Scapholunate Interosseous Ligament Anatomy and Biomechanics

doi:10.1016/j.jhsa.2015.03.032

The Journal of Hand Surgery

Volume 40, Issue 8, August 2015, Pages 1692-1702

https://doi.org/10.1016/j.jhsa.2015.03.032 Get rights and content

Injury to the scapholunate interosseous ligament is one of the most common causes of carpal instability and can impart considerable compromise to the patient’s hand function. However, the management of scapholunate ligament injuries remains a dynamic concept, especially with regard to the multitude of options and techniques that exist for its surgical treatment. We present a thorough review of scapholunate anatomy and morphology, and the role of the scapholunate articulations in the kinetics and pathomechanics of wrist instability. We also review the current literature on the biomechanical properties of the scapholunate ligament and its subcomponents. A sound understanding of the anatomy and biomechanics of the scapholunate ligament can clarify its instability and may better orient current reconstructive procedures or pioneer better future techniques.

Section snippets

Anatomy and Morphology

The SLIL is a C-shaped ligament situated between the scaphoid and lunate bones of the wrist (Fig. 1). The SLIL is anatomically divided into 3 segments: dorsal, proximal, and volar, with the distal edge of the scapholunate articulation free of ligamentous attachment.⁵ The dorsal segment of the SLIL is the thickest and is situated between the proximal pole of the scaphoid and the dorsal portion of the lunate, with an approximate thickness of 3 mm and a proximal-distal length of 5 mm.⁶ The volar

Kinetics

During wrist flexion or radial deviation, the distal scaphoid flexes and draws the lunate into flexion through the strong SLIL (Fig. 4).2, 3 During wrist ulnar deviation, forces at the triquetral hamate articulation are transmitted through the SLIL, rotating the scaphoid and lunate into extension (Fig. 4).2, 16 The SLIL may also be critical for complex wrist movements such as the dart-throwing motion, which does not typically strain the SLIL but may depend on it for scapholunate stability

Pathomechanics

Injuries to the SLIL can manifest as static and dynamic instability. Scapholunate interosseous ligament injury can lead to static widening of the scapholunate interval, resulting in a distinct gap observable in the coronal plane on radiograph (Terry Thomas sign) (Fig. 5). However, sectioning of the SLIL alone may not necessarily produce a gap on radiograph.²¹ This is likely because of the presence of both primary and secondary stabilizers of the scapholunate joint.3, 22 It is possible that

Biomechanical Properties of SLIL

Table 1 lists previous investigations that assessed intact SLILs, including all 3 anatomical facets, to characterize their biomechanical properties. The most studied parameters to date have been linear stiffness and linear load to failure. Although some studies have agreeable parameters, there is variability among both linear stiffness (range, 34.10–1440 N/m) and linear load to failure (range, 115.4–2940 N). Some variability can be associated with differential methodologies. Although most

Biomechanical Properties of SLIL Subregions

Until recently, most studies have treated the SLIL as a single entity. However, there has been a movement to consider the mechanical properties of the 3 different subregions of the SLIL: dorsal, volar, and proximal.

Berger et al⁵³ used a biaxial servohydraulic system to test the extent of movement of the scaphoid relative to the lunate when different subregions of the SLIL were cut. Significant translation and rotation of the scaphoid mainly occurred when the dorsal SLIL was sectioned by itself