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Case History: Three dogs that presented with multiple metacarpal or metatarsal fractures, between January 2004 and November 2008., Clinical Findings: Case 1 had sustained closed fractures of metacarpal bones II-V, resulting in a valgus angulation of the manus. Case 2 had 2-week-old open, infected, comminuted diaphyseal fractures of metatarsal bones II-IV. Case 3 had sustained open fractures of metacarpal bones II-V, that were initially stabilised with intramedullary Kirschner wires, but had gone to non-union 5 months after the initial surgery., Treatment: Circular external skeletal fixation was used in each of the three dogs. In Case 1, the fixator was used to perform a closed reduction, to align the overridden, angulated fractured metacarpus, by distracting the frame. In Case 2, the fixator was applied after a limited open reduction, and was used to provide stable fixation of the comminuted infected fractures while facilitating open wound management. In Case 3, the fixator was applied in buttress fashion, following open debridement and placement of an autogenous cancellous bone graft at the non-union fracture sites., Clinical Outcome: All three dogs developed drainage tracts from the fixator wire. There was minimal associated lameness or pain in two of the dogs, but Case 3 developed a transient lameness ascribed to infection associated with the wire tracts, which resolved following administration of antibiotics. Inflammation of wire tracts resulted in the fixator being removed prior to radiological evidence of union of all fractures in each dog, and the mean time from surgery to removal of the frame was 12 (range 7-24) weeks. None of the dogs had residual lameness or discomfort associated with the fractures at the time of long-term evaluation, which ranged from 10-45 months following surgery., Clinical Relevance: These three cases illustrate the utility of circular external skeletal fixation for the stabilisation of complicated fractures of the metacarpus and metatarsus. The fixators were applied without inducing substantial iatrogenic trauma, and the small-diameter fixation wires provided effective stability of the short metacarpal and metatarsal fracture segments, allowing the fractures to heal. Although complications associated with wire tracts should be anticipated, circular external skeletal fixation should be considered as a viable method for managing complex fractures of the metacarpus and metacarpus in dogs.

Objective: Evaluate the effects of varying ring diameter, wire tension, and wire-divergence angle on the axial stiffness characteristics of circular external skeletal fixator single-ring constructs. Study Design-Biomechanical evaluation using circular fixator components and a Delrin cylinder bone model., Methods: Single ring constructs using two 1.6 mm diameter Kirschner wires to secure a 19 mm Delrin cylinder centered within the ring were examined. Component variables evaluated were ring diameter (50 mm, 66 mm, 84 mm, and 118 mm), wire-divergence angle (30 degrees, 60 degrees, and 90 degrees ), and wire tension (0 kg, 30 kg, 60 kg, and 90 kg). A total of 48 constructs were examined. Rings were rigidly mounted on a universal testing system and the cylinder loaded in axial compression (7.4 N/s) to 220 N. Load/displacement curves were analyzed to determine the following: the displacement (mm) that occurred before the slope of each load/displacement curve became linear, the stiffness (N/mm) of the linear portion of each load/deformation curve, and the total displacement (mm) produced at maximal load. Least-squares linear regression was used to model response variables as linear functions of ring diameter, wire divergence angle, and wire tension. Three-way interactions and 2-way interactions among independent component variables were evaluated first in the modeling process and included in a best model if response variables were found to have statistically significant regression coefficients. The regression coefficients and corresponding standard errors and covariances were used to estimate the maximal effect and standard error attributable to wire divergency angle (change from 30 degrees to 90 degrees ) and wire tension (change from 0 to 90 kg) for each ring diameter., Results: All load/deformation curves had an initial exponential increase in stiffness, with the slope becoming linear at higher loads. The exponential phase was more pronounced in larger-diameter ring constructs and was mitigated by tensioning the wires. Ring diameter had the greatest influence on displacement that occurred before the curve became linear (semipartial r(2) [sp-r2] = .89), stiffness (sp-r2 = .94), and total displacement (sp-r2 = .93). Wire tension exerted a smaller influence on displacement that occurred before the curve became linear (sp-r2 =.06), stiffness (sp-r2 = .03), and total displacement (sp-r2 = .05). Wire divergence angle had a nominal effect on displacement that occurred before the curve became linear (sp-r2 = .0001), on stiffness (sp-r2 = .004), and on total displacement (sp-r2 =.003)., Conclusions: Ring diameter had a profound effect on the axial stiffness characteristic of single ring constructs. Tensioning of the fixation wires can improve the axial stiffness characteristics of these constructs, particularly in larger diameter ring constructs, by mitigating the initial exponential phase of the load/deformation curve. Wire divergence angle had only a nominal differential effect on axial stability., Clinical Relevance: Understanding how individual component variables and their interactions influence bone segment stability should help surgeons to optimize interfragmentary strain. Tensioning fixation wires is probably unnecessary in 50 mm diameter ring constructs, but assumes greater importance as ring diameter increases., (Copyright 2001 by The American College of Veterinary Surgeons)

The biomechanical contribution of the interfragmentary Kirschner wire as a component of composite fixation for acetabular fracture repair was subjectively and objectively evaluated. Acetabular osteotomies were repaired using the screw/wire/polymethylmethacrylate (SWP) composite fixation with or without one of three configurations of Kirschner wire in 32 hemipelves obtained from 16 dogs. Reduction, assessed objectively and subjectively, was unaffected by Kirschner wire placement. Hemipelves repaired with Kirschner wire(s) were subjectively more stable prior to application of polymethylmethacrylate when manually assessed in multiple planes. Consistent incremental increases in stiffness, yield load, and maximum load sustained that were observed during biomechanical testing were not significant, with the exception that hemipelves repaired with two Kirschner wires had significantly greater yield loads than hemipelves repaired without Kirschner wires. The subjective results of this study support the use of at least one interfragmentary Kirschner wire to maintain reduction prior to polymethylmethacrylate application; however, fracture configuration and location may dictate the number and pattern of interfragmentary Kirschner wires used to maintain reduction prior to application of the polymethylmethacrylate. The objective results and observations made during biomechanical testing suggest that use of one or more interfragmentary Kirschner wires may enhance stability after polymethylmethacrylate application.

Distraction osteogenesis and the use of circular external skeletal fixation has increased the capacity of veterinary surgeons to manage difficult orthopedic conditions including limb-length discrepancies, angular deformity, distal and severely comminuted fractures, and bone defects. This article discusses the historical developments of the Ilizarov method of distraction osteogenesis in veterinary surgery, circular external skeletal instrumentation, and the biological principles. There is also discussion of use of this method for correction of angular deformity and bone transport and complications associated with this technique.

Objective: To compare the accuracy of reduction, biomechanical characteristics, and mode of failure of two methods of acetabular osteotomy repair., Study Design: Acetabular osteotomies were created in 16 paired hemipelves and stabilized with a screw/wire/polymethylmethacrylate composite fixation technique (SWP) or a 2-mm veterinary acetabular plate (VAP). Eight intact hemipelves were used as controls., Sample Population: Twelve canine cadavers., Methods: Accuracy of osteotomy reduction was evaluated grossly and by measurement of articular incongruencies formed in polyvinylsiloxane impression casts. Acetabula were loaded in modified bending until failure using a universal testing machine. Data from load-deformation curves were used to determine the biomechanical characteristics of the repaired and intact acetabula. Mode of failure was evaluated grossly and radiographically., Results: Osteotomy reduction was superior in acetabula stabilized with SWP. Mean values +/- standard deviation for load at failure and stiffness of the intact acetabula were 2,796 +/- 152.9 N and 267.5 +/- 61.9 N/mm. Corresponding values for SWP and VAP were 1,192 +/- 202.7 N and 136.3 +/- 76.5 N/mm, and 1.100.5 +/- 331.6 N and 110.0 +/- 51.3 N/mm, respectively. The mean load at failure and stiffness of intact acetabula was significantly greater than acetabula stabilized with SWP or VAP. There was no significant difference between SWP and VAP for load at failure or stiffness. Failure of acetabula stabilized with SWP occurred by fracture of the polymethylmethacrylate and ventrolateral bending of the wires. Acetabula stabilized with VAP failed by ventrolateral twisting of the plate and bending of the caudal screws., Conclusions: SWP and VAP provide comparable rigidity, however, the SWP facilitates more accurate osteotomy reduction., Clinical Relevance: These findings support the use of the SWP technique as an alternative method of acetabular fracture repair.

Deep-frozen, aseptically collected and processed allogeneic cancellous bone was implanted in eight dogs during the surgical repair of diaphyseal long bone fractures and in two dogs during arthrodeses. A combined allogeneic and autogeneic cancellous bone graft was used in two fractures with a segmental bone loss of more than 5 cm. Bone union occurred in five fractures and in both arthrodeses. Failure of fixation occurred in two dogs with nonunion fractures and in a third dog with an open, infected fracture. Biopsies from the fracture sites were obtained from these dogs following failure of their fracture fixation. The cancellous bone graft appeared to be in the process of normal incorporation in each case. Failure of fixation was attributed to technical or case management errors or both, in each of the three fractures that failed to achieve bony union. Frozen allogeneic cancellous bone grafts were effectively incorporated when used in the primary repair of fractures and arthrodeses. Combined autogenous and allogeneic cancellous bone grafts may be particularly useful in the repair of fractures with large segmental diaphyseal bone defects. The use of allogeneic cancellous bone grafts in nonunion fractures requires further investigation before it can be recommended.

Transilial pins and paired plastic spinous-process plates were used to repair fracture-luxations of the sixth lumbar vertebra in 6 dogs. All dogs had signs of lumbar pain and variable lower motor neuron deficits to the hindquarters (including hind limbs, tail, and pelvic region). Lumbar pain was decreased or resolved the day after surgery in all dogs, and 3 dogs were able to walk without assistance. One dog initially deteriorated neurologically after surgery and 2 dogs with multiple concurrent orthopedic injuries had no improvement in neurologic function and remained nonambulatory. Pin migration associated with improper bending of the transilial pins and requiring early implant removal was the most common postoperative complication. Four dogs had no neurologic abnormalities 1 to 3 months after surgery. One dog had a resolving unilateral sciatic nerve deficit 9 months after surgery, and another dog was euthanatized 3 months after surgery because of continued paraparesis and urinary and fecal incontinence. These 6 cases illustrate the efficacy of plastic spinous-process plates in combination with transilial pins for the repair of fracture-luxation of the sixth lumbar vertebra.