Navicular bone: suspensory desmotomy in Horses (Equis) | Vetlexicon
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Navicular bone: suspensory desmotomy

ISSN 2398-2977

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Introduction

  • A change in the biomechanics of the navicular suspensory apparatus may relieve pain associated with navicular disease   Navicular bone: syndrome  .
  • Surgery is proposed based on mechanically-based etiology and involves sectioning the collateral sesamoidean ligaments (CSL):
    • These ligaments contain a large number of nerve fibers and surgery may be a form of neurectomy.
    • Exact biomechanical role of the CSLs is unknown.
  • Surgery is proposed to decrease forces on the navicular bone during the caudal phase of the stride.

Uses

  • Unresponsive navicular disease   Navicular bone: syndrome  :
    • Cases in which the disease was present for >1 year showed a decreased response to surgery.
    • Surgery should be attempted early in disease course if being used.

Disadvantages

  • Surgical procedure - requires general anesthesia   Anesthesia: general - overview  .
  • Potential disruption of the collateral ligaments of the pastern   →   instability.
  • Uncertain results.

Alternative techniques

Time required

Preparation

  • 30 min.

Procedure

  • 30-60 min.

Decision taking

Criteria for choosing test

  • Exhausted other treatment options.

Requirements

Materials required

Minimum consumables

  • Standard soft tissue surgical kit.
  • Esmarch tourniquet.

Preparation

Site preparation

  • General anesthesia and dorsal recumbency.
  • Clean foot and prepare entire pastern aseptically - apply tourniquet proximal to fetlock.
  • The ligaments run from the distal dorsal depression of the proximal phalanx to the medial and lateral sides to the navicular bone - in a dorsoproximal distocaudal direction. 
  • The ligaments are closely associated with the collateral sesamoidean ligaments of the proximal interphalangeal joint.

Technique

Approach

Step 1 - Make the incision

  • Incise the skin obliquely from the medial distal eminence of the proximal phalanx extending 3-4 cm dorsally and distally toward the common digital extensor tendon. The incision ends 0.5 cm proximal to the coronary band and is not parallel to the ligament.
  • Repeat this incision on the lateral side.
  • Continue through the subcutaneous tissue to identify the coronary plexus which is at the proximal edge of the collateral cartilage - dissection should be axial to the cartilage to allow identification of the CSL.

Step 2 - Dissect under the ligament

  • Use hemostats to bluntly dissect under the suspensory ligament running oblique to the incision.

Core procedure

 

Step 1 - Cut the ligament

 
  • Elevate and transect the ligaments on the medial and lateral sides of the limb.

Do not cut the collateral ligaments of the proximal interphalangeal joint.

  • Incision into the pastern joint does not seem to create complications as long as aseptic technique was followed.

Exit

 

Step 1 - Close the incision

 
  • Close subcutaneous tissues and skin routinely.
  • Bandage to include the foot and prevent the bandages from slipping upwards and exposing the incisions.

Aftercare

Immediate Aftercare

Analgesia

Long term Aftercare

Follow up

  • Balance hooves and use corrective shoeing.
  • Walking exercise for 3 weeks post-operatively.
  • Return to full work, after a gradually increasing exercise program, at about 3 months post-operatively.

Outcomes

Reasons for treatment failure

  • An incomplete response to surgery was seen with these concurrent conditions:
    • Flexor cortex defects.
    • Proximal border enthesiophytes.
    • Mineralization of the DDFT
    • Lameness present for >1 year.
  • Infection of the pastern joint   PIP joint: infection - post-navicular suspensory desmotomy  .

Prognosis

  • Fair - literature suggests 70% of operated horses return to work without lameness; current results are probably slightly less.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Wright I M (1993) A study of 118 cases of navicular disease: treatment by navicular suspensory desmotomy. Equine Vet J 25, 501-509. Erratum in:Equine Vet J 1994 26, 77 PubMed.
  • Wright I M  (1986) Navicular suspensory desmotomy in the treatment of navicular disease: technique and preliminary results. Equine Vet J 18, 443-446 PubMed.

Other sources of information

  • Furst A E & Lischer C J (2006) The Foot. In: Equine Surgery. Eds: Auer & Stick. Saunders Elseveir, USA. pp 1210-1212.