Wrist kinetics after scapholunate dissociation: the effect of scapholunate interosseous ligament injury and persistent scapholunate gaps

Abstract

The purpose of this study was to investigate the effects of cutting of the scapholunate interosseous ligament (SLIL) and persistent widening of the scapholunate (SL) joint on changes in moment arms of the principal wrist motor tendons. In seven fresh frozen cadaveric upper extremities, excursions of the extensor carpi radialis longus (ECRL) and brevis (ECRB), extensor carpi ulnaris (ECU), flexor carpi radialis (FCR), and flexor carpi ulnaris (FCU) were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, then in the wrists with complete SLIL sectioning and in those with moderate or severe persistent SL joint widening. The data were converted to moment arms of the tendons. The results showed that moment arms of the ECRL and ECRB tendons after SLIL sectioning were, respectively, 1 10 f 6' !,0 and 105 ! C 3% of those in the intact wrist. In the wrists with moderate or severe SL joint widening, moment arms of the flexors significantly increased ( P < 0.01 and P < 0.001, respectively). During radioulnar deviation, moment arms of the ECRL, ECRB, ECU, and F C U tendons decreased after SLIL sectioning and the SL joint widening. However, moment arms of the FCR tendon significantly increased 123 f 23'%1 after the SLIL section, 133 i 38% after the moderate SL joint widening, and 138 i 24%) after the severe SL joint widening compared with those of the intact wrists. This study demonstrated that integrity of the SLIL and appropriate SL joint space are important for mechanics of wrist motor tendons. Loss of integrity of the SLIL and persistent SL joint widening increase mechanical effects of the radial side wrist motor tendons, which may contribute to the pathomechanics of scaphoid malrotation, scapholunate advanced collapse, and early osteoarthritis in the radioscaphoid joint interface seen in SL dissociation. The results also suggest that reduction of the displaced SL joint is imperative to the recovery of wrist kinetics after SL dissociation.

General Innervation Pattern and Sensory Corpuscles in the Scapholunate Interosseous Ligament

“…Whether certain ligaments in the human body are designed to be mere static stabilizers and others to have a sensory function thus remains an unresolved issue. The scapholunate interosseous ligament (SLIL) is a carpal ligament assigned great importance regarding the biomechanical stability and load transfer of the wrist [Short et al, 2002], since rupture of the SLIL results in gross alterations in wrist kinematics [Garcia-Elias, 1999;Tang et al, 2002] and progressive carpal instability [Linscheid and Dobyns, 1992]. The proximal region of the ligament corresponds to the area articulating with the distal radius and consists mainly of fibrocartilage.…”

A case of bilateral scapholunate advanced collapse in a Romano-British skeleton from Ancaster

“…Eventually, the capitate migrates proximally into the gap which appears between the scaphoid and the lunate as a result of the rotation of the scaphoid (SLAC stage IIIb), with DJD occurring at the scaphocapitate joint. At all of these stages, the radiolunate joint remains unscathed (Metz et al, 1997;Stabler et al, 1997;Cooney et al, 1998;Tang et al, 2002). The radiographic diagnosis and staging of SLAC wrist in modern clinical cases therefore depends on assessing the progression of degenerative changes seen at the radioscaphoid and intercarpal joints, as evidenced by loss of joint space and sclerosis (see Figure 6).…”

“…Rupture of the SLIL allows the scaphoid to rotate, opening up a gap between the scaphoid and the lunate, and this irrevocably alters wrist kinetics allowing the development of SLAC wrist (Tang et al, 2002). The widening gap between the scaphoid and lunate allows the head of the capitate to migrate proximally, which is the characteristic pattern seen in SLAC.…”

Scapholunate Stabilization With Dynamic Extensor Carpi Radialis Longus Tendon Transfer

“…Outcomes are related to injury severity, the timing of treatment, and the ability to re-establish durable scapholunate reduction and normal carpal kinematics. 6,7 Independent repairs of the SLIL have been unreliable owing to intrinsic musculotendinous, entropic, and external forces acting across the wrist joint and stressing the repair site.…”

“…[5][6][7] Scapholunate reduction and pinning, with or without debridement, or repair of the disruption in the space of Poirier between the radioscaphocapitate ligament and long radioscapholunate ligament often attenuate over time. 6 Thermal shrinkage has frequently been effective for chronic partial SLIL tears.…”