Mid-term gender-specific differences in periprosthetic bone remodelling after implantation of a curved bone-preserving hip stem.

BACKGROUND

The implant-specific periprosthetic bone remodelling in the proximal femur is considered to be an important factor influencing the long-term survival of cementless hip stems. Particularly data of gender-specific differences regarding bone-preserving stems are very rare in literature and mainly limited to short-term investigations. Therefore, we investigated at mid-term one arm of a prospective randomised study to evaluate if there is an influence of gender on implant-specific stress shielding after implantation of a curved bone preserving hip stem (Fitmore) 5 years postoperatively.

HYPOTHESIS

We hypothesised there will be no gender-specific differences in periprosthetic bone remodelling.

PATIENTS AND METHODS

A total of 20 female and 37 male patients underwent total hip arthroplasty using the Fitmore stem. Clinical, radiological as well as osteodensitometric examinations were performed preoperatively, 7 days and 3, 12 and 60 months postoperatively. Clinical data collection included the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and the Harris Hip Score (HHS). Periprosthetic bone mineral density (BMD) was measured using Dual Energy X-ray Absorptiometry (DXA) and the periprosthetic bone was divided into 7 regions of interest (ROI) for analysis. The results at 3, 12 and 60 months were compared with the first postoperative measurement after 7 days to obtain a percentage change.

RESULTS

Periprosthetic BMD showed a decrease in all 7 ROIs for both groups 5 years postoperatively referred to the baseline value, except ROI 3 (0.8%, p=0.761), representing the distal lateral part of the stem, and ROI 5 (0.3%, p=0.688), representing the distal medial part of the stem in the male cohort. Significant gender differences were found in ROI 1 (-16.0% vs. -3.5%, p=0.016) and ROI 6 (-9.9% vs. -2.1%, p=0.04) in favour of the male patients. Clinical results showed no significant gender differences 5 years postoperatively with regard to WOMAC (mean 0.4 (±0.8, 0-3.3) in women vs. 0.3 (±0.8, 0-4.2) in men, p=0.76) and HHS (mean 93.0 (±9.7, 66.0-100.0) in women vs. 93.9 (±11.5, 53.0-100.0) in men, p=0.36).

CONCLUSION

Proximal stress shielding was observed independent of gender 5 years postoperatively. However, there was a significantly lower bone loss proximal lateral and medial below the calcar in male patients, indicating a more physiological load transfer. [ClinicalTrials.gov identifier: NCT03147131 (Study ID D.3067-244/10). Registered 10 May 2017 - retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03147131?term=Bieger&draw=2&rank=1] LEVEL OF EVIDENCE: IV; prospective study without control group.