Introduction

Arthroscopy of the distal radioulnar joint (DRUJ) is a natural extension of radiocarpal and midcarpal arthroscopy. It provides a minimally invasive means of evaluating the DRUJ, including visualization of the articular cartilage, synovium, and triangular fibrocartilage complex (TFCC). This chapter discusses the relevant anatomy and biomechanics of the DRUJ, indications for DRUJ arthroscopy, and the surgical technique. In addition, open distal radioulnar ligament reconstruction is described for patients with DRUJ instability found to have an irreparable TFCC.

Anatomy and Biomechanics

The DRUJ is a trochoid diarthrodial articulation that allows both rotation and translation during normal forearm motion. The overall dimensions of the sigmoid notch average 15 mm in the transverse plane and 10 mm in the coronal plane. Its dorsal bony rim is typically acutely angled, whereas the volar rim is more rounded and is frequently augmented by a cartilaginous lip. The shape of the notch varies considerably in both planes, which plays a role in both joint stability and ease of arthroscopic access.¹ Due to its relatively shallow and incongruent articulation, the DRUJ relies strongly on the soft tissues for stability. The structures that contribute to DRUJ stability are the pronator quadratus, extensor carpi ulnaris (ECU), interosseous membrane (IOM), DRUJ capsule, and components of the triangular fibrocartilage complex (TFCC).²

The TFCC is generally accepted as the major static soft-tissue stabilizer. The palmar and dorsal radioulnar ligaments are the prime components of the TFCC that stabilize the DRUJ. These ligaments appear as thickenings at the junctures of the triangular fibrocartilage, DRUJ capsule, and ulnocarpal capsule. As each ligament extends from its respective distal margins of the sigmoid notch, it divides in the coronal plane into two limbs. The deep (proximal) limb attaches at the fovea, and the superficial (distal) limb attaches to the base and mid-portion of the ulnar styloid. The palmar ligament provides origins for the ulnolunate and ulnotriquetral ligaments, whereas the dorsal ligament is confluent with the ECU sheath.

During forearm rotation, DRUJ translation occurs because the sigmoid notch is shallow (with a radius of curvature 50% greater than that of the ulnar head). At the extremes of pronation and supination, the ulnar head slides palmarly and dorsally in the sigmoid notch (respectively)—resulting in only 2 to 3 mm of articular contact area at the rims.³ Although DRUJ motion has a substantial translational component (with a changing axis of rotation), its instant axis generally passes near the center of the ulnar head—moving dorsally with pronation and palmarly with supination. The ulnar head serves as the seat for the sigmoid notch, around which the radius rotates.³ The amount of articular cartilage that covers the head varies from a 50-degree to a 130-degree arc.

The ulnar styloid is a continuation of the subcutaneous ridge of the ulna, providing increased area for soft-tissue attachments. At the base of the styloid lies a shallow concavity termed the fovea, which is replete with vascular foramina and is an attachment site for ligaments. Identification of this site is essential for anatomical repair and reconstructive procedures because the axis of forearm motion passes through it.

Indications

The DRUJ is susceptible to trauma, post-traumatic degenerative changes, and inflammatory conditions. Arthroscopy allows for inspection of the articular surfaces of both the sigmoid notch and the ulnar head. Chondromalacia, cartilage defects, and articular shear injuries may be visualized. Systemic inflammatory conditions (including gout and rheumatoid arthritis) are sources of DRUJ synovitis that can be evaluated and treated arthroscopically. PVNS leading to synovial hypertrophy, loose bodies from fracture, or osteophytes can be removed. Undersurface partial- or full-thickness tears of the TFCC can be seen and debrided. Occasionally, the competency of the volar ulnocarpal ligaments may be evaluated.

Contraindications

There are no absolute contraindications to DRUJ arthroscopy. However, the joint is very small and access is limited. Thus, relative contraindications include surgical proficiency and a tight joint that does not allow passage of the scope or instruments without undo joint damage. Radiographic evidence of degenerative changes is a sign that navigating the joint arthroscopically could be very difficult, especially if the joint is stiff.

Surgical Technique

A regional or general anesthetic is administered. The patient is positioned supine on the operating table. An upper-arm tourniquet is applied over cotton padding. The elbow is flexed to 90 degrees and the upper extremity is mounted in a traction tower using finger traps applied to the long and ring fingers. Placing the wrist in full supination facilitates access to the DRUJ, unless the joint becomes excessively tight in this position. In neutral rotation the opposing surfaces of the sigmoid notch and the ulnar head are congruent, whereas in full supination the opposing surfaces have only a marginal contact area of 2 to 3 mm.⁴

The joint is insufflated with 3 to 5 cc of sterile saline using a 20-gauge needle. The needle is punctured through the skin just proximal to the confluence of the radius and ulna and angled 45 degrees distally to enter the proximal aspect (axilla) of the DRUJ, which will serve as the proximal DRUJ portal. After distension of the joint, a small longitudinal incision is made at the injection site using a number 11 or 15 blade. Care is taken to avoid the EDQ tendon. A hemostat can be used to spread the subcutaneous tissue and penetrate the capsule.

A cannula with bullet-tipped trocar is inserted into the joint. The trocar is then removed and the arthroscope is inserted. A 2.0- or 2.7-mm arthroscope is preferred, depending on the size and tightness of the joint. Inflow is directed through the cannula, and outflow (if needed) is provided with a needle inserted just distal to the ulnar head and proximal to the TFCC. To maintain appropriate pressure, a three-way stopcock with an attached syringe filled with saline can be used to pump fluid into the joint when needed. Some surgeons prefer an arthroscopy pump system.

A distal DRUJ portal can be established for instrumentation and improved visualization of the ulnar dome and TFCC. This portal enters between the TFCC central disc and the head of the ulna (Figure 6.1). It should first be localized with a needle while viewing with the arthroscope in the proximal portal.⁵ The portal is typically used for instruments such as shavers, graspers, and radiofrequency devices.

FIGURE 6.1 Sites of the proximal and distal DRUJ portals are marked on the skin. The proximal portal is located just proximal to the confluence of the radius and ulna, and the distal portal enters between the TFCC and the ulnar head.

Arthroscopic Evaluation of the DRUJ

Beginning proximally, the axilla of the joint is inspected for loose bodies, synovial hypertrophy, and marginal osteophytes. Continuing distally, the cartilaginous surfaces of the sigmoid notch and ulnar head are evaluated. Chondromalacia, articular fractures, and full-thickness cartilage defects can be visualized and debrided. Relaxing traction on the fingers may increase space and visualization. Pronation and supination allow a more complete evaluation of the articular surfaces. Directing the arthroscope distally, the undersurface of the TFCC is evaluated for full- or partial-thickness tears.

By passing the arthroscope between the TFCC and the dome of the ulnar head, the distal radioulnar ligaments may be visualized from their attachments on the sigmoid notch to their insertion at the fovea of the ulna head. With the arm in neutral rotation, the TFCC is under the least amount of tension—allowing for easier evaluation of the distal articular surface of the ulna. At the fovea, the ulnocapitate ligament may be seen inserting into the ulnar head—just slightly ulnar to the attachments of the radioulnar ligaments.^5,6

Pitfalls

Entry into the joint is the most difficult aspect of DRUJ arthroscopy. Keeping the forearm positioned in supination during entry into the DRUJ is important to maximize the dorsal space of the DRUJ. At times, a 1.9-mm scope may be necessary if the joint is tight. Absorption of fluid by the distal radioulnar joint synovium can easily obscure one’s view of the small DRUJ. In the presence of a TFCC tear, fluid inflow from the radiocarpal joint may have already affected the DRUJ.^6,7

Postoperative Management

The portals are closed with 5-0 nylon sutures or Steri-Strips (some surgeons prefer to leave the sites open). The wrist is dressed in a compressive bandage with an ulnar gutter plaster splint to immobilize the wrist in a position of comfort. The splint is removed at 10 to 14 days when the patient returns for the initial postoperative visit. At this time, the sutures are removed and gentle wrist range of motion is initiated. A second postoperative visit two to three weeks later allows for a clinical assessment of function. Patient activities are typically advanced as tolerated, but unrestricted use is not usually achieved for several weeks.

DRUJ Instability

Arthroscopically assisted TFCC repair, especially for peripheral tears, is common practice (see Chapter 5). In the presence of DRUJ instability, an open TFCC repair directly to the fovea with transosseous sutures is more effective at restoring joint stability. If an arthroscopic or open TFCC repair is not possible due to chronicity and attenuation of the tissues, a secondary reconstruction is indicated. The author’s preferred technique for chronic instability reconstructs both radioulnar ligaments to restore normal joint stability and mechanics.^8–11

A 5-cm incision is made between the fifth and sixth extensor compartments over the DRUJ. The fifth compartment is opened over the radioulnar joint, and the extensor digiti minimi tendon is retracted. An L-shaped DRUJ capsulotomy is made with one limb along the dorsal rim of the sigmoid notch and the other just proximal to the dorsal radioulnar ligament (Figure 6.2). The ECU sheath is not opened or dissected from the ulnar groove during the procedure. Scar is debrided from the fovea. Functioning remnants of the TFCC are retained.

FIGURE 6.2 Dorsal exposure of the DRUJ for ligament reconstruction is obtained by incising the fifth compartment and raising a triangular capsular flap.

The periosteum beneath the fourth dorsal extensor compartment is elevated from the dorsal margin of the sigmoid notch. A guide wire for a 3.5-mm cannulated drill bit is driven through the radius several millimeters proximal to the lunate fossa and approximately 5 mm radial to the articular surface of the sigmoid notch. The site is chosen so that a tunnel can be enlarged if necessary to accommodate the graft without disrupting the subchondral bone of the lunate fossa or sigmoid notch. Fluoroscopic views confirm proper guide-wire position, and the tunnel is made with a cannulated drill.

A tunnel is created in the distal ulna between the fovea and ulnar neck. A 4- to 5-mm drill hole is made in the ulnar neck at its subcutaneous border. A guide wire is inserted in the hole and driven through the fovea. Alternatively, the wrist is flexed and the guide wire may be driven through the fovea and out the ulnar neck. A 3.5-mm cannulated drill bit is used to create the tunnel. If necessary, the tunnel may be further enlarged with larger drill bits or gouges to accommodate both limbs of the graft.

A palmaris longus or plantaris tendon graft is harvested. The palmar opening of the radius tunnel is exposed through a 3- to 4-cm longitudinal incision extending proximally from the proximal wrist crease between the ulnar neurovascular bundle and finger flexor tendons. A suture retriever is passed through the radius tunnel from dorsal to palmar, and one end of the graft is pulled back through the tunnel. A hemostat is passed over the ulnar head but proximal to the remaining TFCC and pushed through the volar DRUJ capsule.

The other end of the graft is grasped with the hemostat and pulled back along this tract. Both graft limbs are then passed through the ulnar tunnel to exit the ulnar neck. The limbs are passed in opposite directions around the ulnar neck, one passing deep to the ECU sheath. With the forearm in neutral rotation and the DRUJ manually compressed, the limbs are pulled taut, tied together, and secured with sutures (Figure 6.3). The dorsal DRUJ capsule and extensor retinaculum are closed in layers with 3-0 sutures, leaving the EDQ subcutaneous.

FIGURE 6.3 Tendon graft reconstruction of the DRUJ through bone tunnels.

Postoperative Management

The patient is placed in a long arm splint with the forearm in neutral to slight supination or pronation, depending on the most stable position. At the first postoperative visit at about 10 days, the patient is converted to a long arm cast extending just above the elbow to control forearm rotation. At three weeks, the cast is changed to a short arm well-molded cast that partially limits forearm rotation for an additional two to three weeks.

The patient is then converted to a removable commercial or custom wrist brace to be used for at least two more months as motion and strength are recovered. Therapy begins with active and gentle passive wrist flexion, extension, pronation, and supination. No limitations are placed on active motion, but only gentle passive motion should be used during the first month of therapy. Strengthening is started early, but high forces with the arm in full pronation and supination are avoided. At four months postoperatively, more aggressive passive ROM and strengthening are added (with the goal to recover 85% of “normal” forearm rotation by six months). No use of the hand for sports or lifting greater than ten pounds is allowed until at least four months postoperatively.