PREVALENCE OF ADVERSE SPINOPELVIC CHARACTERISTICS IN PATIENTS UNDERGOING TOTAL HIP ARTHROPLASTY AND ITS CLINICAL IMPLICATIONS: A PROSPECTIVE STUDY

Adverse spinopelvic characteristics (ASC) are associated with increased dislocation risk following primary total hip arthroplasty (THA). How often such patients are presenting to clinic and whether surgical approach influences dislocationrisk is unknown. This study aims to 1: Describe prevalence of patients presenting for a THA with adverse spinopelvic characteristics; 2. Test for association with pre-THA functional scores; and 3. Describe early-term dislocation rate with different approaches. This is a prospective, three-center, multi-surgeon, consecutive, cohort series of 460 patients (mean age: 65.8±11.8y; 52.5% females; mean BMI: 28.1±5.5kg/m2) undergoing THA through anterolateral- (n=202; 44%), direct anterior- (n=216; 47%) or posterior- approaches (n=142; 22.8%) without dual-mobility bearings or robotics. All participants underwent spinopelvic radiographs in standing and deep-flexed-seated positions to determine spinopelvic characteristics. ASC were Pelvic tilt >19°; spinopelvic imbalance (PI-LL >10°); and spinal stiffness (lumbar flexion <20°). Pre-operative patient reported outcomes was measured using Oxford Hip Score (OHS). Dislocation rates were prospectively recorded at followup of 1.5±0.9 years. Presence of any ASC was seen in 41%. Most common characteristic was high pelvic-tilt (34%), followed by spinopelvic imbalance (22%) and spine stiffness (6%). Only 3% had all three characteristics. 1% has all 3 ASC characteristics (n=11). There was no difference in the pre-operative OHS between patients without or with ASC (20.2±9.4 vs. 18.1±7.5; p=0.370). At 1-year, two patients sustained a dislocation (0.4%), both with all three ASC characteristics that had posterior approach. Amongst patients with ASC, anterior- and anterolateral approaches were associated with reduced dislocation risk (p=0.03). The prevalence of any ASC, especially high pelvic-tilt, is high. However, the presence of all three ASCs is low (3%). Use of the anterior- and anterio-lateral approaches in such patients minimizes dislocation risk. However, patients with ASCs, especially all three, treated with posterior approach may benefit from advanced technology to minimize dislocation-risk.