Evaluation of Spino-Pelvic Parameters in Asian Patients Undergoing Total Hip Arthroplasty

Emerging research emphasizes the critical relationship between the hip and spine affecting implant positioning in total hip arthroplasty (THA). While spino-pelvic parameters and mobility patterns have been well described in Western populations, corresponding data from Asian patients undergoing THA remain limited. The primary objective of this study was to evaluate preoperative spino-pelvic parameters in Asian patients undergoing THA. The secondary objectives were to classify these patients using the hip-spine classification system and to compare the observed distribution with existing literature.

A multicenter, retrospective observational study was conducted across six high-volume centers from June 2023 to December 2024. Patients aged ≥18 years undergoing primary THA with available flexed-seated and standing lateral lumbosacral spine radiographs were included. Radiographic parameters were independently measured by two observers, patients were categorized according to the hip-spine classification, and statistical analyses were performed.

A total of 836 patients (mean age: 46.35±14.4 years; 72% male) were eligible for final evaluation. Avascular necrosis of the femoral head was the predominant indication (87.1%). Radiographic measurements showed excellent reproducibility (intraclass correlation coefficient (ICC)=0.82). Distribution according to hip-spine classification was: 1A (78.9%, N=660), 1B (9.6%, N=80), 2A (8%, N=67), and 2B (3.5%, N=29). Mean pelvic incidence, lumbar lordosis, standing sacral slope, and sitting sacral slope were 48.78°±10°, 53.88°±9.95°, 38.82°±8.85°, and 14.61°±11.14°, respectively.

This study provides a large, multicenter descriptive analysis of spino-pelvic parameters in an Asian THA population and demonstrates a predominance of normal spino-pelvic alignment and mobility patterns when classified using the hip-spine classification system. The observed distribution differs from that reported in Western cohorts, likely reflecting regional and etiological differences. These findings offer a foundational understanding of spino-pelvic characteristics in Asian patients undergoing THA and highlight the need for future longitudinal studies correlating spino-pelvic classification with postoperative clinical outcomes.