Effect of internal fixation on the strain environment of the canine femur.

Strain gauge technology and telemetric transmission were utilized to investigate the dynamic strain patterns along the cortical surface of bone and the response to internal fixation, in vivo. Application of a tension band plate resulted in conversion of normal tensile strain into compressive strain which verified the tension band principle of internal fixation. Creation of a transverse osteotomy did not alter this response, provided that the fragments were rigidly fixed. The plate caused an appreciable decrease in normal surface strain measured from the lateral and medial cortices, illustrating the concept of stress protection.