Clinical outcome of design modifications to the CLS Spotorno Stem in total hip replacement

Abstract

Purpose: historically, the original CLS Spotorno Stem has demonstrated excellent survival. The design of this stem was recently modified, resulting in the introduction of a shorter, modular version (CLS Brevius). The purpose of the current study was to evaluate the functional, radiological and survivorship outcomes of the cementless CLS Brevius Stem in a multi-surgeon, single center, consecutive series study at two years post-surgery.

Methods: the Authors performed 170 total hip arthroplasties in 155 patients using the shorter, triple-taper stem design (CLS Brevius). The patients' diagnoses were primary hip osteoarthritis (OA) in 74.4%, secondary hip OA in 22.6%, and post-traumatic hip OA in 3%. All operations were performed through a mini-posterior approach, with the patient in the lateral decubitus position. The mean follow-up was 32 months (24-44 months). Outcome was assessed using the Harris Hip Score (HHS).

Results: the mean HHS improved from 32 preoperatively to 92 points at final follow-up, while the stem survival rate was 99.4%. Overall, the results were excellent in148 hips (87%), good in 14 hips (8.2%), fair in six hips (3.6%), and poor in two hips (1.2%). Intraoperative complications included a calcar fissure in three hips (1.7%). Correct femoral offset was reproduced in 97% while the planned center of hip rotation was achieved in 98%. Only one hip underwent early stem revision; this was due to major subsidence.

Conclusions: the modified CLS stem design showed excellent short-term results with a low rate of early postoperative complications. One of the main findings of this study was the high correlation between the planned femoral offset and center of hip rotation and the final radiographic measurements. This high reproducibility, which indicates the ability of the system to restore normal hip anatomy, is indeed due to the extensive modularity that characterizes this stem system. Long-term follow-up studies are necessary to fully compare the outcomes of the new design with its highly successful predecessor.

Level of evidence: Level IV, therapeutic cases series.

Keywords: CLS; arthroplasty; femoral stem; hip; osteoarthritis.

Fig. 1

The original CLS Stem (Zimmer) (A) and the modified CLS Brevius Stem (Zimmer) (B).

Fig. 2

Left hip. CLS Brevius Stem insertion: three longitudinal fins are present on the anterior and on the posterior surfaces of the proximal part of the stem.

Fig. 3

Right hip. During the acetabular component positioning phase, a tilt-meter is connected to the cup holder to allow the inclination of the implant to be adjusted for pelvic tilt.

Fig. 4

Left hip. A 65-year-old man received a CLS Brevius femoral stem and a Continuum acetabular component (Zimmer): A. Preoperative radiograph. B. Two-year follow-up radiographic evaluation.