Alendronate did not inhibit instability-induced bone resorption. A study in rats

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Pharmacology

Background:

• Periprosthetic osteolysis is a significant complication following orthopedic implant surgery.
• Bisphosphonates, such as alendronate, are known to inhibit osteoclastic bone resorption.
• Alendronate has been proposed as a potential treatment to mitigate periprosthetic osteolysis.

Purpose of the Study:

• To investigate the efficacy of alendronate in preventing bone resorption at an unstable implant-bone interface.
• To evaluate the systemic effects of alendronate administration on bone metabolism.

Main Methods:

• A rat model with a surgically implanted plate on the tibia was used.
• An unstable implant-bone interface was created by inducing a sliding motion of the implant.
• Alendronate was administered systemically via osmotic minipumps at a dose of 0.063 mg/kg/day.
• Bone resorption was assessed using histomorphometry.
• Systemic effects were evaluated by measuring the ash-weight of the contralateral tibia.

Main Results:

• Alendronate treatment did not inhibit the bone resorption induced by implant instability at the interface.
• Histological analysis revealed bone resorption and the formation of a loosening membrane at the unstable interface.
• A significant increase of 43% in ash-weight of the contralateral tibia was observed in the alendronate-treated group (p = 0.0001).
• Histological changes in the metaphyseal bone of the contralateral tibia corresponded to the increased ash-weight.

Conclusions:

• Alendronate is ineffective in preventing bone resorption at an unstable implant-bone interface.
• Alendronate demonstrates systemic effects, leading to increased bone mass in non-stressed skeletal sites.
• Further research is needed to understand the localized vs. systemic effects of bisphosphonates in orthopedic contexts.