Homologous growth hormone accelerates bone healing--a biomechanical and histological study

The purpose of this study was to prove whether homologous growth hormone has a beneficial effect in the early phase of bone healing. Therefore the left tibias of 24 Yucatan micropigs were osteotomized and stabilized by plate fixation. The treatment group (12 animals) received 100 microg of recombinant porcine growth hormone (rpGH)/kg body w/day sc, whereas the control pigs (12 animals) received 1 ml sodium chloride as placebo. After a healing period of 4 weeks the animals were sacrificed and destructive torsional testing was performed. For histological evaluation 6 microm serial slices of the tibiae were stained with von Kossa. The total area of callus formation (CA) and the mineralized bone area (BA) were quantified by image analysis. The fraction of mineralized bone tissue within the callus area, the bone density (BD), was calculated as follows: BD = (BA/CA) x 100. Torsional failure load was 91% higher and torsional stiffness 61% higher in the treatment group than in the control group (P < 0.05). The histomorphometric measurements revealed an advance for the CA (GH: 127.6 +/- 38.9 mm(2); placebo: 75.9 +/- 50.7 mm(2); P < 0.005) as well as for the BA (GH: 89.3 +/- 25.8 mm(2); placebo: 55.9 +/- 38.5 mm(2); P < 0.001) for the GH-treated animals in comparison to the control animals. The BD was similar in both groups (GH: 70.6 +/- 8.4%; placebo: 74.0 +/- 6.24%; P = 0.28). These data indicate that administration of homologous GH stimulates callus formation and ossification in the early phase of bone healing, which consequently results in an increased mechanical strength and stiffness.