Achilles Tendon Repair in Dogs Using the Semitendinosus Muscle: Surgical Technique and Short-Term Outcome in Five Dogs WENDY I. BALTZER, DVM, PhD, Diplomate ACVS and PAUL RIST, DVM, Diplomate ACVR Objective—To describe augmentation of primary Achilles tendon repair using suture with a sem- itendinosus muscle flap and report outcome in 5 dogs. Study Design—Prospective clinical study. Animals—Dogs (n ¼ 5) with Achilles tendon rupture (n ¼ 6). Methods—After tendon repair with #2 polypropylene in a 3-loop pulley suture pattern, the lateral one-half of the semitendinosus muscle was transected from the ischium, rotated distally then sutured with #2 polypropylene to the calcaneus in a 3-loop pulley pattern. The epitenon was sutured to the muscle flap fascia with interrupted sutures. All dogs had a bivalved cast for 2 weeks then a cranial splint for 2–6 weeks. Lameness scores (0 ¼ stands and walks normally to 4 ¼ non-weight-bearing lameness, plantigrade stance on affected pelvic limb) were determined every 2–3 weeks postoper- atively for 12 weeks. Outcome was determined from telephone questionnaire of owners. Results—Four had lameness scores of 0, the 5th had a score of 1 at 12 weeks. Three owners were very satisfied with outcome. Minor complications included cast sores (2 dogs), infection (2), and acute swelling (1); 1 major complication occurred (infection resulting in reoperation). Conclusions—Semitendinosus flap augmentation resulted in early return to function without pro- longed postoperative immobilization. Three dogs returned to full work/activity after repair. Clinical Relevance—Augmentation of primary Achilles tendon repair with a semitendinosus flap can be considered in dogs with chronic rupture but further investigation of the long-term outcome using this technique is needed. r Copyright 2009 by The American College of Veterinary Surgeons INTRODUCTION T HE ACHILLES tendon is comprised of 3 tendinous structures: the gastrocnemius tendon, the superficial digital flexor tendon, and the common tendon of the biceps femoris, gracilis, and semitendinosus muscles. 1 The tendon of the superficial digital flexor proximally lies cranial to the gastrocnemius then passes medially to the caudal aspect of the gastrocnemius tendon as it courses distally. The super- ficial digital flexor tendon continues distally after inserting on the tuber calcis to insert on the proximal caudal border of the second phalanges of digits II–V. 1 The most common cause of Achilles tendon rupture is reportedly acute trauma, such as laceration of the tendon resulting in complete transection of all of its components 2 resulting in a typical tarsus plantigrade stance in dogs with complete rupture. 3 Partial tendon ruptures, in which the superficial digital flexor remains intact, are thought to occur during exercise in large breeds or working/racing dogs. 4,5 When the gastrocnemius tendon has ruptured but the superficial digital flexor remains intact, the dog most commonly presents with hyperflexion of the tarsus and hyperflexion of the digits from contraction of the super- ficial digital flexor. 6 Besides blunt or sharp trauma, Achilles tendon injuries have been attributed in dogs and people to avulsion fracture of the calcaneus, chronic wear damage caused by repetitive stress, postmenopausal osteoporosis, exercise- Address reprint requests to Wendy I. Baltzer, DVM, PhD, Diplomate ACVS, Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, 105 Magruder Hall, 2979 NW Audene Dr, Corvallis, OR 97331. E-mail: wendy.baltzer@ oregonstate.edu. Submitted May 2008; Accepted November 2008 From the Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR. r Copyright 2009 by The American College of Veterinary Surgeons 0161-3499/09 doi:10.1111/j.1532-950X.2009.00565.x 770 Veterinary Surgery 38:770–779, 2009