Comparison of torsional properties between a Fixateur Externe du Service de Santé des Armées and an acrylic tie-in external skeletal fixator in a red-tailed hawk (Buteo jamaicensis) synthetic tibiotarsal bone model.

OBJECTIVE: To compare the torsional mechanical properties of 2 external skeletal fixators (ESFs) placed with 2 intramedullary pin (IP) and transfixation pin (TP) size combinations in a model of raptor tibiotarsal bone fracture. SAMPLE: 24 ESF-synthetic tibiotarsal bone model (polyoxymethylene) constructs. PROCEDURES: Synthetic bone models were fabricated with an 8-mm (simulated fracture) gap. Four types of ESF-synthetic bone model constructs (6/group) were tested: a FESSA with a 1.6-mm IP and 1.6-mm TPs, a FESSA with a 2.0-mm IP and 1.1-mm TPs, an acrylic connecting bar with a 1.6-mm IP and 1.6-mm TPs, and an acrylic connecting bar with a 2.0-mm IP and 1.1-mm TPs. Models were rotated in torsion (5°/s) to failure or the machine angle limit (80°). Mechanical variables at yield and at failure were determined from load deformation curves. Effects of overall construct type, connecting bar type, and IP and TP size combination on mechanical properties were assessed with mixed-model ANOVAs. RESULTS: Both FESSA constructs had significantly greater median stiffness and median torque at yield than both acrylic bar constructs; FESSA constructs with a 1.6-mm IP and 1.6-mm TPs had greatest stiffness of all tested constructs and lowest gap strain at yield. No FESSA constructs failed during testing; 7 of 12 acrylic bar constructs failed by fracture of the connecting bar at the interface with a TP. CONCLUSIONS AND CLINICAL RELEVANCE: Although acrylic bar ESFs have been successfully used in avian patients, the FESSA constructs in this study were mechanically superior to acrylic bar constructs, with greatest benefit resulting from use with the larger TP configuration.

Torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis). SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks. PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined. RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties. CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Autotransfusion in dogs using a 2-syringe technique.

OBJECTIVE: To describe the successful use of an autotransfusion technique utilizing 2 syringes in 4 dogs. CASE SERIES SUMMARY: All 4 dogs in this series had a hemoabdomen and subsequent hypovolemic shock. During surgery blood was collected from the abdominal cavity by the surgeon and passed to an assistant. The blood was then transferred to a second syringe for direct IV administration. The blood was passed through an inline blood filter prior to reaching the patient. Given the transfusion volume and administration time frame, 3 cases were classified as a massive transfusion. All 4 dogs survived the transfusion, were discharged within 3 days of surgery/transfusion and no complications were noted. NEW OR UNIQUE INFORMATION PROVIDED: This case series describes a relatively simple method of performing an autotransfuion in patients with hemoabdomen and hypovolemic shock.

Perianal neuroendocrine tumor with suspected lymph node metastasis causing colonic compression and subsequent megacolon.

An 8-year-old spayed female domestic shorthair cat was presented with a 4- to 5-month history of a progressively growing mass above her anus and an inability to defecate for 3 to 4 wk. External perianal and internal regional masses were subsequently identified and diagnosed as tumors of neuroendocrine origin through surgical excision and histopathologic evaluation. The cat was treated with 2 courses of chemotherapy and radiation therapy.

Tumeur neuroendocrinienne périanale avec une métastase suspectée des ganglions lymphatiques causant une compression du côlon et un mégacôlon subséquent. Une chatte commune domestique stérilisée âgée de 8 ans a été présentée avec une anamnèse de 4 ou 5 mois d'une masse à croissance progressive au-dessus de l'anus et l'incapacité de déféquer depuis 3 ou 4 semaines. Les masses périanales externes et régionales internes ont été subséquemment identifiées et diagnostiquées comme des tumeurs d'origine neuro-endocrinienne suite à l'excision chirurgicale et une évaluation histopathologique. La chatte a été traitée à l'aide de deux séries de traitement et d'une radiothérapie.(Traduit par Isabelle Vallières).

Cryoinsult parameter effects on the histologically apparent volume of experimentally induced osteonecrotic lesions.

Investigation of femoral head osteonecrosis would benefit from an animal model whose natural history includes progression to bony collapse of a segmental necrotic lesion. The bipedal emu holds attraction for systematic organ-level study of collapse mechanopathology. One established method of experimentally inducing segmental lesions is liquid nitrogen cryoinsult. Four cryoinsult parameters-hold temperature, freeze duration, freeze/thaw repetition, and thaw duration-were investigated to determine their individual and combined effects on resulting necrotic lesion morphology. 3D distributions of histologically apparent osteocyte necrosis from 24 emus receiving varying cryoinsults were used to develop univariate and multivariate linear regression models relating resulting necrotic lesion morphology to particular cryoinsult input parameters. These models were then applied to predict lesion size in four additional emus receiving differing input cryoinsults. The best multivariate regression model predicted lesion volumes that were accurate to better than 8% of overall emu femoral head volume. The hold temperature during cryoinsult was by far the most influential cryoinsult input parameter. The utility of this information is to enhance the consistency and predictability of cryoinsult-induced segmental lesion size for the purposes of systematic laboratory studies at the whole-organ level.

Development of a fracture osteomyelitis model in the rat femur.

Osteomyelitis contributes significantly to fracture morbidity. Our objective was to develop a model of induced implant-associated osteomyelitis following fracture repair by modifying an existing rat femur fracture model. Thirty male Sprague-Dawley rats were divided into three groups (Control, Staphylococcus aureus, S. aureus + ceftriaxone). The closed femur fracture model (right femur), stabilized with an intramedullary pin, was combined with inoculation of 10(4) colony-forming units (CFU) of S. aureus. Radiographs were obtained immediately after surgery and at weeks 1, 2, and 3 and were evaluated by individuals blinded to treatment group. At necropsy the CFU of S. aureus per femur and pin were determined and synovial tissue and blood were cultured. The fractured femur from two rats in each group was evaluated histologically. A statistically significant difference in the CFU/femur and CFU/pin was found across treatment groups, with the highest CFU in the S. aureus group and the lowest in the Control group. Cultures of synovial tissue were positive in 11/19 of inoculated limbs. Osteomyelitis was present both radiographically and histopathologically in both S. aureus groups but not in the controls. No rats were systemically ill or had positive blood cultures at the study endpoint. This model will be useful for the evaluation of treatments or prophylactics designed for use in implant-associated osteomyelitis.

In vitro antibacterial properties of magnesium metal against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

Bacterial infections are a costly sequela in any wound. The corrosion properties of 0.15, 0.30, 0.45 and 0.60 g of Mg metal were determined in Mueller-Hinton broth by serially measuring the Mg(2+) concentrations and pH over 72 h. In addition, the effect of Mg metal, increased Mg(2+) concentration and alkaline pH on the in vitro growth of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were evaluated in three separate experiments. The primary outcome measure for culture studies was colony-forming units/ml compared to appropriate positive and/or negative controls. Regardless of the mass of Mg added, there was a predictable increase in pH and Mg(2+) concentration. The addition of Mg and an increase of pH resulted in antibacterial effects similar to the fluoroquinolone antibiotic; however, a simple increase in Mg(2+) concentration alone had no effect. The results demonstrate an antibacterial effect of Mg on three common aerobic bacterial organisms, the mechanism of which appears to be an alkaline pH.

The apparent critical isotherm for cryoinsult-induced osteonecrotic lesions in emu femoral heads.

Cryoinsult-induced osteonecrosis (ON) in the emu femoral head provides a unique opportunity to systematically explore the pathogenesis of ON in an animal model that progresses to human-like femoral head collapse. Among the various characteristics of cryoinsult, the maximally cold temperature attained is one plausible determinant of tissue necrosis. To identify the critical isotherm required to induce development of ON in the cancellous bone of the emu femoral head, a thermal finite element (FE) model of intraoperative cryoinsults was developed. Thermal material property values of emu cancellous bone were estimated from FE simulations of cryoinsult to emu cadaver femora, by varying model properties until the FE-generated temperatures matched corresponding thermocouple measurements. The resulting FE model, with emu bone-specific thermal properties augmented to include blood flow effects, was then used to study intraoperatively performed in vivo cryoinsults. Comparisons of minimum temperatures attained at FE nodes corresponding to the three-dimensional histologically apparent boundary of the region of ON were made for six experimental cryoinsults. Series-wide, a critical isotherm of 3.5 degrees C best corresponded to the boundary of the osteonecrotic lesions.

Relationship between objective and subjective assessment of limb function in normal dogs with an experimentally induced lameness.

OBJECTIVE: To evaluate the relationship between previously used subjective and objective measures of limb function in normal dogs that had an induced lameness. STUDY DESIGN: Prospective, blinded, and induced animal model trial. ANIMALS: Normal, adult, and mixed-breed dogs (n=24) weighing 25-35 kg. METHODS: Force platform gait analysis was collected in all dogs before and after induction of lameness. All gait trials were videotaped; 60 video trials were evaluated by 3 surgeons with practice limited to small animal orthopedics and 3 first year veterinary students in an effort to establish the relationship between subjective and objective measures of lameness. Evaluators were unaware of the force platform data. RESULTS: Concordance coefficients were low for all observers and were similar between students and surgeons. These values were further decreased when normal and non-weight bearing trials were removed. Agreement with the force platform data was low even when observers only had to be within +/-10% of the ground reaction forces. When repeat trials were evaluated surgeons had a much higher repeatability compared with students. CONCLUSIONS: Subjective evaluation of the lameness in this study varied greatly between observers and agreed poorly with objective measures of limb function. CLINICAL RELEVANCE: Subjective evaluation of gait should be interpreted cautiously as an outcome measure whether performed from a single or from multiple observers.

Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking.

The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratory-habituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lower-limb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders.

Evaluation of short-term limb function following unilateral carbon dioxide laser or scalpel onychectomy in cats.

OBJECTIVE: To evaluate short-term postoperative forelimb function after scalpel and laser onychectomy in cats. DESIGN: Randomized, prospective study. ANIMALS: 20 healthy adult cats. PROCEDURES: Cats were randomly assigned to the laser (n = 10) or scalpel (10) onychectomy group. Unilateral left forelimb onychectomy was performed. In the scalpel group, a tourniquet was used during surgery and a bandage was applied after surgery. Pressure platform gait analysis was performed prior to and 1, 2, 3, and 12 days after onychectomy. Peak vertical force (PVF), vertical impulse, and the ratio of the PVF of the left forelimb to the sum of the remaining limbs (PVF ratio) were used as outcome measures. RESULTS: The laser onychectomy group had significantly higher ground reaction forces on days 1 and 2 and significantly higher PVF ratio on day 12, compared with the scalpel group. Similarly, significant differences were found in change in ground reaction forces on days 1 and 2 and the PVF ratio on day 12, compared with day -1. No cats required rescue analgesia during the course of the study. One cat in the laser group had signs of depression and was reluctant to walk on day 2 after surgery, had physical examination findings consistent with cardiac insufficiency, and was euthanized. CONCLUSIONS AND CLINICAL RELEVANCE: Cats had improved limb function immediately after unilateral laser onychectomy, compared with onychectomy with a scalpel, tourniquet, and bandage. This improved limb function may result from decreased pain during the 48 hours following unilateral laser onychectomy.

The effect of tibial plateau angle on ground reaction forces 4-17 months after tibial plateau leveling osteotomy in Labrador Retrievers.

OBJECTIVE: To assess the relationship between postoperative tibial plateau angle (TPA) and ground reaction forces (GRFs) in Labrador Retrievers at least 4-months after tibial plateau leveling osteotomy (TPLO) surgery. STUDY DESIGN: A retrospective longitudinal study. ANIMALS: Thirty-two Labrador Retrievers with unilateral cranial cruciate ligament disease that had TPLO and concurrent meniscal surgery. METHODS: TPA and GRFs were measured pre- and > or = 4 months postoperatively. Preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA and degree of rotation were each compared with postoperative GRFs using correlation analysis. Dogs were also grouped by postoperative TPA and compared using 1-way analysis of variance (ANOVA). Postoperative function was compared with meniscal release/meniscectomy, patient age, sex, body weight and follow-up time using ANOVA. RESULTS: No significant relationship was found between preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA, degree of rotation, or meniscal release/meniscectomy and postoperative function. Mean preoperative GRFs for all dogs were 28.8 +/- 9.5 for peak vertical force (PVF) and 9.3 +/- 3.1 for peak vertical impulse (VI). Mean postoperative GRFs for all dogs were 40.4 +/- 5.0 for PVF and 14.1 +/- 1.9 for VI. CONCLUSIONS: No statistically significant relationship was found between postoperative TPA and GRFs after TPLO > or = 4 months after surgery, where the postoperative angle was between 0 and 14 degrees. No significant relationship was found between the preoperative TPA and postoperative function. CLINICAL RELEVANCE: Limb function in Labrador Retrievers was not affected by postoperative TPA and re-operation for cases with a postoperative TPA between 0 and 14 degrees is not recommended.

Estimate of the annual economic impact of treatment of cranial cruciate ligament injury in dogs in the United States.

OBJECTIVE: To estimate the economic impact to veterinary clients for the medical and surgical treatment of rupture of the cranial cruciate ligament (RCCL) in dogs for the year 2003. DESIGN: Economic impact survey. SAMPLE POPULATION: 501 diplomates of the American College of Veterinary Surgeons (ACVS) indicating that their area of surgical emphasis was small animal orthopedic surgery or small animal general and orthopedic surgery and 4,000 veterinarians indicating to the AVMA that their professional area was small animal practice exclusive or mixed animal practice (at least 80% small animal). PROCEDURE: Veterinarians were surveyed concerning the cost for medical and surgical treatment of RCCL for 2003. The economic impact was calculated by multiplying the number of RCCL surgeries performed by the mean cost of surgery. This was added to the number of RCCL cases managed medically multiplied by the mean cost of medical management. This estimate for survey responders was extrapolated to the total number of veterinarians in the study population for the ACVS or AVMA. RESULTS: Estimates for the total cost of surgery were $171,730,134.72 and $1,020,167,907 for veterinarians in the ACVS and AVMA populations, respectively. The cost of medical management was $2,885,687.86 and $126,558,155.16 for veterinarians in the ACVS and AVMA populations, respectively. After combining the ACVS and AVMA populations, we estimated that owners spent $1.32 billion for the treatment of RCCL in the United States in 2003. CONCLUSIONS AND CLINICAL RELEVANCE: RCCL is a prevalent, costly injury. Results may motivate veterinary and consumer agencies to prioritize funding for a better understanding of the injury.

Effect of postoperative analgesic protocol on limb function following onychectomy in cats.

OBJECTIVE: To evaluate the analgesic effects of topical administration of bupivacaine, i.m. administration of butorphanol, and transdermal administration of fentanyl in cats undergoing onychectomy. DESIGN: Prospective study. ANIMALS: 27 healthy adult cats. PROCEDURE: Cats were randomly assigned to 1 of 3 treatment groups, and unilateral (left forefoot) onychectomy was performed. Gait analysis was performed before and 1, 2, 3, and 12 days after surgery. All forces were expressed as a percentage of the cat's body weight. RESULTS: On day 2, peak vertical force (PVF) was significantly decreased in cats treated with bupivacaine, compared with cats treated with butorphanol or fentanyl. The ratio of left forelimb PVF to PVF of the other 3 limbs was significantly lower on day 2 in cats treated with bupivacaine than in cats treated with fentanyl. No significant differences in vertical impulse (VI) were found between groups on any day. Values for PVF, VI, and the PVF ratio increased progressively following surgery. However, for all 3 groups, values were still significantly decreased, compared with baseline values, 12 days after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that limb function following onychectomy is significantly better in cats treated with fentanyl transdermally or butorphanol i.m. than in cats treated with bupivacaine topically. Regardless of the analgesic regimen, limb function was still significantly reduced 12 days after surgery, suggesting that long-term analgesic treatment should be considered for cats undergoing onychectomy. Irrigation of the surgical incisions with bupivacaine prior to wound closure cannot be recommended as the sole method for providing postoperative analgesia in cats undergoing onychectomy.