Preliminary evaluation of a novel method for computed tomography quantification of lumbosacral articular process displacement in dogs with and without degenerative lumbosacral stenosis

Objective

This study aimed to describe the diagnostic discrimination and reliability of a novel technique for quantifying lumbosacral articular process displacement (LSAPD) on dorsal plane computed tomography (DPCT) imaging in dogs with and without degenerative lumbosacral stenosis (DLSS).

Study design

DPCT surveys of the lumbosacral vertebral column were performed with dogs positioned in extension and flexion. LSAPD is defined as the distance between the cranial aspects of the L7 and S1 articular processes. The LSAPD ratio is identified by dividing the LSAPD by the length of the L7 articular process. Intraclass correlation coefficients (ICCs) for intra- and inter-observer reliability were calculated, and logistic regressions were used to test for the association of LSAPD and LSAPD ratio with odds of DLSS. Significance was set at 0.05. Receiver operator characteristic (ROC) curves were calculated to determine diagnostic discrimination and optimal cutoff for LSAPD and LSAPD ratio in the diagnosis of DLSS.

Results

Intra- and inter-observer reliabilities were excellent for most measurements. In the current cohort, excluding covariates, the area under the curve (AUC) (95%CI) for LSAPD and LSAPD ratio measured in a flexed position were both 0.89 (0.82-0.96), suggesting potentially excellent discrimination for using this measurement as a marker for diagnosing DLSS, pending further studies. The cutoffs for flexed LSAPD and LSAPD ratio that maximizes Youden's index were ≥ 1.2 mm and ≥ 9%, respectively. When age and weight were subsequently included as covariates in a multivariable analysis, a significant relationship between LSAPD or LSAPD ratio and odds of diagnosis of DLSS was not demonstrated, suggesting the need for a larger sample size.

Conclusion

The results of this study suggest that measurements of LSAPD and LSAPD ratio on DPCT are feasible and reliable, although their diagnostic discrimination in DLSS should be evaluated further in future prospective studies.

Accuracy of Lumbosacral Pedicle Screw Placement in Dogs: A Novel 3D Printed Patient-Specific Drill Guide versus Freehand Technique in Novice and Expert Surgeons

OBJECTIVE

 The aim of this study was to compare the accuracy of pedicle screw placement at the canine lumbosacral junction using a novel unilateral three-dimensional printed patient-specific guide (3D-PSG) versus a freehand drilling technique. Additionally, accuracy of screw placement between a novice and an experienced surgeon was determined.

STUDY DESIGN

 Preoperative computed tomography images from 20 lumbosacral cadaveric specimens were used to design a novel unilateral 3D-PSG for the L7 and sacral vertebrae which was printed in acryl-nitrile butadiene styrene plastic. A novice and an expert surgeon each placed 3.5mm cortical screws in 10 cadavers; on the left using the unilateral 3D-PSG and by the freehand (anatomic landmark) technique on the right.

RESULTS

 Sixty screws were placed using the unilateral 3D-PSG and 60 using the freehand technique. There was no statistical difference in accuracy for the comparison between methods performed by the expert (p = 0.679) and novice (p = 0.761) surgeon, nor between an expert and novice surgeon overall (p = 0.923). Unexpectedly, the use of a unilateral 3D-PSG increased variability for the expert surgeon in our study (p = 0.0314).

CONCLUSION

 Using a novel unilateral 3D-PSG did not improve the accuracy of screw placement for lumbosacral stabilization by a novice surgeon compared with an expert surgeon in lumbar spine surgery. This may reflect a suboptimal PSG design.

Comparison of Cervical Stabilization with Transpedicular Pins and Polymethylmethacrylate versus Transvertebral Body Polyaxial Screws with or without an Interbody Distractor in Dogs

OBJECTIVE

 The main aim of this study was to compare the biomechanical properties of caudal cervical vertebral stabilization using bicortical transpedicular pins with polymethylmethacrylate (PMMA) versus transvertebral body polyaxial screws and connecting rods with or without an interbody distractor.

STUDY DESIGN

 Ten canine cervical vertebral columns (C2-T3) were used. Four models (intact, transvertebral body polyaxial screw with interbody distractor [polyaxial + distractor], transvertebral body polyaxial screw without interbody distractor [polyaxial - distractor] and bicortical transpedicular pins/polymethylmethacrylate [pin-PMMA]) were applied to C6-7 sequentially on the same specimens. Angular range of motion (AROM) in the form of flexion and extension was measured at C4-5, C5-6 and C6-7 in all groups.

RESULTS

 Treated vertebral specimens had significantly less AROM than unaltered specimens. There was no significant difference in AROM between the experimental groups at C6 and C7. Angular range of motion ratio in flexion-extension was 80.8, 72.7 and 78.3% for polyaxial + distractor, polyaxial - distractor and pin-PMMA groups, respectively, which were less than the intact group. There was no significant increase in the range of motion of the adjacent vertebrae after stabilization.

CONCLUSION

 Stabilization obtained with transvertebral body polyaxial screws was comparable to that from the well-established bicortical pins/PMMA construct. Association of an intervertebral distractor did not change AROM of the polyaxial screw constructs.

Postoperative outcomes of combined surgery comprising dorsal laminectomy, transarticular screws, pedicle screws and polymethylmethacrylate for dorsal fixation in 21 dogs with degenerative lumbosacral stenosis

OBJECTIVE

To retrospectively review the efficacy of combined surgery comprising dorsal laminectomy and dorsal fixation using screws and polymethylmethacrylate as treatment for dogs with degenerative lumbosacral stenosis (DLSS).

ANIMALS

21 client owned dogs diagnosed with DLSS and treated surgically.

PROCEDURES

Based on clinical records, signalments, clinical signs, findings from orthopedic and neurological examinations, imaging findings, and postoperative complications were evaluated at the following time points: preoperatively, postoperatively, and 3, 6, 12, 24, and 36 months after surgery.

RESULTS

In all 21 cases, clinical signs were alleviated, proprioceptive deficits were improved from 3 months after surgery, and no recurrence of clinical signs was observed during the observation period. Minor complications were observed in 6 cases (28.6%), including implant failure in 2 (9.5%), delayed healing of surgical wounds in 2 (9.5%), seroma in 1 (4.8%), and swelling of the affected area in 1 (4.8%). There was no case with major complications.

CLINICAL RELEVANCE

Combined surgery comprising dorsal laminectomy and dorsal fixation using screws and polymethylmethacrylate is a useful treatment that can improve long-term clinical signs in dogs with DLSS.

Pedicle screws implantation in polymethylmethacrylate construct to stabilise sixth lumbar vertebral body fracture in dogs: 5 cases (2015-2018)

OBJECTIVES

To assess the feasibility and outcome of pedicle screw implantation on sixth lumbar vertebral body fractures.

MATERIALS AND METHODS

Dogs with sixth lumbar vertebral body fractures stabilised using L6 and L7 (±L5) pedicular implantation via a dorsal approach preferentially and conventional vertebral body implantation otherwise were reviewed. Coaptation was made with bone cement. Complete neurological examination, pre and postoperative imaging consistent with L6 body fracture (radiographs ± CT scan) and follow up including clinical examination and radiographs 3 to 5 weeks post-operatively were required as inclusion criteria. When available, owner interview and/or clinical examination and imaging (radiographs ± CT scan) at least 1 year after surgery were reported.

RESULTS

Five dogs met the inclusion criteria. Dorsal pedicle screws implantation was feasible in all L7 vertebrae and in four L6 vertebrae. Adequate implantation was observed in all of the post-operative radiographs and on all of the three CT scans available. At 3 to 6 weeks after surgery, neurological status and locomotion were normal in four dogs, while one dog suffering from severe sciatic neuropathy did not regain normal locomotion. At least 1 year after surgery, clinical outcome was excellent for four dogs and imaging by radiography and CT scan were available for three dogs and showed complete healing of the fracture and correct positioning of the implants. The dog suffering from sciatic neuropathy had a further trauma and was euthanased 7 weeks after the surgery.

CLINICAL SIGNIFICANCE

In this case series, pedicle screw implantation achieved stabilisation of L6 vertebral body fractures, with full recovery observed in four out of five dogs. Further studies are required to confirm the safety and the effectiveness of this intervention.

Ex-vivo evaluation of the three-column concept in canine thoracolumbar fractures

ABSTRACT Traumatic events such as a motor vehicle accident or falling from heights are very common in veterinary medicine and often lead to vertebral fracture-luxation with concomitant spinal cord injuries, mostly in the thoracolumbar spine. The purpose of this cadaveric biomechanical study was to determine the feasibility of the three-column concept in canine thoracolumbar segments with induced fractures. Eighteen Functional Spinal Units (FSU) of the thoracolumbar segments (T12-L2) were collected from 18 medium-sized adult dog cadavers and were subjected to flexion-extension and lateral bending tests so that range of motion (ROM) was recorded with a goniometer. Fractures were induced by compressive loads applied by a universal testing machine (EMIC®). After this, specimens were screened using computed tomography (CT) and the fractures were graded as affecting one, two or three columns, and divided into groups A, B, and C, respectively. Post-fracture range of motion (ROM) was compared with the previous results. Groups B and C (with fractures in two or three columns) had instability in the two axes evaluated (P<0.05). The outcomes of this study support the applicability of the three-column theory to thoracolumbar spines of dogs, as the FSUs that suffered fractures in two or more columns showed axial instability.

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.

Biomechanical comparison of locking compression plate fixation and a novel pedicle screw external fixation to repair equine mandibular fractures

OBJECTIVE

To determine the biomechanical properties of pedicle screw external fixation (PDW) for equine mandibular fracture repair and compare PDW to locking compression plates (LCP).

STUDY DESIGN

Cadaveric study.

SAMPLE POPULATION

Sixteen adult equine mandibles.

METHODS

Four mandibles were kept intact, while 12 were osteotomized and stabilized with the LCP or PDW construct (6 mandibles/group). Failure, stiffness, and yield were calculated from quasi-static ramp to failure and compared with previous analysis of mandibular fracture constructs. Tooth root involvement and method of failure were determined from radiographs and videos.

RESULTS

Locking compression plate constructs achieved greater stiffness and load at failure (4656 ± 577 N-m/radian, 558 ± 27 N-m P < .05) compared with PDW constructs (2626 ± 127 N-m/radian, 315 ± 48 N-m). Yield did not differ between types of fixation (369 ± 57 N-m, 193 ± 35 N-m, P = .145). Tooth involvement was noted in two LCP constructs with failure via bone fracture. Pedicle screw external fixation constructs failed via wire unraveling and screw bending.

CONCLUSION

Locking compression plate fixation increased stiffness and failure of constructs but did not influence yield. It also increased the risk to tooth root involvement relative to fixation with PDW. Compared with another study, PDW offered stiffness and failure similar to an intraoral splint with interdental wires, external fixator (EF), and external fixator with wires (EFW) and yield similar to an EF, an EFW, and a dynamic compression plate.

CLINICAL RELEVANCE

Pedicle screw external fixation offers biomechanical stability comparable to other relevant mandibular fixation techniques and reduces the risk of tooth root damage compared with LCP fixation.

Influence of a customized three-dimensionally printed drill guide on the accuracy of pedicle screw placement in lumbosacral vertebrae: An ex vivo study

OBJECTIVE

To compare the accuracy of pedicle screw insertion (PSI) into canine lumbosacral vertebrae with custom-made three-dimensionally (3D)-printed drill guides or freehand insertion.

STUDY DESIGN

Ex vivo study.

SAMPLE POPULATION

Nineteen canine lumbosacral specimens.

METHODS

Drill guides for PSI were designed on the basis of safe screw insertion trajectories by using preoperative computed tomography (CT) and produced by 3D printing of templates. Right and left sides of the specimens were randomly allocated to two groups; 4-mm pedicle screws were inserted in L5-L6 and L7-S1 spinal segments either freehand (control group) or with custom-made drill guides (guide group). Sixty-six screws were inserted with each method. Insertion angles (α, β), bone stock, and vertebral canal breach were assessed according to postoperative CT. χ² Tests were used to compare vertebral canal breach between groups and vertebrae.

RESULTS

Breaches in the vertebral canal were less common (P < .001) when screws were placed with a guide in the guide group (9/66, 14%) than without a guide (30/66, 45%). The rate of vertebral canal breach differed at L5 (P = .021) but not at L6 (P = .05), L7 (P = .075) or S1 (P = .658). The angle of insertion (α) did not differ between specimens with and without breaches (guide, P = .068; control, P = .394).

CONCLUSION

The use of a customized 3D-printed guide generally improved the accuracy of PSI in canine lumbosacral vertebrae, although statistical significance was reached only at L5.

CLINICAL SIGNIFICANCE

The use of customized drill guides may be considered as an alternative to freehand PSI in the lumbosacral area, especially for L5-L6 vertebrae.

Accuracy and Efficacy of a Patient-Specific Drill Guide Template System for Lumbosacral Junction Fixation in Medium and Small Dogs: Cadaveric Study and Clinical Cases

Objectives: To develop drill guide templates as an intraoperative guide, and to evaluate the accuracy and safety of screw placement in the lumbosacral junction.

Samples: Canine cadaveric specimens of the lumbosacral junction (n = 6), and clinical cases of lumbosacral instability (n = 3).

Procedures: Computed tomography data of the lumbosacral region of cadaveric specimens and clinical cases were obtained. The optimum screw trajectories were determined and drill guide templates were fabricated using a three-dimensional printing system. Drill holes were made using the templates in cadaveric specimens and clinical cases, and lumbosacral fixation was performed in clinical cases. Computed tomography images were obtained to compare the planned and postoperative drill hole trajectories, and the accuracy and safety of drilling and screw placement in the lumbosacral junction were evaluated.

Results: Thirty-six drill holes were made in cadaveric specimens. The overall mean drill hole deviation was 2.05 ± 1.32 mm. A total of 12 screws were placed in the lumbosacral junctions of three clinical cases. The overall mean drill hole deviation was 2.43 ± 1.09 mm. Clinical signs improved within 2 weeks in the clinical cases. All drill holes were completely located within the bone in cadaveric specimens and clinical cases.

Conclusion and Clinical Relevance: The surgical procedures using the drill guide templates were performed safely with good clinical outcomes. The drill guide template system provided useful surgical guidance to safely and precisely perform screw placement for lumbosacral fixation surgery in small 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.

Update on Surgical Treatment of Wobblers

Cervical vertebral compressive myelopathy (CVCM) represents the most significant disease of the spinal cord in horses for which surgical treatment is described. Current surgical methods used include ventral interbody fusion with kerf cut cylinders and dorsal laminectomy. Polyaxial pedicle screw and rod constructs and ventral locking compression plating have been introduced in the treatment of equine CVCM and present promising alternative approaches to achieve ventral interbody fusion. Advancements in diagnostic imaging and endoscopy of the cervical vertebral canal may improve reliable preoperative identification of the exact locations of spinal cord compression in horses with CVCM to improve postoperative outcomes.

Placement of vertebral screws for spinal stabilization and distraction in a dog with disc-associate cervical spondylomyelopathy: case report

ABSTRACT A 10-year-old male Rottweiler was evaluated for a 2-month history of recurrent forelimb weakness. Neurologic examination revealed proprioceptive ataxia, tetraparesis and moderate cervical pain. Disk-associated cervical spondylomyelopathy (CSM) with static lesion at C3-4 was diagnosed based on magnetic resonance imaging (MRI). The dog was surgically treated by a ventral slot procedure and distraction-stabilization of the vertebral bodies through insertion of vertebral screws with transverse connective bars. The patient had favorable clinical outcome. Neurologic assessment performed 120 days after surgery showed absence of neurologic defects. Radiographic assessment performed at the same time indicated adequate spinal cord decompression although vertebral fusion was not achieved. To the authors’ knowledge, this is the first case of distraction-stabilization with vertebral (pedicle) screws to treat CSM in a dog. The treatment was well tolerated with no complications and excellent outcome and can be a viable option for this condition.

Cervical stabilization with polyaxial pedicle screw and rod construct in horses: A proof of concept study

OBJECTIVE

To evaluate safety and efficacy of a novel technique for cervical stabilization.

STUDY DESIGN

In vivo experimental.

ANIMALS

Four normal adult quarterhorse crossbreed horses (2-4 years of age, > 250 kg).

METHODS

One mid-cervical spinal unit (C3-C4) was distracted with a porous metal interbody fusion device (IFD) and stabilized with a polyaxial pedicle screw and rod construct. Neurologic examinations were performed preoperatively and postoperatively. Radiographs of the fusion site and adjoining vertebrae were obtained preoperatively and monthly. Horses were euthanized at 8 months and spinal units were evaluated for osseointegration and implant safety via micro-computed tomography (CT), histology, and histomorphometry.

RESULTS

The procedure was performed safely in all horses, without severe postoperative complications. Evaluation of radiographs revealed no implant failure, implant migration, or spinal unit instability in any of the horses. The presence of new bone formation around the screw and rod constructs was confirmed via micro-CT. No evidence of inflammation or iatrogenic damage was noted from histology. New bone was present within the IFD in all horses, with variable osseointegration on the cranial and caudal surfaces of the implant in 3 horses.

CONCLUSION

The novel technique reported in the present study was safely applied to stabilize the C3-C4 spinal unit in the horses tested here and led to variable osseointegration within 8 months.

CLINICAL SIGNIFICANCE

The results of this study justify evaluation of this technique in horses with a diagnosis of cervical vertebral compressive myelopathy.

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.

Uso do Clamp and Rod Internal Fixation pedicular na estabilização da coluna lombossacra em felino: relato de caso

RESUMO Objetivou-se reportar, pela primeira vez descrita até então, a fixação de uma fratura de sétima vértebra lombar (L7) com luxação de L7-S1, por meio de fixação pedicular, utilizando-se Clamp and Rod Internal Fixation (CRIF) em um gato. Um felino de um ano de idade, macho, SRD, foi atendido com histórico de atropelamento havia sete dias, apresentando paraparesia não ambulatória secundária à fratura da sétima vértebra lombar e compressão da cauda equina. Após avaliação geral do paciente, no dia seguinte, ele foi submetido à cirurgia descompressiva por meio de laminectomia dorsal e posterior estabilização pedicular entre L7 e S1, utilizando-se CRIF bilateralmente. O paciente apresentou evolução favorável com deambulação normal após 15 dias do procedimento cirúrgico.

The use of autologous neurogenically-induced bone marrow-derived mesenchymal stem cells for the treatment of paraplegic dogs without nociception due to spinal trauma

The aim of this study was to investigate the effects of percutaneous transplanted autologous neurogenically-induced bone marrow-derived mesenchymal stem cells (NIBM-MSCs) in paraplegic dogs without deep pain perception (DPP) secondary to external spinal trauma. Thirteen client owned dogs that had failed in improvement neurologically at least 42 days after conservative management, decompression and decompression-stabilization were included in the study. Each dog received two doses of autologous 5.0 × 10⁶ NIBM-MSCs suspension, which were positive to 2',3'-Cyclic-nucleotide-3'-phosphodiesterase (CNPase) and Microtubule-associated protein 2 (MAP-2), as well as to Glial fibrillary acidic protein (GFAP) and beta III tubulin. The cells were injected into the spinal cord through the hemilaminectomy or laminectomy defects percutaneously with 21 days interval for 2 times. The results were evaluated using Texas Spinal Cord Injury Scale (TSCIS), somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) at the admission time, cell transplantation procedures and during 2, 5, 7 and 12th months after the second cell transplantation. Improvement after cell transplantation in gait, nociception, proprioception, SEP and MEP results was observed in just 2 cases, and only gait score improvement was seen in 6 cases, and no improvement was recorded in 5 cases. All progresses were observed until 2nd month after the second cell transplantation, however, there was no improvement after this period. In conclusion, percutaneous transplantation of autologous NIBM-MSCs is a promising candidate modality for cases with spinal cord injury after spinal trauma and poor prognosis.

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.

The biological basis of degenerative disc disease: proteomic and biomechanical analysis of the canine intervertebral disc

INTRODUCTION

In the present study, we sought to quantify and contrast the secretome and biomechanical properties of the non-chondrodystrophic (NCD) and chondrodystrophic (CD) canine intervertebral disc (IVD) nucleus pulposus (NP).

METHODS

We used iTRAQ proteomic methods to quantify the secretome of both CD and NCD NP. Differential levels of proteins detected were further verified using immunohistochemistry, Western blotting, and proteoglycan extraction in order to evaluate the integrity of the small leucine-rich proteoglycans (SLRPs) decorin and biglycan. Additionally, we used robotic biomechanical testing to evaluate the biomechanical properties of spinal motion segments from both CD and NCD canines.

RESULTS

We detected differential levels of decorin, biglycan, and fibronectin, as well as of other important extracellular matrix (ECM)-related proteins, such as fibromodulin and HAPLN1 in the IVD NP obtained from CD canines compared with NCD canines. The core proteins of the vital SLRPs decorin and biglycan were fragmented in CD NP but were intact in the NP of the NCD animals. CD and NCD vertebral motion segments demonstrated significant differences, with the CD segments having less stiffness and a more varied range of motion.

CONCLUSIONS

The CD NP recapitulates key elements of human degenerative disc disease. Our data suggest that at least some of the compromised biomechanical properties of the degenerative disc arise from fibrocartilaginous metaplasia of the NP secondary to fragmentation of SLRP core proteins and associated degenerative changes affecting the ECM. This study demonstrates that the degenerative changes that naturally occur within the CD NP make this animal a valuable animal model with which to study IVD degeneration and potential biological therapeutics.

In vitro biomechanical evaluation of internal fixation techniques on the canine lumbosacral junction

Few biomechanical studies have evaluated the effect of internal stabilization techniques after decompressive surgery on the stability of the canine lumbosacral junction. The purpose of this canine cadaver study is to evaluate the stability of the canine lumbosacral (LS) spine in flexion and extension following laminectomy and discectomy and then stabilization with each of the three techniques: pins and polymethylmethacrylate (P/PMMA), two dorsal locking plates (SOP) or bilateral transarticular facet screws (FACET).Using a cantilever biomechanical system, bending moments were applied to the LS and range of motion (ROM) was recorded via a rotational potentiometer. With 3 Nm, the ROM (n = 4 in each group) for P/PMMA, SOP and FACET were 1.92 ± 0.96°, 2.56 ± 0.55°and 3.18 ± 1.14°, respectively. With moments up to 35 Nm, the P/PMMA specimens appeared stable. Sacroiliac motion in the SOP and FACET groups invalidated further comparisons. Each of the stabilization techniques (P/PMMA, SOP, and FACET) significantly decreased the range of motion in flexion and extension for low bending moments.

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.

Transarticular facet screw stabilization and dorsal laminectomy in 26 dogs with degenerative lumbosacral stenosis with instability

OBJECTIVE

To describe outcome after transarticular facet screw stabilization and dorsal laminectomy for treatment of dynamic degenerative lumbosacral stenosis (DLS) in 26 dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 26) with dynamic DLS.

METHODS

Medical records (2004-2009) of dogs treated with transarticular facet screw stabilization and dorsal laminectomy were reviewed. Dogs (n = 26) were available for immediate postoperative follow-up, 21 dogs at 6 weeks, and 15 at greater than 6 months. Dogs were evaluated by radiographic assessment and owner questionnaire. Lumbosacral (LS) intervertebral disc (IVD) spaces were measured on pre and postoperative 6-week and 6-month radiographs.

RESULTS

In 23 dogs, improvement in clinical signs occurred within 7 days of surgery. Overall postsurgical complication rate directly related to the surgical procedure was 15.4%. LS IVD space measurements taken immediately postoperatively, at 6 weeks, and ≥ 6 months were all significantly increased compared with preoperative measurements. All working dogs (4) returned to full work within 14 months. Most owners (85%) reported their dog was ambulating normally at 6 months with no perceptible lameness during normal activity. All owners perceived their dog's ability to walk, run, and jump after surgery to be improved.

CONCLUSIONS

Transarticular facet screw stabilization and dorsal laminectomy maintains distraction of the LS IVD space for medium-to-large breed dogs with dynamic DLS with a high degree of owner satisfaction, and is comparable to other reported surgical techniques for DLS.

Biomechanical assessment of the effects of decompressive surgery in non-chondrodystrophic and chondrodystrophic canine multisegmented lumbar spines

PURPOSE

Dogs are often used as an animal model in spinal research, but consideration should be given to the breed used as chondrodystrophic (CD) dog breeds always develop IVD degeneration at an early age, whereas non-chondrodystrophic (NCD) dog breeds may develop IVD degeneration, but only later in life. The aim of this study was to provide a mechanical characterization of the NCD [non-degenerated intervertebral discs (IVDs), rich in notochordal cells] and CD (degenerated IVDs, rich in chondrocyte-like cells) canine spine before and after decompressive surgery (nucleotomy).

METHODS

The biomechanical properties of multisegmented lumbar spine specimens (T13-L5 and L5-Cd1) from 2-year-old NCD dogs (healthy) and CD dogs (early degeneration) were investigated in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), in the native state and after nucleotomy of L2-L3 or dorsal laminectomy and nucleotomy of L7-S1. The range of motion (ROM), neutral zone (NZ), and NZ stiffness (NZS) of L1-L2, L2-L3, L6-L7, and L7-S1 were calculated.

RESULTS

In native spines in both dog groups, the greatest mobility in FE was found at L7-S1, and the greatest mobility in LB at L2-L3. Surgery significantly increased the ROM and NZ, and significantly decreased the NZS in FE, LB, and AR in both breed groups. However, surgery at L2-L3 resulted in a significantly larger increase in NZ and decrease in NZS in the CD spines compared with the NCD spines, whereas surgery at L7-S1 induced a significantly larger increase in ROM and decrease in NZS in the NCD spines compared with the CD spines.

CONCLUSIONS

Spinal biomechanics significantly differ between NCD and CD dogs and researchers should consider this aspect when using the dog as a model for spinal research.

Biomechanical analysis of torsion and shear forces in lumbar and lumbosacral spine segments of nonchondrodystrophic dogs

OBJECTIVE

To determine stiffness and load-displacement curves as a biomechanical response to applied torsion and shear forces in cadaveric canine lumbar and lumbosacral specimens.

STUDY DESIGN

Biomechanical study.

ANIMALS

Caudal lumbar and lumbosacral functional spine units (FSU) of nonchondrodystrophic large-breed dogs (n=31) with radiographically normal spines.

METHODS

FSU from dogs without musculoskeletal disease were tested in torsion in a custom-built spine loading simulator with 6 degrees of freedom, which uses orthogonally mounted electric motors to apply pure axial rotation. For shear tests, specimens were mounted to a custom-made shear-testing device, driven by a servo hydraulic testing machine. Load-displacement curves were recorded for torsion and shear.

RESULTS

Left and right torsion stiffness was not different within each FSU level; however, torsional stiffness of L7-S1 was significantly smaller compared with lumbar FSU (L4-5-L6-7). Ventral/dorsal stiffness was significantly different from lateral stiffness within an individual FSU level for L5-6, L6-7, and L7-S1 but not for L4-5. When the data from 4 tested shear directions from the same specimen were pooled, level L5-6 was significantly stiffer than L7-S1.

CONCLUSIONS

Increased range of motion of the lumbosacral joint is reflected by an overall decreased shear and rotational stiffness at the lumbosacral FSU.

CLINICAL RELEVANCE

Data from dogs with disc degeneration have to be collected, analyzed, and compared with results from our chondrodystrophic large-breed dogs with radiographically normal spines.