Distraction–Fusion for Caudal Cervical Spondylomyelopathy Using an Intervertebral Cage and Locking Plates in 14 Dogs

Objective: To evaluate clinical and radiographic outcome in dogs with caudal cervical spondylomyelopathy (CCSM) treated with an intervertebral fusion cage and locking plates. Study Design: Prospective clinical study. Animals: Large breed dogs (n=14) with CCSM. Methods: Dogs had single level cervical spine distraction/fusion performed using an intervertebral cage with a hollow center filled with cancellous autograft and 2 ventrally applied locking plates. Outcome was measured using neurologic scores and radiographic interpretation 6 weeks, 6 months, and 12 months postoperatively. Results: The surgical procedure was well tolerated in all dogs. Final outcome at 12 months was available in 9 dogs. Five dogs were judged excellent, 1 dog was good, 2 dogs were satisfactory, and 2 dogs were poor because of adjacent segment disease. Four dogs died for reasons unrelated to the procedure. Radiographically, implants remained stable over the entire follow‐up period. The disc space continued to fill with an immature pattern of new bone, which showed progressive increase in opacity and quantity. Subsidence of the cage (median 2 mm) was detected in 9 dogs at 6 weeks and remained unchanged in those that could be followed further. Conclusion: Distraction–fusion of single level CCSM in dogs with a combination of intervertebral cage and ventral locking plates is clinically effective and results in successful bony fusion.     

Cervical Spine Locking Plate Fixation for Treatment of Cervical Spondylotic Myelopathy in Large Breed Dogs

Objective— To describe indirect decompression by means of cervical spine locking plate (CSLP) fixation with vertebral distraction, discectomy, and cancellous block bone grafting in large breed dogs with single caudal cervical dynamic spondylotic lesions diagnosed by myelography with linear traction to the cervical spine, and contrast-enhanced computed tomography.
Study Design— Prospective clinical study.
Animals— Dogs (n=12) with caudal cervical spondylotic myelopathy because of a single dynamic, traction-responsive lesion.
Methods— Single, traction-responsive, caudal cervical spondylotic lesions were treated by vertebral distraction, discectomy, cancellous block bone grafting, and CSLP fixation. Follow-up was obtained by sequential recheck examination by the author or referring veterinarian or by telephone inquiries.
Results— Ten dogs had neurologic improvement after surgery. Indirect decompression by maintained distraction with cancellous block grafting and CSLP fixation was readily accomplished with less risk of blood loss or iatrogenic spinal cord injury than that associated with direct (ventral) decompression. There were no complications of graft intrusion, extrusion or subsidence, implant loosening, foraminal impingement, or end-plate failure. Two dogs that had satisfactory short-term recoveries developed clinical signs associated with adjacent segment disease and were euthanatized. At long-term follow-up, 8 dogs had satisfactory function, either a normal gait or one with slight to moderate proprioceptive deficits.
Conclusions— CSLP fixation with cancellous block interbody grafting is an effective and perhaps safer method of treating single-level, traction-responsive cervical spondylosis in large breed dogs.
Clinical Relevance— CSLP fixation with interbody bone grafting is a viable alternative to other techniques for treatment of single-level, traction-responsive cervical spondylosis.     

Treatment of biologically inactive nonunions by a limited en bloc ostectomy and compression plate fixation: a review of 17 cases

OBJECTIVE: To describe a surgical technique for treatment of biologically inactive nonunions using en bloc ostectomy and compression plate fixation and clinical outcome in 17 dogs. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Seventeen dogs. METHODS: A transverse ostectomy was performed adjacent and parallel to the nonunion to eliminate nonviable tissue and provide a new, viable fracture surface with a minimum circumferential contact area of 315 degrees. With most of the bony column anatomically reconstructed, compression plate fixation was used to stabilize the fracture. Autogenous cancellous bone grafting was used if a fracture gap was present (<45 degrees of missing circumferential bone contact). Resection of bone was limited so that bone shortening was less than 20% of the overall bone length. Clinical and radiographic follow-up evaluations were obtained whenever possible. RESULTS: Complete circumferential bone contact and compression plate fixation was achieved after ostectomy in 12 dogs; cancellous bone graft was used in 5 dogs. En bloc ostectomy sites were radiographically healed in a median time of 2.5 months after surgery in 11 dogs that returned for complete in-hospital follow-up, and progressive healing was observed in 3 other dogs, where in-hospital follow-up was obtained up to 2 months after surgery. These dogs had a median follow-up time of 2 months, at which time 6 dogs had no lameness, 4 had minimal lameness, and one had moderate lameness. No complications occurred, and no implants were removed. CONCLUSIONS: En bloc ostectomy with compression plate fixation was considered successful for the treatment of biologically inactive nonunions. A good to excellent prognosis can be expected with minimal complications. CLINICAL RELEVANCE: Use of an en bloc ostectomy technique for the treatment of biologically inactive nonunions permits easy resection of nonviable tissue. Subsequent fracture stabilization with compression plate fixation resulted in rapid bone healing without complications.     

Facet joint geometry and intervertebral disk degeneration in the L5-S1 region of the vertebral column in German Shepherd dogs

OBJECTIVE: To evaluate the possible association between facet joint geometry and intervertebral disk degeneration in German Shepherd Dogs. ANIMALS: 25 German Shepherd Dogs and 11 control dogs of similar body weight and condition. PROCEDURE: Facet joint angles in the caudal portion of the lumbar region of the vertebral column (L5-S1) were measured by use of computed tomography, and the intervertebral discs were evaluated microscopically. The relationship between facet joint geometry and disk degeneration was evaluated by use of statistical methods. RESULTS: German Shepherd Dogs had significantly more facet joint tropism than control dogs, but an association with disk degeneration was not found. However, German Shepherd Dogs had a different facet joint conformation, with more sagittally oriented facet joints at L5-L6 and L6-L7 and a larger angle difference between the lumbar and lumbosacral facet joints, compared with control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: A large difference between facet joint angles at L6-L7 and L7-S1 in German Shepherd Dogs may be associated with the frequent occurrence of lumbosacral disk degeneration in this breed.     

The effect of cancellous autograft and novel plate design on radiographic healing and postoperative complications in tibial tuberosity advancement for cranial cruciate-deficient canine stifles

Objective: To assess the effect of autogenous cancellous bone graft (autograft) and novel plate use on radiographic healing and complications in tibial tuberosity advancement (TTA) for treatment of cranial cruciate ligament (CrCL)‐deficient stifles in dogs. Study Design: Prospective clinical study. Animals: Consecutive dogs (n=125) with unilateral CrCL‐deficient stifles. Methods: Four treatment groups: CPG, conventional plate with autograft; CPNG, conventional plate without autograft; NPG, novel plate with autograft; NPNG, novel plate without autograft were studied. Radiographs from 60 dogs were scored for healing at 6 and 10 weeks postoperatively; all 125 dogs were assessed for radiographic complications. Variables evaluated for relationship with healing scores and radiographic complications were age, weight, sex, cage and plate size, implant type, and graft use. Results: Dogs with autograft had overall higher healing scores at 6 and 10 weeks. Radiographic complications occurred in 13 dogs (12 minor, 1 major), and were not influenced by graft or novel plate use. Conclusion: Autograft increases healing scores, but was not found to have a significant impact on the rate of complications in TTA. The novel plate was not found to have healing scores or radiographic complication rates significantly different from the conventional plate design.     

Effects of anatomic conformation on three-dimensional motion of the caudal lumbar and lumbosacral portions of the vertebral column of dogs

OBJECTIVE: To determine the association between the 3-dimensional (3-D) motion pattern of the caudal lumbar and lumbosacral portions of the canine vertebral column and the morphology of vertebrae, facet joints, and intervertebral disks. SAMPLE POPULATION: Vertebral columns of 9 German Shepherd Dogs and 16 dogs of other breeds with similar body weights and body conditions. PROCEDURE: Different morphometric parameters of the vertebral column were assessed by computed tomography (CT) and magnetic resonance imaging. Anatomic conformation and the 3-D motion pattern were compared, and correlation coefficients were calculated. RESULTS: Total range of motion for flexion and extension was mainly associated with the facet joint angle, the facet joint angle difference between levels of the vertebral column in the transverse plane on CT images, disk height, and lever arm length. CONCLUSIONS AND CLINICAL RELEVANCE: Motion is a complex process that is influenced by the entire 3-D conformation of the lumbar portion of the vertebral column. In vivo dynamic measurements of the 3-D motion pattern of the lumbar and lumbosacral portions of the vertebral column will be necessary to further assess biomechanics that could lead to disk degeneration in dogs.     

Fluoroscopically Guided Closed Reduction and Internal Fixation of Fractures of the Lateral Portion of the Humeral Condyle: Prospective Clinical Study of the Technique and Results in Ten Dogs

OBJECTIVE: To report a technique for fluoroscopically guided closed reduction with internal fixation of fractures of the lateral portion of the humeral condyle (FLHC) and determine the long-term results in 10 clinical cases. STUDY DESIGN: Prospective clinical case study. ANIMALS: Ten dogs with 11 fractures. METHODS: Fractures of the lateral portion of the humeral condyle were stabilized with transcondylar screws and Kirschner wires. Closed reduction and implant placement were achieved using intraoperative fluoroscopic guidance. After fracture repair, postoperative radiographs were evaluated for articular alignment and implant placement. Dogs were evaluated after surgery by means of lameness scores, elbow range of motion (ROM), radiographic assessment, and owner evaluation of function. RESULTS: Postoperative reduction was considered anatomic in 6 fractures with all other fractures having <1.5 mm of malreduction. Follow-up was available for 9 patients from 9 to 21 months after surgery. All of the fractures had healed. One minor (wire migration) and one major (implant failure) complication occurred. Mean lameness scores were 0 (n = 6), 0.5 (n = 2), and 1 (n = 1) at the time of final follow-up. No significant differences were found in follow-up ROM values between affected and unaffected elbows. All of the dogs in this study regained 90-100% of full function, based on owner assessment. CONCLUSIONS AND CLINICAL RELEVANCE: Fluoroscopic guidance for closed reduction and internal fixation of FLHC in dogs is an effective technique.     

Computed tomographic anatomy of the canine cervical vertebral venous system

Computed tomographic (CT) venography of the cervical vertebral canal was performed in six, clinically normal, adult mixed-breed dogs from 14 to 23 kg. After dogs were euthanized and saline perfused, a gelatin and iothalamate mixture was injected into the right external jugular vein. Contiguous, 4-mm-thick CT images were obtained with dogs in sternal recumbency. Dogs were kept in the same position as for the CT scan and frozen to approximately -8 degrees C. All post-contrast CT images were analyzed using similar bone window and level settings. Additional multiplanar reformatted dorsal images were obtained in all dogs. The frozen cadavers were sectioned through the cervical region extending from the occiput to T1 at approximately 8-mm intervals. The frozen sections were then compared with the CT images. The CT appearance of the normal cervical vertebral venous system was described and illustrated. Components such as the internal vertebral venous plexus, interarcuate veins, intervertebral veins, and vertebral veins were clearly identified on the CT images.     

Hemilaminectomy and vertebral stabilisation for the treatment of thoracolumbar disc protrusion in 28 dogs

Objectives : To evaluate the results of hemilaminectomy and vertebral stabilisation (+/? annulectomy) for the treatment of thoracolumbar disc protrusion. Methods : The medical records of dogs with thoracolumbar annular protrusions treated by hemilaminectomy and vertebral stabilisation were reviewed. Neurological function was assessed 24 hours following surgery. Long‐term follow‐up was by clinical examination or telephone questionnaire. Results : Twenty‐eight dogs fulfilled the criteria. Age ranged from 4 to 12·5 years (median 8 years, mean 7·7 years), bodyweight from 5·1 to 51·5 kg (median 28 kg, mean 27·1 kg), and duration of neurological signs before presentation from 48 hours to 104 weeks (median 5 weeks, mean 9·3 weeks). At presentation 22 dogs were ambulatory and six were non‐ambulatory. Myelography and/or magnetic resonance imaging (MRI) identified 31 thoracolumbar protrusions causing spinal cord compression. Unilateral hemilaminectomy was performed in 27 dogs and bilateral hemilaminectomy in one dog. Partial annulectomy was performed in 24 of 31 protrusions. Stabilisation was performed using vertebral body bone plates in 26 dogs and vertebral body screws and bone cement in two dogs. Internal vertebral venous plexus haemorrhage was recorded in nine dogs. A screw was inadvertently placed into an intervertebral disc in two dogs. Neurological examination 24 hours postoperatively revealed deterioration in pelvic limb motor function in 17 dogs. One dog was euthanatised at the owner’s request 6 days after surgery. Long‐term evaluation of 24 cases was performed 3 to 52 months following surgery (median 21 months, mean 23·9 months). Six dogs had improved from their preoperative status and one had deteriorated as assessed by the authors. Fifteen dogs had improved from their preoperative status and two were unchanged as assessed by owners. Clinical Significance : Hemilaminectomy and vertebral stabilisation are an effective treatment for chronic spinal cord compression due to thoracolumbar annular protrusion in dogs. A temporary deterioration in neurological function is not uncommon following surgery. Internal vertebral plexus haemorrhage and inappropriate vertebral body screw placement are potential complications.     

Association between postoperative outcome and results of magnetic resonance imaging and computed tomography in working dogs with degenerative lumbosacral stenosis

OBJECTIVE: To determine whether results of magnetic resonance imaging (MRI) and computed tomography (CT) are associated with postoperative outcome in working dogs with degenerative lumbosacral stenosis. DESIGN: Prospective cohort study. ANIMALS: 12 dogs treated surgically for degenerative lumbosacral stenosis. PROCEDURE: The lumbosacral vertebral column was examined before surgery by use of MRI and CT and after surgery by use of CT. Outcome, based on performance in standardized training exercises, was assessed 6 months after decompressive surgery. Associations between imaging results and postoperative outcome were determined by use of a Fisher exact test and logistic regression. RESULTS: None of the dogs were able to perform their duties before surgery. By 6 months after surgery, 8 of 12 dogs had been returned to full active duty. Nerve tissue compression was effectively localized by use of CT and MRI. Significant associations between results of imaging studies and postoperative outcome were not identified. CONCLUSIONS AND CLINICAL RELEVANCE: Surgical intervention is justified in high-performance working dogs with degenerative lumbosacral stenosis. However, results of imaging studies may be less important than clinical or surgical factors for predicting outcome in affected dogs.     

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.     

THE RELATIVE SENSITIVITY OF COMPUTED TOMOGRAPHY AND MYELOGRAPHY FOR IDENTIFICATION OF THORACOLUMBAR INTERVERTEBRAL DISK HERNIATIONS IN DOGS

We compared the relative sensitivity of computed tomography (CT) and myelography for identification of disk herniation in dogs. Criteria for patient selection included presurgical CT, myelography, or both and surgical or necropsy confirmation of disk herniation between the T3 and L6 vertebral articulations. Imaging findings were described as positive or inconclusive. Adverse events such as hypotension, cardiac arrhythmias, seizures, death, and lower urinary tract infection were compared between imaging groups. One hundred and eighty-two dogs met the inclusion criteria, with 116 dogs having myelography performed as the initial diagnostic imaging modality and 66 dogs having CT performed as the initial modality. The relative sensitivity for locating the site of disk herniation was 83.6% when myelography was the first test performed and 81.8% when CT was the first test performed. CT was more sensitive than myelography at detecting lesions in chronically affected dogs ( P =0.025). Myelography was more sensitive than CT at detecting lesions in smaller dogs (<5 kg; P =0.004). Dogs that received both imaging modalities were significantly more likely to die or be euthanized compared with myelography alone ( P <0.001). Both myelography and CT are reasonable diagnostic imaging modalities for locating the site of disk herniation. CT should be considered especially in heavier, more chronically affected dogs. The major limitations of this study include lack of randomization to imaging modality and the use of surgical exploration or necropsy as the gold standard.     

Aural Cholesteatoma in Twenty Dogs

Objective— To determine the clinical course in dogs with aural cholesteatoma. Study Design— Case series. Animals— Dogs (n=20) with aural cholesteatoma. Methods— Case review (1998–2007). Results— Twenty dogs were identified. Clinical signs other than those of chronic otitis externa included head tilt (6 dogs), unilateral facial palsy (4), pain on opening or inability to open the mouth (4), and ataxia (3). Computed tomography (CT) was performed in 19 dogs, abnormalities included osteoproliferation (13 dogs), lysis of the bulla (12), expansion of the bulla (11), bone lysis in the squamous or petrosal portion of the temporal bone (4) and enlargement of associated lymph nodes (7). Nineteen dogs had total ear canal ablation–lateral bulla osteotomy or ventral bulla osteotomy with the intent to cure; 9 dogs had no further signs of middle ear disease whereas 10 had persistent or recurrent clinical signs. Risk factors for recurrence after surgery were inability to open the mouth or neurologic signs on admission and lysis of any portion of the temporal bone on CT imaging. Dogs admitted with neurologic signs or inability to open the mouth had a median survival of 16 months. Conclusions— Early surgical treatment of aural cholesteatoma may be curative. Recurrence after surgery is associated with advanced disease, typically indicated by inability to open the jaw, neurologic disease, or bone lysis on CT imaging. Clinical Relevance— Presence of aural cholesteatoma may affect the prognosis for successful surgical treatment of middle ear disease.     

Vertebral distraction-fusion for cervical spondylopathy using a screw and double washer technique

A technique using two interbody washers and a transvertebral screw was utilised to distract the cervical vertebrae and so decompress the spinal cord in 17 dobermann pinschers and three great danes with cervical spondylopathy. Neurological dysfunction was graded (1 to 5) according to the degree of hindlimb ataxia. Myelography showed evidence of spinal cord compression at C6-7 in all dogs and at C5-6 in six dogs. Twenty-three compressive lesions were reduced when traction was applied to the cervical spine. Seventeen dogs improved following surgery and of these 10 improved by two or more grades. Follow-up radiographic studies indicated resorption of end-plate bone and eventual fusion of the vertebral bodies. Displacement of the screw into the vertebral canal, remodelling of the vertebral canal, fracture of C6 ventral spinous process and breakage of the screw were implant associated complications. The distraction-fusion technique with modifications appears to be an effective procedure for the management of cervical spondylopathy in dogs in which the compressive lesion is soft tissue in nature.     

A surgical technique for implantation of the vibrant soundbridge middle ear implant in dogs

Objective: To report a surgical implantation of the Vibrant Soundbridge (VSB) middle ear implant in dogs. Study Design: Pilot study. Animals: Dogs (n=3). Methods: A lateral approach to the tympanic bulla was used to insert the floating mass transducer of the VSB into the tympanic bulla. Using microscopic guidance the transducer was moved to and inserted into the round window niche by manipulation through the acoustic bony meatus, after reflection of the tympanic membrane. VSB position was confirmed by computed tomography (CT) imaging. Results: No intraoperative complications occurred and CT images confirmed correct placement of the VSB. Conclusions: A VSB can be safely implanted in the middle of dogs.     

Radiographic evaluation of the Zurich cementless total hip acetabular component

OBJECTIVE: To radiographically evaluate the Zurich cementless total hip (ZCTH) cup and correlate lucency with clinical signs of implant instability, time since surgery, and implant generation, using zonal analysis. STUDY DESIGN: Retrospective study. ANIMALS: Client-owned dogs (n = 53). METHODS: Radiographs of dogs that had ZCTH arthroplasty (>1 year) were evaluated using zonal analysis, for lucency surrounding the cup-bone interface (number of zones, length, area). Dogs were examined for clinical signs of implant instability (lameness, hip pain). Lucency was correlated with lameness, time after surgery, and implant generation. RESULTS: Radiographs of 68 implants (18 generation I, 50 generation II) were evaluated. Eight dogs were lame (11.8%). Dogs with lameness were more likely to have lucency in > or =2 zones of analysis (per view), have >2 times the average curvilinear length of lucency, and have >4 times the average area of lucency surrounding the implant compared with non-lame dogs. A weak relationship was observed between time after surgery and implant generation; however, there was no relationship between time after surgery and lucency. CONCLUSIONS: Dogs with lameness after ZCTH arthroplasty were more likely to have lucency at the cup-bone interface. Lucency was better evaluated by radiographic projection than zonal analysis. Temporal progression of lucency was weakly correlated with implant generation. CLINICAL RELEVANCE: Dogs with lucency in > or =2 zones of analysis should be evaluated more frequently for clinical signs of implant loosening. Further investigation of serial radiographs after ZCTH arthroplasty is warranted.     

Use of a titanium mesh for cranioplasty following radical rostrotentorial craniectomy to remove an ossifying fibroma in a dog

CASE DESCRIPTION: A 6-year-old Australian Terrier was evaluated for surgical removal of an ossifying fibroma of the left calvarium of 7 months' duration. CLINICAL FINDINGS: Computed tomography revealed invasion of the mass through the left parietal bone and extension into the epidural space of the brain. TREATMENT AND OUTCOME: A left rostrotentorial and frontal bone craniectomy was performed, and the mass was removed, along with a 1-cm margin of grossly normal bone. Cranioplasty was performed with a combination of porcine submucosa, titanium mesh, and screws. The dog recovered from surgery without complications and was discharged 3 days later. The dog was followed up for 24 months after surgery and has remained clinically normal. CLINICAL RELEVANCE: Findings suggested that rostrotentorial craniectomy is a viable option for removal of benign tumors affecting the parietal bones in dogs. Reconstruction of the resulting defect in the calvarium is possible with a combination of porcine submucosa and rigid titanium mesh.     

Cervical Spinal Locking Plate in Combination with Cortical Ring Allograft for a One Level Fusion in Dogs with Cervical Spondylotic Myelopathy

Objective— To evaluate use of a surgical technique commonly used in humans for treatment of cervical spondylotic myelopathy (CSM) in dogs.
Design— Prospective case series.
Animals— Dogs with CSM (n=10).
Methods— Dogs weighing >30 kg that had CSM at 1 vertebral articulation were eligible for inclusion. Dogs had vertebral column distraction/fusion performed using a cortical ring allograft, cancellous autograft, and a spinal locking plate. Dogs were evaluated temporally by repeat neurological examinations and by client perception of postsurgical outcome, determined by telephone interview.
Results— Nine dogs survived the immediate postoperative period. Seven of 8 dogs had moderate to complete improvement without recurrence (mean follow-up, 2.48 years). The most common postsurgical complications were screw loosening (n=4) and plate shifting (2), neither of which required surgical revision. One dog had pseudoarthrosis that may have negatively impacted outcome.
Conclusion— Treatment of single level CSM in dogs with ring allograft and a spinal locking plate system may lead to successful outcomes. The major problems encountered with included cost of the implants and adjusting the system designed for humans to fit the vertebral column of a dog.
Clinical Relevance— For dogs with CSM at a single level, the use of a spinal locking plate in combination with a cortical ring allograft can be an effective surgical treatment. Costs of the implants as well as anatomic differences in dogs make this type of surgery less appealing.