Clinical and radiological outcomes of the SL-Plus stem with a minimum 10-year follow-up: a retrospective study.

Purpose: The SL-Plus cementless stem was introduced in 1993 as an evolution of the Alloclassic stem with some modifications. The aim of this study was to analyse if these modifications have any influence in clinical and radiological outcomes at minimum 10-year follow-up.

Methods: Sixty-eight consecutive implants (64 patients) were retrospective evaluated. The mean duration of clinical and radiographic follow-up was 12.2 years. There were 41 female and 23 male patients with a median age of 73.5 years. All complications and reinterventions were collected. Functional outcomes were assessed using the modified Harris Hip Score (mHHS). Radiographs were evaluated immediately after the operation, after a minimum 2-year follow-up and by the end of follow-up (time A, B and C, respectively).

Results: Two stems were revised, one due to periprosthetic fracture and one due to aseptic loosening with a cumulative probability of not having a stem revision for any reason of 97.2% at 12.2 years. Mean mHHS was 76.7 points at the latest follow-up. Significant differences were found in distal migration (time A: 5.9mm±6.7, B: 6.9mm±7.1 and C: 8.2mm±6.3; p=0.000) and varus angulation (time A: 0.0° ±2, B: 0.0° ±2 and C: 1.0° ±3; p<0.001), although these stems showed radiographic signs of osseointegration. Thirty-three hips (48.5%) showed any radiolucent line around the stem, most of them located the proximal femur (Gruen 1 and 7). Multivariate regression analysis showed lower mHHS scores in older patients (p=0.004) and female (p=0.00).

Conclusions: The modifications of the SL-Plus stem influence the long-term outcome of the implant regarding radiological results, particularly in progressive varus angulation and distal migration. However, our study has not been able to demonstrate any clinical repercussions: functional scores and survival free of all cause revision were favorable and comparable to previous reports.

Level of evidence: Therapeutic Level IV (Case Series).