Total Wrist Replacement

Arthritis of the wrist is not an uncommon condition and it affects the radio-carpal, mid carpal and distal radio ulnar joints. It usually presents with pain, loss of grip strength and deformity. As with arthritis anywhere else in the body the most common causes are osteoarthritis (primary and secondary) and rheumatoid arthritis. A few rare forms of inflammatory arthritis can also affect the wrist joint.

The treatment options that have been traditionally available are conservative measures in the form of splinting, intra-articular steroid injections and surgical measures such as denervation, arthroscopic debridement, proximal row carpectomy and fusion. Although total joint replacement has been quite popular with hip and knee joints since the mid 60s, it has never been a sought after option for the wrist joint. This is partly due to the complexity of the wrist joint and partly due to the failure of the earlier designs of wrist arthroplasties that were available in the 80s and late 90s.

Wrist fusion has been described since the early 50s and has long been the gold standard treatment for all types of wrist arthritis. Although it gives consistent pain relief, over the years it has been associated with a few problems such as poor hand function, a long recovery period, non-union and a high re-operation rate for metal work complications. It definitely has not been a suitable option for bilateral wrist arthritis.

Universal Total Wrist

The complications from wrist fusion have led to the concept of total wrist replacement being re-visited. This has coincided with a better understanding of the bio-mechanics of the wrist joint and also advances in implant technology especially with polyethylene. Also patient expectation has increased and they are no longer happy with just a pain free wrist which does not function well. The obvious advantages with a replacement over a fusion are good pain relief, improved range of motion, good strength and a much quicker recovery time.

The earlier models of wrist replacements were essentially silastic interpositional implants which caused lot of local reaction and led to early failure. The modern types all have a metal on poly articulation and are made up of two components:

Fixed to the capitate either cemented or uncemented with a peg and augmented with two screws.

Maestro Total Wrist

One screw goes into the trapezoid and second metacarpal and the other screw goes into the hamate and the fourth metacarpal.

This has a stem which is placed intra-medullary within the radius. This can be cemented or uncemented.

The difference among major manufacturers is where the metal and the polyethylene are situated. For example, in the Universal Total Wrist (KMI) the polyethylene is on the carpal side whereas in the Maestro (Biomet) replacement it is on the radial side as the following pictures illustrate.

In addition to this a distal radio-ulnar joint can also be inserted depending on the state of the distal radio ulnar joint. In our unit we have been using the Biomet Maestro Total Wrist Replacement for the past two years.

Whatever type of wrist replacement is used, the operation is usually carried out under general anaesthesia with a regional nerve block. A dorsal approach is used with access through the bed of the extensor tendons. A dorsal capsulotomy is done and flaps raised to aid repair at the time of closure. The components are inserted and the whole procedure is done under image intensifier control to aid perfect positioning of the implant as shown below.

Post operatively the wrist is placed in slight dorsiflexion either in a plaster back slab or a splint for a period of six weeks before we start mobilising to aid soft tissue healing.