0. While the equine hip is a rare site of lameness, and pelvic problems are usually fractures which are generally straightforward to diagnose, conditions of the thoracolumbar vertebrae cause discomfort which may be subtle and only manifest at ridden exercise. The often vague clinical signs and the volume of the musculature surrounding the thoracolumbar region combine to make diagnosis of thoracolumbar diseases more challenging than those affecting the rest of the axial skeleton. In particular, only a minority of horses presented as having “back pain” will in fact have pain originating from the thoracolumbar region, with lameness and behavioural issues much more common. These difficulties in defining, investigating and treating the horse with “back pain” has resulted in more unconventional treatments being used to treat this syndrome than in any other realm of equine medicine. However, best results are achieved by adopting a consistent and evidence-based approach to diagnosis and treatment. 

0. Osteoarthritis of the coxofemoral joint is a rare cause of lameness in the horse and is usually secondary to trauma. Confirmation of this diagnosis would require a positive intraarticular block (possible, but not easy) and radiographic evidence of periarticular bone remodelling and/or acetabular rim fragments. Standing radiographs are possible but often general anaesthesia is required for diagnostic quality images.

   Hip luxation is also rare. Trauma is the cause. The hip is usually displaced craniodorsally. Limb is shortened and held in an outwardly rotated position. Greater trochanter is very prominent and crepitus may be palpable. Can distinguish from fractured pelvis by rectal examination.

   Closed reduction can occasionally work in the acute case. Open reduction and excision arthroplasty has been reported as a salvage procedure in ponies or small horses. Prognosis is very poor. 

Fractures of the pelvis are regularly encountered in racehorse practice (several are seen here annually here at the R(D)SVS Equine Hospital) and result from trauma. The most common sites are the ilial wing or shaft (see Figure 1). Ilial wing fractures may be caused by a one-off incident, or result from stress remodelling in horses working at high speeds (stress fracture). Tuber coxae fractures are usually due to hitting a fence post or stable door. Tuber ischium fractures result from kick injuries or falling backwards, while other fractures are usually the result of a bad fall. 

 Usually a single traumatic incident, but stress fractures of the ilial wing may have a history of recurrent and transient hindlimb lameness following fast work.

These depend on site of fracture (e.g. involvement of acetabulum) and degree of fragment displacement, and vary from moderate uni- or bi-lateral hindlimb lameness to severe lameness or inability to rise, with obvious crepitus. Asymmetry of the tubera sacrale or coxae may be present, and will be permanent. Some cases may appear ataxic but have no neurological abnormalities when assessed. Chronic cases invariably have marked muscle wastage, most prominent in the gluteal region. A rare complication is damage to iliac arteries caused by displaced bone fragments. 

•   Rectal palpation for pain, haematoma, displacement (not all of pelvis accessible)

•   Scintigraphy and ultrasonography are now the imaging modalities of choice for pelvic

  fractures.

•   Radiography rarely performed as general anaesthesia is required for good quality

  images, and recovery from anaesthesia may further displace a fracture. Standing radiography has been described, but requires specialised equipment and image quality is often poor. 

0. Fragments of tuber ischii or tuber coxae may be surgically removed. For most other pelvic fractures, prolonged rest is the only treatment. Euthanasia is indicated where lameness persists or the horse remains recumbent.
   
   

   Prognosis.

   Fracture of tuber coxae & ischii and non-displaced ilial wing fractures = good. Fractures of ilial shaft, pubis or involving acetabulum = poor. 

1. Diagnosis of the equine “back case”
The diagnosis is made following a detailed and exhaustive clinical examination, the main purpose of which is to detect other conditions that may be the cause of the reported clinical signs. The history is often lengthy and complicated, but may give valuable clues about the aetiology of the problem (e.g. horse recently changed owners or increased level of exercise). A full orthopaedic examination should be performed.
If the signs are evident only during riding, the horse should be observed with the regular rider, although if the history includes unseating the rider, there are clear safety considerations. In addition to direct palpation of the soft tissue structures of the back, the hypaxial muscles should be palpated per rectum. Levels of the enzymes CK and AST can be measured following a period of strenuous exercise to detect exertional rhabdomyolysis (see Medicine lectures). Other sources of pain can produce similar signs, so check saddle fit, teeth, bridle / bit. Palpation of the back to assess the degree of flexion and extension is an important test of whether back pain is present. NORMAL HORSES WILL SHOW REFLEX BACK MOVEMENTS IN RESPONSE TO STIMULATION, although to the lay person these responses can appear to confirm severe pain.

A useful diagnostic test is to place the horse on a course of phenylbutazone and monitor the response, if any, when ridden. No improvement during medication suggests that the problems are not due to pain, although a painful incident may have triggered the now-established behaviour.

If it has been established that the horse does have “back pain”, then diagnostic imaging is used to localise the pain. Radiography and scintigraphy are established techniques. Thermography and ultrasonography are more controversial diagnostic tools. 

Excessive curvature of the thoracolumbar spine can be ventral (lordosis), dorsal (kyphosis) or lateral (scoliosis). Most of these deviations are mild and clinically insignificant. Severe congenital, or developmental, deviations of the spine are rare but when present can interfere with the athletic use of the animal. As there is no firm evidence that horses with mild conformational abnormalities of the back are more likely to develop back pain, these animals should be managed as normal. The inheritance of these anomalies is unknown. 

Soft Tissue Lesions of the Thoracolumbar Vertebral Column

The soft tissues of the thoracolumbar and sacral regions include the muscles (epaxial and hypaxial), the ligaments interconnecting the vertebrae and those attaching the vertebral column to the hindlimbs at the sacroiliac joint. Acute soft tissues injuries occur either as a consequence of repeated low-grade trauma, or in a single acute incident such as a fall. Clinical signs of thoracolumbar discomfort (“back pain”) in the horse are notoriously varied and can often be attributed to pain elsewhere or equitation problems. Horses with back pain due to soft tissue lesions may have concomitant uni- or bilateral hindlimb lameness (raising the question which of the two conditions came first), shortened stride length affecting the hindlimbs, poor performance and deterioration in temperament or other behavioural signs such as bucking when ridden. Often, veterinary attention is only sought at a late stage in the condition, by which time localised swelling and pain on application of pressure are only rarely evident. There may be palpable focal enlargement of the supraspinous ligament; the other ligaments can only be examined by ultrasound. 

Clinical signs in horses confirmed as having pain in the sacroiliac joint region in a recent report were varied and included poor or asymmetric muscling, either reduced or increased movement of the thoracolumbar spine and gait abnormalities which usually worsen when ridden. Asymmetric tuber sacrale are frequently encountered as an incidental finding and, contrary to previous reports, are unusual in horses with confirmed sacroiliac regional pain. 

If the damaged ligament or muscle can be accurately located then targeted treatment is possible. Steroids and irritants have been injected directly into ligaments and reported to be of use. Ultrasound can be used to monitor healing (reduction in diameter, return of fibres to normal alignment). With any significant lesion of a ligament or insertion, prolonged rest is essential. 

Impingement of Dorsal Spinous Processes

Also known as “kissing spines” and “overriding dorsal spinous processes”, this is one of the most common conditions known to cause thoracolumbar pain in horses. The spaces between the dorsal spinous processes in the mid-thoracic or, less commonly, the lumbar vertebral column narrow dorsally and the opposing bone surfaces remodel. Affected horses usually resent flexion or extension of the back when manipulated. Radiography will confirm the impingement but not whether the “kissing spines” are actually causing pain. As many normal horses (around 60% of all middle-aged Thoroughbreds, for example) have narrowed inter-spinous process spaces a positive response to local anaesthesia is required for confirmation of the diagnosis. Many horses will recover with rest. Local injections of steroid or surgical removal of impinging processes are used as treatments. Surgical treatment resulted in the return of around 80% of treated horses to their previous level of work, after conservative treatment had failed. 

A novel surgical treatment for impingement of dorsal spinous processes has recently been described. This treatment is less invasive than removal of the impinging processes, and involves cutting of the interspinous ligament through small incisions. It is hoped that this will result in resolution of pain with a faster return to normal exercise than with removal of the spinous processes. However there is only preliminary data available, and the case numbers are not sufficient for a full appraisal of the efficacy to be made. The paper is referenced at the end of these lecture notes. 

is often encountered as an incidental finding when radiographing the soft

tissues of the thorax in adult horses. Considerable amounts of bone form on the ventral surface of the thoracolumbar vertebral bodies, but it is unclear whether this is a source of pain. 

 of the thoracic, lumbar and sacral vertebrae vary in degree of displacement and amount of pressure exerted on the spinal cord. Signs therefore vary from mild discomfort to recumbency and may include a range of neurological signs. 

affects the dorsal articulations. Disc prolapse is virtually unknown in the horse