title: Effects of instability on fracture healing in the rat.
abstract: The effect of bending and rotational instability on the healing of a femoral osteotomy was studied in rats using intramedullary fixation with nails made of either steel or flexible polyacetal. All osteotomies were made rotationally unstable by reaming the medullary cavity to a diameter wider than the nails. At 16 weeks, four osteotomies had healed, and 17 had not healed. However, bending tests gave higher values for strength and energy absorption in non-unions with flexible as compared to Stiff nails. Rotational instability thus caused a high rate of non-union in the present model, which has given safe healing when the osteotomy has been stabilized for rotation. Flexible nailing increased strength and energy absorption in bones with non-union, but did not affect the incidence of healing.
mesh_terms: D000080:Acetals; D000818:Animals; D001835:Body Weight; D001858:Bone Nails; D005264:Femoral Fractures / Q000503:physiopathology* / Q000601:surgery; D005594:Fracture Fixation, Intramedullary; D005599:Fractures, Ununited / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D010027:Osteotomy; D011108:Polymers; D051381:Rats; D011919:Rats, Inbred Strains; D013193:Stainless Steel; D013314:Stress, Mechanical; D014945:Wound Healing
chemical_list: D000080:Acetals; D011108:Polymers; D013193:Stainless Steel; C016067:polyacetal