Four Corner Fusion is a surgical procedure used to treat carpal instability and arthritis. It involves fusing together the four small carpal bones (scaphoid, lunate, triquetrum, and pisiform) through bone preparation, temporary fixation with K-wires, and permanent fixation with a plate and screws. The procedure aims to reduce pain, maintain range of motion and grip strength, and allow activities of daily living. Contraindications include a stiff wrist, radiolunate arthritis, or erosive arthropathy, which may be better treated with proximal row carpectomy.

1. Four Corner Fusion

2. Indications
• post-traumatic or
degenerative mid carpal
bone arthrosis
• carpal instability (SNAC or
SLAC) - Stage 2 and 3
• failed partial arthrodesis

3. Aim
• Reduce pain
• Maintain ROM
• Maintain grip strength
• Maintain activities of daily living (ADL)

4. contraindication for a 4CF
• Stiff wrist
• Radio lunate arthritis
• Erosive arthropathy
Consider Proximal row carpectomy

5. Prerequisites
• normal congruity without degenerative changes between the lunate
fossa of the radius
• At least 40% of ROM in Radio carpal joint
• Good bone stock of 4 bones

6. Complications of implant in 4CF
• Nonunion
• Hardware failure
• Dorsal wrist impingement

7. Approach
• Radially based capsular flap
• allows a wide exposure of the
radiocarpal as well as the
midcarpal joints
• dorsal capsule ligament sparing
• Preserve volar radioscaphocapitate
ligament

8. Bone preparation
• the articular surfaces of the four
bones to be fused must be
decorticated
• bleeding cancellous bone
• down to healthy cancellous bone
• manipulate the lunate in a neutral
position (joystick)
• K Wire temporarily fixes the two
bones
(mini C-arm fluoroscopic),
Midcarpal joint in slight extension - to increase wrist functionality

9. Technique
12 screw holes,
4 cortical screws and 8 TriLock locking screws
reamer to create a recess for the four corner fusion plate

10. Seating recess
• Center the reamer on the proximal
(medially oriented) pole of the hamate
• reamer perpendicularly, create recess
by applying axial pressure
• Ream downward until the plate can be
inserted a little beneath the dorsal
bone surface
• 4 C filled with cancellous bone graft,

11. Plate alignment and fixation
• 3 holes (1 fixation hole, 2 locking holes) per
bone to be fused
• at least 2 holes per carpal bone
• correctly aligned
• fixation hole through one of the lower plate
holes 1.6mm drill
• gold cortical screw Ø 2.0 mm (lag screw)
• Remove the K-wires
• blue TriLock locking screws Ø 2.0 mm are
inserted through the upper plate holes
at least 1 locking screw per carpal bone

12. Results
• both procedures give improvements in pain and subjective outcome
• PRC may provide better postoperative range of movement and lacks the potential complications
• risk of subsequent osteoarthritis is significantly higher in PRC
• Grip strength, pain relief and subjective outcomes are similar in both treatment groups.
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