Equis ISSN 2398-2977

Carpus: sheath tenosynovitis

Synonym(s): Carpal tunnel syndrome, Carpal canal syndrome

Contributor(s): Bud G E Fackelman, Graham Munroe, Chris Whitton

Introduction

Pathogenesis

Etiology

  • Primary or idiopathic synovitis of the sheath post-trauma:
    • No evidence of physical damage on palpation and imaging, but marked synovial inflammation.
  • Chronic synovitis and enlargement of the carpal sheath following trauma to sheath:
    • Acute injury and moderate to severe lameness that does not resolve.
    • No physical cause of the persistent inflammation but gradually becomes chronic with thickening of the sheath wall, palmar retinaculum and surrounding perisheath tissue.
    • The synovium becomes chronically damaged and thickened with adhesions, synovial masses and clumps. There may or may not be enlargement of the SDFT/DDFT.
  • Frontal plane or comminuted fracture Accessory carpal: fracture of the accessory carpal bone can affect the carpal canal and sheath:
    • Fracture fragments can impinge on the DDFT and more rarely, comminuted bone fragments may be displaced into the carpal sheath.
    • Both can lacerate or damage the DDFT to varying degrees.
  • Superficial digital flexor tendonitis in the carpal sheath has been occasionally reported in older horses (15 years) and Standardbred racehorses:
    • Acute cases have sheath distension without any obvious signs involving the SDFT elsewhere.
    • Injury to the SDFT may also occur at the musculotendinous junction often subsequent to a fall or other severe trauma. If complete rupture occurs the horse may require humane destruction.
    • Focal tears lead to a moderate to severe lameness with sheath distension.
  • Primary deep digital flexor tendonitis in the carpal sheath is uncommon:
    • Occasionally marginal tears are detected on tenoscopy in chronically lame horses with carpal sheath distension.
  • Tearing of the radial head of the DDFT can cause tenosynovitis of the carpal sheath:
    • The amount of distension of the sheath and presenting lameness is variable.
  • Osteochondroma Carpus: osteochondroma of the caudal distal radius:
    • Most present in young horses (2-6 years old) with distension of the sheath and variable, often recurrent, lameness.
    • The lesion is most likely to be in the lateral one-third of the radius.
    • Most are single, sharply pointed protuberances situated between 7 and 33 mm proximal to the distal radial physis.
    • They are variable in size but when clinical signs are present they are impinging on the overlying DDFT.
  • Desmitis and tearing of the accessory ligament of the SDF:
    • This is an uncommon injury mainly in European Standardbred trotters, and occasional show jumpers, eventers, dressage horses and Thoroughbred racehorses.
    • The primary injury to the ligament leads to a secondary sheath synovitis and may be associated with other injuries in the carpal canal such as SDFT tendinitis SDFT: tendinitis and flexor retinaculum fibrosis.
  • Intrathecal hemorrhage which may be idiopathic, traumatic, eg fall, or secondary to damage to the SDFT/DDFT/ALSDFT or accessory carpal bone.
  • Exostosis of the caudal margin of the bony remnant of the distal radial physis:
    • One or two caudally directed physeal remnants can occur with variable shapes from sharp to irregular and blunted.
    • Similar interference to the DDFT, as in the radial osteochondroma, occurs with fraying and tearing of fibers, sometimes over an extensive area.
  • Deep DDFT tendon injuries, whether due to tendinitis Deep digital flexor tendon: tendinitis or rubbing on the distal radial osteochondroma/physeal exostosis:
    • Can lead to an expanded flexor tendon volume within the carpal canal and may lead to restriction and carpal tunnel-like syndrome.
    • Additionally, some chronic carpal sheath problems, such as desmitis of the ALSDFT, sheath tenosynovitis, and ALSDFT tendonitis, may lead to secondary perisheath and carpal retinacula fibrosis, further constricting the carpal canal.

Timecourse

  • Acute or chronic.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hawthorn A et al (2016) Post operative synovial sepsis following endoscopic surgery: Increased risk associated with the carpal sheath. Equine Vet J 48 (4), 430-433 PubMed.
  • Jorgensen J S et al (2015) Musculoskeletal lesions and lameness in 121 horses with carpal sheath effusion (1999-2010). Vet Radiol Ultrasound 56 (3), 307-316 VetMedResource.
  • Minshall G J & Wright I M (2014) Frontal plane fractures of the accessory carpal bone and implications for the carpal sheath of the digital flexor tendons. Equine Vet J 46 (5), 579-584 PubMed.
  • Taintor J, Caldwell F & Almond G (2013) Aseptic tenosynovitis of the carpal flexor sheath caused by rupture of the accessory ligament of the deep digital flexor tendon. Can Vet J 54 (8), 765-768 PubMed.
  • Minshall G J & Wright I M (2012) Tenosynovitis of the carpal sheath of the digital flexor tendons associated with tears of the radial head of the deep digital flexor: Observations in 11 horses. Equine Vet J 44 (1), 76-80 PubMed.
  • Wright I M & Minshall G J (2012) Clinical, radiological and ultrasonographic features, treatment and outcome in 22 horses with caudal distal radial osteochondromata. Equine Vet J 44 (3), 319-324 PubMed.
  • Byron C R et al (2010) Modified tenoscopic method for carpal flexor retinaculum release in a horse. Vet Surg 39 (2), 239-243 PubMed.
  • Nixon A J, Schachter B L & Pool R R (2004) Exostoses of the caudal perimeter of the radial physis as a cause of carpal synovial sheath tenosynovitis and lameness in horses: 10 cases (1999-2003). J Am Vet Med Assoc 224 (2), 264-270 VetMedResource.
  • Textor J A, Nixon A J & Fortier L A (2003) Tenoscopic release of the equine carpal canal. Vet Surg 32 (3), 278-284 PubMed.
  • Southwood L L et al (1998) Tenoscopic anatomy of the equine carpal flexor synovial sheath. Vet Surg 27 (2), 150-157 PubMed.
  • Cauvin E R J et al (1997) Gross and ultrasonographic anatomy of the carpal flexor tendon sheath in horses. Vet Rec 141 (19), 489-495 PubMed.
  • Cauvin E R J et al (1997) Endoscopic examination of the carpal flexor tendon sheath in horses. Equine Vet J 29 (6), 459-466 PubMed.
  • Munroe G A & Cauvin E (1997) Surgical treatment of a comminuted articular fracture of the accessory carpal bone in a thoroughbred horse. Vet Rec 141 (2), 47-49 PubMed.
  • Redding W R (1993) Evaluation of equine digital flexor tendon sheath using diagnostic ultrasound and contra radiography. Vet Radiol Ultrasound 34, 42-48 WileyOnline.

Other sources of information

  • McIlwraith C W, Wright I & Nixon A (2014) Diagnostic and Surgical Arthroscopy in the Horse. 4th ed. Mosby, USA.
  • Dyson S J (2011) The Carpal Canal and Carpal Synovial Sheath. In: Diagnosis and Management of Lameness in the Horse. 2nd edn. Eds: Ross M K & Dyson S J. Elsevier Saunders. pp 777-779.


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