Management of Muscle and Tendon Injury or Disease

Chapter 35

Management of Muscle and Tendon Injury or Disease

General Principles and Techniques

Muscle Contusion and Strains

General Considerations and Clinically Relevant Pathophysiology

Muscle contusions are caused by external trauma. An external blow disrupts fibril continuity and the vascular compartment, with subsequent hemorrhage into the interstitial space. Muscle strains are caused by overstretching or overuse. These injuries occur but are often difficult to recognize in small animals.

An injured muscle may cause considerable pain during normal body motion. Muscle has an intrinsic ability to heal by regeneration of myofibrils if the sarcolemmal cells survive and the endomysial connective tissue sheath is not destroyed. With mild contusions and strains, cells and the endomysial sheath are not destroyed, and their preservation allows complete healing. However, if the contusion is severe and causes extensive cell death and hemorrhage precluding muscle regeneration, healing occurs with fibrous interposition between muscle ends. Excessive scarring may impede muscle fiber regeneration and interfere with muscle contraction.

Compartment syndrome of muscles occurs when pressure increases within a nonextensible fascial compartment usually as the result of bleeding in the compartment following trauma. The increased pressure may cause irreversible damage to the muscle and nerves within the compartment. Compartment syndrome secondary to hemangiosarcoma has been reported in two dogs (Bar-Am et al, 2006; Radke et al, 2006).


Medical Management

The primary treatment for muscle contusion and strain is rest. Enforced rest with controlled activity is necessary for at least 3 weeks. If injury is recurrent or severe, longer periods of enforced rest may be necessary. If the muscle is not allowed to heal adequately, repeated injury is likely. Nonsteroidal anti-inflammatory drugs (NSAIDs) (see Table 34-4 on p. 1221) can be administered for the first 3 to 4 days, but restricted activity must continue even if lameness and pain disappear.

Surgical Treatment

When a severe contusion is recognized during surgical stabilization of a fracture, decompression of the muscle compartment can be achieved through incision of the epimysium (see p. 1377). Surgical treatment is necessary only if interstitial fluid accumulation causes sufficient pressure to compromise blood flow (i.e., compartment syndrome). Compartment syndrome has been diagnosed rarely in dogs and has not been reported in cats. Fibrotic contracture of the infraspinatus muscle may be a sequela of osteofascial compartment syndrome in dogs (Devor et al, 2006).

Surgical Anatomy

Skeletal muscle is made of long, cylindrical fibers encased within connective tissue sheaths (Fig. 35-2). Each individual fiber is enclosed within a sheath called the endomysium. Each fiber bundle is also enclosed within a sheath (perimysium), as is the entire muscle (epimysium). The connective tissue sheaths house blood vessels and nerve fibers that serve to integrate muscle contraction of individual fibers. Muscles are attached to bone by cordlike tendons or flat aponeuroses. The fascial compartment overlying the muscle group appears tight and congested with contusions, and the underlying muscle appears severely bruised and often protrudes from the incision through the fascial compartment.


Bar-Am, Y, Anug, AM, Shahar, R. Femoral compartment syndrome due to haemangiosarcoma in the semimembranosus muscle in a dog. J Small Anim Pract. 2006;47:286.

Devor, M, Sørby, R. Fibrotic contracture of the canine infraspinatus muscle: pathophysiology and prevention by early surgical intervention. Vet Comp Orthop Traumatol. 2006;19:117.

Radke, H, Spreng, D, Sigrist, N, et al. Acute compartment syndrome complicating an intramuscular haemangiosarcoma in a dog. J Small Anim Pract. 2006;47:281.

Ragetly, GR, Griffon, DJ, Johnson, AL, et al. Bilateral iliopsoas muscle contracture and spinous process impingement in a German Shepherd dog. Vet Surg. 2009;38:946.

Stahl, C, Wacker, C, Weber, U, et al. MRI features of gastrocnemius musculotendinopathy in herding dogs. Vet Radiol Ultrasound. 2010;51:380.

Muscle-Tendon Unit Laceration


Diagnostic Imaging

Standard craniocaudal and medial-to-lateral radiographs should be taken to determine whether foreign bodies or concurrent fractures are present. Mild swelling may occur in the area of chronic tendon lacerations. Ultrasonography helps localize the site of tendon injury and may differentiate partial from complete tendon rupture. Tendon injuries have a variable sonographic appearance depending on the severity of the trauma and the stage of healing. The normal ultrasound appearance of tendons depends on the incidence of the ultrasound beam. In a sagittal plane, the tendon or ligament will have a parallel, linear fiber alignment pattern that is hyperechoic. Damaged or torn tendons or ligaments will have disruption of the fiber alignment and edema, which appears as hypoechogenicity between fibers. In acute injury, the tendon is often enlarged because of the presence of edema, whereas with chronic injury, thickening of the tendon with focal areas of mineralization may be seen. A complete disruption may be identified by the presence of a hypoechoic band bordered by the retracted hyperechoic tendon ends.

Surgical Treatment

Muscular lacerations require appositional sutures supported with deeper stent sutures. If the laceration goes through the tendon, delicate manipulation and apposition with small-diameter suture are recommended.

Surgical Technique

Muscle Laceration

Thoroughly débride the wound edges to fresh, bleeding muscle (Fig. 35-3). Débride carefully to prevent excess removal of tissue, which makes apposition of the severed ends difficult. Place interrupted sutures in the outer muscle sheath around the circumference of the muscle. Support the appositional sutures with heavy stent sutures placed in a cruciate pattern.

Tendon Laceration

Delicately manipulate and débride the tendon ends. With small, flat tendons, use small-diameter, nonabsorbable material placed in a series as interrupted vertical mattress or cruciate sutures. For larger tendons, select the largest suture diameter that will readily pass through the tendon atraumatically. A locking-loop suture pattern is recommended (Fig. 35-4). Place each loop of the pattern in a slightly different plane (i.e., near-far, middle-middle, and far-near pattern). Alternatively, use a three-loop pulley or a Bunnell-Mayer, far-near, or near-far suture pattern. Use adjoining fascia to support the tendon appositional sutures.

Healing of Tendons and Muscles

Healing of tendons follows a pattern similar to that of other connective tissue. The inflammatory phase is characterized initially by neutrophils and later by mononuclear cells. Tendon injury is rarely isolated but exists in a zone with other wounded tissue. Unsuccessful attempts to isolate tendon healing from surrounding tissue have led to the concept of one wound, one scar. This implies that successful healing is dependent on activation of undifferentiated mesenchymal cells, which migrate into the wound. Mesenchymal cells produce the collagen and matrix that lend strength to the entire wound. The resultant scar unites the tendon ends, which remodel with collagen fibers oriented parallel to lines of stress. Strength is regained through the one-wound, one-scar principle, but function is regained through active and passive postoperative use of the limb.

Postoperative Care

After tendon repair, the limb should be immobilized for 3 weeks with the use of rigid external coaptation or external fixation with the joint positioned to release stress on the repaired tendon (see p. 1067). However, placement of an external fixator has not been demonstrated to significantly decrease strain in the Achilles tendon (Lister et al, 2009). When the splint is removed, the limb should be semi-rigidly immobilized for an additional 3 weeks with a heavy padded bandage or a half cast (i.e., one side of a split cast applied cranially or caudally to the limb). If an external fixator was used, it may be dynamized by the use of hinges or resistance bands. Hinges placed at the center of rotation of the joint can be adjusted to increase the range of motion and subsequently the tendon load. Elastic bands placed between the pins above and below the joint to replace the side bars allow partial loading of the tendon. After muscle repair, the limb should be immobilized for 5 days, followed by 4 to 6 weeks of protected activity. The use of platelet-rich plasma is under investigation as an aid in the healing of muscle and tendon in dogs (see Chapter 14).

Physical Rehabilitation

During immobilization, pulsed 3 MHz therapeutic ultrasound may aid in collagen repair. After immobilization for muscle or tendon lacerations, physical rehabilitation is vital to reverse the effects of immobilization on the other joints (Table 35-1). The animal should be gradually returned to normal activity; premature weight bearing will result in failure of the tendon to heal.


Return to normal function is expected if postoperative recommendations are followed (Worth et al, 2004). Failure generally is associated with allowing the animal to exercise before the tendon has completely healed.

Suggested reading

Kramer, M, Gerwin, M, Michele, U, et al. Ultrasonographic examination of injuries to the Achilles tendon in cats and dogs. J Small Anim Pract. 2001;42:531.

This article reports the ultrasonographic findings of 42 dogs and 7 cats with Achilles tendon injuries. Ultrasonography was shown to be an excellent diagnostic method for these injuries and a means of monitoring healing of the structure.

Lamb, CR, Duvernois, A. Ultrasonographic anatomy of the normal canine calcaneal tendon. Vet Radiol Ultrasound. 2005;46:326.

This article provides a detailed description and pictures of normal structures of the calcanean tendon as visualized by arthroscopy.

Millis, DL, Levine, D, Taylor, RA. Canine rehabilitation and physical therapy. Philadelphia: Saunders; 2004.

This book is a comprehensive guide to physical therapy and rehabilitation for dogs. It provides detailed descriptions of rehabilitation techniques and explains how they are applied for specific diseases.

Moores, AP, Comerford, EJ, Tarlton, JF, et al. Biomechanical and clinical evaluation of a modified 3-loop pulley suture pattern for reattachment of canine tendons to bone. Vet Surg. 2004;33:391.

This paper describes an alternative method for repair of tendon lacerations or avulsions that may be superior to the locking-loop pattern. It may be more appropriate for use in some clinical cases.

Moores, AP, Owen, MR, Tarlton, JF. The three-loop pulley suture versus two locking-loop sutures for the repair of canine Achilles tendons. Vet Surg. 2004;33:131.

This study reports that the three-loop pulley pattern is more resistant to gap formation than two locking-loop sutures. Resistance to gap formation is important in rapid healing of tendon injuries.

Worth, AJ, Danielsson, F, Bray, JP, et al. Ability to work and owner satisfaction following surgical repair of common calcanean tendon injuries in working dogs in New Zealand. N Z Vet J. 2004;52:109.

This article reports that surgical treatment of calcanean tendon injury combined with rigid immobilization resulted in a satisfactory outcome in 7 of 10 working dogs. A screw and cast method of immobilization was supported by the results of this study.

Muscle-Tendon Unit Rupture

General Considerations and Clinically Relevant Pathophysiology

Muscle ruptures are caused by powerful contraction during forced hyperextension of the muscle-tendon unit. This injury is seen most often in sporting and performance athlete breeds, such as Racing Greyhounds. The injury most commonly encountered is partial or complete rupture of the Achilles tendon. Injury of the Achilles mechanism may arise from an acute traumatic episode or from chronic progressive stretching of the tendon. Acute injuries often occur secondary to a fall or a penetrating wound. Conversely, chronic injuries are often secondary to overuse that causes chronic stretching and deterioration of the tendon. Chronic injuries more commonly occur in sporting breeds (e.g., field trial dogs and bird hunting dogs) and are often bilateral. Bilateral chronic degeneration of the common calcanean tendons is relatively common in Doberman Pinschers, although the cause is unknown.

Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Management of Muscle and Tendon Injury or Disease

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