Carpal Instability

Instability definition

  1. Abnormal load transmission (dyskinetics)
  2. Abnormal motion (dyskinematics)

Classification

Considerations

  1. Chronicity
  • Acute (<1 week) – optimal for treatment
  • Subacute (1-6 weeks) – reduced healing potential but possible
  • Chronic (> 6weeks) – reduction and primary healing unlikely
  1. Aetiology
  • Congenital
  • Traumatic
  • Inflammatory
  • Arthritis
  • Neoplastic
  • Iatrogenic
  • Other
  1. Location
  • Radiocarpal
  • Proximal intercarpal
  • Mid-carpal
  • Distal intercarpal
  • carpometacapal
  1. Constancy
  • Predynamic – no malalignment, only sporadic symptomatic dysfunction
  • Dynamic – malalignment only under stress
  • Static reducible
  • Static irreducible – permanent alteration of carpal alignment
  1. Direction
  • VISI rotation
  • DISI rotation
  • Ulnar translation
  • Radial translation
  • Volar translation
  • Dorsal translation
  • Proximal translation
  • Distal translation
  1. Pattern
  • Carpal instability dissociative (CID) - within same row
  • Carpal instability non-dissociative (CIND) – between adjacent rows
  • Carpal instability complex (CIC) – both same row and adjacent row
  • Carpal instability adaptive (CIA) – instability due to extrinsic pathology ie malunited distal radius fracture

Pathomechanics

  1. Direct
  • Related usually to crush over concavity of wrist
  • Causes global dissociation
  1. Indirect
  • Tensile forces transmitted by ligaments
  • Compressive forces transmitted by articular surfaces
Indirect mechanisms
  • Most often wrist extension, supination and ulnar deviation
  • Progressive perilunate instability (PLI) of Mayfield
  1. SL dissociation/Scaphoid fracture
  • Progressive tearing of the SLIL (from volar to dorsal – weaker to stronger) as lunate constrained by the short radiolunate ligament
  • With radial deviation – scaphoid becomes constrained and SLIL tears occurs with scaphoid fracture
  1. Lunocapitate dislocation
  • with progressive hyperextension, lunate dislocates volarly through rent in space of Poirier
  • radioscaphocapitate limits the dorsal translation of the distal row
  1. Lunotriquetral disruption/triquetrum fracture
  • LTIL ruptures dorsal to volar (volar is stronger)
  • Ulnocapitate ligament contraints may cause triquetral fracture
  1. Lunate dislocation
  • When all perilunate ligaments torn, lunate only held by dorsal capsule and long radiolunate ligament
  • Culminates in volar lunate extrusion as lunate hinges on volar radiolunate ligament


  • Reverse PLI has also been described
  • Extension injury with radial deviation and pronation
  • instability beginning with tearing of LTIL

Radiology

  • 4 important views
  1. PA (in 90deg shoulder abduction, 90deg elbow flexion
  2. Lateral
  3. Scaphoid (PA in ulnar deviation)
  4. 45deg semipronated oblique
  • Other views
  1. AP with clenched fist – shows SL dissociation
  2. Carpal tunnel view – for hook of hamate
  3. Oblique at 20deg pronation – dorsum of triquetrum
  4. Oblique at 30deg supination – pisotriquetrum and hook hamate
  • Examine
  • Lines of Gilula – 3 smooth arcs


  • Articulating space should be <2mm; >4mm abnormal
  • Shape of lunate on AP
  • Should be trapezoidal
  • VISI – C-shaped (moon)
  • DISI – oblique oval
  • Dislocation – triangular, base at radius
  • Measure


  • Capitolunate angle
  • Long axes of 3rd metacarpus, capitate, lunate, radius should be in a line
  • Draw line along lunate midaxis and along capitate midaxis on lateral. Angle should be -10 to 10 (mean 0)
  • Scapholunate angle
  • Line along lunate mid axis and scaphoid midaxis on profile
  • Angle should be 30 to 60 (mean 47)
  • Greater than 80 a definite indication of SL dissociation


  • Radiolunate angle
  • DISI or VISI if angle >15
  • Ulnar variance (J Hand Surg [Am]. 1989 Jul)
  1. Project a line technique
  • From ulnar side of the articular surface of the distal radius towards the ulnar and measure distance from line to carpal surface of ulnar
  1. Method of perpendiculars
  • Line of radius long axis and perpendicular line from that meeting ulnar border of radius
  • Measure from distal cortical rim of ulnar to this line
  • This method found to be the most reliable in terms of interobserver and intraobserver relaibility
  1. Concentric circles
  • Draw circle following curve of radius over to the ulnar side and measure distance to this line
  • Carpal Height
  • Examines carpal collapse
  • Carpal height ratio = carpus height/length of 3rd metacarpus (normal=0.54)
  • Alternative measure = carpal height/capitate height (normal = 1.57)


Other modalities

  1. CT – replaced tomograms
  2. Cineradiographs
  • Useful where routine and special views do not show the dissociation
  1. Arthrography
  • Poor correlation between symptoms and defects seen on arthrography especially in older patients where degenerative wear is common
  1. MRI
  • Most useful for carpal instabilities due to extrinsic soft tissue disease
  1. Bone scans
  • Helps localise where the problem is located
  1. Arthroscopy
  • Considered gold standard by many
  • Limitations
  1. Instability can’t be seen on arthroscopy, only tears
  2. Can only see intracapsular injuries
  3. Some derangements seen on arthroscopy may be asymptomatic
Carpal Instability: Dissociative
Scapholunate dissociation
  • force is applied to the thenar area with the wrist positionedin dorsiflexion and ulnar deviation.
  • Results in DISI deformity
Aetiology
  1. Trauma
  • Fall on extended outstretched hand, may be associated with distal radius (31% have acute SLD) or scaphoid fracture
  1. Iatrogenic
  • Excessive dorsal capsule excision with dorsal wrist ganglion excision
  1. Inflammatory disease
  • RA, infection
  1. Congenital
  • hyperlax ligaments – see bilateral increased SL gap on xray
Clinical
  • Pain
  • Weakness – grasp
  • Clicking
  • Stiffness
  • Swelling
  • Point Tenderness
  • SL joint palpated with wrist flexed distal to Lister’s
  • Also tender over snuffbox
  • Positive scaphoid shift test (Watson’s test)
  • Provocation test – resist full extension of index and middle fingers with wrist partially flexed (sensitive but not specific)
Investigations

Xray

  1. Increased SL joint space
  • Terry Thomas sign
  • measure gap from middle of scaphoid articulating facet
  • look for asymmetric gap of >5mm
  • If no trauma, suspect RA, gout, pseudogout
  1. Scaphoid ring sign
  2. Taleisnik V sign
  • Sharp angle between distal radius and palmar border of scaphoid on lateral

Arthroscopy

  • Excellent for visualising this joint
Classification (Watson’s)

Type 1:(predynamic)

Type 2:(dynamic) negative Xray; +ve Watson: +ve cine

Type3:(static) – positive plain films

Type 4:(SLAC)

Treatment
  1. Acute
  1. Closed reduction and POP
  • Unsatisfactory – no single position that reduces the SL joint
  1. Closed K wire
  • Best for acute to subacute injuries
  • Bad results if injury >3 months old
  1. ORIF + ligament repair
  • Dorsal approach between 3rd and 4th compartment
  • Most important ligament to repair is the dorsal part of SLIL
  • In addition consider dorsal capsolodesis

SLIL repair

  1. Subacute without arthrosis (and reducible)
  1. SLIL repair, needs to be supplemented by either…
  2. Dorsal radioscaphoid capsulodesis
  3. Blatt – proximally based capsule flap attached to point on scaphoid distal to axis of rotation
  4. Herbert – reverse Blatt
  5. Linsheild – uses ½ dorsal intercarpal ligament (triquetral-scaphoid ligament) based at scaphoid and attached to radius

Blatt capsulodesis

  1. Tenodesis
  2. Brunelli procedure most commonly done
  3. ½ FCR distally based bought dorsally with hole in scaphoid
  4. Sutured to dorsal SLIL and to dorsoulnar ridge of distal radius
  5. Avoids creating holes in lunate unlike earlier methods

  1. Chronic irreducible without cartilage degeneration
  1. STT arthrodesis
  2. Goal to realign proximal pole of scaphoid to radius
  3. Need to make sure that carpal height is maintained
  4. Important to reduce RS angle between 40-60
  5. With lack of scaphoid flexion, this may lead to increased impingement on radius
  1. SL arthrodesis
  2. Unreliable – small area of contact thus difficult to fuse
  3. SLC arthrodesis
  4. 50% reduction in wrist motion
  5. Leads to significant reduction in pain and return to heavy work
  1. Chronic irreducible with cartilage degeneration
  • Arthritis begins at radial styloid and distal scaphoid, then whole of RS joint, midcarpal joints starting at LC interval.
  • RL joint typically spared
  1. RSL arthrodesis
  2. Arthritis confined to the radiocarpal joint
  3. Radial styloidectomy
  4. Beware not to detach volar radiocarpal ligaments – lead to more instability
  5. SLAC operation
  6. Requires intact RL joint
  7. Scaphoid excision and capitate-lunate-triquetrum-hamate(4 corner) fusion
  8. Proximal row carpectomy
  9. Good at relieving pain
  10. Will have significant grip weakness
  11. Unlike SLAC operation, avoids long term immobilisation and risk of non-union
  12. Advantage of being convertible to total wrist arthrodesis/arthroplasty
  13. Total wrist arthroplasty
  14. For low demand patients only (ie RA patient)
  15. Not acceptable in young patients
  16. Total wrist arthrodesis
  17. Good pain relief
  18. Procedure of choice for some heavy manual workers

Lunotriquetral Dissociation

  • fall on the outstretched hand in pronation, extension, and radial deviation
  • resultant intercarpal pronation overloads the ulnar-volar ligament structures and causes LTq ligament injury without scapholunate disruption.
  • Isolated LTq dissociations result from ulnar sided injury or when SL portion heals spontaneously
  • In non-traumatic cases, positive ulnar variance may facilitateLTq ligament degeneration by means of a wear mechanism or alteration of intercarpal kinematics.
  • This leads to a VISI pattern

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Pathomechanics

  • with loss of the integrity of the LTligament, the triquetrum tends toextend, while the scaphoid andlunate attempt to flex.
  • Furthermore loss of dorsal intercarpal and dorsal radiocarpal ligament allow lunate to flex more

Clinical

  • fall on the dorsiflexed wrist with a hypothenar contact point
  • pain worse with ulnar deviation, pronation and axial compression
  • Palpation will always demonstrate point tenderness at the LT joint.
  • Provocation tests (sensitive but poorly specific)
  1. Reagan ballottement test
  2. ballot pisotriquetral unit against lunate
  3. Kleinman shear test
  4. Stabilise lunate and push pisotriquetrum dorsally
  5. Ulnar snuff box test
  6. Radially directed pressure over ulnar snuff box

Differentials for ulnar sided pain

Investigations

  • Xray
  • examine for step-off between lunate and Tq in line of Gilula
  • do not see increase LTq gap
  • scapholunate angle may be diminished from its normal47 degrees to 40 degrees orless but is often normal.
  • Cineradiology
  • Very useful indemonstrating the site of a clunk that occurs with deviation.
  • Bone scans
  • Helpfulwhen standard films and motionstudies are negative.

Management

1. Acute Dynamic VISI

  1. Nonsurgical with cast immobilisation
  2. Midcarpal corticosteroid injections can be helpful in decreasingsynovitis.

2. VISI collapse unresponsive to conservative management,

  1. operative treatment indicated

Surgical options

  • goal is the realignment of the lunocapitate axis and reestablishment of the rotational integrity of the proximalcarpal row.
  1. LTq arthrodesis
  2. ligament repair
  3. dorsal and volar approach
  4. volar LTIL is reattached to the site of its avulsion,generally from the triquetrum.
  5. plication of the dorsal radiotriquetral and dorsal scaphotriquetral ligament
  1. ligament reconstruction
  2. distally based strip of extensor carpi ulnaris tendon
  • If concomitant negative or positive ulnar variance or midcarpal or radiocarpal arthrosis is present, additional procedures, such as ulnar lengthening or shortening, midcarpal arthrodesis,or proximal-row carpectomy
  • LT arthrodesis
  • Up to 50% non-union rate
  • Found to be inferior to ligament repair/recon
  • Total wrist arthrodesis
  • appropriate if degenerative changes make other salvage procedures impossible.

Carpal instability non dissociative

Classification

  1. Radiocarpal
  2. Commonly seen in RA patients
  3. Midcarpal
  4. Palmar
  5. Dorsal
  6. Dorsal and palmar
  7. Extrinsic

Carpal instability Complex

Classification

  1. Lesser Arc injuries (dorsal perilunate dislocations)
  2. Closed reduction and plaster
  3. Closed K wire
  4. ORIF
  5. Greater Arc injuries (dorsal perilunate fracture-dislocations)
  6. Trans-scaphoid, trans-capitate Trans-triquetrum perilunate dislocations
  7. Extremely rare – only 2 described
  8. Trans-scaphoid perilunate dislocations
  9. Trans-scaphoid, trans-capitate perilunate dislocations
  10. Trans-triquetrum perilunate dislocations
  11. Palmar perilunate dislocations
  12. Very rare
  13. Forced hyperflexion and supination
  14. Axial dislocations
  15. Dorsopalmar compression on wrist
  16. Wrist splits into 2 columns
  17. One remaining aligned to the radius and the other unstable, displacing radially or ulnarly
  18. Isolated carpal bone dislocations