MR-imaging of lumbosacral intervertebral disc degeneration in clinically sound German shepherd dogs compared to other breeds

German shepherd dogs are overrepresented in the group of dogs with cauda equina compression syndrome due to degenerative lumbosacral stenosis. A congenital predisposition for early degeneration of the lumbosacral intervertebral disc has been suspected. Our aims were to assess the morphologic appearance of the lumbosacral intervertebral disc and the lumbosacral junction in healthy German shepherd dogs compared to other breeds and to evaluate for an early onset of degenerative changes. The lumbosacral spine of 110 clinically sound German shepherd dogs and 47 healthy dogs of other large breeds was examined using magnetic resonance (MR) imaging. The degeneration of every intervertebral disc was graded using an established classification system. Signal intensity of the entire lumbosacral disc and the nucleus pulposus was determined independently. Lumbosacral malalignment was assessed according to a previously described method. The findings for the German shepherd dogs were compared to those of the other breeds. Although most dogs were younger than 18 months at the date of examination, significantly higher grades of degeneration were detected for the lumbosacral intervertebral disc of German shepherd dogs (P < 0.003). Degeneration of the lumbosacral intervertebral disc was independent from findings in the other lumbar discs. We conclude that the German shepherd dog has a predisposition for degenerative changes in the lumbosacral intervertebral disc.     

QUANTITATIVE SURVEY RADIOGRAPHIC EVALUATION OF THE LUMBOSACRAL SPINE OF NORMAL DOGS AND DOGS WITH DEGENERATIVE LUMBOSACRAL STENOSIS

Survey radiographic studies of the lumbosacral region for 93 normal dogs and for 26 dogs with confirmed degenerative lumbosacral stenosis were reviewed. Normal dogs were divided into 9 groups based on age and body weight. For normal dogs, increasing age and body weight were associated with a decreased ability to extend the lumbosacral joint and with increased incidence and severity of spondylosis. Transitional lumbosacral vertebrae and evidence of lumbosacral disc space collapse were very infrequent findings, and the pivot point for lumbosacral motion was consistently centered over the lumbosacral disc space. Relative to an age/weight matched sub-population of normal dogs, dogs with degenerative lumbosacral stenosis had similar mean normalized lumbosacral vertebral canal height, larger mean neutral lumbosacral angle, decreased extension of the lumbosacral joint, increased flexion of the lumbosacral joint, reduced lumbosacral range of motion, increased lumbosacral dynamic malalignment, higher incidence and severity of spondylosis, higher incidence of transitional vertebrae, and higher incidence of lumbosacral disc space collapse. A logistic model based strictly on radiographic parameters was able to discriminate normal from affected dogs with an overall accuracy rate of 86%.     

Phenotyping of lumbosacral stenosis in Labrador retrievers using computed tomography

Deep phenotyping tools for characterizing preclinical morphological conditions are important for supporting genetic research studies. Objectives of this retrospective, cross‐sectional, methods comparison study were to describe and compare qualitative and quantitative deep phenotypic characteristics of lumbosacral stenosis in Labrador retrievers using computed tomography (CT). Lumbosacral CT scans and medical records were retrieved from data archives at three veterinary hospitals. Using previously published qualitative CT diagnostic criteria, a board‐certified veterinary radiologist assigned dogs as either lumbosacral stenosis positive or lumbosacral stenosis negative at six vertebral locations. A second observer independently measured vertebral canal area, vertebral fat area, and vertebral body area; and calculated ratios of vertebral canal area/vertebral body area and vertebral fat area/vertebral body area (fat area ratio) at all six locations. Twenty‐five dogs were sampled (lumbosacral stenosis negative, 11 dogs; lumbosacral stenosis positive, 14 dogs). Of the six locations, cranial L6 was the most affected by lumbosacral stenosis (33%). Five of six dogs (83%) with clinical signs of lumbosacral pain were lumbosacral stenosis positive at two or more levels. All four quantitative variables were significantly smaller at the cranial aspects of the L6 and L7 vertebral foramina than at the caudal aspects (P < 0.0001). Fat area ratio was a significant predictor of lumbosacral stenosis positive status at all six locations with cranial L6 having the greatest predictive value (R² = 0.43) and range of predictive probability (25–90%). Findings from the current study supported the use of CT as a deep phenotyping tool for future research studies of lumbosacral stenosis in Labrador retrievers.     

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.     

Lumbosacral myelography in dogs--a safer technique

In search of a safer myelographic technique, we performed myelography via the lumbosacral intervertebral space. Eight dogs, in which the backflow of cerebrospinal fluid was observed, received contrast media via the lumbosacral intervertebral space. The subarachnoid contrast columns were successfully observed in 6 dogs. During and after examination, no physiological changes or neurological signs were observed. We recommend that the lumbosacral intervertebral space be selected first before implementing the conventional lumbar myelography.     

Association of cauda equina compression on magnetic resonance images and clinical signs in dogs with degenerative lumbosacral stenosis

Magnetic resonance imaging (MRI) was used to examine the lumbosacral spine of 27 dogs with degenerative lumbosacral stenosis. Four normal dogs were also similarly imaged. Compression of the soft-tissue structures within the vertebral canal at the lumbosacral space was assessed in two ways: by measuring dorsoventral diameter on T1-weighted sagittal images and cross-sectional area on transverse images. The severity of the clinical signs was compared to the severity of cauda equina compression. No significant correlation was found. It is concluded that degree of compression as determined by MRI at time of presentation is independent of disease severity.     

Degenerative lumbosacral stenosis in 18 dogs

Eighteen dogs with degenerative lumbosacral stenosis were presented to the University of Queensland Small Animal Clinic (UQSAC) over a three-year period. Presenting clinical signs included lumbosacral pain (89 per cent), hindlimb paresis and proprioceptive deficits (56 per cent), lameness (49 per cent), flaccid tails (22 per cent), and urinary dysfunction (16 per cent). All 18 dogs were treated by decompressive laminectomy. Two dogs were also treated by a pin fixation-fusion technique. The major compressive lesion was a type II disc protrusion (72 per cent). Seventeen dogs (94 per cent) showed improvement postoperatively with minimal complications. Confirmation of diagnosis is difficult in that many aged dogs without clinical signs show radiographic signs compatible with stenosis.     

Synovial cysts associated with cauda equina syndrome in two dogs

OBJECTIVE: To report synovial cysts associated with cauda equina syndrome in 2 dogs. STUDY DESIGN: Clinical cases. ANIMALS: Two German Shepherd dogs. METHODS: After magnetic resonance imaging detection, cysts were surgically removed via dorsal laminectomy. RESULTS: Six and 8 months after surgery, both dogs were free of clinical signs and no pain was elicited on lumbosacral joint manipulation. CONCLUSION: Although described in dogs, cysts at the lumbosacral joint might cause compression of the cauda equina nerve roots. Radical excision of the cyst capsule can result in resolution of clinical signs. CLINICAL RELEVANCE: Synovial cysts should be considered in the differential diagnosis of dogs with cauda equina compression syndrome when lumbosacral degenerative joint disease is present.     

Surgical treatment of lumbosacral foraminal stenosis using a lateral approach in twenty dogs with degenerative lumbosacral stenosis

Objectives— To describe clinical signs, magnetic resonance imaging (MRI) and surgical findings using a lateral approach to the lumbosacral intervertebral foramen and to evaluate clinical outcomes in dogs with or without concurrent dorsal decompression and annulectomy.
Study Design— Retrospective study.
Animals— Dogs (n=20) with degenerative lumbosacral stenosis (DLSS).
Methods— Medical records (2002–2006) of dogs that had lumbosacral lateral foraminotomy alone or in combination with dorsal decompression were reviewed. Degree of dysfunction was assessed separately for each pelvic limb; dogs with unilateral signs were included in group A, those with bilateral signs in group B. Retrieved data were: signalment, history, neurologic status on admission, 3 days, 6 weeks, and 6 months postoperatively, duration of clinical signs, results of MRI, surgical site(s), intraoperative findings, and outcome.
Results— Based on the clinical and MRI findings unilateral foraminotomy was performed in 8 dogs, bilateral foraminotomy in 1 dog, unilateral foraminotomy with concurrent dorsal decompression in 7 dogs, and bilateral foraminotomy with concomitant dorsal decompression in 4 dogs. Surgery confirmed the presence of foraminal stenosis in all dogs, with osteophyte formation and soft tissue proliferations being the most common lesions. Outcome was good to excellent in 19 dogs and poor in 1 dog. Mean follow-up was 15.2 months (range, 6–42 months).
Conclusion— Lateral foraminotomy addresses compressive lesions within exit and middle zones of the lumbosacral foramen.
Clinical Relevance— Successful surgical management of DLSS is dependent on recognition and correction of each of the compressive lesions within the lumbosacral junction.     

MAGNETIC RESONANCE IMAGING OF ARTICULAR PROCESS JOINT GEOMETRY AND INTERVERTEBRAL DISK DEGENERATION IN THE CAUDAL LUMBAR SPINE (L5–S1) OF DOGS WITH CLINICAL SIGNS OF CAUDA EQUINA COMPRESSION

The geometry of the lumbosacral region has been suspected to play a role in the development of degenerative lumbosacral stenosis in the dog. In this study, 50 dogs (21 German Shepherd dogs and 29 dogs of other breeds) with clinical signs of cauda equina compression were studied by magnetic resonance (MR) imaging. The orientation of the articular process joints in the L5-S1 region and the angle difference between two adjacent motion segments were calculated. Intervertebral disc degeneration of the same region was identified and classified in four stages. A positive association between MR-imaging stage and articular process joint angle difference in the transverse plane was found in the two groups of animals. German Shepherd dogs and dogs of other breeds had different geometry of the lumbosacral region with different articular process joint angles in the transverse plane and statistically different stages of disc degeneration.     

COMPARISON OF THREE RADIOGRAPHIC CONTRAST PROCEDURES IN THE EVALUATION OF THE CANINE LUMBOSACRAL SPINAL CANAL

Lumbar myelography, intraosseous caudal vertebral venography, and epidurography were performed in 12 normal, mature mixed-breed dogs. The radiographic appearance of the lumbosacral region was evaluated in both the lateral and ventrodorsal projections. These three radiographic contrast procedures were repeated in the same dogs after the introduction of a silicone mass into the spinal canal at the lumbosacral junction. The radiographic findings were compared with postmortem findings to determine which contrast procedure was most useful in detecting the mass in the lumbosacral spine. None of the procedures evaluated consistently produced good-quality studies in the normal dogs. After introduction of the silicone mass, lumbosacral epidurography yielded the largest number of positive correlations. However, the sensitivity of lumbosacral epidurography was less than 50% in the lateral projection and less than 20% in the ventrodorsal projection. Though none of the procedures were consistently helpful in the diagnosis of the lumbosacral masses, lumbosacral epidurography has the most potential to give consistently good-quality studies and thereby a greater probability of detecting an abnormality.     

CT measures of lumbosacral paraspinal muscle size are not correlated with CT measures of lumbosacral stability in military working Labrador Retrievers

Management of degenerative lumbosacral stenosis in military working dogs more frequently utilizes core conditioning exercise programs. Future research on the effectiveness of these programs may benefit from an improved understanding of relationships between paraspinal muscle size and lumbosacral stability. The aim of this retrospective, secondary analysis, cross‐sectional study was to test the following hypotheses related to CT measures: (a) transverse paraspinal muscle area ratios differ between hip flexion and extension, (b) lumbosacral angle and lumbosacral range of motion differ by lumbosacral angle measurement technique, and (c) transverse paraspinal muscle area ratios are correlated with CT measures of lumbosacral stability (parasagittal and parasagittal oblique foraminal area changes) regardless of hip position and with lumbosacral range of motion within each hip position. Lumbosacral CT scans in hip flexion and extension were retrieved from a previous prospective study of military working Labrador Retrievers. A single observer performed triplicate measurements of transverse paraspinal muscle area ratios, parasagittal foraminal area, and parasagittal oblique foraminal area for each hip position and another observer independently performed triplicate measurements of lumbosacral angle and lumbosacral range of motion at L7‐S1 using two published techniques. Thirty‐nine dogs were analyzed and significant differences were identified between hip flexion and extension for all mean transverse paraspinal muscle area ratio values (P ≤ .05). Mean lumbosacral angles also significantly differed between the published techniques in both hip flexion and extension. When comparing mean lumbosacral range of motion values, one of the published techniques produced significantly smaller values. No significant correlation was found between transverse paraspinal muscle area ratios and parasagittal foraminal area changes, parasagittal oblique foraminal area changes, or lumbosacral range of motion. These results should be considered when designing studies using these CT measures in military working dogs.     

Three-dimensional motion pattern of the caudal lumbar and lumbosacral portions of the vertebral column of dogs

OBJECTIVE: To evaluate the 3-dimensional motion pattern including main and coupled motions of the caudal lumbar and lumbosacral portions of the vertebral column of dogs. ANIMALS: Vertebral columns of 9 German Shepherd Dogs (GSDs) and 16 dogs of other breeds with similar body weights and body conditions. PROCEDURE: Main and coupled motions of the caudal lumbar and lumbosacral portions of the vertebral column (L4 to S1) were determined by use of a testing apparatus that permitted precise application of known pure moments to the vertebral column. Motion was compared between GSDs and dogs of other breeds. RESULTS: All specimens had a similar motion pattern consisting of main motion and a certain amount of coupled motion including translation. Vertebral columns of GSDs had significantly less main motion in all directions than that of dogs of other breeds. Translation was similar in GSDs and dogs of other breeds and was smallest at the lumbosacral motion segment. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that motion in the caudal lumbar and lumbosacral portions of the vertebral column of dogs is complex and provided a basis for further studies evaluating abnormal vertebral columns.     

A follow-up study of neurologic and radiographic findings in working German Shepherd Dogs with and without degenerative lumbosacral stenosis

OBJECTIVE: To identify radiographic abnormalities associated with degenerative lumbosacral stenosis (DLSS) in German Shepherd Dogs (GSDs) and determine whether specific radiographic abnormalities could be used to identify dogs at risk of developing DLSS. DESIGN: Cohort study. ANIMALS: 33 GSDs working as police dogs. PROCEDURES: Results of physical, neurologic, and orthopedic examinations were used to identify dogs with DLSS. Survey radiography of the lumbosacral junction was performed, and radiographs were compared with radiographs obtained 3 years earlier. RESULTS: DLSS was diagnosed in 15 of the 33 (45%) dogs. Thirteen of the 15 dogs with DLSS and 14 of the 18 dogs without DLSS had radiographic abnormalities of the lumbosacral junction. Twenty-two (67%) dogs were able to perform unrestricted duties, including 3 dogs with suspected DLSS. Six (18%) dogs had been excluded from active duty during the period of surveillance because of DLSS. Significant progression in specific clinical and radiographic signs was detected, but multiple logistic regression analysis did not identify any radiographic signs that could be used to predict the development of DLSS. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that survey radiography cannot be used to predict development of DLSS in working GSDs.     

Surgical treatment of lumbosacral instability caused by discospondylitis in four dogs

OBJECTIVE: To describe a surgical technique involving distraction and stabilization of the lumbo-sacral vertebral segment using an external skeletal fixator in dogs with lumbosacral instability caused by discospondylitis. STUDY DESIGN: Retrospective clinical study. ANIMALS: Four client-owned dogs. METHODS: Medical records of all dogs diagnosed with discospondylitis from 1994 to 1997 were identified and reviewed. Four dogs with lumbosacral discospondylitis requiring surgical treatment were then specifically studied. Surgical technique, clinical signs, preoperative diagnostic investigation, radiographic findings, and the results of short-term and long-term reevaluations were recorded. RESULTS: Twelve dogs with discospondylitis were identified, 4 of which had lumbosacral discospondylitis. These 4 dogs underwent surgical distraction and stabilization because they failed to respond to medical treatment. Three dogs received a cancellous bone graft between L7 and S1 and had rapid interbody fusion of this vertebral segment. The dog that did not receive a graft did not have interbody fusion at the time of fixator removal. This did not affect the final clinical outcome. Lumbosacral pain and neurological deficits present before surgery rapidly subsided after the procedure. All dogs received concurrent antibiotic treatment for a minimum of 4 weeks. All dogs were clinically normal at the time of fixator removal and all continued to do well during the follow-up period (8-48 months; mean, 27.5 months). CONCLUSION AND CLINICAL RELEVANCE: Lumbosacral discospondylitis may not respond well to conservative treatment because of the mobility of the affected space. Surgical treatment involving distraction and stabilization to obtain intervertebral fusion is very effective in treating lumbosacral instability caused by discospondylitis.     

Congenital malformations of the lumbosacral vertebral column are common in neurologically normal French Bulldogs,English Bulldogs,and Pugs,with breed‐specific differences

Congenital vertebral malformations are common findings on diagnostic imaging of the vertebral column in “screw‐tailed” brachycephalic dogs. The aims of this study were to evaluate the prevalence and anatomical characteristics of lumbosacral congenital vertebral malformations in French Bulldogs, English Bulldogs, and Pugs presenting for problems unrelated to spinal disease, as well as possible associations with the degree of tail malformation, lumbosacral intervertebral disc herniation, or spondylosis deformans. In this retrospective cross‐sectional study, CT scans of vertebrae L6 to S3 and of the coccygeal vertebrae were reviewed for type of congenital vertebral malformations (hemivertebrae, block vertebrae, lumbosacral transitional vertebrae, and spina bifida), lumbosacral intervertebral disc herniation, lumbosacral spondylosis deformans, and degree of tail malformation. In 76 (51.0%) of the 149 included dogs (53 French Bulldogs, 37 English Bulldogs, and 59 Pugs) at least one type of congenital vertebral malformations was found, with lumbosacral transitional vertebrae being the most common (34.2%). There was a significantly higher prevalence of lumbosacral transitional vertebrae (54.2%) and lower prevalence of hemivertebrae (1.7%) in Pugs compared to English (13.5% and 24.3%, respectively) and French Bulldogs (26.4% and 32.0%, respectively). Tail malformation was significantly more severe in dogs with evidence of hemivertebrae. Congenital vertebral malformations are a common finding in the lumbosacral vertebral column of French Bulldogs, English Bulldogs, and Pugs. These anatomical variances need to be considered when interpreting diagnostic studies and when planning for neurosurgical and neurodiagnostic procedures. Furthermore, this study suggests a possible association between the degree of tail malformation and lumbosacral hemivertebrae.     

Kinematic study of back movement in clinically sound malinois dogs with consideration of the effect of radiographic changes in the lumbosacral junction

Objective— To determine thoracolumbar spinal movement in dogs and the influence of subclinical radiographic changes involving the lumbosacral junction. Study Design— Experimental study. Animals— Clinically sound Malinois dogs (n=22). Methods— Kinematic analysis of markers on the spinal processes of C7, T6, T13, L3, L7, and S3 was performed while dogs were walking on a treadmill. Range of motion (ROM) in the transverse and vertical direction and the time of occurrence (TOO) of the maximal marker position were calculated. ROM and TOO of angulations formed by the corresponding markers were calculated. Initial kinematic analysis was performed without knowledge of the radiographic changes, and then data were reanalyzed to determine whether vertebral changes influenced back motion. Based on the results of radiographic analysis of the lumbosacral junction, dogs were divided into 3 groups: 1=no radiographic changes; 2=shortened L7 vertebra; and 3=transitional vertebrae, spondylosis, subluxations, and spondylarthrosis of the lumbosacral junction. ROM and TOO were compared using ANOVA for repeated measures and a Bonferroni's post hoc test; P<.05 was considered significant. Results— The highest transverse ROM was achieved by markers T6, T13, and L3, and in the vertical direction by S3; however, there were no significant differences in ROM in horizontal angulations. In the sagittal plane, T13–L3–L7 had a lower angulation than L3–L7–S3. In Group 3, transverse ROM for C7 was significantly higher than in Group 1; the horizontal angular maximum of T13–L3–L7 occurred significantly earlier. Conclusions— Significant kinematic changes were detected between clinically sound dogs with radiographic lumbosacral changes and dogs with no radiographic abnormalities. Clinical Relevance— Kinematic data from clinically sound dogs can be used for comparison with data from dogs with gait disturbances associated with orthopedic or neurologic disease or changes associated with therapy.     

The diagnosis and treatment of cauda equina lesions in the dog

The case details of 46 dogs with cauda equina syndrome are reviewed. The causes were variable and included lumbosacral spondylosis, disc protrusion, discospondylitis, fractures, dislocations and neoplasia. Dogs with discospondylitis generally responded well to prolonged antibiotic therapy but the response to conservative treatment of lumbosacral spondylosis or disc protrusion was transient or incomplete. Ten dogs with cauda equina syndrome were treated surgically; the techniques are described and results presented.     

Effect of hind limb position on the craniocaudal length of the lumbosacral space in anesthetized dogs

Objective To investigate whether rostral extension of the hind limbs increases the cranio‐caudal dorsal interlaminar distance between the seventh lumbar vertebra and the sacral bone (LS distance) in sternally recumbent anesthetized dogs. Study design Prospective clinical study. Animals Eighteen dogs (eight neutered males, three intact males, six spayed females, one intact female) of various breeds, weighing 4–34 kg and ranging in age from 1 to 13 years. Methods Each dog was grouped by size: small (≤10 kg), medium (15–20 kg) or large (≥25 kg). Each dog was anesthetized and positioned in sternal recumbency. Computed tomography (CT) of the lumbosacral area was performed with the hind limbs resting on the stifle and the feet extended posteriorly, and then with the hind limbs extended rostrally. LS distance, craniocaudal dorsal interlaminar distance between sixth and seventh lumbar vertebra (L6–L7 distance), length of L7 vertebral body and lumbosacral angle (LS angle) were measured on a reconstructed mid‐sagittal CT image from the two hind limb positions. The measurements from the two hind limb positions for the whole dog population and by size were compared using Student’s T tests. Diagnostic interpretation of the CT images was performed. Results The length of L7 was taken as the reference value as it was not affected by hind limb position. LS distance, L6–L7 distance and LS angle were significantly higher when the hind limbs were extended rostrally in all three size groups. The CT images of ten dogs showed clinically undetected osteoarthrosis of the ileo‐ and lumbosacral area. Conclusions and clinical relevance Rostral extension of the hind limbs significantly increases LS and L6–L7 distance and LS angle even in dogs with clinically undetected osteoarthrosis of the ileo‐ and lumbosacral area, and may enhance the ease of lumbosacral epidural injection in sternally recumbent anesthetized dogs.     

Cauda equina compression syndrome (CECS): retrospective study of surgical treatment with partial dorsal laminectomy in 86 dogs with lumbosacral stenosis

We report our results of partial lumbosacral laminectomy for treatment of canine Cauda equina Compression Syndrome due to a lumbosacral stenosis. Opposite to conventional techniques of dorsal laminectomy, only widening of the Spatium interarcuale is performed. This is achieved by exstirpation of the Lig. flavum and partial dorsal laminectomy of the first sacral segment. The Proc. spinosi and integrity of facet joints are fully maintained by this technique. In 96.5% of 86 dogs treated with this method relief of dorsal pressure and permanent rapid regression of clinical symptoms was achieved. In two cases recurrence of clinical symptoms was observed during follow up and one case showed no improvement at all. In conclusion partial dorsal laminectomy is a minimal invasive technique for treatment of Cauda equina compression syndrome expressed by pain reaction accompanied by minor neurological deficits caused by lumbosacral stenosis. Maintained spinal stability allows short reconvalescence and the unrestricted use of dogs immediately post operation.