Topical zoledronic acid decreases micromotion induced bone resorption in a sheep arthroplasty model

Abstract

Background: Initial micromotion of a total hip replacement is associated with aseptic loosening. The use of bisphosphonates could be one way to reduce peri-implant bone resorption induced by micromotion. Bisphosphonates compounds are inhibitors of bone resorption. The aim of this study was to investigate whether local treatment with bisphosphonate would reduce bone resorption and fibrous tissue around an experimental implant subjected to micromotion.

Methods: One micromotion implant were inserted into each medial femoral condyle in ten sheep. During each gait cycle the implant axially piston 0.5 mm. During surgery one of the femoral condyles were locally treated with 0.8 mg zoledronate. The other condyle served as control. Observation period was 12 weeks.

Results: Histological evaluation showed a fibrous capsule around both the control and bisphosphonate implants. Histomorphometrical analysis showed that 97% of the surface on both control and bisphosphonate implants were covered by fibrous tissue. However, the bisphosphonate was able to preserve bone in a 1 mm zone around the implants.

Conclusion: This study indicates that local treatment with bisphosphonate cannot prevent the formation of a fibrous capsule around an implant subjected to micromotion, but bisphosphonate is able to reduce resorption of peri-prosthetic bone.

Keywords: Animal; Arthroplasty; Bisphosphonate; Implant; Osseointegration.

Fig. 1

Schematic drawing showing implant position in the medial femoral condyle. Reproduced with permission from copyright holder/author

Fig. 2

Schematic diagram showing the specimen preparation. Each bone-implant specimen is embedded and cut into four slides for histomorphometrical analysis. Reproduced with permission from copyright holder/author

Fig. 3

Representative photomicrographs of samples from the same animal. The samples were stained with basic fuchsin and counterstained with 2% light green. Note the thick fibrous membrane around the control implant compared to the zoledronate implant. Solid bar = 1 mm. Dotted bar = 0.3 mm

Fig. 4

Tissue-volume fractions in a 0–1 mm zone around implants. Paired data connected by line