Scapholunate Interosseous Ligament Sectioning Research Articles

The role of scapholunate interosseous, dorsal intercarpal, and radiolunate ligaments in wrist biomechanics

Rupture to wrist ligaments predisposes the joint to degenerative changes. Scapholunate interosseous ligament (SLIL) rupture, especially when compounded by dorsal intercarpal ligament (DIC) and long radiolunate ligament (LRL) disruption, can cause carpal bone kinematic abnormalities. It is essential to delineate the role of these ligaments and their constraints on wrist range-of-motion (ROM) and center of rotation (COR). Wrist ROM and COR location were determined in 9 specimens using a six degree-of-freedom robotic musculoskeletal simulator in 24 directions of wrist motion for four experimental conditions: intact, and after sequential sectioning of the SLIL, DIC, and LRL. Sectioning the SLIL alone did not change wrist ROM in any direction (p > 0.10), while sectioning the SLIL and both the DIC and LRL caused significant increases in radial deviation, radial-extension, and ulnar-flexion ROM (p < 0.05). The COR of the intact wrist was located between the proximal third and middle third of the capitate, depending on the direction of wrist motion. While SLIL sectioning alone did not affect the COR, subsequent DIC sectioning led to a distal shift of COR in motions involving ulnar-extension relative to the intact condition. Additional sectioning of the LRL caused a proximal shift of COR in motions involving radial-flexion. A proximal shift implies a more dominant role of the radiocarpal joint, while a distal shift of the COR implies an increased role for the midcarpal joint. Understanding the role of ligaments on overall wrist mechanics is critical to devising new treatment strategies to restore wrist function.

Effect of Push-Up Position on Wrist Joint Pressures in the Intact Wrist and Following Scapholunate Interosseous Ligament Sectioning.

To determine the contact pressures between the scaphoid and lunate and the distal radius during 2 wrist push-up positions before and following scapholunate interosseous ligament (SLIL) sectioning. Eight fresh cadaveric wrists were tested in a neutral flexion-extension (knuckle) push-up position and in an extended push-up position. Pressure measurements were acquired as each wrist was loaded with the wrist in extension and with the wrist in a neutral position. Data were acquired with the SLIL intact and following sectioning of its dorsal, volar, and proximal components. The wrist was disarticulated and a map drawn on each sensor to identify each joint fossa. A push-up performed with the wrist in extension caused a significantly greater peak pressure in the radioscaphoid fossa but not in the radiolunate fossa. Moving the wrist into extension caused a significant dorsal movement of the pressure centroid an average of 2.9 mm in the radiolunate fossa and an average of 5.7 mm in the radioscaphoid fossa. Sectioning the SLIL caused the centroid of pressure in the radioscaphoid fossa to significantly move an average 1.4 mm radially. A push-up with the wrist in extension causes a significant increase in the pressure in the radioscaphoid fossa but not in the radiolunate. This finding may help explain why degenerative arthritis first develops in the radioscaphoid fossa before involving the radiolunate fossa. As expected, gapping that occurs with SLIL injury was observed here as a radial translation of the scaphoid and not as a movement of the lunate. The new location of scaphoid contact may be an additional reason for the development of radioscaphoid arthritis occurring before radiolunate arthritis. This study provides a possible explanation as to why degenerative arthritis may first occur in the radioscaphoid fossa.

Biomechanical Evaluation of Scaphoid and Lunate Kinematics Following Selective Sectioning of Portions of the Scapholunate Interosseous Ligament

To determine the relative roles of the dorsal and volar portions of the scapholunate interosseous ligament (SLIL) in the stability of the scaphoid and lunate. Sixteen fresh cadaver wrists were moved through physiological motions using a wrist joint simulator. Electromagnetic sensors measured the motion of the scaphoid and lunate. Data were collected with the wrist intact, after randomly sectioning the dorsal SLIL first (8 wrists) or the volar SLIL first (8 wrists), and after full ligamentous sectioning. Differences in the percent increase in scaphoid flexion or lunate extension were compared using a t test with significance set at P < .05. Sectioning the dorsal SLIL accounted for 37%, 72%, and 68% of the increase in scaphoid flexion in wrist flexion-extension, radioulnar deviation, and dart throw motion as compared with complete SLIL sectioning. Sectioning the volar SLIL accounted for only 7%, 6%, and 14%, respectively. In the same 3 motions, sectioning the dorsal SLIL accounted for 55%, 57%, and 58% of the increase in lunate extension, whereas volar SLIL sectioning accounted for 27%, 28%, and 22%. The dorsal SLIL provides more stability to the scaphoid and lunate in biomechanical testing. The volar SLIL does provide some, although less, stability. Although this study supports the critical importance of dorsal SLIL repairs or reconstructions, it also shows that there may be some value in implementing a volar SLIL repair or reconstruction.

The role of SLIL in 3D movement of scaphoid and lunate during wrist radio-ulnar deviation

Objective To observe the effects of transection of scapholunate interosseous ligament (SLIL)and its subregions on the 3D movement of scaphoid and lunate during wrist radio-ulnar deviation, and study the rule of SLIL subregions in 3D motion of the scaphoid and lunate. Methods Twelve fresh adult cadaver upper extremities (6 left side and 6 right side) were divided to normal control group, proximal SLIL subregion transection group, proximal and dorsal SLIL subregion transection group, proximal and palmar SLIL subregion transection group and entire SLIL transection group (6 each). 3D laser scanning and reconstruction techniques were applied to measure 3D motion of the scaphoid and lunate during wrist radio-ulnar deviation, and data were statistically analyzed, on the normal and sequential sectioning of SLIL subregions during wrist flexion-extension and wrist radlal-ulnar deviation were determined. Results In the intact wrist specimens, the scaphoid and lunate deviated radially and ulnarly during wrist radial-ulnar deviation, along with obvious flexion and extension.At the same time, there was minimal scaphoid and lunate pronation-supination. With sectioning of proximal subregions of the SLIL, no significant kinematics changes were observed in the scaphoid and lunate bones. After sectioning proximal and palmar or proximal and dorsal subregions of the SLIL, kinematics of the scaphoid and lunate were changed. Sectioning the whole SLIL caused increased volar flexion of the scaphoid and decreased volar flexion of the lunate. Conclusion 3D laser scanning and reconstruction can precisely measure 3D motion of the scaphoid and lunate. Kinematic study of SLIL subregions showed that partial or complete sectioning of SLIL led to obvious change in volar flexion of the scaphoid and lunate. However, the proximal subregion of SLIL has no prominent effect on the motion of scaphoid and lunate. Key words: Carpal joints; Scaphoid bone; Lunate bone; Ligaments,articular; 3D movement

The Hysteresis Effect in Carpal Kinematics

Carpal bones show hysteresis that is dependent on the direction of wrist motion during a continuous active loading protocol. We describe an accurate methodology for analyzing the hysteresis effect and we apply this model to analyze the effect of sequential ligament sectioning on scapholunate instability. In 8 fresh cadaver forearms scaphoid, lunate, and third metacarpal motions were recorded while each wrist was moved in continuous cycles of active motion in flexion-extension and radioulnar deviation. Motions were analyzed for the intact state and after sequential sectioning of the scapholunate interosseous, scaphotrapezium, and radioscaphocapitate ligaments. Carpal motion was curve-fitted with respect to the third metacarpal motion using optimization criteria. The area between the 2 curves that represents opposite directions of wrist motion was measured to give the total hysteresis area. Repeated-measures analysis of variance was used to determine significance. In the flexion-extension trials the scaphoid and lunate total hysteresis area was significantly greater than the intact state only after all 3 ligaments were sectioned. In the radioulnar deviation trials the scaphoid total hysteresis area was significantly greater than the intact after just scapholunate interosseous ligament sectioning; however, the lunate total hysteresis area decreased with additional sequential sectionings in 4 of the 8 specimens as compared with the intact state. These 4 specimens started with a significantly greater intact total hysteresis area than the other 4 specimens. The computation of the total hysteresis area from the hysteresis effect was found to be a sensitive technique to determine the subtle onset of abnormal carpal motion. By using this technique in a ligament sectioning study significant increases in the total hysteresis area were seen after just scapholunate interosseous ligament sectioning during wrist radioulnar deviation. This subtle change may signify the onset of dynamic scapholunate instability. The total hysteresis area of the lunate in a subset of lax specimens did not increase after ligament sectioning. This divergent behavior may explain why some patients with scapholunate instability do not develop dorsal intercalated segmental instability.

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

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, 110±6% and 105±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 FCU tendons decreased after SLIL sectioning and the SL joint widening. However, moment arms of the FCR tendon significantly increased 122±23% after the SLIL section, 133±28% after the moderate SL joint widening, and 138±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.

Dorsal intercarpal ligament capsulodesis for scapholunate dissociation: biomechanical analysis in a cadaver model.

The purpose of this study was to evaluate in cadavers a new method for treating scapholunate dissociations, dorsal intercarpal ligament capsulodesis (DILC), and to compare its performance with that of a previously described soft tissue reconstruction, Blatt capsulodesis (BC). A cadaver model was used to simulate normal and abnormal wrist motions. The positions of the scaphoid and lunate and their changes with wrist motion and ligament condition were recorded using biplanar radiographs taken posteroanteriorly and laterally. The scapholunate gap was measured on the posteroanterior radiographs and the scapholunate angle was measured on the lateral view radiographs. Following scapholunate interosseous ligament sectioning, a diastasis developed between the scaphoid and lunate that was maximum in the clenched fist position 2.1 +/- 0.33 mm (mean +/- SEM) with the ligament intact versus 8.0 +/- 1.74 mm after the ligament was sectioned. Dorsal intercarpal ligament capsulodesis reduced gap formation more than BC, including when the specimens were in the clenched fist position: increased gap versus intact specimens equals 1.0 mm for DILC versus 3.7 mm for BC. The differences in diastasis were statistically significant between BC and DILC when the wrist was in extension, radial deviation, and clenched fist positions. After the scapholunate interosseous ligament was divided, the scaphoid flexed relative to the lunate. Both capsulodeses improved scapholunate alignment and there was a trend for DILC to correct the scapholunate angle more than BC. The results demonstrate that DILC is an attractive alternative to BC ex vivo. Because DILC does not tether the scaphoid to the distal radius, as BC does, improved wrist motion, especially flexion, might be possible in vivo. The use of DILC in the treatment of scapholunate dissociation warrants further investigation and clinical trials.

Scapholunate interosseous ligament sectioning adversely affects excursions of radial wrist extensor and flexor tendons

Excursions of tendons around the scaphoid were measured in 6 fresh cadaver forearms to evaluate the role of the scapholunate interosseous ligament (SLIL) in wrist joint motion. Excursions of the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons and the flexor carpi radialis (FCR) tendon were continuously recorded during wrist flexion, extension, and radial and ulnar deviation. Tendon excursions were measured in the intact wrists and after complete sectioning of the SLIL. Tendon excursions were altered significantly in the major ranges of wrist motion after SLIL sectioning. After ligament sectioning, excursions of the ECRL and ECRB tendons increased significantly in wrist flexion and extension. Excursions of the FCR tendon increased significantly during wrist extension and ulnar deviation. These findings support the concepts that integrity of the SLIL plays an important role in wrist function and that injury of the ligament may cause clinical problems.