Total wrist arthroplasty (TWA) provides a motion-preserving alternative to total wrist arthrodesis for low-demand patients with debilitating pancarpal arthritis. The earlier generation total wrist implants had high complication and failure rates. Advances in prosthetic design have contributed to improved clinical outcomes and implant survivorship. The current fourth-generation implants allow for expansion of indications for TWA. Careful patient selection remains critical; patients with high-demand lifestyles and poor bone stock may not be candidates. Long-term studies on implant survival and patient outcomes are critical for the current generation total wrist implants in assessing their long-term value compared with total wrist arthrodesis.
Key points
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Total wrist arthroplasty provides a motion-preserving alternative to wrist arthrodesis for low-demand patients with debilitating, painful pancarpal arthritis.
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Technical advancement in implant design promotes osteointegration and preserves motion with the goal of reducing torque transmission to the carpal component.
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Current generation implants have reduced rates of dislocation and instability but reoperation rates remain high and further long-term evaluation of survivability and complications are necessary.
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Long-term, prospective, randomized trials comparing total wrist arthroplasty with wrist arthrodesis are needed to understand which patients receive the greatest benefit with the lowest failure and complications.
Introduction
Total wrist arthroplasty (TWA) provides a motion-preserving alternative to total wrist arthrodesis for low-demand patients with debilitating arthritis. Palmer and Werner determined the functional range of motion of the wrist to be 30° of extension and 5° of flexion. To perform most activities of daily living, including hygiene and food preparation, Ryu and colleagues suggested that wrist flexion and extension of 40° are required. The first description of a wrist prosthesis was by Gluck, who placed an ivory wrist implant for tuberculosis of the wrist in 1891. Swanson introduced the first commercially available total wrist implant with a hinged silicone interpositional spacer prosthesis in 1967. Significant improvements have been made with TWA prosthesis design over the past 2 decades, which has simultaneously allowed for both improvements in clinical outcomes with TWA, and the expansion of clinical indications for this procedure.
Introduction
Total wrist arthroplasty (TWA) provides a motion-preserving alternative to total wrist arthrodesis for low-demand patients with debilitating arthritis. Palmer and Werner determined the functional range of motion of the wrist to be 30° of extension and 5° of flexion. To perform most activities of daily living, including hygiene and food preparation, Ryu and colleagues suggested that wrist flexion and extension of 40° are required. The first description of a wrist prosthesis was by Gluck, who placed an ivory wrist implant for tuberculosis of the wrist in 1891. Swanson introduced the first commercially available total wrist implant with a hinged silicone interpositional spacer prosthesis in 1967. Significant improvements have been made with TWA prosthesis design over the past 2 decades, which has simultaneously allowed for both improvements in clinical outcomes with TWA, and the expansion of clinical indications for this procedure.
Indications and contraindications
TWA is classically described for patients with rheumatoid arthritis, especially those with bilateral wrist involvement. Its use has expanded to pancarpal wrist arthritis in patients with nonrheumatoid inflammatory arthritis, posttraumatic arthritis, osteoarthritis and avascular necrosis. Ideal surgical candidates are patients who have failed nonoperative management with persistent debilitating pain that limits the ability to perform activities of daily living, have low-demand lifestyles, and are seeking a pain-free wrist with preservation of moderate motion. Patients with arthritis involving multiple joints of the upper extremity, including limitations in elbow motion or forearm rotation, often find activities of daily living easier when some wrist motion is preserved and thus may have greater benefit from a TWA over a wrist arthrodesis.
Absolute contraindications include a lack of neuromuscular control of the hand, laborers, those with high-demand use of the upper extremity for ambulation and transfer, previous surgery with implant or bone loss that limit adequate carpal or radial fixation, and patients with an active infection. One relative contraindication is inadequate carpal bone stock to support the implants from severe erosions or osteopenia. In addition, inadequate treatment of soft tissue contractures or imbalance can lead to persistent instability or motion restriction after TWA.
Operative procedure
A dorsal longitudinal midline incision is made over the wrist. Full-thickness skin flaps are raised with attention paid to protecting the branches of the radial sensory and dorsal ulnar cutaneous nerves. The retinaculum over the sixth dorsal compartment is incised followed by elevation of the flap radially to the septum between the first and second extensor compartments. The dorsal capsule is raised as a broad, distally based flap off the distal radius from proximal to distal, through the floors of the first and sixth extensor compartments. Care is taken to elevate full-thickness capsular flaps to allow for closure. Alternatively, the distal portion of the extensor retinaculum can be placed under the finger extensors to augment the capsular closure.
Once the dorsal capsule is raised, the wrist can be flexed to expose the joint and perform synovectomies if necessary. A distal ulnar resection can now be performed if there is an arthritic distal radioulnar joint. The order of preparation of the carpus and radius varies. The distal radius is cut, broached, and trialed according to the specific implant, and care is taken to protect the volar radiocarpal ligaments. The technique for carpal bone preparation varies among implants, and Kirschner wires are often used to temporarily pin the carpal bones to facilitate the carpal bone cuts. The distal radius cut is usually made perpendicular to the long axis of the forearm while the carpal cut is made perpendicular to the axis of the third metacarpal. Care is taken to protect the volar capsule and radiocarpal ligaments. Soft tissue balance is extremely important. With the trial radial component in place, trial polyethylene carpal components can be introduced so that both stability and range of motion can be assessed and adjustments made as necessary. Intraoperatively, there should be wrist flexion and extension of 30° in each direction. With limited wrist extension, more distal radius should be resected. If there is volar instability, a larger polyethylene should be used. Repair of the volar radiocarpal ligaments can also be considered. Patients with severe wrist flexion contractures may benefit from step cut lengthening of the wrist flexors.
Prosthetic design
Themistocles Gluck performed the TWA using an ivory implant in a 19-year-old patient with tuberculosis of the wrist in 1890. This subsequently developed a chronic fistula and was recognized as a failure despite reported good range of motion. Since then, there have been significant advances in prosthetic design, materials, fixation, and surgical techniques that have led to remarkable improvements in clinical outcome and implant survivorship and decreased complications. Newer implants have more anatomic design, involve minimal bony resection, and have more stable fixation.
First-generation Implants
Often described as a first-generation implant, the first commercially available Swanson implant was designed in 1967 as a silicone rubber, 1-piece, flexible, hinged implant that primarily serves as an interpositional implant ( Fig. 1 ). The implant stems are mobile in the medullary canals, fitting into the radius proximally and passing through the capitate and seats in the third metacarpal distally. Long-term follow-up studies have demonstrated prosthetic fracture, implant subsidence, silicone synovitis, and progressive radiologic and clinical deterioration.
Fatti and colleagues retrospectively reviewed 47 patients with Swanson TWA and found that at average follow-up of 5.8 years postoperatively, only 51% of patients reported pain relief compared with their initial 1986 review of the same cohort demonstrating pain relief in 67% at average follow-up of 4.8 years, suggestive of continued clinical deterioration. Long-term studies have shown considerable problems with implant fracture, which most often occurs at the distal stem and barrel junction. Jolly and colleagues found an implant fracture rate of 52% and also showed a trend toward progressive radiologic and clinical deterioration at an average follow-up of 6 years. Silicone synovitis is a well-documented complication of the Swanson implant, with studies reporting rates of radiologic silicone synovitis as high as 30%.
In 2005, Kistler and colleagues reviewed 12 patients with rheumatoid arthritis treated with the Swanson implant with a minimum 10-year follow-up. Interestingly, they reported good to very good subjective results in 75% of patients despite a high number of implant fractures and expected silicone synovitis, suggesting that the correlation between clinical results and implant integrity may not be straightforward. The authors concluded that low-demand patients with rheumatoid arthritis with severe deformity and bony erosion may still be good candidates for the Swanson silicone spacer implant as an alternative to wrist arthrodesis or TWA using the more complex, modern design prosthesis.
Second-generation Implants
Second-generation implants had separate radial and carpal components and relied on either a ball-and-socket design or hemispherical implants. In 1973, The Volz prosthesis was developed at Arizona Health Sciences Center as a semiconstrained cemented cobalt chrome alloy prosthesis. The metacarpal component has a hemispherical surface with 2 different radii that allows for more wrist flexion and extension than radial and ulnar deviation, and minimizes radiocarpal rotation. The component fits through the capitate into the third metacarpal. The radial component has a polyethylene component with a concave surface that articulates with the metacarpal component. Volz reported on 25 cases in patients with rheumatoid arthritis and reported no infections, dislocations, implant loosening, or radioulnar imbalance. Volz stressed the importance of soft tissue balance and musculotendinous forces across the radiocarpal joint. In a review of 30 Volz total wrist arthroplasties in patients with rheumatoid arthritis, Dennis and colleagues reported 86% of patients had pain relief and satisfaction, but there were complications in 12 of 30 cases (40%) with a 24% rate of metacarpal component loosening. Gellman and associates reviewed their series of 14 total wrist arthroplasties with the Volz prosthesis with mean follow-up of 6.5 years. Migration of the radial component was seen in 2 patients with migration of the carpal component in 5 patients. Radiographic lucency was present in the radial component in 3 patients, the carpal component in 2 patients, and both components in 2 patients. There were 2 dislocations. The majority of the complications were related to technical problems with soft tissue balance and centering of the prosthesis and prosthetic design issues related to poor distal fixation.
Meuli introduced an unconstrained polyester ball-and-socket design in 1970 that used malleable metal forks to gain fixation in the second and third metacarpals. The rationale behind the ball joint was to allow for easier manufacturing, better range of motion in all planes, and to minimize unfavorable stresses and edge loading from impingement. The original Meuli prosthesis included a polyester ball that was replaced with an ultra-high-molecular-weight polyethylene with newer models. The newer prosthesis also incorporated eccentric prongs that allowed for more exact centering of the prosthesis. Because the center of rotation of the radiocarpal joint is volar to the longitudinal axis of the radius, the malleable prongs allow the surgeon to adjust the component positioning intraoperatively ( Fig. 2 ). Meuli described 41 implants of which 15 wrists required reoperation that were attributed mostly to technical errors and prosthesis centering, but ultimate satisfactory outcome was described in the majority of cases. The Meuli implant has had a number of revisions, with the most recent MWP III Total Wrist Prosthesis, which uses a titanium alloy malleable design with a spherical head radial component that articulates with a polyethylene cup of the metacarpal component (Zimmer, Warsaw, IN).
Vogelin and Nagy reviewed 16 wrists that had complications with Meuli I, II, and III prostheses and found that a combination of both mechanical and soft tissue problems were causes for failures in 69% of the failures. Both loosening of the distal component and metacarpal perforation occurred in the majority of their reviewed failures. Cooney and colleagues reviewed the Mayo Clinic experience with the Swanson silastic implant, the Volz prosthesis, and the Meuli prosthesis. Cooney attributed implant failure to 3 major factors: (1) centering of the prosthesis, (2) implant fixation, and (3) soft tissue balance. The Meuli prosthesis requires bending of the distal prongs to center the radiocarpal joint. The Volz prosthesis was modified with a dorsal offset on the metacarpal component to more accurately duplicate the center of rotation. In 140 Meuli arthroplasties at the Mayo Clinic there was reoperation rate of 33% for major complications including 8.6% dislocations, 2.9% prosthetic, 12.1% soft tissue deformity or contracture, and 6.4% tendon rupture. The authors recommended against the use of the Meuli prosthesis for clinical use despite the design changes based on the high complication rates.
Third-generation Implants
Third-generation implants include the Biaxial total wrist implant, the Trispherical prosthesis, and the Universal prosthesis. The third-generation prostheses were designed with the goal of minimizing bone resection, restoring the center of rotation of the wrist, and improving soft tissue balance and stability.
The Trispherical total wrist prosthesis has a radial component with a spherical head that articulates with a high-density polyethylene bearing on the metacarpal component to form a ball-and-socket joint. There is an axle constraint to prevent dislocation. The metacarpal component consists of a large third metacarpal stem and a smaller offset second metacarpal and scaphoid stem. The offset stem provides rotational stability. Figgie and colleagues reviewed 35 cases of the Trispherical TWA with average follow-up of 9 years and reported no dislocations, implant fractures, or implant failures. However, the same group subsequently presented 8 failures out of 87 trispherical total wrist arthroplasties. Two of the failures were from progressive wrist flexion contracture owing to loss of wrist extensor function. Mechanical failure occurred in 6 patients, with metacarpal loosening with dorsal perforation being the most common mode.
The Biaxial implant (Depuy Orthopedics, Inc, Warsaw, IN) is an unconstrained cemented cobalt chrome alloy implant with double-stemmed metacarpal component with an ellipsoidal head that articulates with a polyethylene-bearing surface that attaches to the radial component. In addition to the long stem that inserts into the third metacarpal, there is a small stud that inserts to the trapezoid for added fixation and rotational stability. The shape of the ellipsoidal articular component is designed to reproduce the anatomic movements and stability in the native wrist. In addition, the proximal radial component is offset ulnarly and palmarly to match the center of rotation. The stems have porous coated surfaces.
Cobb and Beckenbaugh reviewed 57 cases of Biaxial TWA with mean follow-up of 6.5 years and found failures in 11 cases that included loosening of the distal implant in 8 cases (14%), as well as 1 case each of infection, dislocation, and progressive soft tissue imbalance. The authors felt that technical difficulties with poor intraoperative positioning contributed to failures in 5 of the cases. They suggested advising patients of a 20% failure rate at 6 years and consideration of long-stemmed multipronged implants, especially in revision cases and patients with poor bone stock ( Fig. 3 ). Rizzo and Beckenbaugh reviewed the Mayo Clinic experience with the long-stem biaxial prosthesis in 17 patients. There were no cases of prosthetic failures or revisions at a mean of 73.9 months. However, there were 2 cases of intraoperative metacarpal fractures. The authors caution that the longer metacarpal stem is more difficult to insert and potentially increases the risk of stress shielding. Takwale and colleagues reviewed 76 biaxial total wrist implants and found no correlation between stem length in the third metacarpal component and loosening or terminal events. The probability of implant survival at 8 years was 83%. They found that uncemented fixation was predictive of future distal component loosening, and that the alignment of the distal component in extension predicted loosening and migration of the carpal component.
Menon’s Universal I Total Wrist Implant (KMI Inc, San Diego, CA) is a nonconstrained implant with a Y-shaped radial component and a central carpal component that consists of a titanium plate holding a central capitate component with 2 screws on each side of that insert into the second and fourth metacarpal bones. A large, toroidal-shaped articular polyethylene-bearing surface attaches this plate to the cobalt chromium radial component, and the radial articular component has a 20° inclination similar to the native radial articular surface. The large articular surface area was designed to resist instability and dislocation.
Menon reviewed this implant at average follow-up of 6.7 years and reported excellent pain relief in 88% of patients. However, he also reported a 32% complication rate with 5 volar dislocations in 37 wrists being the leading complication. Divelbiss and colleagues also reviewed the Universal Total Wrist Implant and reported a 14% complication rate, all owing to instability in patients who were noted to have severe wrist laxity with advance rheumatoid arthritis.
Recently, Ward and colleagues reviewed the 5- and 10-year outcomes of the Universal Total Wrist Implant in rheumatoid arthritis patients and reported a 50% revision rate at the latest follow-up at average 7.3 years. In 19 patients with a minimum 5-year follow-up, 9 prostheses had undergone revision surgery because of carpal component loosening. Only 1 patient had wrist instability that was ultimately managed with a wrist arthrodesis. At the time of revision surgery, all wrists had evidence of polyethylene wear, metallosis, and carpal component loosening. There was no evidence of loosening of the radial component in any of the wrists. All 10 prosthesis that were functioning at the time of follow-up had radiographic evidence of intercarpal fusion.
Fourth-generation Implants
Current generation implants were designed with the goal of improving the instability and fixation problems that plagued many of the earlier generation components. Loosening of the distal component remained the most difficulty challenge with the earlier generation prosthesis. Fourth-generation implants are mainly uncemented with porous titanium surfaces to allow for osseous integration. There are currently 3 designs that are approved by the US Food and Drug Administration ( Fig. 4 ).
