Carpal Instability

Definition

Situation where normal alignment of carpal bones is lost

Aetiology

• DISI
  • due to disruption of scapho-lunate articulation
• VISI
  • secondary to disruption of lunate & triquetral
• Ulnar translocation
  • rarely results from injury but is commonly seen in wrists affected by rheumatoid arthritis

Epidemiology

Anatomy

• Two major groups of ligaments
  • extrinsic ligaments course between carpal bones & radius or metacarpals
  • intrinsic ligaments originate & insert in carpus
• extrinsic ligaments are stiffer while intrinsic ligaments are capable of greater elongation before permanent deformation occurs

Extrinsic

Palmar

• palmar extrinsic ligaments consist of 2 V-shaped ligamentous bands
  • one is proximal & connects forearm to proximal carpal row
    • proximal limb consists of
      • radiolunotriquetral & radioscaphoid ligs laterally
      • ulnolunate & ulnotriquetral ligs medially
  • one is distal & connects forearm to distal carpal row
    • distal limb of palmar extrinsic ligs consists of
      • radioscaphocapitate ligament laterally
      • ulnocapitate ligament medially

Dorsal

• dorsal extrinsic ligaments
  • radiotriquetral
  • scaphotriquetral

Intrinsic

• intrinsic ligs connect adjacent carpal bones
• Proximal row
  • intraarticular
    • connecting scaphoid to lunate & lunate to triquetrum
    • strong
    • critical for carpal stability

TFCC

• separates ulna from carpus
  • Made up of
    • TFC
    • dorsal & volar radio-ulna ligaments
    • ulnar collateral ligament
    • meniscus homologue
    • articular disc
    • sheath of ECU
  • Variable thickness of TFC from 1 – 5mm depending on station of ulna (ulna variance)
  • No tendons are directly attached to carpus

Rows/Columns

• Traditional view
  • proximal & distal row of carpal bones- scaphoid joining them
• Taliesnik
  • three columns
    • scaphoid being radial column
    • triquetral ulnar column
    • lunate & capitate with remaining carpal bones making up middle column
• Navarro
  • Three column modification
    • scaphoid, trapezium & trapezoid making up radial column
    • triquetral ulnar column
    • capitate & lunate along with hamate middle column

Pathology

Classification

4 major types of carpal instability

• DISI:
  • Dorsi-flexion (Dorsal Intercalated Segment Instability)
  • most common where lunate is rotated into dorsi-flexion
  • (zig zag alignment of radiolunatocapitate alignment)
• VISI:
  • Palmar flexion (Volar Intercalated Segment Instability or VISI)
• Ulnar Translocation
  • abnormal translocation of lunate ulnarward
    • Type 1 entire carpus is translocated ulnarward
    • Type 2 relationship between radius & scaphoid is normal but scapholunate gap is wide
  • rheumatoid
• Dorsal Subluxation
  • malunion fracture distal radius with reversal of normal palmar tilt

Instabilities may be

• Static
  • loss of normal alignment can be seen on XR
• Dynamic
  • routine XR within normal limits
  • instability can be produced by either voluntary movement or manipulation
    • eg between scaphoid + lunate, between lunate + triquetrum, or at midcarpal joint

Instabilities may also be termed

• Dissociative
  • S-L dissocation DISI
  • L-T dissociation VISI
• Nondissociative
  • may also result in VISI or DISI but 3 bones (S,L,T) act as unit
  • eg dorsal carpal subluxation, mid-carpal instability, Type1 ulnar translocations

History

Examination

• painful wrist
• clicking or clunking
• Ballottement test
• Watson test for scaphoid instability

Investigations

• AP
  • AP wrist under axial load (clenched fist)
  • hand in radial & ulnar deviation
  • Findings
    • May demonstrate ­ distance between scaphoid & lunate or lunate & triquetral
  • DISI pattern
    • ­scapholunate gap
    • ring sign
      • with flexed scaphoid seen end on
    • scaphoid foreshortened
      • distance between ring & proximal pole less than 7mm
    • flexed scaphoid is seen with dorsiflexed lunate
    • (quadrilateral) & with triquetrum in distal (dorsiflexed) position
  • VISI pattern
    • ring sign
    • scaphoid foreshortened
    • lunate volar flexed (triangular)
    • triquetrum distal in relation to hamate ( dorsiflexed)
    • distance between ulnar head & triquetrum is reduced ( Mayersbach sign)
    • convex outline of proximal carpal row (= Shentons line of wrist) is interrupted by step off between lunate & triquetrum
  • Ulnar Translocn
    • Carpal-Ulnar distance
      • is distance from centre of head of capitate ( ie centre of rotation of carpus) & line produced along line of centre of ulna
      • Normally ratio of C-U distance/ length of 3rd metacarpal = .30 ± .03
      • ¯ in ulnar translocation
• Lat: to assess opposite rotations of scaphoid & lunate

• DISI pattern
  • when scapholunate joint is dissociated
    • scaphoid is palmar flexed
    • lunate is dorsiflexed
  • Scapho-lunate angle
    • Normal 30- 60° (av 46o)
    • DISI > 70°
• VISI pattern
  • lunate palmar flexed
  • lunotriquetral angle
    • Normal -16 deg
    • Abn neutral or +ve
• Ulnar Translocation
  • often associated with VISI
• SLAC wrist (scapho-lunate advanced collapse)
  • With S-L dissocation
    • All load going through Radioscaphoid joint
    • degenerative process
  • • radial styloid & scaphoid
    • luno-capitate joint (commonest pattern of degeneration 55%)
    • triscaphoid degeneration
      • between scaphoid, trapezium + trapezoid
      • 2nd most common pattern
• Other Ixs
  • Bone scan
    • is useful to identify pathology
    • When bone scan is negative it suggests either that there is no injury or more frequently that problem is minor & can be treated non operatively
  • Arthrography
    • is helpful in finding ligament tears but ? significance as these may not necessarily be result of trauma but may indicate age related degenerative change
    • NB: need to compare with normal side
  • Arthroscopy
    • can directly visualise pathology

Differential Diagnosis

Treatment

• of chronic instability depends on patients symptoms
• Nonsurgical
  • little disability
  • > 80% of ROM
  • > 80% grip strength

Scapholunate dissociation

• Acute
  • either closed manipulation or open reduction with pinning
• Chronic: if no associated Osteoarthritis
  • reattachment of scapholunate ligament
  • dorsal capsuloligamentodesis (Blatt)
    • dorsal capsular flap used to prevent scaphoid from subluxing in palmar direction
    • ref : Blatt & Nathan ” Dorsal Capsulodesis for rotatory subluxation of scaphoid: review of long term results” Proc Am Soc of Surgery of Hand 1992
  • STT fusion
    • problem is with radial impingement
  • S-L or S-C fusion
    • if associated Osteoarthritis ( ie SLAC )
  • Excise (?replace) scaphoid & perform mid carpal fusion that is fusion of capitate, hamate, triquetral & lunate
    • (= 4 – corner fusion)
  • total wrist fusion

Lunatotriquetral instability

• Acute
  • either immobilisation in BEPOP or direct repair of ligament
• chronic
  • Lunatotriquetral arthrodesis

Ulnar Translocation

• Acute
  • Repair of disrupted volar & dorsal radiocarpal ligs
• Chronic
  • ligament repair unreliable
  • relocation of carpus & maintenance of reduction by radiolunate arthrodesis more reliable

Dynamic VISI & DISI

• trial of nonoperative management with AEPOP/ NSAIDS/ local injection of steroids
• Stabilisation of midcarpal joint limited fusion
• Capsuloligamentodesis
• tenodesis

Complications

Prognosis

References