Evaluation of two dynamic axial fixators for large ruminants.

Objectives: To evaluate healing of a radial osteotomy repaired by application of dynamic axial fixation devices (DAF) in large ruminants.

Study Design: In vivo study of bone healing after application of 2 DAF types. Model I had 2 sidebars, each with a central cylindrical cuff (internally threaded) with 2 detachable connecting rods telescoping within the cuff. Model II had 2 side bars with 2 moveable clamps with multiple holes.

Sample Population: Bull calves (n=8; aged, 1.5-2.0 years; weighing, 175-250 kg).

Methods: A mid-diaphyseal radial osteotomy was repaired by use of a model I (n=4) or model II (n=4) DAF. Calves were monitored for weight bearing, stability of fixation, and radiographically for fracture reduction, alignment and healing at intervals for 6 months. Fixators were removed when there was radiographic evidence of healing.

Results: Both the fixators were well tolerated with free movement of adjacent joints. Fragment fixation was maintained until healing in all but 1 model I calf where failure occurred within 7 days. Model II DAF provided more rigid fixation as indicated by early full weight bearing and fracture healing with less callus formation. Functional recovery of repaired limbs occurred within 60 days in surviving calves.

Conclusions: Both bilateral DAFs were easy to apply; however, the model II DAF provided better fixation.

Clinical Relevance: The model II DAF made of low carbon steel was economical and may be useful for treating long bone fractures in large ruminants.