The cumulative percentage of World Health Organization Disability Assessment Schedule (WHODAS) scores at 6 months after surgery. The two dotted lines refer to the 75th centile for the WHODAS score at 6 months after surgery (left-hand dotted line; 16.7%) and the centile (right-hand dotted line; 84th) corresponding to the WHODAS score previously used to define clinically significant disability.³