Arthroplasty of the Distal Radioulnar Joint

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INTRODUCTION

The wrist is a complex structure consisting of the radiocarpal, midcarpal, and distal radioulnar joint (DRUJ). The three joints work together to set the hand in position to perform activities of daily living, avocational pursuits, and work requirements. Injury or disease to any of the three joints affects function of the upper limb. In the past, it was believed reasonable to resect or fuse one or more of these joints to relieve pain and improve strength. However, this often results in loss of function at the sacrifice of motion, which is often so critical to function of the hand and upper limb. Previous procedures for treatment of pain, instability, and loss of motion of the DRUJ included resection of the distal ulna (complete resection of the distal ulna or Darrach procedure), partial resection with soft tissue interposition, and fusion with a proximal pseudarthrosis to provide for forearm rotation. Though effective in relieving pain by removing opposing bone surfaces, these procedures often resulted in instability of the forearm and wrist, impingement of the distal ulna against the radius, loss of power grip, and restricted ranges of motion. In patients with rheumatoid arthritis, the carpus can translate ulnarly as a result of loss of both bone and soft tissue support on the ulnar side of the wrist.

In the past 10 years, there has been increased interest in joint replacement of the wrist. At this time, replacement of all or part of the DRUJ is now both possible and successful in properly selected and motivated patients. Prosthetic arthroplasty of the distal ulna alone can be performed with a variety of orthopedic implants using materials of ceramic, pyrolytic carbon, and metal (cobalt-chrome and titanium). Replacement of the distal DRUJ can be performed with total joint replacement with either an unconstrained or a constrained prosthesis. Total joint replacements are indicated when there is extended arthritis that precludes a hemiarthroplasty. In this chapter, we provide an update of the current prostheses for replacement of the DRUJ.

ANATOMY AND BIOMECHANICS

The DRUJ is a spheroidal joint with primarily 2 degrees of freedom (rotation and translation). It has important soft tissue support from the dorsal and volar radioulnar ligaments, the triangular fibrocartilage complex (TFCC), the interosseous membrane, and the subsheath of the extensor carpi ulnaris (ECU) tendon. Studies that reviewed resection of the distal ulna have demonstrated the importance of the DRUJ in maintaining the correct axis of forearm rotation and the transmission of forces from the hand and wrist to the elbow. This is a complex process involving an intact DRUJ joint, bone contact between the distal ulna and sigmoid fossa of the distal radius, support ligaments, the interosseous membrane, and the radiocapitellar and ulnohumeral joints.

Loss of ligament support of the DRUJ can lead to or cause instability and eventually result in arthritis. Restoration of the normal ligaments of the DRUJ is essential for effective function including stability and force transmission. Equally important is restoration of the joint anatomy (ulnar head and sigmoid fossa) in preserving function of the DRUJ. It is in the latter vein that prosthetic replacement is superior to resection of the joint or fusion.

PROSTHETIC REPLACEMENT

Indications

Arthroplasty of the DRUJ is indicated in both acute and chronic conditions, with salvage procedures more commonly performed at the present time than acute or primary operative procedures directed at the DRUJ. The acute or semi-acute indications for prosthetic replacement include comminuted fracture of the distal ulna precluding internal fixation and replacement of the distal ulna in cases of advanced rheumatoid arthritis. Complete replacement of the DRUJ may be necessary in crush injury or severe comminuted fractures of the distal radius in which restoration of anatomy cannot be achieved by other means. Such surgery would be analogous to total elbow replacement in highly comminuted and unstable fractures of the distal humerus.

For late or chronic conditions of the DRUJ, indications for prosthetic replacement include failed Darrach or other resection arthroplasty, failed fusion with pseudarthrosis (Sauvé-Kapandji procedure), impingement syndrome (radioulnar impingement after distal ulnar resection), failed silicone ulnar head replacement, and late arthritis of the DRUJ ( Fig. 30-1 A–C). For advanced forearm instability, an extended collar prosthesis along with ligament reconstruction (Linscheid-Hui procedure or a brachioradialis wrap) can restore forearm kinematics and support for the ulnar side of the wrist.

Contraindications

There are specific contraindications to consider when a patient otherwise appears to be a suitable candidate for distal ulnar replacement. Any previous infection is always a concern related to reinfection. Aspiration of the DRUJ or site of previous distal ulnar resection should be performed and cultures taken. If positive, other forms of treatment should be considered. Any previous fracture of the distal radius or ulna also may be a contraindication for distal ulnar replacement. A malunion of the distal radius would need a prior or simultaneous corrective osteotomy to provide correct alignment. Any ulnar shaft deformity should also be treated. Previous fusion of the DRUJ with pseudarthrosis is a relative contraindication, but verbal reports have suggested that it is possible to insert an ulnar head prosthesis at the base of a previous Sauvé-Kapandji procedure. Pain dysfunction is also a relative contraindication; however, direct ulnar nerve-related pain (somatic type I chronic regional pain syndrome) can be improved in combination with arthritis of the DRUJ by appropriate nerve treatment.

Other considerations are poor bone stock, advanced arthritis of the sigmoid fossa unless a total joint replacement is performed, and prior wrist fusion. Wrist fusion has been associated with an increased risk of prosthetic loosening. Cement fixation of a distal ulnar implant is recommended in the face of a prior total wrist fusion.

PROSTHESES FOR the DISTAL ULNA

Current distal ulnar head prosthesis replacement can be divided into constrained and unconstrained prostheses. The unconstrained prosthesis consists of an anatomic distal ulnar replacement with or without soft tissue reconstruction. The option includes a distal ulnar arthroplasty (ulnar head replacement) alone or distal ulnar replacement and resurfacing of the sigmoid fossa. A number of hemiarthroplasties have been used as distal ulnar head replacements. These include the Herbert-Martin prosthesis (ceramic), the U-head cobalt-chrome prosthesis with titanium-coated stem (uHead endoprosthesis, Small Bone Innovations, Morrisville, Pennsylvania); the E-Centrix prosthesis with a spheroid shape rather than circular ulnar head (Wright Medical Technologies, Arlington, Tennessee), and the partial or complete pyrolytic carbon prosthesis (Ascension Orthopedics, Austin, Texas). The Herbert-Martin ceramic prosthesis experience was published in 2000 with a clinical trial of 23 patients reported with 27 months’ follow-up. The uHead prosthesis (SBI) was reviewed in 2007 with a report of implants in 17 patients with more than 2 years’ follow-up. The surgical technique of prosthesis insertion has been presented on-line in the company websites and in surgical text or surgical review journals. Distal ulnar prostheses (Herbert and U-head) have been reported to have good to excellent clinical success. The remaining prosthesis has not been reported in peer-reviewed literature.

The ulnar head prosthesis in selective patients can be matched with a metal-backed polyethylene replacement of the sigmoid fossa of the distal radius ( Fig. 30-2 A and B). Clinical reports of five patients were presented at the International Wrist Investigators Workshop (Seattle, 2006) as having had good success, but the procedure and long-term results have not been published in peer-reviewed journals.

A total joint replacement of the distal ulna has been reported by the inventor. The Scheker implant (Aptis Medical, Louisville, Kentucky) is the only constrained replacement of the DRUJ with reported clinical information ( Fig. 30-3 A and B). It consists of a capture ulnar head with a fixed implant to replace the sigmoid fossa. The most recent clinical presentation involved 31 patients with an average of 6 years of follow-up. Pain decreased from 4.2 to 1.0 on a pain scale (0 to 5 with 5 as more severe pain). Functional results indicated increases in strength and motion. The specific surgical technique of the other DRUJ implants such as the constrained Scheker implant can be obtained from previous surgical reviews ²⁷or on-line at the Aptis Medical website. Each implant has variations on the surgical techniques as described by the inventor or manufacturer (see specific websites).

There were three complications: infection (one) and fracture about the prosthesis (two)—both related to trauma after the index procedure.

Prosthetic Design

The ulnar head prosthesis that we used (uHead endoprosthesis, SBI) is a modular endoprosthesis that consists of a metal stem with a shaft that can be press-fit or cemented into the intramedullary canal of the distal ulna. A metal semispherical ulnar head of cobalt-chrome alloy is connected to an intramedullary stem of cobalt-chrome alloy with a commercially pure titanium spray finished through a tight-fitting Morse-taper junction. There are two stem-neck designs: an extended collar for revision of previous distal ulnar complete resection and a normal collar for primary procedures calling for ulnar head excision and revision of failed distal ulnar head resection procedures. The head has a provision for fixation of the triangular fibrocartilage complex and ECU subsheath to the device by way of sutures, which we believe is advantageous for initial soft tissue stabilization. To ensure adequate length correction after previous surgery, different-sized ulnar head components and extended collars are available to compensate for shortening of the ulna after ulnar head resection.

Surgical Technique

The basic surgical technique involves either a dorsal ulnar or medial (ulnar) midline incision to approach the DRUJ ( Fig. 30-4 ). The extensor retinaculum is reflected, and the dorsal cutaneous branch of the ulnar nerve is identified and protected with a nerve/vessel loop. The DRUJ itself is approached by division longitudinally with reflection of the capsule with the ECU subsheath. The triangular fibrocartilage (TFC) is either reflected and suture-tagged or left attached to the ulnar styloid, which is released (divided) from the ulnar head. In chronic cases in which the distal ulna has been resected, the approach needs to be more cautious in identifying the cutaneous nerves and reflection of the dorsal capsule and ECU tendon subsheath. The TFC may be intact or loose, depending on previous procedures. It requires repair to the endoprosthesis.