OBJECTIVE To provide an objective, quantitative morphometric description of the caudal cervical intervertebral disk (IVD) spaces of dogs. SAMPLE Vertebral specimens consisting of C4 through C7 from 5 medium-sized dogs. PROCEDURES CT images were obtained with the specimens positioned in neutral, flexion, extension, and lateral bending positions. Size and shape of the cranial and caudal end plates, angle between the end plates (IVD wedge angle), and craniocaudal distance (IVD width) between end plates for the 4 loading positions were measured and compared for the 3 segments (C4-5, C5-6, and C6-7). RESULTS End plate size and shape, IVD wedge angle, and IVD width were not significantly different among the 3 segments. Caudal cervical end plates were consistently larger than cranial cervical end plates. The IVD wedge angle ranged from −4.8° to 15.2°. Flexion induced a reduction in IVD width in the ventral portion of the IVD, whereas extension induced a decrease in width in the dorsal portion of the IVD. Central IVD width remained unchanged among the loading positions. CONCLUSIONS AND CLINICAL RELEVANCE Unique morphometric and dynamic characteristics of the caudal cervical IVD space of dogs were detected. These findings may help investigators when designing IVD prostheses for dogs with cervical spondylomyelopathy.

Objective: To investigate the relationship between runt-related transcription factor 2 (RUNX2) expression in canine nucleus pulposus (NP) cells and intervertebral disk aging in chondrodystrophoid dogs. Animals: 7 healthy Beagles (mean age, 35.6 months) and 11 Dachshunds with herniated disks (mean age, 61 months). Procedures: All dogs underwent MRI examination of the thoracic and lumbar vertebral column immediately before sample collection under general anesthesia. The disk center–to–CSF T2-weighted signal intensity ratio was determined for healthy Beagles. Samples of NP were obtained from nonherniated disks in healthy Beagles and from herniated disks during surgical treatment of hospitalized Dachshunds. Samples were evaluated for RUNX2 and matrix metalloproteinase 13 transcript expression via reverse transcriptase PCR assay; RUNX2 protein expression was evaluated via immunohistochemical analysis, and correlation between these variables and age of dogs was evaluated. A 3′ and 5′ rapid amplification of cDNA ends method was used to identify the RUNX2 coding region. Results: RUNX2 cDNA had > 97% conservation with the human cDNA sequence and approximately 95% conservation with the mouse cDNA sequence; RUNX2 and matrix metalloproteinase 13 mRNA expression and RUNX2 protein expression in NP cells were positively correlated with age. The disk center–to–CSF T2-weighted signal intensity ratio was negatively correlated with RUNX2 protein expression in the NP of healthy dogs. Conclusions and Clinical Relevance: Results indicated that RUNX2 mRNA and protein expression in the NP are enhanced in aging intervertebral disks in dogs.

Objective—To compare biomechanical characteristics of vertebral segments after vertebral body plating or laminar stabilization following complete incision of the annulus fibrosus. Sample—Vertebral segments from T13 through L3 obtained from 18 canine cadavers. Procedures—A 4-point bending moment was applied in flexion and extension to the intact vertebral segments to determine a baseline range of motion (ROM) and neutral zone (NZ). Vertebral columns were then destabilized by creating a defect in the intervertebral disk via complete incision of the ventral aspect of the annulus fibrosus. The bending moment was applied again after stabilization was accomplished via vertebral body plating or with laminar stabilization (n = 9 vertebral segments/stabilization technique). The ROM and NZ were compared with their baseline values and among treatment groups. Finally, load-to-failure testing was performed in flexion. Results—Mean relative ROM and NZ for segments treated with laminar stabilization were significantly lower than those for segments treated with vertebral plates. Conclusions and Clinical Relevance—Analysis of in vitro results suggested that laminar stabilization of vertebral segments provided greater stiffness than did vertebral body plating.

OBJECTIVE To investigate the effects of intervertebral distraction screw (IDS) fixation of the lumbosacral joint (LSJ) on the intervertebral foraminal area (IFA) and intervertebral stabilization of the LSJ and adjacent lumbar segments in dogs. ANIMALS 7 healthy Beagles. PROCEDURES Dorsal laminectomy was performed at the LSJ in each dog to expose the intervertebral disk. The IDS was then inserted into the L7-S1 disk. Computed tomography was performed before and after laminectomy and after IDS insertion (intact, laminectomy, and IDS conditions, respectively) to measure the intervertebral range of motion (ROM) and intervertebral distance (ID) at L7-S1, L6-7, and L5-6 with the LSJ in a flexed and extended position. The intervertebral foramina stenosis rate was calculated from the intervertebral foramina area in entrance, middle, and exit zones. Results were compared among conditions. RESULTS The ROM at L7-S1 after IDS insertion was lower than that observed before and after laminectomy; no other differences were identified among conditions. With the LSJ in the flexed position, the ID at L7-S1 was larger after IDS insertion than before and after laminectomy; no other differences in ID were identified. In all evaluated zones, the stenosis rate was lower after IDS insertion than before and after laminectomy. No differences in ROM, ID, and stenosis rate were identified among conditions at L6-7 or L5-6. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that IDS fixation of the LSJ restricted lumbosacral ROM and prevented decreases in lumbosacral ID and IFA in healthy dogs. There were no changes at L6-7 and L5-6.

OBJECTIVE To characterize and compare MRI susceptibility artifacts related to titanium and stainless steel monocortical screws in the cervical vertebrae and spinal cord of canine cadavers. SAMPLE 12 canine cadavers. PROCEDURES Cervical vertebrae (C4 and C5) were surgically stabilized with titanium or stainless steel monocortical screws and polymethylmethacrylate. Routine T1-weighted, T2-weighted, and short tau inversion recovery sequences were performed at 3.0 T. Magnetic susceptibility artifacts in 20 regions of interest (ROIs) across 4 contiguous vertebrae (C3 through C6) were scored by use of an established scoring system. RESULTS Artifact scores for stainless steel screws were significantly greater than scores for titanium screws at 18 of 20 ROIs. Artifact scores for titanium screws were significantly higher for spinal cord ROIs within the implanted vertebrae. Artifact scores for stainless steel screws at C3 were significantly less than at the other 3 cervical vertebrae. CONCLUSIONS AND CLINICAL RELEVANCE Evaluation of routine MRI sequences obtained at 3.0 T revealed that susceptibility artifacts related to titanium monocortical screws were considered mild and should not hinder the overall clinical assessment of the cervical vertebrae and spinal cord. However, mild focal artifacts may obscure small portions of the spinal cord or intervertebral discs immediately adjacent to titanium screws. Severe artifacts related to stainless steel screws were more likely to result in routine MRI sequences being nondiagnostic; however, artifacts may be mitigated by implant positioning.

OBJECTIVE To evaluate the effects of postoperative photobiomodulation therapy and physical rehabilitation on early recovery variables for dogs after hemilaminectomy for treatment of intervertebral disk disease. ANIMALS 32 nonambulatory client-owned dogs. PROCEDURES Dogs received standard postoperative care with photobiomodulation therapy (n = 11), physical rehabilitation with sham photobiomodulation treatment (11), or sham photobiomodulation treatment only (10) after surgery. Neurologic status at admission, diagnostic and surgical variables, duration of postoperative IV analgesic administration, and recovery grades (over 10 days after surgery) were assessed. Time to reach recovery grades B (able to support weight with some help), C (initial limb movements present), and D (ambulatory [≥ 3 steps unassisted]) was compared among groups. Factors associated with ability to ambulate on day 10 or at last follow-up were assessed. RESULTS Time to reach recovery grades B, C, and D and duration of postoperative IV opioid administration did not differ among groups. Neurologic score at admission and surgeon experience were negatively associated with the dogs' ability to ambulate on day 10. The number of disk herniations identified by diagnostic imaging before surgery was negatively associated with ambulatory status at last follow-up. No other significant associations and no adverse treatment-related events were identified. CONCLUSIONS AND CLINICAL RELEVANCE This study found no difference in recovery-related variables among dogs that received photobiomodulation therapy, physical rehabilitation with sham photobiomodulation treatment, or sham photobiomodulation treatment only. Larger studies are needed to better evaluate effects of these postoperative treatments on dogs treated surgically for intervertebral disk disease.

Objective—To evaluate the reliability of the Thompson system for use in grading the gross pathological changes of intervertebral disk (IVD) degeneration in dogs and to investigate the agreement between gross pathological findings and low-field (0.2-T) magnetic resonance imaging (MRI) indings. Sample—Vertebral columns from cadavers of 19 dogs of various ages, breeds, and origins. Procedures—182 intervertebral segments were collected from 19 canine cadavers. Sagittal T2-weighted MRI of the T11 through S1 portion of the vertebral column was performed within 24 hours after the dogs were euthanized. The vertebral columns were subsequently divided in the midsagittal plane, and high-resolution photographs were obtained of each intervertebral segment (end plate—disk—end plate). The MRI images and photographs were graded separately in a blinded manner by 4 observers who used both Pfirrmann and Thompson grading criteria. Results—The interobserver agreement for Thompson scores ranged from 0.76 to 0.88, and the intraobserver agreement ranged from 0.88 to 0.94 (Cohen weighted κ analysis). Agreement between scores for the Pfirrmann and Thompson grading criteria was κ = 0.70. Conclusions and Clinical Relevance—Grading of IVD degeneration in dogs by use of the Thompson system resulted in high interobserver and intraobserver agreement, and scores for the Thompson system had substantial agreement with low-field MRI findings graded by use of the Pfirrmann system. This suggested that low-field MRI can be used to diagnose IVD degeneration in dogs.

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.

OBJECTIVE To determine values of F-wave parameters for the tibial nerve in clinically normal Miniature Dachshunds and those with thoracolumbar intervertebral disk herniation (IVDH). ANIMALS 53 Miniature Dachshunds (10 clinically normal and 43 with various clinical grades of thoracolumbar IVDH). PROCEDURES F-waves were elicited in the interosseous muscles of 1 hind limb in each dog by stimulation of the tibial nerve. F-wave parameters were measured for 32 stimuli/dog, and mean values were calculated. Linear regression was performed to assess correlations between F-wave parameters and clinical severity of IVDH. RESULTS For clinically normal dogs, mean ± SD values of shortest F-wave latency, mean F-wave conduction velocity, mean F-wave duration, and ratio of the mean F-wave amplitude to M response amplitude were 8.6 ± 0.6 milliseconds, 83.7 ± 6.1 m/s, 6.6 ± 1.5 milliseconds, and 9.8 ± 8.5%, respectively. F-wave persistence was 100%. Mean F-wave duration was positively correlated with clinical grade of IVDH. Linear regression yielded the following regression equation: F-wave duration (milliseconds) = 6.0 + 2.7 × IVDH grade. One dog with grade 2 IVDH had a mean F-wave duration shorter than that of all 5 dogs with grade 1 IVDH; 1 dog with grade 3 IVDH had a longer duration than that of all 10 dogs with grade 4 IVDH. CONCLUSIONS AND CLINICAL RELEVANCE Mean F-wave duration was correlated with the severity of inhibitory motor tract dysfunction in the spinal cord of dogs. F-wave examination may be useful for objective functional evaluation of upper motor neurons in the spinal cord.

Objective-To determine the accuracy of neurologic data, survey radiographic results, or both for localization of the site of thoracolumbar intervertebral disk herniation in dogs. Sample-338 dogs with surgically confirmed intervertebral disk herniation from disk spaces T10-11 to L6-7. Procedures-Medical records and archived survey radiographs were reviewed for each case. Data were analyzed with multivariable logistic regression models. Three models were fit to develop subsets of the data consisting of survey radiographic data, neurologic examination data, and a combination of survey radiographic and neurologic examination data. The resulting models were validated by evaluating predictive performance against a validation subset of the data. Results-Models incorporating survey radiographic data and a combination of survey radiographic and neurologic data had similar predictive ability and performed better than the model based solely on neurologic data but resulted in substantial errors in predictions. Conclusions and Clinical Relevance-A combination of neurologic examination data as recorded in the medical records and radiographic data did not enhance predictive performance of multivariable logistic regression models over models limited to radiographic data. Neurologic and radiographic findings should not be used to completely exclude areas in an abnormal spinal cord region from further evaluation with advanced imaging.