Physical Performance Tests Correlate With Patient-reported Outcomes After Periacetabular Osteotomy: A Prospective Study.

INTRODUCTION Individuals with hip dysplasia report significant functional disability that improves with periacetabular osteotomy (PAO). Four physical performance measures (PPMs) have been recently validated for use with nonarthritic hip conditions; however, their ability to detect functional improvement and correlate with improvements in popular hip-specific patient-reported outcome (PRO) instruments after PAO is unknown. The purpose of this study was to evaluate the responsiveness of four PPMs up to 1 year after PAO, compare PPMs with established PRO measures at these time points, and report the acceptability and utility of PPMs for assessing outcomes after PAO. METHODS Twenty-two participants aged 15 to 39 years completed the timed stair ascent (TSA), sit-to-stand five times (STS5), self-selected walking speed, four-square-step test, and seven hip-specific PRO measures before surgery and at approximately 6 months and 1 year after PAO. They completed questions regarding acceptability and utility of both types of testing. Wilcoxon rank sum test and unpaired Student t-tests were used to assess differences between time points; Spearman correlation and generalized linear modeling were used to determine the relationship between PPMs and PRO measures. RESULTS Six months after PAO, participants showed significant improvements on all seven PRO instruments (P < 0.001) and on the STS5 (P = 0.01). At one year, these improvements were maintained and TSA also improved (P = 0.03). Improvement in other PPMs did not reach significance (P = 0.07 and 0.08). The STS5 test demonstrated moderate to strong correlation (|r| = 0.43 to 0.76, P < 0.05) with all PRO measures, and the TSA test demonstrated moderate to strong correlation with almost all measures (|r| = 0.43 to 0.58, P < 0.05). Correlations strengthened on subanalysis of participants with unilateral disease (n = 11) (|r| = 0.56 to 0.94, P < 0.05). All participants (100%) found PPM testing acceptable despite disability; 25% preferred PPMs to PRO measures, whereas 75% of participants found them equal in usefulness. DISCUSSION The STS5 and TSA tests demonstrated moderate to very strong correlation with PRO measures at six and 12 months after PAO for dysplasia. These tests could be used as a functional outcome to supplement PRO instruments after PAO.