CHAPTER 29 Ligament Reconstruction/Sigmoid Notch Plasty for DRUJ Instability

The bony or ligamentous structures of the distal radioulnar joint (DRUJ) are often disrupted in association with a distal radius fracture, which is the most common cause for DRUJ instability. In some studies, up to 10% of patients with distal radius fractures had a DRUJ injury necessitating primary operative repair.¹ In addition, arthroscopy at the time of fracture identified the presence of triangular fibrocartilage complex (TFCC) injury in 43 of 51 patients examined by Lindau and colleagues.² The TFCC lesions were associated with DRUJ instability in 17 patients. Younger patients and those sustaining high-energy injuries are more likely to have DRUJ injuries in association with distal radius fractures.²

Failure to recognize and treat DRUJ disruption can contribute to a poor outcome. In particular, residual DRUJ instability after distal radius fracture is associated with worse objective and subjective outcome measures.³ When treated acutely by either closed reduction or soft tissue or bony repair, most patients will not develop DRUJ instability. However, some patients with distal radius fractures will go on to develop chronic DRUJ instability owing to failure of the soft tissues to heal or to malunion of the radius or ulna (Fig. 29-1). Multiple techniques have been described to restore stability to the chronically unstable DRUJ. These techniques can be divided into three categories: (1) a direct radioulnar tether that is extrinsic to the joint, (2) an indirect radioulnar link through an ulnocarpal sling or tenodesis, or (3) reconstruction of the distal radioulnar ligaments.

FIGURE 29-1 Chronic DRUJ instability after a distal radius fracture. Arrow points to the prominent ulnar head on the affected side.

Multiple biomechanical studies have shown that the dorsal and palmar radioulnar ligaments are key stabilizers of the DRUJ.^4,5 The radioulnar ligaments are condensations of fibers at the combined junctures of the triangular fibrocartilage articular disc, DRUJ capsule, and ulnocarpal capsule. As they pass toward the ulna, each ligament divides into superficial and deep fibers (Fig. 29-2). The superficial fibers insert on the ulnar styloid near its midportion. Disruption of the superficial fibers in the absence of other injury does not result in DRUJ instability. The deep radioulnar ligament fibers insert into the fovea on the ulnar head, which is a bony depression between the base of the styloid and the articular cartilage on the dome of the ulnar head. Disruption of these fibers can result in DRUJ instability.

FIGURE 29-2 Volar and dorsal radioulnar ligaments each divide into superficial and deep limbs. Deep limbs insert into the ulnar fovea and are more important for DRUJ stability.

Because of the importance of the dorsal and palmar radioulnar ligaments for DRUJ stability, reconstruction of these ligaments offers the best anatomical restoration of joint stability. The technique described in this chapter uses a tendon graft that nearly mimics the native ligaments. The two limbs of the tendon graft pass from the volar and dorsal margins of the sigmoid notch and converge to insert on the ulnar head at the fovea (Fig. 29-3). A recent biomechanical study by Gofton and coworkers⁶ found that this radioulnar ligament reconstruction nearly restored the kinematics of the unstable DRUJ, and it provided better joint stability than the nonanatomical reconstruction described by Fulkerson-Watson, which has been shown to provide the best stability among the radioulnar tether methods.

FIGURE 29-3 Final graft placement mimics the native insertion sites of the distal radioulnar ligaments.

Reconstruction of the soft tissue DRUJ restraints, however, will be insufficient in the presence of a substantial osseous abnormality. The articular surfaces of the DRUJ are not congruent in the normal wrist. The sigmoid notch has a radius of curvature that is much larger than that of the ulnar head (Fig. 29-4). It is a combination of ligament tension and joint compression between the ulnar head and rims of the notch that provides joint stability. The dorsal and particularly the volar rims of the notch often have fibrocartilaginous extensions or labrums that augment its relatively flat surface, which improves joint congruency and capture and thus substantially increases DRUJ stability.⁷ A developmentally flat notch or one that is deficient from injury poses greater risks to develop DRUJ instability and for the failure of a ligament reconstruction (Fig. 29-5). Sigmoid notch osteoplasty increases the prominence of the rim and improves joint stability.

FIGURE 29-4 Radius of curvature of the sigmoid notch is greater than that of the ulnar head.

FIGURE 29-5 CT of a patient with symptomatic DRUJ instability shows a flat sigmoid notch with no substantial volar or dorsal rims. Ligamentous reconstruction alone in this patient would not be sufficient to restore stability; reconstruction was augmented with a volar sigmoid notch osteoplasty.

Extra-articular deformity of the radius alone is sufficient to substantially impair DRUJ function. In cadaver studies, dorsal angulation of the distal radius or loss of radial inclination alters DRUJ mechanics and reduces forearm rotation.^8,9 Corrective osteotomy of the radius can be performed in conjunction with a radioulnar ligament reconstruction.

Surgical Technique

During the preoperative evaluation the patient should be examined for the presence of a suitable tendon graft, which is typically the palmaris longus tendon. The plantaris tendon, lesser toe extensor tendon, and a strip of flexor carpi ulnaris are alternative grafts.

The patient is positioned supine with the operative arm extended on a hand table. An upper arm tourniquet is applied. A 4-cm longitudinal skin incision is made over the interval between the fifth and sixth extensor compartments. The fifth compartment is entered, and the extensor digiti minimi is retracted. The DRUJ is identified by palpation. An L-shaped capsulotomy is made overlying the DRUJ. Its longitudinal limb extends along the dorsal rim of the sigmoid notch, stopping just short of the radiocarpal joint to preserve any remnant of the dorsal radioulnar ligament. The transverse limb extends ulnarward from the sigmoid notch, just proximal and parallel to the normal location of the dorsal radioulnar ligament (Fig. 29-6).

FIGURE 29-6 An L-shaped capsulotomy allows visualization of the sigmoid notch (arrow) and ulnar head.

The capsular flap is reflected ulnarward, allowing inspection of the TFCC, ulnar head, and sigmoid notch. TFCC repair should be performed instead of ligament reconstruction if there is sufficient tissue. If the TFCC is insufficient for repair, one can proceed with ligamentous reconstruction.

The graft may be harvested at this point, and its diameter is assessed to plan for appropriate drill size to make the bony tunnels.

The periosteum is elevated from the dorsal distal radius adjacent to the sigmoid notch. A small back-cut along the dorsal rim of the distal radius may be necessary to provide sufficient elevation and retraction of the fourth extensor compartment. A guidewire for a 3.5-mm cannulated drill is driven from dorsal to volar through the distal radius several millimeters from the articular surfaces of the lunate fossa and sigmoid notch. The distance between the guidewire and the articular surfaces must be sufficient to allow a drill hole of sufficient size that will accommodate the graft. Guidewire position is confirmed with fluoroscopy. The cannulated drill is used over the guidewire with care not to drive the guidewire into the volar tissues. If necessary, the hole is enlarged with standard drill bits (Fig. 29-7).

FIGURE 29-7 A, In this patient with a distal radius malunion, fluoroscopy is used to confirm guidewire and cannulated drill placement. Note that the drill hole is parallel to the distal radius articular surface. B, A distal radius drill hole (arrow) has been made several millimeters away from the articular surfaces of the sigmoid notch and lunate fossa.

When the surgical plan includes a corrective osteotomy for a distal radial malunion it is easier to create the radial tunnel before making the osteotomy. Whether done before or after the osteotomy, the tunnel should be made parallel to the malaligned lunate fossa. Any osteotomies should be positioned and stabilized before graft tensioning.

The distal ulna tunnel extends between the fovea and the subcutaneous border of the ulnar neck just volar to the extensor carpi ulnaris tendon. If sufficient exposure cannot be obtained by flexing the wrist and retracting the TFCC remnant, the guidewire is inserted through the fovea to exit the ulnar neck. Alternatively, in patients with stiff wrist flexion or a large wrist, the guidewire can be passed more easily in the opposite direction, that is, from the ulnar neck to the fovea. Using this latter method, a 4- to 5-mm drill hole is first made in the ulnar neck at its subcutaneous border. A guidewire is inserted in the hole and driven through the fovea. Regardless of the direction of guidewire placement, the cannulated drill should be passed from proximal (ulnar neck) to distal (fovea) to prevent damage to the carpus. One should begin with a 3.5-mm cannulated drill bit and if necessary enlarge the tunnel with standard drill bits to accommodate both limbs of the graft (Fig. 29-8).

FIGURE 29-8 A, Cannulated drill passes over the guidewire from the ulnar neck to the fovea of the ulnar head. Arrow indicates the location of the fovea. B, After removal of the surrounding soft tissues, the red vessel loop can be seen exiting the fovea in the ulnar head.

The volar 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. Careful dissection between the ulnar neurovascular bundle and finger flexors reveals the pronator quadratus and distal portion of the volar DRUJ capsule. A suture retriever is passed through to the radius tunnel from dorsal to volar. The retriever is used to pull one end of the graft from volar to dorsal through the radius. From dorsal to volar, a straight hemostat is passed just distal to the ulnar head and proximal to the residual TFCC. The volar DRUJ capsule is punctured, and the volar limb of the graft is grasped and pulled back into the dorsal wrist wound (Fig. 29-9). One should be careful not to entrap any nervous, vascular, or tendinous structures in the graft loop. Both ends of the tendon graft should now lie in the dorsal wrist exposure (Fig. 29-10).

FIGURE 29-9 Suture passer is seen to the right in this image, while the tip of the hemostat is to the left. Hemostat grasps one end of the graft (long arrow) while the other graft end is placed in the suture retriever loop (short arrow). (A red vessel loop has been used instead of tendon graft in this cadaver specimen for illustrative purposes.)

FIGURE 29-10 Both limbs of the tendon graft exit into the dorsal wound—one limb exiting through the distal radius tunnel (short arrow), and the second limb though the volar DRUJ capsule just distal to the ulnar head (long arrow).

The suture retriever is passed through the distal ulna tunnel from the neck to fovea, exiting in the dorsal wound. Both limbs of the tendon graft are pulled back through the ulna to exit at the ulnar neck (Fig. 29-11). A hemostat is passed ulnarward under the extensor carpi ulnaris sheath at the ulnar neck and used to pull one limb of the graft toward the radius (Fig. 29-12). From the dorsal exposure, a right-angled clamp is passed volarly around the ulnar neck to grasp the second graft limb and pull it back around the neck. Both limbs of the tendon graft should now be resting on the dorsal ulnar neck (Fig. 29-13).

FIGURE 29-11 A suture retriever is used to pass both ends of the tendon graft through the distal ulna tunnel to exit at the ulnar neck (arrow).

FIGURE 29-12 A hemostat pulls one end of the tendon graft over the dorsal ulnar neck and beneath the extensor carpi ulnaris sheath (long arrow). The short arrow indicates the location of the extensor digiti minimi tendon.

FIGURE 29-13 A right-angled clamp passes around the volar ulnar neck to retrieve the other end of the tendon graft.

The two graft limbs are pulled taut and tied in a half-hitch while the forearm is held in neutral rotation and manual pressure is applied to compress the DRUJ (Fig. 29-14). The half-hitch is secured with 3-0 nonabsorbable sutures (Fig. 29-15). The dorsal DRUJ capsule and the extensor retinaculum are closed in a single layer, with care to avoid the extensor tendons (see Fig. 29-20). The extensor digiti minimi tendon is left superficial over the DRUJ. A temporary large-diameter Kitschner wire (K-wire) may be placed across the DRUJ if desired but I very rarely do this.

FIGURE 29-14 While holding the DRUJ reduced, the two ends of the graft are pulled taut and tied in a half-hitch over the ulnar neck. The ECU sheath is being retracted by the rake retractor (right).

FIGURE 29-15 Final appearance of the graft from the dorsal wrist wound. The graft is seen exiting the radial drill hole (short arrow) and entering the fovea on the ulnar head (long arrow).

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 10 days, the patient is converted to a long arm cast extending to just above the elbow to control forearm rotation. Three weeks later the cast is changed to a short arm well-molded cast that partially limits forearm rotation for an additional 2 to 3 weeks.

The patient is then converted to a removable wrist brace to be used for an additional 2 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 4 months after the surgical procedure, more aggressive passive range of motion and strengthening exercises are added. No use of the hand for sports or other stressful activities is allowed until at least the fourth month after surgery.

If the sigmoid notch is flat or deformed, then an osteoplasty may be performed at the same setting as the DRUJ ligament reconstruction. Sigmoid notch osteoplasty augments the volar or dorsal rim of the sigmoid notch to increase DRUJ stability. Wallwork and Bain¹⁰ originally described the sigmoid notch osteoplasty for the volar rim, but the same technique may also be used to augment the dorsal rim.

The osteoplasty may be performed through the same volar or dorsal approach used for DRUJ ligament reconstruction. For the volar side, the periosteum is incised and raised 3 to 4 mm radial to the rim of the sigmoid notch (see Fig. 29-16). For the dorsal side, the previously incised capsule is raised in continuity with the adjacent periosteum. With the use of a small osteotome, a transverse cut about 4 mm deep is made in the rim of the notch at its proximal edge (Fig. 29-17). A second parallel osteotomy is made 2 to 3 mm proximal to the radiocarpal joint. A longitudinal cut about 4 mm from the margin of the rim connects the two transverse limbs. If a simultaneous ligament reconstruction is part of the surgical plan, the radial drill hole is made first. The longitudinal limb of the osteotomy passes through the ulnar margin of the radial drill hole (Fig. 29-18). The osteotome is slowly advanced to the depth of the longitudinal cut (one-fourth to one-third the width of the radius) and used to gently lever the rim a few millimeters toward the ulna. The articular cartilage and subchondral bone are bent but not broken through. The gap is filled with bone graft harvested from the nearby distal radius (Fig. 29-19). The tendon graft should be passed through the distal radius drill hole but not tensioned before bone graft placement. Because the tendon graft will pass directly over the bone graft when tensioned in its final position, it will typically secure the bone graft, but sutures through the nearby periosteum can be added (Fig. 29-20).

FIGURE 29-16 Bony surface of the radius adjacent to the volar rim of the DRUJ is exposed (short arrow) extending to the exit of the radial tunnel (long arrow).

FIGURE 29-17 A small osteotome is used to make the proximal cut of the osteoplasty at the proximal margin of the sigmoid notch.

FIGURE 29-18 An osteotome is used to make the second transverse limb parallel to both the lunate fossa and the proximal osteotomy. The longitudinal cut of the osteotomy passes through the ulnar edge of the radial tunnel (arrow).

FIGURE 29-19 A, Osteotomy fragment is gently levered toward the ulnar head, which should bend but not break the articular cartilage and subchondral bone. The lines are adjacent to the proximal and distal osteotomy cuts. B, Oblique view of the wrist with the DRUJ distracted shows the intact articular cartilage of the sigmoid notch (arrow).

FIGURE 29-20 Tendon graft has been passed through the radial tunnel and into ulna tunnel. A small wedge of bone graft from the distal radius is wedged into the defect left by the osteotomy (shown as a blue spacer). Tension on the tendon graft secures the bone graft and the osteotomy position. The lines indicate the proximal and distal osteotomy cuts.

The addition of a sigmoid notchplasty does not alter the postsurgical management except that the long arm immobilization is used for the first 6 weeks instead of 4 weeks; however, the time in the short arm cast can be reduced to 2 weeks.