“Endoscopic-Assisted Lumbosacral Foraminotomy in the Dog.”

Wood et al.

Vet Surg 2004.

Methods—Using endoscopic assistance, unilateral L7-S1 foraminotomy was performed. Computed tomography of L7-S1 was performed preoperatively, immediately postoperatively, and at 12 weeks. Parasagittal foramen area (PFA) measurements were obtained at the entry, middle, and exit zones of the treated and control foramen for each period. Objective and subjective data were compared among dogs by time period and treatment status.

Results—Endoscopic-assisted foraminotomy resulted in a significant increase in the mean PFA of the entry and middle zones immediately postoperatively. The exit zone was not significantly larger at any time. The foramen remained significantly larger at 12 weeks only in the middle zone; however, some decrease in the surgically created foramen enlargement occurred at all 3 levels. The procedure was well tolerated but dogs did have transient, mild delay of functional return postoperatively.

Conclusions—Endoscopic-assisted foraminotomy in dogs can be performed for certain foraminal regions, allowing enhanced visibility of the spinal canal. The foramen can be surgically enlarged at the entry and middle zones using this technique; however, some reduction of the foraminal enlargement occurs by 12 weeks. The clinical implications of this reduction cannot be determined from this study.  The lateral lumbar spinal canal is divided into the entrance zone (lateral recess), middle zone, and exit zone. The entrance zone is the most cranial aspect of the lateral lumbar canal and is located beneath the caudal articular facet of the cranial vertebral body. The middle zone is the region of the canal located at the level of the pars interarticularis portion of the lamina and caudal to the pedicle. The exit zone is the area immediately surrounding the intervertebral foramen.

“Asymmetrical, Transitional, Lumbosacral Vertebral Segments in Six Dogs: A Characteristic Spinal Syndrome.”

Steffen et al.

JAAHA 2004.

Clinical findings in six dogs with asymmetrical, transitional, lumbosacral vertebral segments are reported. All dogs exhibited low back pain and varying degrees of asymmetrical cauda equina dysfunction. Results of myelography, epidurography, and magnetic resonance imaging (MRI) indicated a unilateral disk protrusion in all dogs. In the dogs with MRIs, focal degenerative alterations in the vertebral end plates and adjacent body of the vertebra were detected. All dogs were treated with a dorsal laminectomy or hemilaminectomy. Results following surgery were good or excellent in all six dogs.  The disk protrusion always occurred on the opposite side from the broadest fusion of the vertebra with the ilium.  Although not statistically proven in the present report, dogs with asymmetrical, transitional, lumbosacral vertebral segments developed clinical signs earlier than dogs with degenerative lumbosacral stenosis

“Magnetic resonance imaging of articular process joint geometery and intervertebral disc degeneration in the caudal lumbar spine (L5-S1) of dogs with clinical signs of cauda equine compression. 

Rossi et al.

VRU 2004.

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. A significant association was found between tropism in the transverse plane and MR-imaging stage with higher mean tropism values recorded for the stage 4 disc spaces. Measured mean tropism values were 1.51, 2.41, 31, and 3.31 for MR-imaging stages 1, 2, 3, and 4, respectively. German Shepherd dogs had smaller articular process joint angles at all levels, but the angle values were similar for the L5–L6 and L6–L7 joints (121 and 14.41), whereas between L6–L7 and L7–S1 a large difference was observed (from 14.41 to 34.71). In the second group of dogs, the mean transverse angles were larger at all levels and increased more gradually in the caudal direction (20.61, 22.41, 37.91, respectively). These observations are in agreement with the results of a previous CT investigation,12 confirming the hypothesis of a different anatomic conformation of the lumbosacral region in German Shepherd dogs.

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

Benninger et al.

AJVR 2004.

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.

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

Steffen et al.

JAVMA 2008.

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.

“Force Plate Analysis Before and After Dorsal Decompression for Treatment of Degenerative Lumbosacral Stenosis in Dogs.”

Van Klaveren et al.

Vet Surg 2005.

Methods–DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy?), peak propulsive (Fy_), and peak vertical (Fz?) forces of 8 consecutive strides were determined. The ratio between the total Fy_ of the pelvic limbs and the total Fy_ of the thoracic limbs (P/TFy_), reflecting the distribution of Fy_, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control).

Results–In dogs with DLS, the propulsive forces (Fy_) of the pelvic limbs were significantly smaller than those of controls. P/TFy_ was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery.

Conclusions–Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period.

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

Benniger et al.

AJVR 2006.

Results: The amount of flexion and extension was found to increase with the following 4 parameters: large facet joint angle in the transverse plane, large difference in facet joint angles between levels in the transverse plane, high intervertebral disk height, and short lever arm length. Four shapes of facet joints were observed on transverse CT scans as follows: straight (28%), angled (14%), arcuate (29%), and round (14%; Figure 4). A few facet joints had different shapes on each side (15%). In GSDs, 47% of the facet joints were straight, 19% angled, 6% round, and 11% arcuate, whereas in dogs of other breeds, 16% were straight, 11% angled, 20% round, and 39% arcuate. In GSDs, 42% of the facet joints were asymmetric, whereas only 31% were asymmetric in dogs of other breeds. The difference in the facet joint angle in the transverse plane between adjacent motion segments was significantly (P < 0.001) larger from L6-7 to L7-S1 than between the more cranial segments. In GSDs, the difference in the facet joint angle from L6-7 to L7-S1 was significantly (P = 0.001) larger (21.9o) than in dogs of other breeds (15.8o).

“A lumbosacral transitional vertebra in the dog predisposes to cauda equine syndrome.” 

Fluckiger et al.

Vet Radiol and Ultrasound 2006.

The association between the occurrence of a lumbosacral transitional vertebra (LTV) and the cauda equina syndrome (CES) in dogs was investigated. In 4000 control dogs without signs of CES, 3.5% had an LTV, while in 92 dogs with CES, 16.3% had an LTV. The lesion causing CES always occurred between the last true lumbar vertebra and the LTV. Dogs with an LTV were eight times more likely to develop CES than dogs without an LTV. German Shepherd dogs were eight times more likely to develop CES compared with other breeds. Male dogs were twice as likely to develop CES than females. Dogs with an LTV develop CES 1–2 years earlier than dogs without an LTV.

“Lumbosacral transitional vertebrae in dogs: classification, prevalence, and association with sacroiliac morphology.” 

Damur-Djuric et al.

Vet Radiol and Ultrasound 2006.

The prevalence of lumbosacral transitional vertebrae (LTV) was determined by reviewing the pelvic radiographs of 4000 medium- and large-breed dogs of 144 breeds routinely screened for canine hip dysplasia. An LTV was seen in 138 (3.5%) dogs. The prevalence was higher in German Shepherd dogs and Greater Swiss Mountain dogs than in the other breeds, suggesting a genetic predisposition. There was no gender predisposition. The transverse processes of the LTV were divided into three types based on their morphological characteristics: lumbar type or type 1; intermediate type or type 2; and sacral type or type 3. In a symmetric LTV, both transverse processes are of the same type, while in an asymmetric LTV they are not. The frequency of occurrence of symmetric and asymmetric LTV was similar. In symmetric LTV, intermediate-type transverse processes predominated. Most of the asymmetric LTV had an intermediate-type transverse process combined with a lumbar or sacral type, respectively. Highly asymmetric LTV were often angled relative to the adjacent vertebrae. We hypothesize that an LTV is not the result of transformation of a lumbar into a sacral vertebra or vice versa, but rather is an autonomous intermediate type of vertebra. It occurs when the point of contact of the pelvis with the vertebral column is slightly cranial or caudal to its normal position. The resulting formative stimulus on the vertebral ossification centers, sagittally still separated, causes the various morphologies seen in LTV including the asymmetric variations. The first and second sacral vertebrae have an additional pair of symmetric ossification centers, which develop into the ventral parts of the wings of the sacrum. The dorsal portions of the sacral wings correspond to the transverse processes, which develop from the paired ossification centers out of the neural arches An LTV is asymmetric when the transverse processes have a different morphology. Variations in the shape of the vertebral body are less common. One or both ventral centers for the sacral wings may be absent or partially or completely developed. When absent, lumbar-type transverse processes develop, whereas with a partially or completely developed ventral ossification center, an intermediate or sacral-like transverse process forms. The prevalence of LTV varied from 0% to 9.4% between breeds with 50 or more dogs per breed (Table 2). It was significantly lower in Golden retrievers and Labrador retrievers and significantly higher in German Shepherd dogs and Greater SwissMountain dogs on comparing each of these breeds with all others combined (all Po0.01). In the Shar-Pei, prevalence reached 19.2%, but the number of examined dogs was only 26. The lengths of the sacroiliac attachments were the same on each side in 82% of the dogs with a symmetric LTV. When an asymmetric LTV was noted, these lengths were equal on both sides in 50% of the dogs. Of the symmetric LTV, only 15% were rotated while 49% of the asymmetric ones were rotated, and 85% of these were rotated toward the side where the contact zone between transverse process and the pelvis was longer as seen in types 2 and 3 transverse processes

“Biomechanical Flexion–Extension Forces in Normal Canine Lumbosacral Cadaver Specimens Before and After Dorsal Laminectomy–Discectomy and Pedicle Screw–Rod Fixation.”

Meu et al.

Vet Surg 2007.

Animals—Cadaveric spine specimens without lumbosacral pathology from mature, intact Labrador retrievers (n1/412).

Methods—Lumbosacral spine segments were subjected to a constant bending moment from L6 to S1 in a hydraulic 4-point bending materials testing machine. Force and displacement were recorded during each loading cycle constituting 1 complete flexion–extension cycle of the spine. Each spine segment had 3 series of recordings of 5 loading cycles each: (1) intact spine, (2) after surgical destabilization by dorsal laminectomy and partial discectomy, and (3) after surgical stabilization using dorsal pedicle screw–rod fixation.

Results—After dorsal laminectomy and partial discectomy, the neutral zone and range of motion were not different from those in the native spine specimen. After pedicle screw–rod fixation, the neutral zone and range of motion of the instrumented specimen significantly (Po.0001) decreased compared with the native specimen and the specimen after dorsal laminectomy.

Conclusion—Dorsal laminectomy and partial discectomy does not lead to significant spinal instability in flexion and extension whereas pedicle screw and rod fixation effectively stabilizes the lumbosacral spine.

Clinical Relevance—Dorsal laminectomy and partial discectomy does not lead to significant spinal instability. Pedicle screw–rod fixation of L7 and S1 may be used to stabilize an unstable L7–S1 junction in dogs with degenerative lumbosacral stenosis.

“Transiliac Approach for Exposure of Lumbosacral Intervertebral Disk and Foramen: Technique Description.”

Carozzo et al.

Vet Surg 2008.

Objective—To describe and evaluate a transiliac approach to the L7–S1 disk and intervertebral foramen in dogs.

Study Design—Cadaver study.

Animals—Fresh canine cadavers (n1/410).

Methods—A craniolateral approach was made to each iliac wing of 10 fresh canine mixed breed cadavers. An 18mm hole was drilled in a standardized position through the iliac wing. The musculature connected to the cranial aspects of the sacral wing was dissected and retracted cranially through this iliac window. Endoscopic exploration of the area was performed.

Results—The foramen and intervertebral disk were clearly observed in all specimens without iatrogenic injury of the L7 nerve branch. Access to the foramen was possible in 16 of 20 specimens without excision of the sacral wing; however, it was always partially excised to observe the intervertebral disk which lies more caudally and ventrally.

Conclusion—Transiliac approach to the lumbosacral joint allows direct exposure of the intervertebral disk and foramen through an iliac window. Endoscopic exploration provided good observation of the intervertebral disk and/or foramen.

Clinical Relevance—Transiliac approach could be used for lateral corpectomy and foraminotomy in dogs with degenerative lumbosacral stenosis caused by ventral or ventrolateral disk protrusion, foramen stenosis, or OCD of the L7–S1 joint. Clinical study will be necessary to evaluate the efficacy of this approach.

“Effects of body position and clinical signs on L7-S1 intervertebral foraminal area and lumbosacral angle in dogs with lumbosacral disease as measured via computed tomography.”

Jones et al.

AJVR 2008.

Objective—To measure effects of dog position on L7-S1 intervertebral foraminal area and lumbosacral (LS) angle by means of computed tomography (CT) and determine whether changes in values between positions are associated with clinical signs in dogs with LS disease.

Animals—86 dogs examined via a positional CT protocol that included flexion and extension scans of L7-S1.

Procedures—Archived CT images and medical records were reviewed. Included dogs had good-quality flexion and extension CT scans of L7-S1 and no evidence of fractures, neoplasia, or previous LS surgery. One person who was unaware of CT findings recorded clinical status with regard to 3 signs of LS disease (right or left hind limb lameness and LS pain) at the time of CT evaluation. One person who was unaware of clinical findings measured L7-S1 foraminal areas and LS angles, with the aid of an image-analysis workstation and reformatted parasagittal planar CT images.

Results—Intraobserver variation for measurements of L7-S1 foraminal area ranged from 6.4% to 6.6%. Mean foraminal area and LS angle were significantly smaller when vertebral columns were extended versus flexed. Percentage positional change in L7-S1 foraminal area or LS angle was not significantly different among dogs with versus without each clinical sign. There was a significant correlation between percentage positional change in L7-S1 foraminal area and LS angle in dogs with versus without ipsilateral hind limb lameness and LS pain.

Conclusions and Clinical Relevance—Positional CT is a feasible technique for quantifying dynamic changes in L7-S1 intervertebral foraminal morphology in dogs with LS disease.