Schmidt 2014.

Methods	RCT
Participants	54 people (mean age 49.3 years, range 20 to 74; 32 males, 22 females) with 56 clinical, electrophysiological, and ultrasonographic confirmed cases of ulnar nerve neuropathy Exclusion criteria: contraindications for general anaesthesia, post‐traumatic cubital tunnel syndrome with bony deformity of the elbow, previous surgery of the affected ulnar nerve, severe nerve luxation Investigators appear to have randomised arms rather than participants.
Interventions	Endoscopic decompression (29 arms), open decompression (27 arms)
Outcomes	Clinical outcomes: modified Bishop scale 2‐point discrimination numeric analogue scale (NAS) Electrophysiological outcome: motor nerve conduction velocity
Conflicts of interest	Report states: "The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article."
Study funding	No information provided.
Notes	Operations were performed between October 2008 and April 2011. Single centre in Germany. Early follow‐up at mean of 16 weeks and long‐term follow‐up at mean of 16.8 months
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The randomization process was performed as a simple randomization without restrictions by drawing a trial envelope by the surgeon directly before each surgery started"
Allocation concealment (selection bias)	Unclear risk	Quote: "The randomization process was performed as a simple randomization without restrictions by drawing a trial envelope by the surgeon directly before each surgery started"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Participants were blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinded examiners performed the postoperative evaluation and statistical analysis.
Incomplete outcome data (attrition bias) Clinical or neurophysiological outcome	Low risk	3 participants were free of symptoms at follow‐up and declined further electrophysiological examination.
Selective reporting (reporting bias)	Low risk	Results from all the outcome measures are reported.
Other bias	Low risk	The sample size was not calculated. The authors do not specify if the study was designed to be a non‐inferiority or a superiority trial. It is unclear whether any adjustment was made for the 2 bilateral cases (3.7%), but unlikely to have an important effect.