JOA - 2026-06-01 - Journal Article
Prospective Evaluation of Hip-Spine Dynamics in Patients Who Have a Primary Total Hip Arthroplasty Dislocation: A Matched Case-Control Study.
Trostel C, van Erp JHJ, Snijders TE, Weinans HH, Hentenaar B, de Gast A, Schlösser TPC
Topics
Key Takeaway
High pelvic incidence (60° vs 52°, P=0.015) and excessive transverse version of the acetabular cup (38° vs 32°, P=0.042) were independent predictors of primary THA dislocation in a prospective matched cohort.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This prospective matched case-control study compared spinopelvic and 3D implant orientation parameters between 23 primary THA dislocations and 23 stable controls using standing AP and lateral pelvic radiographs. Dislocating hips had significantly higher pelvic incidence (60° vs 52°) and transverse cup version (38° vs 32°); logistic regression identified PI, transverse cup version, and surgical approach as independent dislocation predictors. Anterior dislocations showed higher sagittal ante-inclination (48° vs 34°, P=0.012) compared to posterior dislocations, suggesting direction-specific implant orientation failure modes.
Key Limitation
The anterior dislocation subgroup contains only 5 patients, making direction-specific conclusions statistically underpowered and potentially unreliable for clinical generalization.
Original Abstract
BACKGROUND
Understanding of the comprehensive hip-spine relationship may reduce total hip arthroplasty (THA) dislocation. However, the impact of sagittal spino-pelvic dynamics on three-dimensional implant orientation has not been investigated prospectively. This study aimed to assess hip-spine dynamics and changes in three-dimensional implant orientation in patients who have stable and unstable primary THAs.
METHODS
In this prospective, case-control study, 23 adults who had a THA dislocation were matched to 23 patients who had a stable implant. Of the 23 dislocations, 17 sustained a posterior, and five sustained an anterior dislocation; one was unknown. Standing anterior-posterior and standing and sitting lateral pelvic radiographs were obtained. Sagittal spinopelvic morphology and orientation parameters, coronal and sagittal acetabular cup, and femoral component orientation parameters were measured. Transverse component orientation parameters were computed. Logistic regressions were conducted to determine the impact of demographics and hip-spine parameters on the likelihood for dislocation.
RESULTS
The unstable THAs had significantly higher pelvic incidence (PI; 60 ± 13° versus 52 ± 10°, P = 0.015) and transverse version of the acetabular component (TV Cup ; 38 ± 11° versus 32 ± 8°, P = 0.042) compared to the stable THAs. Patients who have anterior dislocations had higher sagittal ante-inclination of the acetabular component (SAI Cup ) than posterior dislocations (48 ± 5° versus 34 ± 10°, P = 0.012). Based on logistic regression analyses, PI, TV Cup , and the approach were significant predictors of THA dislocation.
CONCLUSIONS
By assessment of spino-pelvic characteristics, surgeons could identify patients at increased risk for THA dislocation preoperatively based on a high PI. Posterior dislocations seem to occur more in patients who have more TV Cup and a postero-lateral approach, anterior dislocations seem to occur in patients who have more SAI Cup , TV Cup , and a direct anterior approach. This suggests implementing a patient-specific functional safe zone of the acetabular component may further reduce THA dislocation rates.