Shoulder Joint Ligament and Tendon Conditions in Cats

Bicipital Tenosynovitis, Brachii Muscle Rupture, and Supraspinatus Avulsion in Cats

A ligament is a band of connective or fibrous tissue that connects two bones or cartilage at a joint, and a tendon is a band of connective or fibrous tissue that connects a muscle to a bone. The shoulder joint is a “ball-and-socket” joint that is held together and supported by ligaments and tendons. In four legged animals, the shoulder is made up of the scapula/shoulder blade bones, and the humerus/upper bone of the front leg. Conditions that affect the tendons and ligaments of the shoulder will be apparent in a cat's ability to walk, run and jump.

Abnormalities of the ligaments and tendons in the shoulder are rare in cats, they are more commonly associated with large dogs and working dogs. However, there have been occasions in which shoulder disorders have been reported in cats. There is no prior indication that would necessarily dispose a cat to shoulder joint problems.

Symptoms and Types

• Symptoms will depend on the severity and long-term nature of the disease
• A decrease in muscle mass is a consistent finding for all conditions
• Bicipital tenosynovitis (an inflammation of the tendon and surrounding sheath of the biceps tendon – at the front of the shoulder blade)
  • Onset is usually subtle
  • Often of several months’ duration
  • Trauma to the limb or shoulder may be the inciting cause
  • Subtle, intermittent lameness that worsens with exercise
  • Short and limited swing-phase of gait owing to pain on extension and flexion of the shoulder
  • Pain inconsistently demonstrated on manipulation of shoulder
• Rupture of the tendon of the biceps brachii muscle (upper limb)
  • Signs similar to bicipital tenosynovitis
  • May have sudden (acute) onset due to a known traumatic event
  • Usually subtle, long-term (chronic) lameness that worsens with exercise
  • Mineralization of the tendon of the supraspinatus (shoulder joint) muscle — onset is usually subtle
  • Long-term (chronic) lameness that worsens with activity
• Forcible separation (known as an avulsion) or fracture of the tendon of the supraspinatus muscle (tendon that connects the scapula/bone of the shoulder blade with the humerus/bone of the upper limb)
  • Signs are similar to mineralization of the supraspinatus tendon.
  • Deterioration and scarring (known as fibrotic contracture) of the shoulder muscle — usually sudden (acute) onset, occurring during a period of intense outdoor exercise (such as hunting).
  • Shoulder lameness and tenderness gradually disappears within two weeks
  • Left untreated, condition results in long-term (chronic), persistent lameness
  • Decrease in muscle mass of the infraspinatus muscle (muscle atrophy)
  • When patient is walking, lower limb swings in an arc away from the body, as the paw is advanced

Causes

• Direct trauma to shoulder
• Repetitive strain injury (indirect trauma) is the most common cause
• Overexertion and/or fatigue
• Poor conditioning before performing athletic activities (i.e., lack of previous exercise, obesity, or inappropriate preparation)

Diagnosis

X-rays will be needed to determine what is wrong with the shoulder. Ultrasound and magnetic resonance imaging (MRI) may help identify muscle injuries, bicipital tenosynovitis, and rupture of the biceps tendon. It is also useful for determining the location of calcium densities near the intertubercular groove, where the long head of the biceps meets the upper part of the humerus. A joint tap and analysis of fluid from the joint will help identify intra-articular (within the joint) disease. An arthroscopic exploration of the shoulder joint will help diagnose bicipital tenosynovitis, rupture of the biceps tendon, and will confirm or rule out intra-articular disease. This method of diagnostics is performed using an arthroscope, a specially equipped endoscope, which is a tubular device that can be inserted into the joint in order to remove fluid, tissue, or other material for analysis. It includes a camera for visual inspection, and can be outfitted with tools for removal of samples, and for treating the cavity or internal structure.

Treatment

If the disease is severe and long-term your cat will need to be hospitalized for surgical intervention. If the condition is not severe, your cat may be treated on an outpatient basis, especially if the shoulder joint problem was found early.

With bicipital tenosynovitis (inflammation of the tendon and surrounding sheath of the biceps tendon), there is a 50-75 percent chance of success with medical treatment. Surgery is usually required when there is evidence of long-term (chronic) changes and failure to response to non-invasive medical management. Rupture of the tendon of the biceps muscle generally requires surgery. Mineralization of the tendon of the shoulder muscle may be an incidental finding. This condition may require surgery after excluding other causes of lameness and attempting medical treatment. Forcible separation (avulsion) or fracture of the tendon of the shoulder muscle often requires surgery because of persistent bone-fragment irritation of the tendon. Deterioration and scarring of the shoulder muscle requires surgery.

Ice packing (known as cryotherapy) immediately following surgery can help to reduce inflammation and swelling at the surgical site. It will need to be performed five to ten minutes every eight hours for three to five days after surgery, or as directed by your veterinarian. Regional massage and range-of-motion exercises can improve flexibility and decrease loss of muscle mass (muscle atrophy) after the initial recovery period. Your veterinarian will advise you on when you should begin physical therapy with your cat.

Following surgery, how much activity your cat can participate in depends on the procedure performed; your pet's veterinarian will provide instructions regarding postoperative activity and restrictions. Medical treatment will require strict confinement for four to six weeks. You may need to enforce a strict period of cage rest, with a liter box kept close by so that your cat does not need to exert itself. It is important to follow your veterinarian's recovery protocols closely to avoid a recurrence or worsening of your cat's physical health. A premature return to normal activity will likely worsen signs and lead to a long-term (chronic) condition.

Weight control may need to be a part of your cat's long term care as well, so that excess pressure on the limb does not aggravate the tendons. Depending on your cat's starting weight, your veterinarian may recommend a strict diet for weight loss, or merely a maintenance diet to prevent weight gain. 

Living and Management

Most patients require a minimum of one to two months of rehabilitation after treatment. Medically managed bicipital tenosynovitis is often successful after one or two treatments in 50-75 percent of cases, with no long-term (chronic) changes. Surgically treated bicipital tenosynovitis has good to excellent results in 90 percent of cases. Recovery will need to be taken slow, with gradual increases of physical movement. Full function may take two to eight months.

Surgically treated rupture of the tendon of the biceps muscle has a good to excellent prognosis; more than 85 percent of patients show improved return to function. Surgically treated mineralization of the tendon of the supraspinatus muscle has a good to excellent prognosis; recurrence is possible, but uncommon. Surgically treated forcible separation (avulsion) or fracture of the tendon of the supraspinatus muscle has a good to excellent prognosis; recurrence is possible, but uncommon. Finally, surgically treated deterioration and scarring (fibrotic contracture) of the infraspinatus muscle has a good to excellent prognosis; patients uniformly return to normal limb function with appropriate recovery time and physical therapy.

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