Scapholunate Ligament (SL) Tears

Neil J. White, M.D., FRCSC
Orthopaedic Hand & Trauma Surgeon 
University of Calgary
Calgary, AB

In 1972, Linscheid and colleagues observed a pattern of wrist injury implicating a starting point for the simple 'wrist sprain.' It was theorized that an unrecognized injury to the Scapholunate (SL) ligament could lead to a predictable collapse deformity and, ultimately, severe arthritis of the wrist. They postulated that early recognition and treatment of this injury could prevent long-term morbidity1. Some 40 years later SL ligament dissociation is far better understood, but we still struggle when it comes to early identification.

 

As reviewed earlier, an SL ligament tear results in scaphoid flexion and lunate extension. When the angle between these bones is greater than 60º a DISI deformity exists (Figure 1). On the AP view we see a gap of greater than 3 mm. The scaphoid had flexed and pronated away from the lunate. This causes abnormal joint loading on the oval scaphoid facet of the radius, which leads to chronic arthritic changes. The lunate facet however, is preserved resulting from its circular articulation allowing for equal loading despite pathologic extension. This lunate facet preservation becomes very important when we think about treating the chronic sequelae, scapholunate advanced collapse (SLAC wrist).

The hallmarks of identification of an acute SL ligament injury include a high index of suspicion, and early imaging. The common presentation of a painful swollen wrist with diffuse palpable tenderness is nonspecific. Careful exam may reveal a point of maximal tenderness 1-2 cm distal to Lister's tubercle. The examiner can use his or her thumb to track distally from this readily identifiable landmark allowing the thumb to fall over the dorsal lip of the distal radius onto the SL ligament. The patient with an acute injury is often too sore to glean information from a Watson shift test.

High quality X-rays must be obtained in the PA and lateral planes (Figure 1). X-rays of the contra-lateral side are recommended routinely for comparison. Index of suspicion should go up in the setting of an isolated radial styloid fracture (Figure 1). The diagnosis can be confirmed by arthrography, MRI, MRI arthrography, or wrist arthroscopy.

white1
Figure 1: A 57 year-old labourer with radial styloid fracture. Terry Thomas Sign (top left). This implies a force that started at the radial styloid (bottom left) and propagated through the SL ligament (A to B). Lateral view shows DISI deformity (87º).

After identifying this injury, the next challenge is deciding if the pathology is truly acute. Repairing a chronic SL ligament tear is unlikely to yield a good outcome; generally reconstruction or repair with augmentation is required. This is especially true in the manual labourer3. It is paramount to ensure the patient's symptoms are not a result of previous wrist injuries including trivial sprains. Likewise it is important to know if the patient had any pre-injury pain or loss of function. X-rays and any advanced imaging must be scrutinized for any evidence of arthritic changes suggesting a chronic injury with acute aggravation. Finally arthroscopy can also be used to assess for haematoma, other evidence of an acute injury and for evidence of SLAC wrist arthritis.

Unfortunately, unlike the neighboring pathology of scaphoid fracture, immobilization and re-examination is not an option. The window for repair of this relatively avascular ligament is considered small. Acute injuries have been arbitrarily defined as two to four weeks2,4.

Surgical repair is generally performed with a dorsal approach to the carpus. The deformity is reduced using diverging vertical K-wires as joysticks (Figure 2) and the ligament is repaired with suture anchors. Dorsal capsulodesis can be used to augment the repair. K-wires or headless screw fixation are used to temporarily neutralize the repair while the ligament heals.

white2
Figure 2: Divergent K-wire joysticks are used to control the scaphoid and the lunate (A, B). The scaphoid is then extended and the lunate flexed (bringing the wires together) to reduce the deformity. This can be provisionally held with a Kocher clamp (C) and then fixed with either K-wires or a headless smooth shaft compression screw.

Although many studies suggest favorable outcome of SL ligament repair in the setting of acute ligament rupture5,6,7, it should be noted that this technique has never been studied prospectively or in any comparative fashion.

In summary, this is a difficult injury to identify and often difficult to discern whether acute or chronic. Careful history and physical exam coupled with liberal use of X-rays and judicious use of advanced imaging are the keys to making an accurate diagnosis. In general, a truly acute injury should be repaired acutely.

References

  1. Linscheid R.L., Dobyns J.H., Beabout J.W., et al. Traumatic instability of the wrist. Diagnosis, classification, and pathomechanics. J Bone Joint Surg Am 1972;54(8):1612-32.
  2. Manuel J., Moran S.L. The Diagnosis and Treatment of Scapholunate Instability. Orthop Clin N Am 38 (2007) 261-277.
  3. Pomerance J. Outcome After Repair of the Scapholunate Interosseous Ligament and Dorsal Capsulodesis for Dynamic Scapholunate Instability Due to Trauma. J Hand Surg Am 2006; 31A(8):1380-1386.
  4. Kuo C.E., Wolfe S.W. Scapholunate Instability: Current Concepts in Diagnosis and Management J Hand Surg 2008;33A:998-1013
  5. Bickert B., Sauerbier M., Germann G. Scapholunate ligament repair using the Mitek bone anchor. J Hand Surg 2000. 25B:188-192.
  6. Pilny J., Kubes J., Cizmar I., Visna P. Our experience with repair of the scapholunate ligament using the MITEK bone anchor. Acta Chir Orthop Traumatol Cech 2005;72:381-386.
  7. Minami A., Kato H., Iwasaki N. Treatment of scapholunate dissociation: ligamentous repair associated with modified dorsal capsulodesis. Hand Surg 2003;8:1-6.

Submit Community Content

If you have orthopedic information that you would like to share with the Orthogate Community, please register/login and submit your news, event, job, article, case or workshop from the Submit Content menu under the My Account area. Learn more!