Abstract
The Hip Dysfunction and Osteoarthritis Outcome Score for Joint Replacement (HOOS-JR) was developed as a short-form survey to measure progress after total hip arthroplasty (THA). However, the longitudinal validity of the scale structure pertaining to the modified five-item HOOS-JR has not been assessed. Therefore, the purpose of this study was to evaluate the structural validity, longitudinal invariance properties, and latent growth curve (LGC) modeling of the modified five-item HOOS-JR in a large multi-site sample of patients who underwent a THA. A longitudinal study was conducted using data from the Surgical Outcome System (SOS) database. Confirmatory factor analyses (CFAs) were conducted to assess the structural validity and longitudinal invariance across five time points. Additionally, LGC modeling was performed to assess the heterogeneity of the recovery patterns for different subgroups of patients. The resulting CFAs met most of the goodness-of-fit indices (CFI = 0.964-0.982; IFI = 0.965-0.986; SRMR = 0.021-0.035). Longitudinal analysis did not meet full invariance, exceeding the scalar invariance model (CFI(DIFF) = 0.012; χ(2)(DIFF) test = 702.67). Partial invariance requirements were met upon release of the intercept constraint associated with item five (CFI(DIFF) test = 0.010; χ(2)(DIFF) = 1073.83). The equal means model did not pass the recommended goodness-of-fit indices (CFI(DIFF) = 0.133; χ(2)(DIFF) = 3962.49). Scores significantly changed over time, with the highest scores identified preoperatively and the lowest scores identified at 2- and 3-years postoperatively. Upon conclusion, partial scalar invariance was identified within our model. We identified that patients self-report most improvements in their scores within 6 months postoperatively. Females reported more hip disability at preoperative time points and had faster improvement as measured by the scores of the modified five-item HOOS-JR.