title: Influence of systemic bisphosphonate treatment on mechanical properties of BMP-induced calluses in a rat fracture model: comparison of three-point bending and twisting test.
abstract: The combination of autograft, BMP and bisphosphonate has been shown to produce strong calluses. In this study, without autograft we investigate the effect of bisphosphonate treatment on BMP-induced calluses, both in bending and in rotation. Sprague-Dawley rats (n = 42) underwent femoral osteotomy and BMP-7 treatment. At 2 weeks an injection of saline or bisphosphonate was administered. The animals were sacrificed after 6 weeks. Both femurs were tested in either three-point bending or twisting. All femurs healed. BMP + bisphosphonate-treatment led to larger calluses (p < 0.05) and in three-point bending, higher ultimate force (p < 0.01) and greater stiffness (p < 0.05) than BMP alone. The BMP + bisphosphonate group was nearly 60% stronger than controls, while the BMP group did not reach the strength (p < 0.05) nor stiffness (p < 0.01) of the controls. In the twisting test, similar trends were found but less pronounced. Three-point bending produced transverse callus associated fractures, whereas the twisting test produced spiral fractures, located in the structurally weaker distal femur. BMP + bisphosphonate-treatment produces calluses that are mechanically superior to calluses induced by BMP alone, when tested both in three-point bending and in twisting. For the mechanical evaluation of pharmacologically enhanced calluses with breaking strengths exceeding the native bone, the bending test is recommended.
authors: Department of Orthopaedics, Clinical Sciences, Lund University, Lund, Sweden.
authors: Per
authors: P
authors: Bosemark
authors: Hanna
authors: H
authors: Isaksson
authors: Magnus
authors: M
authors: Tägil
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D055419:Bone Morphogenetic Protein 7 / Q000627:therapeutic use*; D002146:Bony Callus / Q000502:physiology*; D004164:Diphosphonates / Q000627:therapeutic use*; D005264:Femoral Fractures / Q000601:surgery; D007093:Imidazoles / Q000627:therapeutic use*; D008297:Male; D010027:Osteotomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D055114:X-Ray Microtomography; D000077211:Zoledronic Acid
chemical_list: D050071:Bone Density Conservation Agents; D055419:Bone Morphogenetic Protein 7; D004164:Diphosphonates; D007093:Imidazoles; D000077211:Zoledronic Acid
keywords: anisotropy; bisphosphonates; bone morphogenic protein; callus; callus density