John R. Mosley

Clinical and neurological characteristics of aortic thromboembolism in dogs

OBJECTIVES To characterise the clinical presentation and neurological abnormalities in dogs affected by aortic thromboembolism. METHODS The medical records of 13 dogs diagnosed with aortic thromboembolism as the cause of the clinical signs, and where a complete neurological examination was performed, were reviewed retrospectively. RESULTS The onset was acute in only four dogs, chronic in five dogs (with all of these presenting as exercise intolerance) or chronic with acute deterioration in four dogs. Dogs with an acute onset of clinical signs were more severely affected exhibiting neurological deficits, while dogs with a chronic onset of disease predominantly presented with the exercise intolerance and minimal deficits. The locomotor deficits included exercise intolerance with pelvic limb weakness (five of 13), pelvic limb ataxia (one of 13), monoparesis (two of 13), paraparesis (two of 13), non-ambulatory paraparesis (two of 13) and paraplegia (one of 13). There was an apparent male predisposition and the cavalier King charles spaniel was overrepresented. CLINICAL SIGNIFICANCE The rate of onset of clinical signs appears to segregate dogs affected by aortic thromboembolism into two groups, with different clinical characteristics and outcomes. Dogs with an acute onset of the clinical signs tend to be more severely affected, while dogs with a chronic onset predominantly present with exercise intolerance. It is therefore important to consider aortic thromboembolism as a differential diagnosis in dogs with an acute onset of pelvic limb neurological deficits and in dogs with longer standing exercise intolerance.

Clinical assessments of increased sensory sensitivity in dogs with cranial cruciate ligament rupture

Dogs with chronic pain have a compromised quality of life. Repeatable and accurate sensory assessments form a means by which the hypersensitivity likely to reflect chronic pain may be quantified. These assessments can be applied to individuals to identify those that may benefit from improved analgesic relief. In this study four sensory assessments were evaluated in dogs presenting with a naturally occurring chronic painful condition (cranial cruciate ligament rupture, CCLR) and were compared with healthy control animals of similar age and weight. Inter-digital von Frey filament and thermal sensitivity tests revealed that the affected hind limb of dogs with CCLR was significantly more sensitive than the opposing limb. Static weight bearing and gait parameter scores were also reduced in the affected hind limb compared to the opposing hind limb of dogs with CCLR; no such differences were found between the hind limbs of healthy (control) dogs. The quantitative sensory tests permitted the differentiation of limbs affected by CCLR from healthy limbs. Dogs presenting with CCLR demonstrate objectively quantitative sensory sensitivities, which may require additional consideration in case management.

Genetic selection for fast growth generates bone architecture characterised by enhanced periosteal expansion and limited consolidation of the cortices but a diminution in the early responses to mechanical loading

Bone strength is, in part, dependent on a mechanical input that regulates the (re)modelling of skeletal elements to an appropriate size and architecture to resist fracture during habitual use. The rate of longitudinal bone growth in juveniles can also affect fracture incidence in adulthood, suggesting an influence of growth rate on later bone quality. We have compared the effects of fast and slow growth on bone strength and architecture in the tibiotarsi of embryonic and juvenile birds. The loading-related biochemical responses (intracellular G6PD activity and NO release) to mechanical load were also determined. Further, we have analysed the proliferation and differentiation characteristics of primary tibiotarsal osteoblasts from fast and slow-growing strains. We found that bones from chicks with divergent growth rates display equal resistance to applied loads, but weight-correction revealed that the bones from juvenile fast growth birds are weaker, with reduced stiffness and lower resistance to fracture. Primary osteoblasts from slow-growing juvenile birds proliferated more rapidly and had lower alkaline phosphatase activity. Bones from fast-growing embryonic chicks display rapid radial expansion and incomplete osteonal infilling but, importantly, lack mechanical responsiveness. These findings are further evidence that the ability to respond to mechanical inputs is crucial to adapt skeletal architecture to generate a functionally appropriate bone structure and that fast embryonic and juvenile growth rates may predispose bone to particular architectures with increased fragility in the adult.

The effect of external coaptation on plate deformation in an ex vivo model of canine pancarpal arthrodesis

OBJECTIVES Since external coaptation is applied clinically to prevent plate failure during healing in canine pancarpal arthrodesis (PCA), we tested the hypothesis that external coaptation does not significantly reduce plate strain in an experimental ex vivo model of canine PCA. METHODS Ten thoracic limbs from healthy Greyhounds euthanatized for reasons un- related to the study were harvested and the carpus was stabilised with a dorsally applied 2.7/3.5 mm hybrid PCA plate. The strain in the plate adjacent to the most distal radial screw hole (R4) and the radial carpal bone (RCB) screw hole was measured as the limbs were loaded axially to a load that approximated that of controlled walking. Each limb was tested with and without external coaptation in place. RESULTS Mean strain amplitude at the RCB was -177.2 με (± 20.78) without external coaptation. Following cast application, strain reduced significantly to -34.7 με (± 9.84) (p <0.002). Mean strain at R4 was -89.4 με (± 22.10) without external support and -66.9 με (± 10.74) following application of a cast. This reduction in recorded strain was not statistically significant. CLINICAL SIGNIFICANCE The application of a cast to the distal portion of the limb significantly reduced strain in the 2.7/3.5 mm hybrid PCA plate, but the magnitude of the measured strain was low, suggesting that fatigue damage is unlikely to accumulate as a result of this type of loading and that external coaptation may not be necessary to prevent fatigue failure of the plate.

Management of laterally displaced proximal tibial physeal fractures in three dogs

Fractures of the proximal tibial physis are uncommon in dogs, and are rarely associated with marked instability and lateral displacement of the proximal tibial epiphysis. Three dogs with proximal tibial physeal fractures demonstrating marked instability and lateral displacement were treated with two different principles of fixation. Healing of the physeal fracture was achieved with rigid internal fixation in one case, and with adaptational osteosynthesis supplemented with a temporary transarticular external skeletal fixator in two cases. Duration of surgery and technical difficulty was reduced using a modified adaptational osteosynthesis approach, suggesting that surgical treatment of these uncommon and challenging fractures may be more appropriately achieved by this technique.

Patellar ligament rupture in the cat: repair methods and patient outcomes in seven cases

The medical records of cats receiving surgical treatment for unilateral patellar ligament rupture between 1999 and 2012 at 12 referral centres in the UK and Ireland were reviewed. Seven cases were identified: six were caused by trauma and one was iatrogenic, occurring as a complication following surgical stabilisation of a tibial fracture. All cases were treated by sutured anastomosis of the ruptured ligament, with six of the repairs protected by a circumpatellar and/or transpatellar loop of suture. The stifle was immobilised by transarticular external skeletal fixation in three cases. No cases required revision surgery. No complications were reported. Final evaluation, performed at a median time of 31 days, determined five patients to have returned to acceptable or good limb function; two cases were lost to follow-up. The data suggest that, in cats, the current surgical techniques extrapolated from their canine counterparts for repair of a completely or partially ruptured patellar ligament are successfully used and result in acceptable limb function.

Patellar ligament rupture in the dog: repair methods and patient outcomes in 43 cases

The medical records of dogs receiving surgery for unilateral patellar ligament rupture between 1999 and 2012 at 12 multidisciplinary referral centres were reviewed. Forty-three cases were identified; 26 were traumatic in origin; almost one-third were iatrogenic, of which over three-quarters occurred as a complication following surgical stabilisation of patellar luxation. Treatment involved primary reapposition of the ligament (36 cases). The repair was protected by circumpatellar and/or transpatellar loop(s) of orthopaedic wire, nylon, polypropylene or polydioxanone suture (34 cases). Wire loops were more likely to require surgical removal compared with loops of other materials (P=0.0014). The stifle joint was immobilised postoperatively by the applications of a transarticular external skeletal fixator (taESF) in 17 cases and by external coaptation (EC) in 8 cases; in 18 cases, no postoperative joint immobilisation was provided. Complications specific to the method of immobilisation occurred in seven of the cases with taESF and six of the cases with EC. Revision surgery to address failure of repair was required in five cases. Outcome was classified as acceptable or good in over three-quarters of the cases (31/40) and poor in less than a quarter (9/40). These data highlight patellar ligament rupture as a complication of surgical stabilisation of patellar luxation.

Occlusion of blood flow in the contralateral pelvic limb during positioning for canine total hip replacement surgery

80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 To our knowledge, neither ipsilateral nor contralateral limb ischaemia following total hip replacement has been reported in dogs. Ipsilateral lower limb ischaemia is a widely recognized surgical complication in total hip arthroplasty in humans, most commonly caused by aberrant placement of the acetabular retractor and/or vascular stretch and manipulation (Calligaro et al. 2003; Hakuta et al. 2011; Matos et al. 1979). At least one case of contralateral lower limb ischaemia has been reported in humans (Brookes-Fazakerley et al. 2015). In that case, described in a patient with a previous endovascular abdominal aortic aneurysm repair, a multifactorial cause was hypothesized, which included occlusion of blood flow by pressure exerted on the femoro-femoral crossover graft by the anterior pubic symphysis support used to maintain the lateral position required for surgery. The present report details an acute obstruction to blood flow in the pelvic limb of a dog undergoing total hip replacement, which occurred during positioning of the post used to support the pubic symphysis. A 46-month-old neutered female Labrador underwent general anaesthesia for a right total hip replacement. The patients general medical history and the clinical examination were unremarkable. The blood analyses showed a slight elevation in creatinine concentration (146 mmol L ) but were otherwise normal. Body mass was 22.8 kg with a body condition score of 5/9. Premedication consisted of methadone [0.2 mg kg 1 intramuscularly (IM)], dexmedetomidine (2 mg kg 1 IM) and acepromazine (10 mg kg 1 IM). Anaesthesia was induced with 30 mg propofol administered intravenously. Neuraxial anaesthesia was provided with a lumbosacral extradural injection of 4.75 mL of a solution containing 22.5 mg of bupivacaine and 2.4 mg morphine administered via a 22 gauge 6.25-cm-long

Patellar ligament rupture in the dog

The medical records of dogs receiving surgery for unilateral patellar ligament rupture between 1999 and 2012 at 12 multidisciplinary referral centres were reviewed. Forty-three cases were identified; 26 were traumatic in origin; almost one-third were iatrogenic, of which over three-quarters occurred as a complication following surgical stabilisation of patellar luxation. Treatment involved primary reapposition of the ligament (36 cases). The repair was protected by circumpatellar and/or transpatellar loop(s) of orthopaedic wire, nylon, polypropylene or polydioxanone suture (34 cases). Wire loops were more likely to require surgical removal compared with loops of other materials (P=0.0014). The stifle joint was immobilised postoperatively by the applications of a transarticular external skeletal fixator (taESF) in 17 cases and by external coaptation (EC) in 8 cases; in 18 cases, no postoperative joint immobilisation was provided. Complications specific to the method of immobilisation occurred in seven of the cases with taESF and six of the cases with EC. Revision surgery to address failure of repair was required in five cases. Outcome was classified as acceptable or good in over three-quarters of the cases (31/40) and poor in less than a quarter (9/40). These data highlight patellar ligament rupture as a complication of surgical stabilisation of patellar luxation.

Patellar ligament rupture in the dog: Repair methods and patient outcomes in 43 cases

The medical records of dogs receiving surgery for unilateral patellar ligament rupture between 1999 and 2012 at 12 multidisciplinary referral centres were reviewed. Forty-three cases were identified; 26 were traumatic in origin; almost one-third were iatrogenic, of which over three-quarters occurred as a complication following surgical stabilisation of patellar luxation. Treatment involved primary reapposition of the ligament (36 cases). The repair was protected by circumpatellar and/or transpatellar loop(s) of orthopaedic wire, nylon, polypropylene or polydioxanone suture (34 cases). Wire loops were more likely to require surgical removal compared with loops of other materials (P=0.0014). The stifle joint was immobilised postoperatively by the applications of a transarticular external skeletal fixator (taESF) in 17 cases and by external coaptation (EC) in 8 cases; in 18 cases, no postoperative joint immobilisation was provided. Complications specific to the method of immobilisation occurred in seven of the cases with taESF and six of the cases with EC. Revision surgery to address failure of repair was required in five cases. Outcome was classified as acceptable or good in over three-quarters of the cases (31/40) and poor in less than a quarter (9/40). These data highlight patellar ligament rupture as a complication of surgical stabilisation of patellar luxation.