April, 2017: Update on Total Wrist Arthroplasty
The first total wrist arthroplasty (TWA) was performed in 1890 and was a ball and socket replacement made of ivory. In the 1970s, stemmed silicone spacers were used to replace the proximal carpal row and maintain alignment of the hand on the forearm. Unfortunately, the silicone implants often broke.
Implant designers then took advantage of the well-established concepts that were already successful for total knee and total hip implants. These wrist implants had stems that were cemented into the distal radius and into a central metacarpal. Although pain relief was good, loosening and dislocation caused frequent failures.
The next generation of implants required less bone removal in an attempt to improve stability. Failure, however, was still frequent, particularly from the metallic stems cutting out from the metacarpal and from dislocation of the carpal component on the radius component.
The current implants are designed to maximally preserve bone and to reduce instability. The proximal portion is metallic with a surface simulating the contour of the radius articular surface and a stem that is designed for a cement-less, press-fit into the radius. The distal component has a metal-backed polyethylene surface that simulates the proximal articular surfaces of the lunate and scaphoid combined. The distal component is secured with screws into both the distal carpal row and into the index metacarpal. Five-year survival rates with the modern designs are in excess of 90%, which is markedly higher than for previous designs.
To date, most TWAs have been performed for patients with rheumatoid arthritis. Because of improved implant designs, more patients with post-traumatic and osteoarthritis are now choosing TWA over wrist fusion. Complications are infrequent for either procedure, and one cited study indicated that DASH scores were better for patients receiving TWA than for those with wrist fusions.
The current TWA implant designs may also prove useful even if the patient has had previous surgery, including proximal row carpectomy or wrist fusion. Should a TWA fail, wrist fusion is feasible by using a large bone graft to restore normal carpal height. A novel indication for TWA is for treatment of an acute, severely comminuted distal radius fracture. Two reported cases with one year follow-up and good subjective and objective assessments.
Cost of TWA is an issue. Considering the expenses of the implant, hospitalization, and those related to a possible complication or revision, TWA is nearly three times more expensive as a fusion. When quality-adjusted life-years were factored in for these patients with rheumatoid arthritis, however, a TWA cost only slightly more than a wrist fusion.
The authors of this review conclude that modern implant design has made TWA a reliable and durable procedure. The decision between TWA and wrist fusion remains a complex one and needs to take into account each individual’s functional requirements and activity level.
COMMENT: Having watched the progress of TWA stagger along over decades, I enjoyed reading this current update. The authors cite 30 relevant articles and give a balanced assessment.
It should not be surprising that TWA has lagged far behind the successes experienced by total hip and knee replacements. Just consider the joints. The knee is a hinge. Period. The hip is a ball and a deep socket. Period. In either instance one bone moves on one bone. By contrast, the wrist has the radius rotating around the ulna just proximal to the wrist. Then the proximal carpal row moves on both the radius and on the distal carpal row. Simulating these complexities with implants is a huge challenge. Furthermore, the hip and knee only need to withstand compression forces, whereas the wrist has to withstand distraction forces, when carrying a suitcase for instance.
The relatively small numbers of arthritic patients needing major wrist reconstruction compared to hips and knees has also retarded technical advances in implant design. Innovators naturally want to pursue the big ticket items.
So I consider it practically a miracle that TWA works at all. For your patients with marked pain and limited motion from advanced wrist arthritis, TWA might be the best answer. It would be worthwhile for them to investigate the benefits and risks of TWA. Ten years ago I would not have advised this.