The Presence of a Trochlear Bump and Patella Alta May Predict the Risk of Recurrent Instability After Isolated Medial Patellofemoral Ligament Reconstruction: A Systematic Review and Meta-analysis

Medial patellofemoral ligament reconstruction (MPFLR) is an excellent surgical option for patients with recurrent patellar instability. This technique has demonstrated significant improvements in patient-reported outcomes, high rates of return to sport, and low rates of failure. However, there is debate regarding the use of isolated MPFLR in the setting of concomitant pathoanatomic features such as patella alta, trochlear dysplasia, or a lateralized tibial tubercle. To estimate the overall relative effect sizes as well as strength of evidence supporting described risk factors for recurrent instability after isolated MPFLR. Systematic review and meta-analysis. A systematic review was performed in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed, Embase, Cochrane, and Ovid/MEDLINE databases were queried. Clinical studies for outcomes of isolated MPFLR reporting recurrent instability and associated risk factors were included. Data for each risk factor analyzed by at least 2 studies were extracted, and the heterogeneity of studies was determined by I2 value. For variables evaluated in studies determined to have fair homogeneity, defined as I2 <25%, DerSimonian-Laird random-effects models were generated and effect sizes were represented as mean differences or odds ratios. Nine studies examining risk for recurrent instability after isolated MPFLR were identified, with 5 overlapping risk factors with low heterogeneity between studies: age, sex, tibial tubercle to trochlear groove (TT-TG) distance, Caton-Deschamps Index (CDI), and trochlear dysplasia. There was strong evidence to support the risk of recurrent instability associated with CDI >1.3 (OR, 2.72; P = .02) and dysplasia with a trochlear bump (DeJour type B or D; OR, 3.28; P <.001). Age, sex, and TT-TG distance did not cause an increased risk of recurrent instability with currently available aggregate data. There are signs of increased risk of failure of isolated MPFLR in the setting of DeJour type B and D trochlear dysplasia and patella alta (CDI, >1.3). Currently available data suggest that age, sex, and TT-TG distance do not cause a higher risk of recurrence for patients undergoing isolated MPFLR.