Radiographic retrospective study of the caudal cervical articular process joints in the horse

Reasons for performing study: Arthropathy of the caudal cervical articular process joints (APJs) in the horse is documented as a cause of ataxia and paresis secondary to spinal cord compression. Enlargement of the caudal APJs is reported to increase with age, but there are no known associations of any other factors. No association of the degree of APJ enlargement with neurological signs seen has been documented. This study investigated the associations of cervical APJ enlargement at the C5‐C6 and C6‐C7 articulations with case subject details (breed, age, sex, usage) and clinical signs. Objectives: To ascertain if there are of any associations between: the subject details and enlargement of the caudal cervical APJs; and the degree of APJ enlargement and the presence and type of clinical signs. Hypotheses: There would be an effect of age, breed and usage on APJ grade, with no effect of sex. Association between grade and clinical signs seen was also investigated. Materials and methods: The radiographs of 122 horses qualified for inclusion. Horses were excluded if they were known to have a neck lesion cranial to C5‐C6, or if the radiographs were rotated or of poor quality. In order to standardise the interpretation of APJ enlargement, a novel grading system was developed and used. Results: An association was found between age and APJ grade at C5‐C6 but not C6‐C7. There was no association between grade, breed, sex and usage, or clinical signs seen. Data also showed a trend for increasing enlargement the more caudal the APJ. Conclusion and potential relevance: The data in this study support that the size of the caudal cervical APJ at the level of C5‐C6, appear to increase with age, but this enlargement may not be significant. Enlargement cannot be associated with breed, sex or discipline of the horse at present, and specific grades and therefore degree of enlargement, cannot necessarily be assumed to be the cause of neurological deficits.     

Multi‐modality diagnostic imaging of a cervical articular process fracture in a Thoroughbred horse including a novel C‐Arm imaging technique

Interpretation of cervical radiographs can be challenging due to the complex anatomy and superimposition of osseous structures on either side of the vertebrae. This report describes the investigation of neck pain in a Thoroughbred gelding following a traumatic fall. Several imaging modalities were used to demonstrate the presence of a fracture of the left cranial articular process of the fourth cervical vertebra (C4), including nuclear scintigraphy, ultrasonography, oblique radiographic projections and a novel cineradiographic technique. Oblique radiographs were superior to standard lateral‐lateral radiographs in both the diagnosis and for monitoring the progression of healing of the articular process fracture in this case.     

The 3D anatomy of the cervical articular process joints in the horse and their topographical relationship to the spinal cord

Reasons for study: Detailed anatomy of the equine cervical articular process joints (APJs) has received little attention in the literature and yet disorders of this joint have been linked to spinal cord compression resulting in severe clinical signs such as ataxia and weakness. This study aimed to describe the 3D anatomy of the APJ in relation to the spinal cord in the horse. Hypothesis: Artificial distension of the APJ causes the joint pouches to extend into the vertebral canal, with the potential for APJ effusion to cause spinal cord compressive disease. Methods: Six cadaveric necks (C1–C7) of clinically normal horses were used in this study. Computed tomography scans of the cervical APJ were acquired after injection of a negative contrast agent to maximal distension. The resulting images were semi‐automatically segmented using greyscale thresholding and reconstructed in 3D by polygonal surface meshing. The 3D reconstructions were used to assess the topographic anatomy of the APJ in relation to the spinal cord and to measure joint volume at each cervical vertebra in relation to vertebrae size. Results: Joint volume varied significantly between joint location (P<0.0001) and was positively correlated to the vertebral site (from cranial to caudal) (r = 0.781, P<0.0001). After distension, the medial outpouch of the APJ extended towards the vertebral canal from a dorsolateral location but in none of the 6 horses was there apparent compression of the dura mater surrounding the spinal cord. There was no significant difference in the extent of medial outpouch at any vertebral level (P = 0.104). Flexion of the neck resulted in minor changes to the shape of the APJ but did not result in the medial outpouch encroaching any closer to the spinal cord. Conclusions: From this study, it appears that in the absence of any other soft tissue or bony changes an effusion of the APJ is unlikely to cause spinal cord compression. However, given that the APJ and spinal cord are in close approximation, in the presence of other anatomical changes, an effusion may have the potential to cause compression. Potential relevance: This study confirms that the APJ extend into the dorsolateral aspect of the vertebral canal in a ventromedial direction, suggesting that oblique myelographic views are recommended for the diagnosis of spinal cord compression when pathology of the APJ is suspected.     

Cervical disc width index is a reliable parameter and consistent in young growing Dutch Warmblood horses

Intervertebral disc disease, as well as the associated alteration of the radiographic intervertebral disc space width, has been reported in horses. Disc height index (DHI) has proven to be an accurate and objective parameter in other species but data related to this parameter are lacking in horses. Therefore, the aims of this retrospective longitudinal diagnostic accuracy study were (a) to evaluate the reliability of measurements within and between observers of the equine Disc Width Index (EDWI) as a parameter for radiographic equine cervical intervertebral disc space width, and (b) to evaluate the sequential development of the EDWI over time. For this, EDWI from all intervertebral disc spaces between second cervical (C) to first thoracic (Th) vertebrae were obtained in a group of 39 Dutch Warmblood horses at 1, 5, and 18 months of age, by one European College of Veterinary Diagnostic Imaging (ECVDI) board‐certified veterinary radiologist (S.V.) and two veterinary students. Bland‐Altmann plots and intraclass Correlation Coefficient revealed a good intra‐ and interobserver agreement. A linear mixed‐effect model did reveal that mean EDWI increases significantly toward the caudal cervical spine, but did not differ significantly for a certain location over time or between sexes. Spearman's rank test did show a significant correlation between the vertebral alignment angle induced by different head‐neck positions and a normalized EDWI (ρ = 0.33, P < .0001). Student's t‐test revealed that the presence of C6‐C7 transposition of the transverse processes did not influence EDWI significantly. It was concluded that EDWI represents a reliable parameter for equine cervical radiographic intervertebral disc space width. Practical implementation of EDWI warrants monitoring in a group of adult horses while maintaining a standardized head‐neck position.     

EX VIVO COMPUTED TOMOGRAPHIC EVALUATION OF MORPHOLOGY VARIATIONS IN EQUINE CERVICAL VERTEBRAE

Diagnostic imaging is one of the pillars in the clinical workup of horses with clinical signs of cervical spinal disease. An improved awareness of morphologic variations in equine cervical vertebrae would be helpful for interpreting findings. The aim of this anatomic study was to describe CT variations in left–right symmetry and morphology of the cervical and cervicothoracic vertebrae in a sample of horses. Postmortem CT examinations of the cervical spine for horses without congenital growth disorders were prospectively and retrospectively recruited. A total of 78 horses (27 foals, 51 mature horses) were evaluated. Twenty‐six horses (33.3%) had homologous changes in which a transposition of the caudal part of the transverse process (caudal ventral tubercle) of C6 toward the ventral aspect of the transverse process of C7 was present (n = 10 bilateral, n = 12 unilateral left‐sided, n = 4 unilateral right‐sided). There was one horse with occipito‐atlantal malformation, two horses with rudimentary first ribs bilaterally, and one horse with bilateral transverse processes at Th1, representing homeotic (transitional) vertebral changes. Chi‐square tests identified no significant differences in the number of conformational variations between the group of mature horses with or without clinical signs (P = 0.81) or between the group of mature horses and the group of foals (P = 0.72). Findings indicated that, in this sample of horses, the most frequently identified variations were homologous variations (transposition of the caudal part of the transverse process of C6–C7) in the caudal equine cervical vertebral column. Homeotic (transitional) variations at the cervicothoracic vertebral column were less common.     

PREVALENCE OF ANATOMICAL VARIATION OF THE SIXTH CERVICAL VERTEBRA AND ASSOCIATION WITH VERTEBRAL CANAL STENOSIS AND ARTICULAR PROCESS OSTEOARTHRITIS IN THE HORSE

The sixth cervical vertebra (C6) has unique morphology due to a ventral extension from the transverse process known as the ventral lamina. Little information was found regarding the prevalence and clinical relevance of morphologic variations. Aims of this observational, retrospective study were to characterize C6 morphologic variations in a large sample of horses. Cervical radiographic studies of 100 horses were retrieved. Data recorded were signalment, clinical history, morphology of the C6 ventral lamina, presence of articular process osteoarthritis, and presence of static vertebral canal stenosis. Morphologic variations were found in C6 vertebrae for 24/100 horses, with symmetric absence of the ventral lamina in nine horses and asymmetric absence in 15. Anomalous C6 vertebrae were more common in Warmbloods, with 19/55 Warmbloods in the population being affected (P = 0.006). No association was found with sex. There was no significant difference in the mean of the intravertebral sagittal ratios between horses with normal or anomalous C6 vertebrae; however there was a significantly greater proportion of horses with anomalous C6 vertebrae that had an intravertebral sagittal ratio of less than 0.5 at C6 (P = 0.047). There was no association between the morphology of C6 and articular process osteoarthritis. Anomalous C6 vertebrae in our population were associated with a higher likelihood of cervical pain (P = 0.013). Authors propose that morphologic variations in the C6 ventral laminae could be linked to other developmental abnormalities such as vertebral canal stenosis, might affect regional biomechanics and should therefore be considered clinically relevant in horses. Future, controlled prospective studies are needed to test this theory.     

Case-Control Comparison of Cervical Spine Radiographs From Horses With a Clinical Diagnosis of Cervical Facet Disease With Normal Horses

The accuracy of using radiographs to diagnose cervical facet osteoarthritis (CFA) in horses is undetermined. Further investigation is required to determine the clinical significance of radiographic evidence of CFA, the prevalence of radiographic changes in horses without clinical signs, and the long-term efficacy of intra-articular CFA treatment. The objectives of this study is to compare degenerative changes of the cervical facet joints of the cervical vertebrae on radiographs of horses with clinical signs of CFA with healthy cohort-matched horses, to compare clinical findings between groups, and to obtain follow-up information on the long-term outcome in treated horses. This is a retrospective case-control cohort-matched comparison study of horses treated for cervical facet disease versus horses with no clinical signs of cervical facet disease. Horses diagnosed with CFA and treated with intra-articular injection of corticosteroids were included. Follow-up information on recovery from treatment was obtained via telephone survey of owners/trainers. Healthy horses with no clinical signs of CFA were matched to treated horses by breed, sex, age, and sport as the control group. Two blinded radiologists reviewed cervical spine radiographs for each horse and recorded CFA score and intravertebral/intervertebral measurements. Clinical and radiographic parameters were compared between treatment and control groups. There was a significant difference in CFA grades for C5-6 and C6-7 between horses with presence of clinical signs and healthy horses. However, interobserver agreement between radiologists for grading CFA was moderate and only 56% of values were identical for both observers. Atrophy of the neck was present on clinical examination in most cases in the treatment group. Dressage horses were overrepresented. Overall, 64% of horses returned to their previous level of performance after treatment. Clinical examination data collected for the treatment group were retrospective and were obtained by different clinicians. Eight owners/trainers were not able to be reached for the survey. There was a significant difference in CFA grades for C5-6 and C6-7 between horses with presence of clinical signs and healthy horses. Despite these statistical differences, the clinical diagnosis of CFA based on radiographic grading alone is questionable because of the lack of agreement between the radiologists. To strengthen the diagnosis, clinical signs of facet disease, in particular atrophy of the neck muscles, need to be present to make this diagnosis. Intra-articular corticosteroid injection was effective at allowing most treated horses to return to athletic use..     

Arthroscopic treatment for cervical articular process joint osteochondrosis in a Thoroughbred horse

A yearling Thoroughbred colt was presented for investigation of neck stiffness and episodes of intermittent neck pain without neurological signs. Osteochondrosis (OCD) of the cervical articular process joints (APJs) was diagnosed with the aid of radiography and computed tomography. An articular osteochondral fragment of the left fourth caudal cervical articular process was removed arthroscopically following a cut down approach to the joint capsule of the affected APJ. Surgical removal resulted in resolution of clinical signs at 4 weeks. However, subsequently the horse was markedly ataxic 6 weeks post surgery after being found cast in its stable. Cervical stenotic myelopathy was considered the most likely cause based on clinical and radiographic signs and the horse was subjected to euthanasia due to a poor prognosis for racing. Post‐mortem examination identified atypical cartilage within several cervical APJs with histological changes consistent with OCD. This case report supports OCD of the APJs as a cause of neck pain and confirms the clinical practicality and short‐term effectiveness of arthroscopic fragment removal. Surgical treatment for cervical OCD should be considered in horses without neurological signs, although case selection is important and the underlying pathology remains a risk factor for the development of subsequent neurological signs.     

A technique for pelvic radiography in the standing horse

REASONS FOR PERFORMING STUDY: An alternative technique of radiographing the pelvis in the standing horse is required, to avoid the risks associated with general anaesthesia. HYPOTHESIS: That lateral oblique radiography in the standing horse would be a useful technique in the investigation of pelvic injury. OBJECTIVES: To describe the technique of lateral oblique pelvic radiography in the standing horse and demonstrate the feasibility and usefulness of this technique. METHODS: A technique for lateral oblique radiography in the standing horse was devised and retrospective review made of radiographic findings in 18 clinical cases. RESULTS: The caudal iliac shaft, greater trochanter of the femur, femoral head, acetabulum and coxofemoral articulation on the side under investigation were visualised consistently using this technique. Of the 18 cases, 3 iliac shaft fractures, 1 acetabular fracture, 2 coxofemoral luxations and 4 horses with new bone formation around the coxofemoral joint and/or proximal femur were identified. CONCLUSIONS: Lateral oblique radiography in the standing, conscious horse can be used to investigate conditions affecting the caudal iliac shaft, coxofemoral articulation and proximal femur in the horse. POTENTIAL RELEVANCE: The technique is straightforward, noninvasive and useful in the investigation of horses with suspected pelvic injury. However, not all pelvic injuries would be identified, and normal radiographic findings do not rule out injury or fractures elsewhere in the pelvis.     

RADIOGRAPHIC TECHNIQUE AND ANATOMY OF THE EQUINE SACROILIAC REGION

Radiography is part of evaluating horses with poor performance and pelvic limb lameness; however, the radiographic appearance of the sacroiliac region is poorly described. The goal of the present study was to describe the use of a simple technique to obtain radiographs of the sacroiliac region in the anesthetized horse and to describe the radiographic appearance of this region. Seventy-nine horses underwent radiography of the pelvis under general anesthesia in dorsal recumbency. During a 5s exposure time the horse was actively ventilated to blur the abdominal viscera, which allowed assessment of individual bone structures in 77 horses. A large variation in the shape of the sacral wings, their articulation with the transverse processes of L6, and the relation of the sacrum to the ilium were observed. Females had significantly narrower width of the sacral wings. Broad sacral wings and bony proliferations at the caudal aspect were commonly observed features and their size was highly correlated with gender. In males, caudal osteophytes were significantly larger than in females. Five horses had transitional or hemitransitional vertebrae. Radiography with the ventilation-induced blurring technique is a simple approach that results in diagnostic quality radiographs and delineation of the highly variable bone structures of the sacroiliac region.     

Radiographic identification of the equine ventral conchal bulla

Involvement of the ventral conchal sinus (VCS) is an important diagnostic and prognostic feature in cases of the equine sinus disease. The authors aimed to ascertain if the caudo-dorsal extension of the VCS, the ventral conchal bulla (VCB) is identifiable on plain radiographs of cadaver skulls without sinus disease. Bilateral frontonasal sinus flaps were made in 10 equine cadaver skulls. Plain lateral, lateral oblique and dorso-ventral radiographs were then obtained followed by the same views taken with stainless steel wire outlining the caudal border of the VCB. Plain radiographs were randomised and blindly evaluated by two observers who marked where they believed the VCB to be positioned. This was then correlated with the true position of the VCB using radiographs with wires in place. The ease of identification of the VCB was classified as 'easy' or 'difficult'. The VCB was correctly identified in 70 per cent of lateral radiographs, but only 45 per cent of lateral oblique radiographs and 17 per cent of dorso-ventral radiographs. If a clinician was confident that he or she could identify the VCB, they were usually correct. Conversely if the clinician judged VCB identification as 'difficult', they usually identified it incorrectly. In the authors' clinical experience, the VCB of horses with sinusitis involving this compartment is more radiologically evident than in clinically normal horses. Knowledge of the normal radiographic anatomy of this structure should aid clinicians in identifying horses with sinusitis affecting the VCS.     

An in vitro biomechanical comparison of a locking compression plate fixation and kerf cut cylinder fixation for ventral arthrodesis of the fourth and the fifth equine cervical vertebrae

Objectives: To (1) define mechanical properties in flexion, extension, and left lateral bending of cadaveric equine 4th and 5th cervical (C4–C5) articulations, (2) compare biomechanical properties of C4–C5 when stabilized with a kerf cut cylinder (KCC) compared with a ventrally placed 4.5 mm locking compression plate (LCP). Study Design: In vitro biomechanical investigation. Sample Population: Cadaveric adult equine cervical vertebral columns (n=54). Methods: Cervical vertebrae aged by horse dentition and size measured from radiographs were divided into 3 age groups then randomly allocated to 3 groups. The C4–C5 articulation was treated differently in each of the groups: KCC group; KCC‐implanted LCP group; 8‐hole 4.5 mm LCP implanted and intact group; no implant. Specimens were randomly subdivided into 1 of 3 loading conditions, before testing to failure under 4‐point bending. Stiffness, yield bending moment, failure bending moment, and failure mode were recorded. General linear models were performed to analyze associations between biomechanical properties and test variables. Results: All specimens failed at the C4–C5 intervertebral articulation. The cervical vertebrae with the LCP construct had significantly higher stiffness, yield bending moment, and failure bending moment than the KCC‐implanted cervical vertebrae. Failure modes differed between groups and varied with loading direction: KCC group, fractures of C5 associated with the KCC were common; LCP group, screw pull out or fractures (of C4 and C5 bodies, during extension and the caudal aspect of C4 during left lateral bending) were common; and intact group, subluxations were most common. Conclusions: In this model, LCP constructs had superior biomechanical properties compared with KCC constructs. Further research investigating the effect of repetitive loading is indicated.     

Gross Osteology,Radiographic and Computed Tomographic Morphology of the Axial Skeleton of the Nine‐Banded Armadillo (Dasypus novemcinctus)

This study used 20 nine‐banded armadillo, four in vivo and 16 cadavers, to describe the osteoarticular anatomy of the axial skeleton by means of digital radiography and computed tomography. Vertebral formula obtained in this sample specimens was seven cervical, 10 thoracic, five lumbar, nine vertebrae related to the synsacrum and 20–27 free caudal vertebrae. Peculiar features of this species were noted as the presence of xenarthrous processes in the caudal thoracic vertebra to the last lumbar vertebra, with prominent mammillary processes in the thoracolumbar segment, fused cervical vertebra from the second to fourth vertebra and the presence of synsacrum related to sacral and caudal vertebra fused to the pelvis. They are homodont animals presenting only molariform teeth with formula of 8/8, totalling 32 teeth. There was no complexity in the execution of radiographic and tomographic examinations, concluding that execution can be carried out in nine‐banded armadillos during the clinical routine for wild animals.     

Diagnosis, management, and outcome in 19 horses with deltoid tuberosity fractures

Objective: To describe the diagnosis and treatment of fractures of the deltoid tuberosity. Study Design: Case series. Methods: Medical records (1992–2009) of 19 horses with radiographic confirmation of deltoid tuberosity fractures were reviewed. Data retrieved included signalment, clinical and diagnostic imaging findings, and treatment. Outcome was determined by telephone questionnaire of owners and referring veterinarians. Results: Most horses were markedly lame on admission and 53% had reduced protraction of the affected limb. All fractures were identified on a cranio45° medial‐caudolateral oblique projection; however, only 32% (6 horses) were detected on a mediolateral projection whereas 86% were evident ultrasonographically. Treatment by local wound care and stall rest resulted in return to athletic function without lameness for 13 of 14 horses that had follow‐up. Conclusions: A cranio45° medial‐caudolateral oblique radiographic view was better than a mediolateral projection for identification of deltoid tuberosity fractures. Ultrasonographic detection of fractures was similar except when gas accumulation obscured the fracture site. Deltoid tuberosity fractures can cause severe lameness but can be treated successfully with conservative management.     

Management of equine ataxia caused by cervical vertebral stenotic myelopathy: A European perspective 2010–2015

The diagnosis and therapy of cervical vertebral stenotic myelopathy (CVSM) are challenging and have been most frequently described in racehorses. We aimed to analyse CVSM cases presented for diagnostic work‐up and treatment in a nonracing horse population. We hypothesised that our diagnostic work‐up protocol including clinical/orthopaedic/neurological/radiographic and myelographic examinations may provide practical reference points for in vivo diagnosis/prognosis and adequate CVSM management. Medical records from 2010 to 2015 were reviewed retrospectively. Cases were included if our standardised work‐up protocol was followed, there was no evidence of any infectious diseases causing the neurological signs, and native cervical radiographs and myelograms confirmed CVSM. Age/breed/sex/type of performance/degree of neurological deficits and number/sites/quality/therapy of stenosis were recorded. Sixty‐two horses met the inclusion criteria. The majority of the horses were aged 5–10 years (44%) or >10 years (35%); nine horses (15%) were 1–4 years and four <1 year (6%) old. Forty‐six horses were Warmbloods (73%), 10 ponies (16%) and six of other breeds (11%). Males were more affected (69%) than females (31%). Sixty‐one percent were pleasure‐horses, 26% were sport‐horses and no information was available for 13%. Most cases presented with mild–moderate neurological signs (grade 2/5 = 18%, grade 2–3/5 = 31%). On myelograms, 23 horses (37%) had single‐level, 22 (35%) had double‐level, and eight (13%) triple‐level stenosis, while nine cases (15%) did not have stenosis. Fifty horses (55%) showed dynamic and 41 (45%) static stenosis. Dynamic stenosis was more common (46%) than static (29%) stenosis and/or combined stenosis (25%). Stenoses were more frequently observed in the mid‐to‐caudal vertebrae. Static stenoses tended to be located more caudally. Based on our protocol, 15% of horses were subjected to euthanasia without therapy, 62% treated conservatively and 23% underwent cervical ventral interbody fusion. In conclusion, our diagnostic work‐up protocol provided practical reference points for in vivo diagnosis/prognosis and adequate management of CVSM in a nonracing horse population.     

Conservative Management of a Cervical Vertebral Fracture in a Gelding

The presentation, diagnostic evaluation, treatment, and 5 years follow-up of a 12-year-old Arabian-Saddlebred cross gelding with neck pain and stiffness, attributable to a fracture of the third cervical vertebrae (C3), is described. Initial cervical spinal radiographs revealed a concave defect in the ventral aspect of the cranial end plate of C3. However, both this finding and ultrasonographic imaging of the area were inconclusive for a fracture. Nuclear scintigraphy revealed that the lesion was metabolically active, prompting computed tomographic imaging that revealed a fracture of C3. Sequential radiographs documented progressive fusion of C2-C3 and no neurological deficits developed over the 5 years after the injury. Cervical vertebral injuries in horses can lead to various clinical signs including ataxia, weakness, and neck stiffness or pain. Diagnosis with cervical radiographs alone can be challenging and, in some cases as the horse in this report, multiple imaging modalities may be required to establish a definitive diagnosis. Horses without neurological signs may recover successfully with conservative medical management, which was performed in this case.