Recurrent & Revision Carpal Tunnel Syndrome (and Endoscopic Release)

Before the knife

• Obtain and read the original operative note. It states which approach was used, what was divided, what was seen and whether anything unexpected was found. A note describing a limited open or endoscopic release with no comment on the distal ligament edge raises the probability of an incomplete division; a note recording a normal-looking, fully decompressed nerve pushes the diagnosis back towards a mimic.
• Consent for the specific findings. Numbness in the palmar cutaneous distribution, a slower and initially more painful recovery than the first operation, the possibility that a flap will be raised, and the honest position that revision relieves symptoms less predictably than a primary release.
• Anaesthesia and tourniquet. Regional or general with an arm tourniquet; the field must be bloodless, because in scar the nerve is identified by texture and pattern rather than by colour contrast.

The incision

Extend the previous palmar incision proximally, keeping it ulnar to the thenar crease and in line with the radial border of the ring finger. Cross the wrist crease obliquely towards the ulnar side rather than as a straight transverse line - a straight line across a flexion crease contracts, and a radially placed extension runs directly onto the palmar cutaneous branch between palmaris longus and flexor carpi radialis. The proximal extension is not optional in a revision; it is what creates the unscarred territory the next step depends on.

Start proximal, in tissue nobody has operated on

This is the single principle that makes revision surgery safe. Identify the median nerve in the distal forearm proximal to the old scar, where the planes are normal and the nerve lies in its expected position ulnar to flexor carpi radialis and deep to palmaris longus. Only once it is in view and controlled do you trace it distally into the scar, keeping the nerve itself as the guide.

Beginning the dissection in the middle of the scar inverts this: the nerve is tethered, displaced and surrounded by tissue with no reliable plane, and there is nothing to tell you where it is until you have cut it. Every element of the revision - the extended incision, the open approach, the bloodless field - exists to make a proximal-to-distal dissection possible.

Keep the dissection and the ligament division on the ulnar side of the canal, away from the recurrent motor branch, which leaves the nerve radially. In a revision a sub- or transligamentous Lanz variant may already have been tethered or partially divided at the index operation, so treat every revision as though a variant is present until the branch has been seen for itself.

Complete the decompression

• Proximally: divide the distal antebrachial fascia under direct vision, continuing several centimetres into the forearm. This is one of the two classic sites of under-division, and it cannot be reached blindly through a palmar incision.
• Distally: divide the transverse carpal ligament to its true distal edge, where the palmar fat pad appears. Confirm completeness by passing a blunt instrument along the canal and seeing that nothing tethers it, rather than by assuming the ligament ended where the previous incision did. The superficial palmar arch lies immediately beyond, which is why this step is done with the eye and not the finger.
• External neurolysis only: free the epineurium from perineural scar circumferentially. Do not perform an internal neurolysis or epineurotomy - dissecting between fascicles adds intraneural scarring and denervation risk without improving outcome.
• Assess the bed. If the nerve now sits in a smooth, well-vascularised bed, the release alone is enough. If it lies on bare, scarred, poorly vascularised tissue - or has been circumferentially neurolysed - it will re-adhere to that same surface, and coverage is indicated.

The workhorse coverage flap

Raised through the same incision, so no second wound is needed.

1. Develop the ulnar skin flap and expose the fat of the hypothenar eminence.
2. Raise the fat pad ulnarly based, keeping intact the perforating vessels entering it from the ulnar artery - this is a vascularised flap, not a fat graft, and that is the point of it.
3. Protect the ulnar neurovascular bundle in Guyon's canal, which lies deep at the base of the flap. This is the flap's one real hazard, and it is the reason the base is developed under vision rather than by blunt sweeping.
4. Transpose it radially across the median nerve and suture its free edge to the radial edge of the divided ligament or to the deep radial soft tissue, so the nerve lies under healthy vascularised fat rather than against scar.

Alternatives when the hypothenar fat is unusable: a synovial flap from the flexor tendons, a pronator quadratus or adipofascial flap, or a vein wrap. A systematic review and meta-analysis of 26 studies of autologous nerve coverage found the hypothenar fat pad and synovial flaps were the only two techniques comparable head-to-head, with more patients achieving complete relief of symptoms, satisfaction and pain improvement in the hypothenar fat pad group - which is why it is the default choice rather than merely one option on a list.

Rehabilitation is part of the operation

The problem being treated in recurrent disease is scar, so the post-operative plan is aimed at scar, not at rest.

• Early active finger and median-nerve gliding, started within the first few days, to keep the nerve moving within its new bed rather than becoming fixed to it. Prolonged splinting works against the whole purpose of a neurolysis.
• Scar management - massage and desensitisation - from wound healing, because scar tenderness and pillar pain are more prominent after revision than after a primary release.
• Expect a slower curve. Counsel at the outset that early pain is higher and the recovery longer than after the first operation, so that a normal revision course is not mistaken by the patient for a second failure.