Scapholunate ligament injury

Complications

Main article: Wrist osteoarthritis

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

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.

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.

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

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

References

References

1. (10 July 2009). "Essential Orthopaedics". Elsevier Health Sciences.
2. (November 2023). "Scapholunate Instability: Diagnosis and Management - Anatomy, Kinematics, and Clinical Assessment - Part I.". The Journal of Hand Surgery.
3. (2014). "Scapholunate advanced collapse: a pictorial review". Insights into Imaging.
4. Shah, CM. (2013). "Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist arthritis". Curr Rev Musculoskelet Med.
5. Omori, S. (July 2013). "In vivo 3-dimensional analysis of dorsal intercalated segment instability deformity secondary to scapholunate dissociation: a preliminary report.". The Journal of Hand Surgery.
6. (2013). "Current Role of Open Reconstruction of the Scapholunate Ligament". Journal of Wrist Surgery.
7. (2001). "The anatomy of the ligaments of the wrist and distal radioulnar joints". Clinical Orthopaedics and Related Research.
8. Owen Kang and Henry Knipe. "Scapholunate advanced collapse".
9. Novelline, RA. (2004). "Squire's fundamentals of radiology, 6th Edition". President and fellows of Harvard college.