Table 4: Pearson’s correlation coefficients between BMI and the outcome measures before surgery, at 6 months and 1 year after surgery and between BMI and the change scores.

OKS SF12 (PCS) SF12 (MCS) Pre-op. 0.271* −0.086 −0.101 6 months 0.115 0.143 −0.139 1 year 0.072 −0.206 −0.041 Pre-6m −0.082 −0.117 −0.015 Pre-1yr −0.194 −0.159 −0.068

* P < 0.01, PCS: physical component summary of the SF12, and MCS: mental component summary of SF12.