The Carpal Tunnel

Attachments of flexor retinaculum (palmaris longus inserts into it; proximal edge is at distal wrist crease)

1. tubercle of Scaphoid
2. ridge of Trapezium
3. Hook of hamate
4. Pisiform

Superficial:

• Ulnar nerve and artery (runs in Guyon's canal)

Deep structures:

• 4FDS, 4FDP, FPL
• Median nerve
• (Flexor carpi radialis runs underneath the flexor retinaculum but lies outside the carpal tunnel

Causes

1. Idiopathic
2. Pregnancy
3. Obesity
4. Trauma
5. Systemic disease: myxodema, rheumatoid arthritis, acromegaly, diabetes

Management

1. History
   • Risk factors (above)
2. Examination
   • Tinels tap test positive
   • Phalen's test
3. Investigations
   • Nerve conduction studies
4. Surgical decompression

Surgical decompression procedure

1. Informed consent, mark correct side
2. LA / Regional / GA
3. Limb exsanguinated + tourniquet, note inflation time
4. Exposure of flexor retinaculum
   • 3cm incision from distal flexor crease (from line ring finger ------)
   • expose flexor retinaculum
5.  Cut retinaculum
   • Place MacDonald's elevator underneath retinaculum
   • Incise longitudinally down to instrument
   • Median nerve identified (paler in colour, has visible blood vessels called vasa vasorum on surface)
   • Protect motor branch to thenar muscles / palmar cutaneous branch that provides sensation to skin [by staying medially...]
6. Close skin with interrupted nylon sutures
7. Apply light splint