34th Annual Scientific Meeting proceedings

Objectives:

Introduction:

Sheep are commonly used in fracture research, as their size and bone healing are translational to humans. Current tubular bone fracture models involve major weightbearing bones such as the tibia, with postoperative management involving extensive co-aptation and/or sling suspension. Consequently, freedom of movement is significantly impaired, impacting the welfare of the animals.

Objectives:

The study aimed to develop a new tubular bone fracture model using off-loading and bandages or half-limb casts to protect the fracture repair and to use a multimodal approach for evaluating the welfare of the sheep.

Methods:

12 healthy, 5-year-old sheep underwent surgery of both proximal lateral phalanges of the thoracic limbs and were observed for 16 weeks. Four sheep had mid-diaphyseal ostectomies (3 and 6 mm gap) performed, eight sheep had mid-diaphyseal osteotomies performed in combination with a unicortical 4.5 mm drill hole. All fractures were repaired with a single 1.5 mm, 5 or 6-hole LCP. A wooden block was applied under the medial claw of both front limbs to off-load the operated toes. Welfare was monitored by pain scoring, facial expression assessment, and activity tracking. 

Results:

All ostectomies resulted in non-healing (i.e., critical size defect model), while osteotomies showed radiographic signs of healing within 6-8 weeks. The sheep ambulated well and showed mild signs of pain.

Conclusions:

We developed two ovine fracture models useful for testing osteosynthesis materials and/or bone cements or fillers. The welfare of the sheep was good. The main drawbacks of the models were hoof block maintenance and occasional screw breakage.