Wounds

• There are 4 phases of wound healing…

  • The first phase is haemostasis
  • There is an initial vasoconstriction for the first 5-10 minutes which results in the formation of a blood clot.
  • The second phase is the inflammatory phase aka the debridement phase
  • This occurs 1-3 days after injury
  • The third phase is the proliferative phase
  • The fourth phase is the remodelling / maturation phase
  • This occurs 2 weeks after trauma and ends in the formation of scar tissue 1-2 years later
• the proliferative phase involves a filing of the wound bed with healing tissue (fibroblasts). This occurs in the first few days and lasts for weeks after injury.

  • Fibroplasia
  • Angiogenesis
  • Epithelisation
  • Contraction
• Epithelialisation is defined as the process of covering denuded epithelial surfaces. It gives the characteristic pink rim, it takes a while to appear although cellular epithelialisation commences 24 to 48 hours after wounding. In full thickness wounds, epithelialisation cannot proceed until a bed of granulation tissue has formed. this process can be inhibited by…

  • Infection
  • Desiccation of the wound surface
  • Exuberant granulation tissue
  • Repeated dressing changes (every dressing change removes the top layer of cells)
• Contraction starts 2 weeks after the wound occurs and continues for several weeks. This is very important, especially for horses

  • Accelerates closure
  • Increase cosmesis (cosmetics) of scar
  • Less need for epithelialization
• There are large differences in healing in horses compared to ponies. The main differences seen in ponies are…

  • 1 & 2 intention healing more rapid in ponies and is accompanied by fewer complications
  • Quicker & more intense inflammatory response
  • Pony wounds more resistant to infection
  • Greater contraction due to higher number of leukocytes recruited
  • Less wound dehiscence (likely related to the higher resistance to infection)
  • Fewer bone sequestrate
  • Less exuberant granulation tissue due to more intense and a less prolonged inflammatory phase
• When treating wounds healing by second intention, inflammation should be stimulated until the wound as filled with granulation tissue, and thereafter should be inhibited.
• Wounds should be clipped to provide a 5 to 10cm margin around wounds or larger if synoviocentesis or a pressure test is being performed
• The key recommendations for wound lavage are…

  • The use of clean, potable tap water can be considered instead of saline for lavaging wounds
  • The use of povidone iodine may be beneficial for contaminated wounds
  • Lavage pressures of 13 psi (12 mL syringe with 22 g needle) are recommended for traumatic wounds
• For cleaning/cleansing consider using…

  • 0.05% chlorhexidine (gluconate) 4%
  • Superior antibacterial activity than povidone iodine
  • 12.5 mL in 1L of saline
  • 0.1-0.2% povidone iodine
  • Inactivated by organic material
  • Evidence for dilute povidone iodine use in contaminated wounds (1-2 mL in 1L of saline)
  • Just water
  • Hose a very contaminated wound down first, to remove the bulk of debris and contamination
  • Water is toxic to fibroblasts so ideally do not use this for cleaning (Saline, iodine or dilute chlorhexidine is preferred
• The steps for wound preparation goes as follows.

  1. Restraint (physical and chemical) and move to a clean, well-lit and calm environment
  2. Hose down gross contamination and apply local anaesthetic (perineural anaesthesia with mepivacaine)
  3. Put gel on the wound (e.g., KY Jelly prevents hair debris on the wound) and clip around it (5-10cm from the periphery of the wound)
  4. Clean with chlorhexidine, iodine or sterile saline
  5. Put on gloves and palpate the depth of the wound (digital exploration, sterile probes and joint taps)
  6. Suture if necessary and bandage as needed (wound management)
• For the dorsal perpendicular approach to the DIP joint, the needle is inserted at the proximal edge of the coronet, approximately 0.75 inch (2 cm) lateral or medial to the midpoint of the coronet (i.e., at the edge of the extensor ligament). The needle is directed distally, perpendicular to the bearing surface of the hoof.

  To perform the dorsal inclined approach to the DIP joint, a needle is inserted near or on the midline, perpendicular to the skin surface immediately proximal to the coronary band.
• To enter the PIP joint, the needle is inserted on the dorsal midline about 1 cm distal to an imaginary line drawn between the medial and lateral eminences for attachment of the collateral ligaments on the distal end of the proximal phalanx and is directed obliquely distally and medially

  OR

  The needle is inserted on the dorsal midline one-half inch (1.3 cm) proximal to the imaginary line between eminences and directed slightly distally and slightly medially
• The digital synovial sheath can be entered at any of the pouches evident along its length. Even when the digital synovial sheath is not effused, it often can be entered on the palmar aspect of the pastern between the proximal and distal digital annular ligaments, where the deep digital flexor tendon lies close to the skin
• To enter the dorsal pouch of the metacarpophalangeal / metatarsophalangeal joint, insert the needle under the lateral edge of the common digital extensor tendon at, or slightly above the palpable joint space and direct the needle medially and parallel to the frontal plane of the joint.

  OR

  Hold the limb in flexion, insert the needle into the lateral aspect of the palmar/plantar pouch
• to enter the carpus, insert the needle medial to the palpable tendon of the extensor carpi radialis muscle.
• to enter the tibiotarsal joint, palpate the tibiotarsal joint distal to the level of the medial malleolus of the tibia. Insert the needle just medial or lateral to the visible saphenous vein, to 1.5 inches 2.5 to 3.8 cm) distal to the level of the palpable medial malleolus. The joint capsule is superficial and thin.
• Using a plantarolateral approach to the tarsometatarsal joint, a needle is inserted above the head of the 4th metatarsal bone and directed in a dorsomedial direction. Approaching the tarsometatarsal joint by directing the needle dorsodistally in a sagittal plane may increase accuracy of arthrocentesis of this joint.
• The femoropatellar joint can be accessed by inserting a needle between the middle and medial patellar ligaments or between the middle and lateral patellar ligaments, 1 to 1.5 inches (2.5 to 3.8 cm) proximal to the palpable proximal aspect of the tibial tuberosity. The needle is inserted parallel to the ground

  through the large fat pad between the patellar ligaments and joint capsule.
• For the fetlock you want to take 4 view, DP, LM and two obliques
• Radiography is good for assessing synovial structures and you can evaluate for evidence of bone trauma
• Ultrasound is very sensitive of picking up bony fragments where you see the hyperechoic region and an artefact underneath (anechoic shadow)
• what probe should be used when assessing soft tissue injuries?

  linear
• SDFT and DDFT rupture = dropped fetlock and toe pointing up
• SDFT rupture = dropped fetlock
• DDFT rupture = toe pointing up
• a pressure test requires a sterile prep of the joint, then insert a needle in the joint (ideally far away from the wound) and try to aspirate fluid for macroscopic analysis. Inject saline in the joint until it’s fully distended. A wound may leak if it communicates with the joint being instilled with fluid

  • You need to distend the balloon fully to see a leak
  • Leak cases must be referred
• Where possible it is preferable to use perineural techniques to avoid flooding wound edges with LA and adversely affecting wound healing. Line or ring blocks can be used.
• drains in wounds are useful for eliminating dead space by preventing build up of serum or exudate in the wound. Remove drains when minimal discharge

  • after ~5 days may become a source of contamination and result in exudate so should be removed.
• Absorbable sutures for muscle or non-external layers.
• Suture removal at 10 to 14 days (always clean prior to suture removal to avoid recontamination of site during suture removal).
• • Multifilament non-absorbable suture for distal limb wounds
• what needle type should you use to suture a wound closed?

  cutting
•  consider dressing the wound, there are different options…

  • Non-adherent gauze like
  • When no discharge and doesn’t stick to wound
  • Foam dressing for exudative wounds
  • Technically for proliferative phase of wound healing
  • Silicone dressing
  • Technically helps reduce excessive granulation tissue (limited evidence)
  • Can be left on for 3 to 4 days
  • Silver dressing for wounds that need granulating (limited evidence)
  • Can be left on for 3 to 4 days
• The granulation phase can be the itchy phase so protection of the wound may need to be improved in these cases e.g., fly masks for head wounds to prevent rubbing