Tag Archives: shoulder joint

Reverse Total Shoulder Replacement

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Reverse Total Shoulder Replacement or Delta Shoulder Replacement is a modification of total shoulder replacement procedure. The conventional procedure has a metal ball on the humerus (replacing the natural humeral head) and a plastic component on the glenoid. The reverse procedure has the reverse positions of the prostheses : the metal ball is now fixed on the glenoid socket and the plastic cup is fixed in place of the humeral head (Fig. 1). This configuration is indicated for people with rotator cuff arthropathy.

Conventional and reverse total shoulder replacement

Fig. 1: Configuration of conventional versus reverse total shoulder replacement. Note the location of the metal head and plastic component in each case. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Why a conventional total shoulder will not work with rotator cuff arthropathy?

Rotator cuff arthropathy or cuff tear arthropathy (CTA) is shoulder arthritis in a setting of rotator cuff tears. Rotator cuff muscles hold the ball and the socket together and prevent the humeral head from moving out of the socket when the deltoid muscle raises the arm. In people with torn rotator cuff, the head of the humerus moves upwards out of the socket resulting in shoulder instability. Conventional total shoulder preserving the natural configuration of the shoulder joint will encounter the same problem (Fig. 2, left panel).

Fig. 2: Conventional versus reverse total shoulder replacement with torn rotator cuff. The upward force displaces the humeral head in conventional configuration but stabilizes the joint in reverse configuration. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Why a reverse total shoulder would work?

In reverse total shoulder procedure, the arthritic humeral head is replaced with a plastic cup and the metal ball is fixed onto the glenoid surface. With this configuration, the contraction of the deltoid will move the arm up and compress the socket to the ball at the same time (Fig. 2, right panel). The ball and the socket will fit more snugly together providing stability.

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Shoulder arthritis

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Shoulder arthritis refers to loss of cartilage on the surface of the ball (humeral head) and the socket (glenoid) of the shoulder glenohumeral joint. The two bones rub against each other and produce pain, stiffness and difficulty moving an arm.

Types and Causes of Shoulder arthritis

Osteoarthritis (OA) – also called degenerative joint disease (DJD), is the “wear and tear” condition of the joint commonly due to old age. OA is characterized by loss of cartilage, bone spurs (osteophytes) and no major inflammation (Fig. 1).

Fig. 1: Osteoarthritis of the main shoulder joint. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Rheumatoid arthritis (RA) – Inflammation of the synovium – the membrane that encloses the joint and contains lubricant fluid. Inflammation brings in the cells of the immune system whose inflammatory chemicals damage and destroy the joint. It’s not clear how RA starts but genetic predisposition together with infection of the joint are likely to be among the causes.

Rotator cuff arthropathy or cuff tear arthropathy (CTA) – Shoulder arthritis as a result and in a setting of rotator cuff tears. Rotator cuff muscles hold the ball and the socket together and prevent the humeral head from moving out of the socket when the person raises an arm. In people with torn rotator cuff, the head of the humerus moves upwards and rub onto the acromion. This causes damages to the covering cartilage and eventually arthritis. Combination of cuff tear and arthritis is a devastating condition that seriously compromises function of the shoulder.

Post-traumatic arthritis – arthritis that develops after physical injury to the joint.

Chondrolysis – sudden loss of cartilage that happens occasionally after a shoulder surgery, commonly seen in association with infusion of local anesthetics into the joint for pain management.

Treatments

Non-surgical treatments include shoulder exercises and anti-inflammatory medications.

Surgical treatments include a variety of procedures :

1. Total shoulder replacement surgery : the arthritic humeral head is replaced with a metal ball on a stem that fits inside the humerus, the socket is replaced with a plastic component made of high density polyethylene.

Fig. 2: Total shoulder replacement procedure. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

2. Ream and Run Arthroplasty – a modification of total shoulder procedure above. The metal ball replaces the humeral head but the socket is simply shaped, smoothed to fit the ball and left to heal. No plastic component used. With time, the body grows a cartilage layer on top of the socket. This procedure is recommended for younger and more active individuals.

3. Reverse total shoulder or Delta total shoulder replacement – This is indicated for people with rotator cuff arthropathy (see types of shoulder arthritis above). This procedure reverses the positions of the prostheses : the metal ball is now fixed on the socket and the plastic component is fixed in place of the humeral head. This topic is covered in the next article about reverse total shoulder replacement.
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Common shoulder injuries and surgical repair (part 1)

Anatomy

There are three bones in the shoulder: the humerus (the bone of the upper arm), the scapula (shoulder blade) and the clavicle (collarbone). Articulations between these bones make up the shoulder joints. The main joint, commonly referred to as “the shoulder joint”, is the joint between the head of the humerus and glenoid cavity of the scapula and is called the humeroscapular or glenohumeral joint. The second joint of the shoulder is formed by the articulation between the clavicle and the acromion (extension of the scapula that forms the top of the shoulder) and is called acromioclavicular joint or AC joint. The two joints are stabilized by associated muscles and ligaments.

Fig.1: Main components of the shoulder joint. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Shoulder dislocation

Shoulder dislocation occurs when the humeral head slips out of the pocket made by glenoid cavity of the scapula (Fig. 2). This usually happens as a result of trauma (fall, sport injury,..). Dislocation can be anterior where the humerus slips to the front or posterior where it dislocates behind the normal position. Anterior dislocation is more common.

Fig.2 : Types of shoulder dislocation. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Below is a narrated animation about shoulder dislocation, bankart lesion and repair. Click here to license this video and/or other orthopaedic videos on Alila Medical Media website.

Bankart lesion and shoulder instability

The glenoid cavity has a ring of fibrocartilage tissue called the labrum around it. The labrum makes the cavity deeper and helps to keep the humeral head in place (Fig.3). During anterior shoulder dislocation, the head of the humerus may be pressed against and damages the anterior portion of the labrum. This type of labral tear is called bankart. Damaged labrum makes it easier for the humeral head to slip out of place again. This vicious cycle leads to repeated shoulder dislocation and severely damaged labrum. The condition is called shoulder instability as it feels like slipping out anytime. Treatment includes physical therapy and, in some cases, surgery for bankart repair (see below).

Click here to see an animation of bankart lesion and arthroscopic repair on Alila Medical Media website where the video is also available for licensing.

Fig. 3: Anatomy of the shoulder joint with the humerus slightly abducted to show the glenoid cavity and labrum. Types of labral lesions are shown on the right. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Bankart repair

During surgery the damaged cartilage is removed, area is cleaned, small holes are then drilled into the bone of glenoid fossa to hold small suture anchors with threads. The threads are attached to the labrum and pulled tightly to hold the labrum to the glenoid (Fig.4). Over time, the labrum will reattach to the glenoid naturally. Physical therapy will be needed to regain the shoulder range of motions and strength.

Fig.4: Steps of bankart repair surgery. See text for details. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.

Bankart repair can be done with arthroscopic or open surgery. While arthroscopy is minimal invasive, open surgery maybe recommended for larger tears. In arthroscopic surgery only two or three small incisions are made, an arthroscope is inserted through one of the incision. Arthroscope is an instrument equipped with light and camera which transmits image of the joint to a computer screen. Other small tools are inserted to carry out the repair (Fig.5).

Click here to see an animation of arthroscopic bankart repair.

Fig. 5 : Arthroscopic surgery for bankart repair. Click on image to see a larger version on Alila Medical Media website where the image is also available for licensing.