Contents
- Introduction
- Position of patient
- Landmarks and incision
- Internervous plane
- Superficial dissection
- Deep dissection
- Dangers
- How to enlarge the approach
- Figures
Introduction
Indications
- Decompression of median nerve.
- Flexor tendon synovectomy.
- Carpal tunnel tumor excision.
- Carpal tunnel nerve and tendon repair.
- Drainage of sepsis tracking up from the mid-palmer space.
- ORIF of fxs and dislocations of distal radius and carpus.
Position of patient
- Place the patient supine on the operating table, supinate and place the arm on an armboard.
- Apply a tourniquet after exsanguinating the arm.
Landmarks and incision
Landmarks
- The thenar crease runs around the base of the thenar eminence.
- The transverse skin crease of the wrist overlies the wrist joint.
- The tendon of the palmaris longus muscle bisects the anterior aspect of the wrist easy to palpate in the distal forearm if the patient is instructed to pinch the fingers together and flex the wrist.
Incision
- Begin 4 cm distal to the flexion crease, remaining just to the ulnar side of the thenar crease.
- Make an ulnar curve so you do not cross perpendicular to the flexion crease; also helps protect the palmer cutaneous branch.
- End 3 cm proximal to the flexion crease.
Internervous plane
- No internervous plane, the approach is a true anatomic dissection.
Superficial dissection
- Incise skin flaps and fat
- Section fibers of the superficial palmar fascia in line with the incision.
- Retract curved flaps medially to expose insertion of the PL into the flexor retinaculum.
- Retract the PL tendon toward the ulna to expose the median nerve under the PL and FCR.
- Pass a blunt object between the median nerve and retinaculum.
- Incise the entire length of the retinaculum on ulnar side of the nerve distally and proximaly.
Deep dissection
- Identify the motor branch of the median nerve, which usually arises from the anterolateral side of the median nerve just as the nerve emerges from the carpal tunnel.
- Mobilize the median nerve and retract it radially to avoid stretching the motor branch.
- Mobilize and retract the flexor tendons
- Incise the base of the carpal tunnel
Dangers
Palmar cutaneous branch of the median nerve
- Danger occurs if the skin incision is not angled to the ulnar side of the forearm, as it arises 5 cm proximal to the wrist joint and runs down along the ulnar side of the tendon of the flexor carpi radialis muscle before crossing the flexor retinaculum.
Motor branch of the median nerve to the thenar muscles
- The nerve exhibits considerable anatomic variation.
- The risk is minimized if the incision is made into the carpal tunnel on the ulnar side of the median nerve.
Superficial palmar arch
- Crosses the palm at the level of the distal end of the outstretched thumb.
- Blind slitting of the flexor retinaculum may damage this arterial arcade; no danger if the flexor retinaculum is cut carefully under direct observation for its entire length.
How to enlarge the approach
Proximally
- To further expose the median nerve, extend the incision up to the middle of the arm.
- Incise the deep fascia between the PL and FCR.
- Retract the PL and FCR to expose the FDS.
- The median nerve adheres to the deep surface of the FDS.
Distally
- The skin incision can be extended into a volar zigzag approach for any of the fingers, providing complete exposure of all the palmar structures.
Figures
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