Abstract 36

ULNA DEFECT HEALING WITH A BONE GRAFT SUBSTITUTE AND LOW INTENSITY PULSED ULTRASOUND (LIPUS)

Stephen PC, Neichoda B, Auld J, Langdown A, Bruce W, Chen J, Yu Y, Pounder N, Walsh, WR

Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Sydney, Australia

The potential synergistic effect of LIPUS and bone graft substitutes to improve bone defect healing was explored in this study.

A critical defect model in the adult rabbit ulna was used to compare healing with a tricalcium phosphate bone graft substitute (JAX TCP, Smith & Nephew) and LIPUS. A 1.5 cm defect was made in the right ulna of 18 NZ White Rabbits, and filled with JAX TCP. Half were treated with LIPUS for 20 minutes/day (n = 9). Animals were sacrificed at 4 weeks (n = 3) and 12 weeks (n = 6).

Ulnas were faxitroned, and graded for evidence of implant resorption and new bone formation. BMD was calculated, and analysed with a 2-way ANOVA. Routine histology (H&E and Trichrome) and immunohistochemistry (Type I collagen, VEGF, PCNA and CBFA-1) was performed.

Defects filled with JAX TCP and treated with LIPUS demonstrated significant amounts of new bone formation compared to controls at 4 and 12 weeks on radiographic analysis. DEXA data revealed a significant increase in BMD with LIPUS treatment at 4 weeks (p<0.05); no difference was observed at 12 weeks. Histological analysis at 4 and 12 weeks confirmed the radiographic findings. Immunohistochemistry confirmed a type I collagenous matrix between the JAX TCP particles in all animals. VEGF, CBFA-1 and PCNA levels were elevated in the LIPUS treated animals compared to controls.

The use of low intensity pulsed ultrasound in combination with bone graft substitutes may offer a viable treatment option in the repair of bony defects.

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