A biomechanical study of the effects of growth hormone in experimental fracture healing

Abstract

In 65 mature Wistar rats a Kirschner wire was introduced into the medullary cavity of each femur. A closed transverse mid-shaft fracture of one femur was produced by a three-point bending technique. Subsequently the mechanical characteristics of the healing fracture, including the torque and angle of twist required to take the callus to its yield point and to ultimate failure, were compared with those for the opposite femur of each rat. Controls were killed in groups at two, three, four, five and seven weeks. Test animals were given bovine growth hormone in a daily dose of five milligrams before being killed in groups at two, three and four weeks. A significant increase in torque index was found in the two-week group of test animals but not in subsequent groups. No evidence was found that growth hormone given alone could produce an overall shortening of the healing time in fresh fractures.

Influence of Age on Mechanical Properties of Healing Fractures and Intact Bones in Rats

“…As observed by Northmore-Ball et al (1980), this was transient in young rats. The increased stiff-ness was probably caused by the large polar moment of inertia and the increasing mineralization of the callus, rather than the callus tissue being stiffer than normal bone material.…”

Growth Hormone and Bone

“…A few negative studies in rabbits [71] and rats [72] are in contrast with positive effects of GH therapy on healing of experimental frac tures of young rats [73][74][75][76]. Results in other animals are also contradictory [76], Systemic administration of bio synthetic IGF|, however, was not able to enhance exper imental fracture healing of adult rats [77], On the con trary, local infusion of IGF) into one leg clearly in creased the osteoblast number (+ 13%) while decreasing the osteoclast number (-13%) and increased cortical and trabecular bone formation in the treated leg of intact rats [78,79], The potential application of either GH, GHRH or IFG| for treatment of osteoporosis or fracture repair is therefore still in an early experimental stage.…”

Dose response of growth hormone on fracture healing in the rat

“…In contrast, Northmore-Ball et al (1980) did not find any effect on the healing of stabilized femoral fractures of 5 mg/day of bovine growth hormone (specificity not stated) given to mature rats. Neither did Harris et al (1975), who investigated fractures in rabbits receiving growth hormone (type not specified) 0.46 I.U./kg body weight/day for 10 to 50 days.…”