Comparison of body weight distribution, peak vertical force, and vertical impulse as measures of hip joint pain and efficacy of total hip replacement.

ABSTRACT

OBJECTIVE: To determine whether there is a difference between the ability of peak vertical force (PVF), vertical impulse (VI), and percentage body weight distribution (%BW(dist) ) in differentiating which leg is most affected by hip joint pain before total hip replacement (THR) surgery, and for measuring changes in limb use after THR surgery. STUDY DESIGN: Prospective clinical study. ANIMALS Dogs (n = 47). METHODS: Ground reaction force (GRF) data were collected using a pressure-sensitive walkway the day before THR surgery and at ∼3, 6, and 12 months postoperatively. PVF and VI expressed as a percentage of body weight (%PVF, %VI), and %BW(dist) were recorded. Regression models performed separately for each outcome were used for statistical analysis. RESULTS: When comparing limb use between the affected limb (AP) and the nonaffected limb (NP) preoperatively, differences between limbs were statistically significant when evaluated using PVF (P = .023), VI (P = .010), and %BW(dist) (P = .012). When evaluating the magnitude of absolute and percentage change difference in AP limb use preoperatively versus postoperatively, differences were statistically significant when evaluated using PVF (P < .001 and P = .001, respectively), VI (P = .001 and P < .001) and %BW(dist) (P < .001 and P < .001). CONCLUSION: There appeared to be no difference in the sensitivity of VI, PVF, and %BW(dist) for evaluating limb use before and after THR.