Question: In patients receiving a total knee prosthesis, does intraoperative treatment with a bisphosphonate reduce prosthesis migration after surgery?
Design: Randomized (allocation concealed)*, blinded (surgeon, patients, and radiostereometry technician) controlled trial with 24-month follow-up.
Setting: A university hospital in Sweden.
Patients: 50 patients who were 60 to 75 years of age and who had gonarthrosis (Ahlbäck stages 3 to 5) and were scheduled to receive a NexGen (Zimmer, Warsaw, Indiana) cemented knee prosthesis. Exclusion criteria were cortisone or bisphosphonate medication, rheumatoid arthritis or other skeletal systemic illness, or generally poor health. 48 patients (96%) completed the study.
Intervention: Patients were allocated to local treatment with ibandronate (n = 25) or placebo (n = 25). The bone surfaces were cleaned with use of high-powered lavage. The porous tibial bone surface was dried, and either 1 mL of ibandronate solution or 1 mL of saline solution was poured onto it with use of a syringe. After 1 minute, cementation was started.
Main outcome measures: The primary outcome was maximal total point motion (MTPM) of the prosthesis (migration) measured by radiostereometry at each follow-up time point. Secondary outcomes were translation along the y-axis (sinking) and rotation around the transverse and sagittal axes.
Main results: MTPM of all time points combined was analyzed by repeated measures analysis of variance and showed that migration was significantly reduced with ibandronate (p = 0.006), with the greatest effect occurring at 6 months (Table). Ibandronate also significantly reduced prosthesis translation along the y-axis (p = 0.009). At 6 months, rotation was significantly reduced with ibandronate around the transverse (p = 0.04) and sagittal (p = 0.02) axes; the difference was not significant at later time points.
Conclusion: In patients receiving a total knee prosthesis, intraoperative treatment with ibandronate reduced prosthesis migration after surgery.
This well-designed study by Hilding and Aspenberg, with good randomization and blinding techniques as well as valid outcome measures, addresses a question of clinical interest—namely, tibial baseplate micromotion and the potential for aseptic loosening. The authors' application of bisphosphonate directly to the freshly cut, cleaned tibial bone surface allows for maximal drug-binding and the potential benefit of inhibited osteoclastic resorption of necrotic bone at the interface, while taking advantage of the drug's anabolic effect on osteoblasts. Background data in animal studies corroborate that locally infused bisphosphonate around implants may prevent periprosthetic bone loss.
However, based on the Swedish Registry data, aseptic loosening is a relatively rare cause of early failure of cemented total knee prostheses. A recent study showed survival with respect to aseptic loosening of 1000 cemented total knee prostheses at 15 years was 98.8%1. In fact, the clinical relevance of the described technique may be better applied to cementless fixation. Furthermore, consideration must also be given to the possible negative effect on the mechanical properties of local bone. Longer-term follow-up is clearly required to demonstrate how bone mineralization is affected, because a reduction in ductility would result in bone that is more prone to fracture and, possibly, implant loosening.
While this study is of interest, the low prevalence of aseptic loosening makes the sample size too small to demonstrate any relevant differences. A larger sample size, followed over a much longer duration, will be required prior to making definitive statements regarding the benefits of local bisphosphonate application and before making recommendations regarding the application to clinical practice.
Vessely MB, Whaley AL, Harmsen WS, Schleck CD, Berry DJ. Long-term survivorship and failure modes of 1000 cemented condylar total knee arthroplasties. Clin Orthop Relat Res.2006;452:28-34.45228
2006
[PubMed][CrossRef]