Abstract
Background and aim
Despite good survivorship analysis for most uncemented tapered straight stems, new proposals modifying stem design in total hip replacement (THR) are being introduced in order to facilitate femoral revision surgery.
We have evaluated the clinical and radiological results of four different designs of uncemented tapered straight stems implanted in our institution in order to assess: operative complications, clinical results, survivorship analysis for aseptic loosening and radiographic findings
Methods
1008 hips implanted from 1998 to 2006 were prospectively followed for a mean of 12 years (range, 10 to 17). Four uncemented femoral designs employing a tapered straight stem were included: 209 Alloclassic stems, 420 Cerafit, 220 SL-Plus and 159 Summit. All hips had a 28 or 32 mm femoral head, and polyethylene (PE)-on metal or ceramic-on-ceramic bearing surface. Radiological femoral type, stem position, femoral canal filling at three levels and the possible appearance of loosening and other bone remodelling changes were recorded in all hips.
Results
The rate of intra- and post-operative peri-prosthetic fractures ranged from 0 to 2.5%. No thigh pain was reported in unrevised patients. Among all groups, a total of 15 stems were revised for any cause. The revision rates for any cause at 12 years ranged from 97.1 to 99.3%. (p=0.1). 10 femoral components were revised for aseptic loosening: 6 Alloclassic stems with PE liner sterilized by Nitrogen and 3 SL-Plus stems with standard PE. No revision for aseptic loosening was found in the other designs. The survival rate for stem aseptic loosening was 97.1% (95% CI 95.6–100) for the Alloclassic group at 17 years and 98.2% (95% CI 96.2–100) for the SL-Plus at 14 years. The percentage with a neutral stem position was lower in the Alloclassic and SL-Plus groups (p=0.04). We found that femoral canal filling depended on stem group and stem position at three levels A, B and C (p<0.001). Femoral canal filling was greater in the SL-Plus group at three levels than the others (p<0.001). Bone remodelling changes were more frequent in the SL-Plus group, radiolucent lines (p<0.001) and cortical hypertrophy (p<0.001).
Conclusion
Uncemented tapered straight stems consistently provide excellent clinical outcome and bone fixation. Newer proposals must consider these results, avoiding changing successful characteristics and concentrate on improving the less successful aspects
