Karen E Burtt, Ido Badash, Brian Wu＊

Keck School of Medicine of the University of Southern California, Los Angeles, California, USA

Cubital tunnel syndrome (CTS), characterized by compression or irritation of the ulnar nerve as it runs under the medial epicondyle of the humerus, is the second most common entrapment neuropathy of the upper extremity.1A number of surgical options exist for treating CTS when nonoperative options have failed or neurologic deficits exist. These include simple decompression, which involves lysis of adhesions to free the ulnar nerve, and anterior transposition, in which Osborne's ligament is cut and the ulnar nerve is moved out of the tunnel to a more anterior location in which it experiences less tension during arm flexion. Peer reviewed studies investigating these surgical options have found similar outcomes.2-4Consequently,the choice of surgical procedure is often a matter of physician and patient preference. When anterior transposition is performed, the nerve and associated vessels may be placed in a subcutaneous or submuscular location. No significant difference in clinically relevant improvement in function from baseline has been found between these two options of nerve placement.5Thus, the study designed by Liu et al.,6which aims to establish quantitative and objective data on outcomes of the aforementioned surgical options, will produce clinical data to assist surgeons in optimizing their approach to patients with cubital tunnel syndrome.

The study by Liu et al. has a number of strengths which may result in clinically and statistically significant data not elucidated by prior investigations. Inclusion and exclusion criteria are extensively documented, and interventions are detailed and consistent with prior literature.7-9Randomization of patients with blinding of outcome assessors and statisticians will reduce biases in selection and reporting. Outcomes are well defined and extensive;use of several criteria for outcome measures (muscle strength,sensation, EMG, pain, and incision complications) will allow for a multifaceted investigation of patient outcomes. Preliminary data shows promising outcomes overall; it will be valuable to determine if significant data arises out of a larger sample size.

Several aspects of the study protocol may be improved. Patients and implementers are not blinded, which could introduce reporting bias. Moreover, it is unclear how many participants the study seeks to enroll. Based on the likelihood of negative results given their prevalence in the literature, care must be taken to include a sample size that is large enough to establish an acceptable level of power to minimize type II error, and a power analysis should be performed and reported. Furthermore, the choice to use broad inclusion criteria may mask significant differences in outcomes present between specific populations. For example, prior studies have found duration of symptoms and advanced age to be negatively correlated with outcomes.10,11Moderate and severe cubital tunnel syndrome have also previously shown differences in efficacy of surgical options.12Thus, while the authors plan to distribute patients with moderate and severe symptomatology non-discriminately, this may obscure significant results. It may be preferential to randomize patients into groups, such as moderate and severe CTS, in order to highlight differences that may be present between these populations. Finally, one of the study’s exclusion criteria is unsatisfying efficacy of the procedure necessitating other therapies. This criterion may bias results since patients with poor outcomes will be removed from the study.

While the study design addresses that adverse events will be investigated, the authors do not define which specific adverse events will be recorded and included in the study. Common surgical complications, including symptom recurrence, procedure revision, and limited work capacity, would be beneficial for the authors to compare between procedures. Validated functional outcome scales assessing duration of limited work capacity, including the Disability of the Arm, Shoulder, and Hand (DASH)questionnaire or Bishop-Kleinman rating, may be useful and have been utilized in other studies investigating surgical treatment of cubital tunnel syndrome.13Lastly, the authors may wish to follow the patients for greater than 6 months postoperatively in order to observe long-term outcomes of these procedures. For example, grip strength has been found to improve up to a year after decompression.14

CTS is a debilitating condition without clear evidence for a preferred surgical option. Overall, the study design of Liu et al.’s clinical trial is promising, and the results have the potential to impact the way in which hand surgeons approach cubital tunnel syndrome. If the considerations discussed in this commentary are addressed, this study could provide valuable evidence giving preference to one surgical modality.

Author contributions

All authors contributed to the concept of the manuscript. KEB and IB contributed to manuscript preparation, and all authors worked on manuscript editing, review and approval. All authors took responsibility for the integrity of the work as a whole from inception to the published article.

Conflicts of interest

None declared.

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Checked twice by iThenticate.

Peer review

Externally peer reviewed.

Open access statement

This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License,which allows others to remix, tweak, and build upon the work noncommercially, as long as the author is credited and the new creations are licensed under the identical terms.

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