Anatomy and Description
The shoulder is composed of your humerus (upper arm bone), scapula (shoulder blade), and clavicle (collar bone). It is a ball-and socket joint meaning there is a ball (top of the humerus) that fits into a shallow socket located in your shoulder blade known as the glenoid. The surfaces of these bones, where they touch, are covered in articular cartilage which is a smooth matter that shields the bones and allows them to move trouble-free. Synovial membrane (slim, smooth tissue) coats the remaining surfaces of the joint. When the joint is healthy the synovial membrane produces a solution that works as a lubrication for the cartilage and prevents friction in the shoulder. Shoulder stability is provided by muscles and ligaments that surround it. The shoulder has the greatest range of motion out of all the joints in the body as a result of these structures.
Damaged parts are removed and replaced in shoulder replacement surgery. Prosthesis’s (artificial parts) are used to replace the damaged areas of the shoulder. During the surgery either the ball (top of the humerus) or the entire ball and glenoid (socket) are replaced.
Multiple conditions can cause shoulder pain and debilitation.
• Osteoarthritis – arthritis from wear and tear that is age related
• Rheumatoid Arthritis – Synovial membrane that covers the joint develops inflammation and thickens
• Post-traumatic Arthritis – fractures or tears in the tendons or ligaments of the shoulder may damage the articular cartilage over time
• Rotator Cuff Tear Pathology – a big, untreated rotator cuff tear may lead to damage in the joint cartilage and arthritis
• Avascular Necrosis (Osteonecrosis) – the blood supply to the bones is interrupted and bone cells die causing damage to the shoulder joint and arthritis
• Severe Fractures – when the upper arm shatters it can be difficult to piece back together and blood supply may not return properly to the bone
• Failed Previous Shoulder Replacement Surgery – this is uncommon, but if it occurs it most likely would be from either the implant loosening, prosthesis wear, infection, or dislocation
Evaluation and Treatment Options
An evaluation may consist of; medical history discussion, physical examination, x-rays, occasional blood test, magnetic resonance imaging (MRI) scan, and/or bone scan.
Several treatment options are available.
• Total Shoulder Replacement –typically entails the replacement of arthritic surfaces in the joint with a metal ball attached to a rod and a plastic socket. The surgeon may choose to cement or press fit the prosthesis. Cement is used when the bones are soft, tendons torn beyond repair or if the bones are badly worn. Most of the time cement is used. However, if the bone is in good condition the press fit option may be used instead.
• Stemmed Hemiarthroplasty – only the ball is replaced in this surgery. A metal ball and stem similar to that in the total shoulder replacement is used in the Hemiarthroplasty. Sometimes the physician may not know which procedure will be necessary (total or hemiarthroplasty) until they are in the operating room.
• Resurfacing Hemiarthroplasty – only the joint surface of the ball is replaced. A cap like prosthesis is used instead of the entire ball and stem prosthesis. This surgery has bone preserving advantages and helps young patients reduce the risk of the prosthesis to wear or loosen.
• Reverse Total Shoulder Replacement – very similar to the conventional total shoulder, the reverse total shoulder replacement simply installs the metal ball on the shoulder bone and the socket on the humerus. This surgery may be necessary because a total shoulder replacement has failed, a rotator cuff is completely torn causing arm weakness, pain persists, or the arm is debilitated from hindered range of motion.
Physical Therapy following shoulder replacement
Physical therapy usually begins after your first follow up appointment with your surgeon. Initial physical therapy goals include restoring range of motion, decreasing pain and swelling, and improving muscle function. Your physical therapist will help you safely return to your daily activities including work and leisure activities.