Equis ISSN 2398-2977

Deep digital flexor tendon: tendinitis

Synonym(s): Deep digital flexor tendonitis

Contributor(s): Larry Booth, Graham Munroe, Vetstream Ltd, Chris Whitton

Introduction

  • Cause: uncertain in many cases but includes exercise, fatigue, degenerative changed with age, direct trauma +/- infection, pathology in other structures such as the digital sheath (DFTS) and carpal/tarsal sheaths is common and can have a direct affect on the deep digital flexor tendon (DDFT).
  • Signs: often severe and acute lameness in early cases, becoming mild to moderate with time and rest but high tendency to recurrence with medical treatment   Musculoskeletal: gait evaluation  . Acute cases will have local heat, pain, and swelling often associated with the DFTS    Digital sheath: tenosynovitis 03  , or  DDFT   Musculoskeletal: physical examination - adult  .
  • Diagnosis: clinical signs with regional and intrasynovial analgesia plus ultrasonography   Ultrasonography: flexor tendon  , radiography   Hindlimb: radiography   and MRI   Magnetic resonance imaging  .
  • Treatment: cold therapy, anti-inflammatories, compression bandaging and rest in acute cases, followed by controlled exercise program and corrective farriery. Surgery (tenosynovioscopy) is important for definitive diagnosis and treatment in those cases involving tendon sheaths. 
  • Prognosis: guarded to poor depending on the site and type of DDFT pathology and the4 speed and extent of treatment.
Print off the Owner factsheet on Tendon injuries to give to your clients.

Pathogenesis

Etiology

  • Primary:
    • Less clear in many cases with much less research having been conducted than in the SDFT.
    • Exercise, fatigue and degenerative changes may be involved, most commonly in the digital sheath and distal phalangeal regions.
    • Direct trauma/puncture wounds/infection.
  • Secondary:
    • In the carpal/metacarpal region: associated with recurrent desmitis of the accessory ligament of the deep digital flexor tendon (ALDDFT)   Accessory ligament DDFT: forelimb - desmitis  +/- superficial digital flexor tendinitis (SDFT)   SDFT: tendinitis  - ? secondary/relationship.
    • To primary pathological conditions of bones, eg in the carpal sheath: irritation by solitary osteochondromas   Carpus: osteochondroma  and excessive distal radial physeal exostosis; in the hock: in association with bony lesions of the sustentaculum tali of the calcaneus.
    • Inflammation of surrounding tendons, eg proximal and distal digital annular ligaments (PDAL/DDAL) caused by blunt trauma, eg overreach, to plantar fetlock/pastern.

Pathophysiology

  • The DDFT:
    • Varies in shape, size and component elements according to its position in the limb.
    • Is elastic with a high tensile strength, limiting carpal and fetlock extension under high loading.
    • Stabilizes the distal interphalangeal joint in the digit.
    • Facilitates flexion of the proximal interphalangeal joint during weight bearing. 
    • Is closely related to the navicular bone within the hoof capsule during various phases of propulsion.
  • With the advent of more advanced imaging techniques, including ultrasound    Ultrasonography: flexor tendon  , MRI   Magnetic resonance imaging  , CT   Computed tomography   and tenoscopy techniques   Tenosynovioscopy  several different lesions involving the DDFT have been identified. These are listed below. In many cases their etiology and pathophysiology are uncertain at this present time.
  • Injury of the DDFT is most common in the metacarpal region in association with desmitis of the ALDDFT   Accessory ligament DDFT: forelimb - desmitis  (often recurrent chronic cases), and less commonly chronic SDFT tendinitis.
  • Deep digital flexor (DDF) tendinitis in the metacarpal region outside of the ALDDFT or DFTS is rare. Proximal lesions have been occasionally detected on MRI and can be associated with the carpal sheath.
  • Lesions of the DDFT commonly occur in the DFTS where they cause distension of the sheath   Digital sheath: tenosynovitis  . Secondary lesions of the annular ligament   Annular ligament: constriction   and other clinical signs of complex tenosynovitis of the DFTS may also occur.
  • Distal lesions of the DDFT commonly occur in the foot.
  • In the pastern region the DDFT is relatively close to the skin surface making it vulnerable to damage by direct trauma or puncture wounds.
  • Blunt trauma, eg overreach, to plantar fetlock/pastern    →    inflammation of the surrounding subcutaneous tissues and  PDAL/DDAL    →   undue pressure on DDFT. Occasional cases of DDFT tendinitis occur in the pastern region with or without the lesion extending into the foot. Rupture of the DDFT can occur within the foot or pastern region usually secondary to a previous neurectomy of the palmar digital nerves.
  • Lesions in the carpal sheath are related to solitary osteochondroma   Carpus: osteochondroma   of the distal radius, enlarged distal radial physeal exostosis, injuries of the radial head of the DDFT or traumatic injuries and penetrations   Carpus: sheath tenosynovitis  .
  • Lesions of the DDFT in the hock region and proximal metatarsus are uncommon. They have been recorded in young Thoroughbreds in training with swelling in the proximal plantar metatarsal region. Primary lesions of the DDFT occasionally occur in the tarsal sheath. Wounds in the medial aspect of the tarsus may involve the DDFT and tarsal sheath, with secondary sepsis seriously deteriorating the prognosis. Injuries of the sustentaculum tali may occur after trauma    →    damage to the DDFT as it runs through the tarsal sheath.

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.
  • Cillán-García E et al (2013) Deep digital flexor tendon injury within the hoof capsule; does lesion type or location predict prognosis? Vet Rec 173 (3), 70 PubMed.
  • King J N et al (2013) MRI findings in 232 horses with lameness localized to the metacarpo(tarso)phalangeal region and without a radiographic diagnosis. Vet Radiol Ultrasound 54 (1), 36-47 PubMed.
  • Montgomery L, Elliott S B & Adair H S (2013) Muscle and tendon heating rates with therapeutic ultrasound in horses. Vet Surg 42 (3), 243-249 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.
  • Smith M R & Wright I M (2012) Endoscopic evaluation of the navicular bursa: observations, treatment and outcome in 92 cases with identified pathology. Equine Vet J 44 (3), 339-345 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.
  • Beck S et al (2011) Are matrix and vascular changes involved in the pathogenesis of deep digital flexor tendon injury in the horse? Vet J 189 (3), 289-295 PubMed.
  • Blunden A, Murray R & Dyson S (2009) Lesions of the deep digital flexor tendon in the digit: a correlative MRI and post mortem study in control and lame horses. Equine Vet J 41 (1), 25-33 PubMed.
  • Schramme M C (2008) Treatment of deep digital flexor tendonitis in the foot. Equine Vet Educ 20 (7), 389-391 VetMedResource.
  • Eliashar E, Schramme M C, Schumacher J, Ikada Y & Smith R K W (2001) Use of bioabsorbable implant for the repair of severed digital flexor tendons in four horses. Vet Rec 148 (16), 506-509 PubMed.
  • Barr A R S et al (1995) Tendonitis of the deep digital flexor tendon in the distal metacarpal/metatarsal region associated with tenosynovitis of the digital sheath in the horse. Equine Vet J 27, 348-355 PubMed.
  • Dyson S (1991) Desmitis of the accessory ligament of the deep digital flexor tendon - 27 cases (1986-1990). Equine Vet J 23, 438-444 PubMed.

Other sources of information

  • Ross M W & Dyson S J (2011) The Deep Digital Flexor Tendon. In: Diagnosis and Management of Lameness in the Horse. Elsevier, USA. pp 726-733.
  • Dyson S J & Schramme M (2004) Lameness in 162 Horses Associated with Deep Digital Flexor Tendonitis: Diagnosis Using Magnetic Resonance Imaging. In: Proc 43rd BEVA Congress. Equine Vet J Ltd, UK. pp 124.
  • McIlwraith C W (2002) Tendonitis of the Deep Digital Flexor Tendon. In: Adam's Lameness in Horses. 5th edn. Lippincott, Williams & Wilkins. pp 620-621.


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