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.

Comparison between meloxicam and transdermally administered fentanyl for treatment of postoperative pain in dogs undergoing osteotomy of the tibia and fibula and placement of a uniplanar external distraction device.

OBJECTIVE: To compare the efficacy of meloxicam administered perioperatively with transdermal administration of fentanyl via a patch placed preoperatively in dogs undergoing orthopedic surgery. DESIGN: Prospective study. ANIMALS: 16 dogs. PROCEDURE: Unilateral or bilateral osteotomy of the tibia and fibula was surgically performed, and a uniplanar external distraction device was placed in each limb. Postoperative pain and lameness were assessed 24, 48, and 72 hours after administration of the first of 3 doses of meloxicam (0.2 mg/kg [0.09 mg/lb], IV, given preoperatively, followed by 0.1 mg/kg [0.045 mg/lb], IV, after 24 hours, and 0.1 mg/kg, PO, after 48 hours) or preoperative placement of a transdermal fentanyl patch (50 microg/h) left in place for 72 hours. RESULTS: No significant differences in total pain scores were detected between groups. Mean +/- SD lameness scores assessed at 24 and 72 hours were lower in dogs in the meloxicam group than dogs in the fentanyl group. Lameness scores decreased with time in a similar manner in both treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: Perioperative administration of meloxicam or preoperative placement of a transdermal fentanyl patch provided effective and similar postoperative analgesia in dogs undergoing orthopedic surgery. However, because of its anti-inflammatory effects, treatment with meloxicam reduced the degree of lameness and resulted in rapid functional recovery of the limb.

Effects of static fixation and dynamization after interlocking femoral nailing locked with an external fixator: an experimental study in dogs.

OBJECTIVE: To determine bone healing at 20 weeks, after either static fixation (SG) or after dynamization (DG) at 4 weeks in osteotomized canine femurs repaired with an interlocking nail (ILN) secured with a type I external skeletal fixator (ESF). STUDY DESIGN: Experimental study. ANIMALS: Ten adult beagle dogs. METHODS: After mid-diaphyseal femoral osteotomy, femurs in 10 dogs were repaired with an ILN secured with 4 (2 proximal, 2 distal) threaded custom pins (TP; 2.7-mm-diameter cortical screw with a 2-mm shaft attached to the screw head) to which 2 parallel connecting bars were attached in a type I ESF configuration. In 5 dogs, dynamization was performed at 4 weeks by removing the connecting bars and 2 distal screws. Limb function, range of motion of the stifle joint (ROMSJ), radiographic evidence of bone healing, and complications were studied for 20 weeks. RESULTS: Full limb function was achieved between 8 and 10 weeks in SG dogs, but a decreased ROMSJ was observed from 5 to 8 weeks. In DG dogs, full limb function occurred between 5 and 6 weeks except in 1 dog, and ROMSJ was considered normal in all dogs. Bone healing was not affected by dynamization. Average healing time for SG was 12.8 weeks, and for DG it was 13.6 weeks. Periosteal reaction at TP insertion points, osteolysis around the thread and head of TPs were observed in both groups. A windshield-wiper effect was observed at the tip of 1 ILN. CONCLUSION: ILN locked with a type I ESF can be used for fixation of mid-shaft femoral fractures. Dynamization at 4 weeks did not affect bone healing but did prevent stifle ankylosis and promoted earlier limb function. CLINICAL RELEVANCE: ILN locked with a type I ESF is seemingly a feasible method for repair of mid-shaft femoral fractures and may decrease risk of nail failure.

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.