Abstract
Introduction
Varus malpositioning of femoral stems has been recognised as a poor prognostic feature with regard to loosening and failure of cemented composite beam implants, but there have been no published results of the long-term effect on taper-slip designs.
Objectives
To determine the results of varus placement of a polished triple tapered femoral stem.
Methods
We have prospectively analysed the results of 350 consecutive polished triple-tapered C-Stem implants performed on 322 patients between March 2000 and July 2004, using a standard posterior approach and Palacos-R cement. All patients underwent annual clinical and radiological review.
Results
The average duration of follow-up in surviving patients is 140 months (120–172 months).
There were 49 femoral implants in 49 patients implanted with more than 5 degrees of varus (14%) with respect to the long axis of the femur, and 14 in 14 patients in more than 5 degrees of valgus (4%). Alignment within 5 degrees of neutral was achieved in 82% of cases.
The average age in the varus group was 69.2 years (41–92), which was higher than in the neutral group (67.4 years: 25–89), more patients were male (49% v 36%) but the average BMI was similar (29 v 28). The average duration of follow-up was the same.
There was only one re-operation in the varus group, which was a revision for deep infection. There was one dislocation successfully treated by closed reduction and one acetabular component is currently loose.
In the neutral group there have been four dislocations, one of which required application of a PLAD; five revisions for aseptic loosening of the acetabular component associated with high wear rates, with a further three currently being loose; four intra-operative, undisplaced fractures of the greater trochanter; two peri-prosthetic femoral shaft fractures treated by internal fixation and two temporary nerve palsies.
There has been no aseptic loosening of the femoral components in either group.
Subsidence of the femoral stem within the cement mantle was noted in 96% of the entire series. There was no significant difference between the groups with respect to the degree of subsidence. In the varus group 78% subsided less than 2mm compared to 75% in the neutral group. None of the femoral implants in either group subsided more than 4mm and none demonstrated evidence of aseptic loosening or negative bone remodelling.
Conclusion
Varus implantation of the femoral component was more common in older, male patients, but there was no increased risk of subsidence or loosening at a minimum follow-up of ten years.
