Scapholunate ligament repair

Introduction

• The scapholunate (SL) ligament is a commonly injured wrist ligament. A complete SL ligament injury that is not treated can progress to pancarpal arthritis, as described later, making the diagnosis and repair of SL ligament injuries important.

• The SL ligament is the primary stabilizer of the scapholunate joint. As a stabilizer , the SL ligament prevents the scaphoid and lunate from moving independently at the SL joint. If disrupted, the scaphoid tends to flex (volarly), whereas the lunate tends to extend (dorsally) when viewed from a lateral radiograph.

• The secondary stabilizers of the SL joint are the scaphotrapeziotrapezoid (STT), scaphocapitate (SC), and radioscaphocapitate (RSC; Fig. 21.1A–B ). These are volar structures and resist the scaphoid’s tendency to flex; in this way, they are secondary stabilizers. The STT and SC are volar intrinsic ligaments, whereas the RSC is a volar extrinsic ligament.

  

• If an SL ligament injury is severe enough and does not spontaneously heal, the primary stabilizer is lost and the secondary stabilizers become stressed.

• Over time, loss of the secondary stabilizers permits scaphoid flexion and changes in wrist biomechanics, leading to a spectrum of dysfunction known as scapholunate advanced collapse (SLAC).

• The endpoint of SLAC is pancarpal arthritis; therefore timely identification and repair of an SL ligament injury can prevent the development of pancarpal arthritis.

Staging

• SL ligament injuries exist along a continuum, and different treatments exist for different stages along this continuum.

• Table 21.1 presents a staging system that shows the progression from partial injury (stage I) to arthritis (stage VI).

  TABLE 21.1

  Staging System for Scapholunate Dissociation

  Adapted from: Garcia-Elias M, Lluch AL, Stanley JK. Three-ligament tenodesis for the treatment of scapholunate dissociation: Indications and surgical technique. J Hand Surg Am. 2006;31(1):125–134.)

  Stage	Definition
  I	Partial SL ligament injury (“predynamic”)
  II	Complete disruption that is reparable, with normal static scapholunate alignment (“dynamic”)
  III	Complete disruption that is not reparable but has normal static scapholunate alignment (“dynamic”)
  IV	Complete disruption that is not reparable, with static volar flexion of the scaphoid that can be reduced to normal (“static”)
  V	Complete disruption that is not reparable, with volar flexion of the scaphoid that cannot be reduced to normal, but the cartilage surfaces are intact (“static”)
  VI	Complete disruption that is not reparable, with volar flexion of the scaphoid that cannot be reduced to normal, with cartilage degeneration (scapholunate advanced collapse [SLAC])

  SL, Scapholunate.

• The dorsal SL ligament is strongest and most important. Stage I indicates an incomplete SL ligament tear involving only the volar and proximal portions ( Fig. 21.2 ) with an intact dorsal aspect of the SL ligament. This is also known as predynamic because the scaphoid does not move with provocative testing or imaging.

  

• Stages II and III both have complete SL ligament disruptions and normal carpal alignment; however, the distinction is whether the SL ligament is reparable. Progression from stage II to III is influenced by both time and the location of the tear. Complete SL ligament injuries older than 6 weeks are usually irreparable and are generally described as chronic injuries. Meanwhile, midsubstance tears are often harder to repair over time than avulsion-type injuries.

• For complete SL ligament tears in both stages II and III, there may be widening of the SL interval with stress views such as a clenched fist view, so these stages are known as dynamic .

• The progression from stages II and III to IV and V reflects a loss of the secondary stabilizers. With disruption of the primary stabilizer (SL ligament) and secondary stabilizers (STT, SC, RSC), the scaphoid flexes and the lunate extends. Early on, the scaphoid can be reduced to its normal alignment. With time, fibrosis can make reduction impossible, thereby distinguishing stages IV and V. (Of note, scaphoid flexion is only considered “reducible” and therefore stage IV, if only mild force is needed to reduce the scaphoid. If tremendous force is required, current reconstruction techniques will not maintain reduction, and therefore it is classified as not reducible, stage V).

• Eventually, abnormal wrist biomechanics leads to wrist arthritis through a predictable pattern known as SLAC wrist (stage VI).

The authors’ preferred operative technique will be presented for stages I and II. Chapter 22 will review treatment for stages III to VI.

The Geissler arthroscopic classification is another system used to grade the severity of SL ligament injuries ( Table 21.2 ); however, it is not as complete as the aforementioned system.

Indications and contraindications

• Patients with diagnosed SL ligament injuries who present with wrist pain should generally receive treatment that is appropriate for the stage of their injury.

• The only exception is if a patient presents without pain and no obvious injury within 6 weeks; these patients are typically left untreated.

• This is guided by clinical experience because no randomized trials can offer guidance on this recommendation.

Clinical examination

• Patients present with radial-sided wrist pain, particularly with axial loading, power grip, and with extremes of wrist extension and radial deviation.

• An SL ligament tear results in tenderness over the scaphoid in the anatomic snuff box and distal to the Lister tubercle over the scapholunate interval.

• Many provocative tests exist to aid in diagnosis:

  • The carpal shake test involves passively shaking the wrist into extension and flexion by grasping the forearm. If this does not elicit pain or resistance to movement, then carpal pathology is unlikely.

  • The sitting hand test involves weight-bearing/loading the wrist as the patient rises from the seated position to standing. If this elicits pain, then it is suspicious for wrist pathology.

  • The scaphoid shift test ( Fig. 21.3A–B ) is the bimanual examination of the scaphoid in relation to the radius. One hand is used to apply pressure dorsally over the distal radius while the thumb presses on the distal pole of the scaphoid. The examiner’s opposite hand is then used to passively move the hand from ulnar to radial deviation. With SL ligament laxity or tear, the proximal pole of the scaphoid subluxes dorsally out of its fossa, which can result in pain along the SL interval. With release of pressure on the distal scaphoid, an audible and palpable clunk can be appreciated with reduction of the scaphoid back into its fossa.

    

  • Resisted long finger extension is when the patient extends the long finger with resisted extension and partial flexion of the wrist. This may elicit pain over the SL interval, which lies directly under the long finger extensor tendon.

  • To complete the SL ballottement test, after firmly stabilizing the lunate with one hand, the opposite hand is used to translate the scaphoid dorsally and volarly. Pain, crepitus, or mobility suggests disruption of the SL interval.

Imaging

• Standard wrist x-rays will only identify static SL instability, showing a widened SL interval ( Fig. 21.4A–C ) or flexed scaphoid.

  

• Additional views are known as stress views and include clenched fist, posteroanterior (PA) maximal radial deviation, and PA maximal ulnar deviation (scaphoid view).

• Arthroscopic evaluation is the reference standard for diagnosis of SL injuries, particularly predynamic and dynamic injuries.

• The Geissler arthroscopic classification of SL ligament injuries can both diagnose an SL tear and examine the articular surface for signs of degeneration (see Table 21.2 ).

Surgical anatomy

• The SL ligament can be found distal to the Lister tubercle and deep to the dorsal wrist capsule between the second and fourth dorsal extensor compartments.

• The SL ligament is a U-shaped ligament consisting of palmar, proximal, and dorsal fibers. The dorsal ligament is the strongest of the ligamentous complex (see Fig. 21.2 ).

• Wrist kinematics are governed by the primary (intrinsic) and secondary (extrinsic) ligamentous stabilizers of the wrist. The primary stabilizer of the scaphoid and lunate is the SL ligament. The secondary stabilizers of importance in scapholunate injury include the volar STT, SC, and RSC ligaments (see Fig. 21.1 ).

• Predynamic scapholunate instability represents a partial ligament injury that results in pain but cannot be appreciated on plain x-ray. Diagnosis can be confirmed by arthroscopy, which may reveal attenuation, hemorrhage, or a partial tear of the scapholunate ligament (see Table 21.1 ).

• With complete disruption of the scapholunate ligament and preservation of the secondary stabilizing ligaments, dynamic instability can be appreciated. This refers to an injury pattern in which the scapholunate interval widens with activation of extrinsic muscular forces across the wrist. With axial loading, such as clenching the fist, radiographs will demonstrate an increase in the scapholunate interval ( Fig. 21.5 ).

  

• After complete scapholunate injury and attenuation or rupture of the secondary stabilizing ligaments, static carpal malalignment results. This refers to fixed gapping of the scapholunate interval (≥4 mm; Terry Thomas sign) and flexion of the scaphoid (Signet ring sign) with or without extension of the lunate ( Fig. 21.6 ).