The number of cases increased from 25,835 cases in 2007 to 31,033 cases in 2011, followed by a decrease to 30,235 cases in 2015. Considering the number of patients under 20 years of age, there was also an increase from 40 cases per 100,000 population in 2007 to 50 cases per 100,000 population in 2013. Ever since, the case numbers have remained relatively constant and have reached a plateau. The maximum number of case numbers was in the age group of 20-24 years. The female age group 10-14 years old is the only group among all investigated age groups with more cases than the respective male age group. The investigated data did not permit any epidemiological conclusions for pilonidal sinus disease because outpatient cases have not been included. The higher incidence in the female age group 10-14 years old could be explained by the earlier onset of adolescence. Thus, adolescence appears to have a major impact on the development of pilonidal sinus disease.

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Objective Sacro-coccygeal pilonidal sinus disease is a frequent surgical problem. Some authors assign the low recurrence rates of the Limberg flap to the flattening or elevation of the natal cleft. Summery of the background data: Numerous authors describe a flattening or elevation of the natal cleft as a result of a Limberg flap that originated from the gluteal region. However, thus far these were not quantified. Methods The aim of our study was to quantify the flattening or elevation, respectively, of the natal cleft. In the context of our study on the Limberg flap plasty with a homogenous group of 12 male patients, we measured the depth of the rima ani after the excision and we also measured the thickness of the Limberg flap. Results The median thickness of the rima ani at excision was 3.35 cm [IQR: 2.70; 4.18]. The median thickness of the Limberg flap was 4.85 cm [IQR: 3.90; 5.18]. The thickness of the rima ani after excision was statistically significantly less as compared to the thickness of the Limberg flap (p = 0.002). Conclusion In our study, we have shown the elevation of the crena ani with statistical significance by performing the Limberg flap for the treatment of sacro-coccygeal pilonidal sinus disease, leading to a flattening of the sacro-coccygeal region. As a deep crena ani is a factor in the pathogenesis of pilonidal sinus, the flattening of the sacro-coccygeal region with a Limberg flap plasty, as reported in countless publications, may explain the low recurrence rates.

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