A randomised trial comparing a short and a standard-length metaphyseal engaging cementless femoral stem using radiostereometric analysis.
This was a randomised controlled trial studying the safety of a new short metaphyseal fixation (SMF) stem. We hypothesised that it would have similar early clinical results and micromovement to those of a standard-length tapered Synergy metaphyseal fixation stem. Using radiostereometric analysis (RSA) we compared the two stems in 43 patients. A short metaphyseal fixation stem was used in 22 patients and a Synergy stem in 21 patients. No difference was found in the clinical outcomes pre- or post-operatively between groups. RSA showed no significant differences two years post-operatively in mean micromovement between the two stems (except for varus/valgus tilt at p = 0.05) (subsidence 0.94 mm (SD 1.71) vs 0.32 mm (SD 0.45), p = 0.66; rotation 0.96° (SD 1.49) vs 1.41° (SD 2.95), p = 0.88; and total migration 1.09 mm (SD 1.74) vs 0.73 mm (SD 0.72), p = 0.51). A few stems (four SMF and three Synergy) had initial migration > 1.0 mm but stabilised by three to six months, with the exception of one SMF stem which required revision three years post-operatively. For most stems, total micromovement was very low at two years (subsidence < 0.5 mm, rotation < 1.0°, total migration < 0.5 mm), which was consistent with osseous ingrowth. The small sample makes it difficult to confirm the universal applicability of or elucidate the potential contraindications to the use of this particular new design of stem.
University Hospital, 339 Windermere Road, London, Ontario N6A 5A5, Canada.
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McCalden
University Hospital, 339 Windermere Road, London, Ontario N6A 5A5, Canada.
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Korczak
University Hospital, 339 Windermere Road, London, Ontario N6A 5A5, Canada.
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Somerville
Western University, 1151 Richmond Street, London, Ontario N6A 3K7, Canada.
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Yuan
University Hospital, 339 Windermere Road, London, Ontario N6A 5A5, Canada.
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Naudie
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D059869:Radiostereometric Analysis
Radiostereometric Analysis; Short metaphyseal stem; Total Hip Arthroplasty