Kristiansen et al. have previously estimated the rates of surgical treatment for degenerative cervical spine disease in Norway, and reported an increase from 16.9 to 29.4 procedures per 100 000 inhabitants per year from 2008 to 2014 (7). The underlying data consisted of figures from the Norwegian Patient Registry (n = 5 918) that correspond to our data, as well as data from Oslofjordklinikken (n = 593), which treats patients who meet the cost themselves or use private health insurance, and encompassed more than 99 % of the total activity. The proportion of patients who had met the cost themselves or used private health insurance amounted to 9.1 %. We found that the rate of publicly funded treatment had remained stable at an average of 29.6 procedures per 100 000 inhabitants per year until 2018. The Norwegian Registry for Spine Surgery also estimates rates based on data from the Norwegian Patient Registry, and reported a stable rate of approximately 30 surgical procedures per 100 000 inhabitants per year in 2019 and 2020 (11). The total rate of both publicly and privately funded treatment is therefore likely to have increased slightly also after 2014. We had no access to data on privately funded treatment, and Kristiansen et al. did not report whether this proportion remained stable or increased from 2008 to 2014 (7). In any case, a growing population and a higher proportion of older people can be expected to give rise to a continued increase in the number of surgical procedures per year.
The treatment rate also remained stable among residents in the Northern Norway Regional Health Authority area, although at 78 % of the national average. Similar inter-regional differences also prevailed in the period 2008–14 (7). The large annual variations in some regions of residence are likely to be random in areas with few inhabitants. The intra-regional differences were considerable. The average rates were close to the national average in Finnmark and the areas of residence served by the University Hospital of North Norway, but below it among residents in Nordland (56 %) and Helgeland (61 %). We cannot exclude the possibility that there are differences in the prevalence of degenerative cervical spine disease between geographical areas, but we consider this to be a fairly unlikely reason for the lower rates in the Northern Norway Regional Health Authority area. Geographical variations in the access to diagnostic imaging or specialist examination, better provision of non-surgical treatment and long waiting times for surgical treatment can be possible causes. Kristiansen et al. found that residents in areas with low rates of publicly funded treatment also had the lowest rates of surgical procedures paid for by the patients themselves or by private health insurance (7). Privately funded treatment replacing publicly funded treatment is therefore an unlikely reason for the lower rates among residents in the Nordland and Helgeland regions.
Kotkansalo et al. analysed data from nationwide Finnish registries for the years 1999–2015 and found an average rate of 26 surgical procedures for degenerative cervical spine disease per 100 000 inhabitants per year (12). The rate increased from 19 to 35 procedures per 100 000 inhabitants per year from 1999 to 2013 before levelling off. The rate after 2013 was somewhat higher than the one we report for Norway (29.6 procedures per 100 000 inhabitants per year in Norway). The Finnish study included procedures that were paid for by the patients themselves or by private health insurance (A. Kotkansalo, personal communication, 2021). The total rates of publicly and privately funded surgical treatment of degenerative cervical spine disease are therefore likely to have been fairly similar in Norway and Finland. We are not aware of any similar studies from other European countries. The treatment rates in Norway and Finland are far lower than in the United States, where it increased from 51 to 62 surgical procedures per 100 000 inhabitants per year from 2002 to 2009 (13). Lopez et al. analysed data for inhabitants older than 65 years who were insured through Medicare, and reported 85 surgical procedures per 100 000 inhabitants in 2017 (14). There was a large geographical variation from 35 to 190 procedures per 100 000 inhabitants per year, and the increase in the average rate did not level off as it did in Norway and Finland (14).