Abstract
Introduction and Objective
An important subset of patients is dissatisfied after total joint arthroplasty (TJA) due to residual functional impairment. This study investigated the assessment of objectively measured step-up performance following TJA, to identify patients with poor functional improvement after surgery, and to predict residual functional impairment during early postoperative rehabilitation. Secondary, longitudinal changes of block step-up (BS) transfers were compared with functional changes of subjective patient reported outcome measures (PROMs) following TJA.
Materials and Methods
Patients with end stage hip or knee osteoarthritis (n = 76, m/f = 44/32; mean age = 64.4 standard deviation 9.4 years) were measured preoperatively and 3 and 12 months postoperatively. PROMs were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscore. BS transfers were assessed by wearable-derived measures of time. In our cohort, subgroups were formed based on either 1) WOMAC function score or 2) BS performance, isolating the worst performing quartile (impaired) of each measure from the better performing others (non-impaired). Subgroup comparisons were performed with the Man-Whitney-U test and Wilcoxon Signed rank test resp. Responsiveness was calculated by the effect size, correlations with Pearson's correlation coefficient. A regression analysis was conducted to investigate predictors of poor functional outcome.
Results
WOMAC function scores were strongly correlated to WOMAC pain scores (Pearson's r=0.67–0.84) and moderately correlated to BS performance (Pearson's r = 0.31–0.54). Prior to surgery, no significant differences for WOMAC function scores and BS performance were found between the impaired and non-impaired subgroups. One year after TJA, our cohort performed significantly better at WOMAC and BS with largest effect size for the non-impaired subgroups (0.62 and 0.43 resp.) At 12 months postop, 56% of patients allocated to the impaired subgroup defined by WOMAC, represented the impaired subgroup defined by BS. Allocation to the impaired subgroup at 3 months postop, raised the odds for belonging to the impaired subgroup at 12 months for WOMAC with an odds ratio=19.14 (67%) and for BS with an odds ratio=4.41 (42%).
Conclusions
Assessment of BS performance following TJA reveals residual functional impairment that is not captured by pain-dominated PROMs. Its additional use may help to early identify those patients at risk for a poor outcome.
