Kienbock's Disease
“AVN of lunate. Also known as lunatomalacia.”
- Affects dominant hand; rarely bilateral.
- Cause unknown – ? repetitive microtrauma causing vasc compromise & AVN
Biomechanical
- Negative ulnar variance à ↑ shear forces on lunate, predisposing it to injury thru repetitive microtrauma
Anatomic
- Shape of lunate
- Type I – proximal ulnar apex + ulnar -ve
- Type II – square lunate + ulnar neutral
- Type III – rectangular lunate + ulnar +ve
- Flattened radial articulation
- Type of vasc supply – normally palmar & dorsal
- If single supply – ↑ risk
- Y – 60%, I – 30%, X – 10%
- ∞ negative ulnar variance & cerebral palsy (Apley’s).
- lunate dislocations often do not result in AVN b/c disloc is palmar & vasc inflow often persists thru a palmar capsular flap
- No surgical procedure has conclusively shown to prevent progression
Presentation
- Wrist pain (radiates up forearm)
- Limited ROM. ↓ DF & PF but preserved rotation
- Synovitis & swelling
- Tenderness localized to lunate (especially dorsally)
- ↓Grip strength
Plain radiographs – ulnar variance
- PA views with wrist in neutral rotation
- Ulna looks relatively longer if XRay in supination
Staging – Radiographic (Lichtman)
- 1 – no visible Δ in lunate, Δ seen on MRI & Bone Scan.
- 2 – sclerosis/↑ density
- 3A – collapse of lunate BUT no carpal collapse
- 3B – carpal collapse. fixed scaphoid flexion (ring sign)
- 4 – degenerative arthritis of adjacent intercarpal jts
MRI findings
T1 – uniform ↓ in signal intensity
T2 – low signal unless revascularization is occurring, in which case there will be increased signal
Management
- If stage 1 – immobilise & NSAIDs
- Stage 2-3A – if ulnar neg à jt leveling procedure :
- Radial shortening osteotomy
- Ulnar lengthening (higher rate nonunion)
- Capitate shortening
- Stage 2-3A – if ulnar neutral/+ve
- Direct revascularization
- Pedicled vascularised graft from distal radius + PQ
- Dorsal 2nd MC artery placed into drill hole on lunate
- The greatest chance of success in stage II.
- Vascularized transfers of pisiform
- Transfers of distal radius on pedicle of PQ
- Transfers of brs of 1st, 2nd or 3rd dorsal MC Art
- Indirect revascularization procedures (pressure relieving procedures
- Radial closing wedge osteotomy
- Radial dome osteotomy
- Capitate shortening with or without capito-hamate fusion (Almquist procedure)
- Use an ex fix to unload the lunate
- Stage 3B – Options :
- Correction of scaphoid flexion (to its normal position of 45° flexion) followed by STT or SC fusion
- Joint leveling procedures
- Proximal row carpectomy – capitate then articulates with distal radius
- Limited intercarpal fusion (STT)
- Wrist denervation
Options 1 & 2 may be combined with excision of lunate; the resulting defect may be filled with a palmaris longus tendon or titanium implant
- Stage 4 – Options :
- Proximal row carpectomy (if no arthritis of capitate)
- Wrist fusion / limited intercarpal fusion
- Wrist denervation
Carpal height
- Carpal height (from base middle finger MC to distal radial articular surface) divided by length of 3rd MC
- Normal = 0.54 ± 0.03
Summary
- Stage I – Splint
- Stage II or IIIa – ascertain ulnar variance
If ulnar minus – joint leveling procedure - radial shortening
If ulnar neutral or positive – revascularization or capitate shortening ± capitohamate fusion
- Stage IIIb - STT/SC fusion / Proximal row carpectomy / joint leveling
- Stage IV – Proximal row carpectomy /wrist arthrodesis/ denervation
