Survival rates and reasons for revision of different stem designs in total hip arthroplasty for developmental dysplasia: a regional registry study

INTRODUCTION: Total hip arthroplasty (THA) in dysplastic hips is challenging, and each specific implant used in this context has been associated with specific complications. A registry study was performed to query survival rates, hazard ratios, and reasons for revision of different stem designs in THAs after developmental dysplasia of the hip. MATERIALS AND METHODS: A regional arthroplasty registry was inquired about cementless THAs performed for hip dysplasia from 2000 to 2017. Patients were stratified according to stem design in tapered (TAP; wedge and rectangular), anatomic (ANAT), and conical (CON), and divided on the basis of modularity (modular, M; nonmodular, NM). In total, 2039 TAP stems (548 M and 1491 NM), 1435 ANAT (1072 M and 363 NM), and 2287 CON (1020 M and 1267 NM) implants were included. Survival rates and reasons for revisions were compared. RESULTS: The groups were homogeneous for demographics, but not fully comparable in terms of implant features. NM-CON stems showed the highest risk of failure (significant) and a high risk for cup aseptic loosening (2.5%). The adjusted risk ratio showed that NM-CON was more prone to failure (HR versus NM-ANAT: 3.30; 95%CI 1.64–7.87; p = 0.0003). Revision rates for dislocations and stem aseptic loosening did not differ between cohorts. CONCLUSIONS: NM-CON stems showed the highest risk of failure, especially high rates of cup aseptic loosening. NM-CON implants were not more prone to dislocations and stem aseptic loosening. Clinical comparative studies are required to investigate the causes of NM-CON failures, which may be due to abnormal acetabular morphology or imperfect restoration of the proximal biomechanics.