Abstract
Purpose: Dislocation after THA is a multifactorial challenge involving patient, surgical and implant variables. The extramedullary features of a hip implant—offset, neck length, height, version, and head/neck ratio—significantly impact the stability of the reconstruction. We report a significant difference in dislocation rate between two different femoral stems.
Methods: Between May, 1998 and October, 2003, 263 primary THAs were performed by a single surgeon, utilizing identical surgical technique. Acetabular fixation was cementless with 3 varieties of cups in 262 hips and cemented in one hip. 141 hips had a single cemented femoral component (C-Stem, DePuy, Warsaw, Indiana), and 122 hips had a single cementless design (S-ROM, DePuy, Warsaw, Indiana).
Results: Diagnosis, gender, and side were similar between the groups. Mean age of the cemented group was 68.9 years(R 33 to 92) and of the cementless group was 51.9 years (R 19 to 79). The 3 acetabular designs were equally distributed between groups. All hips were implanted with 28 mm heads. There were 12/141 (8.5%) dislocations in the cemented group, and 3/122 (2.5%) dislocations in the cementless group (p < 0.10).
Conclusions: Stability after THA is affected by design features of a femoral implant, including height, neck length, offset, and version. The use of a single stem in all patients may not adequately address individual biomechanic variability. Careful preoperative templating, and the availability of multiple stem designs within a single fixation philosophy, may facilitate matching of extramedullary features to an individual patient’s anatomy in order to optimize postoperative hip stability.
The abstracts were prepared by Ms Orah Naor. Correspondence should be addressed to Israel Orthopaedic Association at PO Box 7845, Haifa 31074, Israel.
