Surgical treatment of lumbosacral instability caused by discospondylitis in four dogs

Accuracy and Safety of Image-Guided Freehand Pin Placement in Canine Cadaveric Vertebrae

OBJECTIVE

 The aim of this study was to validate an imaging technique for evaluation of spinal surgery accuracy and to establish accuracy and safety of freehand technique in the thoracolumbar spine of large breed dogs.

STUDY DESIGN

 After thoracolumbar spine computed tomography (CT), 26 drilling corridors were planned then drilled to receive 3.2 mm positive profile pins using a freehand technique. After pin removal, CT was repeated. All entry points, exit points and angles of the preoperative planned trajectories were compared with postoperative ones using an image registration and fusion technique by three observers. Corridor coordinates for entry and exit points were evaluated in three dimensions and angles were measured in one plane. Intraclass correlation coefficient (ICC) was used to establish the imaging technique reliability and descriptive statistics were used to report on the freehand technique accuracy. Safety was evaluated using a vertebral cortical breach grading scheme.

RESULTS

 Intraclass correlation coefficient for the entry points, exit points and angle were 0.79, 0.96 and 0.92 respectively. Mean deviations for the entry points, exit points and angle were 3.1 mm, 6.3 mm and 7.6 degrees respectively. Maximum deviations were 6.3 mm, 11.0 mm and 16.4 degrees. Most deviations were lateral and caudal. All corridors were judged as safe.

CONCLUSION

 The imaging technique reliability was good to excellent to study spinal surgery accuracy. Implant deviations should be anticipated when planning stabilization surgery in large breed dogs using the freehand-guided technique.

Use of C-reactive protein concentration in evaluation of diskospondylitis in dogs

Background

C‐reactive protein (CRP) is a positive acute phase protein that increases in many inflammatory conditions of dogs. Serum CRP concentration has important diagnostic and prognostic utility in humans with vertebral osteomyelitis.

Hypothesis/objectives

To determine if a correlation exists between serum CRP concentration and clinical and magnetic resonance imaging (MRI) findings in dogs with diskospondylitis, and if CRP predicts prognosis.

Animals

Eighteen client‐owned dogs with MRI diagnosis of diskospondylitis.

Methods

Retrospective study evaluating signalment, clinical signs, neurologic examination findings, white blood cell count, neutrophil count, serum globulin concentration, serum CRP concentration, radiographic findings, MRI findings, bacterial culture results, and outcome in dogs with diskospondylitis.

Results

Serum CRP concentration was significantly more sensitive than were fever and leukocytosis for predicting the presence of diskospondylitis. Serum CRP concentration was more sensitive than neutrophilia and hyperglobulinemia. No difference in serum CRP concentration was found between dogs with single or multiple lesions, nor between dogs with or without empyema, muscular involvement or spinal cord compression. No association was found between serum CRP concentration and positive bacterial culture.

Conclusions and Clinical Importance

C‐reactive protein is a sensitive, but nonspecific biomarker for diskospondylitis which may prove useful as an adjunctive diagnostic test in patients with suspicious clinical signs and may help predict prognosis.

Accuracy of Placement of Pedicle Screws in the Lumbosacral Region of Dogs Using 3D-Printed Patient-Specific Drill Guides

OBJECTIVE

 The aim of this study was to report the accuracy of pedicle screw placement using three-dimensional (3D)-printed, patient-specific drill guides in the lumbosacral region of dogs.

STUDY DESIGN

 This was a retrospective study. Thirty-two pedicle screws were placed in five dogs. Medical records were reviewed between November 2015 and November 2018 for dogs showing clinical signs associated with cauda equina syndrome. Inclusion criteria included preoperative magnetic resonance imaging, pre- and postoperative computed tomography (CT) and dorsal stabilization, with pedicle screws placed using 3D-printed, patient-specific drill guides and polymethylmethacrylate. Screw placement was evaluated for medial or lateral breaching on postoperative CT.

RESULTS

 Five dogs met the inclusion criteria. Four had degenerative lumbosacral stenosis and one had discospondylitis. All dogs had failed medical management prior to surgery. Of 32 bicortical pedicle screws placed, 30 were fully contained inside the pedicle and 2 were partially breaching the vertebral canal (less than one-third of the screw diameter). Postoperative CT revealed good alignment of L7-S1 in all planes.

CONCLUSION

 This technique enabled an accurate and safe placement of pedicle screws in the lumbosacral region of dogs with lumbosacral disease. Three-dimensional, printed patient-specific drill guides are a safe and effective method of placing pedicle screws in dogs with lumbosacral disease.

Qualitative and quantitative computed tomographic characteristics of the lumbosacral spine in German Shepherd military working dogs with versus without lumbosacral pain

Lumbosacral (LS) stenosis is a cause of lower back pain, loss of mission readiness, and early retirement in military working dogs (MWDs). Aims of the present two-part study were to evaluate a sample of German Shepherd MWDs using standard clinical criteria for LS pain, standard qualitative computed tomographic (CT) criteria for LS stenosis, novel quantitative CT criteria for LS stenosis, and novel behavioral classification criteria for LS pain. Data were retrieved from archives of a tertiary referral MWD hospital. Study 1 was a retrospective, observational, two-group design with a hypothesis that there would be a significant difference in the percentage of affected German Shepherd MWDs with multilevel stenosis (affecting ≥ 3 vertebrae) between LS pain groups, based on standard clinical and qualitative CT criteria. Study 2 was a retrospective, observational, cross-sectional, two- and three-group study design with a hypothesis that quantitative CT measurements would significantly differ between LS pain groups, assigned based on 3 classification systems. The 1st classification system used standard clinical criteria, while the 2nd and 3rd novel classifications included behavioral signs of LS pain. The following quantitative CT measures were recorded without knowledge of behavioral classification: vertebral foramen area, vertebral foramen volume, vertebral foramen fat area; and ratios of vertebral foramen area/vertebral body area (foramen area ratio), cranial vertebral foramen area/caudal vertebral foramen area (cranial:caudal foramen area ratio), and vertebral fat area/vertebral body area (fat area ratio). Study 1 findings did not support the hypothesis in that there was no significant difference in the percentage of dogs affected with multilevel stenosis between LS pain groups (P = 0.6567). Findings for study 2 supported the hypothesis in that dogs with LS pain were significantly more affected by multilevel stenosis (P = 0.0273). Significant differences occurred between LS pain groups in select vertebral locations for all measurements (P ≤ 0.05) except vertebral foramen area and vertebral foramen volume (P > 0.05). Comparisons using novel quantitative CT measures and behavioral classification criteria identified significant differences between LS pain groups that were not detected using standard qualitative criteria. These novel quantitative and behavioral classification criteria may be helpful in future research on causes for early retirement in German Shepherd MWDs.

Diagnosis and management of lumbar Aspergillus spp. discospondylitis using intraoperative cytology and external stabilization in a dog with disseminated infection

Background:

Discospondylitis is an infection of the intervertebral disc and adjacent vertebral endplates. The infectious agent is most commonly a bacterial organism and fungal causes are uncommon.

Case Description:

A 1.5-year-old female entire pug was referred with a 6-week history of right head tilt and progressive non-ambulatory paraparesis. On neurological examination, right facial paralysis and mid and caudal lumbar pain were also detected. Magnetic resonance imaging and computed tomography of the head and spine were performed 3 weeks apart. Findings were consistent with osteolysis of the petrous temporal bone and L2-L3 and L5-L6 vertebral subluxation caused by discospondylitis and osteomyelitis. Disseminated aspergillosis was diagnosed following biopsy and stabilization using an external skeletal spinal fixator. Voriconazol was administered as a medical treatment after surgery. The dog died 3 months later without failure of the construct.

Conclusion:

To the authors’ knowledge, this is the first report using an external fixator for fungal lumbar discospondylitis. The use of an external skeletal spinal fixator should be considered when choosing the surgical technique.

Diagnostic Imaging of Discospondylitis

Discospondylitis can affect dogs of any age and breed and may be seen in cats. Although radiography remains the gold standard, advanced imaging, such as CT and MRI, has benefits and likely allows earlier diagnosis and identification of concurrent disease. Because discospondylitis may affect multiple disk spaces, imaging of the entire spine should be considered. There is a lengthening list of causative etiologic agents, and successful treatment hinges on correct identification. Image-guided biopsy should be considered in addition to blood and urine cultures and Brucella canis screening and as an alternative to surgical biopsy in some cases.

Biomechanical comparison between pins and polymethylmethacrylate and the SOP locking plate system to stabilize canine lumbosacral fracture-luxation in flexion and extension

OBJECTIVE

To determine the stability of a simulated complete L7-S1 fracture-luxation immobilized with SOP locking plate system, compared to pins and polymethylmethacrylate (PMMA).

STUDY DESIGN

In vitro biomechanical study.

ANIMALS

Cadaver specimens of 18 skeletally mature large-breed dogs.

MATERIALS AND METHODS

Specimens were randomly stabilized with one of the two fixation techniques. Lumbosacral spine specimens (L5-S3) were subjected to a bending moment applied to the caudal and cranial ends of the specimen. The biomechanical parameters (ie, range of motion [ROM], neutral zone [NZ], and elastic zone stiffness [EZS]) were compared between fixation techniques.

RESULTS

No difference was found between the means of the NZ in flexion (P = .3458), extension (P = .1255), and total value (P = .3458) of L7-S1 stabilized with the two fixation techniques. Mean ROM in flexion (P = .2386), extension (P = .1255), and mean of EZS in extension (P = .4094) did not differ between fixations. The only significant differences were in the means of total ROM and means of the EZS in flexion, with the means being smaller with SOP fixation.

CONCLUSION

The stability of the two fixation techniques in flexion and in extension was similar for the L7-S1 and adjacent L5-L6 junctions, while the mean of ROM of L6-L7 in flexion was smaller with SOP fixation.

CLINICAL RELEVANCE

Stability of the resulting construct should be considered when selecting an implant. Our results provide evidence that fixation via pin-PMMA or SOP provide similar stability for L7-S1 fracture-luxation. In this context, other factors become more important in selecting the fixation method.

Pedicle screw-rod fixation: a feasible treatment for dogs with severe degenerative lumbosacral stenosis

Background

Degenerative lumbosacral stenosis is a common problem in large breed dogs. For severe degenerative lumbosacral stenosis, conservative treatment is often not effective and surgical intervention remains as the last treatment option. The objective of this retrospective study was to assess the middle to long term outcome of treatment of severe degenerative lumbosacral stenosis with pedicle screw-rod fixation with or without evidence of radiological discospondylitis.

Results

Twelve client-owned dogs with severe degenerative lumbosacral stenosis underwent pedicle screw-rod fixation of the lumbosacral junction. During long term follow-up, dogs were monitored by clinical evaluation, diagnostic imaging, force plate analysis, and by using questionnaires to owners.

Clinical evaluation, force plate data, and responses to questionnaires completed by the owners showed resolution (n = 8) or improvement (n = 4) of clinical signs after pedicle screw-rod fixation in 12 dogs. There were no implant failures, however, no interbody vertebral bone fusion of the lumbosacral junction was observed in the follow-up period. Four dogs developed mild recurrent low back pain that could easily be controlled by pain medication and an altered exercise regime.

Conclusions

Pedicle screw-rod fixation offers a surgical treatment option for large breed dogs with severe degenerative lumbosacral stenosis with or without evidence of radiological discospondylitis in which no other treatment is available. Pedicle screw-rod fixation alone does not result in interbody vertebral bone fusion between L7 and S1.

Diagnosis and treatment of lumbosacral discospondylitis in a calf

Background

The aim of this case report was to describe the clinical findings, treatment and outcome of lumbosacral discospondylitis in a calf.

Case Presentation

A 5.5-month-old calf was presented with difficulty in rising, a stiff and slightly ataxic gait in the hind limbs and a shortened stride. The lumbosacral region was severely painful on palpation.

Radiographic examination confirmed lumbosacral discospondylitis. Medical treatment with stall rest was instituted over six weeks. Radiographic and ultrasonographic follow-up examinations showed lysis of the endplates initially, then collapse of the intervertebral space at the lumbosacral junction and progressive sclerosis in the periphery of the lytic zones. Four weeks after institution of treatment, the calf could rise normally and the general condition gradually had returned to normal. The calf was discharged after 6 weeks and was sound at 3.5 months clinical and radiographic follow up examination. Thereafter, it was kept on alpine pastures without problems and was pregnant 1 year after the last examination.

Conclusions

This report shows that recovery from lumbosacral discospondylitis is possible in heifers, provided that treatment is started before major neurologic deficits have developed and is continued for an extended period of time.

Accuracy of conventional radiography and computed tomography in predicting implant position in relation to the vertebral canal in dogs

OBJECTIVE

To compare the accuracy of radiography and computed tomography (CT) in predicting implant position in relation to the vertebral canal in the cervical and thoracolumbar vertebral column.

STUDY DESIGN

In vitro imaging and anatomic study.

ANIMALS

Medium-sized canine cadaver vertebral columns (n=12).

METHODS

Steinmann pins were inserted into cervical and thoracolumbar vertebrae based on established landmarks but without predetermination of vertebral canal violation. Radiographs and CT images were obtained and evaluated by 6 individuals. A random subset of pins was evaluated for ability to distinguish left from right pins on radiographs. The ability to correctly identify vertebral canal penetration for all pins was assessed both on radiographs and CT. Spines were then anatomically prepared and visual examination of pin penetration into the canal served as the gold standard.

RESULTS

Left/right accuracy was 93.1%. Overall sensitivity of radiographs and CT to detect vertebral canal penetration by an implant were significantly different and estimated as 50.7% and 93.4%, respectively (P<.0001). Sensitivity was significantly higher for complete versus partial penetration and for radiologists compared with nonradiologists for both imaging modalities. Overall specificity of radiographs and CT to detect vertebral canal penetration was 82.9% and 86.4%, respectively (P=.049).

CONCLUSIONS

CT was superior to radiographic assessment and is the recommended imaging modality to assess penetration into the vertebral canal.

CLINICAL RELEVANCE

CT is significantly more accurate in identifying vertebral canal violation by Steinmann pins and should be performed postoperatively to assess implant position.

Treatment of 10 dogs with discospondylitis by fluoroscopy‐guided percutaneous discectomy

Ten dogs suffering from discospondylitis were treated by percutaneous discectomy and local and systemic antibiotic therapy. With fluoroscopic guidance, a cylinder 5 mm in diameter was removed from the centre of the intervertebral space, yielding a fenestration and decompressing the disc without producing any spinal instability. The causative bacteria were identified in nine of the 10 biopsy specimens, but in only three urine cultures and four blood cultures. In two cases, the antibiotics used initially had to be changed owing to the organisms' antibiotic resistance. The clinical signs of the dogs improved markedly after two to nine days (mean 4.2 days) and had resolved completely after five to 14 days (mean 9.1 days). In all the cases the disease could be classified histologically as either acute or chronic, and the disease was classified as chronic in one dog. No side effects were observed.

External fixation of the lumbar spine in a canine model

OBJECTIVE

To compare the mechanical properties of two types of external skeletal fixation of the lumbar spine with polymethylmethacrylate (PMMA)/Steinmann pin fixation in a canine unstable spine model.

STUDY DESIGN

Cadaver study.

SAMPLE POPULATION

Lumbar spines of 17 mature large-breed dogs.

METHODS

Spine stiffness (N-m/deg) in flexion, extension, and rotation under physiological loading conditions and spine strength (N-m) in flexion were determined. Spines were destabilized at L3-L4, instrumented and retested. Fixation techniques included four-pin PMMA (PMMA4), eight-pin PMMA (PMMA8), eight-pin biplanar type I external skeletal fixator (ESF) (SK), and eight-pin spinal arch ESF (ARCHES).

RESULTS

All fixation groups were as stiff as intact spines in extension and rotation and were significantly stiffer in flexion. In flexion, both PMMA8 and ARCHES were significantly stiffer than SK, and PMMA8 was significantly stiffer than PMMA4. In rotation, PMMA8 and ARCHES were significantly stiffer than SK, and in flexion to failure, PMMA8 and ARCHES were significantly stiffer than PMMA4.

CONCLUSIONS

External skeletal spinal fixation (ESSF) has mechanical properties comparable to more commonly used PMMA/pin internal fixation techniques.

CLINICAL RELEVANCE

External fixation of the canine spine has several potential advantages over internal fixation including minimal dissection for pin placement, the ability to span affected vertebrae with placement of implants distant from the site of injury, postoperative adjustability, and complete removal of implants after healing. This study supports the biomechanical stability ESSF of the canine lumbar spine. Further studies are indicated to evaluate zones of consistently safe and secure placement of pins and clinical efficacy.