Carpal Instability

Scapholunate ligament

• C shaped ligament composed of dorsal, central and palmar subregions.

• Dorsal aspect most thick.

• Central aspect separated from the volar region by radioscapholunate ligament.

• Ligament of Testut

• The Scaphocapitate and STT ligaments present dorsally resist palmar flexion of scaphoid.

• The RSC ligament and short and long radiolunate ligament on palmar aspect.

• The Lunotriquetral ligament also has 2 layers, with the volar region more thick.

• Proximal carpal row has no tendinous attachments and is called intercalated segment.

• Movement between the carpal bones is determined by ligamentous attachments and mechanical forces crossing the wrist.

Biomechanics

• Lunate exists in suspension between the scapholunate ligament and lunotriquetrum lig.

• Scaphoid and triquetrum exert flexion and extension moment respectively.

• Tendons crossing the carpus exert compressive force on lunate through capitate.

Mechanism of injury

• Fall on outstretched hand, high energy injuries.

• Hyperextension of wrist.• Mayfield- 4 stage progression.– Wrist extension.– Ulnar deviation.– Carpal supination.

Progressive Perilunar Instability

• I- dorsal migration of proximal pole of scaphoid Scapholunate injury.

• II- extension, supination and ulnar deviation leads to force transmitted through space of Poirier.

• Triquetrum translates away from lunate LT ligament injury

• Dorsal radiocarpal ligament dissociation lunate rotates on its palmar hinge and dislocates with capitate articulating with the radius.

• Arthritic changes may occur in the setting of chronic scapholunate ligament injury and deformity of lunate, capitate and scaphoid may become static.

• Scapholunate advanced collapse (SLAC)

SLAC

History

• H/o specific injury to the wrist.• Position of wrist.• Pain, swelling and instability; progressing to

inability to use the hand.• Carpal Tunnel Syndrome.• Subacute or chronic injuries may present with

pain and decreased grip.

Examination

• Localise point tenderness.• Pain elicited by radial or ulnar deviation of

wrist.• Tenderness over the lunotriquetral ligament or

scapholunate ligament.• Pain with subjective or palpable clicking or

popping feel.

Watson Shift Test

• Pain, apprehension and subluxation of scaphoid.

• Movement of the wrist- smooth or with crepitus.

• Positive clunk on releasing pressure as scpahoid relocates.

• Examine opposite side for laxity which can give false positive results.

Scaphoid Ballotment Test

Lunotriquetral ligament injury

• Ulnar sided wrist pain.• Reagan test- Lunotriquetral ballottement.• Kleinman shear test( Lunotriquetral Shuck

test)

X rays

• PA, Lateral and Oblique• Evaluate static

instability patterns, fractures, or dislocations.

• PA films in radial/ ulnar deviation.

• Clenched fist/Pencil view.

• Flexion and extension laterals

• Dynamic stability.• Forearm in neutral

rotation.

Gilula lines

Terry Thomas sign

Signet ring sign• Distal pole of scaphoid is

palmar flexed while the lunate is extended dorsally.

• Cortical border of distal and proximal pole align in PA view.

• Lunate triangular not hexagonal

• Longitudnal axes of third metacarpal, lunate,capitate and radius are collinear.

• Perilunate dislocations show collinearity of radius and lunate while the capitate is dorsally located.

• Scaphoid axis- line that connects the proximal and distal poles.

• Lunate axis- Line connecting the midpoint of the convex proximal surface to the concave distal articular surface.

• Scapholunate angle more >60 deg – DISI

• < 30 deg- VISI

• Dissociative instability- disruption of intrinsic interosseous ligaments.

• Nondissociative- Extrinsic radiocarpal ligaments disrupted, intact intrinsic ligaments.

• 3-T MRI has sensitivity of 86% for detecting scapholunate tears and 82% for detecting lunotriquetral tears compared with arthroscopy.

Magee T.Comparison of 3-T MRI and arthroscopy of intrinsic wrist ligament and TFCC tears. AJR Am J Roentgenol 2009;192:80–5

• Injection of gadolinium into the midcarpal joint should show the flow of dye into the midportion of the scapholunate interval, but not into the radiocarpal joint.

Tirman RM, Weber ER, Snyder LL, et al. Midcarpal wrist arthrography for detection of tears of the scapholunate and lunotriquetral ligaments. AJR Am J Roentgenol 1985;144:107–8.

Wrist arthroscopy

• Gold standard for detecting Scapholunate and lunotriquetral injury.

• Direct visualisation.

• Location and size of insult.

• Presence of arthritic changes within the joint space.

Geisslers classification

Carpal Instability

• Carpal instability dissociative( CID)– Dissociation between interosseous ligaments

• Carpal instability non dissociative(CIND)– Instability of carpal row as a whole

• Carpal Instability Complex (CIC)– Combination of above two injuries

• Carpal Injury Adaptive (CIA)– Secondary changes in carpus resulting from non

union or malunion or the carpal bones

Treatment concepts

• Acute injuries- Closed or arthroscopically controlled manipulation and percutaneous pinning; Open reconstruction/repair.

• Instability w/o arthrosis- ligament reconstruction, capsular imbrication and limited intercarpal arthrodesis.

• Dorsal capsulodesis to limit scaphoid flexion.

• Fixed deformity, arthrosis, pain or interference with function- excisional arthroplasty, limited intercarpal arthrodesis and wrist fusion.

Ligament repair

Ligament Reconstruction

• Free tendon grafts or tenodesis using prolonged slips of wrist flexors or extensors.

• Linscheid and Dobyns suggested that procedure be limited to patients whose ligament ruptures cannot be maintained with closed reduction, patients diagnosed after 1 month.

• Not indicated in patients with degenerative joint disease.

• Complications-– Tendons may stretch and become lax– Bone tunnels may lead to fracture and vascular

changes.– Tightness required to maintain bony apposition

may eventually limit wrist motion.

Palmer, Dobyns and Linscheid

Almquist repair- 4 bone ligamentous repair

Taleisnik and Linscheid

Brunelli and Brunelli

Talesnik

VISI (FCU) DISI (ECRB)

Capsulodesis (Blatt)

• Useful for scapholunate dissociation and caput ulnae syndrome (DRUJ incongruity)

• Ability to anatomically reduce the scaphoid.

Limited Wrist (Triscaphe) Arthrodesis

• Pain relief with functional arc of motion.

• Indications– Degn arthritis of STT joint with normal thumb CMC joint– Radial hand dislocations– Rotary subluxation of scaphoid– Scapholunate diastasis of > 2mm– Scaphoid angle of >60 deg on true lateral.– Foreshotening of scaphoid in AP view.

STT fusion (Watson)

• Scaphocapitate arthrodesis• Scaphocapitolunate arthrodesis• Lunotriquetral arthrodesis.