Management of fractures of the long bones of eight cats using external skeletal fixation and a tied-in intra-medullary pin with a resin-acrylic bar.

CASE HISTORY AND CLINICAL
FINDINGS: Eight feline patients with fractures of the femur, tibia or humerus were presented non-weight-bearing, with varying degrees of soft tissue and concurrent injury. Five fractures were comminuted, two were open fractures and there was one malunion. TREATMENT: Fracture repair was performed in each case using a low-cost resin-acrylic external skeletal fixator (ESF). An open, limited open, or 'open but do not touch' (OBDNT) approach allowed intra-medullary (IM) pinning of the major fragments, establishing axial alignment and countering bending stress. Application of a unilateral, uniplanar (Type IA) ESF using small diameter half-pins provided stabilisation against rotational and compressive forces. The half-pins and IM pin (tied-in) were incorporated into a composite bar with the resin-acrylic. The single humeral construct incorporated a transcondylar pin into a Type I-II design.
RESULTS: Seven cats, including all five comminuted fractures, had uncomplicated fracture healing. Median time to complete removal of the construct was 7 (range 5-12) weeks. In the eighth cat, an open fracture developed into a non-union, which required revision with a plate and bone graft. This cat and six others available for follow-up (median 6 months) were reported by their owners to enjoy normal activity. Two had a mild, intermittent lameness, one had a mild but persistent lameness, and four were sound. Six out of seven owners rated the appearance of their pet's limb as normal. CLINICAL RELEVANCE: The resin-acrylic ESF/tied-in IM pin construct was versatile and lightweight and allowed even highly comminuted non-load-sharing fracture configurations to be stabilised successfully using a biological strategy. Failure of the pin/acrylic interface did not occur and the frames provided sufficient strength as evidenced by healing without failure of the bar in these cases. A resin-acrylic ESF construct is inexpensive and affords the occasional orthopaedist the means to provide rotational stability when IM pinning has been used as the primary mode of fracture repair for short-oblique and transverse fractures. An extensive and costly clamp/bar inventory is not required, and there is greater flexibility for the orientation and placement of fixation pins than allowed by traditional linear bar systems.