Scapholunate ligament injury

Scapholunate ligament injury
Other names: Scapholunate instability; scapholunate interosseous ligament (SLIL) injury
Xray showing a scapholunate dissociation resulting from an injury
Specialty	Plastic surgery
Symptoms	Wrist pain and weakness
Complications	Scapholunate advanced collapse (SLAC)
Types	Partial (occult), complete (dynamic, static)
Causes	Fall on the hand, sprained wrist, repetitive motion
Diagnostic method	Based on symptoms, supported by X-rays, MRI, or arthroscopy
Differential diagnosis	de Quervain tenosynovitis, carpal tunnel syndrome, ganglion cyst, gout, tendonitis
Treatment	Splinting, physiotherapy, surgery
Medication	NSAIDs
Frequency	Relatively common

Scapholunate ligament injury is a disruption of the ligament connecting the scaphoid and lunate bones within the wrist. Symptoms may include wrist pain and weakness, particularly when the wrist is bent back. There may also be a clicking sound with certain movements. If untreated, complications include a form of wrist osteoarthritis called scapholunate advanced collapse (SLAC).

It may result from falling on the hand, sprain of the wrist, repetitive motion, or gout. Diagnosis is based on symptoms, supported by X-rays, MRI, or arthroscopy. Injury may be partial (occult) or complete (dynamic or static). X-rays in partial injuries often appear normal, while complete injuries may show widening when the fist is clenched or at rest.

Management is with splinting for around 5 weeks if X-rays are normal. Repeat X-rays should than be performed and if symptoms have resolved physiotherapy may begin. If X-rays show widening follow up with hand surgery is recommended within about 10 days for potentially surgical options. Pain can be managed with NSAIDs.

Scapholunate ligament injury is relatively common. It is present in about 5% of wrist sprains and 40% of distal radius fractures. Those at greater risk include young athletes. The condition was first described in 1926 by Destot.

Complications

Eventually, untreated scapholunate instability generally causes a predictable pattern of wrist osteoarthritis called scapholunate advanced collapse (SLAC).

Pathophysiology

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.

Anatomy

Scapholunate ligament
Shown is the right hand, palm down (left) and palm up (right). A=Scaphoid, B=Lunate
From	Scaphoid
To	Lunate
Identifiers
TA98
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	{{#property:P1402}}
Anatomical terminology

The scapholunate ligament is an intraarticular ligament binding the scaphoid and lunate bones of the wrist together. It is divided into three areas, dorsal, proximal 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.

Diagnosis

X-ray 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.

The most accurate test for diagnosis is arthroscopy.

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 may be used in diagnosis.

• 
  Dynamic instability: Increased scapholunate distance (between yellow lines) upon ulnar deviation of the wrist, but not otherwise.
• 
  Dynamic scapholunate instability visible upon clenching the wrist
• 
  Scapholunate ligament disruption associated with a Colles' fracture

Treatment

Treatments vary depending upon the degree of injury and can range from observation to direct ligament repair or reconstruction.