Infraspinatus contracture and bursal ossification
The infraspinatus muscle arises from the infraspinatus fossa of the scapula, crosses the shoulder joint, and inserts on the
humerus at the greater tubercle just distal to the supraspinatus insertion point.6 This muscle has many functions for the shoulder—flexion and extension, passive stability, and lateral rotation of the forelimb.6 Labrador retrievers and other breeds may develop tendon and bursal ossification of the infraspinatus muscle.9,21 One of the first reports of mineralization of the infraspinatus tendon was in Labrador retrievers; progressive lameness
was reported to develop in this breed.21,22 Affected dogs may show no clinical signs, or pain may be present on palpation of the tendon craniolaterally on the shoulder
joint, and the dogs may exhibit progressive lameness.21 Diagnostic ultrasound may be used to visualize the damaged tendon and to monitor healing after treatment.23
Some dogs respond to conservative management with rest and corticosteroid injection into the bursa or tendon, while others
require surgical resection and release of the tendon. As many as 50% may not fully recover from the condition.21 During arthroscopy, pathology is often noted in other shoulder structures such as the medial glenohumeral ligament or biceps
brachii tendon, and these problems may contribute to the patient's lameness and dysfunction.24 The prognosis for return to previous levels of athletic ability in animals with this condition alone is unknown since it
frequently occurs with other shoulder pathologies.
Teres minor myopathy
The teres minor muscle flexes the shoulder joint and can slightly rotate the forelimb medially. It arises from the infraglenoid
tubercle of the scapula and crosses the shoulder to insert on the lateral diaphysis of the humerus.25 Teres minor myopathy results in a consistent lameness with pain on extension of the shoulder.25 When tissue and muscle just caudal to the acromial process are palpated, sometimes a firm band of tissue and shoulder pain
are evident. This condition can be diagnosed by ultrasonographic examination of the tendon and muscle. Conservative management
may only be effective early in the course of the disease. If the condition is chronic, surgery is needed to resect the fibrous
tissue and tendon.25
Medial shoulder instability
4. A craniocaudal radiograph of the shoulder showing medial glenohumeral instability in a dog.
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Medial glenohumeral joint laxity, or medial shoulder instability, may be a frequent but underdiagnosed cause of forelimb lameness
in athletic dogs.26,27 Careful examination of a sedated dog can identify instability, with abduction angles greater than 40 degrees indicative
of pathologic instability (Figure 4).28 Definitive diagnosis can be difficult with stress-view radiographs of the shoulder in abduction since the radiographs are
sometimes difficult to interpret.28,29 Secondary changes can be seen with radiographs and are indicative of osteoarthritis, but definitive diagnosis of medial
shoulder instability is based on MRI or arthroscopic visualization of the subscapularis tendon, medial glenohumeral ligament,
and medial joint capsule pathology.30,31 The weightbearing lameness seen with this instability is often intermittent and occurs after physical activity.
Numerous treatment methods have been reported, including conservative management with hobbles and cage rest, thermal capsulorrhaphy,
prosthetic medial ligament repair, biceps brachii tendon transposition, and subscapularis tendon imbrication.27,32-34 Conservative management has been reported to have a good to excellent outcome in 25% of dogs, whereas surgical treatment
has improved outcomes, with 85% to 93% of dogs attaining good or better function.27,32 However, after surgery, some dogs may have continued lameness.27,32,34 Rehabilitation may improve the function and performance of some dogs after recovery from surgery. In severe cases of instability,
arthrodesis may be performed, but the dog cannot continue to compete at the same level as before the injury.32
Carpal injury
In the carpus, sporting dogs can incur flexor carpi ulnaris tendinopathy or avulsion, superficial digital flexor tendon elongation
(flyball and agility dogs), medial and lateral collateral ligament rupture, abductor pollicis longus tenosynovitis (earthdogs),
palmar ligament hyperextension injury (flyball and dock dogs), radial carpal bone luxation or fracture, styloid process fracture
and joint instability, or carpal osteoarthritis (racing greyhounds).4,25,35-37
Tendinopathy and even avulsion of the insertion of the flexor carpi ulnaris from the accessory carpal bone can occur in sporting
dogs, especially those working on uneven terrain and hard surfaces. In dogs, the injury presents with what looks like hyperextension
of the carpus and is differentiated from tears of the flexor retinaculum by palpating distal to the accessory carpal bone
(which should palpate normally if the flexor carpi ulnaris is strained or avulsed). If the flexor retinaculum is torn, the
dog will stand with the affected limb hyperextended, and there will be swelling or enlargement of the soft tissues on the
palmar aspect of the carpus distal to the accessory carpal bone.38
Treatment consists of surgical repair of the avulsion by using a three-loop pulley suture technique (usually with a bone tunnel
created in the accessory carpal bone), splinting for three weeks, and then rehabilitation for a gradual return to function.38 Treatment of strains or tendinopathies can be conservative with laser or shockwave therapy used to stimulate healing of
the insertion and increase the strength of the healed fibers.39-41 During therapy and for three weeks after treatment, the dog should be maintained in a splint or orthotic brace to support
the healing structures.
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