Hip flexion after Birmingham hip resurfacing: role of cup anteversion, anterior femoral head-neck offset, and head-neck ratio

• Published in: The Journal of arthroplasty 2010-04, Vol.25 (3), p.387-391
• Main Authors: Malviya, Ajay, Lingard, Elizabeth A, Malik, Atul, Bowman, Russell, Holland, James P
• Format: Article
• Language: English
• Subjects: Aged; Arthroplasty, Replacement, Hip - methods; Biomechanical Phenomena; Female; Hip Joint - diagnostic imaging; Hip Joint - surgery; Hip Prosthesis; Humans; Male; Middle Aged; Models, Theoretical; Multivariate Analysis; Radiography; Range of Motion, Articular; Regression Analysis; Retrospective Studies; Treatment Outcome
• ISSN: 1532-8406
• DOI: 10.1016/j.arth.2009.01.026

We aimed to investigate the factors affecting range of flexion after hip resurfacing. A total of 82 cases, operated by a single surgeon, were assessed at a mean of 43 months. The Einzel-Bild-Roentgen-Analysis for the acetabular cup software was used to measure socket orientation. Range of flexion had a moderate positive correlation with cup anteversion (R = 0.26, P = .017), weak but significant negative correlation with neck diameter (R = -0.23, P = .042), and none with anterior femoral head-neck offset. Using multivariate analysis that adjusted for age, sex, cup anteversion and inclination, head-neck offset ratio, head-neck ratio, and neck diameter, the only significant correlate of flexion was cup anteversion (P = .017). Care should be taken during cup placement to allow adequate anteversion to be maintained in Birmingham hip resurfacing because this can affect flexion range of motion.