Recombinant growth hormone accelerates regenerate consolidation in distraction osteogenesis

Distraction osteogenesis is a good model for evaluation of fracture healing with intramembranous bone formation. The purpose of the present study was to investigate whether homologous GH has a stimulating effect on bone healing in distraction osteogenesis. The left tibiae of 30 micropigs were osteomized and distracted with an external fixator 2 mm daily over a period of 10 days. Animals were killed after an additional healing time of 10 days. The treatment group received 100 mu g r-pGH per kg bodyweight per day. A newly developed device allowed non-destructive torsional biomechanical evaluation of the regenerate strength as in vivo measurements. After killing, destructive torsional strength testing of the sites of distraction was performed. To determine the endocrine response to the administration of r-pGH, serum levels of IGF-I were determined. The non-destructive in vivo testing showed that torsional stiffness of the regenerate was significantly higher in the treatment group than in the control group. Final regenerate torsional failure load was 131 % higher and ultimate torsional stiffness was 231 % higher in the treatment group than in the control group. The mean serum level of IGF-I increased to 440 % of the preoperative base level in the treatment group and remained unchanged in the control group. Our data indicate that systemic administration of recombinant homologous growth hormone significantly accelerates ossification of bone regenerate in distraction osteogenesis.