Summary

Objectives: Currently available synthetic void fillers are indicated for bony voids or gaps that are not intrinsic to the stability of the structure. Jax™ TCP (tricalcium phosphate) is an osteoconductive bioceramic fabricated into 4 mm granules with a unique interlocking form, promoting structural integrity while allowing bone ingrowth. The objective of this study was to assess bone ingrowth using a large, critically sized, femoral defect. Methods: A 5 cm segmental ostectomy was created in the mid-diaphysis of 16 adult ovine femora. A stainless steel intramedullary nail was introduced and locked with two proximal and two distal fully-threaded locking screws. Each defect was surrounded with a resorbable macroporous poly (L-lactide-co-D,L) lactide mesh acting as graft containment. Treatment groups (n=4) were as follows: 1) Empty defect; 2) Morselized cortical bone; 3) Cortical strut; 4) Jax TCP. Serial radiographs were taken postoperatively and at two, four and six months. Femora retrieved at necropsy (six months) underwent computed tomography for volumetric analysis followed by histological assessment of the biological response. Results: Little bone was apparent in the empty defect group, whereas significant bone was evident in both autograft groups and the Jax TCP group. Three-dimensional CT reconstructions and volumetric analysis were in close agreement with the radiographic findings. Clinical significance: Jax TCP bone graft substitute has been proven to be effective in the healing of a large, critically sized, contained segmental defect. The healing observed was superior to that of cortical struts and the new bone laid down had similar radio-opacity to autograft.