Anatomy of the Shoulder:
The shoulder joint or glenohumeral joint, consists of the upper arm bone (humerus) fitting into a part of the shoulder blade called the glenoid. A group of muscles and tendons called the rotator cuff keep the humerus in place. The shoulder blade, or scapula, meets the collarbone (clavicle) at a second joint called the acromioclavicular joint. Both joints are susceptible to arthritis.
Types of arthritis:
Osteoarthritis: often found in patients over the age of 50, it results from the breakdown of cartilage surrounding the bones, causing the bones to rub against each other.
Rheumatoid arthritis: an autoimmune disorder involving the patient’s own immune system attacking the synovium of the shoulder joints. The synovium lines the joints and acts as a lubricant. Attack of the synovium causes it to swell and leads to joint stiffness.
Posttraumatic Arthritis: arthritis that develops after an injury to the shoulder.
Rotator Cuff Tear Atrophy: tears in the rotator cuff may result in destabilization of the humerus and rubbing of the humerus against the acromion. Constant friction between the bones may result in arthritis.
Avascular Necrosis: occurs when the blood supply to the humerus is disrupted, leading to the death of bone cells, degradation, and collapse of the humerus. Eventually, cartilage surrounding the humerus becomes damaged, leading to arthritis. At later stages, collapse of the humerus may also damage the glenoid.
Symptoms of arthritis: pain in the side or back of the shoulder or the top of the shoulder that travels up the side of the neck. Pain may be exacerbated by certain movements or experienced at night. Grinding or clicking may also be heard.
Diagnosis of shoulder arthritis:
Physical examination: during examination of the shoulder, the physician will look for muscle weakness, tenderness to the touch, pain with pressure, signs of injury and patient history of shoulder injuries, the sound of grinding or crepitus with movement, as well as any limitations to movement with and without the assistance of the examiner.
X-rays: radiographic imaging is often used to assess shoulder arthritis. The examiner looks for joint space narrowing as well as the formation of bone spurs or osteophytes. CT scans may be used to localize defects to the cartilage and MRI scans can be used to assess subtle changes in cartilage as well as the presence of fluid inside the bone that suggests advanced cartilage involvement.
Conservative treatment of osteoarthritis: common treatment options involve rest and activity modification, physical therapy, NSAIDs to reduce inflammation and pain, steroid injections to the shoulder, heat, icing, and dietary supplements such as glucosamine and chondroitin sulfate. Patients with rheumatoid arthritis may be prescribed methotrexate by their rheumatologist.
Surgical Treatment: if conservative treatment fails, patients may elect to proceed with surgical treatment. Shoulder surgeries often utilize an arthroscope, a small camera inserted into the shoulder joint that will display images of the inside of the shoulder on a monitor. This allows for a less invasive procedure as the incisions are smaller in comparison to open surgeries.
Surgical treatment most often involve the following:
Total shoulder arthroplasty: a shoulder replacement removes damaged areas of bone and replaces them with parts made of metal and plastic (implants). The glenoid is often replaced with a plastic cup and the humerus is replaced with a metal ball that recreates the shape of the shoulder joint.
Reverse total shoulder arthroplasty: the metal cup is attached to the humerus instead of the glenoid and ball is attached to the glenoid. This reversal in natural shoulder anatomy leads to the involvement of muscles outside of the rotator cuff (i.e. Deltoid) during arm and shoulder movement, making this treatment effective for patients with rotator cuff injuries. Patients with previously failed total shoulder arthroplasties (i.e ongoing pain after surgery and limitations to arm lifting) may also proceed with this option.
Depending on the quality of the patient’s bones, the ball with stem and plastic socket components of arthroplasty may be either pressed into the bone or cemented in. Patients with soft humeral components, poor glenoid cartilage, good quality glenoid sockets and rotator cuffs generally have the components implanted with cement.
Surgical Recovery: Patients are immobilized with a sling 2-6 weeks after surgery. Most can return home from hospitalization one to three days postoperatively. NSAIDs and opioids may be prescribed for short-term pain management. Gentle physical therapy and a home exercise program may be initiated shortly after surgery in order to improve shoulder strength and flexibility. Patients will be able to perform simple daily activities within 2 weeks and drive from 2 to 6 weeks postoperatively.