Endoscopic-Assisted Lumbosacral Foraminotomy in the Dog

Morphometric Evaluation of Thoracolumbar Spinal Canal and Cord by Magnetic Resonance Imaging in Normal Small-Breed Dogs

Thoracolumbar intervertebral disc disease (IVDD) is the most common cause of spinal injury in dogs. MRI has been considered the gold standard for neurologic diagnosis, but studies focusing on the thoracolumbar spinal canal and spinal cord using MRI in small-breed dogs are limited. Therefore, this study aimed to establish an MRI reference range for the spinal cord and canal measurements (height, width, cord-to-canal ratio of height, width, cross-sectional area (CSA)) of each intervertebral disc level from T11 to L5 (total of seven levels) on transverse T2-weighted images in normal small-breed dogs. We hypothesized that the spinal cord and spinal canal measurements might vary according to the body weight and age. The width and height of the spinal cord and canal increased as the body weight increased at all levels (p < 0.05). The cord-to-canal ratio of the width showed a negative correlation to the body weight at all levels. The cord-to-canal ratio of the height did not show any correlation to the body weight at all levels. All measurements (height, width, cord-to-canal ratio of height, width, CSA) did not show any statistical correlation between the groups subdivided by age. These measurements could serve as a morphometric baseline for thoracolumbar spinal diseases and clinical research in small-breed dogs.

Percutaneous full endoscopic foraminotomy for treatment of cervical spinal nerve compression in horses using a uniportal approach: Feasibility study

BACKGROUND

Cervical spinal nerve insult can be a sequel of osteoarthropathy in horses due to enlargement of the articular processes (AP).

OBJECTIVES

To describe the percutaneous endoscopic cervical foraminotomy procedure in horses.

STUDY DESIGN

Ex vivo experimental study and clinical case report.

METHODS

The technique was performed in three equine cadavers and in two clinical cases with history of forelimb lameness located in the caudal cervical region. Briefly, the horse was positioned in lateral recumbency, with the affected AP joint uppermost. Under fluoroscopic guidance, the endoscopic instruments (Ø 6.9 mm, length 207 mm, 25° angle of vision) were positioned at the dorsal bony margin of the intervertebral foramen (IVF). The bone was freed from soft tissues and removed using diamond various burrs, hence widening the IVF. The bone drilling was continued until the medial cortical surface of the caudal AP was removed. Thereafter, the endoscope was removed and the skin portal was closed.

RESULTS

The average of operation time in clinical cases was 98 ± 24 min. The horses recovered smoothly from the operation. At 12-month follow-up, the clinical signs had resolved completely without recurrence.

MAIN LIMITATION

Small number of clinical cases and absence of post-mortem examination or histopathology performed in the cadaver study to assess possible iatrogenic injuries.

CONCLUSION

Cervical spinal nerve decompression via minimal invasive foraminotomy is feasible in horses. More research is required before this procedure can be recommended in clinical cases.

ACVIM consensus statement on diagnosis and management of acute canine thoracolumbar intervertebral disc extrusion

Background

Thoracolumbar intervertebral disc extrusion (TL‐IVDE) is the most common cause of acute paraparesis and paraplegia in dogs; however, guidelines on management of the condition are lacking.

Objectives

To summarize the current literature as it relates to diagnosis and management of acute TL‐IVDE in dogs, and to formulate clinically relevant evidence‐based recommendations.

Animals

None.

Methods

A panel of 8 experts was convened to assess and summarize evidence from the peer‐reviewed literature in order to develop consensus clinical recommendations. Level of evidence available to support each recommendation was assessed and reported.

Results

The majority of available literature described observational studies. Most recommendations made by the panel were supported by a low or moderate level of evidence, and several areas of high need for further study were identified. These include better understanding of the ideal timing for surgical decompression, expected surgical vs medical outcomes for more mildly affected dogs, impact of durotomy on locomotor outcome and development of progressive myelomalacia, and refining of postoperative care, and genetic and preventative care studies.

Conclusions and Clinical Importance

Future efforts should build on current recommendations by conducting prospective studies and randomized controlled trials, where possible, to address identified gaps in knowledge and to develop cost effectiveness and number needed to treat studies supporting various aspects of diagnosis and treatment of TL‐IVDE.

Minimally invasive mini-hemilaminectomy-corpectomy in cadaveric dogs: evaluation of the accuracy and safety of a three-dimensionally printed patient-specific surgical guide

Background

As the frequency of spine surgery increases in the veterinary field, many studies have been conducted on minimally invasive spine surgery (MISS). Although many studies have been conducted on the thoracolumbar spine about MISS in animals, several problems and limitations have emerged regarding this method. Therefore, we developed a three-dimensional (3D) printed patient-specific surgical guide (3DPSSG) using 3D printing technology to overcome these problems. We aimed to evaluate the accuracy and safety of the 3DPSSG in minimally invasive mini-hemilaminectomy-corpectomy (MI-MHC).

MI-MHC using 3DPSSG and an endoscopic system was performed at L1–L2 in 15 cadaveric dogs. The procedure of fixing the surgical guide to the vertebral body through screws and the surgical procedure using the guide were performed by two surgeons with different experiences. Postoperative computed tomography was used to measure planned and postoperative screw trajectories (angle, protruding from the far cortex) and to create 3D rendering images of vertebrae to evaluate the direction of bone window formation, corpectomy slot length, depth, and height ratio.

Results

The two groups which performed by two surgeons with different experiences did not differ in terms of screw angle deviation and length of the screw protruded from the far cortex. The corpectomy slot-length ratio was not different between the two groups; however, the slot-depth and height ratios were different.

Conclusions

No differences were detected in screw trajectory and corpectomy slot-length ratio between the two groups. The 3DPSSG for MI-MHC is classified as accurate and safe; therefore, it can be an alternative to the conventional technique in dogs.

Microendoscopic Dorsal Laminectomy for Multi-Level Cervical Intervertebral Disc Protrusions in Dogs

The objective of this study was to evaluate the feasibility and clinical outcomes of microendoscopic dorsal laminectomy for multi-level cervical intervertebral disc protrusions in dogs. Eight client-owned dogs diagnosed with multi-level cervical intervertebral disc protrusions using computed tomography (CT) and magnetic resonance imaging (MRI) were included in this retrospective case series. Microendoscopic dorsal laminectomies (MEL) were performed with an integrated endoscopic system to the cranial and caudal vertebrae of the affected intervertebral joints. Pre- and post-operative neurological status, operation time, intra-operative complications, and postoperative complications were reviewed. Post-operative CT images were obtained to measure the dimensions of laminectomy and compared to those of planned laminectomy. Full endoscopic procedures were feasible in 7 dogs (87.5%) and the laminectomy dimensions were in agreement with pre-operative planning. In all dogs, major intra- and postoperative complications did not occur. Conversion to open surgery was required in one case. Short-term postoperative clinical deterioration was found in two dogs. Long-term clinical outcomes were good and comparable to those reported in previous studies of open dorsal laminectomies. MEL is a promising minimally invasive approach to multi-level cervical dorsal laminectomy for intervertebral disc protrusions. This technique may improve postoperative discomfort compared to the open approach. Further studies are needed to directly compare outcomes between these two approaches.

Microendoscopic Mini-Hemilaminectomy and Discectomy in Acute Thoracolumbar Disc Extrusion Dogs: A Pilot Study

The objective of this study was to evaluate the clinical outcomes and complications of a microendoscopic laminectomy and discectomy (MED) for acute thoracolumbar intervertebral disc extrusions in dogs. Eleven client-owned dogs with acute thoracolumbar intervertebral disc extrusions were included in this retrospective case-series. Dogs were diagnosed with acute thoracolumbar intervertebral disc extrusions using computed tomography (CT) and magnetic resonance imaging (MRI). MED was performed with an integrated endoscopic system to the affected intervertebral disc. Surgery time, intra-operative complications, causes of conversion to microscopic surgery if necessary, post-operative complications, and neurological status on presentation at discharge, as well as any further evaluations in hospital, and long-term concerns via owner contact, were recorded. Post-operative CT images were obtained to compare the extent of laminectomy performed to the planned region of laminectomy. The fully endoscopic procedure was completed in eight dogs without major complications. Three cases were converted to an open surgery due to difficulty removing extruded disc material and controlling hemorrhage. The clinical outcome was good in all cases and equivalent to previously reported prognoses after open surgery. MED is an effective and safe alternative to conventional open procedures in dogs with acute thoracolumbar intervertebral disc extrusion.

Distraction Stabilization of Degenerative Lumbosacral Stenosis: Technique and Mid- to Long-Term Outcome in 30 Cases

OBJECTIVE

 To describe the dorsal laminectomy, annulectomy and distraction stabilization with pins and polymethylmethacrylate technique, its complications and outcome in the management of canine degenerative lumbosacral stenosis. To determine pre- and post-surgical foraminal width and vertebral step changes.

STUDY DESIGN

 Multi-institutional retrospective clinical study.

METHODS

 Medical records (2005-2020) of dogs treated (n = 30). Clinical signs, Modified Frankel Score, Texas Spinal Cord Injury Score, pain score (dorsal palpation of spine, tail dorsiflexion), imaging findings and complications were retrieved pre-operatively, perioperatively and at long-term follow-up.

RESULTS

 The most common presurgical imaging findings were disc protrusion (24/25) and sclerosis of the caudal end-plate of L7 (23/30). On short- to long-term assessment 18 out of 21 dogs exhibited clinical improvement and all exhibited improved pain scores (p < 0.0001). Catastrophic complications occurred in 3 dogs, and major complications occurred in 5, of which 3 required additional surgery. Mean lumbosacral step defect reduced 60% (1.8 mm ± 2.5 mm pre-surgery to 0.7mm ± 0.9mm post-surgery, p = 0.1585). Mean foraminal width significantly increased 50% long-term (3.3 mm ± 1.0 mm pre-surgery to 5.0 mm ± 0.9 mm post-surgery, p < 0.0001).

CLINICAL SIGNIFICANCE

 Dorsal laminectomy, annulectomy and distraction stabilization is a complex procedure which can significantly increase foraminal width, reduce pain and improve gait characteristics in dogs in the short- to long-term, and should be performed by surgeons experienced in lumbosacral pin placement.

Effects of intervertebral distraction screw fixation of the lumbosacral joint on the adjacent lumbar segments in Beagles

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.

Minimally invasive spine surgery in dogs: Evaluation of the safety and feasibility of a thoracolumbar approach to the spinal cord

OBJECTIVE

To describe the safety and feasibility of a minimally invasive spine surgery technique to access the thoracolumbar vertebral canal in dogs.

STUDY DESIGN

Prospective study.

ANIMALS

Six healthy research dogs.

METHODS

Dogs were placed under anesthesia for MRI to evaluate vertebral column and spinal cord integrity. Minimally invasive surgery was performed at multiple sites. Access to the vertebral canal was achieved by means of foraminotomy, discectomy, and lateral minicorpectomy by using minimally invasive access and a surgical microscope. Sequential neurological examinations, pressure algometry pain quantification, and creatine kinase levels were evaluated before and after surgery for 7 days. Magnetic resonance imaging, computed tomography, and histopathology were performed on day 6 postoperatively after animals were humanely killed to evaluate the impact of surgery on spinal cord, muscles, and bone.

RESULTS

The vertebral canal was successfully accessed, and the ventral aspect of the spinal cord was identified at all sites. No neurological deterioration was observed. Postoperative pain was not different compared with baseline except in one dog on the day after surgery.

CONCLUSION

Minimally invasive spine surgery was a safe and feasible technique to access the thoracolumbar vertebral canal and the ventral aspect of the spinal cord in dogs. Findings supported postoperative pain benefits.

CLINICAL SIGNIFICANCE

Minimally invasive spine surgery is a valid surgical technique to access the thoracolumbar vertebral canal at single or multiple sites in dogs.

Canine Degenerative Lumbosacral Stenosis: Prevalence, Impact And Management Strategies

Canine degenerative lumbosacral stenosis (DLSS) is a syndrome of low back pain with or without neurologic dysfunction associated with compression of the cauda equina. Most commonly occurring in medium- to large-breed dogs of middle to older age, German shepherd and working dogs are predisposed. Diagnosis is based on a combination of clinical signs, advanced imaging and ruling out other differential diagnoses. The volume of the intervertebral foramina at the lumbosacral junction is naturally reduced on extension but degenerative changes lead to a more marked reduction that can impinge the L7 nerve roots. Evidence is lacking on which to base decision-making for treatment of dogs with DLSS. However, surgical intervention may be indicated in dogs that do not respond to conservative management, or for dogs in which there is a requirement to work that prevents lifestyle adjustments. Improvements in electrodiagnosis and novel intra-discal treatments may improve the management of DLSS in the future.

Minimally invasive microsurgical decompression of an intervertebral disc protrusion in a dog

OBJECTIVE

To report the successful treatment of intervertebral disc protrusion with minimally invasive microsurgery in a large breed dog.

STUDY DESIGN

Retrospective case report.

ANIMAL

A 4-year-old, neutered male, German shepherd dog presented with chronic progressive ambulatory paraparesis and thoracolumbar pain; lumbar intervertebral disc protrusion and severe spinal cord compression at L2-L3 were diagnosed.

METHODS

A minimally invasive approach was used to access the target surgical area by using a muscle splitting technique and retractors. Intraoperative fluoroscopy confirmed correct placement. Magnification and illumination through a surgical microscope were used (microsurgery) to perform the spinal cord decompression by means of a foraminotomy and lateral corpectomy.

RESULTS

Technically, the combination of fluoroscopy and muscle splitting approach offered adequate minimally invasive access. Microsurgery allowed for precise and efficient spinal cord decompression. Clinically, no immediate postoperative neurological deterioration was observed. Opioid usage was limited to 24 hours postoperatively. Focal muscle swelling was observed postoperatively for 2 days, and hospital stay was 3 days. At 7 weeks postoperatively, neurological examination results were normal, and postoperative MRI confirmed spinal cord decompression. No complications were reported.

CONCLUSION

The procedure was associated with a small incision, limited muscle trauma, early improvement of the neurological status, a short hospital stay, and limited postoperative pain.

CLINICAL SIGNIFICANCE

This case provides evidence that minimally invasive microsurgery is an effective treatment for intervertebral disc protrusion in large breed dogs and may offer benefits regarding postoperative pain and functional recovery.

Long-term outcome following lateral foraminotomy as treatment for canine degenerative lumbosacral stenosis

Lateral foraminotomy has been described as an effective surgical treatment for foraminal stenosis in the treatment of degenerative lumbosacral stenosis (DLSS) in dogs. Clinical records were reviewed from 45 dogs which had undergone lateral foraminotomy at the lumbosacral junction either alone or in combination with decompressive midline dorsal laminectomy. Short-term outcome at six weeks was assessed by the surgeon to be good (11.1 per cent) or excellent (88.9 per cent) in all 45 cases. Long-term outcome beyond six months for lumbosacral syndrome was assessed by the owner as excellent in all 34 cases for which follow-up was available despite recurrence in five cases. Recurrence of clinical signs was not related to re-establishment of foraminal compression at the surgical site when assessed on repeat MRI and was managed by either contralateral foraminotomy in one case or conservative management with excellent response. This study confirms lateral foraminotomy as an effective procedure in the management of DLSS-affected dogs suffering from foraminal stenosis and demonstrates that initial good short-term results are maintained long term despite some treatable recurrences. Lateral foraminotomy is an effective procedure when used appropriately in DLSS with foraminal stenosis either alone or in combination with midline dorsal laminectomy.

Lumbosacral foraminal ratios and areas using MRI in medium-sized dogs

Objective: To examine conventional magnetic resonance imaging planes of the lumbosacral foramina to obtain objective measurements of foraminal size in mediumsized (20–28 kg) normal dogs.

Method: Ten canine cadavers were evaluated using magnetic resonance imaging in neutral, flexed and extended position. Foraminal ratios, areas and lumbosacral angles were calculated and their relationship to body weight was evaluated.

Results: Foraminal ratios were found to be independent of body weight in medium sized dogs (p >0.42). Foraminal areas were dependent on body weight (p <0.05). Flexion and extension were shown to significantly change both the foraminal ratio and area.

Clinical significance: Lumbosacral foraminal stenosis is common in working dogs. Foraminal ratios were evaluated in mediumsized dogs and were found to be independent of body weight, which may provide objective evaluation of surgical decompression techniques if calculated pre- and post-surgery. Foraminal areas were not independent of body weight.

Minimally Invasive Spine Surgery in Small Animals

Minimally invasive spine surgery (MISS) seems to have many benefits for human patients and is currently used for various minor and major spine procedures. For MISS, a change in access strategy to the target location is necessary and it requires intraoperative imaging, special instrumentation, and magnification. Few veterinary studies have evaluated MISS for canine patients for spinal decompression procedures. This article discusses the general requirements for MISS and how these can be applied to veterinary spinal surgery. The current veterinary MISS literature is reviewed and suggestions are made on how to apply MISS to different spinal locations.

Operative techniques of percutaneous endoscopic mini-hemilaminectomy using a uniportal approach in dogs

The present study aimed to investigate the technical feasibility of percutaneous endoscopic mini-hemilaminectomy via a uniportal approach, and to evaluate the possibility of decompression and endoscopic examination of the thoracic and lumbar spinal canals in small dogs during such procedures. Fresh canine cadavers of mixed-breed dogs (n=7) were used in this study. Following injection of a barium and agarose mixture (BA-gel) to stimulate intervertebral disc herniation, percutaneous endoscopic mini-hemilaminectomy was performed using a lateral approach to the thoracic and lumbar vertebrae. BA-gel was removed to decompress the spinal cord using an elevator and rongeurs after mini-hemilaminectomy. Pre and post-operative computed tomography (CT) scans were obtained to evaluate surgical outcomes. Intra-operative complications, incision length, and procedure time were recorded. All procedures were completed with clear visualization of the spinal cord and floor of the spinal canal. The mean total operating time was 58.00 ± 18.06 min. Lengths of incision were under 1 cm in all dogs. Intra-operative complications included iatrogenic nerve root injuries caused by the micro-rongeur in two dogs. CT imaging revealed that removal of BA-gel resulted in sufficient spinal cord decompression. Our findings indicated that percutaneous endoscopic thoracolumbar mini-hemilaminectomy is feasible for spinal cord decompression and allows for adequate observation of the spinal canal. Thus, this technique may be an alternative surgical option for treatment of thoracolumbar disk disease in dogs.

Complete Cranial Iliac Osteotomy to Approach the Lumbosacral Foramen

An approach using a complete cranial iliac osteotomy (CCIO) to access the lumbosacral (LS) foramen in dogs from lateral was developed using cadavers and applied in a clinical patient with degenerative lumbosacral stenosis (DLSS). The foraminal enlargement in the cadavers and the patient was documented on postoperative CT scans. The preoperative CT scan of the patient showed moderate cranial telescoping of the sacral roof and a moderate central disk protrusion, leading to moderate to severe compression of the cauda equina. In addition, there was lateral spondylosis with consequential stenosis of the right LS foramen. The right L7 nerve had lost its fat attenuation and appeared thickened. After a routine L7S1 dorsal laminectomy with a partial discectomy, a CCIO was performed, providing good access to the LS foramen and the adhesions around the proximal L7 nerve caudoventral to the foramen. The osteotomy was stabilized with a locking plate and a cerclage wire. The dog recovered well from the procedures and after 36 h, the dog walked normally and was discharged from the hospital. Eight and 16 weeks later, the signs of the DLSS had markedly improved. From these data, it can be concluded that the CCIO is a useful approach to the LS foramen and intervertebral disk in selected patients with DLSS, giving good access to the structures around the LS foramen.

Postoperative computed tomography and low-field magnetic resonance imaging findings in dogs with degenerative lumbosacral stenosis treated by dorsal laminectomy

OBJECTIVES

To describe postoperative computed tomography (CT) and magnetic resonance imaging (MRI) findings in dogs with degenerative lumbosacral stenosis (DLSS) treated by dorsal laminectomy and partial discectomy.

METHODS

Prospective clinical case study of dogs diagnosed with and treated for DLSS. Surgical and clinical findings were described. Computed tomography and low field MRI findings pre- and postoperatively were described and graded. Clinical, CT and MRI examinations were performed four to 18 months after surgery.

RESULTS

Eleven of 13 dogs were clinically improved and two dogs had unchanged clinical status postoperatively despite imaging signs of neural compression. Vacuum phenomenon, spondylosis, sclerosis of the seventh lumbar (L7) and first sacral (S1) vertebrae endplates and lumbosacral intervertebral joint osteoarthritis became more frequent in postoperative CT images. Postoperative MRI showed mild disc extrusions in five cases, and in all cases contrast enhancing non-discal tissue was present. All cases showed contrast enhancement of the L7 spinal nerves both pre- and postoperatively and seven had contrast enhancement of the lumbosacral intervertebral joints and paraspinal tissue postoperatively. Articular process fractures or fissures were noted in four dogs.

CLINICAL SIGNIFICANCE

The study indicates that imaging signs of neural compression are common after DLSS surgery, even in dogs that have clinical improvement. Contrast enhancement of spinal nerves and soft tissues around the region of disc herniation is common both pre- and postoperatively and thus are unreliable criteria for identifying complications of the DLSS surgery.

Video-assisted removal of metal pellet fragments from the vertebral canal following gunshot injury and long-term outcome in a cat

OBJECTIVE

 To describe the surgical management and long-term outcome of a spinal gunshot injury in a cat.

CLINICAL REPORT

A two-year-old, 4.2 kg castrated European Shorthair male cat was referred for evaluation of bilateral acute hindlimb paralysis with loss of deep pain perception in the right hindlimb associated with a perforating gunshot wound in the left side of the flank. Based on the clinical findings, the injury was localized to the fourth lumbar-first sacral spinal cord segment. The orthogonal spinal radiographs and computed tomography examination showed several metal pellet fragments within the vertebral canal of the sixth lumbar vertebra. A left mini-hemilaminectomy of the sixth lumbar vertebra pedicle combined with a mini dorsal laminectomy over the sixth to seventh lumbar vertebrae disc space were performed. A 2.4 mm 30° arthroscope was then introduced within the spinal canal to improve visibility and help with the fragment extraction. The cat was discharged from the hospital five days after surgery and the owners were encouraged to continue passive and active physiotherapy movements.

RESULTS

The cat was ambulatory with a plantigrade stance eight weeks following surgery. At the last follow-up examination (24 months postoperatively), the cat was able to jump on chairs, although intermittent urinary and faecal incontinence, proprioceptive deficits, and plantigrade stance were still present.

CLINICAL SIGNIFICANCE

 Decompressive surgery may promote neurological status improvement following spinal gunshot injury.

Management of degenerative lumbosacral disease in cats by dorsal laminectomy and lumbosacral stabilization

In this case series we describe the diagnosis and surgical treatment of five cats affected by clinical cauda equina syndrome as a result of degenerative lumbosacral stenosis. Radiographic and magnetic resonance imaging findings confirmed the suspected diagnosis of disc-associated lumbosacral disease. Cauda equina decompression was achieved by dorsal laminectomy followed by dorsal annulectomy and nuclear extirpation. Dorsal stabilization was achieved using miniature positive-profile pins inserted into the vertebral body of L7 and the wings of S1 with the free ends of the pins being embedded in a bolus of gentamicin-impregnated polymethylmethacrylate. Reassessment two years postoperatively using a previously validated feline specific owner questionnaire indicated satisfactory outcome with complete return to normal activity and resolution of signs of pain in all cases.

Effects of body position, imaging plane, and observer on computed tomographic measurements of the lumbosacral intervertebral foraminal area in dogs

OBJECTIVE

To evaluate effects of imaging plane, flexion and extension, patient weight, and observer on computed tomographic (CT) image measurements of the area of the lumbosacral (L7-S1) intervertebral foramen (LSIF) in dogs.

SAMPLE

12 dog cadavers (2 were excluded because of foraminal stenosis).

PROCEDURES

In each cadaver, sagittal, sagittal oblique, transverse oblique, and double oblique CT images were obtained at 3 zones (entrance, middle, and exit zones) of the region of the lateral lumbar spinal canal that comprises the LSIF while the lumbosacral junction (LSJ) was positioned in flexion or extension. Barium-impregnated polymethylmethacrylate was used to fill the intervertebral foramina to aid boundary detection. Measurements of interest were obtained.

RESULTS

Among the dog cadavers, there was large variability in LSIF cross-sectional areas (range, 0.12 to 0.44 cm2; SD, 0.1 cm2) and in foraminal angles required to obtain a double oblique plane in LSJ extension (SD, 8 ° to 9 °). For LSIF area measurements in standard sagittal CT images, interobserver variability was 23% to 44% and intraobserver variability was 4% to 5%. Sagittal oblique images obtained during LSJ extension yielded smaller mean LSIF areas (0.30 cm2), compared with findings in sagittal images (0.37 to 0.52 cm2). The exit and middle zone areas were smaller than the entrance zone area in sagittal images obtained during LSJ extension.

CONCLUSIONS AND CLINICAL RELEVANCE

Repeated measurements of the LSIF area in images obtained during LSJ extension may be unreliable as a result of interobserver variability and the effects of dog positioning and CT slice orientation.

A Review of Neuroendoscopy and Potential Applications in Veterinary Medicine

The endoscope was first developed over 200 yr ago. Endoscopy has since been applied to many disciplines of medicine. Its application to the nervous system was initially slow and not widely accepted and mainly involved the biopsy of tumors and the treatment of hydrocephalus. Several reasons for neuroendoscopy's limited use include inadequate endoscope technology, high skill level required, the advent of the surgical microscope, and the development of other treatments such as ventricular shunting. Over the past 50 yr, improvements in optical glass lenses, fiber optics, and electrical circuitry has led to better equipment and a revival of neuroendoscopy. Neuroendoscopy is now used in many diseases in human medicine including hydrocephalus, neoplasia, and intracranial cysts. This review presents the history of neuroendoscopy, the equipment and technology used, and the possible translation of techniques currently used in human medicine to veterinary medicine.

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.