Heckman 1994.

Methods	Randomised, placebo‐controlled study
Participants	Setting: University of Texas Health Science Centre, USA. Size: 97 patients were enrolled. Of the 48 patients in the test group, 11 violated the protocol and 4 were lost to follow‐up, leaving 33 patients completing the study. Of the 49 patients in the control group, 6 violated the protocol and 9 were lost to follow‐up, leaving 34 patients completing the study. Baseline characteristics: mean age was 36 years, with 25 males and 8 females in the intervention group, and mean age 31 years with 29 males to 5 females in the control group. Inclusion criteria: skeletally mature men and non‐pregnant women aged less than 76 years with closed or grade I open, transverse or short oblique/spiral, fractures of the tibial diaphysis that could be treated with closed reduction and cast immobilisation. Exclusion criteria: post‐reduction findings of long oblique/spiral fracture, length of fracture line greater than twice the diameter of the diaphysis; fracture displacement greater than 50%; fracture gap greater than 0.5 cm or persistent shortening; persistent angulation greater than 10 degrees; metaphyseal fracture; large butterfly fragment; pathological fracture; comminution; participant inability to comply with trial procedures; current prescription of NSAID, calcium channel blockers, bisphosphonates; history of thrombophlebitis, vascular insufficiency, alcoholism or nutritional deficiency.
Interventions	Participants were treated with closed reduction and above‐knee casting. An alignment window was placed in the cast at the level of the fracture over the antero‐medial aspect of the leg. Reduction of the casting to a below‐knee cast, any subsequent splintage and weight bearing status was at the discretion of the clinician. Test: participants underwent ultrasound treatment for 20 minutes each day from the second to twentieth week, or earlier if the clinician believed there was adequate evidence of union. The ultrasound signal was composed of a 200 µs burst of 1.5 MHz sine waves, with a repetition rate of 1 kHz and a spatial average intensity of 30 mW/cm². Control: participants in the control group were given a similar treatment regimen but had an externally similar sham machine instead.
Outcomes	Follow‐up schedule: plain radiographs at 4, 6, 8, 10, 12, 14, 20, 33 and 52 weeks. Clinical examination at times of cast change and at the time of union. Outcomes: time to combined radiographic and clinical union.
Notes	The weight bearing status of the patients was strictly described initially but subsequently handed over to the discretion of the treating clinician part way through the trial. It was confirmed in personal communication with James Heckman that there was no time to union data on participants who violated protocol. Cook 1997 describes a subgroup analysis of the study by Heckman 1994. Smoking status was collected prospectively during the study for half the participants and retrospectively for the other half. There were 33 participants in the active group and 34 in the control group. These numbers correspond with the numbers of participants that successfully completed the study by Heckman 1994. Of these smoking status was not determined in 7 participants due to loss to follow‐up.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "...predetermined computer generated code." Comment: Likely to have been a robust method.
Allocation concealment (selection bias)	Low risk	Quote: "...the patients were randomized, in groups of four, at each study site..." Comment: It is likely that the sequence was held centrally and allocations were given to the distant study centres.
Blinding (performance bias and detection bias) Objective measures	Low risk	Quote: "The active and placebo devices were identical in every way..." Comment: Likely to have been a robust method.
Incomplete outcome data (attrition bias) Objective measures	Unclear risk	Quote: "...patients who adhered to the study protocol ... inferences were drawn" Only data from 67 fractures were presented, which represents a loss to follow‐up of 31%. (From JDH: 13 lost to follow‐up, 17 did not present in a timely manner so only certainty is ultimate successful union, no time to event data available.)
Selective reporting (reporting bias)	Unclear risk	No protocol available.
Other bias	High risk	Quote: "Ninety‐six patients, who had ... ninety‐seven fractures..." Comment: Per protocol analysis only. Also, there was no adjustment for recruiting related fractures
Selection bias (imbalance in baseline characteristics)	Unclear risk	Smoking status is not reported as part of the baseline characteristics of the participants.