Healing of canine femoral osteotomies. Effects of compression plates versus Eggers' plates

The effects of rigid self-compressing plates were compared with the effects of less rigid internal contact splints on the healing characteristics of osteotomized canine femora. Radiographically, the rigid fixation afforded by the compression plate produced accelerated healing as compared with the less rigid fixation obtained with splints at two to four months. At six months there was little or no difference between the two groups. Comparison of the material biomechanical properties of the healing femora suggested that the repair tissue formed early after compression plating was stronger than the callus tissue that surrounded the less rigidly fixed femora. A comparison of the structural biomechanical properties of the bones suggested, conversely, that a stronger whole bone resulted from the less rigid fixation splint. The histomorphometric data showed that some cortical bone was lost under both types of fixation plates. However, the patterns of loss were not comparable. Use of rigid internal fixation led to loss of cortical bone after four to six months, while the less rigid fixation obtained with the Eggers splint produced mild intracortical resorption only. These observations point to the desirability of rigid internal fixation early in the healing process and the possible benefit of decreasing the rigidity of the fixation device as healing proceeds.