Distraction osteogenesis to treat premature distal radial growth plate closure in a dog

Outcomes of 11 dogs with short radius syndrome treated with acute arthroscopically assisted ulnar shortening

OBJECTIVE

To describe the short-term outcome of acute arthroscopically assisted ulnar shortening (AUS), to treat short radius syndrome in dogs.

STUDY DESIGN

Case series.

ANIMALS

Eleven client owned dogs.

METHODS

Records of dogs that had undergone AUS for treatment of short radius syndrome were reviewed for inclusion. Reporting data included among others pre- and postoperative radioulnar, humeroradial and humeroulnar distances, lameness scores, surgical times, complications and clinical outcome.

RESULTS

Following AUS, radiohumeral articulation was improved in all dogs. Median presurgery radioulnar, humeroradial and humeroulnar values were 4.5, 3.2, and 2.2 mm and were improved with surgery by a median of 3.2, 1.8, and 1.2 mm, respectively. Median surgery time was 140 min. Median time to bone healing was 8 weeks (range: 4-14). Median time to last follow-up was 9 weeks (4-468). Median lameness score (scale 0-4) improved from 2 to 1. No major complications were reported. Short-term clinical outcome was graded by the surgeons as full function in four cases and acceptable function in seven.

CONCLUSION AND CLINICAL RELEVANCE

Radiographic and arthroscopic radiohumeral articulation were improved and short-term clinical improvement was documented following AUS in all 11 dogs.

Physeal Injuries and Angular Limb Deformities

Physeal injuries are common in the developing small animal and can result in growth disturbances of the forelimb. Resulting deformities can include limb shortening, joint incongruity, angulation, and alterations in joint loading with subsequent osteoarthritis, remodeling, and debilitation. Because of the unique paired bone configuration, the antebrachium is the main source for malalignment resulting from physeal disturbance in the forelimb. Successful correction of deformities requires in-depth understanding of normal physeal activity; careful consideration of patient signalment; and the ability to quantify the location, magnitude, and plane of the deformity or deformities.

Experimental study of bone lengthening in dogs by means of backscattered scanning electron microscopy

OBJECTIVE

To describe the morphology of calcified tissues involved in distraction osteogenesis (DO) by means of backscattered scanning electron microscopy (BS-SEM).

STUDY DESIGN

Experimental study.

ANIMALS

Adult female Beagle dogs (n=12).

METHODS

Non-simultaneous and bilateral transverse mid-diaphyseal osteotomies performed in tibiae were stabilized and distracted by a Type Ia external skeletal fixation device. After a latency period of 5 days, distraction was applied at a rate of 0.5 mm every 12 hours for 10 days. Then, the external fixator was maintained in a static mode during the consolidation period until bone healing or euthanasia at 1, 2, 3, 4, 6, 8, 10, 12, 14, and 18 weeks after operations, whichever came first. Distracted regions were isolated and their structure was examined by BS-SEM.

RESULTS

Calcified chondroid tissue was prominent during distraction and calcified cartilaginous tissue during consolidation; both tissues were successively replaced by woven, lamellar, and osteonal bone.

CONCLUSIONS

In osteotomized tibia, chondroid tissue is the main component of the mineralization front during distraction, calcified cartilaginous tissue during consolidation, and then both tissues are replaced by woven, lamellar, and osteonal bone. The ossification mechanism of distraction callus is transchondroidal.

CLINICAL RELEVANCE

BS-SEM is an effective technique for studying progression of bone healing during DO. The presence of chondroid tissue during DO explains why callus mineralization occurs more rapidly during distraction than during static stabilization.

Antebrachial fractures in four captive polar bears (Ursus maritimus)

OBJECTIVE

To identify common risk factors for antebrachial fractures of captive polar bears and to evaluate outcome after fracture repair.

STUDY DESIGN

Retrospective study.

ANIMALS

Four captive polar bears.

METHODS

United States zoological collections were surveyed to determine the prevalence of fractures in captive polar bears. Medical records of captive polar bears that had antebrachial fractures were reviewed for signalment, history, physical and radiographic findings, fracture management, postoperative care, and outcome. Serum samples from healthy bears and bears with antebrachial fractures were assayed for 25-hydroxyvitamin D (25-OHD) concentrations.

RESULTS

Nineteen fractures (12 polar bears) occurred from 1974 to 2002; 12 fractures involved the antebrachium. Management of 4 antebrachial fractures was reviewed; 3 were repaired by internal fixation and 1 by external coaptation. Fractures healed and bears were returned to exhibit on average 3 months postfracture. Of 11 serum samples assayed for 25-OHD concentrations, 6 were below normal, 1 was low normal and 4 were within normal reference intervals. The 7 bears with subnormal or low normal values were housed in 2 zoos. Subnormal vitamin D concentrations were identified in 2 of 3 bears with fractures.

CONCLUSIONS

Fracture disease is not uncommon in captive polar bears. Additional research is necessary to explore the role of nutrition in polar bear fracture disease.

CLINICAL RELEVANCE

Internal fixation of antebrachial fractures is feasible and reasonably well tolerated in captive polar bears.

Treating pedal shortening in a dog by metatarsal distraction osteogenesis

A five-month-old, male German shepherd dog was presented with a left hindlimb deformity. Wearing a cast for a prolonged period to treat left metatarsal fractures at eight weeks of age had resulted in physeal closure of the calcaneus, metatarsals and phalanges. Hyperextension of the phalanges and ulceration of the plantar skin proximal to the main tarsal pad were seen. The left foot was 40 mm shorter than the right. At seven months of age, a modified circular external skeletal fixator (CESF) was used to perform distraction osteogenesis of the metatarsal bones for 28 days. The CESF apparatus was removed after eight weeks when there was radiographic consolidation of regenerate bone. At follow-up evaluations four and 12 months after surgery, the phalangeal hyperextension and plantar skin ulceration had resolved. No lameness was detected.

Use of distraction osteogenesis for the correction of deviated nasal septum and premaxilla in a horse

A 13-month-old female Andalusian was evaluated because of a congenital left deviation of the maxilla and nasal septum, which had resulted in a gross malocclusion of the maxillary incisor teeth. Surgical correction of a deviated nasal septum and premaxilla in a horse was first reported in 1978 and involved a pre-maxilla osteotomy and use of an autogenous rib graft, with a nasal septum osteotomy performed in a second surgery; to the authors' knowledge, no alternative surgical treatments have since been described. In this horse, a new surgical treatment by distraction osteogenesis without nasal septum osteotomy was attempted. After the procedure, the premaxilla and nasal septum deviations were corrected; however, an overjet lesion (rostral projection of maxillary arcade over the mandibular arcade) was evident, for which the owners declined treatment. Compared with previously recommended procedures, distraction osteogenesis appears to be a less invasive treatment for congenital facial deformities and may be considered an option in the treatment of congenital deviation of the nasal septum and premaxilla (wry nose), head scoliosis, brachygnathism, and prognathism in horses.

Effect of various distal ring-block configurations on the biomechanical properties of circular external skeletal fixators for use in dogs and cats

OBJECTIVE

To evaluate mediolateral, axial, torsional, and craniocaudal bending behavior of 6 distal ring-block configurations commonly used to stabilize short juxta-articular bone segments in small animals.

SAMPLE POPULATION

8 circular external skeletal fixator constructs of each of 6 distal ring-block configurations. The distal ring-block configurations were composed of combinations of complete rings, incomplete rings, and drop wires.

PROCEDURE

Constructs were nondestructively loaded in axial compression, craniocaudal bending, mediolateral bending, and torsional loading by use of a materials testing machine. Gap stiffness was determined by use of the resultant load displacement curve.

RESULTS

Circular external skeletal fixator configurations and constructs significantly affected gap stiffness in all testing modes. Within each loading mode, gap stiffness was significantly different among most configurations. In general, complete ring configurations were significantly stiffer than similar incomplete ring configurations, and addition of a drop wire to a configuration significantly increased stiffness of that configuration.

CONCLUSIONS AND CLINICAL RELEVANCE

When regional anatomic structures permit, the use of complete ring configurations is preferred over incomplete ring configurations. When incomplete ring configurations are used, the addition of a drop wire is recommended.

Distraction osteogenesis for treatment of premature physeal closure and shortening of the third and fourth metatarsals of a dog

A 4-month-old Siberian husky was presented for a history of lameness of the left hind limb. Physical and radiographic examination revealed a 1-cm shortening of metatarsals III and IV, with subsequent hyperextension of the digits on the left hind paw. A circular external skeletal fixator was used to accomplish distraction osteogenesis in both metatarsals over a period of 15 days. Treatment was successful in restoring appropriate length of the metatarsals and in resolution of the lameness. At 6 and 12 months after surgery, the owner reported that the dog was ambulating normally and had no complications related to the surgery.