Bi-Phase External Skeletal Splint Fixation of Mandibular Fractures in Dogs

The technique for stabilizing the mandible using the bi-phase external splint is described. Considerations for the use of external skeletal fixation on the mandible are reviewed. Two severe mandibular fracture cases and 1 case of unilateral mandibular body excision for the treatment of oral neoplasia are presented. Excellent results have been obtained by using the bi-phase splint in dogs of moderate to large size.     

Unilateral Uniplanar External Skeletal Fixation for Isolated Diaphyseal Tibial Fractures in Skeletally Immature Dogs

Objective: To report and evaluate use of external skeletal fixation (ESF) for repair of isolated (fibula intact) diaphyseal tibia fractures in skeletally immature dogs.
Study Design: Case series.
Animals: Skeletally immature (mean age, 17 weeks; range, 12–23 weeks) dogs (n=5) with isolated diaphyseal tibial fractures.
Methods: Medical records (2006–2007) of 5 dogs with isolated diaphyseal tibial fractures treated with Type 1a ESF were reviewed and outcome assessed by clinical examination and telephone interviews.
Results: Dogs were evaluated ∼2 and 4 weeks after surgery. Limb function, muscle mass, and comfort level remained very good to excellent throughout healing. Bony union was confirmed radiographically and the ESF removed ∼4 weeks after surgery (mean, 31.4 days; range, 28–37 days). Owner satisfaction was high when contacted a minimum of 4 weeks after ESF removal.
Conclusions: Use of Type Ia ESF with positive profile threaded pins is a practical and biologic method for treatment of isolated tibial fractures in skeletally immature dogs
Clinical Relevance: ESF is an effective alternative treatment to external coaptation and internal fixation for isolated diaphyseal tibial fractures in skeletally immature dogs.     

Miniplate Fixation for Repair of Mandibular and Maxillary Fractures in 15 Dogs and 3 Cats

Maxillofacial miniplates and screws were used for skeletal fixation in 15 dogs and 3 cats that sustained a variety of mandibular and maxillary fractures. These implants were used as neutralization or buttress fixation in 11 caudal (junction of the ramus with the mandibular body) and 2 rostral mandibular fractures, 4 maxillary fractures, and 2 zygomatic arch fractures. All but one of the fractures healed with appropriate occlusion and excellent function. In one case of a rostral mandibular fracture, soft tissue dehiscence occurred accompanied by a loss of the fixation and subsequent distraction of the bone fragments; reasonable function was obtained by performing a rostral mandibulectomy. Plate contouring and application of the miniplates along the appropriate biomechanical lines of stress was easily performed and permitted the biomechanical principles of tension band fixation to be applied in most cases. Miniplate fixation, either used alone or in combination with other fracture fixation techniques, achieved sufficiently rigid skeletal fixation to provide uncomplicated healing and good to excellent functional and cosmetic results in 14 dogs and 3 cats.     

Correction of Rotational Deformity of the Pes with External Skeletal Fixation in Four Dogs

Objective— To report unilateral correction and initial stabilization with external skeletal fixation (ESF) of metatarsal rotation in 4 immature Bernese Mountain Dogs.
Study Design— Case series.
Animals— Bernese Mountain Dogs (n=4).
Methods— The limb deformity, including degree and origin of the deformity at the level of the proximal intertarsal joint and involvement of the central tarsal bone, was characterized by clinical and radiographic assessment. Unilateral surgical correction of the most severely affected limb was performed by disrupting the ligaments and debriding the articular cartilage of the proximal intertarsal joint to allow for derotation of the deformity and arthrodesis of the proximal intertarsal joint stabilized with either circular or linear ESF.
Results— Initial metatarsal rotation of the corrected limbs ranged from 60° to 80° of external rotation (mean, 72.5°). Three limb corrections were stabilized with circular ESF and 1 with a biplanar linear ESF. Implants were removed at the time of radiographic bony union (range, 7–10 weeks; mean, 8.6 weeks). Residual deformity was minimal, ranging from 6° to 15° (mean, 11°). Two minor complications (loosening of 1 pin, serous drainage from 1 pin) resolved with treatment.
Conclusion— Correction of rotational deformity of the pes with intertarsal arthrodesis yielded an excellent clinical outcome, with only a mild residual deformity.
Clinical Relevance— Rotational metatarsal deformities can have a significant impact on gait, ambulation, and appearance. Correction of these deformities and stabilization with ESF and intratarsal arthrodesis can yield an excellent functional outcome, with improved gait and ambulation.     

Evaluation of 2 Types of External Skeletal Fixation for Repair of Experimental Tibial Fractures in Foals

Transverse or oblique midshaft tibial osteotomies were created in 11 foals. The osteotomies were repaired during the same procedure using external skeletal fixation in either full splint or 3-dimensional (3-D) tent configurations. Four of the six foals receiving the full splint fixator recovered to full soundness; two were euthanized because of complications. The foals receiving the 3-D tent configuration would not bear weight on the limbs and consequently suffered significant secondary fracture disease. These foals were euthanized for humane reasons before the scheduled termination of the project. The full splint configuration is considered a viable option for use in foals less than 150 kg with fractures that are not amenable to other proven method of repair.     

Pinless External Fixation of Mandible Fractures in Cattle

Objective — This report describes our experience with a new technique for stabilization of mandibular fractures in cattle using a pinless external fixator.
Study Design — Mandibular fractures were stabilized with a pinless external fixator, which is a modification of a unilateral AO/ASIF (Association for the Study of Internal Fixation)-fixator in which pins are replaced with bone clamps.
Animals — Seven dairy cattle between 1 and 5 years of age.
Methods — Fracture stabilization was achieved by using the pinless external fixator. Postoperative management included intravenous administration of sodium chloride-glucose and antibiotics. A suspension of ruminal contents from a normal cow together with linseed and grass pellets was administered with a gastric tube.
Results — Three to 10 days after surgery six of seven cows masticated comfortably. The only failure was a yearling with a 10-day-old open infected fracture. This animal was slaughtered 9 days after surgery because of additional problems. In six cases there was enough callus formation 33 to 54 days after surgery to stabilize the fracture. The fixation devices were removed under heavy sedation. The major complication was bone sequestration at the fracture site, which required additional treatment.
Conclusion — The pinless fixator has proven satisfactory for external stabilization of unilateral horizontal ramus fractures of the mandible in cattle.
Clinical Relevance — The technique provides good stability without penetration of the medullary cavity and damage to the tooth roots. Other advantages of the technique include ease of application, minimal surgical trauma, and the short surgical time for application.     

Flexible External Fixation for Craniodorsal Coxofemoral Luxations in Dogs

An external fixator consisting of two Ellis pins connected by a flexible band was developed and evaluated as a treatment for craniodorsal coxofemoral luxations in dogs. The technique for closed application of the fixator without injury to the coxofemoral joint or sciatic nerve was developed in six dog cadavers. The coxofemoral joints were then surgically destabilized and the limbs were manipulated through a full range of motion to assess the efficacy of the fixator in maintaining joint reduction. The fixator maintained joint reduction and stability after a surgically created craniodorsal luxation except when the femur was externally rotated 90d?. A flexible external fixator was then applied unilaterally in four healthy dogs. The dogs tolerated the fixator well and were bearing weight on the limb within 2 days after surgery; the range of motion was not limited by the fixator. The efficacy of a flexible external fixator in maintaining joint reduction after craniodorsal coxofemoral luxation was then evaluated in eight large dogs. The right coxofemoral joint in each dog was luxated surgically by removal of the dorsal joint capsule and transection of the ligament of the head of the femur and deep gluteal muscle. The joint was reduced and the fixator pins were applied in a closed fashion. In four dogs, a flexible external band was applied to the pins. Luxation did not reccur in these four dogs. The bands were not applied initially in four control dogs. Luxation occurred in three of the four control dogs within 24 hours of surgery. The joints that luxated were reduced and the flexible bands applied. Luxation did not recur after the bands were in place. The dogs tolerated the external fixators well, were bearing weight within 2 days of surgery, and walking with only minimal lameness 5 days after surgery. Luxation of the coxofemoral joints did not occur during the 2-week period in which the fixators were in place. The joints remained stable 1 week after removal of the fixators, at which time the dogs were euthanatized. Necropsy evaluation identified inflammation surrounding the pins and fibrous thickening of the dorsal joint capsule. The flexible external fixators were applied closed, maintained reduction of the coxofemoral joint after replacement of a craniodorsal luxation, and allowed weight bearing and limb usage soon after surgery. The flexible external fixator has several advantages over other methods of treating craniodorsal coxofemoral luxations. Complications noted in this study included pin tract drainage, pin loosening, and disruption of the flexible bands.     

Kirschner Wire Fixation of Lateral Humeral Condylar Fractures in Small Dogs

Successful treatment of humeral condylar fractures requires accurate reduction and rigid internal fixation. Lag screw fixation is the traditional method of repair for these fractures. An alternative method using Kirschner wire fixation was used to repair humeral condylar fractures in eight small dogs. Long-term follow-up was available for seven dogs: all were reported to have normal limb function.     

Static Strength Evaluation of Six External Skeletal Fixation Configurations

The relative strength of six different configurations of external skeletal fixation was determined by subjecting them to axial compression, and shear and torsion forces while measuring the load they would sustain before failing. The double clamp, single connecting bar, double connecting bar, quadrilateral frame, full pin splintage and three- dimensional tent configurations were found to be successively stronger in all three of the tests with the exception of the quadrilateral frame being more resistant to shear force than the full pin splintage configuration.     

Distraction Osteogenesis Using Modified External Fixation Devices in Five Dogs

Distraction osteogenesis was used to treat five dogs with limb deformities or limb shortening. The affected bones underwent osteotomy, and modified external fixators were attached. Complications included pin loosening, implant breakage, and soft-tissue contracture. Adequate limb length was attained in all cases, but clinical results varied from poor to excellent. Two dogs were not lame after the procedure, two dogs had improved function but were still lame, and one dog had complications necessitating amputation.     

Maxillomandibular Circular External Skeletal Fixation for Repair of Bilateral Fractures of the Caudal Aspect of the Mandible in a Dog

Objective: To describe the novel use of circular external skeletal fixation (CESF) for repair of bilateral fractures of the caudal aspect of the mandibles. Study Design: Clinical report. Animals: A 5‐month‐old female Newfoundland. Methods: A 2‐ring CESF was used to immobilize the mandible relative to the maxillae. Results: Anatomic dental occlusion and reduction of the right hemimandible were achieved with mild malalignment of the left hemimandible. Fracture healing occurred within 20 days. Transient epistaxis and reduced temporomandibular joint range of motion occurred at the time of fixator removal but normal use of the mandible was reported 6 months postoperatively. Conclusions: CESF effectively immobilized the mandible permitting rapid fracture healing with minimal morbidity. Clinical Relevance: Maxillomandibular CESF may represent a simple, effective option for the management of challenging fractures involving the caudal aspect of the mandible.     

A Comparison of Nonthreaded, Enhanced Threaded, and Ellis Fixation Pins Used in Type I External Skeletal Fixators in Dogs

Three different pin types (Ellis, enhanced threaded, and nonthreaded) were used in type 1 external skeletal fixation after transverse osteotomy of the radius and ulna in 12 skeletally mature dogs. Dogs were placed into three groups of four dogs based on the pin type used. Axial extraction forces were determined for each of the pin types after 8 weeks of weight bearing (chronic study). Nine contralateral radii were used to determine axial extraction forces for nine of each pin type not subjected to weight bearing forces (acute study). The force required for extraction of the enhanced threaded and Ellis pins in the chronic and acute studies was not significantly different. The force required to extract the nonthreaded pins was significantly less than that required for the other two pin types. Ground reaction forces had returned to levels measured before surgery by 2 weeks after surgery in the enhanced threaded and Ellis pin groups, however, dogs in the nonthreaded pin group required 4 weeks until normal ground reaction forces were measured. Radiographic evaluations 1,2,4, 6, and 8 weeks after surgery showed no difference among groups in the number of pin tract radio-lucencies, however, the enhanced threaded pins had caused more trans-cortical chip fractures than the other two pin types. None of the pins broke during the eight-week chronic study.     

The Effect of Long-Term Bone Plate Application for Fixation of Radial Fractures in Dogs

This study was divided into two phases. In the in vitro phase, a stainless steel bone plate was applied to the cranial surface of the radius in 14 canine limbs. The effect of the presence of a bone plate on bone density analysis using radiographic photodensitometry (RP) was evaluated by comparing the density measurement of the unplated limb to the density measurement of the plated limb. The optical density of the plated bones was 12% greater than that of the unplated bones. This information was used as a correction factor for the in vivo study. In the in vivo phase, 23 dogs with radial and ulnar fractures were examined for complications associated with the long-term application of a stainless steel plate applied to the cranial surface of the radius. In 14 dogs, RP analysis was used to compare the plated limb with the normal, contralateral limb. No significant differences in radial cortical bone density existed between the plated limb and the contralateral limb after taking into account the effect a bone plate had on photodensitometry readings. There was no significant correlation between the change in radial cortical density and the duration of bone plate application, suggesting that a steady state between bone loss and bone production occurs after long-term plate fixation of the fractured canine radius. The majority (87%) of the dogs with a plate applied to the radius greater than 1 year had normal limb usage when standing, walking, or running.     

Ex Vivo Biomechanics of Kirschner-Ehmer External Skeletal Fixation Applied to Canine Tibiae

The purpose of this study was to determine the respective contribution of each of the following parameters to the compressive, bending, and torsional rigidity of the Kirschner-Ehmer (KE) external fixation splint as applied to canine tibiae with an osteotomy gap: bilateral versus unilateral splints; increasing the number of fixation pins; altering the diameter of fixation pins and side bars; decreasing side bar distances from the bone; increasing pin separation distances in each pin group; decreasing distances between pin groups; altering pin clamp orientation; and altering side bar conformation. Bilateral splints were 100% (mean) stiffer than unilateral splints, with stiffness enhanced to the greatest extent in mediolateral bending and torsion. Increasing pin numbers stiffened both bilateral (mean, 41%; 8 versus 4) and unilateral splints (mean, 14%; 8 versus 4). Medium KE splints were 85% (mean) stiffer than small KE splints. Decreasing side bar distances to the bone from 1.5 cm to 1.0 cm to 0.5 cm increased stiffness of both bilateral and unilateral splints by a mean of 13% to 35%. Widening pin spacing from 1.67 cm to 2.5 cm increased stiffness in craniocaudal bending only (56% increase, bilateral splints; 73% increase, unilateral splints). Decreasing the distance between pin groups from 5.84 cm to 2.5 cm increased stiffness in torsion between 23% (unilateral splints) and 45% (bilateral splints) and decreased stiffness of unilateral splints by 29% in craniocaudal bending. Altering pin clamp configuration so that the bolts of the clamp were inside the side bar rather than outside the side bar increased stiffness in axial compression only (73% increase, bilateral splints; 54% increase, unilateral splints). Conforming the lateral side bar to the tibiae increased only axial compressive stiffness by 77% but was no different than placing the clamps inside the side bars of an unconformed bilateral splint. These results quantify the relative importance of specific parameters affecting KE splint rigidity as applied to unstable fractures in the dog.     

Placement of Multiple Full Pins for External Fixation Technique and Results in Four Dogs

A technique using a third bar and guide clamp was developed to permit reduction and stabilization of distal limb fractures with full pins and two connecting bars, one on each side of the bone. The system uses only single Kirschner clamps. Four distal limb fractures were stabilized using this technique. Closed reduction was used in three dogs to avoid devitalization of fragments and avoid contamination of a closed fracture. The fracture site stability achieved with this configuration allowed early return to weight bearing and rapid bone healing.