Scapholunate separation is the most common and important wrist ligament injury.  Scapholunate instability is the most common pattern of carpal instability, occurring alone and as part of other wrist disorders.  This is due to the relative instability between Scaphoid and lunate secondary to scapholunate ligament injury usually manifests radiographically as widening of the internal and external space between the two carpal bones. 
The scapholunate ligament (SLL), also known as the scapholunate interosseous ligament (SLIL), is C-shaped with three structurally distinct parts: volar membranous and dorsal. The dorsal portion of the SLL is strongest and is the main stabilizer of the SL joint, resisting forces up to 260 N. The avascular proximal membrane portion does not provide any appreciable slack constraint (63 N), whereas the volar portion of the SLL (118 N) plays an important role in rotational stability. 
Although the distal row of carpal bones distributes the axial load relatively evenly, 50% of the axial load at the wrist is transmitted through the radioscaphoid joint and 35% through the radiolunate joint. Since the SLL is located between these two major weight-bearing bones, it is easy to Learn how destabilizing damage happens here.
The secondary stabilizers are: several extrinsic ligaments such as the trapezoidal navicular bone and the dorsal intercarpal ligament.  
Isometric contractions of the abductor pollicis longus, extensor carpi radialis longus (ECRL), and flexor carpi ulnaris cause supination of the carpus. Supination of the middle carpus tightens the distal row of volar navicular bones of the carpus, stabilizing the navicular. Specifically the flexor carpi radialis (FCR) Rotates the scaphoid into flexion and supination under load and pronates the capitate and triquetrum. Both of these actions contribute to the dynamic stability of the wrist. Proprioception and neuromuscular control also play a role in the stability of the scapholunate joint. 
The vascular supply of SLL is fragile, with the major vascular contribution coming from the radial artery. 
Scapholunate injuries are common after wrist trauma.  The primary mechanism of injury is that acute stress loading of the wrist in extension and ulnar deviation causes the force vector to push the lunate and scaphoid against each other at an angle, rather than transmitting force directly through the lunate with the navicular. 
The incidence of scapholunate interosseous ligament injuries is unknown, as this injury may not be diagnosed in cases where a fall with an outstretched hand (eg, distal radius fracture) results in a more distracting injury. 
Approximately 5% of wrist sprains are associated with SL tears. Approximately 13.4% of distal radius fractures are associated with scapholunate separation. In particular radial styloid fractures, the so-called Chauffeur fractures and undisplaced scaphoid fractures are associated. 
Patients with SLL injuries often present with
- Patient’s medical history usually precedes symptoms with significant injury events, including wrist injury involving a fall onto an extended ulnarly deviated wrist (hands-on-steering-wheel posture has also been identified as a possible trigger for SLL injury) motor vehicle accident) or FOOSH injury (fall into outstretched hand) or repetitive trauma in wrist extension. Liu et al.  gave an example of chronic use of crutches as a type of overuse trauma with wrist extension.
- Tenderness, usually on the back of the wrist
- Anatomical snuffbox or palmar scaphoid tubercle pain.
- A “click” or “pain” on the dorsal radial side of the wrist
- Swelling and limited grip strength and range of motion (ROM)
Based on Radiological Findings
Watson et al described a series of injuries resulting from rotational subluxation of the scaphoid. Using static and dynamic radiographs, injuries can be divided into four groups: predynamic instability/occult dynamic instability static scapholunate separation and SLAC.
X-ray film showing scapholunate instability spectrum
On radiographs, the PA view is used to determine the size of the space between the scaphoid and lunate. A gap greater than 3 mm is considered pathological, although studies have shown that the average gap in normal wrists is 3.7 mm. For this reason, it is important to compare the size of The gap between the affected wrist and the patient’s healthy side. In addition to the PA view, the lateral view shows the scapholunate angle. The normal angle should be 30-60°, if the angle exceeds 70°, it is considered positive separation of the scapholunate. 
For dynamic instability, SL separation is noted radiologically with SL angle > 60° and SL gap > 3 mm on clenched fist or ulnar deviation radiographs.  It usually takes 3 to 12 months after trauma to develop dynamic instability and SL dissociation to be radiographically noted. for this Development and progression require additional tears or gradual continuous elongation of the secondary ligament stabilizers of the SL ligament. 
SLAC has its own spectrum according to the progression of arthritis. In the first stage, arthritic changes begin at the radial styloid process. In the second stage, arthritic changes progress to the radioscaphoid joint. In the third stage, arthritic changes are evident at the craniolunate joints. in the fourth Stage Evidence of arthritis throughout the radiocarpal and middle carpal joints. 
Based on Arthroscopic Findings
Geissler classifies SLL injuries as partial or total, with degrees of instability as follows:
Geissler’s arthroscopic classification of medial carpal ligament tears 
The two main complications resulting from scapholunate separation are late scapholunate collapse (SLAC) and general arthritis of the wrist.  Both lead to increased wrist disability, but SLAC refers to a specific pattern of osteoarthritis and subluxation secondary to the wrist An untreated separation can lead to severe disability of the wrist. 
Palpation of the anatomical landmarks of the wrist may cause informative tenderness. There may be pain dissecting the snuffbox or navicular bone in the palm.
- Scapholunate Ballottement Test
- Watson’s Test It is also called navicular displacement maneuver. Designed as a provocative test, dorsal subluxation of the proximal scaphoid at the dorsal edge of the radius when the wrist is radially deviated. The examiner performs the test:
- Grab the patient’s wrist above the navicular tubercle with the thumb, with the wrist slightly dorsiflexed.
- Move the patient’s wrist from the ulnar side to the radial side.
- If the scapholunate ligament is damaged, the scaphoid will tend to bend into the palm, while the lunate will face the back of the hand.
Positive Test: Examiner should feel a distinct clunk and patient feel pain.
Watson tests used with permission. November 2011.
Plain radiographs are a viable method of assessing scapholunate injury. 
- AP view
- Lateral view
- Clenched fist view and ulnar view (dynamic wrist instability) 
Key characteristic to look :
- Scapholunate gap
- Scapholunate Angle: When the scaphoid and lunate lose their normal relationship in SLL injuries, the scaphoid flexes and the lunate extends, resulting in a scapholunate (SL) angle >60° (Figure 4). This is called dorsal intervening segmental instability (DISI).
- Terry Thomas sign
- Gilula Lines
- Scaphoid ring sign
When establishing a diagnosis, it is important to take a careful medical history, including specific details about how the patient fell on their hands. A fall with the wrist extended and with ulnar deviation is the posture most likely to result in SLIL damage. Palpation during physical examination Should also be performed on an anatomical snuffbox. Tender points tend to be proximal to the snuffbox and distal to Lister’s nodules. The examiner may also notice a click or have the patient report a feeling of the wrist “releasing” when pressure is applied to the wrist area. In the acute phase of injury, scapholunate separation may resemble a scaphoid fracture, so it is important to rule out possible fractures. Other possible causes of wrist and hand pain are:
Possible Causes of Pain Location Dorsal Carpal Scaphoid Impingement Syndrome Distal Radioulnar Joint Instability Scapholunate Ligament Tears Lunate Trigonal Ligament Tears Occult Ganglion Carpal Metacarpal Metacarpal Boss Kienbock Disease Tear ulnar impingement syndrome Flexor carpi ulnaris tendonitis Extensor carpi ulnaris tendon subluxation Carpi radialis pain De Quervain’s tenosynovitis Flexor carpi radialis tendinitis Intersection syndrome Scaphoid fracture Wrist pain Wrist pain carpal ganglion Instability Kimberk’s diseasePresser’s disease (Avascular necrosis of the scaphoid) Flexor carpi radialis tendinitis Bovine triangle arthritis Palm pain Ulnar neuritis Carpal tunnel syndrome Hamate hook fracture Gayon’s canal compression
- DASH (Disability of the Arm, Shoulder and Hand)
- PRWE (Patient Wrist Evaluation)
Medical treatment of scapholunate separation includes many surgical options, but unfortunately, no single procedure stands out as the best approach to treat this injury. Even among surgeons, there is no preferred method or the best evidence currently available. research attempted A meta-analysis of treatments found that research articles varied from describing the technical aspects of the procedure to reporting results using a single method. Evidence-based assessments have been attempted, but again due to different methods and the nature of the comparisons In previous reports, none of the methods proved superior. 
While it is difficult for the medical community to decide on specific surgical interventions, other classification separations do suggest that certain procedures are superior to others. These include the severity or long-term nature of the injury, the severity of the separation, and the extent of the effects of the injury personal.
If the injury is acute, the current approach of choice is:
- Closed reduction and plaster immobilization (8 weeks)
- Closed or open reduction and percutaneous Kirschner wire (Kirschner wire) fixation
- Open reduction for direct repair of scapholunate ligament
- Open reduction of the scapholunate ligament with tendon graft  
This type of injury is more common in the chronic phase because it can manifest much like a wrist sprain or soft tissue inflammation. Many times, individuals do not even seek treatment until 15-25 years after the injury.  For chronic dissection without arthritis, surgical options yes:
- Blatt capsulodesis
- Scaphoid tenodesis
- Tendon reconstruction of the scapholunate ligament
- Scaphoid Trapezium Trapezoid fusion
Other options include (but are less widely used):
- Arthroscopic joint debridement
- Autologous bone-retina-osseous ligament reconstruction
- Scapholunate or scaphocapitate fusion
If the injury is chronic and has progressed to include arthritic changes (SLAC) options include:
- Proximal carpal row carpectomy
- Resection of lunate triangular bone and hamate scaphoid and fusion of four corners
- Wrist fusion
In theory soft tissue reconstruction can more accurately restore normal biomechanics of the wrist. However, the viscoelasticity of the tendon used as a substitute was lower than that of the original ligament. Bone surgery is more predictable, but also more permanent (fusion). two types Operation has advantages and disadvantages. García-Elias et al. A treatment algorithm was created based on some predictors of injury, which has been shown to help decide which procedure to use. 
On the positive side, the literature shows that surgical treatment does improve patients’ symptoms. While pre-injury function is not always restored, patients do report better subjective pain scores and functional outcomes after surgery compared to non-surgery Treatment  Although 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 approach will yield better results than using standard procedures. 
Staged treatment of scapholunate separation. García-Elias et al.
Physical Therapy Management
Unfortunately, rehabilitation from SLD has not been well studied. Therefore, an injury-based approach is recommended in both acute and chronic phases. Close collaboration with a plastic surgeon is recommended for postoperative patients and those with symptoms that are likely to benefit from surgery. It also has its role, especially in partial SLL injuries and anterior and dynamic instability. 
After excluding more serious conditions, this condition can essentially be considered synonymous with an ankle sprain of similar severity.
Injuries such as localized poor grip strength and severe pain in ROM compared to bilateral should be managed as appropriate. Advise patients that they should learn to recognize activities that place excessive stress on the wrist and avoid or modify these activities. use heat or Cooling modalities, including contrast baths and NSAIDs, can be used to control symptoms during attacks.  In addition, splints can be used to limit the motion of the joint involved.  Cadaveric studies also suggest that the flexor carpi radialis may be stabilizing Scaphoid during motion. 
Physical therapy management should be based on the surgeon’s protocol. Patients may wear a plaster cast for up to 10 weeks , which can result in a number of significant limitations that can then be addressed in therapy. Goldberg et al suggested that after recovery Major reconstructive surgery may take 4-6 months for return to activity and 12-15 months for full recovery.  Even if the procedure is successful, patients may benefit from being advised to wear removable orthotics when performing particularly strenuous activities .
- A combination of proprioceptive neuromuscular training and a physiotherapy treatment program appears to produce the greatest improvements in sensorimotor control and joint stability.  
- Retraining of the flexor carpi radialis (FCR) has also been shown to benefit the stability of the scapholunate joint. 
- Resist wrist flexion/extension with a hand weight. Ulnar/radial deviations can also be performed, or the patient can be stretched into these positions
- Passive self-extension with elbow extended into flexion/extension
- Self-resistance isometric strengthening of wrist extensors/flexors
- folded hands in prayer stretch, fingers stretched
- Wrist Stretch Self-Mobilization in Prayer Position
- concentric/eccentric wrist flexors/extensors of theraband resistance
- Hold the hammer or cane at the end of the handle and move slowly through pronation/supination. As tolerated by the patient, move the handle further down to increase resistance and vice versa
- Strengthen the grip using a hand dynamometer (this can be done as a percentage of the patient’s contralateral side or up to 1 repetition).
Clinical Bottom Line
SLD is a very common complication of FOOSH-type injuries and is also often unrecognized. There are several secondary complications, such as SLAC or arthritis, which may not appear until many years after the initial injury. The most well-studied treatment option for SLD is surgical repair, but A commonly agreed surgical approach has not been identified. Depending on the specific stage and severity of the patient’s presentation, PT management of the condition should be considered.
- ↑ Jump up to: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).
- ↑ Jump up to: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.
- ↑ Jump up to: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.
- ↑ 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.
- ↑ Goelz L, Kim S, Güthoff C, Eichenauer F, Eisenschenk A, Mutze S, Asmus A. ACTION trial: a prospective study on diagnostic Accuracy of 4D CT for diagnosing Instable ScaphOlunate DissociatioN. BMC Musculoskelet Disord. 2021 Jan 15;22(1):84.
- ↑ Tomas A. Scapholunate Dissociation. Journal of Orthopaedic & Sports Physical Therapy. 2018 Mar;48(3):225-.
- ↑ Jump up to:7.0 7.1 7.2 7.3 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.
- ↑ Konopka G, Chim H. Optimal management of scapholunate ligament injuries. Orthopedic research and reviews. 2018;10:41.
- ↑ Jump up to:9.0 9.1 9.2 9.3 9.4 9.5 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
- ↑ Andersson JK. Treatment of scapholunate ligament injury: current concepts. EFORT open reviews. 2017 Sep;2(9):382-93.
- ↑ Jump up to:11.0 11.1 Duke Orthopaedics: Wheeless’ Textbook of Orthopaedics. http://www.wheelessonline.com/ortho/scapholunate_advanced_collapse_slac. (Accesed 15 October 2011).
- ↑ Opreanu RC, Baulch M, Katranji A. Reduction and maintenance of scapholunate dissociation using the TwinFix screw. Eplasty. 2009;9.
- ↑ Watson’s Test. http://en.wikipedia.org/wiki/Watson%27s_test. (accessed 24 October 2011).
- ↑ Imada AO, Welch K, Mlady G, Moneim MSA. The tangential view described by Moneim to demonstrate scapholunate dissociation: an update. Eur J Orthop Surg Traumatol. 2022.
- ↑ Jacobson MD, Plancher KD. Evaluation of hand and wrist injuriesin athletes. Operative Techniques in Sports Medicine. 1996 Oct 1;4(4):210-26.
- ↑ Jump up to:16.0 16.1 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.
- ↑ Jump up to:17.0 17.1 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.
- ↑ Jump up to:18.0 18.1 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.
- ↑ Jump up to:19.0 19.1 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.
- ↑ 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.
- ↑ Jump up to:21.0 21.1 21.2 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