Increased risk of periprosthetic fracture associated with decreased aseptic loosening in C-stem compared with the Charnley Elite Plus in primary total hip arthroplasty: a minimum 10-year follow-up study.

Abstract

Background: The Charnley stem design has evolved, with notable modifications from the 6th generation (Elite Plus) to the 7th generation (C-stem), potentially affecting load transmission and clinical outcomes. This study aimed to compare the clinical, radiological, and survival outcomes between the Elite Plus and C-stem.

Methods: A retrospective review was conducted on 131 primary total hip arthroplasties in 115 patients. A minimum 10-year follow-up was completed for 89 hips (78 patients) with the Elite Plus and 42 hips (37 patients) with the C-stem, with mean follow-ups of 15.8 and 11.7 years, respectively.

Results: The surgical procedures were hybrid arthroplasty with lateral and posterior approach for the Elite Plus group and cement arthroplasty with anterior and lateral approach for the C-stem group. In the Elite Plus group, five patients experienced dislocations and three developed aseptic loosening (AL); in the C-stem group, three cases of periprosthetic fracture (PPF) occurred. Four cases in the Elite Plus and two cases in the C-stem group required revision arthroplasty. The reasons for revision surgery were AL of the acetabular component in two cases and femoral AL in two cases in the Elite Plus group and PPF in two cases in the C-stem group. Radiolucent lines were significantly more frequent with the Elite Plus (33.7%) than with the C-stem (11.9%). After excluding three patients with extreme subsidence (≥ 3 mm) in the Elite Plus group, the average stem subsidence was found to be significantly larger with the C-stem (0.88 mm) than with the Elite Plus (0.17 mm) (p < 0.001, Mann-Whitney U test). With revision surgery due to any reason as the endpoint, the 10-year survival rates were 96.6% for the Elite Plus and 95.2% for the C-stem, showing no significant difference. However, survival rates differed significantly with PPF as the endpoint (100% for the Elite Plus vs. 92.9% for the C-stem, p = 0.01).

Conclusions: Both stems achieved satisfactory 10-year outcomes. The Elite Plus stem showed more frequent loosening and radiolucent lines, whereas the C-stem demonstrated a stable cement-bone interface but had several PPF cases. Design differences likely contributed to these variations in outcomes.