Scapholunate Dissociation

Definition/Description

Scapholunate dissociation is the most common and most significant ligamentous injury of the wrist.[1][2] Scapholunate instability is the most frequent pattern of carpal instability occurring separately and as part of other wrist disorders.[3] It results from the relative instability between the scaphoid and lunate bones secondary to the injury of scapholunate ligament and generally presents radiographically as a widened medial-lateral gap between the two carpal bones.[1]

Anatomy

The scapholunate ligament (SLL) also called scapholunate interosseous ligament (SLIL) is C-shaped and has three structurally distinct parts: volar, membranous and dorsal.The dorsal part of the SLL is the strongest and the primary stabiliser of the SL joint and can resist forces of up to 260 N. The avascular proximal membranous portion does not provide any significant laxity restraint (63 N), while the volar part of the SLL (118 N) plays an important role in terms of rotational stability. [3]
Volar wrist ligament.jpg
 

While the carpal bones in the distal row of the carpus distribute axial loads relatively evenly, 50% of an axial load through the wrist is transmitted through the radioscaphoid joint and 35% across the radiolunate joint. As the SLL is between these two primary load-sustaining bones, it is easy to understand how a destabilizing injury can occur here.  

The secondary stabilizers are: several extrinsic ligament such as scaphotrapeziotrapezoid, scaphocapitate, radioscaphocapitate and dorsal intercarpal ligaments.[4][2]

Isometric contraction of abductor pollicis longus, extensor carpi radialis longus (ECRL), and flexor carpi ulnaris induced midcarpal supination. Midcarpal supination tightens the volar scaphoid-distal row of the carpus, lending stability to the scaphoid. The flexor carpi radialis (FCR), in particular, rotates the scaphoid into flexion and supination when loaded, and pronates the capitate and triquetrum. Both of these actions contribute dynamic stability to the carpus. Proprioception and neuromuscular control also play a role in the stability of the scapholunate joint. [2]

The vascular supply to SLL is delicate and main vascular contribution comes from the radial artery.[3]

Epidemiology/Etiology

R Wrist.jpg
The primary mechanism of injury is an acute stress load of the wrist in extension and ulnar deviation, leading to a force vector pushing the lunate and scaphoid at an angle to each other instead of transferring force directly through the lunate and scaphoid together.[1]

The incidence of scapholunate interosseous ligament injury is unknown due to probable non-diagnosis of this injury in the setting of more distracting injuries resulting from falls on outstretched hands, such as distal radial fractures.[5]

Approximately 5% of all wrist sprains have an associated SL tear. About 13.4% of distal radius fractures are associated with scapholunate dissociation.particularly fractures of the radial styloid, the so-called Chauffeur’s fracture and also non-displaced scaphoid fractures are associated.[1][3][2]

Characteristics/Clinical Presentation

Patients with an SLL injury often present with

  • patient history have often an episode of clear injury preceding the symptoms include injuries to the wrist that involve a fall onto an extended, ulnarly deviated wrist (position that a hand assumes holding a steering wheel has also been postulated as a possible predisposition for an SLL injury during a motor vehicle accident)[2] or FOOSH injury (fall onto outstretched hand) or repetitive trauma while the wrist is in extension. Lau et al.[6] give an example of prolonged use of crutches as a type of overuse trauma to the wrist while it is in extension.
  • typically with tenderness over dorsoradial aspect of wrist
Snuffbox.jpg
  • pain in the anatomic snuffbox or the palmar scaphoid tuberosity.
  • a ‘click’or ‘pain’ on the dorso-radial aspect of the wrist
  • Swelling and limited grip strength and range of movement (ROM)[2][3]

Grading

Special Radiographic Views for Scapholunate Dissociation: Clenched Fist

Based on Radiological Findings

Watson et al described a spectrum of injury resulting from rotary subluxation of the scaphoid. Using static and dynamic radiographs, the injuries can be categorized into four groups: predynamic instability/occult, dynamic instability, static scapholunate dissociation, and SLAC.

Spectrum of scapholunate instability by radiograph[7]
In radiographs, a PA view is used to determine the size of the space between the scaphoid and the lunate. A gap greater than 3mm is considered to be pathologic, although there is research demonstrating that in normal wrists, the average is 3.7mm. For this reason, it is important to compare the size of the gap in the involved wrist to the patient’s uninvolved side. In addition to the PA view, the lateral view shows the scapholunate angle. The normal angle should be 30-60°, and if the angle is over 70°, it is considered a positive scapholunate dissociation.[8]
Radiolograph showing the gap between scaphoid and lunate.
For dynamic instability, SL dissociation is noted radiologically with SL angle > 60° and SL gap > 3 mm on clenched-fist or ulnar-deviation radiographs.[3]It often takes three to 12 months after trauma before dynamic instability develops and SL dissociation is noted radiologically. For this development and progression to occur, an additional tear or gradual, continuous elongation of the secondary ligament stabilisers of the SL ligament is needed.[3]

SLAC has its own spectrum based on the progression of arthritis. In the first stage, arthritic changes begin at the radial styloid. In the second stage, the arthritic changes progress to the radioscaphoid joint. In the third stage, arthritic changes are evident at the capitolunate joint. In the fourth stage there is evidence of arthritis throughout the radiocarpal and midcarpal joints.[2]

Based on Arthroscopic Findings

Geissler classified SLL injury as partial or total and the degree of instability as following:

Geissler's Arthroscopic Classification for intra-carpal ligament tear [9]

Complications

The two primary complications due to scapholunate dissociation are Scapholunate Advanced Collapse (SLAC) and general arthritis of the wrist.[10] Both of these lead to increased disability at the wrist, but a SLAC refers to a specific pattern of osteoarthritis and subluxation resulting secondary to an untreated disassociation that can lead to severe disability at the wrist.[3]

Examination

On palpation

Palpation of the wrist anatomic landmarks may elicit informative tenderness. There may be pain in the anatomic snuffbox or the palmar scaphoid.

Special Tests

  • Scapholunate Ballotment Test[11]
  • Watson's Test[10][12] It is also known as "scaphoid shift maneuver". Designed as a provocative test with dorsal subluxation of the proximal scaphoid over the dorsal rim of the radius as wrist is radially deviated. To perform the test the examiner:
  • Grasps the wrist with their thumb over the patient's scaphoid tuberosity with the wrist in slight dorsiflexion.
  • Move the patient's wrist from ulnar to radial deviation.
  • If the scapholunate ligament is disrupted, the scaphoid will tend to flex to the palm of the hand and the lunate will face dorsally on the hand.
Positive test: The examiner should feel a significant "clunk" and the pt will experience pain.
Watson's Test

Used with permission. November 2011.

Radiographs

  • AP view
  • Lateral view
  • Clenched fist view and ulnar deviation view (for dynamic wrist instability)[8]

Key characteristic to look :

  • Scapholunate gap
  • Scapholunate angle:When the scaphoid and lunate lose their normal relationship in an SLL injury, the scaphoid flexes and the lunate extends, resulting in a scapholunate (SL) angle >60° (Figure 4). This is called dorsal intercalated segment instability (DISI).
  • Terry Thomas sign
  • Gilula Lines
  • Scaphoid ring sign[2]

Differential Diagnosis

In determining a diagnosis, it is important to take a careful history, including specific details on how the patient fell onto their hand. Falling onto the hand with the wrist extended with ulnar deviation are the most likely positions to lead to damage to the SLIL. During the physical exam, palpation should also be done over the anatomic snuffbox. Tenderness tends to be at the proximal end of the snuffbox, and just distal to Lister’s tubercle. The examiner may also notice a click, or have the patient report the feeling of the wrist “giving way” when pressure is applied over the area. During the acute phase of injury, Scapholunate Dissociation can present similarly to a scaphoid fracture, so it is important that a possible fracture be ruled out. Other possible causes of wrist and hand pain are:

Site of Pain Possible Cause
Dorsal Wrist
  • Scaphoid impaction syndrome
  • Distal radioulnar joint instability
  • Scapholunate ligament tears
  • Lunotriquestral ligament tears
  • Occult ganglion
  • Carpometacarpal boss
  • Kienbock's disease
  • Posterior interosseous nerve
Ulnar Wrist Pain
  • Triangular fibrocartilage complex tears
  • Ulnar impaction syndrome
  • Flexor carpi ulnaris tendinitis
  • Extensor carpi ulnaris tendinitis
  • Extensor carpi tendon subluxation
Radial Wrist Pain
  • De Quervain's tenosynovitis
  • Flexor carpi radialis tendinitis
  • Intersection syndrome
  • Scaphoid fracture
  • Cheiralgia paresthetica
Volar Wrist Pain
  • Ganglion
  • Carpal instability
  • Kienbock's disease
  • Preiser's disease (avascular necrosis of the scaphoid)
  • Flexor carpi radialis tendinitis
  • Pisotriquetral arthritis
Palmar Pain
  • Ulnar neuritis
  • Carpal tunnel syndrome
  • Hook of hamate fracture
  • Guyon's canal compression

[13]

Outcome Measures

Medical Management

The medical management of scapholunate dissociation includes many surgical options, but unfortunately no single procedure has distinguished itself as the best way to manage this injury. Even among surgeons there is no preferred method or current best evidence available. Studies that have attempted to perform a meta-analyses of treatments have found that research articles vary in describing the technical aspects of an operation to reporting the results of using a single method. Evidence based assessments have been attempted, but again, due to the nature of differing methodologies and comparisons of previous reports, no method has been shown as superior. [6][8]

While it is difficult for the medical community to decide on specific surgical interventions, other categorical separations do indicate certain procedures over others. These include the acuity or chronicity of the injury, the severity of the separation and to what extent the impairments are affecting the individual.

If the injury is acute, the current methods of choice are:

  • Closed reduction and cast immobilisation (8-weeks)
  • Closed or open reduction and percutaneous Kershner wire (K-wire) fixation
  • Open reduction with direct repair of the scapholunate ligament
  • Open reduction and replacement of the scapholunate ligament with tendon graft [6][14]

More often, this type of injury is discovered in the chronic stage as it can present much like a wrist sprain or soft tissue inflammation. Many times, the individual will not even seek care until 15-25 years post injury.[8] With chronic dissociations that present without arthritis, the surgical options are:

  • Blatt capsulodesis
  • Scaphoid tenodesis
  • Tendon reconstruction of the scapholunate ligament
  • Scaphoid Trapezium Trapezoid fusion

Other options include (but are much less widely used):

  • Arthroscopic joint debridement
  • Autogenous bone-retinaculum-bone ligament reconstruction
  • Scapholunate or scaphocapitate fusion

If the injury is chronic and has advanced to include arthritic changes (SLAC) options include:

  • Proximal carpal row carpectomy
  • Scaphoid exision and four-corner fusion of lunate, triquetrum, capitate and hamate
  • Wrist fusion[6][15][8]


Soft tissue reconstructions in theory can more accurately restore the normal biomechanics of the wrist. However, the tendons that are used as replacements hold less viscoelasticity than the original ligaments. Skeletal procedures are more predictable, but also more permanent (fusions). Both types of operations have strengths and weaknesses. Garcia-Elias et al. created an algorithm of treatment based off a number of predicating factors of the injury which has been shown to be helpful in deciding which procedure to use. [14]

On a positive note, it has been shown in the literature that surgical management does tend to improve patients’ symptoms. While not always restoring pre-injury function, patients do report better subjective pain ratings and functional outcomes following surgery compared to non-operative treatment.[15] While there are many surgical options, there is no gold standard procedure. Current recommendations suggest that relying on your surgeon’s experience and expertise in a particular method will grant better results that using a standard procedure. [8]

Abbreviations: ECRL, extensor carpi radialis longus; SL, scapholunate; SLL, scapholunate ligament.
Treatment of scapholunate dissociation by stage. Garcia-Elias et al

Physical Therapy Management[16][3]

Unfortunately, rehabilitation of SLD has not yet been well researched. As such an impairment based approach is recommended in the acute and chronic phases. It is advised to work closely with the orthopaedic surgeon for post-surgical patients and patients with symptoms that may benefit from surgery. Also it has its role, especially in partial SLL injuries and pre-dynamic and dynamic instabilities.[3]

Acute Phase

After ruling out more serious conditions, this condition can be treated as essentially synonymous with an ankle sprain of similar severity.

Chronic Phase

Impairments such as limitations in ROM, poor grip strength as compared bilaterally, and severe pain should be addressed as appropriate. It is recommended that the patient should learn to recognise activities which over stress their wrist and avoid or modify these activities. The use of heating or cooling modalities, including contrast baths, and NSAIDS may be used for symptom control during flare-ups.[17] In addition, splints may be used to limit the movement of the involved joints.[17] Cadaver studies have also indicated that the Flexor Carpi Radialis may play a role in stabilising the Scaphoid during movement.[18]

Post-Surgically

Physiotherapy management should be based on the surgeon's protocol. The patient will likely wear a cast for up to 10 weeks,[19] which can result in a number of significant limitations, which can then be addressed in therapy. It has been suggested by Goldberg et al that rehabilitation following a major reconstruction surgery can take 4-6 months until return to activity and 12-15 months until full recovery.[19] Even with a successful surgery, it is suggested that the patient could benefit from wearing a removable Orthosis during particularly strenuous activities[19]

Effective Exercises

  • A combination of proprioceptive, neuromuscular training and physiotherapeutic treatment regimens appears to yield the greatest improvement in the sensorimotoric control and stability of joints.[3][16]
  • Re-education of the flexor carpi radialis (FCR) has also shown beneficial for stability of Scaholunate joint.[3]
  • Resisted wrist flexion/extension with a handheld weight. Can also be performed into ulnar/radial deviation or it can be used to stretch the patient into these positions
  • Passive self stretch with elbow extended into flexion/extension
  • Self resisted isometric strengthening of the wrist extensors/flexors
  • Prayer stretch with palms together and fingers extended
  • Wrist extension self mobilization in a prayer position
  • Concentric/eccentric wrist flexors/extensors resisted by theraband
  • Hold a hammer or cane at the end of the handle and move slowly through pronation/supination. As the patient tolerates, move further down the handle to increase the resistance or vice-versa
  • Grip strengthening using a hand dynamometer (this can be dosed as a percentage of patients contralateral side or 1 rep max).

Clinical Bottom Line

SLD is a very common complication of FOOSH type injuries and is equally commonly undiscovered. There are several secondary complications such as SLAC or arthritis which may not appear until many years after the initial insult. The most well researched treatment option for SLD is surgical repair, but a commonly agreed upon surgical approach has not yet been identified. PT management of the condition should be considered impairment based according to the specific stage and severity of the patient presentation.

References

  1. 1.0 1.1 1.2 1.3 Duke Orthopaedics: Wheeless' Textbook of Orthopaedics. http://www.wheelessonline.com/ortho/scapholunate_instability (accessed 15 October 2011).
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Konopka G, Chim H. Optimal management of scapholunate ligament injuries. Orthopedic research and reviews. 2018;10:41.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Andersson JK. Treatment of scapholunate ligament injury: current concepts. EFORT open reviews. 2017 Sep;2(9):382-93.
  4. Van Overstraeten L, Camus EJ, Wahegaonkar A, Messina J, Tandara AA, Binder AC, Mathoulin CL. Anatomical description of the dorsal capsulo-scapholunate septum (DCSS)—arthroscopic staging of scapholunate instability after DCSS sectioning. Journal of wrist surgery. 2013 May;2(02):149-54.
  5. Tomas A. Scapholunate Dissociation. Journal of Orthopaedic & Sports Physical Therapy. 2018 Mar;48(3):225-.
  6. 6.0 6.1 6.2 6.3 Lau S, Swarna SS, Tamvakopoulos GS. Scapholunate dissociation: an overview of the clinical entity and current treatment options. European Journal of Orthopaedic Surgery & Traumatology. 2009 Aug 1;19(6):377-85.
  7. Konopka G, Chim H. Optimal management of scapholunate ligament injuries. Orthopedic research and reviews. 2018;10:41.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 Bloom HT, Freeland AE, Bowen V, Mrkonjic L. The Treatment of Chronic Scapholunate Dissociation: An Evidence-Based Assessment of the Literature. Orthopedics. 2003;26(2):195-203
  9. Andersson JK. Treatment of scapholunate ligament injury: current concepts. EFORT open reviews. 2017 Sep;2(9):382-93.
  10. 10.0 10.1 Duke Orthopaedics: Wheeless' Textbook of Orthopaedics. http://www.wheelessonline.com/ortho/scapholunate_advanced_collapse_slac. (Accesed 15 October 2011).
  11. Opreanu RC, Baulch M, Katranji A. Reduction and maintenance of scapholunate dissociation using the TwinFix screw. Eplasty. 2009;9.
  12. Watson's Test. http://en.wikipedia.org/wiki/Watson%27s_test. (accessed 24 October 2011).
  13. Jacobson MD, Plancher KD. Evaluation of hand and wrist injuriesin athletes. Operative Techniques in Sports Medicine. 1996 Oct 1;4(4):210-26.
  14. 14.0 14.1 Garcia-Elias M, Lluch AL, Stanley JK. Three-ligament tenodesis for the treatment of scapholunate dissociation: indications and surgical technique. The Journal of hand surgery. 2006 Jan 1;31(1):125-34.
  15. 15.0 15.1 Caloia M, Caloia H, Pereira E. Arthroscopic scapholunate joint reduction. Is an effective treatment for irreparable scapholunate ligament tears?. Clinical Orthopaedics and Related Research®. 2012 Apr 1;470(4):972-8.
  16. 16.0 16.1 Wolff AL, Wolfe SW. Rehabilitation for scapholunate injury: application of scientific and clinical evidence to practice. Journal of Hand Therapy. 2016 Apr 1;29(2):146-53.
  17. 17.0 17.1 Capele A, et al. Mayo Clinic Health Letter - Tools for Healthier Lives. 2011;29(1):1-3. Mayo Foundation for Medical Education and Research, 200 first St. SW, Rochester, MN 55905.http://www.businesswire.com/news/home/20110117005129/en/Mayo-Clinic-Health-Letter-January-2011-Reducing Accessed: November 27th, 2011.
  18. Salvà-Coll G, Garcia-Elias M, Llusá-Pérez M, Rodríguez-Baeza A. The role of the flexor carpi radialis muscle in scapholunate instability. The Journal of hand surgery. 2011 Jan 1;36(1):31-6.
  19. 19.0 19.1 19.2 Goldberg SH, Strauch RE, Rosenwasser MP. Scapholunate and lunotriquetral instability in the athlete: Diagnosis and management. Operative Techniques in Sports Medicine. 2006 Apr 1;14(2):108-21