UNDER Study: Ulnar Nerve Decompression Endoscopic Randomisation Study

Background: Cubital tunnel syndrome is a compression neuropathy of the ulnar nerve at the elbow. Surgical decompression is recommended for persistent and severe symptoms. Surgery may be performed using either open or endoscopic techniques. The open technique is widely used in clinical practice and has a low rate of complications and of symptom recurrence. Patients may recover more quickly after endoscopic surgery. However, the technique is used infrequently and there is a higher rate of complications. Data on comparative efficacy for the two techniques is limited. A comparative study requires wider surgeon training in and adoption of the endoscopic technique.

Aim: To train surgeons in endoscopic cubital tunnel surgery and then to conduct a randomized controlled trial comparing endoscopic and open decompression techniques in the surgical management of cubital tunnel syndrome.

Objectives: To ascertain the relative patient reported clinical efficacy of endoscopic and open cubital tunnel decompression at 3 months measured by the PRUNE score using a two arm RCT with a parallel economic evaluation determining cost effectiveness.

Methods: The study has 2 phases. In phase 1, 30 hand and upper limb surgeons from up to 20 hospitals expressing interest in becoming investigators in the UNDER Study will be invited to attend a cadaveric workshop and trained in the endoscopic cubital tunnel decompression technique. Satisfactory completion of training will allow progression to the training cohort whereby patients with cubital tunnel syndrome considered for primary decompression surgery will be recruited and consented for the study. Each surgeon will perform up to 5 endoscopic decompression cubital tunnel procedures and will be eligible for transition to phase 2 depending on previous experience, satisfactory attainment of defined competencies and capture of 6 week follow up data on study participants. Data from the phase 1 study will be used to establish the learning curve and complications for the endoscopic procedure. During phase 2, 334 eligible participants will be recruited at up to 20 hospitals in the United Kingdom and randomized to either the endoscopic or open decompression technique. The primary outcome measure is the change in PRUNE score measured at baseline, 3 and 6 months. Secondary outcomes measures include motor function in the ulnar nerve innervated muscles measured using the British Medical Research Council scale, elbow range of motion, scar cosmesis measured using the POSAS v2, return to work, complications and EuroQol EQ-5D-5L. Parallel economic evaluation will determine the cost effectiveness of the endoscopic and open cubital tunnel decompression procedures.