Distances between thoracic spinous processes in Warmblood foals: A radiographic study

Reason for performing study: The aetiological factors behind impinged or overriding of dorsal spinous processes (‘kissing spine syndrome’, KSS) are not clearly understood. Back conformation, breed, age, training and gender may play important roles in this condition. Radiographic changes vary and abnormalities are seen in many clinically normal horses, but the conclusion of previous studies in mature horses is that interspinous spaces <4 mm are considered too narrow and potentially indicative of KSS. Objectives: To evaluate whether narrowing of the interspinous space was present in a population of normal Warmblood foals. Materials and methods: The mean interspinous space width in the area of T10–L1 was measured on radiographs from 25 Warmblood foals aged 9–88 days. Results: Mean ± s.d. interspinous space width was found to be between 5.9 ± 1.2 and 8.9 ± 2.6 mm with the narrowest space in the area T16–T17 and the widest space in T10–T12. No interspinous spaces were <4 mm wide. Gender and location of the interspinous space significantly affected the width of the distance between the spinous processes. Conclusions and potential relevance: In this study none of the interspinous spaces were <4 mm and therefore none of the foals showed signs of impinged or overriding of dorsal spinous processes known as KSS based on the current definitions. Consequently, in this population, there did not appear to be a congenital narrowing of the interspinous space. However, long‐term follow‐up studies, including detailed information on imposed factors such as training, are needed in order to further elucidate a possible congenital component in the aetiology of KSS.     

COMPARISON OF RADIOGRAPHIC AND SCINTIGRAPHIC FINDINGS OF THE SPINOUS PROCESSES IN THE EQUINE THORACOLUMBAR REGION

Back pain is common in horses, but there has been no large‐scale in‐depth study describing radiographic changes of the spinous processes, the relationship between radiographic and scintigraphic findings, and the effect of size, age, breed, or discipline. The objectives were to investigate the frequency of occurrence in horses with perceived back pain of: (1) radiographic alteration of the spinous process structure; (2) increased radiopharmaceutical uptake (IRU) in the spinous processes; and (3) to compare radiographic and scintigraphic findings; and to determine if there was breed, gender, age, bodyweight, height, or work discipline predisposition for close, impinging, or overriding spinous processes. Radiographic and scintigraphic images of the thoracolumbar spine of 604 horses were graded. A radiographic grade for each spinous process (T8–L6) was assigned (0–7). The maximum radiographic grade for each horse was defined as the highest grade assigned to any spinous process; the total radiographic grade was the sum of all grades for each horse. A scintigraphic grade for each spinous process was determined (0–3). The maximum scintigraphic grade for each horse was defined as the highest grade assigned to any spinous process; the total scintigraphic grade was the sum of all grades for each horse. Associations between radiology and scintigraphy and age, gender, breed, height, weight, and discipline were analyzed statistically. The severity of radiographic lesions of the spinous processes was associated with the severity of scintigraphic abnormalities. The caudal thoracic spine (T14–T17) was most frequently affected. There was a significant breed and age effect, with Thoroughbreds and older horses having higher total and maximum radiographic grades. The severity of the lesions of the spinous processes was significantly associated with the presence of osteoarthritis of the articular process joints. It was concluded that there is a wide range of radiographic abnormalities of the spinous processes seen in horses with or without back pain. There is an association between radiographic and scintigraphic grades of the spinous processes.     

Relationship between scintigraphic and radiographic evaluations of spinous processes in the thoracolumbar spine in riding horses without clinical signs of back problems

REASONS FOR PERFORMING STUDY: Radiography and scintigraphy are used to aid diagnosis of the cause of back pain, but a large variation in appearance and radiopharmaceutical uptake in fully functioning horses make diagnosis difficult. OBJECTIVES: To describe the range of and compare scintigraphic and radiographic findings in the spinous processes of horses without clinical signs of back problems. METHODS: Thirty-three apparently normal riding horses underwent scintigraphic and radiographic examinations of the spinous processes in the thoracolumbar spine. Scintigraphic images were evaluated in a continuous blue, green and red colour scale, and the level of radiopharmaceutical uptake in the spinous processes from T10-L2 was graded into none, mild, moderate or severe increased radiopharmaceutical uptake. Structural changes along the borders of the spinous processes and the width of the interspinous spaces from T10-L2 were recorded. RESULTS: Only 7 horses had no scintigraphic or radiographic findings. Nine horses had no increased radiopharmaceutical uptake, 17 had no sclerosis, 21 had no radiolucencies and 11 had normal spacing of the spinous processes (>4 mm wide). The majority of findings in 26 horses were located from T13-18 and were mild. CONCLUSIONS: The findings of a wide spectrum of scintigraphic and radiographic changes leads to the conclusion that changes within this range found in affected horses cannot be interpreted as clinically significant. POTENTIAL RELEVANCE: To determine whether scintigraphy and/or radiography can be used to separate horses with back pain from horses without clinical signs, the results from this study should be compared to the scintigraphic and radiographic findings in horses with clinical signs.     

Structure and Innervation of the Equine Supraspinous and Interspinous Ligaments

Pain related to the osseous thoracolumbar spine is common in the equine athlete, with minimal information available regarding soft tissue pathology. The aims of this study were to describe the anatomy of the equine SSL and ISL (supraspinous and interspinous ligaments) in detail and to assess the innervation of the ligaments and their myofascial attachments including the thoracolumbar fascia. Ten equine thoracolumbar spines (T15‐L1) were dissected to define structure and anatomy of the SSL, ISL and adjacent myofascial attachments. Morphological evaluation included histology, electron microscopy and immunohistochemistry (S100 and Substance P) of the SSL, ISL, adjacent fascial attachments, connective tissue and musculature. The anatomical study demonstrated that the SSL and ISL tissues merge with the adjacent myofascia. The ISL has a crossing fibre arrangement consisting of four ligamentous layers with adipose tissue axially. A high proportion of single nerve fibres were detected in the SSL (mean = 2.08 fibres/mm²) and ISL (mean = 0.75 fibres/mm²), with the larger nerves located between the ligamentous and muscular tissue. The oblique crossing arrangement of the fibres of the ISL likely functions to resist distractive and rotational forces, therefore stabilizing the equine thoracolumbar spine. The dense sensory innervation within the SSL and ISL could explain the severe pain experienced by some horses with impinging dorsal spinous processes. Documentation of the nervous supply of the soft tissues associated with the dorsal spinous processes is a key step towards improving our understanding of equine back pain.     

Enthesophytosis and Impingement of the Dorsal Spinous Processes in the Equine Thoracolumbar Spine

Impingement of the dorsal spinous processes (DSPs) is a common cause of pain and poor performance in sport horses, but there is limited information regarding regional differences in the prevalence and severity of DSP osseous lesions in the equine thoracolumbar spine. It was hypothesized that lesion severity would increase with horse age and height, and that severe lesions would be more prevalent in the mid-caudal thoracic region. The thoracolumbar spines of 33 horses were removed postmortem, disarticulated, and boiled out. The thoracic and lumbar DSPs were examined for the presence of proliferative or lytic osseous lesions of the DSPs. Age and height of the horses were recorded, and severity of pathologic changes at each vertebral level was scored using an ordinal grading system (grades 0–3) and a continuous visual analog scale (VAS). Osseous lesions of the DSPs were present at every vertebral level from C7–T1 to L6–S1, and 70% of horses had at least one lesion of severity grade 2 or higher. Grade 3 lesions were found in the cranial thoracic (T2–T4), mid-thoracic to cranial lumbar (T11–L1) and mid-lumbar (L4–L5) segments. Analysis of VAS data using analysis of variance indicated that increasing age and height were associated with more severe osseous lesions (P < .001). DSP osseous lesions occur frequently in horses with more severe lesions in the cranial thoracic, mid to caudal thoracic, and mid-lumbar regions. Lesions in the cranial thoracic and lumbar regions present a challenge for diagnostic imaging and may be underdiagnosed clinically.     

THE EFFECTS OF ROTATION ON THE RADIOGRAPHIC APPEARANCE OF THE CANINE CARDIAC SILHOUETTE IN DORSAL RECUMBENCY

Cardiac mensuration was done on thoracic radiographs of Beagles to determine the effects of rotation on the cardiac silhouette in dorsal recumbency. As the thorax became more rotated, surfaces of the heart not normally seen were projected, making interpretation of cardiac changes unreliable. A positioning standard based on the relationship of the dorsal spinous processes to the vertebral body was developed. If the tips of the dorsal spinous processes were within the bounds of the vertebral bodies, the radiographs were suitable for cardiac interpretation. If the tips of the dorsal spinous processes were outside the bounds of the vertebral bodies, there was enough rotation to make interpretation unreliable. A microcomputer, digitizer pad, and a BASIC language program were used to input, store, and calculate the various cardiac mensuration parameters.     

The treatment of horses with chronic back pain by resecting the summits of the impinging dorsal spinous processes.

This paper describes the surgical treatment of 14 horses exhibiting chronic back pain attributed to impaction and overriding of the dorsal spines in the thoracolumbar region. The technique involved the resection of the summits of one or more dorsal spines following midline division of the supraspinous ligament. All the horses returned to full work after a convalescent period of at least four months, and 12 of them showed considerable improvement in their form and performance. A post-surgical complication encountered in one case was the development of new bone on the edge of a resected spine. This lesion, which pressed on the dorsal spine immediately caudal to it, was removed subsequently at a second operation and no further sequelae occurred.     

ULTRASONOGRAPHIC TECHNIQUE AND NORMAL ANATOMIC FEATURES OF THE SACROILIAC REGION IN HORSES

The purpose of this study was to establish the normal percutaneous ultrasonographic appearance of anatomic structures within the equine sacroiliac region. Percutaneous ultrasonography was performed in a cranial-to-caudal direction in 10 normal adult live horses. The following structures were examined in detail: supraspinous ligament, lumbar and sacral spinous processes, thoracolumbar fascia and its caudal extension, tubera sacralia, ilial wings, dorsal and lateral portions of the dorsal sacroiliac ligaments, lateral part of the sacrum, and the lateral sacral crest. After ultrasonography, all animals were euthanized and detailed dissection of the lumbosacropelvic region was performed in six horses. Four lumbosacropelvic specimens were frozen and sectioned transversely for evaluation of cross-sectional anatomy. Gross anatomic findings were correlated with ante-mortem ultrasonographic images. On percutaneous ultrasonography, all horses had tubera sacralia with a mild-to-moderate roughened surface with occasional irregular hyperechoic mineralizations located within the apophyseal cartilage of younger horses. At the level of the tuber sacrale the caudal extension of the thoracolumbar fascia joined the dorsal portion of the dorsal sacroiliac ligament and assumed two different configurations relative to the dorsal portion of the dorsal sacroiliac ligament, with the predominant configuration of the thoracolumbar fascia located medial to the dorsal portion of the dorsal sacroiliac ligament. The less frequently encountered configuration had the thoracolumbar fascia positioned dorsal to the dorsal portion of the dorsal sacroiliac ligament. Caudal to the tuber sacrale the dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia consolidated to form a single, fused structure with a common insertion on the sacral spinous processes. A large variability in linear fiber pattern, echogenicity (small focal hypoechoic areas), ligament height, and cross-sectional measurements was identified in the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia of normal horses. Diagnosing mild-to-moderate desmitis of the fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia based solely on ultrasonography may therefore be difficult. To correlate ultrasonography with histology, samples of a fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia with bilateral hypoechoic lesions were submitted for histology and revealed diffuse mild-to-moderate loss of fiber density, multifocal fibrocyte degeneration, and cartilagenous metaplasia with multifocal, mild myofiber mineralization, which was compatible with age-related changes. As controls, sections of ultrasonographically normal fused dorsal portion of the dorsal sacroiliac ligament and thoracolumbar fascia from three horses demonstrated similar but milder histologic findings, which were considered normal.     

Dorsal spinous process impingement syndrome ('kissing spine') in a cat: imaging appearance and surgical management

Spinal pain is an important clinical presentation in feline patients, but the underlying causes can often be difficult to elucidate. Dorsal spinous process impingement syndrome ('kissing spine' or in human patients 'Baastrup syndrome') is a significant cause of spinal pain in equine and human patients and radiographically is characterised by a close approximation of adjacent spinous processes with reactive bone sclerosis affecting these spinous processes. In this report we describe the first reported case of dorsal spinous process impingement syndrome in a cat causing spinal pain, and successful surgical management of the syndrome. The affected cat presented at 5 years of age for evaluation of a 7-month history of progressive thoracolumbar pain. Radiographs revealed close approximation of the dorsal spinous processes of the seventh, eighth and ninth thoracic vertebrae (T7, T8 and T9), with associated reactive bone sclerosis. Surgical resection of the T8 dorsal spinous process resulted in complete resolution of the clinical signs with no evidence of recurrence 9 months after surgery.     

Effect of Application of Polyvinilidine Plates on the Dorsal Spinous Processes of Dogs

Anecdotal comments in the literature suggest that spinous fracture many weeks after application of polyvinilidine plates to the dorsal spinous processes of dogs may be due to associated adverse vascular changes. This study was undertaken to evaluate that hypothesis. Large size Lubra plates were cut to the appropriate length and applied to the dorsal spines of vertebrae L3 and L4. Vertebrae L2 and L5 served as operated controls. Vertebrae L1 and L6 served as unoperated normals. Two dogs were euthanized 1 week postoperatively, and three dogs each at 4, 8, and 12 weeks. The effect of the plate on the dorsal spinous processes was evaluated using microangiography and correlated histology. There was no apparent change in vascular architecture associated with plate application, nor with surgery alone, at any time interval. There did appear to be a time dependent loss of bone associated with plate application, indicating a change in the relative balance of osteoblastic and osteoclastic activity, and altered bone turnover.     

Impingement of the dorsal spinous processes in two hundred and fifteen horses: case selection, surgical technique and results

The surgical treatment of impingement of dorsal spinous processes (DSPs) at 2 equine veterinary hospitals following a similar diagnostic and surgical protocol is described with special reference to the diagnosis and case selection. The diagnosis was made from clinical examination and results of radiography and diagnostic analgesia of the affected sites. Scintigraphy was also used as an aid to diagnosis at one hospital. Surgical treatment was generally recommended when conservative treatment, which included 3-9 months rest, intralesional corticosteroids and physiotherapy, had failed. The DSPs were approached through a midline incision in the skin and supraspinous ligament. They were resected using an oscillating saw. Postoperatively, horses were returned to lungeing work after 2 weeks and riding commenced at 3 months, in most cases, and by 6 months in all successful cases. From one to 6 DSPs between thoracic vertebra (T) 11 and lumbar vertebra (L) 3 were resected in individual horses. T15, 16 and 17 were the spines most commonly treated. Long-term follow-up information was obtained in 209 horses. Seventy-two percent of these horses returned to full work and a further 9% improved sufficiently to be used for some athletic work.     

Effects of vertebral mobilization and manipulation on kinematics of the thoracolumbar region

OBJECTIVE: To measure passive spinal movements induced during dorsoventral mobilization and evaluate effects of induced pain and spinal manipulative therapy (SMT) on passive vertebral mobility in standing horses. ANIMALS: 10 healthy adult horses. PROCEDURES: Baseline vertical displacements, applied force, stiffness, and frequency of the oscillations were measured during dorsoventral spinal mobilization at 5 thoracolumbar intervertebral sites. As a model for back pain, fixation pins were temporarily implanted into the dorsal spinous processes of adjacent vertebrae at 2 of the intervertebral sites. Vertebral variables were recorded again after pin placement and treadmill locomotion. In a randomized crossover study, horses were allocated to control and treatment interventions, separated by a 7-day washout period.The SMT consisted of high-velocity, low-amplitude thrusts applied to the 3 non-pin-placement sites. Control horses received no treatment. RESULTS: The amplitudes of vertical displacement increased from cranial to caudal in the thoracolumbar portion of the vertebral column. Pin implantation caused no immediate changes at adjacent intervertebral sites, but treadmill exercise caused reductions in most variables. The SMT induced a 15% increase in displacement and a 20% increase in applied force, compared with control measurements. CONCLUSIONS AND CLINICAL RELEVANCE: The passive vertical mobility of the trunk varied from cranial to caudal. At most sites, SMT increased the amplitudes of dorsoventral displacement and applied force, indicative of increased vertebral flexibility and increased tolerance to pressure in the thoracolumbar portion of the vertebral column.     

Overriding vertebral spinous processes in the extinct horse, Equus occidentalis

Lumbar and thoracic vertebrae of the extinct horse, Equus occidentalis, were examined for gross and radiographic evidence of overriding spinous processes. Of 2,661 vertebrae examined, 580 had intact spinous processes. Thirty-six intact spinous processes, which appeared grossly similar to overriding spinous processes in the modern domestic horse, E caballus caballus, were radiographed. Of these 36 vertebrae, 2 had radiographic signs compatible with a radiographic diagnosis of overriding spinous processes, ie, radiographically observed lysis and/or sclerosis. Seemingly, weight bearing or other stresses imposed by human beings may not have induced the signs of overriding spinous processes.     

Thermography and ultrasonography in back pain diagnosis of equine athletes

The object of the current study was to evaluate the efficacy of thermography and ultrasonography in the diagnosis of thoracolumbar lesions in Quarter Horse athletes and associate the different types of lesions found with the athletic modality practiced. Twenty-four horses were admitted to the Surgery Service for Large Animals of the Veterinary and Animal Science Faculty, UNESP, Botucatu, Brazil, with complaints of back problems. All the horses were submitted for physical examinations to confirm the existence of thoracolumbar alterations and then for thermography and ultrasonography. Thermography was used to map the lesioned areas of this region and ultrasonography for lesion characterization. The lesions found were supraspinous desmitis, interspinous desmitis, dorsal intervertebral osteoarthritis, and impingement of the spinous processes or kissing spines. The existence of a relation between the type of event practiced by the horse and the type of lesion found was determined. In horses that competed in the barrel race, a predominance of lesions in the thoracic caudal, thoracolumbar, and cranial lumbar regions occurred, with intervertebral osteoarthritis and interspinous desmitis being the most common. In cutting horses, most of the lesions were observed in the caudal lumbar region, whereas horses competing in reining showed a preferential location for lesions in the middle lumbar, with a predominance of supraspinous desmitis and myositis. Thermography associated with ultrasonography was shown to be efficient in the diagnosis of the thoracolumbar lesions of these horses.     

Pressure algometry for the detection of induced back pain in horses: a preliminary study

REASONS FOR PERFORMING STUDY: Pressure algometry (PA) is a potential modality for objectively measuring mechanical nociceptive thresholds (MNTs) in horses. Its ability to differentiate musculoskeletal pain sites from nonpain sites is unknown and must be assessed prior to its clinical application. OBJECTIVES: To assess the ability of PA to detect induced musculoskeletal pain. METHODS: Twenty clinically normal mature horses (2 groups of 10 horses, over 2 years) were used to measure MNTs before and after implantation and removal of 2 fixation half-pins in the dorsal spinous processes of 2 adjacent vertebrae. To assess hyperalgesia, MNTs near the surgical sites were pooled and compared to surrounding landmarks. MNTs were also compared on 2 consecutive days immediately after surgical implantation. To assess longer-term adaptation or sensitisation, changes from the beginning to the end of the study were evaluated. RESULTS: The precise surgical sites could be recognised due to substantial and localised decreases in the MNTs compared with surrounding landmarks. At most sites distant to the surgical sites, the distribution of the median percentage change in MNTs was centred around 0 (suggesting unbiased repeatability). MNTs compared from the beginning to the end of this study did not demonstrate obvious adaptation or sensitisation. CONCLUSIONS AND POTENTIAL RELEVANCE: PA provides a quantitative and repeatable method for assessing the presence of musculoskeletal pain. Further studies are needed to evaluate PA clinically for assessing musculoskeletal injuries and pain management strategies in horses.     

Morphological variations of the infraorbital canal during CT has limited association with headshaking in horses

Headshaking is a common problem in horses. The etiology is unknown but thought to involve sensory input from branches of the trigeminal nerve, some of which are within the infraorbital canal. The objective of this retrospective cross‐sectional study was to describe the CT anatomy and variations of the infraorbital canal in horses with local disease processes and normal horses, and to examine associations between those findings and headshaking. Computed tomography scans were reviewed and morphological changes of the infraorbital canal were described. Presence of changes was then tested for association with headshaking prevalence, presence of disease processes in the region of the infraorbital canal, age, and sex. Nonparametric tests were used and a P‐value of .05 was considered significant. A total of 218 horses were included, 9% of which had headshaking and 45% had CT lesions in the region of the infraorbital canal. Morphological changes to the bone of the infraorbital canal were found in 121 horses (56%) and included the following: increased mineralization 39 (18%), decreased mineralization 89 (41%), deformed shape 51 (23%), displaced position 43 (20%), and disruption 11 (5%). All changes of the infraorbital canal significantly increased in frequency with the presence of adjacent disease. Increased mineralization and disruption of the infraorbital canal were significantly associated with headshaking in horses with adjacent disease; the latter only reached significance after exclusion of dentally immature horses. No other changes were significantly associated with the presence of headshaking. No association was found between headshaking and the age or sex of the horse.     

SCINTIGRAPHIC EVALUATION OF THE THORACIC SPINE IN THE ASYMPTOMATIC RIDING HORSE

Scintigraphic evaluation of the spinous processes of the equine spine has been done by subjective evaluation of radiotracer uptake in clinically abnormal horses. To determine the range of variation in asymptomatic riding horses, 33 normal horses were examined. Two 60 degrees oblique views of the thoracic and lumbar spine were evaluated subjectively, and a semi quantitative method based on standardized regions of interest in each spinous process in T10-L3 was also applied. A ratio between each spinous process and a reference area (Rib 15 or 16) was calculated. The effects of two different color displays and a smoothing filter were assessed. The results of the subjective evaluation was compared to the calculated ratios, and the associations between age, gender, weight, height, use and increased radiotracer uptake, and ratios were analyzed. No significant association was found between age, gender, weight, height, use and increased radiotracer uptake, or ratio. One or more areas of increased radiotracer uptake between T13 and T18 were common in the asymptomatic riding horse, which may have implications for the interpretation of clinical patients. The blue, green and red color display had a higher sensitivity for detecting increased radiotracer uptake compared to the continuous grayscale. The smoothing filter used in this study had no effect on the detection of areas with increased radiotracer uptake. The association between the results of the subjective evaluation and the semi quantitative method was apparent when analyzed in T13-17. To evaluate if the semi quantitative method can replace the subjective evaluation, studies on clinically affected horses are necessary.     

The cervical vertebral column of horses--a clinico-radiological study

For various anamnestic reasons the cervical vertebral column of 78 horses was examined radiologically. Statistical comparisons showed that male "warmbloods" were more frequently affected than was expected. Our horses were older than comparable animals in the international literature. Independently of their history the radiologic diagnosis of "cervical spondylarthrosis" was established in 56 horses. Arthrosis and other conditions were clinically manifested by spinal ataxia (44 horses) or mechanical impairment of the neck's mobility (21 horses). 10 of the arthrotic patients had synovial cysts causing compression of the spinal cord. 79 percent of all dorsal intervertebral arthrotic joints were found in the caudal column (C6/7 to C7/Th1). With 38 percent, C6/7 was the most frequently affected joint. Clinical and radiological findings could be compared with patho-anatomic results in 29 horses. The correlation was satisfactory.     

Relationship between spinal biomechanics and pathological changes in the equine thoracolumbar spine

The relationship between spinal biomechanics and pathological changes occurring in functionally normal equine thoracolumbar spines was studied in 23 horses. Ventrolateral vertebral body osteophytes occurred in 36 per cent of the spines. The majority occurred between the 10th and 17th thoracic vertebrae with the largest being found between the 11th and 13th thoracic vertebrae, the region of the thoracic spine where the greatest amount of lateral bending and axial rotation occurs. Impingement of the dorsal spinous processes was detected in 86 per cent of the spines with most lesions occurring between the 13th and 18th thoracic vertebrae. The severity of occurrence of impingement did not appear to be related to regional spinal mobility. Degeneration of intervertebral discs was observed in three of four specimens that were sectioned sagittally. It occurred in the first thoracic and the lumbosacral intervertebral discs and appeared to be related to the increased dorsoventral mobility and the increased disc thickness of these joints. The characteristic distribution of fractures of the thoracolumbar spine is discussed with respect to the biomechanics of the spine.