Factors Associated With an Increased Risk of Recurrence After a First-Time Patellar Dislocation: A Systematic Review and Meta-analysis.

ABSTRACT

BACKGROUND: Recurrent dislocations after a first-time lateral patellar dislocation may occur in more than 50% of patients and can cause long-term disability. Many factors have been suggested to influence the risk of recurrence. PURPOSE: To systematically review and quantitatively synthesize the literature for factors associated with an increased risk of recurrence after a first-time patellar dislocation. STUDY DESIGN: Systematic review and meta-analysis of observational studies. METHODS: A total of 4 electronic databases were searched to identify relevant studies published before February 7, 2019. A quality assessment was performed with the National Heart, Lung, and Bone Institute quality assessment score. Factors assessed for their effect on the recurrence rate were documented, and the rates of recurrence were compared. Pooled dichotomous data were analyzed using random-effects meta-analysis with odds ratios (ORs). RESULTS: A total of 17 studies met the criteria for inclusion. The overall rate of recurrent dislocations after a first-time lateral patellar dislocation was 33.6%. An increased risk of recurrence was reported in patients with a younger age (OR, 2.61; P < .00001), open physes (OR, 2.72; P < .00001), trochlear dysplasia (OR, 4.15; P = .009), an elevated tibial tuberosity-trochlear groove (TT-TG) distance (OR, 2.87; P < .00001), and patella alta (OR, 2.38; P = .004). Sex, patterns of medial patellofemoral ligament injury, and history of contralateral dislocations were not found to be associated with an increased recurrence rate (P≥ .05). In studies that reported on the presence of multiple risk factors, recurrence rates were 7.7% to 13.8% when no risk factors were present but increased to 29.6% to 60.2% when 2 risk factors were present and to 70.4% to 78.5% when 3 risk factors were present. CONCLUSION: Younger age, open physes, trochlear dysplasia, elevated TT-TG distance, and patella alta were key risk factors for the recurrence of lateral patellar dislocations. Despite being not infrequently cited as risk factors, patient sex and a history of contralateral dislocations were not found to be significant risk factors. The presence of multiple risk factors increased the risk, and the development of predictive instability scores in large patient cohorts using all established risk factors should be a focus of future studies.