Equis ISSN 2398-2977
Musculoskeletal: back pain
Synonym(s): Equine back pain
Contributor(s): Graham Munroe, Vetstream Ltd, Chris Whitton
Print off the Owner factsheets on Exercise intolerance / poor performance testing and Fitting a saddle - why it's so important to give to your clients.
- Cause: common problem, especially in ridden performance horses where presenting complaint is poor performance or alteration in gait; difficult to definitively diagnose and in some cases treat; may present as a primary back problem, involving bony and/or soft tissue structures or more commonly as a secondary problem related to lameness elsewhere, especially in the hindlimbs. Easily confused, and sometimes coincidental with neck and pelvic problems, faulty tack or riding issues, and poor behavior or schooling.
- Signs: range of possible signs which may vary between individuals and some of which are quite subtle, localization to a specific area of pathology which is painful can be difficult; the whole animal should be carefully evaluated for other causes of lameness and poor performance followed by a methodical workup of the back consisting of a visual inspection, palpation and manipulation of the thoracolumbar spine, and a full lameness evaluation at exercise, including when ridden.
- Diagnosis: digital radiography, scintigraphy and ultrasound of the back have improved diagnosis, but imaging techniques are not always diagnostic as to the source of pain in an individual animal. However, local anesthetic infiltration techniques may assist in localizing this.
- Treatment: correction of tack or riding habits, rest, medical therapy, physiotherapy, manipulation, surgery.
- Prognosis: guarded to poor depending on the specific cause.
- Vary with the type of pathology causing the back pain and in many cases multifactorial influences may lead to the individual incidences.
- Faulty tack.
- Poor riding.
- Abnormal back conformation.
- Direct trauma from a fall, road traffic accident.
- Overuse injuries due to repetitive 'wear and tear' exercise or 'one off' acute exercise movements.
- Unusually either infection or neoplasia.
- There may be some hereditary factors in certain pathologies.
- Ridden animals have a higher incidence of back pathology but driven horses and unbroken animals can still develop back problems.
- Performance athletic animals have a higher incidence of pathology.
- Abnormal back conformation may predispose to an increased incidence of back pain.
- Poor riding.
- Faulty or poorly fitting tack.
- Exercise regimens; see individual back pathologies.
- Primary congenital back abnormalities.
- See specific conditions causing back pain.
- There is considerable variation among individuals as to their perception and manifestation of back pathology and pain. This means that there is often a poor correlation between the clinical signs of back pain and severity of pathology as manifested on diagnostic imaging modalities.
- See Spine: fractures Spine: fracture .
- Fracture of dorsal spinous processes of cranial thoracic spine T3-10 (withers):
- Cause: trauma, rearing and falling backwards.
- Signs: young animals, local pain, swelling, heat, neck and forelimb stiffness, later depression and deviation in the withers, crepitus.
- Diagnosis: lateral radiography of affected area.
- Treatment: 6 weeks initial rest, NSAIDs, physiotherapy, refit saddle and/or pads. Surgical removal of infected fragments.
- Prognosis: good, fibrous union usually develops, complete recovery in 3-6 months.
- Fracture of single thoracic dorsal spinous process:
- Cause: uncommon condition but post-direct trauma.
- Signs: local pain, heat, swelling in acute cases; less obvious signs in chronic cases; difficult to distinguish from musculoligamentous pathology.
- Diagnosis: palpation, radiography, scintigraphy Bone: scintigraphy .
- Treatment: similar to fractured withers (as above).
- Fracture of neural arch, vertebral body :
- Cause: severe trauma, eg high speed falls or collisions.
- Signs: depends type of fracture; extensive comminuted fracture with displacement leads to severe damage to the spinal cord and neurological deficits; crush-type or incomplete vertebral body fractures can have minimal damage to the spinal cord and can present with severe back pain or minor local neurological signs and epiaxial muscle wastage; thoracolumbar fractures typically involve T9-T16, particularly T12 (usually compression fractures), or T18-L6 (usually comminuted).
- Diagnosis: radiography may define some lesions, scintigraphy is helpful in chronic non-displaced cases.
- Treatment: euthanasia if severe neurological signs, aggressive anti-inflammatory therapy and strict box rest if no neurological signs.
- Prognosis: guarded to grave.
- Vertebral laminar stress fractures:
- Cause: inadequate bone modeling in respone to training regimen, cranial aspect of vertebrae near articular facet in thoracolumbar junction and cranial lumbar vertebrae.
- Signs: young Thoroughbred Thoroughbred racehorses, clinical back pain, loss of performance.
- Diagnosis: scintigraphy, radiography, ultrasonography.
- Treatment: rest, then reduced plane of exercise.
- Prognosis: good.
- Overriding dorsal spinous processes Spine: spinous processes - overriding :
- Cause: decreased interspinous gap or overlapping processes, common radiographically but many cases are asymptomatic, possibly more common in Thoroughbreds Thoroughbred , ?jumping horses more common, conformation (short back or abnormal dorsal spinous process shape and size). T13-18 most commonly affected. Three age groups affected but most commonly 6-9 year old horses.
- Signs: present with a whole range of back pain signs from acute severe to low grade and insidious, stiffness, poor performance, temperament change, resentment of saddling, girth tightening, mounting; pain on palpation; muscle wastage of longissimus dorsi ; improves with rest, but returns on exercise. Often other problems coincidentally such as hindlimb lameness.
- Diagnosis: back palpation, radiography; local infiltration anesthesia, gamma scintigraphy Bone: scintigraphy .
- Treatment: rest, NSAIDs Therapeutics: anti-inflammatory drugs , physiotherapy Musculoskeletal: physiotherapy , interspinous injection of corticosteroids, surgery (resection of processes or interspinous desmotomy Spine: interspinous ligament - desmotomy ), acupuncture Acupuncture: overview , shockwave therapy Extracorporeal shockwave therapy .
- Spondylosis deformans:
- Cause: remodeling and bony formation on ventral, ventrolateral and lateral vertebral body. Usually T9-15 and several locations. Many lesions are incidental and asymptomatic.
- Signs: general signs of back pain, older horses, often other concurrent back pathology.
- Diagnosis: radiography , may be incidental finding, scintigraphy.
- Treatment: no specific treatment
- Prognosis: poor if secondary to trauma.
- Osteoarthritis of the vertebral articular facet joints Musculoskeletal: osteoarthritis (joint disease) :
- Cause: wear and tear trauma, often worse in cases with concurrent overlapping dorsal processes and other back pathology - possible change in movement of joints, usually worse T15-L1, cranial and caudal process, bilateral lesions are most common, middle to old aged animals.
- Signs: may be incidental finding but presentation often complicated by other back pathology - mild to moderate chronic back pain and/or poor performance.
- Diagnosis: high definition gamma scintigraphy under GA, or using motion correction software for dynamic image . Radiography with special ventrolateral 20° oblique views - interpretation of lesions can be difficult as high incidence of pathology which may be incidental. Ultrasonography of facet joints will allow periarticular pathology to be identified and allow ultrasound-guided intra/periarticular medications to be placed.
- Treatment: rest and controlled exercise, systemic NSAIDs, physiotherapy, specific articulations i/a corticosteroids under US control. Other therapies suggested but with little evidence base for their effectiveness include perilesional sarapin, intravenous tiludronate Tiludronate , mesotherapy.
- Sacroiliac damage Pelvis: trauma - sacroiliac :
- Cause: congenital or traumatic cause → prolonged mild instability → chronic damage in competitive horses → remodeling → enlargement and unevenness of joints (not spur formations); up to 15% of back disorders.
- Signs: chronic reduced or poor performance (riding horses at slow speed; racing horses at racing pace); unilateral hindlimb lameness usually (not always) corresponding with side of lesion; maybe bilateral lameness or gait change; not progressive.
- Diagnosis: gamma scintigraphy Bone: scintigraphy , periarticular local analgesia, ultrasonography Ultrasonography: bone / joints Ultrasonography: musculoskeletal .
- Treatment: difficult; rest, short-term systemic anti-inflammatories, periarticular corticosteroids, graduated exercise regimens to improve muscle tone and fitness of quarters and back and maintain fitness, physiotherapy techniques to remove muscle spasm in acute cases and improve stability of articulation in longer term.
- Prognosis: guarded to poor.
Soft tissue injuries
- Muscle strain of longissimus dorsi and/or sublumbar muscles:
- Cause: trauma from saddle and/or rider, slip, fall, poor jump; fatigue, lack of fitness may predispose; chronic cases common secondary to bony back pathology or concurrent fore/hind limb lameness.
- Signs: sudden loss of performance, muscle soreness/guarding, swelling in more severe cases where ther is tearing and hematoma, fibrotic scars in chronic cases with muscle atrophy, no dorsal midline pain, stiffness and decreased flexibility in chronic cases.
- Diagnosis: biochemistry - elevated muscle enzymes (acute), Faradic stimulation, ultrasonography of the muscles dorsally.
- Treatment: rest, NSAIDs, physiotherapy Musculoskeletal: physiotherapy , controlled exercise and flexibility regimens, check saddle fit, cold therapy in acute damage.
- Supraspinous ligament desmitis:
- Cause: unknown; abnormal tensile or direct compressive forces, or secondary to other back pathology including overlapping DSPs. Uncommon, but usually high level athletic horses.
- Signs: acute cases often sudden change in performance when ridden and focal swelling and pain in dorsal midline, especially T15-18; chronic cases less localizing signs with chronic back pain presentation.
- Congenital malformation.
- Contracted foal syndrome.
- Lordosis .
- Kyphosis .
- Scoliosis Spine: deformity .
- Vertebral formula:
- 7 cervical.
- 18 thoracic (17-19).
- 6 lumbar (5-7).
- 5 sacral.
- 18 coccygeal (15-21).
- Interneural joint:
- Caudal articular facets of one vertebrae articulate with the cranial articular facets of the next.
- Orientation varies from horizontal to dorsal, with large degree of movement possible in the cervical vertebrae, limited caudally.
- Loose joint capsule, synovium, cartilage-covered joint surfaces.
- Intercentral joint:
- Each vertebral body is joined to the next by a fibrocartilagenous intervertebral disk (except first and second cervical vertebrae).
- There is no obvious nucleus pulposus.
- The disks are thin in the thoracic region, thickest in the coccygeal region.
- Transverse process joints:
- The last two lumbar vertebrae and the last vertebra and sacrum have synovial articulations between their transverse processes (in the latter case with the cranial edge of the sacrum).
- Interspinous ligaments: connect spinous processes.
- Ligamentum flavum: elastic connective tissue between the arches.
- Supraspinous ligament: white fibrous tissues running along the tops of the spinous processes.
- Nuchal ligament:
- Modification of the supraspinous ligament cranial to T4/5 into funicular (runs from back of skull to T4/5) and lamellar (paired sheets attaching to cervical spinous processes and merging caudally with the supraspinous ligament) parts.
- There are a cranial nuchal bursa at the atlas and suprapinous bursa over the cranial thoracic spinous processes.
- Dorsal longitudinal ligament: runs along the floor of the vertebral canal from the axis to the sacrum.
- Ventral longitudinal ligament:
- Runs along the ventral surface of the vertebral bodies beginning from the middle thoracic region.
- The crura of the diaphragm blend with it in the lumbar region.
- Finally it blends with the periosteum on the ventral surface of the sacrum.
- Intertransverse ligaments: connect lumbar transverse processes.
- Intercapital ligaments (costal conjugal ligaments): run between the heads of the ribs (excluding the first and the last few) over the intervertebral disk but do not impinge on the floor of the vertebral canal.
- Epaxial musculature- lies dorsal to the transverse processes and are extensors (or responsible for dorsoflexion) of the spine:
- Minor short muscles include theintertransversarii- between transverse processes,interspinalis- replaced by ligament,rotatores.
- Longissimus dorsi- extends from sacrum and ilium to insert in three parts -l lumborum- inserts on the lumbar transverse and articular processes,l thoracis- inserts on the thoracic transverse processes and the lateral surfaces of the ribs,l cervicis- inserts on the spinous and transverse process of the last four cervical vertebrae.
- Largest and longest muscle in the horse, filling the space between the spinous processes and lumbar transverse processes and ends of the ribs - rounding out the back.
- Responsible for extension of the back and lateral flexion of the thoracolumbar spine.
- Iliocostalis- merged with l lumborumfrom L4/5 caudally but inserts in distinct flat tendinous bundles in the thorax on the caudal border of ribs 1-15 and on the transverse process of C7.
- Spinalis- divides froml dorsirunning from spinous processes of the thoracic vertebrae and last four cervical vertebrae.
- Multifidus(multifidi) - deep muscle originating from lumbar spinous processes, sacrum, articular and mamillary processes of the lumbar vertebrae and transverse processes of thoracic vertebrae.
- Insert on spinous processes of the lumbar and last thoracic vertebra.
- Hypaxial musculature- other muscles of the trunk act as flexors (or responsible for ventroflexion of the spine):
- Longus colli- overlapping bundles covering the ventral surface of the cervical vertebrae and T1-5/6, inserting on the vertebral bodies and the transverse processes; flexes the neck.
- Psoas minor- ventral sublumbar muscle; from last thoracic and first few lumbar vertebral bodies to the arcuate line of the pelvis.
- Psoas major- from last two ribs, transverse processes and ventral and lateral surfaces of lumbar vertebrae to insert as a tendon uniting with iliacus to formiliopsoason the lesser trochanter of the femur.
- Quadratus lumborum- dorsal to the psoas muscles, from ventral surface of the last thoracic vertebrae to transverse processes of the lumbar vertebrae and the wing of the sacrum.
- Consists of the hip (coxal) bone, sacrum and first three coccygeal vertebrae.
- Joints and ligaments:
- Sacroiliac joint - transmits forces between vertebral column and hindlimb; little movement.
- Ventral sacroiliac ligament surrounds the joint which is crossed by fibrous bands.
- Dorsal sacroiliac ligament - strong band attaching to tuber sacrale and tops of the sacral spines.
- Sacrosciatic ligament (broad sacrotuberal ligament) - forms part of wall of pelvis; attaches to the border of the sacrum and transverse processes of the coccygeal vertebrae and to the ischiatic spine and tuber.
- Iliolumbar ligaments - connect sacropelvic surface of the ilium to the lumbar transverse processes.
- Pelvic symphysis - where the two hip bones join in the midline; no movement possible; juvenile cartilage is replaced by bone in the adult (=synostosis).
- The atlanto-occipital (AO) joint is a ginglymus or hinge joint (known as the 'yes' joint).
- The atlantoaxial (C1-2) joint is a trochoid or pivot joint (known as the 'no' joint).
- Axial rotation: C1-2 - about 107.5° > atlanto-occipital (AO) joint - about 27° > rest of cervical spine - <3°.
- Lateral bending: AO - up to 45° > rest of spine - about 25° > C1-2 - 3.9°.
- Dorsoventral flexion and extension: AO - 86.4° > C1-2 > rest of cervical spine; in foals C1-2 can move through nearly 40° and the dens can protrude into the vertebral canal during maximum flexion, whereas in adults there is only about 16° movement.
- With age, degree of movement of all types is significantly decreased from C2-6; C6-T1 there is age related loss of axial movement but no change in lateral or dorsoventral movement - these joints stay mobile due to daily activities such as grazing and grooming.
- Fusing of lateral joints of lumbar spine (L5-6, L4-5) not uncommon, presumed development and to provide extra stability.
- Maximum lateral and rotational movement T10-14, probably accounts for the incidence of vertebral body osteophytes in this region.
- T12-18 develop broad flat dorsal spinous processes → narrowing of the interspinous spaces in early years. Degree depends on conformation, and can lead to impingement of dorsal spinous processes, particularly if jumping, ie due to maximal extension of back.
- Increased axial and lateral movement in T9-T16 → susceptible to compression fractures; greatest at T12, where the highest incidence of thoracic vertebral fractures occurs.
- T18-L6 have larger articular surfaces, and therefore more resistant to compression, but articular facets are interlocking, limiting ability to absorb axial rotational forces → susceptible to comminution fractures.
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