Isolated Medial Patellofemoral Ligament Reconstruction for Patellar Instability Regardless of the Tibial Tubercle Trochlear Groove Distance: Outcomes at 1 and 2 Years

BACKGROUND: Several surgical options exist for treatment of recurrent patellar instability. The treatments can be divided into ligamentous and bony procedures. It is currently unclear which patients require a bony procedure in addition to a soft tissue reconstruction. PURPOSE: To report the one and two-year outcomes of patients following medial patellofemoral ligament (MPFL) reconstruction performed in isolation regardless of the patellar height, tibial tubercle trochlear groove distance (TT-TG) or trochlear dysplasia. HYPOTHESIS:: Patients will have <5% re-dislocation rate and significant improvements in patient reported outcome measures (PROMs) following isolated MPFL reconstruction. METHODS: All patients with recurrent patellar instability and without significant unloadable chondral defects, failed previous surgery or pain greater than or equal to 50% as their chief complaint, were prospectively enrolled beginning March of 2014. All patients underwent a primary, unilateral, isolated MPFL reconstruction regardless of concomitant bony pathology for treatment of recurrent patellar instability. Patients were followed at standard intervals. PROMs were collected at one year and two year follow up visits. Information on recurrent subjective instability, dislocations, and ability to return to sport (RTS) was recorded. TT-TG and patellar height (using the Caton-Deschamps index) were measured on magnetic resonance images. RESULTS: Overall, 90 patients (77% female; average age 19.4 +/- 5.6 years) underwent a MPFL reconstruction from March 2014 to August 2017; 63 (70%) of whom reached one year follow up, and 35 of these patients (39%) reached 2-year follow-up. No patient experienced a redislocation; 96% of patients at one year and 100% of patients at two years had no subjective patellofemoral instability. RTS rates at one and two years were 59% and 75% respectively. No patient experienced a complication at one year. All patients had a clinically and statistically significant improvement from baseline to 1-year follow-up in the following PROMs: Knee injury and Osteoarthritis Outcome Score Quality of Life (KOOS QOL) (32.7 to 72.0; p<0.001), International Knee Documentation Committee (IKDC) (51.4 to 82.6; p<0.001) Kujala (62.2 to 89.5; p<0.001), and all general health PROM. No clinically and statistically significant change was seen between 1- and 2-year follow-ups in all outcome scores (all p>0.05). A non-statistically significant increase was seen in sporting activity of the Pediatric Functional Activity Brief Scale (Pedi-FABS) (13.9 to 16.7 p=0.292) at 2 years. Average patient satisfaction was 9.3 of 10 (10 being most satisfied) at 1- and 2-year follow-up. Average TT-TG was 15.1 +/- 4.0. Average patellar height was 1.25 +/- 0.17. CONCLUSION: Isolated MPFL reconstruction is an effective treatment for patellar instability and provides significant improvements in PROMs with a low redislocation/instability rate at early 1 and 2 year follow up, regardless of bony pathologies including TT-TG, Caton-Deschamps Index and trochlear dysplasia. The goal of this ongoing prospective study is to follow these patients out for 5 to 10 years to assess what radiologic and physical examination factors predict failure of isolated MPFL reconstruction.