CARPAL INSTABILITY

Dr.RUBEESH HASSAN

Carpal Anatomy• 2 CARPAL RAWS: DISTAL• Trapezium, trapezoid, capitate, hamate bound

together by strong interosseous (intrinsic) ligaments to form distal row, which moves together as a single unit

PROXIMAL– Scaphoid, lunate and triquetrum form the

proximal row. It has no muscle attachments and is inherently unstable in compression without its ligamentous attachments. Acts as a link between the relatively rigid distal row and the radioulnar articulations.

Intrinsic ligaments

• These have their origin and insertion within the same carpal row

• Distal row – To bind all the distal carpal bones together

• Proximal row – Scapholunate ligament – Lunotriquetral ligament

• Scapholunate ligaments is a C shaped ligaments composed of dorsal,central and volar subgroups.

• Dorsal subgroups is strongest,provide maximum stability.

• Additional stabilizers are• STT,SC -Dorsal stability Provide resistance against the tendency of the

saphoid to palmar flex.RSC AND RL Volar side stability.

• Lunotriquetral ligament• 3 subgroup• palmal aspect is thickest and provide

max stability to lunototriquetral stability.

• Proximal carpal bone has no tendinous insertion and thus often termed as INTERCALATED SEMENTS

• THREE Sets of tendons cross the proximal row• Extrinsic flexer and extensers of fingers• flexers and extensers of wrist• abducter pollicis longus and EPB•

Movements between the carpal bone is neglible

Movements of proximal carpal bone is determined by their ligamentous attachments and mechanical force of tendons that cross the wrist.

Biomechanics of the Wrist

• SL ligament is the most important factor in the spatial coherence of the carpus.

• The tendons that cross the proximal row exert a compressive force that is resisted by the connecting –rod action of scaphoid.

• Instability of scaphoid leads to an alternation of the articulation between the proximal and distal row.

Biomechanics of the Wrist

• During the radial deviation of the normal wrist the trapezoid and trapezium exert a volarly directed force on the distal pole of the scaphoid.

• This couses the scaphoid to flex about its waist.• This force is then transmitted to the lunate via SL

ligaments and to triquetrum via LT LIGAMENTS.• Thus proximal row radially deviate as one unit.

Biomechanics of the Wrist

Ulnar deviation of normal wrist causes the hamate to project a dorsally directed force on triquetrum.

As the triquetrum rotate dorsally by the hamate,a competent LT imparts an extension moments

on the lunate and indirctly to scaphoid via SL ligaments.

ScaphoidFlexion bias

TriquetrumExtension bias

Lunate

• In a balanced proximal row the lunate remains cantered on the distal radius without tilting into flexion or exension.

• The tendons that cross the wrist exert a compressive force across the carpus through the centrally located capitate at capitolunate articulation.

CLASSIFICATION

• Carpal instability is extremely difficult to classify and many classification schemes exist, each with advantages and disadvantages.

Direction of lunate

● Dorsal intercalated segmental instability (DISI) ● Volar intercalated segmental instability (VISI)

● Ulnar translocation ● Dorsal translocation

BASED Pattern of injury

● Carpal instability dissociative (CID) ❍ Dissociation within row Scapholunate, lunotriquetral● Carpal instability nondissociative (CIND) ❍ Instability between carpal rows Midcarpal instability, capitolunate

instability, ulnar translocation

BASED Pattern of injury

● Carpal instability complex (CIC) ❍ Feature of CID and CIND Perilunar injuries, axial carpal

dislocations ● Carpal instability adaptive (CIA) ❍ Extrinsic to wrist Dorsal malunion of the distal radius that causes

CIND

Injury to SL ligaments-DISI

DISI

• SL injury –a gap opens between the scaphoid and the lunate ,into which capitate eventually collapse.

• The scaphoid ,now free of its tether to lunte ,assumes a position of flexion.

• Lunate no longer balanced by flexion moment from scaphoid

• Lunate rotate dorsally ---DISI

ScaphoidFlexion bias

TriquetrumExtension bias

Lunate

VISI

• Isolated injury to LT is insufficient to allow the flexion moment of the scaphoid to palmar flex the lunate .

• However if dorsal radiocarpal is also injured tethering effect on dorsum of lunate is lost

• Scaphoid and lunate angle inti flexion ,while capitate begins to migrate between lunate and triquetrum.

• Thus injury to both LT and dorsal RC ligaments leads to VISI

MECHANISM OF INJURY

• Fall on outstretched hand-SL AND LT• Sports injury• High energy trauma -RTA

• Dissociative carpal instability is often directly caused by hyperextension of wrist

• Mayfield described a 4 part circular progressive injury termed as PLI

MAYFIELD STAGES OF PERILUNAR INSTABILITY

• Stage 1: dorsal migration of the proximal pole of scaphoid with resulting injury to the scapholunate ligaments

• Stage2: further extension ulnar deviation and supination of carpus leads to progression of the force

• Stage 3: progression of these forces leads to triquetrum to translate away from lunate with resultant injury to the LT ligaments.

• Stage 4: disruption of dorsal RC ligaments allow the lunate to rotate on its palmar ligmentous hinge and dislocate with resultant articulation of the capitate into the lunate facet of the radius.

SLAC

• Scapho Lunate Advance Collapse• In the setting of chronic SL ligament injury

arthritic changes may occure and the deformity of the capitate ,lunate ,and scaphoid may become static

• The abnormal position leads to wear of articular cartilage and serrounding articular surface resulting in a condition known as SLAC

SLAC -stages

• Stage 1:arthritic changes of the radial styloid

• Stage 2:arthritic changes of scaphoid facet of distal radius

• Stage3:arthritis of the articulation of capitate and lunate.

Clinical Features

• History• Fall on outstretched hand • Often presents late as a sprained wrist which fails to

resolve • Weakness of wrist, catching ,clunking or episodes of

giving away• Examination• Detailed palpation of all the landmarks • Grip strength often diminished

Special tests

• Scapholunate ballotment • Kirk-Watson’s test • Lunotriquetral ballotment • Reagan’s with 2 hands

Watsons shift maneuver

• Useful in determining the presence or absence of SL ligament injury

• Examiner sits across from the patient with a table in between

• Grasp the radial side of hand with his same hand• Thumb is placed over palmar side prominance of

scaphoid while fingers provide counter pressure on the dorsum of the wrist proximal to the carpal row.

Watsons....• The examiners other hand provides ulnar to radial deviation

by grasping the metacarpals.• As the wrist moves beyond neutral and to radial deviation ,the

dorsally directed pressure on the palmr aspect of the scaphoid may cause subluxation of scaphoid.

• This subluxaion may produce pain or apprehension in the patient

• Or examiner may feel subluxation• The pressure on the distal pole of the scaphoid released and

clunk may be realized as scaphoid relocate.• Always examine opposite side also –lig laxity

Scaphoid ballotment test

• Patient hand is held in pronation.• Examiner stabilise the lunate betwen thumb

and dorsally and index volarly• Hold scaphoid also in similar manner• Scaphoid is transilated dorsally and volarly

while noting the pain and transilation

Reagan test

• Lunatriquetral ballotment

INVESTIGATION

• X ray PA LATERAL VIEW OBLIQUE VIEW Evaluate static instability

• PA film in radial and ulnar deviation• Flexion and extension lateral view dynamic• Clenched fist view

The lines of Gilula

MRI

• FOR ligaments tear

• 3 T MRI IS 86 % SENSITIVE

ARTHOGRAPHY

• GOLD STANDARD for diagnosis of SL /LT ligaments tear is wrist arthroscopy

• Detect the tear and arthritic changes

Treatment

• Presence of arthritis• Degree of instability• Chronicity of condition• Associated injury• Functional demands of patients must be

considered

Non operative treatment

• Dynamic instability in acute setting may be amenable to conservative treatment

• But patient must understand the complication like future arthritis

• NSAID\LOCAL STEROID• Activity modification• Immobilisation

TreatmentSL injury

partial tear 1. Arthroscopic debridement +/- percutaneous pinning 2.capsulodesis

Dynamic instability without diastasis

• Arthroscopic debridement +/- percutaneous pinning

• Capsulodesis• RASL Screw fixation• Brunelli reconstruction

Acute tear with reducible diastasis

• Ligament repair –transosseous suture/anchor suture

• Capsulodesis• RASL Screw fixation• Brunelli reconstruction

Chronic tear with reducible diastasis

• Capsulodesis • Blatt capsulodesis• dorsal intercarpal lig capsulodesis• RASL Screw fixation• Brunelli reconstruction• Interosseous graft

irreducible diastasis/SLAC changes

• Scaphotrapeziotrapezoid Arthrodesis• Proximal row carpectomy• Scaphoid excision with 4 corner fusion

RASL procedure

• If repair of the scapholunate ligament is not possible,a headless compression screw may be used to approximate the scapholunate ligament via open /arhroscopic approach called a reduction and association of scaphoid and lunate procedure(RASL)

CAPSULODESIS

• BLATT CAPSULODESIS- this technique tether the scaphoid to the distal radius via a flap of dorsal capsuloligamentous tissue secured with suture anchor

• Loss of wrist flexion

capsulodesis

• Dorsal intercarpal ligament capsulodesis• Tether the scaphoid to triquedrum• This leads to long term acceptable function of

the wrist at the cost of early arthritis degeneration.

BRUNELLI RECONSTRUCTION

• Stabilizes the scaphoid in reduced position by passing FCR tendon through an interosseos scaphoid tunnel ad to distal radius.

SAMMARY

• Scaphoid serves as the connecting rod between the proximal and distal carpal rows.

• And is stabilised by the scapholunate ligament directly and lunotriquetral ligament indirectly.

• Disruption of either of this ligament leads to a pattern instability that left untreated leads to altered mechanics of wrist and ultimately arthritis and collapse.

SUMMARY

• Arthroscopy is gold standard• In acute setting conservaive treatmet may be

attempted.• But recalcitrant cases require surgical

stabilisation.• Salvage procedure are also available for those

patient who fail initial stabilisation.