Mechanical testing of a steel-reinforced epoxy resin bar and clamp for external skeletal fixation of long-bone fractures in cats.

AIMS: To provide veterinarians with confidence when using a commercially available epoxy resin in external skeletal fixators (ESF), testing was conducted to determine exothermia during curing of the epoxy resin compared to polymethylmethacrylate (PMMA), the hardness of the epoxy resin as a bar over 16 weeks, and the strength of the epoxy resin bar compared with metal clamps in similarly constructed Type 1a ESF constructs simulating the repair of feline long bone fractures. METHODS: Exothermia of the epoxy resin during curing was tested against PMMA with surface temperatures recorded over the first 15 minutes of curing, using four samples of each product. The hardness of 90 identical epoxy resin bars was tested by subjecting them to cyclic loads (1,000 cycles of 20.5 N, every 7 days) over a 16-week period and impact testing 10 bars every 2 weeks. Ten bars that were not subjected to cyclic loads were impact tested at 0 weeks and another 10 at 16 weeks. Strength of the epoxy resin product, as a bar and clamp composite, was tested against metal SK and Kirschner-Ehmer (KE) clamps and bars in Type 1a, tied-in intramedullary pin, ESF constructs with either 90° or 75° pin placement, subjected to compressive and bending loads to 75 N. RESULTS: The maximum temperature during curing of the epoxy resin (min 39.8, max 43.0)°C was less than the PMMA (min 85.2, max 98.5)°C (p<0.001). There was no change in hardness of the epoxy resin bars over the 16 weeks of cyclic loading (p=0.58). There were no differences between the median strength of the epoxy resin, SK or KE ESF constructs in compression or bending when tested to 75 N (p>0.05). Stiffness of constructs with 75° pin placement was greater for SK than epoxy resin constructs in compression (p=0.046), and was greater for KE than epoxy resin constructs in bending (p=0.033). CONCLUSIONS: The epoxy resin tested was found to be less exothermic than PMMA; bars made from the epoxy resin showed durability over an expected fracture healing timeframe and had mechanical strength characteristics comparable to metal bar and clamp ESF constructs. CLINICAL RELEVANCE: The epoxy resin ESF construct tested in this study can be considered a suitable replacement for SK or KE ESF constructs in the treatment of feline long-bone fractures, in terms of mechanical strength.

Permanent monoparesis in a dog after intramedullary injection of iohexol into the lumbar spinal cord.

UNLABELLED: Abstract CASE HISTORY: An 8-year-old, spayed, Doberman Pinscher bitch presented for assessment of acute hindlimb paresis. CLINICAL FINDINGS: During a lumbar myelographic contrast study a small volume of iohexol contrast agent was inadvertently injected into the cord parenchyma. After surgical hemilaminectomy for an intervertebral disc extrusion at L1-2 the dog recovered use of one hindlimb, but had ongoing extensor weakness of the left hindlimb. Left femoral nerve function had not returned after 14 months. DIAGNOSIS: EMG findings 14 months after the incident indicated persistent femoral neuropathy consistent with the intramedullary contrast injection at L3-4. CLINICAL RELEVANCE: Inadvertent deposition of iohexol into spinal cord parenchyma may be rare, but if it occurs it can have long-lasting consequences.

Pedicle ligation in ovariohysterectomy: an in vitro study of ligation techniques.

OBJECTIVES: Ligature failure is an important complication following ovariohysterectomy in the bitch. The aim of this study was to assess the differences between five individual ligation techniques in their ability to attenuate a bulky vascular model. METHODS: A vascular model was constructed that enabled the occlusive ability of five different ligation techniques to be measured including the square knot, surgeon's knot, slip knot, modified transfixing ligature and the single-double other side knot. Each was constructed using both USP-0 polyglyconate and polyglactin 910 suture material. The extent of attenuation of the vascular model that was achieved by each technique was assessed using pressure transducers. RESULTS: In this model, the slip knot, modified transfixing ligature and the single-double other side knot outperformed the square and surgeon's knots. CLINICAL SIGNIFICANCE: The results of this study suggest that utilising a knot design that has more inherent resistance to slippage of the first throw (e.g. the modified transfixing ligature, slip or single-double other side knots) may be preferable over square and surgeon's knots when tying a ligature on a bulky vascular pedicle like the ovarian stump in a large bitch.

Probable avulsion of the infraspinatus tendon of insertion in a Rottweiler.

CASE HISTORY: An 8.5-month-old male Rottweiler was presented with chronic, non-localisable, right forelimb lameness. CLINICAL FINDINGS: Survey radiographs revealed panosteitis in the right antebrachium and an irregularly marginated radiolucency on the lateral aspect of the proximal left humerus. The tendon of insertion of the left infraspinatus muscle was enlarged, some tendon fibres ended prematurely in a cluster of mineralised particles, and there was a large bony defect at the point of insertion. DIAGNOSIS: Probable avulsion of the left infraspinatus tendon. CLINICAL RELEVANCE: This case was particularly unusual due to the marked prominence of the lesion without lameness of the left forelimb. Avulsion of the infraspinatus tendon is poorly described in the veterinary and medical literature.