Abstract
The fully hydroxyappatite (HA) coated tapered collarless femoral stem has been available worldwide for more than 20 years. However, in Thailand this design became available in 2007. In uncemented collarless tapered and HA coated designs, axial subsidence is a sign of early failure of the implant. This leads to stem instability, loosening and dislocation. To achieve vertical stability, the surgeon should use the correct surgical technique, accurate instrumentation, appropriate stem size and fill in the femoral canal before biologic fixation occurs. This study addresses the axial subsidence of the design.
Methods
46 consecutive total hip arthroplasties with fully HA coated tapered collarless femoral stem (Corail, DePuy) were performed between July 2007-November 2009 by a single surgeon. Patients with at least 6 months follow-up were included in this study. This involved 39 stems. The average follow-up was 11.86 months (6–24 months). The average age at the time of surgery was 58.6 years (37–83 years)
Results
25 stems (64%) had no evidence of subsidence. 14 stems (36%) had some subsidence. The average axial subsidence was 0.68 mm. The femoral canal shape was identified by canal flare index and classified to stovepipe in 12 cases, normal in 20 cases and Champagne –flute in 7 cases. The average axial subsidences at the end of the follow-up period were 0.67 mm, 0.8 mm and 0.25 mm respectively. All cases had no signs of loosening. All subsidences occurred on the first 3 months and no further subsidence was detected at 6 months or more. 12 cases (30%) were aged 60 years or older at time of surgery. In this group, 6 cases (50%) had stovepipe femoral stems (canal flare index <3.0).
Conclusion
The fully hydroxyappatite coated tapered femoral stem design shows minimal axial subsidence within the first 3 months after full stability after 6 months.
