1-year data on patient-reported outcome is enough after surgery for degenerative cervical myelopathy: a cohort study from the Swedish Spine register.

Background and purpose:  Degenerative cervical myelopathy (DCM) is the most common cause of spinal cord dysfunction in adults. Repeated follow-ups after surgery are resource consuming. The aim was to examine whether patient-reported outcome measures (PROMs) change after the first year. The purpose of this study was to investigate whether it is necessary to obtain follow-up data from patients more than 1 year after surgery for DCM.

Methods:  We included individuals treated surgically for DCM in the Swedish Spine registry (Swespine), with available preoperative, 1-, and 2-year PROMs, primarily the European Myelopathy Scale (EMS) and secondarily the Neck Disability Index (NDI), and the European Quality of life Visual Analogue Scale (EQ-VAS). A tertiary analysis included available 5-year data. Median, interquartile range (IQR), and Bland-Altman plots were used to compare PROM data at different follow-up time points.

Results:  642 individuals had baseline, 1-, and 2-year follow-up data, of whom 347 also had 5-year data. EMS was 14 (12-16) preoperative, 15 (12-17) at the 1-year follow-up, and 15 (12-17) at the 2-year follow-up. Corresponding data for NDI was 38 (24-50), 25 (12-42), and 26 (12-42) and for EQ-VAS 50 (30-60), 60 (42-77), and 60 (40-75). Similar findings were seen in individuals who also had 5-year data. Bland-Altman plots indicated good agreement between 1- and 2-year data, and between 1- and 5-year data and were without proportional bias.

Conclusion:  In individuals treated for DCM no clinically meaningful change in PROMs occurred after the 1-year follow-up.