The Journal of Hip Surgery 2017; 01(04): 194-199
DOI: 10.1055/s-0038-1635101
Original Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Dislocation Rates following Anterior Approach THA: The Role of Functional Pelvic Tilt

Preetesh Patel
1   Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, Florida
,
Colin McNamara
1   Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, Florida
,
Eric Slotkin
2   Orthopaedic Associates of Reading, Ltd., Reading, Pennsylvania
,
Amar Mutnal
1   Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, Florida
,
Wael Barsoum
1   Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, Florida
,
Juan C. Suarez
1   Department of Orthopaedic Surgery, Cleveland Clinic Florida, Weston, Florida
› Author Affiliations
Further Information

Publication History

23 August 2017

19 January 2018

Publication Date:
19 March 2018 (online)

Abstract

Various target zones for acetabular cup placement have been suggested to minimize dislocation following total hip arthroplasty (THA), though dislocations occur despite proper positioning. The authors have reported accuracy of fluoroscopic guidance in cup positioning during direct anterior approach (DAA) THA when using a standardized fluoroscopic technique functional pelvic tilt. They believe that cup placement with regard to functional pelvic tilt, rather than static reference frames, will offer improved stability. A cohort of 1,597 fluoroscopy-assisted DAA primary unilateral THA patients was prospectively followed for a minimum of 1 year and component position measured radiographically. Target cup position was based off the standing anteroposterior pelvis while using conventional safe zone parameters. Dislocation rate was assessed. Average follow-up was 13.1 months (range 1–6 years). The mean abduction angle was 37.7° and the mean anteversion angle was 16.2°. Overall, 1,517 (95.0%) fell within the targeted abduction range, 1,528 (95.7%) fell within the targeted anteversion range, and 1,456 (91.2%) simultaneously met both criteria. There were nine dislocations, eight within the combined safe zone, for a dislocation rate of 0.56%. Fluoroscopy can improve accuracy and precision of cup placement in DAA THA. Conventional safe zone parameters applied using functional pelvic tilt resulted in a low dislocation rate, with most dislocations occurring within the safe zone. Using a dynamic functional safe zone may further reduce dislocation rates after DAA THA, though other factors that contribute to instability must be accounted for in future studies. This study had a III level of evidence.