The scapholunate ligament is a

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

of the

wrist In human anatomy, the wrist is variously defined as (1) the Carpal bones, 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 ...

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

wrist osteoarthritis Wrist osteoarthritis is a group of mechanical abnormalities resulting in joint destruction, which can occur in the wrist. These abnormalities include degeneration of cartilage and hypertrophic bone changes, which can lead to pain, swelling and loss ...

called scapholunate advanced collapse (SLAC).

Anatomy

The scapholunate ligament is an

intraarticular A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

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 flake removed from a stone tool during the process of pressure flaking. In the Natufian period, a lunat ...

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 * Dorsal co ...

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

and palmar, with the dorsal segment being the strongest part. It is the main stabilizer of the scaphoid. In contrast to the scapholunate ligament, the lunotriquetral ligament is more prominent on the palmar side.

Instability

Complete

rupture Rupture may refer to: General * Rupture (engineering), a failure of tough ductile materials loaded in tension Anatomy and medicine * Abdominal hernia, formerly referred to as "a rupture" * Achilles tendon rupture * Rupture of membranes, a "wate ...

of this ligament leads to wrist instability. The main type of such instability is

dorsal intercalated segment instability Dorsal intercalated segment instability (DISI) is a deformity of the wrist where the lunate bone angulates to the dorsal side of the hand. Causes The main causes of DISI are: *Wrist trauma, with or without a fracture **Scaphoid fracture: bony DISI ...

(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, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

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 In radiology, the Terry-Thomas sign is a scapholunate ligament dissociation on an anteroposterior view of the wrist. Most commonly a result of a fall on the outstretched hand ( FOOSH), the scapholunate ligament ruptures resulting in separation of t ...

. 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

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