K-wire is more damaging than standard or acrylic drill bits when evaluating torsional properties of rabbit (Oryctolagus cuniculi) femurs.

OBJECTIVE: The objective of this study is to compare drilling variables and torsional mechanical properties of rabbit femora after bicortical drilling with a 1.5-mm standard surgical drill bit, acrylic drill bit, and K-wire. SAMPLES: 24 pairs of rabbit femora. METHODS: After drilling under controlled axial displacement rate, each bone was biaxially loaded in compression followed by rapid external torsion to failure. Maximum axial thrust force, maximum drill torque, integral of force and displacement, change in temperature, maximum power spectral density of the torque signal, torque vibration, and torque and angle at the yield and failure points were collected. Pre- and postyield stiffness, yield and failure energies, and postyield energy were calculated. RESULTS: The work required to drill through the cis- and transcortices (integral of force and displacement) was greater for the K-wire, followed by the acrylic and then standard drill bits, respectively. The K-wire demonstrated higher maximum torque than the drill bits at the ciscortex, and the force of drilling was significantly greater. The vibration data was greater with the acrylic and standard drill bits than the K-wire. There was no difference in torsional strength between drilling types. CLINICAL RELEVANCE: Mechanical differences exist between different drill bits and K-wire and demonstrate that the K-wire is overall more damaging than the surgical drill bit.

Large T-cell extradural lymphoma with concurrent marked cerebrospinal fluid eosinophilia in a dog.

A 3-year-old male pit bull terrier was presented for a 4-day history of progressive tetraparesis and cervical pain. Magnetic resonance imaging confirmed an extradural mass within the left lateral vertebral canal extending from caudal C5 to mid-T2. Lumbar cerebrospinal fluid (CSF) demonstrated marked (90%) eosinophilic inflammation. A C6-7 dorsal laminectomy and C7-T2 left hemilaminectomy were done, with gross disease remaining. Histopathology revealed a large T cell lymphoma with marked eosinophilic infiltration. The dog underwent CHOP-based chemotherapy with resolution of clinical signs, with a similar course of therapy performed at recurrence 37 months after initial presentation. The dog was euthanized 39 months after presentation for multiorgan failure secondary to neutropenic sepsis and aspiration pneumonia. This represents a positive long-term response to multimodal treatment of extradural T-cell lymphoma within the vertebral canal associated with a marked CSF eosinophilia.

Gastrointestinal obstruction secondary to activated charcoal granule impaction in a dog.

OBJECTIVE: To describe a serious adverse event of gastrointestinal obstruction requiring surgery following routine administration of multiple doses of activated charcoal (AC) granules, which were prescribed for carprofen toxicosis. CASE SUMMARY: A 2-year-old female neutered Airedale Terrier presented for ingestion of 207 mg/kg of carprofen. Decontamination was initiated with apomorphine to induce emesis. Along with additional supportive care, the dog received an initial dose of 75 mL of AC suspension containing sorbitol by mouth (15.6 g of AC, or 0.6 g/kg), followed by 50 g of AC granules every 8 hours for 4 additional doses. While hospitalized, the dog experienced clinical signs, including vomiting and black diarrhea, as well as bloodwork changes including mild to moderate elevations in kidney and liver enzymes. Given clinical improvement after 72 hours of hospitalization, the patient was discharged for monitoring and ongoing care at home. Two days later, the patient presented again for nausea, dark diarrhea with frank blood, and panting. Abdominal ultrasound showed findings suspicious for partially obstructive foreign material or atypical impacted fecal material partially occluding the distal ileum. Despite medical management overnight, recheck ultrasound the following day demonstrated persistent obstruction with ileal foreign material. Exploratory laparotomy and enterotomy revealed moderate distension and obstruction of the distal ileum with black granular foreign material consistent with charcoal granules. The patient remained in hospital for supportive care for 4 days following the procedure, and all clinical signs were resolved at the time of discharge. NEW OR UNIQUE INFORMATION PROVIDED: This report documents a serious adverse event of gastrointestinal obstruction associated with routine multidose AC administration, which has been occasionally reported in people but not in dogs. The potential for this complication should be taken into account when prescribing multiple doses of AC granules.

Effects of Hole Diameter on Torsional Mechanical Properties of the Rabbit Femur.

OBJECTIVE: The aim of this study was to evaluate and compare the effect of three clinically applicable screw hole diameters on rabbit femoral torsional structural properties. SAMPLE: Eighteen pairs of skeletally mature New Zealand White rabbit femora (36 bones). MATERIALS AND METHODS: Femora with a bicortical hole at mid-diaphysis from one of the 3-drill bit sizes, 1.1 mm, 1.5 mm, 2.0 mm, and intact bones were studied. Each bone was bi-axially loaded in a servo-hydraulic load frame with the bone positioned so the neutral axis of torsion was aligned with the centre of the bone diaphysis. Axial compression to 35% body weight was applied to represent compression at stance, and rapid external torsion was applied to failure. Torque and angular deformation data were plotted for each test, with pre-yield and post-yield stiffnesses derived. Yield and failure torques and angles were determined, along with calculated yield, failure and post-yield energies. RESULTS: Failure torque was reduced compared with that of intact bone; weakened by 37% in 1.1-mm hole models, 53% in 1.5-mm hole models and 65% in 2.0-mm hole models. The torque angular deformation curves lacked plastic deformation. CONCLUSIONS AND CLINICAL RELEVANCE: This study demonstrates the unique, brittle biomechanics of rabbit bone. Based on data from other species that strength loss of no more than 50% is acceptable when placing orthopaedic implants, no defect greater than 1.1 mm (15% bone diameter) is recommended in rabbit femora.

Outcome of nonunion fractures in dogs treated with fixation, compression resistant matrix, and recombinant human bone morphogenetic protein-2.

OBJECTIVES: To report the use of compression resistant matrix (CRM) infused with recombinant human bone morphogenetic protein (rhBMP-2) prospectively in the healing of nonunion long-bone fractures in dogs. METHODS: A longitudinal cohort of dogs that were presented with nonunion fractures were classified and treated with CRM soaked with rhBMP-2 and fracture fixation. They were followed with serial radiographs and evaluated for healing times and complications according to the time frame and definitions previously established for orthopaedic clinical cases. RESULTS: Eleven nonunion fractures in nine dogs were included. Median healing time was 10 weeks (range: 7-20 weeks). Major perioperative complications due to bandage morbidity were encountered in two of 11 limbs and resolved. All other complications were minor. They occurred perioperatively in eight of 11 limbs. Minor follow-up complications included short-term in one of two limbs, mid-term in one of three, and long-term in four of five limbs. Nine limbs returned to full function and two limbs returned to acceptable function at the last follow-up. CLINICAL SIGNIFICANCE: Nonunion fractures given a poor prognosis via standard-of-care treatment were successfully repaired using CRM with rhBMP-2 accompanying fixation. These dogs, previously at high risk of failure, returned to full or acceptable function.