Rationale

In order to decide upon the best surgical treatment of CTS, it is important to know when nonoperative treatment is unlikely to be successful and therefore surgery is indicated.

Clinical comment

In patients with severe CTS in which there is clear wasting of the thenar muscles (specifically abductor pollicis brevis) and objective sensory changes such as a decrease in two‐point discrimination, the diagnosis of CTS is typically clear on the basis of clinical examination alone. However, many, and in fact the majority of, patients do not exhibit these clinical features.

Available literature and quality of the evidence

In a highly rigorous process, the American Academy of Orthopaedic Surgeons (AAOS) published an evidence‐based set of guidelines for CTS (level IV evidence).¹

Findings

The AAOS concluded that there was strong evidence that thenar atrophy “is strongly associated with ruling‐in carpal tunnel syndrome”; they also concluded that common clinical signs such as Phalen’s sign – when used in isolation – “has a poor or weak association with ruling‐in or ruling‐out carpal tunnel syndrome.” Conversely, they concluded that “limited evidence supports that a hand‐held nerve conduction study (NCS) device” be used to diagnose CTS. It is understood that a “hand‐held NCS device” meant an office‐based device used by surgeons who were not using American Association of Electrodiagnostic Medicine (AAEM) criteria for the diagnosis of CTS versus formal electrodiagnostic testing. In the body of the AAOS review,¹ the authors articulated this, and in an AAOS review on the diagnosis of CTS they recommended formal NCS be performed before surgical intervention (level II).²

The AAEM performed a meta‐analysis of prospective studies which compared independently gathered clinical data with rigorously performed electrodiagnostic testing.³ They concluded that “median sensory and motor NCS are valid and reproducible clinical laboratory studies that confirm a clinical diagnosis of CTS with a high degree of sensitivity and specificity.” Although this level I evidence suggests that NCS is useful for diagnosing CTS, it does not address whether NCS is necessary for patients prior to carpal tunnel surgery.

Another way to examine this question is to ask whether NCS can predict outcomes after CTR and particularly whether patients with normal NCS benefit from CTR. The evidence in this question is of relatively low quality and contradictory. Longstaff et al. as well as Glowacki et al. found that clinical outcomes after CTR did not correlate with preoperative NCS,⁴,⁵ whereas Bland reviewed a large (n = 1268) group of patients and found that patients with either normal or severe findings on NCS had a higher rate of surgical failure (all level IV).⁶

The evidence to support preoperative NCS prior to carpal tunnel surgery is contradictory. There is good evidence to support the ability of NCS to diagnose CTS, but it is unclear whether the addition of NCS to clinical examination is necessary in all circumstances. Interestingly, when presented with scenarios of patients with a low or medium probability of CTS (on clinical testing tools such as the CTS‐6), participants in the AAOS appropriate use guidelines development supported the use of NCS to further investigate patients as appropriate.⁷

Resolution of clinical scenario

• NCS are sensitive and specific for the diagnosis of CTS.
  
• NCS are likely unnecessary in patients with advanced findings of CTS, such as thenar wasting or objective sensory deficits, but can differentiate other neurological pathologies, and assist in postoperative management when outcomes are poor or unexpected.
  
• NCS are likely useful in patients with mild clinical findings or atypical presentations.

Rationale

ECTR has been championed as a less invasive method of releasing the transverse carpal ligament which allows for an earlier return to work and normal activities of daily living (ADLs) relative to OCTR. Conversely, opponents of ECTR feel that complications may be more common.