Injuries in sporting dogs--from agility to flyball to field trials (Proceedings)

One of the most common injuries in sporting dogs involves the shoulder. This is especially true for agility dogs. Common problems include biceps brachii tenosynovitis, supraspinatus insertionopathy, infraspinatous contracture and bursal ossification, teres minor myopathy, medial glenohumeral ligament instability, as well as trauma, resulting in fracture, osteoarthritis, or luxation. Injuries to the elbow commonly encountered include luxation, collateral ligament rupture, fragmented medial coronoid process, and osteoarthritis of unknown cause.

In the carpus, sporting dogs can incur flexor carpi ulnaris avulsion, superficial digital flexor tendon elongation (flyball and agility), collateral ligament rupture, abductor pollicus longus tendosynovitis (earthdogs), palmar ligament hyperextension injury (flyball and dock dogs), radial carpal bone luxation or fracture, styloid process fracture and joint instability, and carpal bone fractures (racing greyhounds).

In the hind limb, hip dysplasia and osteoarthritis of the hip, stifle, and tarsus are not uncommon and usually a consequence of preexisting developmental orthopedic disease. Sporting dogs can also develop gracilis/semitendinosis myopathy and contracture, iliopsoas muscle trauma leading to femoral neuropathy, cruciate ligament rupture, patellar tendonitis, long digital extensor tendonitis, and gastrocnemius head or popliteal muscle avulsion injury. Chronic injuries of the hind limb can include Achilles tendon rupture, iliopsoas myopathy, partial cruciate ligament rupture and lumbosacral disease.

Bicipital tenosynovitis is usually a chronic injury of the forelimb that will be discussed in another lecture. Supraspinatus insertionopathy involves the supraspinatus tendon becoming torn or strained over time. This chronic injury cannot result in any lameness until there is ossification of the tendon and impingement on the biceps tendon. On exam you will see pain on flexion of the shoulder and may get biceps tendon pain as well. Calcification of the tendon can be present and never cause any clinical signs. The decision to treat should be based on clinical presentation of the dog. Treatment can be aimed at surgical removal of the ossified body, however recurrence is common.

Extracorporeal shock wave therapy can be used to resolve the condition along with underwater treadmill therapy and exercises to restore shoulder function and resolve pain associated with the condition. A tendonopathy of the supraspinatus muscle does not have calcification present but there is chronic pain present on flexion of the shoulder and palpation of the tendon. An MRI is needed to identify this soft tissue injury or arthroscopy can sometimes be used to see the tendon abnormality. For athletes, we recommend rehabilitation as well as teaching the dogs to perform swimmers turns to prevent re-injury. 

Labrador retrievers may develop tendon and bursal ossification of the infraspinatous muscle. There may be no clinical signs or pain may be present on palpation of the tendon. Some dogs respond to conservative management with rest and corticosteroid injection into the bursa while others require surgical resection of the mineralizations. As many as 50% may not fully recover from the condition. On arthroscopy, one can see pathology in other shoulder structures such as the medial glenohumeral ligament or biceps tendon and these may be contributing to disease.

Teres minor myopathy results in a consistent lameness with pain on extension of the shoulder. Sometimes the caudolateral shoulder has a firm band of tissue that is the fibrosing muscle but this may not be present. Diagnosis can be made by ultrasound examination of the tendon and muscle. The use of conservative management may only be effective early in the course of the disease and if chronic, surgery is needed to resect the fibrosing tissue.

Strains of the teres major occur in dogs participating in flyball sports. There is pain on extension and abduction of the shoulder and limb. With rest and NSAIDS the condition will often improve but recurrence is not uncommon. Therapeutic ultrasound or laser may help resolve the problem if recurrence is suspected. Adequate healing following the rest period is needed and therefore a slow return to activity is recommended with gradual increases in passive and active range of motion exercises over time. Adequate strength is not returned to muscles for at least 6 weeks following the injury.

Avulsion of the insertion of the flexor carpi ulnaris from the accessory carpal bone is a rare condition that presents with what looks like hyperextension of the carpus and is differentiated from palmar retinacular tears by palpating distal to the accessory carpal bone (which should palpate normally if the flexor carpi ulnaris is avulsed). Treatment consists of repair of the avulsion using a 3-loop pulley suture technique (usually with a bone tunnel created in the accessory carpal bone), then splinting for 3 weeks then rehabilitation for a gradual return to function.

Superficial digital flexor elongation results from stretched tendons following repeated straining of them, however, lameness may not always be apparent but decreased performance can result from this injury. Trainers may call this condition “bowed tendons”. Surgery to resect the lengthened portion of the tendon and to shorten the tendon by suturing the ends following the resection will resolve the problem but the dog may have a flat toe following surgery. The flat toe does not interfere with the performance of the dog.7

Injury to the iliopsoas muscle is not an uncommon occurrence as was once thought. Dogs that are infrequently active and over extend themselves can receive this injury as well as athletes. The dogs may not be lame but show signs of decreased performance, difficulty rising, and a shortened stiff gait in the hind limbs. In severe cases they may have signs of femoral nerve paralysis and drag the limb. A sprain of the muscle will be mildly painful on palpation but when there has been hemorrhage into the muscle fibers, severe pain can be present due to compression and inflammation of the closely related femoral nerve. Ultrasound can diagnose the injury and treatment of mild cases often involves therapeutic ultrasound, passive range of motion exercises, and a gradual return to activity. If this therapy fails, surgical resection of the iliopsoas tendon can resolve the clinical signs.

Avulsion of the gastrocnemius muscle at its head results in an acute nonweight-bearing lameness and the hock may be hyperflexed if the dog tries to bear any weight on the limb. On radiographs, you may visualize displacement of the fabella at the stifle joint distally. The treatment involves surgical reattachment of the muscle head to the femoral supracondyle and restriction of stifle extension for the next 3 weeks postoperatively. The lameness will resolve but dogs rarely return to their previous performance level.

The popliteal muscle functions to flex the stifle and internally rotate the tibia. When avulsion occurs, it is at the lateral femoral condyle and there will be pain present on extension of the stifle as well as when the caudal aspect of the stifle is palpated. On radiographs, the popliteal sesamoid at the caudal aspect of the stifle joint will be displaced distally. Surgery to reattach the muscle to the lateral femoral condyle is recommended, but like gastrocnemius avulsion, return to peak performance is unlikely.

Achilles tendon rupture

The Achilles tendon is the common calcaneal tendon and is most commonly injured by laceration in both dogs and cats. Chronic injuries are increasing in frequency and therefore will also be discussed here. Acute injuries to the common calcaneal tendon are most commonly due to lacerations and have occurred within the last 48 hours prior to presentation. Subacute injuries have occurred at any time between 2 and 21 days and chronic injuries are older than 21 days.

The pathogenesis of subacute or chronic injuries not associated with laceration of the tendon is not well understood. Progressive rupture of the Achilles tendon can develop over time with injury to the gastrocnemius component most commonly affected. Suspected initiators of such chronic ruptures have included steroid and fluoroquinolone administration. Most veterinary cases are in large breed, active dogs and may be related to chronic repetitive injury during exercise. The diagnosis is made on physical examination and confirmed with radiography and ultrasound.

Examination may reveal changes in posture with hock hyperflexion, with or without excessive digit flexion, and potentially a plantigrade stance. Palpation of the tendon may reveal thickening, thinning, or a normal sized tendon. Ultrasonography findings may include signs of hemorrhage, fiber disruption, and scar tissue formation. Normal tendon diameter as seen on transverse ultrasound images has been established at 2.4 to 3.2 mm. Surgical treatment is preferred over conservative medical management in cases of complete gastrocnemius tendon rupture. In both human and small animal cases, primary repair of the tendon is performed and most commonly involves one of two different suture techniques: the three-loop pulley or the locking-loop suture pattern.

Both patterns have superior strength over other patterns used in the past but the locking loop may have improved resistance to gap formation with loading of the tendon. A gap of less than 3 mm allows strength and stiffness to increase with a decrease in repair failure during the first 6 weeks following surgery. All sutures involved in the primary repair are recommended to be nonabsorbable monofilament suture in order to allow gliding motion along the suture but sustain re-apposition of the tendon ends for at least 3 weeks.

Augmentation of the primary repair is controversial. Acute lacerations or injuries of less than 48 hours duration usually are not augmented. Subacute or chronic lacerations are most often augmented with various implants or tissues intended to remain permanently at the repair site. Biological implants include free fascia lata graft, porcine small intestinal submucosa, or the semitendinosus muscle.

Injection of the tendon repair with concentrated platelet gel has been advocated to speed healing post-operatively, however, it is ineffective without early controlled rehabilitation.. Porcine small intestinal submucosa has been used experimentally in dogs and facilitates complete tendon healing within 90 days of the surgically created Achilles tendon defect. Protection of the repair early in the healing process is a must. Additional support can be from casts, external skeletal fixators, splints, or calcaneal-tibial bone screws. All of these methods provide relief of tension on the repair for 3 weeks to 3 months.

Immobilization for longer than 4 weeks will result in deleterious effects on the joints, some of which can be permanent.  In addition, early mobilization of the joint improves the healing process and augments the tensile strength of the tendon repair.  The average length of time that some form of immobilization is needed is about 10 weeks, however, most surgeons decrease the amount of support incrementally over that time. The dog may achieve a stable functional hind limb following repair but return to competition is less likely. A study from New Zealand determined that only 7 out of 10 dogs return to full or substantial levels of work following healing and 29% of those have moderate persistent lameness.

New methods to enhance and speed healing of tendon repairs are being investigated. Low energy shock wave therapy may enhance neovascularization of the bone-tendon junction in dogs. Ultrasound therapy may be able to accelerate healing and tendon maturation in dogs as well. While no clinical studies exist, future developments and methods of postoperative care in the future may improve the functional outcome in small animals with Achilles tendon injuries.

Collies and shelties are becoming increasingly popular in flyball and agility sports and are prone to development of superficial digital flexor tendon luxation. The luxation occurs at the level of the calcaneal bone where the retinaculum ruptures. The dog will be painful and lame in the hind limb and may have its toes elevated off the floor when standing on the affected limb. The diagnosis is made by palpation of the area where the tendon can be replaced and luxated again similar to a luxating patella. Treatment is with surgical repair of the retinaculum and a gradual return to activity with rehabilitation.

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