Transverse periosteal sectioning and femur growth in the rat.

Circumferential cuts through the periosteal covering of long bones have been demonstrated to transiently increase epiphyseal growth. This effect appears to be independent of vascular changes accompanying surgery and has been hypothesized to relate to releasing tension in the periosteal envelope. This study was designed to address problems of previous investigations by controlling for the effects of the surgical procedure and by using regression analyses to analyze intra- and interanimal variations in the length and proportionality of the femur in experimental, sham, and control Sprague-Dawley male rat littermates. Experimental animals received circumferential periosteal sectioning of the right femur and no operation to the left limb. A sham operation without periosteal sectioning was performed on the right femur in the sham group. Right to left differences were analyzed using two multiple regression models; one involved three absolute length measurements as the dependent variables, while the other used the three ratios of these length measurements as the dependent variables. The ratio measures were utilized to reflect changes in bone proportionality. Circumferential periosteal section was followed by an alteration in the shape of rat femurs at 2 weeks postsurgery with a slight retardation of the length dimension from medial epicondyle to head of the femur and an overgrowth of the length dimension from the lateral epicondyle to the greater trochanter. The sham procedure produced a proportional decrease in all length measurements. The experimental procedure was also associated with surface bone apposition at the site of section. At 3 weeks postsurgery, normalization of bony contours between sham, experimental, and control groups had occurred; however, there were still some statistically significant decreases of length dimensions in the sham and experimental groups. In the experimental group the length measurement involving the weight-bearing head of the femur remained reduced at 3 weeks postsurgery. It is hypothesized that the functional demands of the long bone play an important role in the effect of periosteal regulation on growth. In situations where a normal tensive force is exerted on the bone, the periosteal envelope will act to restrain epiphyseal growth. When the bone is under a normal compressive force the release of periosteal tension is not a quantitatively significant stimulus to epiphyseal growth and the effects of surgical intervention and muscle trauma will play a more important role in the growth response of the epiphyses.