INERTIAL MEASUREMENT UNIT SENSORS CAN LIFT THE CEILING EFFECT ASSOCIATED WITH PATIENT-REPORTED OUTCOME MEASURES AND COMPREHENSIVELY ASSESS DIFFERENCES IN APPROACH FOR TOTAL HIP ARTHROPLASTY

Outcome metrics post-arthroplasty are typically based on crude, objective (complication-, reoperation- rates) outcomes, or subjective (patient-reported outcomes) measures (PROMs) with ceiling effects. Inertia measuring unit (IMU) sensors can provide performance-based, objective, measures (PBOMs) to track patient recovery but are yet to be evaluated in hip arthroplasty. Such assessment tools could unveil differences in pre-operative function and post-operative recovery following Total Hip Arthroplasty (THA) including different approaches. This study aims to 1. Assess rate of return to function following hip arthroplasty using subjective- and objective- measures; and 2. Test for association between PROs and PBOMs post- hip arthroplasty; and 3. Test for approach-specific differences This is a prospective, consecutive, IRB-approved, study from a single, academic center. consecutive, cohort study of 77 patients that received a THA (55% female; age: 61±8; BMI:27.6±4.6) under the care of 6 surgeons was studied. Fifty-two patients underwent THA anterior approach (AA; 52% female; age: 62.3±7.9; BMI: 27.2±4.3) and 25 had a posterior approach (PA; 60% female; age: 60±8.3; BMI:29±5.3). Selection of approach was surgeon choice – all surgeons involved were fellowship-trained with the AA. Patients underwent comprehensive assessments at regular intervals (pre-operatively and at 2-, 6-, 12- and 52- weeks post-operatively). At each assessment, PBOMs and PROMs were assessed using inertial measurement unit (IMU) sensors, located at the sacrum, mid-thigh, and ankles. Patients were asked to walk and perform sit-to-stand and stair ascend/descend tasks. PBOMs of interest included walking speed, stride length, impact load asymmetry and pelvic-angular velocity. The Oxford-Hip-Score (OHS) was the PROM of choice. Mean OHS improved from 21±.8 to 42±6 (p However, OHS improvement was not associated with improvements across PBOM parameters, indicating a discrepancy between subjective and objective functional improvements. PBOMs peaked prior to OHS. Pre-THA, OHS was similar between groups (AA:21.6±8.6; PA: 19.1±7.7, p=0.3). However, pre-THA PBOMs were superior for the AA compared to the PA (velocity: 0.81 vs 0.67m/s; stride: 0.97 vs 0.87m; impact asymmetry: 14 vs 22%; angular pelvic velocity: 35 vs 27m/s; p < 0 .001). Post-THA, approach differences across gait parameters reached lack of significance by 12-weeks for all (velocity: 1.1 vs 1.1m/s; stride: 1.2 vs 1.2m; angular pelvic velocity: 123 vs 124m/s) except for impact asymmetry (11% AA vs 15% PA), which may be accounted for based on selection bias when performing a PA. IMU sensors are a valuable assessment tool that may provide a more objective and accurate assessment of return-to-function, complementing, subjective, PROMs. Gait and loading performance “normalizes” prior to full functional recovery. Selective approach does not compromise care as those that underwent PA show good functional recovery, equalizing spatiotemporal gait and sit-to-stand activities within 12-weeks post-operatively, equivalent to what seen with AA, despite started at lower functional levels.