Rationale and Basic Science Pertinent to the Procedure

Scapholunate instability is the most common form of carpal instability. Injury to the scapholunate interosseous ligament leads to alterations in the kinematic loads passing through the radiocarpal joint and a progressive degeneration of the secondary stabilizers of the carpus.¹ Eventual deterioration of these secondary stabilizers leads to fixed changes within the lunate and midcarpal joint leading to radiocarpal and midcarpal arthritis. Early within this process of scapholunate instability, pain is present over the dorsum of the wrist as overload to the remaining scapholunate ligament results in scaphoid subluxation, synovitis, and internal ligamentous strain.^2,3

Despite its frequency, a standardized treatment protocol for scapholunate instability has not been established. Several surgical procedures have been recommended for the treatment of this disease process, including scaphotrapeziotrapezoidal and scaphocapitate fusion, capsulodesis alone, ligament repair in conjunction with dorsal capsulodesis, tenodesis, and bone-ligament-bone reconstruction.^1,4–12

Tenodesis, in particular, attempts to re-establish the scapholunate relationship and scapholunate interosseous ligament through the use of various tendon weaves. Palmer and colleagues¹³ described the use of the extensor carpi radialis longus tendon, which is routed through the tuberosity of the scaphoid, brought out dorsally through the lunotriquetral ligament, and then buried into a hole in the capitate. Taleisnik¹⁴ used a strip of the flexor carpi radialis passed from palmar to dorsal through the lunate and into the scaphoid to recreate the dorsal scapholunate ligament. The graft is then introduced into a drill hole in the radius to create a deep radioscapholunate ligament. Many clinical series using similar tenodesis techniques have reported good results; however, because of the technical demands of these procedures and the complication associated with multiple bone tunnels, many of these procedures were abandoned in favor of scaphotrapeziotrapezoidal fusion or dorsal capsulodesis.^13–15 Inherently, any tenodesis procedure has attendant difficulties in tensioning the carpal bones because the elastic modulus of tendon is much larger than that of ligament. A reconstructed ligament that is snug enough to restore the scapholunate relationship would often result in a significant restriction in wrist motion that may approximate that following a partial wrist fusion.

In 1995, Brunelli and Brunelli⁷ described a tenodesis technique using a slip of the flexor carpi radialis tendon that is tunneled through the distal portion of the scaphoid and attached to the distal radius to correct the abnormal scaphoid flexion deformity and to stabilize the scapholunate interval. Brunelli’s original assumption was that rotary subluxation of the scaphoid is best corrected by stabilization of the scaphotrapeziotrapezoid ligament, rather than by reinforcing the scapholunate interosseous ligament.^7,16 Although this theory itself is still controversial, Brunelli’s results were encouraging. In addition, the procedure itself required less bone tunneling with minimal destruction of the volar carpal ligaments. The initial results with the Brunelli repair have been comparable to the results reported for dorsal capsulodesis.^7,17,18

Modifications of Brunelli’s original procedure have been described by Van Den Abbeele and colleagues and Garcia-Elias and colleagues.^3,18,19 This modified technique involves tunneling the flexor carpi radialis tendon through the scaphoid from the distal pole to the dorsal tuberosity, in contrast to Brunelli’s original description, in which the flexor carpi radialis is passed parallel to the scaphotrapeziotrapezoidal joint surface. The tendon is passed through the dorsal radiocarpal ligament, which also has been referred to as the dorsal radiolunotriquetral ligament. The distal end of the tendon is flipped back and secured to itself and the underlying lunate. This also is in contrast to Brunelli’s original description, in which the flexor carpi radialis graft was originally anchored to the dorsal distal radius. This modified technique (now termed the “three-ligament tenodesis” because the weave is believed to stabilize the scaphotrapeziotrapezoidal, scapholunate interosseous, and dorsal radiocarpal ligaments) has yielded encouraging medium-term results for chronic scapholunate instability.^3,19

Pertinent Anatomy

Adequate execution of the tenodesis procedure is predicated on a thorough understanding of wrist anatomy, including the secondary ligamentous constraints of scaphoid motion and the dorsal and volar wrist capsule. The ligaments of the wrist can be divided into two general categories. The first category includes the interosseous ligaments, which run between carpal bones and include the scapholunate and lunotriquetral interosseous ligaments (Fig. 49-1A). These two ligaments are the major stabilizers of the proximal carpal row and carpus.^20,21 The scaphotrapeziotrapezoidal ligament, also an interosseous ligament, connects the scaphoid with the trapezium and trapezoid (Fig. 49-1B).^22,23 Garcia-Elias and others^24–26 characterized the distal ligament connections of the scaphoid further into two separated complexes—the mediolateral scaphotrapeziotrapezoidal ligament and the anteromedial scaphocapitate ligament; both ligaments provide distal support to the scaphoid.

FIGURE 49-1 Intrinsic ligaments of the wrist are ligaments that originate and insert among the carpal bones. A, Dorsal view of the wrist shows the scapholunate (SL), lunotriquetral (LT), trapeziotrapezoid (TT), capitotrapezoid (CT), and capitohamate (CH) intrinsic ligaments. B, Volar view of the wrist illustrates the volar aspect of the same ligaments in addition to the scaphotrapeziotrapezoid (STT), scaphocapitate (SC), triquetrocapitate (TC), and triquetrohamate (TH) ligaments.

(Copyright Mayo Clinic; reproduced with permission of the Mayo Foundation.)

The second group of ligaments comprises the extrinsic wrist ligaments, which connect the forearm bones to the carpal bones. There are palmar and dorsal extrinsic wrist ligaments. These tend to serve as secondary stabilizers of carpal motion. The palmar extrinsic ligaments form a configuration of two “V”-shaped bands with a space between the bands. This space or gap, which has minimal ligamentous support and is an inherent point of weakness, is known as the space of Poirier (Fig. 49-2A). The dorsal carpal ligaments include the dorsal intercarpal and dorsal radiocarpal ligaments. These extrinsic ligaments are thinner and weaker than their palmar counterparts, but also provide structural support to the carpus (Fig. 49-2B).

FIGURE 49-2 Extrinsic ligaments of the wrist include ligaments that originate outside the carpal bones and insert onto the carpal bones. A, From a volar view, the proximal ligaments from radial to ulnar include the radioscaphocapitate (RSC), long radiolunate (LRL), short radiolunate (SRL), ulnolunate (UL), ulnocapitate (UC), and ulnotriquetral (UT). AIA, anterior interosseous artery; C, capitate; H, hamate; P, pisiform; PRU, palmar radioulnar ligament; R, radius; RA, radial artery; S, scaphoid; T, triquetrum; Td, trapezoid; Tm, trapezium; U, ulna. B, From a dorsal view, there is only one true extrinsic ligament, the radiotriquetral or dorsal radiocarpal (DRC) ligament. The scaphotriquetral or dorsal intercarpal (DIC) ligament is by definition an intrinsic ligament, but is easier to illustrate here.

(Copyright Mayo Clinic; reproduced with permission of the Mayo Foundation.)

The volar extrinsic ligaments, which act as major secondary constraints of scaphoid motion, include the radioscaphocapitate ligament, long radiolunate ligament, scaphotrapezial ligament, and scaphocapitate ligament (see Fig. 49-2A). The radioscaphocapitate ligament originates from the radial palmar rim of the radius and passes beneath the scaphoid waist to attach to the capitate. During its course, it gives off attachments to the lunate.²⁷ These fibers interdigitate with fibers from the ulnocapitate ligament to form the so-called arcuate ligament of the wrist.²⁸ The long radiolunate ligament lies ulnar to the radioscaphocapitate ligament and may also support the scapholunate relationship through its direct connections to the palmar component of the scapholunate interosseous ligament (see Fig. 49-2A).^29,30 Short and coworkers^31,32 showed that after disruption of the scapholunate interosseous ligament, division of the scaphotrapezial and radioscaphocapitate ligaments results in additional instability in scapholunate motion.

Important secondary dorsal stabilizers of the scapholunate joint include the dorsal intercarpal and dorsal radiocarpal ligaments. The dorsal intercarpal ligament originates from the dorsal ridge of the triquetrum and attaches to the dorsal distal aspect of the lunate and into the dorsal rim of the scaphoid. The ligament gives attachments to the scapholunate interosseous ligament and lunotriquetral interosseous ligament during its course.³² The dorsal radiocarpal ligament, or the dorsal radiolunotriquetral ligament, originates from the dorsal margin of the distal radius just ulnar and distal to Lister’s tubercle. The ligament extends obliquely with fibers inserting into the lunate, inserting into the lunotriquetral interosseous ligament, and finally inserting into the dorsal ridge of the triquetrum.³² The dorsal intercarpal and dorsal radiocarpal ligaments create a “V” shape over the dorsal wrist capsule and contribute to the stability of the scaphoid and lunate (see Fig. 49-2B). Viegas and others^33,34