Pelvis: trauma - sacroiliac in Horses (Equis) | Vetlexicon
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Pelvis: trauma – sacroiliac

ISSN 2398-2977


Introduction

Presenting signs

  • Hindlimb lameness.

Acute presentation

  • Acute onset hindlimb lameness.
  • Localized sensitivity to palpation of soft tissues over site and/or tuber sacrale.

Pathogenesis

Etiology

  • Substantial trauma causing pelvic rotation or high stresses, eg fall, during transport, becoming cast in a confined space, rearing and falling backwards, catastrophic musculoskeletal injury during racing.
  • Chronic joint trauma in performance horses.

Pathophysiology

  • The dorsal sacroiliac ligament attaches to tuber sacrale and sacral spines, and blends into the medial border of ilium and the lateral border of sacrum.
  • The ventral sacroiliac ligament surrounds the cranial aspect of the joint capsule running from the dorsal sacrum to the ilium.
  • The sacroiliac and sacrosciatic ligaments form a strong ligamentous sling supporting the caudal vertebral column.
  • The sacroiliac joint is the synovial articulation between the ventral wing of the ilium and the dorsal wing of the sacrum, providing support during weight bearing and helping to transfer hindlimb propulsive forces to the vertebral column.
  • The sacroiliac joint is supported by the dorsal, ventral and interosseous sacroiliac ligaments.
  • Substantial trauma is usually required to damage these structures owing to their being deep anatomically and protected by considerable muscle mass.
  • Lesions:
    • Complete sacroiliac ligament disruption.
    • Uni/bilateral joint capsule disruption.
    • Avulsion fractures of the sacroiliac ligament attachment sites.
    • Sacroiliac joint laxity/instability.
    • Sacroiliac joint subluxation/luxation.

Diagnosis

Presenting problems

  • Hindlimb lameness.
  • Poor performance.
  • Back pain.

Client history

  • Varies with duration and extent of injury:
    • History of trauma.
    • Hindlimb lameness   Musculoskeletal: gait evaluation  .
    • Poor performance.
    • Resisting jumps.
    • Unwillingness to work, especially at higher speeds.
    • Poor quality canter.

Clinical signs

Acute

  • Sudden onset hindlimb lameness.
  • Pain on palpation of soft tissues over dorsal croup region    Musculoskeletal: physical examination - adult  .
  • Palpable protective muscle spasm in middle gluteal, vertebral portion of biceps femoris, semitendinosus and/or semimembranosus muscles.
  • Pain response to firm pressure applied over dorsal aspects of tubera sacrale or caudal lumbar/sacral dorsal spinous processes.
  • May be sacroiliac asymmetry (not always significant)   Pelvis: asymmetry 02  .
  • Palpable or visible independent movement of tubera sacrale (sacroiliac luxation).
  • Palpable crepitus during movement or lateral rocking of pelvis (fractures) may be auscultated using a stethoscope.
  • Resentment to full flexion of hindlimb on affected side   Musculoskeletal: manipulative tests  .
  • Resentment to rectal palpation of sacroiliac region   Musculoskeletal: rectal palpation  .

Chronic

  • Mild, chronic, hindlimb lameness/stiffness that cannot be localized to any other region by routine lameness examination and local anesthesia techniques.
  • Almost always poor hindlimb impulsion, especially when ridden.
  • Sometimes restricted hindlimb action: close behind or plaiting.
  • Lameness/gait abnormalities usually unilateral corresponding to side of injury, but may be bilateral.
  • Poor development of epaxial muscles in thoracolumbar region, asymmetry in gluteal musculature    Musculoskeletal: physical examination - adult      Hindlimb: muscle atrophy 02  +/- tubera sacrale asymmetry (uncommon and not always significant)   Pelvis: asymmetry 03  .
  • Back stiffness: reduced flexibility thoracolumbar region.
  • Exaggerated response to pressure over tubera sacrale   Musculoskeletal: back pain  .
  • Compensatory stiffness in proximal hindlimb.
  • Reluctance to stand on one hindlimb for prolonged periods.

Diagnostic investigation

Local anesthesia techniques

  • Local infiltration of sacroiliac joint region (NB: a technically difficult procedure) produces a profound improvement in gait:
    • Restrain horse in stocks.
    • Stand horse squarely behind with even weightbearing between hindlimbs.
    • Fine clip and aseptically prepare area in the midline cranial to tubera sacrale.
    • Insert an 18G 9-15 cm spinal needle axial to the left tuber sacrale.
    • Direct needle obliquely and caudally at approximately 20° to the vertical, towards the right sacroliliac joint, between the divergent spinous processes of the 6th lumbar and 1st sacral vertebrae.
    • If bone is encountered, partially withdraw and redirect needle.
    • Advance until caudomedial aspect of sacroiliac joint.
    • Inject 20 ml mepivacaine   Mepivacaine  .
    • Walk horse for 15 min before assessing any gait change.
    • Repeat for right sacroiliac joint.
  • Hindlimb analgesia:

Rectal palpation

  • Acute: pain/discomfort over sacroiliac region   Musculoskeletal: rectal palpation  .
  • Chronic: usually unrewarding unless bone proliferation present, or crepitus or joint laxity palpable during movement.

Sacroiliac joint provocation tests

  • Specific manipulation tests have been devised to elicit pain/discomfort responses related to sacroiliac joint injury or pelvic fracture.
  • Test 1: simultaneous gradual compression of the dorsal aspects of both tubera sacrale:
    • Positive response: 
      • May be dramatic causing the horse to suddenly flex both hindlimbs and may even cease to weight bear (pelvic fractures).
    • Negative response: 
      • Minimal pain.
      • Slight extension of lumbosacral joint.
  • Test 2: rhythmically apply a ventrally directed force, from above (use a mounting block) over the sixth lumbar and second sacral dorsal spinous processes:
    • Positive response: 
      • Resentment to this stretching of the sacroiliac ligaments.
      • Protective gluteal/sublumbar muscle spasm.
    • Negative response: 
      • Fluid vertical motion of the lumbosacral region (1-2 cm dorsoventral movement over lumbar region).
  • Test 3: apply lateral pressure to the tuber ischium with one hand whilst applying an opposite lateral force (horizontal) to the third coccygeal bone at the base of the tail alternate direction of pressure to alternately compress and distract the sacroiliac joint surfaces:

Apply only moderate pressure to avoid exacerbating sacroiliac lesions by overstretching.

    • Positive response:
      • Pain reaction to either compression (sacroiliac joint conditions) or distraction (sacroiliac ligament inflammation) of the sacroiliac joint surfaces, uni- or bilaterally.
    • Negative response: 
      • No pain reaction.
  • Test 4: repeat of test 3 using ischial tuberosity and third coccygeal bone as points to apply pressure.

Ossification of the tubera sacrale is not complete in horses <2 years old, making evaluation of the tuber sacrale area difficult in these cases.

Radiography

  • The deep anatomical location of the sacroiliac joints makes radiographic imaging difficult   Pelvis: radiography  .
  • Fractures may be identified   Pelvis: fracture  .
  • Sacroiliac joint space may be enlarged but interpretation is often difficult   Pelvis: radiography  .

Ultrasonography

  • The dorsal sacroiliac ligament can clearly be distinguished from the tendon of the longissimus dorsi muscle, especially in longitudinal images, on either side of the sacral dorsal spinous processes, caudal to the tuber sacrale   Ultrasonography: bone / joints    Ultrasonography: musculoskeletal  :
    • Lesions:
      • Enthesiophytes of the tubera sacrale attachments.
      • Fiber orientation irregularities and hypoechogenicity.
  • The interosseous sacroiliac ligament cannot be imaged because of its position beneath the ilial wing.
  • The ventral sacroiliac ligament, the bony surfaces of the sacrum and ilium, and the caudomedial and ventral borders of the sacroiliac joint can be visualized via transrectal ultrasonography, and comparisons made between left and right sides:
    • Lesions: peri-articular changes.

Scintigraphy

  • Interpretation of results is often difficult. Comparison should be made with normal images from horses of comparable age where there is usually a high degree of left-right symmetry of isotope uptake    Bone: scintigraphy      Pelvis: sacroiliac joint - scintigraphy  .
  • A high degree of left-right asymmetry is likely to be abnormal but this is not conclusive.
  • Oblique views are best for distinguishing between left and right sacroiliac joints but interpretation can be unreliable because of discrepancies in camera positioning between the sides.
  • The overlying thick gluteal musculature may attenuate radiopharmaceutical uptake from an affected joint.

Thermography

  • Thermography has been used to detect inflammation or muscle strain within the sacroiliac region   Thermography  .

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.
  • Failure to localize lameness to any other distal hindlimb region using standard lameness diagnostic and local anesthesia techniques.

Definitive diagnostic features

  • Response to specific manipulative tests.
  • Response to local analgesia.
  • Ultrasonography.
  • Scintigraphy.
  • Diagnosis by exclusion.

Differential diagnosis

Treatment

Standard treatment

  • Symptomatic.
  • Rest.
  • Anti-inflammatories: phenylbutazone    Phenylbutazone  , flunixin meglumine    Flunixin meglumine   or ketoprofen   Ketoprofen  /vedaprofen    Vedaprofen  . May be given by intra-articular injection of sacroiliac joint (see above: local anesthetic infiltration), this is a technically difficult procedure to perform, or systemically.
  • Physiotherapy   Musculoskeletal: physiotherapy  .

Subsequent management

Treatment

  • Acute injuries: strict box rest (30-45 days), followed by prolonged rest (6-12 months).
  • Gradual return to a low-level exercise regime to maintain muscles of back and gluteal region throughout the rest period (acute and chronic injuries).

Prevention

Outcomes

Prognosis

  • Poor for sacroiliac joint injuries to return to previous level of soundness.
  • Guarded for ligament injuries.

Expected response to treatment

  • Slow recovery (several months).
  • Persistent low-grade lameness common.
  • Pasture-soundness usually achieved + low-level exercise tolerance.

Reasons for treatment failure

  • Failure to achieve a specific diagnosis.
  • Chronicity of condition before presentation.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Powell S (2011) Investigation of pelvic problems in horsesIn Pract 33 (10), 518-524 VetMedResource.
  • Varcoe-Cocks K, Sagar K N, Jeffcott L B & McGowan C M (2006) Pressure algometry to quantify muscle pain in racehorses with suspected sacroiliac dysfunction. Equine Vet J 38 (6), 558-562 PubMed.
  • Kersten A A M & Edinger J (2004) Ultrasonographic examination of the equine sacroiliac region. Equine Vet J 36 (7), 602-608 PubMed.
  • Dyson S et al (2003) The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse. Equine Vet J 35 (3), 226-232 PubMed.
  • Dyson S et al (2003) The sacroiliac joints: evaluation using nuclear scintigraphy. Part 2: Lame horses. Equine Vet J 35, 233-239 PubMed.
  • Dyson S & Murray R (2003) Pain associated with the sacroiliac joint region: a clinical study of 74 horses. Equine Vet J 35 (3), 240-245 PubMed.
  • Jeffcott L, Dalin G, Ekman S & Olssen S-E (1985) Sacroiliac lesions as a cause of chronic poor performance in competitive horses. Equine Vet J 17, 111-118 PubMed.

Other sources of information

  • Dyson S J (2003) Diagnosis and Management of Sacroiliac Joint Injuries. In: Diagnosis & Management of Lameness in the Horse. Eds: Ross M W & Dyson S J. Saunders, USA. pp 501-508.