Carpal Instability - DISI/VISI

Progressive Perilunar Instability

Sequential ligament disruption pattern in hyperextension injuries:

Stage I: Scapholunate ligament rupture resulting in SL dissociation.

Stage II: Plus capitolunate dislocation resulting in perilunate dislocation.

Stage III: Plus lunotriquetral ligament rupture causing LT disruption.

Stage IV: Plus dorsal radiocarpal ligament rupture causing lunate dislocation into carpal tunnel.

Each stage includes all previous stages - Stage IV has complete ligamentous disruption around the lunate.

Six-Stage Classification for SL Instability

Stage 1: Partial SL tear, no DISI - treat with arthroscopic debridement.

Stage 2: Complete SL tear, repairable, no DISI - treat with direct repair plus K-wires.

Stage 3: Complete tear, irreparable, no DISI - treat with dorsal capsulodesis.

Stage 4: Complete tear, DISI, reducible, no arthritis - treat with tendon reconstruction (RASL, modified Brunelli).

Stage 5: DISI, reducible, with arthritis - treat with limited fusion (STT, SC).

Stage 6: Irreducible DISI, severe arthritis - treat with salvage procedures (PRC, wrist fusion).

Instability Pattern Progression

Pre-dynamic: Pain and tenderness only. Normal radiographs including stress views. Partial ligament injury. Best prognosis with conservative treatment.

Dynamic: Normal standard radiographs. Abnormal stress views or fluoroscopy. Complete ligament tear with secondary restraints intact. May benefit from early surgical intervention.

Static Reducible: Abnormal standard radiographs. Malalignment correctable passively. Secondary restraints incompetent. Requires surgical stabilisation.

Static Irreducible: Fixed malalignment. Cannot be corrected without surgery. Often associated with arthritis. May require salvage procedures.

Lunotriquetral Instability Grading

Grade I: Partial tear with no instability. May be managed non-operatively with splinting. Good prognosis.

Grade II: Dynamic instability with positive provocative tests. Normal resting radiographs. Consider ligament repair or reconstruction.

Grade III: Static VISI deformity on standard radiographs. Complete ligament disruption. LT arthrodesis often preferred treatment (90% union rate).

Imaging Studies

Plain Radiographs

Standard Views:

• PA view - carpal spacing, arcs of Gilula
• True lateral - carpal angles (most important for DISI/VISI)
• Scaphoid view - scaphoid pathology
• Contralateral comparison - essential for borderline cases

Key Measurements on Lateral View:

Scapholunate Angle:

• Line along long axis of scaphoid
• Line perpendicular to lunate distal articular surface
• Normal: 30-60 degrees (average 47 degrees)
• DISI: greater than 70 degrees
• VISI: less than 30 degrees

Capitolunate Angle:

• Line along long axis of capitate
• Line perpendicular to lunate
• Normal: less than 15 degrees
• Greater than 15 degrees = instability

Radiolunate Angle:

• Long axis of radius to lunate
• Normal: neutral (0 degrees ± 10)
• Abnormal in DISI/VISI patterns

PA View Findings:

SL Gap (Terry Thomas Sign):

• Normal SL interval: less than 3mm
• Greater than 3mm suggests SL injury
• Greater than 5mm = complete SL tear
• Compare to contralateral side

Gilula's Arcs:

• Arc I: Proximal carpal row proximal surfaces
• Arc II: Proximal carpal row distal surfaces
• Arc III: Capitate-hamate proximal surfaces
• Disruption indicates intercarpal pathology

Scaphoid Ring Sign:

• Cortical ring appearance of scaphoid
• Indicates scaphoid flexion (rotatory subluxation)
• Seen in SL dissociation/DISI

Stress Radiographs

Clenched Fist View:

• AP view with tight fist
• Loads scapholunate interval
• May reveal dynamic widening

Radial/Ulnar Deviation Views:

• Maximum radial and ulnar deviation
• Assess scaphoid motion
• Dynamic DISI may only appear in radial deviation

Fluoroscopy:

• Real-time assessment of carpal motion
• Dart thrower's arc evaluation
• Provocative manoeuvres under imaging

Advanced Imaging

MRI:

• Soft tissue ligament visualisation
• SL and LT ligament integrity
• Associated TFCC pathology
• Bone marrow oedema pattern

MR Arthrography:

• Gold standard for ligament tears
• 90% sensitivity/specificity for SL tears
• Contrast leak patterns:
  • Radiocarpal space leads to midcarpal = SL tear
  • Midcarpal leads to radiocarpal = LT tear

CT:

• Bone detail
• Fracture identification
• 3D reconstructions for surgical planning

Arthroscopy:

• Definitive diagnostic tool
• Allows dynamic assessment
• Grading of ligament tears (Geissler classification)
• Therapeutic intervention possible

Geissler Arthroscopic Classification

Grade I:

• Attenuation/haemorrhage of interosseous ligament
• No instability with probing

Grade II:

• Ligament attenuation with incongruity
• Step-off visible between carpal bones
• Probe cannot be passed between bones

Grade III:

• Incongruity and step-off
• Probe can pass between bones (from midcarpal side)
• Volar ligament intact

Grade IV:

• Complete ligament disruption
• 2.7mm arthroscope passes through gap
• Gross instability

Indications:

Pre-dynamic instability with partial ligament tears and no instability on examination. Patient factors precluding surgery. Temporary stabilisation before definitive surgery.

Treatment Protocol:

Immobilisation in slight flexion and ulnar deviation for 4-6 weeks with cast or splint. Physiotherapy for proprioception and grip strengthening. Activity modification to avoid provocative movements. Serial examinations to monitor for progression.

Acute SL Injury (under 6 weeks):

Geissler I-II: Arthroscopic debridement for partial tears without instability. Thermal shrinkage controversial with limited long-term evidence.

Geissler III-IV: Open dorsal approach with direct ligament repair using suture anchors. K-wire fixation of SL and SC joints. 8-12 weeks immobilisation. Best results with acute intervention.

Chronic SL Injury (over 6 weeks, no arthritis):

Dorsal Capsulodesis (Blatt Procedure): Capsular flap attached to scaphoid to limit flexion. Reasonable short-term results but may stretch over time.

Tendon Reconstruction: RASL, Brunelli, modified Brunelli techniques. Bone-retinaculum-bone graft or internal brace augmentation options available.

With Arthritis:

Limited Fusions: STT or scaphocapitate fusion preserves some motion. Salvage Procedures: PRC, four-corner fusion, or total wrist fusion for severe cases.

Acute LT Injury:

Direct repair via palmar or dorsal approach with suture anchor fixation and K-wire stabilisation. Better outcomes than chronic repair.

Chronic LT Injury:

LT Arthrodesis: Most reliable option with high union rate using compression fixation. Minimal motion loss as LT contributes little to wrist motion. May address VISI deformity.

Ligament Reconstruction: Tendon graft techniques less predictable. Reserve for young, high-demand patients.

With Arthritis:

LT fusion addresses instability and pain with limited motion sacrifice. Salvage procedures (PRC, wrist fusion) for severe cases.

SL Instability Algorithm:

Dynamic instability with no DISI: Capsulodesis or ligament repair.

Static DISI, reducible, no arthritis: Tendon reconstruction (modified Brunelli, RASL).

Static DISI with arthritis: Limited fusion (STT, scaphocapitate) or salvage (PRC, four-corner fusion).

LT Instability Algorithm:

Dynamic VISI: Direct repair if acute, reconstruction if chronic.

Static VISI, no arthritis: LT arthrodesis (preferred) or reconstruction.

Static VISI with arthritis: LT fusion or salvage procedures.

Setup and Approach:

Supine position with arm table, tourniquet applied to upper arm. Dorsal longitudinal incision centred over Lister's tubercle extending 4-5cm. Develop interval between 3rd and 4th extensor compartments. Protect extensor tendons and create dorsal capsulotomy (ligament-sparing or traditional).

Direct Repair Technique:

Identify torn SL ligament remnants. Debride non-viable tissue. Place suture anchors in scaphoid and lunate. Repair dorsal SL ligament with non-absorbable sutures. May augment with dorsal capsulodesis.

Reconstruction (Modified Brunelli):

Harvest FCR tendon strip (10cm length, 1/2 width). Drill 3.2mm tunnel through scaphoid from distal pole to SL interval. Pass tendon graft through scaphoid tunnel. Anchor to lunate with suture anchor or bone tunnel. Tensioned with wrist in neutral or slight extension.

K-wire Fixation:

Place 1.1-1.4mm K-wires across SL joint (2 wires) and scaphocapitate joint (1-2 wires). Check reduction fluoroscopically. Wires remain 8-10 weeks.

Approach:

Dorsal ulnar incision between 4th and 5th extensor compartments. Identify and protect DRUJ and ECU tendon. Expose LT joint through dorsal capsulotomy.

Preparation:

Remove articular cartilage from lunate and triquetrum using curettes or burr. Preserve subchondral bone plate. Create bleeding cancellous surfaces.

Fixation:

Reduce VISI deformity, confirm with lateral fluoroscopy. Place compression screw (headless cannulated) or plate/screws. Add autograft or allograft bone graft. Consider K-wire augmentation. Assess reduction and hardware position fluoroscopically.

Proximal Row Carpectomy (PRC):

Remove scaphoid, lunate, and triquetrum. Capitate articulates directly with lunate fossa of radius. Preserves approximately 50% wrist motion. Contraindicated if capitate head cartilage damage.

Four-Corner Fusion (Scaphoid Excision):

Remove scaphoid. Fuse lunate, capitate, triquetrum, hamate. Preserve approximately 50% wrist motion. Better for heavy manual labourers than PRC.

Total Wrist Fusion:

Ultimate salvage for failed reconstruction or severe pancarpal arthritis. Fuse radius to metacarpals via dorsal plate. Eliminates wrist motion but provides reliable pain relief and stability.

Reduction Assessment:

True lateral radiograph essential. Confirm SL angle correction (target 47 degrees). Check scaphoid ring sign resolved on PA view. Verify Gilula's arcs restored.

Common Pitfalls:

Inadequate ligament repair tension. Failure to address secondary restraints. K-wire migration or breakage. Overtensioning reconstruction causing stiffness.

Postoperative Protocol:

Long-arm cast/splint for 2-4 weeks then short-arm for 4-6 weeks. K-wire removal at 8-10 weeks. Protected motion in thermoplastic splint. Full rehabilitation over 3-6 months.

Complications of Carpal Instability

Natural History (Untreated)

DISI/Scapholunate Dissociation:

• Progressive radioscaphoid arthritis
• SLAC wrist pattern (Stages I to II to III)
• Similar to SNAC wrist progression
• 30-50% develop arthritis within 10 years

VISI/Lunotriquetral Dissociation:

• Less predictable progression
• Ulnocarpal impaction may develop
• Midcarpal arthritis possible
• Generally slower progression than DISI

Complications of Surgery

Early Complications:

Infection:

• Superficial: 2-5%
• Deep: less than 1%
• Treatment: antibiotics, debridement if needed

Nerve Injury:

• Superficial radial nerve (dorsal approach)
• DBRCU (dorsal approach)
• Posterior interosseous nerve
• Usually neuropraxia, resolves

Hardware Problems:

• K-wire migration/breakage
• Screw prominence
• Removal often required

Late Complications:

Persistent Instability:

• Incomplete ligament healing
• Stretched repair
• May require revision or salvage

Stiffness:

• Common after prolonged immobilisation
• Intensive physiotherapy required
• May require tenolysis/capsular release

Recurrent DISI/VISI:

• Progressive stretching of reconstruction
• Revision surgery options limited
• May progress to salvage

Secondary Arthritis:

• Altered joint loading
• Progressive cartilage degeneration
• Ultimate outcome similar to untreated instability
• Salvage fusion may be required

Procedure-Specific Complications:

Limited Fusions (STT, SC):

• Non-union: 5-15%
• Hardware prominence
• Adjacent joint arthritis
• Residual instability

Proximal Row Carpectomy:

• Radiocapitate arthritis
• Progressive pain
• May require total wrist fusion

Total Wrist Fusion:

• Loss of all wrist motion
• Hardware failure
• Non-union: less than 5%
• Adjacent joint stress

Managing Failed Surgery

Workup:

• Detailed history: what was done, when, outcomes
• Physical examination
• CT for fusion assessment
• MRI for soft tissue evaluation
• Diagnostic arthroscopy if needed

Revision Options:

• Re-repair/reconstruction (early failure)
• Conversion to limited fusion
• Salvage procedures

Patient Counselling:

• Progressive procedures available
• Each surgery reduces options
• Ultimate salvage is wrist fusion
• Realistic expectations essential

Immobilisation:

Long-arm cast or splint for first 2-4 weeks to control forearm rotation. Transition to short-arm cast/splint for remaining 4-6 weeks. Wrist positioned in slight extension and ulnar deviation.

Monitoring:

Wound check at 10-14 days. Suture/staple removal at 2 weeks. Monitor for infection, neurovascular compromise. X-rays at 2 and 6 weeks to assess hardware and reduction.

Early Exercises:

Active finger ROM from day one to prevent stiffness. Shoulder and elbow ROM exercises. Oedema control with elevation and compression.

K-wire Removal:

Typically at 8-10 weeks under local anaesthesia. Confirm radiographic healing before removal. May delay if healing concerns.

Protected Motion:

Custom thermoplastic splint for protection. Begin active-assisted wrist ROM exercises. Avoid resisted gripping and loading. Continue finger and forearm ROM.

Therapy Initiation:

Formal hand therapy begins. Scar management and desensitisation. Progressive wrist flexion/extension and radial/ulnar deviation.

Progressive Strengthening:

Gradual introduction of grip strengthening. Theraband exercises for wrist strengthening. Proprioceptive training with unstable surfaces. Functional activity training.

Return to Activity:

Light desk work at 8-12 weeks. Light manual work at 3-4 months. Heavy manual work at 6-12 months. Contact sports at 6-12 months with protective splinting initially.

Ongoing Assessment:

Serial radiographs to monitor alignment. Clinical assessment of stability. Functional outcome measures (DASH, PRWHE).

Examination Practice