Osteochondrosis of the occipital condyles and atlanto-occipital dysplasia in a Belgian horse

A lesion in the cervical region of a 14-month-old Belgian gelding with severe ataxia was suspected. Necropsy revealed symmetric focal cartilage defects compatible with osteochondrosis of the occipital condyles and atlanto-occipital dysplasia. To our knowledge this is the first equine report of symmetrical osteochondrosis of the occipital condyles causing neurologic signs.     

Osteochondrosis — An international problem for the horse industry

Osteochondrosis is one of the most important skeletalproblems affecting young horses and is one of the conditions included in the syndrome of developmental orthopedic disease. It occurs worldwide in many different breeds and its incidence appears to be steadily increasing. The primary lesion of osteochondrosis is attributed to focal damage of endochondral ossification. When occurring in the articular/epiphyseal cartilage complex, there may be bone formation within the retained cartilage, resulting in “bony fragments.” These are often seen in the tarsocrural articulation on the cranial aspect of the tibia. Focal retention of necrotic cartilage into the subchondral bone may eventually lead to cleft formation resulting in osteochondrosis dissecans. Other lesions associated with osteochondrosis are subchondral cysts, fractures and osteoarthrosis.The definitive cause of osteochondrosis is unknown,but there is evidence that it is the response in growth cartilage to a number of different challenges. It appears to be multifactorial in origin, involving heredity, growth rate, body size, nutrition, mineral imbalance, endocrinological dysfunction and biomechanical trauma. Recent studies have shown cases of osteochondrosis to be preceded by radiographically detectable disturbances of endochondral ossification during the first three months of life. This early appearance of disturbed ossification necessitates further studies into the importance of nutrition/management of the pregnant and lactating mare. Whether these early disturbances will lead to fully developed osteochondrosis or if they will recede obviously depends on a number of factors such as nutrition and exercise. High energy diets have been shown in weaning foals to consistently produce lesions of osteochondrosis. If, however, foals fed a high energy diet are subjected to forced exercise, the incidence of osteochondrosis is reduced dramatically.The prevention of osteochondrosis must rate as a highpriority for the horse industry, but to achieve this more data on the mechanisms of endochondral ossification and how this process is influenced by different intrinsic and environmental factors are required. Recent research into osteochondrosis has involved studies of chondrocyte metabolism in growth cartilage, the influence of growth factors, the extent of degradation of extracellular matrix and endochondral ossification.     

An undifferentiated sarcoma in the cervical region in a horse

An Italian Saddle Horse mare was admitted for a hard, nonpainful mass localised in the cervical region. Clinical and diagnostic investigations were performed, which were suggestive of a multilobulated ossifying mass of neoplastic origin. Due to poor prognosis the horse was subjected to euthanasia. Post mortem computed tomography, anatomopathological examination and immunohistochemistry were used to make a definitive diagnosis of undifferentiated sarcoma in the cervical region.     

Diverticulum and fistula of the lower cervical esophagus in a horse

Esophageal diverticulum and perforation were diagnosed in a horse. The condition was characterized clinically by dysphagia, polypnea, diffuse swelling of the ventral aspect of neck and cutaneous fistula. Endoscopic examination revealed the presence of food material in the guttural pouch. A barium sulfate esophagram was performed to outline the diverticulum.

Exploratory surgery confirmed esophageal perforation and entrapment of food material between the muscular planes of the cervical region and the horse was euthanized. At necropsy a food-filled periesophageal tract was found extending from the esophageal rupture to the left guttural pouch.

     

Kinematics of the cervical spine of the adult horse

At least three types of movement, dorsoventral flexion and extension, axial rotation and lateral bending, were shown to occur at each of the intervertebral joints in the cervical spine. Between the first two cervical vertebrae the mean axial rotation was 107.5 degrees, which was 73 per cent of the total axial rotation of the cervical spine. The atlantooccipital joint rotated through a mean of 27 degrees, whereas the remaining cervical joints each had less than 3 degrees of rotatory movement. Dorsoventral flexion and extension were maximal at the atlantooccipital joint, which had an amplitude of 86.4 degrees and accounted for 32 per cent of the total dorsoventral movement of the cervical spine. Lateral bending was relatively more uniform along the length of the neck, with mean values ranging from 25 to 45 degrees for each joint except that between the first two cervical vertebrae, which had a mean of only 3.9 degrees of lateral bending.     

Treatment of a metallic foreign body in the cranial cervical region of a horse

Ingestion of foreign bodies is uncommon in horses when compared with indiscriminate grazers such as cattle. This case report describes the diagnosis and treatment of a cervical abscess in a Thoroughbred racehorse thought to be associated with ingestion of wire. Radiographic and ultrasonographic examination provided a diagnosis, and conservative treatment of the lesion with antimicrobials initially allowed the lesion to localise closer to the skin for safer surgical exploration. Intra-operative ultrasonographic imaging facilitated surgical access, removal of the foreign body, and drainage. While surgical treatment is usually necessary to resolve an abscess, initially conservative therapy may help to improve the prognosis by simplifying surgical access and reducing the risk of surgical complications.     

Surgical repair of a cervical fracture/dislocation in a mature horse

The treatment of a cervical fracture/dislocation in an 11-year-old Anglo-Arab gelding is described. Six months after surgical repair of a luxation of the second left true intervertebral joint the animal appeared clinically normal.     

An investigation of the second heart sound in the normal horse

The second heart sound was evaluated in conscious, normal horses using intracardiac and external sound detection devices and echocardiography. The second heart sound (S2) in the normal horse is single or split by a narrow interval, not usually detected by external phonocardiographic evaluation. Splitting of S2 was classified as normal (aortic [A2] preceding pulmonic [P2] components) in 66.7 per cent and reversed (P2 preceding A2) in 33.3 per cent of the horses studied. Normal splitting appears to result from lower impedance of the pulmonary vasculature delaying the onset of P2. Reverse splitting appears to result from a delay in A2 resulting from prolongation of PEP and LVET. There does not appear to be variation in splitting of S2 due to respiration based on the cases in which this was measured.     

Endoscopic anatomy of the cervical vertebral canal in the horse: a cadaver study

Reason for performing study: Localisation of spinal cord compression in horses with cervical vertebral stenotic myelopathy is inexact. Vertebral canal endoscopy has been used in man to localise spinal cord lesions and has the potential to become a useful diagnostic technique in horses. Objective: To establish a surgical approach via the atlanto‐occipital space to the cervical vertebral canal in equine cadavers and describe the endoscopic anatomy of the cervical epidural and subarachnoid spaces. Methods: The cadavers of 25 mature horses were used to assess 3 surgical methods to approach the cervical vertebral canal, including 2 minimally invasive and one open technique. Once the approach had been made, a flexible videoendoscope was inserted into the epidural space (epiduroscopy) or the subarachnoid space (myeloscopy) and advanced caudally until the intervertebral space between C7 and T1 was reached. Results: The epidural and subarachnoid spaces could not be accessed reliably using the minimally invasive techniques. Furthermore, damage to the nervous tissues was a frequent complication with these procedures. The open approach allowed successful insertion of the videoendoscope into the epidural and subarachnoid spaces in all horses and no inadvertent damage was observed. Anatomical structures that could be seen in the epidural space included the dura mater, nerve roots, fat and the ventral internal vertebral venous plexus. In the subarachnoid space, the spinal cord, nerve roots, blood vessels, denticulate ligaments and external branch of the accessory nerve were seen. Conclusions: Using the open approach, epiduroscopy and myeloscopy over the entire length of the cervical vertebral canal are possible in the mature horse. Potential relevance: Cervical vertebral canal endoscopy may become a valuable tool to localise the site of spinal cord injury in horses with cervical vertebral stenotic myelopathy and could aid in the diagnosis of other diseases of the cervical spinal cord.     

Treatment of a second carpal bone fracture by removal under ultrasonographic guidance in a horse

OBJECTIVE: To report an unusual 2nd carpal bone (C2) slab fracture and its treatment, using an ultrasonographically assisted, minimally invasive arthrotomy technique, for fragment removal. STUDY DESIGN: Case report. ANIMALS: An 11-year-old crossbred Warmblood gelding. METHODS: A bone fragment, spanning the height of C2, identified on the palmaromedial aspect of C2 was demarcated intraoperatively using ultrasonographically guided needles and removed by arthrotomy. RESULTS: Fracture fragment removal was achieved using a small, ultrasonographically guided arthrotomy. The horse has become sound after treatment and returned to the previous level of pleasure riding activity. CONCLUSIONS: Perioperative ultrasonography was used to delineate and facilitate removal of an unusual slab fragment of C2, through a minimally sized arthrotomy. Despite the presence of pancarpal osteoarthritis and partial involvement of the medial collateral ligament, the prognosis appeared to be satisfactory for this pleasure riding horse. CLINICAL RELEVANCE: Ultrasonographic guidance may be used to optimize the approach to C2 articular bony fragments that may not be observed using arthroscopy.     

Cervical vertebral canal endoscopy in a horse with cervical vertebral stenotic myelopathy

A 3-year-old Thoroughbred gelding presented with a history of neurological signs, including incoordination in his hindlimbs, of about 7 months' duration. On initial examination, the horse exhibited ataxia and paresis in all limbs with more severe deficits in the hindlimbs. Cervical radiographs displayed severe osteoarthritis of the articular processes between C5 and C6. On subsequent cervical myelography the dorsal contrast column was reduced by 90% at the level of the intervertebral space between C5 and C6. Cervical vertebral canal endoscopy, including epidural (epiduroscopy) and subarachnoid endoscopy (myeloscopy), was performed under general anaesthesia. A substantial narrowing of the subarachnoid space at the level between C6 and C7 was seen during myeloscopy, while no compression was apparent between C5 and C6. Epiduroscopy showed no abnormalities. After completion of the procedure, the horse was subjected to euthanasia and the cervical spinal cord submitted for histopathological examination. Severe myelin and axon degeneration of the white matter was diagnosed at the level of the intervertebral space between C6 and C7, with Wallerian degeneration cranially and caudally, indicating chronic spinal cord compression at this site. Myeloscopy was successfully used to identify the site of spinal cord compression in a horse with cervical vertebral stenotic myelopathy, while myelography results were misleading.     

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.     

Lag screw fixation of avulsion fractures of the second phalanx in the horse.

Avulsion fractures of the posteromedial eminence of the 2nd phalanx were repaired, using an ASIF cortex screw in 3 reining Quarter Horses. Within 9 and 11 months, respectively, 2 horses were sound and back in competition as reining horses. The other horse was sound for pleasure class showing at 7 months after surgery.