Tendon injuries are unfortunately a common occurrence in equine practice. Work or competition at speed, on unlevel ground, or over jumps increases the risk of sustaining an injury to the flexor tendons. When at speed or landing after a jump the fetlock joint is over-extended and the tendon fibres can tear or rupture. Tendon fibres also begin to degenerate with age, weakening the tendon and making injury more likely as the horse gets older.
Tendon injuries range from mild to severe and present with a varying degree of lameness, inflammation, heat and swelling over the affected site. Using ultrasound the extent and the proportion of the fibres damaged can be identified as a “hole” within the tendon.
Traditionally the only treatment for tendon injuries has been an extended period of rest (frequently 6-12months) with no guarantee of outcome or prognosis. The tendon initially bleeds into the “hole” and then newer reparative collagen fills in the hole. However this reparative collagen is functionally inferior. This often results in recurrence of the injury when the horse is returned to their previous level of performance.
Recent developments in regenerative medicine have given veterinarians access to superior therapies when treating tendon lesions in horses.
PRP- Platelet Rich Plasma
Platelets are found in the bloodstream and are essential for blood clotting. They are also an integral part of the early repair process at sites of injury by providing a scaffold for the repair and releasing growth factors. In tendon lesions, these growth factors aid healing by encouraging proliferation and maturation of tenocytes (tendon cells) as well as improving the collagen organisation, thus producing a stronger tendon once healed. These growth factors also aid in stimulating new blood supply to the injured area, which assists with healing as blood supply to the tendons is poor in the normal horse.
PRP is obtained by taking a 60ml blood sample from the horse’s neck and spinning the platelets out by centrifuge. The PRP is then injected in to the site of injury of the tendon, under ultrasound guidance and local anaesthetic. The leg is then bandaged and strict confinement in a stable for up to 4 weeks after which a tailor made gradual exercise program can begin, as well as determining the progress of the healing with regular repeat ultrasound examinations.
PRP is can be used in both recent tendon and ligament injuries as well as injuries that have failed to respond to rest and controlled exercise. Most injuries will only require a single injection of PRP.
Stem cells are cells that are found in bone marrow and fat that are undifferentiated and have the ability to differentiate into any type of tissue, including tendon, bone, ligament and cartilage etc. They have unlimited potential to replicate and produce growth factors, similar to platelets.
Stems cells can be harvested from the bone marrow within the sternum (breastbone) or from fat. Bone marrow stem cells are collected and then sent to a laboratory for culture to increase their number. This process takes about 3 weeks, is expensive and is no longer available.
Stem cells can also be harvested from fat deposits. This is a straight forward procedure that is completed under sedation and local anaesthetic. Between 20-40 grams of fat is removed from the side of the tail head and processed in the lab before injecting into the “hole” in the tendon under ultrasound guidance and local anaesthetic.
Stem cells collected from fat deposits have been shown to have stronger regenerative powers than stem cells from bone marrow and are collected in higher numbers, therefore do not need to be cultured, so that collection, processing and injection of the stem cells can all be done in one day. There has been very few adverse affects with using the stem cells, and less than 0.5% local tissue reactions after injection have been reported.