Long-term results of custom cementless-stem total hip arthroplasty performed in hip fusion

Due to complex anatomical considerations, results of cementless-stem total hip arthroplasty (THA) in hip fusion remain controversial compared with conventional THA. We therefore aimed to analyse 3D anatomy of the fused hip based on pre-operative computed tomography (CT) scans, functional outcomes based on the Harris Hip Score (HHS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS), modifications of hip anatomy based on post-operative standardised radiography, and determine complication rate and long-term survival based on Kaplan-Meier analysis.

We retrospectively studied 23 hips that underwent conversion of a fused hip to THA using a 3D CT scan-based custom titanium (Ti alloy hypoxyapetite (HA)-coated stem. The mean follow-up was 15 (9-22) years. Femur anteversion ranged from -29° to 80°.

HHS improved from 59 to 89 points and average range of motion (ROM) was 88° for flexion. Back pain decreased in 62%, and knee pain decreased in 42%. The mean post-operative leg-length discrepancy was 7.8 mm. No intra-operative complications occurred. One aseptic stem loosening for mechanical failure was observed. The Kaplan-Meier survivorship considering revision for any reasons as the end point was 95.6% [95% confidence interval (CI) 92.4-98.8] at 15 years.

Custom cementless stems may be an interesting solution to address the particular anatomical features of hip fusion at the time of THA, with an excellent survival rate at 15 years.