Received: 12 February 2021
Accepted: 13 December 2021
First Online: 6 January 2022
: The study is approved by the Danish Data Protection Agency Journal no: 18/22336 and permission was granted by the Spine Centre management. According to Danish law, consent is not required when conducting register-based research. Only anonymized data was used, data is presented in aggregate and anonymous form, and study participants were not contacted nor required any active participation. All data was stored according to the GDPR rules on Statistics Denmark’s servers.
: Not applicable, since no individual person’s data was used.
: The authors have no relevant financial or non-financial interests to disclose.