EP8.70 Force Plate Derived Squat Kinetics Predict Time to Crutch Discontinuation Following Hip Dysplasia Surgery

Abstract Introduction Following combined hip arthroscopy and periacetabular osteotomy (HA+PAO) for hip dysplasia, patients typically undergo 6-weeks of protected weightbearing with crutches to allow for bony healing. After clearance for full weightbearing, crutch discharge requires pain-free gait with grossly normal mechanics. Return to unassisted ambulation is a clinically meaningful milestone and often a patient priority. However, prognostic discussions of crutch discharge remain largely subjective. The purpose of this study was to determine whether 6-week force plate derived limb symmetry squat performance predicts time to crutch discharge following HA+PAO. We hypothesized that more symmetric squat performance would be associated with less days of crutch use. Methods Patients were retrospectively identified from a single surgeon, prospectively collected database. Patients who underwent HA+PAO, completed squat testing and iHOT-12 at 6-weeks, and reported discharge of crutch use were included. All patients followed a standard postoperative rehabilitation protocol indicating foot flat weightbearing for 6-weeks followed by progressive weightbearing after surgeon clearance. Force plate analysis evaluated kinetics during a double leg squat performed to a self-selected comfortable depth at a cadence of one squat every 2 seconds, with 5 seconds rest between repetitions. Three squats were collected and averaged. Multiple linear regression was performed to predict days of crutch use, using iHOT-12, concentric impulse limb symmetry index (LSI), and eccentric impulse LSI as independent variables. Results Nineteen patients (23.9±8.8 years, 18 females) were included in the analysis. Mean duration of crutch use was 64.4±24.1 days. At 6-weeks, the mean patient eccentric impulse LSI was 73.9±13.2% and hip-related function via the iHOT-12 was 33.6±12.4. These variables statistically significantly predicted days of crutch use, F(2,16) = 6.737, p = .008, R2 = 0.457. Multiple linear regression analysis demonstrated that every 1–2% increase in eccentric impulse LSI, or every 2-point increase in iHOT-12 score compared to the mean was associated with approximately one fewer day of crutch use. Clinically, our average patient would be predicted to experience a discharge of crutches 1-week earlier, from 9- to 8-weeks, by having 6-week eccentric impulse LSI of 84%, or recording a 6-week iHOT-12 of 47. Concentric impulse LSI was excluded from the final model because of multicollinearity (VIF > 5). Conclusion At 6-weeks following HA+PAO, greater force plate derived eccentric squat impulse LSI was associated with earlier crutch discontinuation, particularly when combined with patient-reported function. Objective squat kinetics may inform gait readiness beyond self-reported function alone. These findings can support a more informed rehabilitation progression and should encourage surgically safe early interventions to support patient load acceptance.