Studies on Mechanical Strength of Bone: II.Torsional Strength of Cortical Bone after Rigid Plate Fixation with and without Compression

The Healing of Experimental Fractures by Compression Osteosynthesis: I.Torsional Strength

“…From 9 to 24 weeks postoperatively, the values for maximum torque capacity and energy absorption decreased, whereas torsional rigidity seemed to reach a steady state without significant changes after 9 weeks. Similar observations have been reported after rigid plate fixation of intact cortical bone (Stromberg & Dalen 1976, Paavolainen et al 1978a.…”

“…Porotic transformation induced by the stress protection properties of the rigid plate has been reported by some investigators (Uhthoff Sz Dubuc 1971, Gordes et al 1975, Woo e t al. 1976, Paavolainen et al 1978b. Uniform morphological changes have been reported after fixation of the plates in both intact and osteotomized bones, indicating that the main factor producing these untoward changes in the bone is not the fracture healing, but the rigidity of the implant (Slatis et al 1978).…”

Effect of Instability on Experimental Fracture Healing

“…A rigid immobilization protects bone from normal loading, and numerous reports have been given that show cancellous transformation and weakening of existing cortical bone after plate osteosynthesis (Tonino et al 1976, Woo et al 1976and Paavolainen et al 1978. It is probable that the same principle applies to new bone in the 34' process of osteogenesis, stress protection giving a slow rate of healing.…”

Fracture Healing After Rigid Intramedullary Nailing in Rats

“…Classification in stages of healing can not therefore be made (White et al 1977). According to previous reports on pre-existing cortical bone after stress protection, the finding of weak and brittle callus tissue in the cases with rigid nailing might be explained by the presence of a mature bone substance in amounts smaller than normal and arranged so that the outer bone limits are close to normal (Uhthoff & Dubuc 1971, Matter et al 1974, Strtamberg et al 1975, Tonino et al 1976, Paavolainen et al 1978, Uhthoff et al 1981. The increase in callus area in our study compared to that of normal bone implies an increase in area moment of inertia that would give abnormally high values for stiffness and strength if the callus consisted of qualitatively normal bone.…”

“…Axial compression or distraction along the plate does not appear to influence the occurrence or extent of weakening caused by bone resorption under the plate. The quality of the remaining bone substance is believed to be unchanged (Uhthoff & Dubuc 1971, Matter et al 1974, Stremberg 1975, Tonino et al 1976, Woo et al 1976, Paavolainen et al 1978, Uhthoff et al 1981. Stress protection may be less pronounced in intramedullary nailing, but some weakening of cortical bone has been reported (Klopper & Tonino 1980).…”