Basic three-dimensional kinematics of the vertebral column of horses trotting on a treadmill

OBJECTIVE: To determine movements of the vertebral column of horses during normal locomotion. ANIMALS: 5 young Dutch Warmblood horses that did not have signs of back problems or lameness. PROCEDURE: Kinematics of 8 vertebrae (T6, T10, T13, T17, L1, L3, L5, and S3) and both tuber coxae were determined, using bone-fixated markers. Measurements were recorded when the horses were trotting on a treadmill at a constant speed of 4.0 m/s. RESULTS: Flexion-extension and axial rotation were characterized by a double sinusoidal pattern of motion during 1 stride cycle, whereas lateral bending was characterized by 1 peak and 1 trough. Ranges of motion for all vertebrae were: flexion-extension, 2.8 degrees to 4.9 degrees; lateral bending, 1.9 degrees to 3.6 degrees; axial rotation, 4.6 to 5.8 degrees, except for T10 and T13, where the amount of axial rotation decreased to 3.1 degrees and 3.3 degrees, respectively. CONCLUSION AND CLINICAL RELEVANCE: During locomotion, 3 types of rotations are evident in the thoracolumbar vertebrae. Regional differences are observed in the shape and timing of the rotations. These differences are related to actions of the limbs. The method described here for direct measurement of vertebral column motion provides insights into the complex movements of the thoracolumbar portion of the vertebral column in trotting horses. Information on normal kinematics is a prerequisite for a better understanding of abnormal function of the vertebral column in horses.     

Basic three-dimensional kinematics of the vertebral column of horses walking on a treadmill

OBJECTIVE: To determine kinematic movements of the vertebral column of horses during normal locomotion. ANIMALS: 5 Dutch Warmblood horses without apparent lameness or problems associated with the vertebral column. PROCEDURE: Kinematics of 8 vertebrae (T6, T10, T13, T17, L1, L3, L5, and S3) and both tuber coxae were determined, using bone-fixated markers. Horses were recorded while walking on a treadmill at a constant speed of 1.6 m/s. RESULTS: Flexion-extension was characterized by 2 periods of extension and flexion during 1 stride cycle, whereas lateral bending and axial rotation were characterized by 1 peak and 1 trough. The range of motion for flexion-extension was fairly constant for vertebrae caudal to T10 (approximately 7 degrees). For lateral bending, the cranial thoracic vertebrae and segments in the pelvic region had the maximal amount of motion, with values of up to 5.6 degrees. For vertebrae between T17 and L5, the amount of lateral bending decreased to <4 degrees The amount of axial rotation increased gradually from 4 degrees for T6 to 13 degrees for the tuber coxae. CONCLUSIONS: This direct measurement method provides 3-dimensional kinematic data for flexion-extension, lateral bending, and axial rotation of the thoracolumbar portion of the vertebral column of horses walking on a treadmill. Regional differences were observed in the magnitude and pattern of the rotations. Understanding of the normal kinematics of the vertebral column in healthy horses is a prerequisite for a better understanding of abnormal function.     

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.     

Efficacy of tiludronate in the treatment of horses with signs of pain associated with osteoarthritic lesions of the thoracolumbar vertebral column

OBJECTIVE: To evaluate the efficacy of tiludronate for the treatment of horses with signs of pain associated with lesions of the thoracolumbar vertebral column. ANIMALS: 29 horses with clinical manifestations of pain associated with lesions of the thoracolumbar vertebral column and abnormal radiographic findings indicative of osteoarthritis of the articular processes-synovial intervertebral joints. PROCEDURES: Horses were initially examined in accordance with a standardized protocol, which included radiographic, ultrasonographic, and scintigraphic examinations. Fifteen horses were randomly assigned to receive tiludronate (1 mg/kg, IV, as a slow-rate infusion), and 14 horses received a control substance (day 0). Horses were monitored for the subsequent 120 days. Clinical evaluations were performed on days 60 and 120. Horses that had no evidence of clinical improvement on day 60 were administered tiludronate. Statistical analyses were performed to compare efficacy at day 60, improvement of dorsal flexibility at day 120, and dorsal flexibility before and 60 days after administration of tiludronate. RESULTS: Horses treated with tiludronate had significant improvement in dorsal flexibility between days 0 and 60, compared with control horses. Clinical improvement in dorsal flexibility was still evident at day 120. The percentage of positive responses was higher in the tiludronate group at 60 days. CONCLUSIONS AND CLINICAL RELEVANCE: Tiludronate had efficacy in the treatment of horses with signs of pain induced by osteoarticular lesions of the thoracolumbar vertebral column, causing a significant improvement in dorsal flexibility. Tiludronate may offer a treatment option for the management of horses with intervertebral lesions and the associated pain.     

Pathology of the vertebral column of horses with cervical static stenosis

Specimens of ligamentum flavum, joint capsule, and dorsal lamina were collected at surgery or necropsy from 25 horses with cervical static stenosis. All horses had myelographic evidence of dorsal compression of the spinal cord caused by soft tissue and/or bone in the caudal cervical area, primarily at C6-7. Most horses also had radiographic evidence of degenerative joint disease of articular facets. Histologically 19 horses had osteosclerosis and cartilage retention in the dorsal lamina, and 24 horses had increased fibrocartilage at the ligamentum flavum attachment to dorsal lamina. The ligamentum flavum and joint capsule had fibrovascular tissue in 20 horses. Fibrocartilaginous tissue, old hemorrhage, and fat necrosis were not unusual. One horse each had a synovial cyst, eosinophilic granulomas in the joint capsule, and osteochondrosis of articular facets. These findings indicate that abnormal biomechanical forces or instability of articulations result in stretching and tearing of the ligamentum flavum and joint capsule with subsequent fibrovascular and fibrocartilaginous proliferation, osteosclerosis of the dorsal lamina, and osteophyte formation on the articular facets.     

Implications of the neuroanatomy of the equine thoracolumbar vertebral column with regional anaesthesia and complications following desmotomy of the interspinous ligament

Impinging/overriding dorsal spinous processes (DSPs) of the thoracolumbar vertebrae are a common cause of poor performance in horses. In the last five decades, numerous surgical treatments have been reported on, from transverse transection of the affected DSPs, and endoscopic resection of the affected DSPs, to transection of the interspinous ligament. Until recently, cosmetic outcomes have been reported as good to excellent in studies. However, a previously unreported complication of neurogenic atrophy of the contralateral epaxial muscle following desmotomy of the interspinous ligament has been recently reported. The authors hypothesised that this was because of a more lateral approach than previously described, resulting in the scissors being too far across midline and transecting a nerve in the region. Considering this finding, we have reviewed the literature on the neuroanatomy of the thoracolumbar region in the horse. Literature on the neuroanatomy of the horse is lacking when compared with that of humans and companion animals, with most of the work extrapolated from companion animals. Based on the current literature, we hypothesise that transection of an intermediate branch of the dorsal spinal nerve supplying the m. longissimus is potentially the cause of the post-operative neurogenic atrophy. The lack of detailed knowledge of the neural anatomy of the equine back has resulted in the role of local anaesthesia in localising pain in the equine back being poorly understood. The wide variation in techniques used for localising back pain may explain why some horses suffering from poor performance or an abnormal gait because of back pain improve to local anaesthesia of the back while others do not. This review article highlights a lack of anatomical knowledge regarding the equine thoracolumbar region in the literature despite diagnostic local anaesthesia, medication, and surgery in this area being relatively common.     

Fractures and luxations of the vertebral column.

External fixation of the vertebral column is indicated to treat fractures of the caudal lumbar spine, open fractures where vertebral osteomyelitis is present or likely to occur, and vertebral fractures not easily stabilized by internal fixation alone (e.g., compression fractures, fractures including spinous processes, and articular facets). Advantages of external fixation of caudal lumbar fractures, especially in combination with dorsal fixation devices, include the following: Fracture fixation does not preclude dorsal decompression; fixation devices need not be applied directly to the fractured vertebrae; and the combined technique provides dorsal and ventral vertebral fixation, which is more stable than dorsal fixation alone. Although external fixation is not applicable to all vertebral fracture/luxations in small animals, it provides additional points of fixation for rigid stability. Animals with vertebral fracture/luxations treated with an external fixation device have tolerated the external portion well. Development of additional applications for this method of vertebral fracture repair seems warranted.     

Temporal and linear kinematics in elite and riding horses at the trot

Standard videography was used to determine the temporal and linear variables of 32 Spanish Purebreds at trot. Horses were organized into three groups: Group A (nonelite), comprising 13 stallions without any specific training program, which were hand led; Group B1 (elite), formed by 19 horses considered to be well-gaited and dressage trained, and which were also hand led; and Group B2 (ridden elite), comprising the same horses as the latter group but this time ridden. The horses ran at working trot, according to the trainers. Each animal was recorded using a Hi8 video camera. For temporal measurements, a 1/50 s time code was added to video images. Recordings were analyzed to provide times (seconds) at landing, mid-stance position, lift off and at subsequent landing in each limb. These data allowed the stride to be divided into its component phases by analysis of the variables for individual limbs, diagonal pairs and overall stride. The linear variables (meters) analyzed were stride length and overtracking, obtained for each stride from digitized images and calculated on a spreadsheet. Data were then compared between Groups A-B1 and Groups B1–B2.

Stride duration (0.639±0.064 vs 0.672±0.037 s) and stride length (247.7±21.9 vs 238.5±18.1 cm) of horses from A and B1 groups were similar; Group B1 was characterized by limb support and overlap values close to those of Group A; however, limb swing (forelimbs: 0.391±0.032 s; hind limbs: 0.374±0.027 s), diagonal swing (0.365±0.027 s) and inter-overlap (0.131±0.035) were of greater duration. Additionally, the proportion of horses with advanced placement was greater in Group B1.

Group B2 displayed greater stride duration (0.718± 0.054 s) and lower stride length (217.3±26.1 cm) than B1 group. The analysis revealed mounted horses to be characterized by limb and diagonal swings similar to those of Group B1; however, limb support and overlap were significantly greater, and inter-overlap and suspension phase were shorter.     

Stenosis of the thoracolumbar vertebral canal in a basset hound

A three-month-old female basset hound was referred to the Norwegian College of Veterinary Medicine with a history of progressive paresis of the pelvic limbs. Following neurological examination and the study of myelograms, extradural masses causing spinal cord compressions at the T₁₂.₁₃ and T₁₃-L₁ junctions were diagnosed. At necropsy bone-tissue of the vertebral laminae was found to have formed stenoses of the vertebral canal producing compressions of the spinal cord. Irreversible tissue-damage was observed in histological sections prepared from the compressed areas of the spinal cord.     

Repeatability of back kinematics in horses during treadmill locomotion

We tested the hypothesis that repeatability of a standardised protocol for quantifying back kinematics is sufficiently high not to prevent its use in the clinical evaluation of horses with back problems. We investigated the extent to which differences between laboratories may affect the results when a standardised protocol is used. As a clinical tool, movement analysis techniques are helpful for the objective and quantitative assessment of kinematics. Knowledge about the repeatability of the kinematic data is very important. The present study investigates the repeatability of back kinematics in 10 sound horses over 5 successive days and in 2 laboratories (5 horses at each location). Measurements were performed on the treadmill during the walk and the trot. The between-stride, between-day and between-horse repeatability were determined. A high degree of between-stride and between-day repeatability was observed in the spatiotemporal parameters and in the time-angle diagrams of thoracic and lumbar vertebrae, the sacrum and the hindlimb during both the walk and trot. Much more variability was found between horses, with the highest degree of dissimilarity in the lateral bending rotation of the L1 vertebra. For range of motion values, the between-day coefficient of variability was <14% and the between-horse coefficient of variability was up to 4 times higher. Small differences were found in range of motion values between the 2 laboratories. It is concluded that an analysis of back kinematics in the horse can provide highly repeatable data, warranting clinical use.     

Clinical progress in the diagnosis of thoracolumbar problems in horses

It is well known that a painful back can be responsible for loss of performance in horses. Veterinary examination of the sore back used to be limited to manual palpation with diagnosis confirmed empirically by response to treatment. Today, due to advances in imaging, there are multiple methods for evaluating the pathology of the horse's thoracolumbar (TL) spine. Radiography, ultrasonography, nuclear scintigraphy, thermography and algometry all play a part in developing a better understanding of equine TL problems. Despite this progress, definitive diagnosis can still be problematic. There is a lack of objectivity in understanding the implications of the pathology detected and its effect on the horse. It is difficult to determine the degree of pain experienced by individual horses and how that interferes with their performance and welfare. This paper emphasises the importance of a systematic clinical examination to identify the presence of pain that can be supported by recognition of pathology using a range of diagnostic aids. These will also be reviewed to assist the clinician in understanding the tools available to evaluate a horse with a sore back.     

Congenital abnormalities of the feline vertebral column.

Radiographs of vertebral segments from 200 cats were retrospectively assessed to determine the incidence of congenital axial skeletal abnormalities. The axial skeleton was divided into cervical, thoracic, lumbar, sacral, and caudal segments and the presence and types of congenital abnormalities present were recorded for each segment. A total of 598 axial skeletal segments were examined. Congenital abnormalities were found in 46 cats and involved 54 spinal segments. Block vertebrae were identified in three cats. No hemivertebrae or spina bifida were noted. Transitional abnormalities were most common, and were identified in 51 spinal segments. Abnormalities at the sacrocaudal junction were the most common of these; 19 examples were found. The second most common transitional abnormality was thoracicization of L1, with 18 such cats identified. Extra ribs on L1 were often smaller and fragmented and it may be possible for an inexperienced clinician to confuse these with rib fractures. The last rib(s) are also often used for anatomic localization of surgical procedures; the presence of a transitional lumbar vertebra with one or two extra ribs introduces the possibility of error or confusion about choice of surgical site.     

Fractures of the cervical vertebral odontoid in four horses and one pony

Four horses and one pony, ranging in age from one to 11 years, were diagnosed with two different types of odontoid peg fractures. Their clinical signs included reluctance to move the neck and head, dullness, and abnormalities of gait. Radiography was essential for the diagnosis, and the method of treatment varied depending on the severity of the neurological signs, the intended use of the horse, and financial constraints. Optimal treatment requires a technique that allows decompression, anatomical alignment, and stabilisation of the odontoid fracture. If the clinical (neurological) signs are not too severe and the animal shows signs of feeling peripheral pain, conservative treatment can be applied, as is common practice in human surgery. All except the pony made a full recovery.     

The effect of induced hindlimb lameness on thoracolumbar kinematics during treadmill locomotion

REASON FOR PERFORMING STUDY: There are no detailed studies describing a relationship between hindlimb lameness and altered motion of the back. OBJECTIVES: To quantify the effect of induced subtle hindlimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses were measured during walk and trot on a treadmill before and during application of pressure on the sole of the left hindlimb using a well-established sole pressure model. Reflective markers were located at anatomical landmarks on the limbs, back, head and neck for kinematic recordings. Ground reaction forces (GRF) in individual limbs were calculated from kinematics to detect changes in loading of the limbs. RESULTS: When pressure on the sole of the hindlimb was present, horses were judged as lame (grade 2 on the AAEP scale 1-5) by an experienced clinician. No significant unloading of this limb was found in the group of horses (unloading was observed in 4 animals, but was not detectable in the other 2), but statistically significant effects on back kinematics were detected. The overall flexion-extension (FE) range of motion (ROM) of the vertebral column was increased at walk, especially in the thoracic segments. Axial rotation (AR) ROM of the pelvis was also increased. At trot, the FE ROM was decreased only in the segment L3-L5-S3. During the stance phase of the lame limb, the segment T6-T10-T13 was more flexed and the neck was lowered at both gaits; the thoracolumbar segments were more extended at walk and trot. There were no significant changes in the stride length or protraction-retraction angles in any of the limbs. CONCLUSIONS: Subtle hindlimb lameness provoked slight but detectable changes in thoracolumbar kinematics. The subtle lameness induced in this study resulted in hyperextension and increased ROM of the thoracolumbar back, but also in decreased ROM of the lumbosacral segment and rotational motion changes of the pelvis. POTENTIAL RELEVANCE: Even subtle lameness can result in changes in back kinematics, which emphasises the intricate link between limb function and thoracolumbar motion. It may be surmised that, when chronically present, subtle lameness induces back dysfunction.     

The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion

REASONS FOR PERFORMING STUDY: Lameness has often been suggested to result in altered movement of the back, but there are no detailed studies describing such a relationship in quantitative terms. OBJECTIVES: To quantify the effect of induced subtle forelimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses was measured at walk and at trot on a treadmill before and after the induction of reversible forelimb lameness grade 2 (AAEP scale 1-5). Ground reaction forces (GRF) for individual limbs were calculated from kinematics. RESULTS: The horses significantly unloaded the painful limb by 11.5% at trot, while unloading at walk was not significant. The overall flexion-extension range of back motion decreased on average by 0.2 degrees at walk and increased by 3.3 degrees at trot (P<0.05). Changes in angular motion patterns of vertebral joints were noted only at trot, with an increase in flexion of 0.9 degrees at T10 (i.e. angle between T6, T10 and T13) during the stance phase of the sound diagonal and an increase in extension of the thoracolumbar area during stance of the lame diagonal (0.7degrees at T13, 0.8 degres at T17, 0.5 degres at L1, 0.4 degrees at L3 and 0.3 degrees at L5) (P<0.05). Lameness further caused a lateral bending of the cranial thoracic vertebral column towards the lame side (1.3 degrees at T10 and 0.9 degrees at T13) (P<0.05) during stance of the lame diagonal. CONCLUSIONS: Both range of motion and vertebral angular motion patterns are affected by subtle forelimb lameness. At walk, the effect is minimal, at trot the horses increased the vertebral range of motion and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes, presumably in an attempt to move the centre of gravity away from the lame side and reduce the force on the affected limb. POTENTIAL RELEVANCE: Subtle forelimb lameness affects thoracolumbar kinematics. Future studies should aim at elucidating whether the altered movement patterns lead to back and/or neck dysfunction in the case of chronic lameness.