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Open Access Research article

Bone mineral density of the proximal femur after hip resurfacing arthroplasty: 1-year follow-up study

Arja Häkkinen12*, Håkan Borg3, Mikko Hakulinen4, Jukka Jurvelin5, Esa Anttila6, Tapani Parviainen7 and Ilkka Kiviranta36

Author Affiliations

1 Department of Physical Medicine and Rehabilitation, Jyväskylä Central Hospital, Jyväskylä, Finland

2 Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland

3 Department of Orthopaedics and Traumatology, University of Helsinki, Helsinki, Finland

4 Department of Clinical Physiology and Nuclear Medicine, Imaging Center, Kuopio University Hospital, Kuopio, Finland

5 Department of Physics and Mathematics, University of Eastern Finland, Kuopio, Finland

6 Department of Orthopaedics and Traumatology, Jyväskylä Central Hospital, Jyväskylä, Finland

7 Department of Clinical Physiology Jyväskylä Central Hospital, Jyväskylä, Finland

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BMC Musculoskeletal Disorders 2011, 12:100  doi:10.1186/1471-2474-12-100

Published: 19 May 2011

Abstract

Background

Hip resurfacing arthroplasty (HRA) is considered a bone-preserving procedure and may eliminate proximal femoral stress shielding and osteolysis. However, in addition to implant-related stress-shielding factors, various patient-related factors may also have an effect on bone mineral density (BMD) of the proximal femur in patients with HRA. Thus, we studied the effects of stem-neck angle, demographic variables, and physical functioning on the BMD of the proximal femur in a one-year follow-up.

Methods

Thirty three patients (9 females and 24 males) with a mean (SD) age of 55 (9) years were included in the study. BMD was measured two days and 3, 6, and 12 months postoperatively and 10 regions of interest (ROI) were used. Stem-neck angle was analyzed from anteroposterior radiographs.

Results

Three months postoperatively, BMD decreased in six out of 10 regions of interest (ROI) on the side operated on and in one ROI on the control side (p < 0.05) compared to the second postoperative day. At 12 months, BMD had increased in 7 ROIs on the operated side and one ROI on the control side (all p < 0.001). Correlation was found between the stem-neck angle and BMD in ROIs 2, 3, 7, and 9 (r = 0.36 - 0.61). In multiple regression analysis, stem-neck angle, age, sex, body mass index, and walking distance did not explain the BMD changes.

Conclusions

After an early drop, the BMD of the upper femur was restored and even exceeded the preoperative level at one year follow-up. From a clinical standpoint, the changes in BMD in these HRA patients could not be explained by stem-neck angle or patient related factors.

Keywords:
bone remodeling; dual energy X-ray absorptiometry; stress shielding; stem-neck angle