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1st CMC Arthroplasty

intermediate Level

Primary Indication

Symptomatic thumb carpometacarpal (CMC) osteoarthritis (Eaton Stage II-IV) refractory to conservative treatment (splinting, NSAIDs, injections), with persistent pain limiting function

Danger Structures

  • Radial artery (in anatomical snuffbox)
  • Superficial radial nerve branches
  • FCR tendon
  • Thenar motor branch of median nerve
  • APL tendon
  • Trapezoid (preserve it)

Visual Atlas

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Step-by-Step Technique

1

Position supine with arm on hand table, apply forearm tourniquet

Surgeon's Tip
EXAM KEY: Volar approach gives better access to FCR for LRTI. Dorsal approach preferred by some for visualization.
Danger Zone
  • Radial artery in snuffbox (dorsal)
  • Palmar cutaneous branch median nerve (volar)
2

For volar approach: make incision along thenar crease from CMC joint to wrist crease

Surgeon's Tip
EXAM KEY: Volar approach follows thenar crease - excellent cosmesis and direct access to FCR
Danger Zone
  • Thenar motor branch of median nerve
  • Radial artery
3

Identify and protect superficial radial nerve branches and radial artery

Surgeon's Tip
EXAM KEY: Radial artery courses through snuffbox - protect throughout procedure
Danger Zone
  • Radial artery injury
  • Superficial radial nerve injury
4

Incise capsule longitudinally, expose CMC joint and trapezium

Surgeon's Tip
EXAM KEY: Full trapezium exposure needed for complete excision
Danger Zone
  • Incomplete capsule incision limiting exposure
  • Cartilage damage
5

Perform complete trapeziectomy - remove entire trapezium in one piece or piecemeal

Surgeon's Tip
EXAM KEY: Complete excision essential - use rongeur, osteotome, or sagittal saw. Protect surrounding structures.
Danger Zone
  • Trapezoid damage
  • Scaphoid cartilage damage
  • FCR tendon injury at base
6

Protect FCR tendon during excision - it runs in groove on trapezium

Surgeon's Tip
EXAM KEY: FCR passes in osteofibrous tunnel on volar trapezium - will be needed if doing LRTI
Danger Zone
  • FCR laceration (catastrophic if planning LRTI)
  • Loss of FCR for reconstruction
7

Ensure complete trapezium removal - no residual fragments that could cause impingement

Surgeon's Tip
EXAM KEY: Palpate and fluoroscopy to confirm complete excision
Danger Zone
  • Residual bone fragments causing pain
  • Incomplete excision
8

Harvest slip of FCR (radial half) through separate incision at wrist crease if not visible

Surgeon's Tip
EXAM KEY: Take radial half of FCR, leave ulnar half attached distally for continued function
Danger Zone
  • Taking entire FCR
  • Inadequate slip length
9

Create drill hole through base of first metacarpal from dorsal to volar

Surgeon's Tip
EXAM KEY: Drill hole should be at CMC joint level - will anchor FCR slip for suspension
Danger Zone
  • Metacarpal fracture
  • Drill hole too small for tendon passage
10

Pass FCR slip through metacarpal tunnel from volar to dorsal

Surgeon's Tip
EXAM KEY: Use tendon passer or suture to pull FCR slip through bone tunnel
Danger Zone
  • Tendon fraying during passage
  • Incomplete passage
11

Tension FCR slip and suture back on itself, creating suspension of MC base

Surgeon's Tip
EXAM KEY: Thumb should sit in appropriate position with adequate tension - not too tight or loose
Danger Zone
  • Incorrect tension (thumb malposition)
  • Suture pull-through
12

Interpose remaining FCR into trapezial space as spacer (anchovy technique)

Surgeon's Tip
EXAM KEY: Roll remaining FCR into ball (anchovy) and suture in trapezial space for cushion
Danger Zone
  • Inadequate interposition material
  • Anchovy extrusion
13

Alternative: simple trapeziectomy without LRTI (similar outcomes in literature)

Surgeon's Tip
EXAM KEY: Evidence shows simple trapeziectomy has similar outcomes to LRTI - less complex procedure
Danger Zone
  • Proximal migration of MC base (minimized with LRTI)
  • None specific if not doing LRTI
14

Close capsule securely, close skin, apply thumb spica splint/cast

Surgeon's Tip
EXAM KEY: Capsular closure adds stability. Thumb spica for 4-6 weeks.
Danger Zone
  • Capsule dehiscence
  • Wound complications
15

Immobilize in thumb spica for 4-6 weeks, then progressive ROM and strengthening

Surgeon's Tip
EXAM KEY: Protected motion at 4-6 weeks, progressive strengthening. Full recovery 3-6 months.
Danger Zone
  • Early failure with aggressive rehab
  • Stiffness with prolonged immobilization