Carpal tunnel release (CTR) is the commonest procedure performed by hand surgeons. Complications and failures have been reported to occur in 3-25% of cases, with up to 12% needing re-exploration.
When it has not worked, how should one approach this problem?
Is it carpal tunnel syndrome?
There are many mimics of carpal tunnel syndrome (CTS) and the following list is by no means exhaustive. One should remember to consider more proximal sites of compression or a more generalised pathology causing the symptoms.
• Cervical radiculopathy
• Thoracic outlet syndrome
• Pronator syndrome
• Brachial neuritis
• Systemic neuropathy (diabetes mellitus, chronic alcoholism)
• Multiple sclerosis
• Peripheral nerve tumour
Careful clinical assessment
The key lies in history and examination. Allow the patient to recount their experience of the index CTR, noting awareness of any pain, difficulties during surgery and duration. I would specifically ask about pre- and post-operative symptoms and establish if there had been any symptom-free period. During examination, pay particular attention to the position of the scar. While I would perform Phalen’s, Durkin compression and scratch-collapse tests, personally I have found Tinel’s sign to be the most useful in localising potential sites of nerve compression. In addition, I would look for evidence of traction neuropathy by asking the patient to make a fist followed by full extension of the wrist and fingers repeatedly (traction Tinel’s sign). Carefully document any sensory loss or muscle weakness.
Do I need to have repeat neurophysiology?
Neurophysiology is a vital aid in the context of failed surgery. Most patients now have pre-operative NCS and I would obtain repeat testing (ideally by the same neurophysiologist) for comparison. If the results are worse, then that is a strong indication for re-exploration. It is reassuring if the results have normalised or improved. However interpret the report carefully.
In successful cases of CTR (i.e. symptoms of CTS have resolved after surgery), the sensory conduction velocity and distal motor latency would improve at as early as one month postoperatively. However the amplitude of motor action potential may worsen. This is probably due to post-surgical oedema locally. By 6 months, all the measurement should improve.
In longer term (i.e. years post CTR), the sensory conduction velocities never quite improve to reach normal values, even in those without any clinical symptoms. In other words there is likely to be residual abnormal sensory NCS following CTR. In contrast, motor latency could improve such that it is within normal values in the long term.
Do I need further imaging?
I have not found it necessary or helpful to request ultrasound or MRI scan unless there is a specific concern with a space-occupying lesion.
Classification
The symptoms can be broadly divided into:
1. Persistent Symptoms
• No or minimal relief after CTR
• Could be due to incomplete release or wrong diagnosis
2. Recurrent Symptoms
• There has to be a defined symptom-free period for at least 3 months (often it is longer)
• Could be due to scar/cicatrix formation and/or tenosynovitis
3. New Symptoms
• Pillar pain
• Nerve injury (median nerve, recurrent motor branch, palmar cutaneous branch, Nerve of Berrettini)
• CRPS
What are the treatment options?
• Repeated decompression/neurolysis
• Nerve repair/grafting
• Neuroma treatment
• Interposition flap or nerve wrap
Would steroid injection help?
A steroid or cortisone injection may predict the success from revision CTR but it is not absolute.
How do you prevent further recurrence?
An interposition flap or nerve wrap theoretically may reduce the risk of further recurrence but a prospective randomised trial is yet to be carried out.
What flaps or wraps are available?
Autologous options (from the patient)
• Fat
• Synovium
• Muscle
• Fascia
• Vein
Off-the-shelf options
• Type I collagen (bovine)
• Small intestine submucosal extracellular matrix (porcine)
Summary
Adequate and thorough decompression of the median nerve in the carpal tunnel is the ultimate surgical aim of CTR. In persistent cases, a repeated decompression is indicated. In recurrent cases, my preference is to perform careful neurolysis of the median nerve, tenosynovectomy and hypothenar fat pad flap. For new symptoms, one has to consider the possibility of nerve injury and treat accordingly.