A systematic review of outcomes reported in randomized controlled trials involving people with patellar dislocations

The primary aims were to determine what outcome domains, outcome measurement instruments, and outcome measurement timepoints are reported in randomized controlled trials (RCTs) involving people with patellar dislocations. The secondary aims were to determine what primary outcomes were used and how a recurrent patellar dislocation was defined when this was used as an outcome.

We searched MEDLINE, Embase, CINAHL, the Cochrane Database of Controlled Trials, and trial registries (last search: January 2024) for RCTs evaluating treatments for people with a patellar dislocation irrespective of age or sex. We identified the unique outcomes in included studies and mapped these onto the World Health Organization's International Classification of Functioning, Disability and Health (WHO ICF) framework to identify the measured domains. We synthesized results into tables, figures, and text. A critical appraisal of included studies was not required for this systematic review.

From the 70 included studies, we identified 141 unique outcomes. The most commonly used unique outcome was a recurrent ipsilateral patellar dislocation (used in 55 studies), but only 17/55 studies (31%) reported how this was defined (i.e. the criteria required for a recurrent ipsilateral patellar dislocation event to be recorded). Unique outcomes mapped onto 66 second-level domains of the WHO ICF framework, and 56% (593/1,052) in the 'activities and participation' domain. Included studies used 42 different patient-reported outcome measures (PROMs), most commonly the Kujala Patellofemoral Score (71%, 50/70 studies), but 28 PROMs (60%) were used only once. In all, 31 different primary outcomes were identified from 47 included studies, with 14 primary outcomes (45%) used only once among included studies. The Kujala Patellofemoral Score was also the most common primary outcome (38%, 18/47 studies). Outcome measurement timepoints varied, but the most common timeframe for primary outcome measurement was > one to three years (46%, 16/35 studies that provided data).

The variability in the outcome domains, PROMs, and primary outcomes measured in RCTs evaluating patellar dislocation treatments highlights that a core outcome set is needed. This process is underway and is being informed by this systematic review's findings.