Stabilisation of atlantoaxial subluxation in the dog through ventral arthrodesis

Ten miniature breed dogs with atlantoaxial subluxation underwent ventral lag screw stabilisation. The procedure did not include bone graft packing into the atlantoaxial articulation. Four dogs showed continuous improvement after surgery. Three dogs developed complications due to external trauma and postoperative implant failure but improved with conservative therapy. Three patients died or were euthanized in early perioperative or postoperative period. The long-term outcome was good or favourable in all surviving patients. Suspected fibrous tissue proliferation and stabilisation without permanent bone fusion was found to be clinically satisfactory when the atlantoaxial joint has been subjected to limited stress during a long-term monitoring period.     

COMPUTED TOMOGRAPHY VARIATIONS IN MORPHOLOGY OF THE CANINE ATLAS IN DOGS WITH AND WITHOUT ATLANTOAXIAL SUBLUXATION

Computed tomography images of 120 dogs were reviewed to characterize variations in atlas morphology, and to identify breed‐specific morphologic features. The neural arch of the atlas was thicker in large dogs and male dogs than in small dogs, having a layer of trabecular bone between the inner and outer layers of compact bone. The transverse processes of the atlas were relatively longer in large dogs than in small dogs. Twelve (10%) dogs had incomplete ossification of the atlas. Incomplete ossification of the atlas was associated with gun dogs. Eight dogs had atlantoaxial subluxation. All eight dogs with atlantoaxial subluxation had cervical signs, whereas none of the seven dogs with incomplete ossification of the atlas unaccompanied by atlantoaxial subluxation had clinical signs referable to that area. Of five dogs with both atlantoaxial subluxation and incomplete ossification of the atlas, four had osseous defects affecting both the intercentrum and neural arch, and one had only an osseous defect affecting the neural arch. There was a strong association between incomplete ossification of the atlas and atlantoaxial subluxation (odds ratio 35.0, 95% CI 7.0–175, P=0.00002), which supports the hypothesis that incomplete ossification of the atlas predisposes dogs to atlantoaxial subluxation.     

A modified ventral fixation for surgical management of atlantoaxial subluxation in 19 dogs

OBJECTIVE: To describe a modified ventral stabilization technique for surgical management of atlantoaxial subluxation in dogs and to evaluate the outcome. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Nineteen client-owned dogs. METHODS: Medical records of 19 dogs with a radiographic diagnosis of atlantoaxial subluxation surgically managed by a modified ventral fixation technique (cortical screws, Kirschner wires, polymethylmethacrylate) were reviewed. Data on pre- and post-operative neurologic status, surgical technique, and complications were retrieved. Follow-up evaluation was performed at approximately 1 month. Telephone interview of the owner was used for long-term assessment (median follow-up for 17 surviving dogs was 10.5 months). RESULTS: Adequate reduction and stabilization was achieved in all dogs based on radiographic assessment immediately after surgery. Improved neurologic outcome occurred in 16 dogs at 1 month and in 15 dogs at follow-up; 2 dogs died of post-operative complications within 24 hours of surgery. One dog was euthanatized at the owners' request because of recurrent neck pain associated with implant failure after 1 month. Two dogs required surgery to remove broken and migrated implants, but further stabilization was not necessary. CONCLUSIONS: Adequate stabilization and improved neurologic outcome was achieved in most dogs. However, on account of the small size of the study and the variable neurologic signs of the dogs on admission, the surgical technique described could not be compared to those previously reported. CLINICAL RELEVANCE: The surgical technique described is an effective means of surgical treatment for atlantoaxial subluxation.     

Stabilization of atlantoaxial subluxation secondary to atlantooccipital malformation in a Devon calf

Atlantoaxial subluxation secondary to atlantooccipital malformation in a 14-day-old female Devon calf was corrected by alignment and stabilization of the atlantoaxial joint. Stabilization was achieved by the ventral placement of pins and screws, and the dorsal placement of a figure 8 tension band wire. At 2 and 14 days post operatively, adequate alignment of the atlantoaxial joint was confirmed radiographically. Following surgery the calf improved clinically, but was terminated 14 days following the surgery due to a pneumonia. At necropsy the fixation was stable and spinal cord decompression had been achieved. It was concluded that this technique could be utilized to allow decompression, anatomical alignment, and stabilization of an atlantoaxial subluxation secondary to atlantooccipital malformation in a calf. At necropsy, there was gross and histologic evidence of congenital fusion of the basioccipital bone to the malformed atlas.     

INCOMPLETE OSSIFICATION OF THE ATLAS IN DOGS WITH CERVICAL SIGNS

Osseous defects affecting the atlas were identified in computed tomography and magnetic resonance images of five dogs with cervical signs including pain, ataxia, tetraparesis, or tetraplegia. Osseous defects corresponded to normal positions of sutures between the halves of the neural arch and the intercentrum, and were compatible with incomplete ossification. Alignment between the portions of the atlas appeared relatively normal in four dogs. In these dogs the bone edges were smooth and rounded with a superficial layer of relatively compact cortical bone. Displacement compatible with unstable fracture was evident in one dog. Concurrent atlantoaxial subluxation, with dorsal displacement of the axis relative to the atlas, was evident in four dogs. Three dogs received surgical treatment and two dogs were treated conservatively. All dogs improved clinically. Incomplete ossification of the atlas, which may be associated with atlantoaxial subluxation, should be considered in the differential diagnosis of dogs with clinical signs localized to the cranial cervical region.     

Occipitoatlantoaxial malformation with atlantoaxial subluxation in a cat

Occipitoatlantoaxial malformation and atlantoaxial subluxation was diagnosed in a three-year-old castrated male domestic shorthair cat. Clinical signs included ataxia, postural reaction deficits, abnormal spinal reflexes, and behaviour changes. Radiographic examination revealed malformation and hypoplasia of the occipital condyles, hypoplasia of the dens, and atlantoaxial subluxation. Electroencephalographic (EEG) findings included high voltage slow activity and sharp waves with superimposed low voltage fast activity in the occipital leads and sinusoidal beta waves in the frontal leads. Basilar artery compression as a result of atlantoaxial instability is suspected to have caused the behavioural changes and EEG abnormalities in this patient. The cat was treated by stabilisation of the atlantoaxial subluxation by ventral cross pin fixation, odontectomy, and arthrodesis of the atlantoaxial articulation. The patient responded well to treatment and was neurologically normal 18 months after surgery.     

Atlantoaxial Instability: A Ventral Surgical Technique for Decompression, Fixation, and Fusion

Atlantoaxial stability was evaluated in 12 surgically stabilized dogs and 6 control dogs after odontoidectomy and dorsal atlantoaxial ligament separation. The atlantoaxial instabilities were stabilized with transarticular pins from a ventral approach. Cancellous bone grafts harvested from the proximal humerus were used to promote joint fusion. Good joint stability, alignment, and early fusion were documented clinically, radiographically, and histopathologically in stabilized dogs. Because of our consistent results despite variable pin angles, we recommend this technique for use in dogs with atlantoaxial instability requiring surgical stabilization.     

DISSEMINATED IDIOPATHIC SKELETAL HYPEROSTOSIS (DISH) IN A DOG

Spinal and extraspinal manifestations similar to Forestier's disease, or disseminated idiopathic skeletal hyperostosis (DISH), are described in a 4-year-old female Great Dane dog. Radiographic features included linear new bone formation with a smooth wavy contour along the ventral and lateral aspects of vertebral bodies plus hyperostosis at ligamentous attachments in the spine (enthesiophytes) causing bony ankylosis. Periarticular new bone and enthesiopathy were present in extraspinal locations. Clinical signs possibly relate to limitations in motion because of the vertebral fusion and extraspinal arthrosis.     

IMAGE FUSION OF COMPUTED TOMOGRAPHIC AND MAGNETIC RESONANCE IMAGES FOR THE DEVELOPMENT OF A THREE-DIMENSIONAL MUSCULOSKELETAL MODEL OF THE EQUINE FORELIMB

Biomechanical models that compute the lengths and forces of muscle-tendon units are broadly applicable to the study of factors that promote injury and the planning and effects of orthopedic surgical procedures in equine athletes. A three-dimensional (3D) generic musculoskeletal model of the equine forelimb comprised of bony segment, muscle-tendon, and ligament information, was developed based on high-resolution computed tomographic (CT) and T1-weighted magnetic resonance (MR) images from an isolated forelimb of a Thoroughbred racehorse. Image fusion was achieved through coregistration of CT and MR images with an image analysis program (Analyze) by adjustment of the relative position and orientation of fiducial markers visible in both modalities until the mutual information between the images was maximized. 3D surfaces of the bones and origin/insertion sites, centroid paths and volumes of the muscle-tendon and ligamentous structures were obtained from the multimodal (CT/MR) images using semiautomated and manual segmentation combined with sagittal and transverse color-cryosection anatomic images obtained from three other cadaveric equine forelimbs. Once bony and soft-tissue structures were reconstructed in the same coordinate system, data were imported to a software package for interactive musculoskeletal modeling (SIMM). The combination of integrated CT and MR acquisitions and anatomical images provided an accurate and efficient means of generating a 3D model of the musculoskeletal structures of an average-sized equine adult horse.     

Healing of dorsal pancarpal arthrodesis in the dog

The purpose of this study was to assess radiographically the healing process in dogs which had undergone dorsal pancarpal arthrodesis with autologous cancellous bone grafting. The medical records of 17 dogs that had undergone dorsal pancarpal arthrodesis with complication-free dynamic compression plate fixation were reviewed. Postoperative healing was evaluated radiographically. It started five weeks after surgery and progressed for six to 12 weeks in all dogs. After this time period no further progression of healing was observed. Between weeks 6 and 8, bony fusion progressed significantly more rapidly in the intercarpal joint than in the radiocarpal joint. The following criteria had no influence on healing time: gender, age, bodyweight, and immediate versus delayed surgery after trauma. The major difficulties noted with respect to the interpretation of postoperative radiographs were irregular bony bridging, mainly caused by inadequate palmar curettage, and oblique projection of articular surfaces resulting in superimposition of joint spaces and solid bone.     

Proximal interphalangeal arthrodesis in 22 horses

The purpose of this study was to evaluate a new method of internal fixation technique for pastern arthrodesis. Pastern arthrodeses are performed commonly in horses with chronic osteoarthritis of the pastern joint or, in cases of acute traumatic injury to the pastern, in which the weightbearing bony column must be restored. Chronic osteoarthritis of the pastern is a frequent cause of lameness in the equine athlete and is evidenced by chronic lameness localised to the pastern joint, and supported radiographically by periosteal proliferation and loss of joint space. Nonsurgical and surgical treatments have both been described in the literature. Complications following pastern arthrodesis have been reported on several occasions and appear to focus on excessive periarticular exostoses and increased time in a cast due to prolonged time to bony fusion. The hospital records of horses presenting for pastern arthrodesis to the Rood and Riddle Equine Hospital in Lexington, Kentucky, were reviewed and 22 met criteria for inclusion in the study. Horses with chronic osteoarthritis of the proximal interphalangeal joint or horses with an acute traumatic injury to the pastern undergoing pastern arthrodesis with one of the following techniques were included in the study. Horses with severe comminution of the middle phalanx were excluded. Three 5.5 mm cortical bone screws placed in lag fashion alone or in combination with a 4 or 3 hole dynamic compression plate affixed with 4.5 mm cortical bone screws were compared. A lower limb fibreglass cast was applied in all cases. Period in cast, time to return to intended use, complications encountered and outcome were evaluated. Seven of the 8 hindlimbs treated with the combination technique became sound. Three out of 6 of the front limbs treated with the combination technique became sound. Four of the 5 horses with hindlimbs, and one of the 2 with front limbs, treated with screws only returned to their intended use. The type of internal fixation did not appear to influence the overall number of horses returning to the intended level of performance. The period spent in cast and the time to return to soundness were decreased in horses operated on using the combination technique. We concluded that, in the immediate postoperative period, the combination of the parallel screw technique with a dorsally-applied dynamic compression plate provides the most stable and secure fixation, minimising motion, expediting bone remodelling and therefore favouring rapid fusion of that joint.     

An evaluation of chemical arthrodesis of the proximal interphalangeal joint in the horse by using monoiodoacetate.

The use of monoiodoacetate (MIA) for arthrodesis of the proximal interphalangeal joint (PIJ) and the effect of exercise on the degree of fusion were investigated. Eight horses received 3 injections (Weeks 0, 3, 6) of MIA (2 mL; 60 mg/mL) into the right or left front PIJ. Peri-operatively, the horses received phenylbutazone, butorphanol, and abaxial sesamoidean nerve blocks to relieve pain. During the study, the horses were monitored for general health, lameness, and swelling around the injection area. Radiographs were taken biweekly to evaluate bony fusion. Horses were randomly divided into non-exercised and exercised groups. Exercise consisted of 20 minutes of trotting on a treadmill (4 m/s), 3 days per week for 13 weeks. The horses were euthanized at 24 weeks. Slab sections of the PIJ were evaluated grossly and radiographically for bony fusion. Histologic examinations were performed to evaluate articular cartilage. Three horses were excluded from the study after developing soft tissue necrosis around the injection site, septic arthritis, and necrotic tendinitis. The remaining horses remained healthy, developed a grade 1 to 4 lameness with minimal to severe swelling in the PIJ region. All 5 horses showed radiographic evidence of bony fusion, however, no fusion was present when injected joints were examined on postmortem examination. Histologic examination revealed thinning of the cartilage, diffuse necrosis of chondrocytes, with the calcified zone intact. Subjectively, exercise did not influence the degree of cartilage destruction. Based on this study, chemical arthrodesis cannot be advocated in clinical cases because of the high complication rate and lack of bony fusion.     

盐酸赛拉嗪对家兔麻醉效果的研究

[目的]探究盐酸赛拉嗪对家兔的麻醉效果。[方法]选取新西兰兔12只,随机分为耳缘静脉注射（IV）保定组、臀部肌肉注射（IM）保定组、IV未保定组、IM未保定组,每组3只;按照不同给药途径给予家兔3 mg/（kg·BW）盐酸赛拉嗪,给药后保定处理方式为仰卧保定四肢及头部,未保定的家兔自然俯卧;第1次给药后30 min,再以相同给药途径给予家兔2 mg/（kg·BW）盐酸赛拉嗪;于给药前10 min以及第2次给药后5、30、60 min监测家兔基本生命体征及麻醉反应指标。[结果]给予盐酸赛拉嗪后不同时间,4组家兔呼吸频率和脉搏次数与给药前相比均显著（P<0.05）或极显著（P<0.01）降低;给药后60 min IM保定组脉搏次数最低,显著（P<0.05）低于IV未保定组。4组家兔给药后30 min直肠温度与给药前相比均显著（P<0.05）降低;除IV未保定组外,给药后60 min各组家兔直肠温度与给药前相比极显著（P<0.01）降低;给药后60 min IM保定组的直肠温度最低,极显著（P<0.01）低于IV未保定组。IM保定组家兔给药后不同时间均未出现翻正反射、睫毛反射和疼痛反射;IV未保定组在给药后60 min,3只家兔均出现翻正反射、睫毛反射和疼痛反射。IM保定组家兔的麻醉期最长,显著（P<0.05）长于IV保定组,极显著（P<0.01）长于IV未保定组和IM未保定组。[结论]用盐酸赛拉嗪麻醉家兔时应使用IM给药途径,推荐首次给药剂量为3 mg/（kg·BW）,之后30 min再补充2 mg/（kg·BW）,给药后应即刻保定确实。     

Outcomes and complications associated with ventral screws, pins, and polymethyl methacrylate for atlantoaxial instability in 12 dogs

Clinical outcomes and complications of a technique used for atlantoaxial stabilization were evaluated in a group of 12 dogs. At surgery, the atlantoaxial joint was realigned and rigidly fixated using cortical bone screws, K-wire, and polymethyl methacrylate. Results in nine dogs were graded as excellent. Results in two dogs were judged as good. One dog was euthanized 17 months after surgery for recurrent cervical pain. Eight dogs had no postoperative complications. The surgical technique described provided an adaptable method for the correction of atlantoaxial instability.     

A modified ventral approach to the atlantoaxial junction in the dog

Objective— To describe and evaluate a surgical technique using a modified ventral approach for stabilization of the atlantoaxial (AA) junction in dogs with AA subluxation.
Study Design— Retrospective study.
Animals— Dogs (n=5) with AA subluxation.
Methods— Medical records (2000–2006) of 5 dogs with AA treated by stabilization via a right parasagittal approach were reviewed and outcome assessed by clinical examination and phone interviews with owners.
Results— The AA joint was clearly visualized and fixation devices were placed in all dogs. A right parasagittal approach provided excellent access to the AA junction and avoided dissection around the thyroid gland, trachea, and recurrent laryngeal nerve. Recovery was considered good to excellent by owners, and dogs returned to good function.
Conclusions— A right parasagittal approach to the AA junction provides improved exposure and allows for surgical stabilization with minimal complications.
Clinical Relevance— In dogs that require surgical stabilization of the AA joint, a right parasagittal approach should be considered. This approach offers advantages over the standard ventral median approach by improved surgical exposure, less dissection, and provides protection of vital structures during insertion of fixation devices used for ventral AA stabilization.     

猪瘟病毒E2蛋白抗原单表位基因的融合表达及其免疫活性的研究

利用基因搭桥技术，在Klenow DNA聚合酶作用下，分别合成猪瘟病毒E2蛋白的3个抗原表位基因，并与原核表达载体pGEX-3X进行连接、转化和筛选鉴定，构建了3个重组质粒pGEX-C、pGEX-D和pGEX-E。在IPTG的诱导下.实现了可溶性蛋白的融合表达(GST-C、GSTD、GST-E)，以GST亲和层析柱对融合蛋白进行纯化。应用ELISA和Western-blot检测证实：E抗原表位基因表达的融合蛋白GST-E具有免疫学活性，而C和D的抗原表位基因虽然都表达了融合蛋白GST-C和GSTD，但未检测到免疫学活性。免疫攻毒保护试验表明：融合蛋白GST-E具有一定的免疫保护功能，为多表位疫苗的研究奠定了基础。     

Magnetic resonance imaging of the ligamentous structures of the occipitoatlantoaxial region in the dog

Our objectives were to establish a magnetic resonance (MR) protocol for the examination of, and then describe, the normal ligaments and the supporting structures of the occipitoatlantoaxial region. This was done in 10 cadaver dogs. In addition, MR images of three patients with cervical pain localized to the occipitoatlantoaxial region are included to provide examples of ligamentous abnormalities. All ligaments were hypointense in all pulse sequences. The apical, dorsal atlantoaxial, and dorsal longitudinal vertebral ligaments were seen best in the sagittal T1W and PD-weighted images. The transverse ligament was best visualized in the transverse plane in all pulse sequences and appeared to be confluent with the dorsal longitudinal vertebral ligament dorsal to the dens in the sagittal plane. A 20° dorsal plane reconstructed image in 0.6-mm slice thickness was necessary to visualize the alar ligaments, which were visible in 9/10 dogs. The dorsal longitudinal vertebral ligament appeared continuous with the apical ligament and tectorial membrane. Abnormalities in clinically affected dogs included thickening of the alar ligaments, absence of transverse ligament and elongation, and irregularity of the apical ligament.     

Lumbar interbody expanding cage. A preliminary study on an animal model

Interbody fusion devices are used in human medicine for treating degenerative diseases of the spine. Currently, there is not a universally accepted assessment tool for determining fusion, and the definitive criteria for diagnosing a successful interbody fusion remain controversial. The aim of this study was to describe microscopic and helical computed tomography (CT) imaging in the assessment of lumbar interbody fusion using cylindrical threaded titanium expanding cage in sheep. One cylindrical threaded expanding titanium cage (Proconcept--SA, Orange, France) was inserted through a transperitoneal approach after radical discectomy and packed with cancellous bone autograft in five adult sheep. The subjects were euthanatized after three, six, 12, 18 and 24 months. CT images revealed lumbar fusion at 12 months post operation, whereas microscopic evaluations indicated the presence of lumbar fusion at 18 months. CT and histological grades were the same in 65% of the cases observed. There were not a significant difference between CT, histological and micro radiographic grades. Helical CT scanning can be considered to be a suitable method for the monitoring of lumbar fusion as it enables observation of the deposition of bony bridging within the cage.     

Cervical Vertebral Osteomyelitis With Secondary Septic Arthritis of the Atlantoaxial Joint in a Foal: A Case Report

A 36-day-old, 100-kg Thoroughbred colt was presented with a sudden onset of abnormal head carriage and pyrexia. Radiography revealed an osteomyelitis of the vertebral body of the second cervical vertebra. Ultrasonography revealed abscessation in the region of the atlantoaxial articulation on the left side, and fluid aspirated from the abscess confirmed suppurative inflammation. Surgical management was not feasible on economic grounds, and therefore this case was managed with aggressive medical therapy based on the most likely pathogens involved. To provide prolonged antibiotic therapy within the client’s budget, the antibiotic flucloxacillin (Staphlex, 500 mg) was used at a dose of 10 mg/kg by mouth, three times daily. Thirty-eight days after first presentation, the foal was euthanized because of chronic pain and deterioration in neurologic signs. A diagnosis of chronic osteomyelitis of the body of the second cervical vertebra (axis) was made with concurrent septic arthritis of the atlantoaxial joint involving the articular surface of the first cervical vertebra (atlas) and cervical myelopathy of the spinal cord within the first two vertebrae. No pathogens were isolated post mortem. This is the first report to describe the use of flucloxacillin in a foal. Although the outcome was fatal, the medical therapy provided could be considered successful at sterilizing the bony lesion.     

Thermal stimulation at 39°C facilitates the fusion and elongation of C2C12 myoblasts

The aim of this study was to determine the effect of thermal stimulation at 39°C on the fusion and elongation of skeletal muscle cells. During a 5 day differentiation process of C2C12 cells, nine groups subjected to varying lengths of thermal stimulation at 39°C were established. Afterward, all groups were immunostained using anti‐muscle heavy‐chain antibody to test for myotube formation. Quantification of the myotube area demonstrated a significant increase in the group subjected to thermal stimulation at 39°C during the latter half of the differentiation compared with the control group, but the fusion index was significantly higher in the group that received hyperthermic treatment during the first half of the differentiation period. Moreover, the longitudinal length of myotubes was significantly increased in the groups that were subjected to thermal stimulation at 39°C during the latter half of the differentiation period. The distance between the center of myotubes and the nucleus farthest away from the center was substantially extended in the group receiving thermal stimulation at 39°C only on the fourth day of the differentiation. Together, these results demonstrate that thermal stimulation at 39°C facilitates myoblast fusion and elongation.