Table 4.

Summarised themes for responses to open-ended questions.

	N (%)
Participants' general opinions towards placebo surgery in clinical trials
Do not see any value/benefit in placebo surgery	15 (27.8)
Have concerns about placebo surgery (e.g. ethical, costs)	11 (20.4)
Have not formed an opinion yet (e.g. due to lack of information)	12 (22.2)
Understand the importance and benefits of placebo surgery	12 (22.2)
Other	4 (7.4)
Reasons participants gave for responding no or maybe to participation in a randomised placebo-controlled surgical trial
Have concerns about the risks and benefits of placebo surgery	12 (27.9)
Have a lack of information or understanding about placebo surgery	2 (4.7)
Have unmodifiable personal reasons against placebo surgery	7 (16.3)
Have a clear preference for treatment	6 (13.6)
Have financial and/or ethical concerns on the cost of the surgery	5 (11.6)
Understand the importance of placebo surgery in clinical trials and/or want to contribute to research	3 (7.0)
Other (disagree with any kind of surgery or answers not interpretable)	8 (18.6)
Factors that would increase willingness to participate in a placebo-controlled trial
More information about procedure and/or study	6 (14.6)
Certainty and reassurance of good outcome	8 (19.5)
Free choice of which treatment received	5 (12.2)
Pain levels or functional status	2 (4.9)
Advantages to participation	4 (9.8)
Support of clinical evidence	1 (2.4)
Nothing/unlikely to improve willingness	11 (26.8)
Other	4 (9.8)
Reasons participants gave against waiting 6 months for surgery (if allocated to placebo group)
Do not see the value of randomised trials or only want surgery	9 (22.5%)
Need reassurance about positive outcomes after placebo surgery	5 (12.5%)
Level of pain and functional status	9 (22.5%)
Require immediate treatment due to personal reasons (e.g. age, work)	11 (27.5%)
Require more information	1 (2.5%)
Other	5 (12.5%)