Hand Bone

Carpal instability and lunate disorders

Scapholunate dissociation, perilunate instability, Kienbock disease, wrist fusion.

23 questions 4 source pages 1 fact-check flags

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Q1Describe the X-ray findings of scapholunate dissociation.▸

Widened SL interval >3mm (Terry Thomas sign)
Gilula line broken - intercarpal alignment disrupted, DISI, scaphoid flexed
Lateral view: SL angle >60deg (DISI)
OA change between scaphoid and radius; midcarpal joint not involved
Likely SLAC Watson stage 2; mention carpal height

Q2Describe the Watson (SLAC) classification.▸

I: radial styloid
II: scaphoid fossa
III: capitolunate
IV: pan-arthritis

Q3Describe the Geissler classification.▸

Arthroscopic classification for acute SL dissociation
Grades: hemorrhage, incongruent, probe through, scope through
Stage: pre dynamic/dynamic/static/reducible DISI/irreducible DISI/SLAC

Q4How is Watson's test performed?▸

Elbow in 90deg flexion, neutral forearm rotation
Scaphoid flexes on radial deviation and extends on ulnar deviation
Examiner's thumb gives a dorsal directed force to the scaphoid tubercle; wrist deviated from ulnar to radial
Positive if a clunk is felt, with dorsal subluxation of the scaphoid over the dorsal rim of the radius

Q5How is SL dissociation managed (Garcia-Elias)?▸

Predynamic/acute dynamic: dorsal repair + K wire fixation
Chronic, no SLAC, reducible DISI: reconstruction - anatomical (BLB/BRB) or non-anatomical with capsulodesis (Blatt DIC, Linscheid ECRL, Brunelli FCR)
Chronic, no SLAC, not reducible DISI: STT fusion + radial styloidectomy
SLAC 1: radial styloidectomy + SL reconstruction/ PIN and AIN neurectomy; 2: scaphoidectomy + 4 corner/PRC; 3: 4 corner or total wrist fusion; 4: total wrist fusion

Q6Compare PRC with four corner fusion.▸

Systematic review 2015 J Hand surg Eur Saltzman: 4 corner fusion: better grip strength
PRC: better ROM, fewer complications; no implant, no nonunion problems
PRC cons: reduced grip strength, longer rehab, 100% OA at 10 years
PRC prerequisites: RSC intact, no CL arthritis, stable midcarpal joint

Q7What factors are taken into account when managing SL dissociation?▸

Integrity and quality of the dorsal SLL
Posture of the scaphoid (DISI)
Carpal alignment and cartilage status

Q8Describe the Moneim classification.▸

Based on the presence of intercarpal dissociation
Type 1: without associated intercarpal dissociation
Type 2: with associated intercarpal dissociation

Q9Describe the Dumontier classification.▸

Based on the presence of radial styloid fracture
Type 1: purely ligamentous or only a small cortical avulsion
Type 2: associated with a large radial styloid fracture

Q10Which ligaments are involved in perilunate instability?▸

RSC, LRL, SRL, UC, UT, UL

Q11Describe the three column fixation concept.▸

Radial column: radial styloid to scaphoid pinning
Intermediate column (lunate facet): SRL and RSC ligament repairs + radiolunate K wire
Ulnar column: DRUJ pinning
Conservative if stable; otherwise ligament repair/reconstruction

Q12Describe the X-ray findings of this lunate pathology.▸

Lunate sclerosis with collapsed height; suspected carpal height collapse
No features of STT arthritis; signet ring sign on AP view
DISI on lateral view with reduced SLA
Ulna minus on PA X-ray, radial inclination within normal limits
Consistent with Lichtman type IIIB Kienbock disease; Ddx infection, trauma

Q13How is carpal collapse quantified?▸

Nattrass index (carpal height / capitate) <1.57
Youm index (carpal height / 3rd metacarpal) <0.54
Stahl index (lunate height to width ratio) <0.53
McMurtry (ulnar central axis to capitate / ulnar axis to 3rd MC) 0.27-0.33

Q14What are the hypotheses and risk factors for Kienbock disease?▸

Avascular necrosis of the lunate of unknown aetiology; biological, mechanical or mixed cause
Biological: single intraosseous/extraosseous vessel variation; 7-20% have a single palmar vessel
Mechanical: ulnar minus, increased radial inclination, lunate morphology (Zapico 1 trapezoidal worst)
Ask about age, functional demands, occupation; risk factors such as alcohol and steroid intake
CT: coronal split; MRI: vascularity (decrease T1 signal), articular congruency (decreased T1 signal suggests AVN)

Q15Describe the Lichtman classification of Kienbock disease.▸

1: X-ray normal
2: sclerosis without collapse
3: collapse - 3A normal scaphoid alignment, 3B fixed scaphoid rotation with ring sign, 3C coronal split
4: pan arthritis
Bain arthroscopic classification looks for articular surface involvement

Q16What are the surgical aims in early versus late Kienbock disease?▸

Early (I-IIIA): revascularize + redistribute load
biologically revascularize: 4,5 ECA pedicle graft, vascularised pisiform transfer, 2nd dorsal intermetacarpal artery
Mechanical: UV minus -> radial shortening; UV positive/neutral -> radial wedge osteotomy or capitate shortening
Postop Exfix to protect joint level procedure
Stage 3B: excise lunate + rolled PL graft and STT fusion, more motion preserved, or SC fusion (larger fusion area, better load transfer); or PRC
Late stage: remove pain generator and transfer load to radial column and salvage remaining carpal height
Late/arthritis: PRC or total wrist fusion/replacement

Q17Why are symptoms rather than radiology the guide to treatment in Kienbock disease?▸

Radiological findings do not correlate well with patient symptoms
Treat if symptomatic: start conservative with activity modification, splint, NSAID for 3-6 months

Q18What examination findings are important in Kienbock disease?▸

ROM
Swelling
Tenderness just distal to Lister tubercle

Q19What are the Zapico lunate morphology types and what is the vascular supply prevalence?▸

Zapico: 1 trapezoidal (worst), 2 rectangular, 3 double facet
Majority of lunates have both dorsal and palmar vessels with rich anastomoses
7-20% have a single palmar vessel supplying the whole lunate
Intraosseous prevalence: Y > I > X

Q20Describe the Bain arthroscopic classification of Kienbock disease.▸

0: 0 (no involvement)
1: proximal lunate
2a: proximal lunate + radius articular surface
2b: split of both distal and proximal lunate surfaces
3: both lunate + radius
4: 3 + proximal capitate

Q21What position is the wrist fused in and why?▸

Extension 20deg for grip strength
Neutral or 10deg ulnar deviation

Q22What are the functional movements of the wrist?▸

40deg flexion/extension
10deg radial deviation
30deg ulnar deviation

Q23How much of wrist ROM comes from each joint?▸

60% radiocarpal joint
30% intercarpal
10% intracarpal

Fact check

Youm index <0.54 and Nattrass index <1.57 indicate carpal collapse — imprecise — These are the normal population means, not fixed cut-offs: Youm carpal height ratio is 0.54 +/- 0.03 (normal range about 0.51-0.57) and Nattrass index is 1.57 +/- 0.05 (range about 1.52-1.62). Compare with the contralateral wrist rather than a single threshold. — (medium confidence) — source

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Carpal instability and lunate disorders

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