The two procedure codes in the Common Classification of Medical Procedures corresponding to surgical treatment of SCC make it possible to identify all anonymous standardized discharge summaries from hospital stays—whether in public or private facilities—that include SCC surgery in the Medical Information Systems Program (PMSI):

• AHPA009: Median nerve release in the carpal tunnel via direct approach

• AHPC001: Median nerve release in the carpal tunnel via video-assisted surgery

These procedure codes were selected in collaboration with orthopedic surgeons and the medical information department at Angers University Hospital and private clinics in Nantes and Angers, as part of the pilot network for monitoring musculoskeletal disorders in the Pays de la Loire region.

The geographic criterion used (region/department) is the patient’s place of residence.

Incidence rates (expressed per 100,000 person-years) are calculated for the entire population and for the 20–64 age group, which corresponds to the working-age population.

Departmental and regional incidence rates are standardized to the age structure of the French population for that year and are compared to the national incidence rate using the comparative morbidity figure.

Trend tests were performed to interpret the temporal evolution of the incidence of surgical SCC cases for each sex.

Calculation of incidence rates

The numerators are the numbers of incident cases calculated from PMSI data for the year in question. The denominators, broken down by age and/or sex like the numerators, correspond to estimates of the number of person-years for the year, derived from INSEE’s localized population estimates. Estimates of person-years are calculated using age in completed years, defined as the age in years at the time of the event or age on the last birthday.
A surgical case of SCC is defined as incident in a given year if it was not preceded within 365 days by a hospitalization with a procedure classified as SCC, whether the procedure was unilateral or bilateral. Regional and departmental incidence rates are age-standardized to the French population in 2022.

Calculation of the Comparative Morbidity Figure

To compare each regional (or departmental) incidence rate standardized to the national incidence rate, the ratios between these two rates (Comparative Morbidity Figure) were calculated, along with their 95% confidence intervals.

CMFregion x = STDInc region x / NationalInc

Caution in Interpreting the Data

Data collection in the PMSI has an initial medico-economic objective rather than an epidemiological one. The results of this surveillance should therefore be interpreted with caution. Since not all SCCs undergo surgery (e.g., symptomatic treatments such as corticosteroid injections), the tracer does not allow for the calculation of the overall incidence of the disease but is limited to the incidence of surgically treated cases. The regional or departmental differences observed may thus reflect differences in the incidence of the condition (varying distributions of high-risk sectors and professions across regions, varying frequencies of high-risk endocrine conditions, etc.), but also sometimes heterogeneity in the coding practices for surgical procedures or differences in medical practice (choice of surgical treatment versus medical treatment) despite the existence of medical guidelines, or even differences in access to care.

Epidemiological Situation in France in 2022

The crude incidence rates of surgical SCC cases, by age and sex, in France in 2022 are presented in Figure 1 and Table 1. The incidence rate rises sharply with age up to age 59, then shows a slight decline at retirement age (60–69 years) before rising again among older adults up to ages 80–84. The incidence rate of surgical cases is higher among women and peaks among them between the ages of 50 and 59, corresponding to the age of menopause onset.

Trends in mainland France in the incidence rates of surgical cases of SCC

The trend between 2007 and 2022 in national incidence rates (mainland France) of surgical intervention for SCC, by sex, for all ages combined, and for those aged 20–64, is shown in Figure 2. The incidence rate of surgical cases of SCC (combined men and women) decreased significantly between 2007 and 2022, with an average annual decline of 1.1% (1.8% among those aged 20–64). This reflects a significant downward trend in the incidence rate among women, with an age-adjusted average annual decrease of 2.1% (2.6% among those aged 20–64), in contrast to men, among whom the incidence rate showed a significant upward trend during this period, with an age-adjusted average annual increase of 0.6%. Among men aged 20–64, incidence rates remained stable. Age-specific incidence rates were calculated for mainland France for the various years of surveillance (2007 to 2022), first for the total population and then for each sex (Tables 2–4). Regardless of gender or age group, a one-time drop in incidence rates occurred in 2020, corresponding to reduced healthcare utilization due to the COVID-19 health crisis. Among men, the increase in rates between 2007 and 2022 was observed among those aged 55 and older, and more specifically among those aged 70 and older. Among women, incidence rates are observed to increase starting at age 70 over the ^period1.

¹ Trends by age group not tested.

Regional incidence rates in 2022

The incidence rate of surgical cases of SCC varies significantly from one region to another: standardized rates ranging from 242 per 100,000 person-years (PY) in the Grand-Est and 240 per 100,000 PY in Normandy to 36 per 100,000 PY in Réunion. Regional incidence rates and their comparison with the national incidence rate, presented as a Comparative Morbidity Figure (CMF), are shown by sex for the entire population (Tables 5–6) and for the 20–64 age group (Tables 7–8).
Maps 1 and 2 show the CMF for each region, by sex, for all ages. Maps 3 and 4 show the CMF for each region, by sex, among those aged 20–64. The regions are divided into five CMF classes with thresholds (0.7 / 0.9 / 1.1 / 1.3) corresponding respectively to variations of -30%, -10%, +10%, and +30% relative to the national incidence rate.

Departmental incidence rates in 2022

The incidence rate of surgical cases of SCC also varies from one department to another. Departmental incidence rates and their comparison with the national incidence rate, presented as a comparative morbidity figure (CMF), are shown for the entire population (Tables 9–10) and for the 20–64 age group (Tables 11–12). Maps 5 and 6 show the CMF for each department, by sex, for all ages. Maps 7 and 8 show the CMF for each department, by sex, among those aged 20–64. The departments are divided into five CMF categories with thresholds (0.7 / 0.9 / 1.1 / 1.3) corresponding respectively to variations of -30%, -10%, +10%, and +30% relative to the national incidence rate. For the same age structure, the northern half of France, with the exception of the Brittany and Île-de-France regions, generally has higher incidence rates of SCC surgical cases than the southern half (maps 5 to 8). This north-south difference is less pronounced among people aged 20–64.

Epidemiological Situation in the Overseas Departments in 2022

Incidence data are presented for all overseas departments except Mayotte (due to the very low number of observed cases, which is incompatible with statistical confidentiality). In the overseas departments, the age-standardized incidence rates for the French population in the year of surgical cases of carpal tunnel syndrome are lower than in mainland France, with the exception of rates in Martinique, which nevertheless remain low as well (Table 7). As in mainland France, incidence rates are higher among women than among men.

Crude incidence rates were higher in 2022 among those aged 20–64 than in the population of all ages, except in Guadeloupe and Martinique among men (Table 13). This holds true for the various years of the follow-up (Tables 16, 18, 20, 22). Standardized incidence rates and their comparison to the national incidence rate, presented as a comparative morbidity figure (CMF), are shown for the entire population and for the 20–64 age group, which comprises the majority of the working-age population (Table 14). Among men, age-standardized incidence rates are between four and five times lower in Réunion and French Guiana than for France as a whole. Among women, the age-standardized incidence rate is also between four and five times lower in Réunion compared to the national rate (CMF=0.21), and twice as high as that of men (Tables 13 and 14). In contrast, the age-standardized incidence rate among women in Martinique is close to that of France.

Detailed results by French Overseas Department in 2022 and incidence trends

• Guadeloupe – 971

Guadeloupe is among the departments with the lowest standardized incidence rates of surgical SCC cases in 2022 (Table 9) for men (60 per 100,000 men), along with Réunion, French Guiana, and Paris. The standardized incidence is also low among women (126 per 100,000 women), but higher than in Réunion, French Guiana, Paris, Hauts-de-Seine, and Haute-Corse.

Incidence rates in Guadeloupe increase gradually with age among men. Among women, a peak in the incidence rate is observed at ages 50–59, corresponding to the age of menopause; the incidence then decreases and rises again until the 70–79 age group (Figure 3 and Table 15).

Incidence rates (crude rates), which were relatively stable among women in Guadeloupe between 2007 and 2009, declined between 2010 and 2020 before rising again starting in 2021, as observed among women in mainland France (with a more significant decline in Guadeloupe). Among men, rates are stable, unlike in mainland France, where they are increasing. However, a dip in incidence was observed for both sexes in Guadeloupe in 2017. The same trends are observed in the general population and in the working-age population (Figure 4 and Table 16). Analysis of the age-adjusted trend in the general population shows an average annual decrease between 2007 and 2022 of -7.0% among women and -2.0% among men.

• Martinique – 972

In 2022, the age-standardized incidence rate of surgical cases of carpal tunnel syndrome (Table 9) among men in Martinique (86 per 100,000 men) is among the lowest in France, comparable to those of other French overseas departments, certain departments in the Île-de-France region (Hauts-de-Seine, Paris, Seine-Saint-Denis), and Haute-Corse. Among women, the standardized incidence rate is close to the incidence rate for France (210 per 100,000 women in Martinique versus 209 per 100,000 women) (Table 13).

In Martinique, incidence rates increase gradually with age among men. Among women, a peak in the incidence rate is observed at ages 50–59, corresponding to the age of menopause; the incidence then decreases and rises again, as at the national level, but only up to the 70–79 age group (Figure 5 and Table 17).

The incidence (crude rates) of surgical SCC cases increased in Martinique between 2007 and 2022, among men (where rates more than tripled) as well as among women (an increase of approximately 50%), and among those aged 20–64 as well as for the general population (Figure 6 and Table 18). This trend differs from that observed in mainland France, where a downward trend in incidence was noted. Analysis of the age-adjusted trend in the general population shows an average annual increase between 2007 and 2022 of +1.0% among women and +3.9% among men.

• French Guiana – 973

The age-standardized incidence rates of surgical SCC cases in French Guiana in 2022 are among the lowest in France (45 per 100,000 men and 102 per 100,000 women), comparable to those of other overseas departments (except among women in Martinique), certain departments in the Île-de-France region (Hauts-de-Seine, Paris, Seine-Saint-Denis) and Haute-Corse (Table 9).

French Guiana has the largest difference between crude and age-standardized rates among the French overseas departments, with age-standardized rates nearly twice as high as crude rates, reflecting the youthfulness of the Guianese population. Incidence rates increase with age up to the 50–59 age group among women, corresponding to menopause. Incidence rates also increase with age among men (Figure 7 and Table 19).

Incidence rates were calculated in French Guiana between 2010 and 2022. For both women and men, the crude rates are relatively stable. A more significant temporary increase in incidence was observed for both sexes between 2014 and 2016 and again in 2019 (Figure 8 and Table 20).

• Réunion – 974

The age-standardized incidence rates of surgical SCC cases in Réunion in 2022 are the lowest in France (27 per 100,000 men and 45 per 100,000 women), comparable to those in the other French overseas departments (except among women in Martinique) (Table 9).

An INSEE study found that residents of Réunion sought hospital care less frequently than those in mainland France, particularly among those aged 40 to 69. This study also noted that the density of private specialist practitioners was lower than in mainland France and that travel times to see specialists were longer than for general practitioners (INSEE Analyses No. 19 – November 2016). In 2021, the density of orthopedic surgeons and traumatologists was 1.7 per 100,000 inhabitants in Réunion, whereas it was 4.1 per 100,000 inhabitants in mainland France (learn more). This contrast was not observed for general practitioners, whose density was higher in Réunion (96.1 per 100,000 inhabitants) than in mainland France (77.3 per 100,000). Nearly half of carpal tunnel syndrome cases (51% among men and 45% among women) are believed to be attributable to occupational activities. The low employment rate among 15- to 64-year-olds in Réunion (50.4% among men and 41.9% among women) compared to France as a whole (66.6% among men and 60.9% among women) may also partly explain the low incidence rates of surgical cases of CTS observed. The occupational categories of women in Réunion may, to a small extent, explain the low incidence observed. Indeed, in 2020, the percentage of female manual workers in Réunion was 5.0% among employed women, compared to 8.1% in France as a whole (learn more), yet the risk of undergoing surgery for SCC is higher in this occupational category (C. Ha et al. 2009).

Among men in Réunion in 2022, the incidence rate increases with age up to the 80+ age group, as seen nationally (up to 80–84 years), despite a slight decline among those aged 60–69. Among women in Réunion, a first peak in the incidence rate is observed at menopause (ages 50–59), followed by a second, smaller peak among those aged 70–79 (Figure 9 and Table 21).

Crude incidence rates were measured in Réunion between 2007 and 2022, among men and women, for those aged 20–64 and in the general population (Figure 10 and Table 22). A decrease in the incidence of surgical SCC cases was observed from 2007 to 2011 (more pronounced among women). Between 2012 and 2018, the incidence gradually increased again in Réunion (except for a more significant temporary decrease in 2013–2014) among both men and women, but incidence rates remained low, and among women, lower than those in 2007. Since 2018, incidence rates have tended to decrease slightly. We do not have sufficient data regarding the practices and movements of surgeons performing carpal tunnel syndrome surgeries in Réunion over this entire period to explain these changes in incidence.