow-up of 29.3 months. There were no significant differences between age, gender, BMI, or tibial-tuberosity to trochlear groove distance. The overall failure rate, defined by recurrent surgery or dislocation, did not significantly differ between the two groups with a 19.3% (6/31) failure rate with MPFL+LRR & 11.1% (2/18) failure rate with isolated MPFL reconstruction. The average patient reported outcome scores collected did not significantly differ between MPFL+LRR and isolated MPFL reconstruction among any of the questionaries (Kujala: 78.4±15.0 v. 78.8±15.8, PROMIS: 74.0±9.8 v. 75.6 ± 10.9, IKDC: 58.3±9.6 v. 63.0±12.4, SANE: 71.6 ±16.6 v. 72.8 ± 22.8, KOOS Symptoms 76.5±14.6 v. 76.0±15.6, KOOS Pain 75.1±21.4 v. 79.3 ±16.6, KOOS ADL 88.0±12.0 v. 86.1±18.0, KOOS Sport 59.1±21.4 v. 71.1±24.8, KOOS QOL 57.1±20.1 v. 56.3 ± 23.6).

Conclusion

Isolated MPFL reconstruction without lateral release is not associated with worse patient reported outcomes or an increased failure rate in patients with lateral patellar instability at a minimum of 1 year follow-up. Subjective outcomes of MPFL reconstructions are not influenced by LRR. This further supports previous studies with similar conclusions