Vinnie was a 22-year-old Thoroughbred Cross gelding that developed an unusual gait anomaly during the spring of 2015. His gait deficit was pathognomonic for fibrotic myopathy of the right semitendinosis (hamstring) musculature.
pa•thog•no•mon•ic: A symptom that is so distinctively characteristic or indicative of a particular disease or condition it can be used to make a diagnosis.
Vinnie's owner suspected that he had right hind (RH) fibrotic myopathy based on his gait characteristics in that limb; she submitted a video clip to confirm her suspicions before scheduling an appointment for treatment.
Massage therapy of the right hamstring musculature had previously been implemented with some success, but Vinnie's gait deficit remained very obvious.
Vinnie on 11 March 2015, Just Before Surgery
Once the owner's tentative diagnosis was confirmed, Vinnie was scheduled for surgery. The procedure was performed in a local barn with Vinnie standing, sedated and locally anesthetized.
Learn more about the physiology, diagnosis and treatment of FIBROTIC MYOPATHY in the horse HERE.
Transecting (cutting) the fibrotic (scarred) portion of affected muscle tissue effectively removes its "fixed" attachment between the tuber ischii of the pelvis and the proximal tibia, thereby leaving only its "stretchable" attachment. Once the fibrotic tissue has been disengaged, the horse should be able to extend the pelvic limb normally and without restriction.
Varying amounts of tissue can be affected depending on the case. The percentage of fibrotic tissue relative to normal tissue is discerned prior to surgery. This information is obtained through careful clinical and/or ultrasonographic examination.
In some cases, supplemental and/or alternate tissue(s) are affected and also require transection. Postoperative recommendations will usually be commensurate with the type, location and amount of tissue operated.
At The Atlanta Equine Clinic, we prefer to perform surgery AFTER the fibrotic (scar) tissue has had ample time to mature, organize and finish contracting. This process generally takes around 90 days to complete in most horses. These (expected) physiologic consequences of muscle injury would counteract the positive effects of surgery if they were to occur postoperatively (after-the-fact). Accordingly, we would observe an inferior response to treatment.
In most cases of pelvic limb fibrotic myopathy, the medial head (inside portion) of the semitendinosis muscle is the only (or primary) structure involved. Preoperative clinical examination of Vinnie revealed that the entire medial (inside) head and approximately 60% of the main head of his right semitendinosis muscle was affected. Of course, transecting too much tissue would result in loss of function of the muscle and associated limb.
The semitendinosis is one of the hamstring muscles. It helps to extend (straighten) the hip joint and flex (bend) the stifle joint. It also helps medially rotate the tibia on the femur when the knee is flexed and medially rotate the femur when the hip is extended.
The medial head and approximately 50% of the main head of the right semitendinosis muscle was transected as treatment for Vinnie's fibrotic myopathy. Approximately 10% of fibrotic tissue was not transected so as to avoid crucial loss of muscle function. Surgery was performed through a linear incision approximately 1 inch (2.5 cm) in length.
Systemic antibiotics (Penicllin) and antiinflammatories (Phenylbutazone) were administered prior to the surgery. A Tetanus Toxoid booster was not administered since Vinnie was up-to-date on his inoculations.
The incision was closed in two layers: a) vertical mattress sutures were placed to alleviate tissue tension and b) staples were implemented to directly appose the tissue edges. Both required eventual removal by the primary veterinarian.
Vinnie's Incision Immediately Following Closure
Vinnie's Postoperative Care
Vinnie was stall-rested (only) for 5 days, then stall-rested with unlimited handwalking for another 5 days.
After 10 days, very small paddock rest with continued handwalking was permitted for another 20 days. Walking up and down hills was encouraged at this point to help to stretch tissue associated with and/or in the vicinity of the injury site. Our goal was produce a better overall functional result.
Training/light exercise and full turnout was resumed in 30 days.
Daily application of a warm or hot compress was recommended help to reduce swelling. The incision area was gently cleaned with warm water and soap as desired.
Sutures and staples should were removed 18-21 days after surgery.
Massage therapy of the hamstring musculature was resumed at the time of suture removal.
1) Phenylbutazone - Two grams were administered orally once daily in the morning for 5 days.
2) Trimethoprim Sulfamethoxazole - Fifteen tablets were administered orally twice daily (starting the evening of surgery) for 14 days.
We suggested reducing the carbohydrate portion and increasing the fat content of Vinnie's feed to make his stall confinement more tolerable while maintaining a consistent caloric intake. Click HERE for more information.
CORRECTIVE TRIMMING/ SHOEING
Vinnie's pelvic foot angles were increased and his breakover was quickened to facilitate early postoperative rehabilitation (temporarily). A normal trimming/ shoeing package was resumed after one cycle.
In many cases, an immediate improvement in gait is observed following surgery. Maximum semitendinosis muscle relaxation typically occurs within 14-21 postoperative days.
Vinnie on 12 March 2015, The Day After Surgery
Vinnie 2 Weeks After Surgery