Analysis of migration of the Nanos® short-stem hip implant within two years after surgery
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Short-stem implants provide a bone-preserving alternative in total hip arthroplasty. However, some evidence exists that the smaller implant-bone contact surface may compromise primary stability and impair osseo-integration. The purpose of this study was to analyse the migration characteristics of the Nanos® short stem over two years by means of model-based roentgen stereophotogrammetric analysis (MBRSA).
Eighteen patients aged 53.6 ± 7.2 years were included. After being treated with a Nanos implant, 14 patients were followed-up radiologically at three, six, 12 and 24 months by means of MBRSA. Early implant migration was calculated. Clinical data have been assessed in addition.
Highest translational migration was observed with a mean value of –0.22 ± 0.39 mm along the proximo-distal axis after three months and highest rotational migration with 0.8 ± 3.2° also around the y-axis after two years. The resulting total migration was 0.46 ± 0.31 mm, with the largest proportion occurring within three months after surgery (0.40 ± 0.34 mm).
The Nanos short-stem hip implant shows only a slight initial migration within three months after implantation, followed by secondary stabilisation. These results suggest both good primary stability and osseo-integration, suggesting a low risk of aseptic loosening.
KeywordsRSA Total hip arthroplasty Short stem Migration
The authors wish to thank Christina Keller for processing the RSA radiographs. Smith & Nephew Orthopaedics AG (Baar, Switzerland) acted as the sponsor of this study, granting financial compensation for expenses. The company took part neither in analysis and interpretation of data nor in preparation of the manuscript. None of the authors had a further conflict of interest that may have biased the study.
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