Femoral Neck Preservation and Diaphyseal Invasion Comparing a Calcar-Metaphyseal Short Stem with its Homonymous Standard Femoral Stem. A Radiographic Study.

BACKGROUND: We aim to compare the preoperative planning radiographs of 50 patients in whom both a short stem and its homonymous standard version were programmed, focusing on the preservation of the neck and the invasion of the femoral shaft. The secondary objective was to evaluate the 50 preoperative radiographs with the 50 postoperative radiographs in which the short stem was implanted, measuring the real invasion of the diaphysis and the real preservation of the femoral neck. MATERIAL AND METHODS: We measured cut level at the femoral neck and diaphyseal invasion in 50 preoperative x-rays where an Alteon Neck Preserving Stem (ANPS) was templated and we compared it with 50 preoperative x-rays where an Alteon Taper Wedge Stem (ATWS) was templated. After surgery, we compared both parameters previously measured in the preoperative x-rays with the 50 postoperative radiographs where the short stem was implanted obtaining the real bone preservation at the femoral neck and the real diaphyseal invasion length. RESULTS: For templating comparison, mean bone preservation at the femoral neck was 14.87mm (SD 3.64) for the ANPS group and 9.94mm (SD 8.39) for the ATWS group (p <0.001). The mean diaphyseal bone invasion was 47.21mm (SD 5.89) and 76.77mm (SD 8.39) for ANPS and ATWS respectively (p <0.001). After surgery, the mean postoperative bone preservation at the femoral neck was 15.08mm (SD 3.1) with a mean of 0.17mm (SD 0.51) more preservation in the preoperative group. CONCLUSION: 1. ANPS allow bone preservation with limited diaphyseal invasion when compared with his homonymous ATWS in the preoperative templates. 2. ANPS showed a good correlation between preoperative radiographs and real bone preservation of the femoral neck and invasion of the femoral shaft.

Primary outcomes of a femoral neck-preserving stem: a multicentre clinical-radiological analysis at 5-year follow-up.

PURPOSE: The aim of this prospective study was to evaluate the clinical-radiological outcomes of the Alteon Neck Preserving Stem (ANPS) (Exactech, Gainesville, FL, USA) implanted in four different centres by five senior hip surgeons with a minimum of 5 years of follow-up. MATERIAL AND METHOD: We conducted a multicentre prospective study that analysed 155 consecutive total hip replacements during 2014. We performed clinical-radiological analysis measuring Harris Hip Score (HHS), subjective satisfaction evaluation, radiolucencies, position of components, limb length discrepancy, heterotopic ossification, medical and surgical complications and a survival analysis at 5 years follow-up. RESULTS: Thigh pain was reported in 5 cases (3.2%), 2 of which reported mild pain, 2 moderate, and 1 severe. In 2 cases, subsidences of 3 mm were detected in the first scheduled X-ray, both related to intraoperative fractures with no progression after 3 months. The overall complication rate was 5.8% and 6 of the 9 complications were in the first 30 cases. Mean HHS improved from 42.9 points (range 37.2-55.7 points) preoperatively to 94.9 on average (range 87-98) at the end of the follow-up (p <0.01). Subjective evaluation was excellent in 130 (83.87%) cases and good in 25 patients (16.13%). CONCLUSIONS: The clinical-radiographic results of ANPS THR are satisfactory. The mid-term results are promising. However, long-term follow-up studies are necessary to confirm the validity of the concept.