Abstract
Introduction
Negative remodelling of the femoral cortex in the form of calcar resorption due to stress shielding and cortical hypertrophy at the level of the tip of the implant, due to distal load transfer, is frequently noted following cemented total hip replacement, most commonly with composite beam implants, but also with polished double tapers. The C-stem polished femoral component was designed with a third taper running from lateral to medial across and along the entire length of the implant, with the aim of achieving more proximal and therefore more natural loading of the femur. The hoop stresses generated in the cement mantle are transferred to the proximal bone starting at the calcar, which should theoretically minimise stress-shielding and calcar resorption, as well as reducing distal load transfer, as signified by the development of distal femoral cortical hypertrophy.
Materials/Methods
We present the results of a consecutive series of 500 total hip replacements performed between March 2000 and December 2005 at a single institution, using a standard surgical technique and third generation cementing with Palacos-R antibiotic loaded cement. Data was collected prospectively and the patients remain under annual follow-up.
500 arthroplasties were performed on 455 patients with an average age of 68.3 years (23–92). 77 patients have died (73 arthroplasties) and the average duration of follow-up for the entire series is 81 months (52–124).
Results
Only 2 femoral implants have been revised - one for deep sepsis and the other as part of a revision procedure for a loose acetabulum, although the femoral component itself was not loose. One implant is currently loose following a periprosthetic fracture treated by internal fixation, but none of the other remaining implants demonstrates any progressive radiolucencies in any Gruen zones, or any features suggestive of current or future loosening. Rounding of the calcar has been observed, but there have been no cases with obvious loss of calcar height and no cases of distal femoral cortical hypertrophy.
Conclusion
The C-stem femoral component has therefore performed well in clinical practice and the objective of eradicating negative bone remodelling has been achieved. The study is ongoing
