All participants received the treatments as allocated. Of these participants,146 (98.6%) completed the follow-up at 1 month for the primary outcome measures of pain and disability and for the secondary outcome measure of quality of life.
However, 4 participants (5.5%) in the McKenzie group and 8 participants (10.8%) in the Back School group could not be followed up for the secondary outcome measure of trunk flexion range of motion at 1 month due to an inability to attend the clinic. All participants completed
the 3-month follow-up, and only one loss to follow-up in the Back School group occurred for all outcomes at 6 months (ie, 99.3% followup).