Abstract
Distal radioulnar joint (DRUJ) arthropathy is relatively uncommon but problematic when present. Surgical options to address this condition are divided into nonanatomical procedures and prosthetic reconstruction. Nonanatomical procedures (Sauve-Kapandji, Darrach’s, etc.) have widespread use among hand surgeons but patients can develop impingement syndrome which can be debilitating.
The Eclypse prosthesis was designed as an alternative to these procedures with the intention of avoiding this rather common complication. The implant consists of a pyrocarbon head and a stem. The insertion technique should be meticulous and is thoroughly described in this chapter.
This prosthesis is indicated in mono arthropathy of the DRUJ as long as there is no major instability of the said joint. It is not indicated in patients who have had a previous Darrach’s or Sauve-Kapandji.
Published literature suggests that good results are achieved early with reliable stability over time. Complications so far have been minimal but we have witnessed one case of molybdenum allergy requiring explantation.
Key words
eclypse – distal radioulnar joint (DRUJ) arthroplasty – DRUJ arthropathy – pyrocarbon prosthesis34 Eclypse Distal Radioulnar Joint Arthroplasty
34.1 Introduction
An intact distal radioulnar joint (DRUJ) is critical to stability and load transmission during forearm and wrist motion. 1 The DRUJ is the keystone in coordination of forearm rotation and wrist circumduction. 2 Arthropathy of the DRUJ is an uncommon problem but when present can cause severe limitations.
Current treatment options for DRUJ arthropathy can be divided into nonanatomical procedures and prosthetic reconstruction.
Salvage nonanatomical procedures (Darrach’s, Bowers’, matched distal ulnar resection, or the Sauvé-Kapandji procedure) fail to restore normal joint anatomy and can carry complications of their own, including instability, subluxation, clicks, and translocations. 3
The most common complication is ulna impingement syndrome. Described by Bell et al 4 as a radioulnar convergence with subsequent impingement, patients present with pain, clicking, and a weak grip. Clinical signs include narrowing of the wrist and pain on compression of the forearm bones and on forced supination. Radiographs may demonstrate scalloping of the radius metaphysis at the site of contact.
The Eclypse prosthesis was designed as an alternative to nonanatomical surgical excisions with the intention of avoiding ulnar impingement syndrome. The goal is to re-establish the distal pivot point necessary for adequate tension of the soft tissue such as the interosseus membrane, thus allowing optimal transfer of loads between the radius and ulna.
34.2 Characteristics of the Implant and Technique
The Eclypse prosthesis is a pyrocarbon spacer developed to replace the articular portion of the damaged ulnar head in patients with isolated DRUJ arthropathy. 2 It can be implanted without major disruption to the foveal insertion of the triangular fibrocartilage complex (TFCC) or to the extensor carpi ulnaris (ECU) sheath, i.e., preserving the physiological DRUJ stabilizers.
It has two components: a titanium four-pronged stem and a pyrocarbon ulnar head. The purpose of the stem is to prevent dislocation of the spacer at extremes of motion. The pyrocarbon head “replaces” the native ulnar head restoring more normal DRUJ kinematics. It is better able to resist compression and shear stress than a tendon “anchovy” or scarring of an excision arthroplasty.
34.2.1 Technique
Via a dorsoulnar skin incision centered on the ulnar head, the dorsal cutaneous branches of the ulnar nerve are identified and preserved. The fifth extensor compartment is released longitudinally and an ulnarly based extensor retinacular flap is elevated avoiding opening the DRUJ and without disrupting the ECU sheath. This will expose the underlying DRUJ capsule (Fig. 34.1a, b).
A dorsal capsulotomy is designed to allow access to the ulnocarpal space, the dorsal edge of the TFCC, and the ulnar head. 5 This is obtained by raising an ulnarly based capsular flap using the following anatomical landmarks (Fig. 34.2): the dorsal border of the triquetrum; the retinacular septum between the fourth and fifth compartments; and the neck of the ulnar head. The most distal component of this flap design will involve an incision along the most proximal fibers of the dorsal radiotriquetral ligament. The flap is raised and if necessary, the TFCC meniscoid can be excised to aid visualization of the ulnocarpal space.
The ulnar head is subluxed for full exposure. This is achieved with full pronation of the forearm and some dorsal translation force onto the ulna. The TFCC should remain attached during this maneuver.
The osteotomy should be regarded as the most important step of the procedure. Accurate orientation of the excision osteotomy is essential. Two cuts are designed with the aid of an osteotomy guide: (1) Transverse: at the proximal end of the DRUJ articular surface of the ulnar head, perpendicular to the longitudinal axis of the ulna; and (2) Longitudinal: through the cartilage of the ulnar head, parallel to the longitudinal axis of the ulna, without breaching the fovea to allow for preservation of the radioulnar ligament (RUL) insertion (Fig. 34.3). In addition, the longitudinal osteotomy needs to be perpendicular to the flexion/extension plane of the elbow. The aim is for the osteotomy to direct the implant so that it will lie parallel to the ground with the elbow flexed at 90 degrees, irrespective of the position of forearm rotation.
After removal of the damaged articular surface, the forearm is fully pronated and the ulna dorsally translated. This will allow for the introduction of an awl into the medullary cavity. The entry point should be set adjacent to the base of the ulnar styloid while avoiding damage to the radioulnar ligament at the fovea. The awl should be aimed toward the center of the ulnar medullary canal in the direction of the ulnar diaphysis. With a 3.5-mm drill bit, a 4-cm long tunnel is created into the ulna. Drilling permits simultaneous sizing: if the drill makes contact with the inner cortex a small stem should be selected. If drilling is performed with no cortical contact (wider bone cavity), a 4.5-mm drill bit should be used next and a medium-sized stem subsequently inserted. In large patients a 5.5-mm drill and a large stem will be necessary. The stem should be inserted with a tight press-fit.
The four legs of the stem should be held together during insertion with a rubber band around the stem distal to the head (anatomically proximal) prior to final insertion. The band will roll distally as the stem is inserted and can later be cut away. Once inside the bone the four legs will spread apart creating an inherently stable construct that will prevent spontaneous extrusion. It is expected that new bone will grow around the legs within 6 weeks; therefore, some protection against extremes of pronation or supination should be enforced during that period.
Three trial heads are available: small, medium, and large. The head should match the diameter of the excised portion of the ulnar head. If the original head is too deformed for a reliable assessment, the small size is tried first and checked for stability and full mobility of the joint. With the trial in situ the construct should be neither too loose nor too tight based upon experience (Fig. 34.4).
Careful closure in layers is recommended. The first step is to repair the dorsal connection between the TFCC and the dorsal capsule fibers on the capsular flap with a 3–0 Vicryl suture (Fig. 34.5). This should not be overlooked as it will help ensure implant stability. The distal portion of the capsulotomy is closed via interrupted sutures connecting parallel fibers of the dorsal radiotriquetral ligament. The vertical portion can be reinforced by suturing the capsule to the septum between fourth and fifth compartments. This septum will be also used to reinsert the retinacular flap. Finally, subcutaneous tissue and skin closure are performed.
Postoperatively an above-elbow plaster cast is worn for 3 weeks with the forearm slightly supinated. Then a removable wrist splint is applied, which is removed three times a day for active forearm rotation performed within the limits of pain. Passive forearm mobilization should be avoided for at least until 6 weeks postoperatively to prevent damage to the bone ingrowth around the legs of the stem. At this point muscle strengthening of both the brachioradialis (the only muscle able to dynamically unload the DRUJ) and the ECU muscle (an effective dynamic DRUJ stabilizer) is begun. We recommend that contact sports should be avoided for 6 months.
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