Aj Worth

Computer-assisted surgical correction of an antebrachial deformity in a dog

OBJECTIVE To report the use of three dimensional (3D) computed tomographic (CT) imaging, computer simulation and rapid prototype modelling to aid surgical correction of a complex antebrachial deformity in a dog. METHODS A six-year-old, 13 kg spayed female Chihuahua crossbreed dog was presented for worsening forelimb gait and exercise intolerance. Both forelimbs had gross angular limb deformity with carpal hyper-flexion, valgus and radial procurvatum. Surgical planning from radiographs was problematic therefore CT data were used to generate 3D reconstructions of the antebrachium. Using imaging software we then quantified the nature of the deformity using a previously unreported method based on the centre of rotation of angulation as a 3D model. Computer simulated closing of the virtual wedge osteotomy was then performed as proof of concept. A stereolithographic model complete with osteotomy axes, was then created in plastic using a rapid prototyping machine. Oscillating saw guides were fabricated in polymethylmethacrylate and cold sterilised. A closing wedge osteotomy with de-rotation was performed and stabilised with a pre-contoured dynamic compression plate. At the three- and six-month follow-up examinations there was improved weight-bearing and cosmetic appearance. CONCLUSIONS Computer assistance was valuable for locating and quantifying this antebrachial deformity and conceptualising the corrective surgery. The results of our study suggest that rapid prototyping can be used to create models and saw guides to simplify one-stage corrective osteotomies and more accurately treat angular limb deformity.

Degenerative lumbosacral stenosis in working dogs: Current concepts and review

Abstract Extract Degenerative lumbosacral stenosis (DLSS) is a common condition amongst active large-breed dogs, and has a complex aetiopathogenesis. Diagnosis is hampered by subtle clinical signs which may be confused for other neurological or orthopaedic conditions. Signalment and specific manipulative tests allow the clinician to form a high suspicion for DLSS and initiate investigation, however plain radiographic findings are not pathognomic. Advanced imaging is considered essential for an accurate diagnosis but may highlight non-symptomatic lesions, therefore clinical judgement remains paramount. Medical management of mild cases is generally considered to be satisfactory for pet animals, for which modification of their lifestyle is possible. However, return to an acceptable level of performance requires surgical intervention in most working dogs. Whilst some prognostic indicators have been identified, recurrence is common, and many questions remain as to the best method of surgical management. Three-dimensional reconstructive computed tomography (CT) has introduced a new means of indirectly visualising the neuroforamina that exit at the lumbosacral space. This review covers the current state of knowledge of DLSS in dogs, and attempts to identify areas for future study regarding dynamic instability and changes to the lumbosacral neuroforamina at the extremes of joint motion.

Ability to work and owner satisfaction following surgical repair of common calcanean tendon injuries in working dogs in New Zealand

Abstract AIM: To report the long-term outcome (return to work and owner satisfaction) following surgical treatment of common calcanean tendon (Achilles tendon) injuries in working dogs in New Zealand. METHODS: Ten New Zealand Huntaway or Heading dogs (working Collies) with complete or partial tears of the common calcanean tendon, were treated using locking-loop suturing and casting, with (7) or without (3), a calcaneo-tibial screw. All dogs were actively in work on sheep or cattle farms at the time of injury, and return to work was the desired outcome. Ability to work and owner satisfaction were investigated using a telephone questionnaire at a mean followup interval of 14.6 months. RESULTS: Overall, 7/10 dogs returned to full or substantial levels of work. Post-operative complications occurred in two dogs that did not return to full or substantial levels of work. Moderate persistent lameness (score 3 on a scale of 0–5) was present in 2/7 dogs that returned to full or substantial levels of work, equating to a 71% good-to-excellent functional outcome within this group. Seven owners felt the financial investment in opting for surgical repair was worthwhile. A screw and cast method of rigid immobilisation was thought to be superior to casting alone. CONCLUSIONS: Surgical treatment of common calcanean tendon injury in working dogs carries a good prognosis if an appropriate tenorrhaphy technique is used and rigid immobilisation is achieved for 6 weeks. Care must be taken to limit post-operative complications. CLINICAL RELEVANCE: This study justifies the use of surgical repair of such injuries in the working dog even when return to work is the only acceptable outcome.

Long-term assessment of pancarpal arthrodesis performed on working dogs in New Zealand

Abstract AIM: To determine the outcomes following unilateral pancarpal arthrodesis (PCA) in working dogs in New Zealand, in terms of return to work and ability, as assessed by the owner. METHODS: Working dogs treated using unilateral PCA were identified by searching the medical records of the Massey University Veterinary Teaching Hospital (MUVTH) by diagnosis and breed code. Eight Heading dogs (working Collies) and four New Zealand Huntaways were identified with carpal pathology that had been treated by dorsal-plate application, bone-grafting, and casting. All dogs were actively in work on sheep or cattle farms at the time of injury. Case files and radiographs were retrospectively analysed, and the ability of the dog to work after surgery and owner satisfaction with the outcome were assessed using a questionnaire conducted at a mean follow-up interval of 5 years. RESULTS: Following arthrodesis, 6/12 (50%) dogs could perform duties as before surgery. A further four (33%) dogs could perform most former duties. Ten of the twelve owners were satisfied or very satisfied with resultant mobility and work performance of their dogs. Post-operative complications occurred in 50% of dogs, but in only one case affected the eventual outcome. Eleven owners felt surgical repair was worthwhile in a trained working dog. CONCLUSIONS: Unilateral PCA carries a good prognosis for working dogs in New Zealand to return to work, even on hillcountry properties. CLINICAL RELEVANCE: This study may allow veterinarians to provide a more accurate prognosis for working dogs requiring PCA. Working dogs that have sustained severe carpal injury including hyper-extension injury, luxation and fracture, or dogs with crippling carpal osteoarthrosis (OA) can return to work after PCA.

Combined xeno/auto-grafting of a benign osteolytic lesion in a dog, using a novel bovine cancellous bone biomaterial

Abstract CASE HISTORY: A 4-year-old female Labrador Retriever was diagnosed with an osteolytic lesion of the right distal radius. CLINICAL FINDINGS: Radiographs indicated a well-circumscribed radiolucent area 18 × 15 × 8 mm, centred on the distal radial physeal scar. DIAGNOSIS: Histopathology, performed via Jamshidi needle biopsy and following surgical curettage, was inconclusive but suggested either an aneurysmal bone cyst or fibrous dysplasia. CLINICAL RELEVANCE: A novel processed cancellous bovine bone xenograft was used in conjunction with autogenous cancellous bone (at a ratio of approximately 4:1) to fill the curetted defect. There were no observed complications associated with the use of this new biomaterial. Osteointegration of the bone graft was followed using conventional radiographs and peripheral quantitative computed tomography (pQCT) for 10 months post-operatively. Radiographically, the osteolytic lesion modelled to resemble metaphyseal trabeculation. The cross-sectional area and the average bone density of the grafted lesion determined using pQCT data increased over time, suggesting healthy osteoconduction and native bone production.

Necrotising fasciitis associated with Escherichia coli in a dog

Abstract CASE HISTORY: Lameness and limb pain associated with a laceration in the inner thigh of a Border Collie dog progressed over 4 days to extensive necrosis of the full-thickness of skin and subcutaneous (S/C) tissue. A successful outcome was achieved using surgical debridement and intensive supportive care, followed by limited local closure, axial pattern flap development, and free skin grafting. CLINICAL FINDINGS: Clinical findings included severe pain, depression, pyrexia and hypoalbuminaemia, and full-thickness loss of skin from the caudal thigh to the hock. Histopathologically, debrided tissue showed extensive necrosis of the dermis, adipose and muscle tissues, and the presence of numerous Gram-negative rods. Escherichia coli was cultured from deep tissue samples. DIAGNOSIS: Necrotising fasciitis (NF) associated with E. coli infection. CLINICAL RELEVANCE: NF associated with E. coli has not been previously reported in dogs. The importance of early diagnosis and surgical debridement is noted and the relevant medical literature is reviewed.

Nitrite poisoning in cats and dogs fed a commercial pet food

The death of three cats, from two separate households, was linked to toxic concentrations of sodium nitrite used as a preservative in a commercial pet food. Post-mortem examination of the three cats revealed a brownish discoloration of the blood suggestive of methaemoglobinaemia. Analysis of two samples of the pet food fed to the cats revealed a mean concentration of 2850 mg of total nitrite per kg of food (as fed). In a further incident, ataxia and weakness was noticed in two of four dogs after they were fed the same brand of pet food. One dog was successfully treated for methaemoglobinaemia with intravenous methylene blue.

Canine hip dysplasia: phenotypic scoring and the role of estimated breeding value analysis

Abstract Canine hip dysplasia (CHD) is a developmental orthopaedic disease of the coxofemoral joints with a multifactorial mode of inheritance. Multiple gene effects are influenced by environmental factors; therefore, it is unlikely that a simple genetic screening test with which to identify susceptible individuals will be developed in the near future. In the absence of feasible methods for objectively quantifying clinical CHD, radiographic techniques have been developed and widely used to identify dogs for breeding which are less affected by the disease. A hip-extended ventrodorsal view of the pelvis has been traditionally used to identify dogs with subluxation and/or osteoarthritis of the coxofemoral joints. More recently, there has been emphasis on the role of coxofemoral joint laxity as a determinant of CHD and methods have been developed to measure passive hip laxity. Though well-established worldwide, the effectiveness of traditional phenotypic scoring schemes in reducing the prevalence of CHD has been variable. The most successful implementation of traditional CHD scoring has occurred in countries or breeding colonies with mandatory scoring and open registries with access to pedigree records. Several commentators have recommended that for quantitative traits like CHD, selection of breeding stock should be based on estimated breeding values (EBV) rather than individual hip score/grade. The EBV is a reflection of the genetic superiority of an animal compared to its counterparts and is calculated from the phenotype of an individual and its relatives and their pedigree relationship. Selecting breeding stock on the basis of a dogs genetic merit, ideally based on a highly predictive phenotype, will confer the breeder with greater selection power, accelerate genetic improvement towards better hip conformation and thus more likely decrease the prevalence of CHD.

Comparison between a novel bovine xenoimplant and autogenous cancellous bone graft in tibial tuberosity advancement.

OBJECTIVE To compare radiographic healing and clinical outcome of a frontal-opening wedge osteotomy of canine tibiae when the osteotomy site is packed with either a novel bovine xenograft or standard autogenous cancellous bone graft (ACBG). STUDY DESIGN Cohort study. ANIMALS Dogs (n = 82) with partial or complete rupture of the cranial cruciate ligament that had tibial tuberosity advancement (TTA). METHODS In 48 dogs, the osteotomy was packed with a novel bovine xenograft and in 34 dogs, ACBG was used. Eight week postoperative radiographs from both groups were graded for osteotomy healing using a 0-4-point scale. Data were analyzed using a Mann-Whitney test with significance set at P < .05. RESULTS Thirty-four dogs (39 stifles) with xenoimplants had complete records and radiographic follow-up at 8 weeks. No significant differences between xenografting and autografting were identified in grading of osteotomy fill, osteointegration, or healing of the distal osteotomy. Significant differences were noted in grading of osteotomy healing proximally (autograft > xenoimplant) and of opacity in the osteotomy site (xenoimplant > autograft). CONCLUSIONS Radiographic evidence of healing of the xenoimplanted portion of the TTA osteotomy was equivalent to results with ACBG. Healing of the proximal osteotomy site (above the cage) was improved when ACBG was used as the graft.

Reduction in the incidence of elbow dysplasia in four breeds of dog as measured by the New Zealand Veterinary Association scoring scheme.

Abstract AIM: To determine if there has been any reduction in the incidence of elbow dysplasia in four popular large-dog breeds as measured by the New Zealand Veterinary Association (NZVA) scoring scheme. METHODS: A retrospective analysis of the NZVA elbow dysplasia database was performed using records of all German Shepherd dogs, Labrador Retrievers, Golden Retrievers and Rottweilers that had undergone evaluation since the schemes inception in 1992. The data for each dog included date of birth, date of radiography, gender, grade of left and right elbow (0, 1, 2 or 3), and accredited or dysplastic status. Ordinal logistic regression was used to model the grade of the worst-affected elbow over time. The model included age at scoring and gender as additional variables. Given the known heritability of elbow dysplasia, the hypothesis was that if the NZVA scheme effectively identifies elbow dysplasia, and that dog breeders have been using the data responsibly, there should have been a trend towards a lower incidence of dogs graded dysplastic over time. RESULTS: In all four breeds, there was a significant trend towards lowergrades of the worst-affected elbow over time. For German Shepherd dogs the incidence of elbow dysplasia (worst elbowgrade not zero) fell from 75% to 47% between dogs born in 1991 vs those born in 2008. The corresponding figures were a drop from 86% to 68% for the Labrador Retriever, from 89% to 77% for Golden Retrievers, but only 98% to 95% for Rottweilers. In the Rottweiler and Golden Retriever, gender had a significant effect on the worst elbow grade. In the Golden Retriever, age at scoring also had a significant effect. CONCLUSIONS: There has been a significant reduction in the incidence of elbow dysplasia in four popular large-dog breeds as scored by the NZVA elbow dysplasia scoring scheme. The limitations of the study are the non-compulsory nature of the elbow dysplasia scheme, and the potential bias caused by dog breeders or veterinarians pre-screening potential submissions. The results therefore may not represent those of the overall population. CLINICAL RELEVANCE: The incidence of elbow dysplasia, as measured by the NZVA elbow dysplasia scheme, has reduced in the four breeds investigated since the schemes inception. The New Zealand Kennel Club (NZKC) and the veterinary profession can confidently support the NZVA scoring scheme, and should promote its use by dog breeders.