The scapholunate ligament is a

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

of the

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

. Rupture of the scapholunate ligament causes scapholunate instability, which, if untreated, will eventually cause a predictable pattern of

wrist osteoarthritis Wrist osteoarthritis is gradual loss of articular cartilage and hypertrophic bone changes (osteophytes). While in many joints this is part of normal aging (senescence), in the wrist osteoarthritis usually occurs over years to decades after scapholu ...

called scapholunate advanced collapse (SLAC).

Anatomy

The scapholunate ligament is an intraarticular ligament binding the

scaphoid The scaphoid bone is one of the carpal bones of the wrist. It is situated between the hand and forearm on the thumb side of the wrist (also called the lateral or radial side). It forms the radial border of the carpal tunnel. The scaphoid bone ...

and

lunate Lunate is a crescent or moon-shaped microlith. In the specialized terminology of lithic reduction, a lunate flake is a small, crescent-shaped lithic flake, flake removed from a stone tool during the process of pressure flaking. In the Natufian cu ...

bones of the wrist together. It is divided into three areas,

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

proximal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and palmar, with the dorsal segment being the strongest part. It is the main

stabilizer Stabilizer, stabiliser, stabilisation or stabilization may refer to: Chemistry and food processing * Stabilizer (chemistry), a substance added to prevent unwanted change in state of another substance ** Polymer stabilizers are stabilizers used ...

of the scaphoid. In contrast to the scapholunate ligament, the lunotriquetral ligament is more prominent on the palmar side.

Instability

Complete rupture of this ligament leads to wrist instability. The main type of such instability is dorsal intercalated segment instability (DISI) deformity, where the lunate angulates to the posterior side of the hand. A ''dynamic scapholunate instability'' is where the scapholunate ligament is completely ruptured, but secondary scaphoid stabilizers are still preserved; these are the scaphotrapezial (ST), scaphocapitate (SC) and radioscaphocapitate (RSC) ligaments. In a ''static scapholunate instability'', these other ligaments are ruptured as well.

Diagnosis

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

images indicate scapholunate ligament instability when the scapholunate distance is more than 3 mm, which is called ''scapholunate dissociation''. A static scapholunate instability is generally readily visible, but a dynamic scapholunate instability can only be seen radiographically in certain wrist positions or under certain loading conditions, such as when clenching the wrist, or loading the wrist in ulnar deviation. In order to diagnose a SLAC wrist you need a posterior anterior (PA) view X-ray, a lateral view X-ray and a fist view X-ray. The fist X-ray is often made if there is no convincing Terry Thomas sign. A fist X-ray of a scapholunate ligament rupture will show a descending capitate bone. Making a fist will give pressure at the capitate, which will descend if there is a rupture in the scapholunate ligament. The

Watson's test Watson's test, also known as the scaphoid shift test, is a diagnostic test for instability between the scaphoid and lunate bones of the wrist. Test procedure To perform the test, the examiner grasps the wrist with their thumb over the scaphoid tu ...

may be used in diagnosis. File:ScaphoLuncateDisoMark.png, ''Static'' scapholunate dissociation File:X-ray of dynamic scapholunate instability - annotated.jpg, Dynamic instability: Increased scapholunate distance (between yellow lines) upon ulnar deviation of the wrist, but not otherwise. File:Dynamic_S-L-grip.jpg, Dynamic scapholunate instability visible upon clenching the wrist File:Scapholunatedis.png, Scapholunate ligament disruption associated with a

Colles' fracture A Colles' fracture is a type of fracture of the distal forearm in which the broken end of the radius is bent backwards. Symptoms may include pain, swelling, deformity, and bruising. Complications may include damage to the median nerve. It ty ...

Treatment

Treatment will vary depending upon the degree of injury and can range from observation and direct ligament repair through to reconstruction.

Complications

Eventually, untreated scapholunate instability generally causes a predictable pattern of

called scapholunate advanced collapse (SLAC).

References

{{Use dmy dates, date=April 2017 Ligaments of the upper limb