Leppilahti 2001.

Methods	Randomised controlled trial. Pre‐specified sample size calculation not reported. Overall validity of results: high risk of bias.
Participants	26 participants (28 elbows); mean duration of symptoms was 23 months (range 5 to 60 months). Decompression of posterior interosseous nerve (PIN group): 13 participants, 6 men and 7 women (14 elbows), mean age 42 years (range 33 to 50 years), 12 participants were manual workers who performed repetitive activities with their upper extremities. Lengthening of the extensor carpi radialis brevis (ECRB group): 14 participants, 7 men and 7 women (14 elbows), mean age 41 years (range 30 to 52 years), 11 participants were manual workers. Inclusion criteria: pain on activity on the lateral aspect of the elbow and local tenderness, previous conservative treatment (including physiotherapy, corticosteroid injections, splint or forearm support band) that did not result in continuous pain relief. Exclusion criteria: none reported.
Interventions	Group 1, 'PIN group' (14 elbows): anterolateral longitudinal incision to expose the radial nerve in the groove between the brachioradial and brachial muscles, PIN exposed by distal dissection and decompressed at the arcade of Frohse by a 1‐2cm incision through the supinator muscle, then all sites of decompression along the PIN were released Group 2, 'ECRB group' (14 elbows): 4cm incision over the dorsilateral aspect of the forearm, proximal to where the thumb extensors obliquely cross the radius, Z‐shaped tenotomy dissection of the tendon of the ECRB muscle, and insertion of a suture to hold the ends loosely together. In both groups, surgery was performed under tourniquet control.
Outcomes	Assessed at 22 to 48 months (mean 31 months) following surgery: 1) function: mean (and range) postoperative grip strength in both hands; 2) pain relief: 4 point ordinal scale as 'excellent'‐ upper limb completely relieved of the pre‐operative symptoms; 'good'‐ slight periodic pain; 'fair'‐ pain provoked by activity (but better than pre‐surgery); 'poor'‐ no improvement in pain or activity tolerance; 3) proportion of participants with lateral elbow pain on activity; 4) proportion of participants with tenderness on palpation at the lateral epicondyle of the humerus, and palpation over the PIN on the volar side of the elbow; 5) rate of re‐operation; 6) post‐operative complications; 7) time to return to work.
Sources of funding	Not reported
Notes	We did not extract pain relief data as the data presented were not easily amenable to meta‐analysis (short ordinal scale with no logical dichotomization point); we also did not extract mean grip strength, or time to return to work from the trial, as only range was provided as a measure of variance, and thus we could not estimate standard deviation in a robust way; the only data we could extract was the proportion of participants with lateral elbow pain on activity or with palpation. The authors report that there were no adverse events in their study.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	Comment: not described
Allocation concealment?	Unclear risk	Comment: not reported
Blinding? All outcomes	High risk	Comment: unlikely; surgeon unblinded (single surgeon performed all procedures); unclear if lack of blinding of outcome assessor would bias toward one intervention
Incomplete outcome data addressed? All outcomes	Low risk	Comment: all randomised participants provided outcome data
Free of selective reporting?	High risk	Comment: the trial authors measured time to return to work, but did not report the mean (and SD), only a P value at one time point
Free of other bias?	Low risk