Rethinking the causes of pilonidal sinus disease: a matched cohort study.

Our understanding of pilonidal sinus disease (PSD) is based on a paper published 29 years ago by Karydakis. Since then, surgeons have been taught that hair more easily penetrates wet skin, leading to the assumption that sweating promotes PSD. This postulate, however, has never been proven. Thus we used pilocarpine iontophoresis to assess sweating in the glabella sacralis. 100 patients treated for PSD and 100 controls were matched for sex, age and body mass index (BMI). Pilocarpine iontophoresis was performed for 5 min, followed by 15 min of sweat collection. PSD patients sweated less than their matched pairs (18.4 ± 1.6 µl vs. 24.2 ± 2.1 µl, p = 0.03). Men sweated more than women (22.2 ± 1.2 µl vs. 15.0 ± 1.0 µl in non-PSD patients (p < 0.0001) and 20.0 ± 1.9 µl vs. 11.9 ± 2.0 µl in PSD patients (p = 0.051)). And regular exercisers sweated more than non-exercisers (29.1 ± 2.9 µl vs. 18.5 ± 1.6 µl, p = 0.0006 for men and 20.7 ± 2.3 µl vs. 11.4 ± 1.4 µl, p = 0.0005 for women). PSD patients sweat less than matched controls. Thus sweating may have a protective effect in PSD rather than being a risk factor.

The Hair in the Sinus: Sharp-Ended Rootless Head Hair Fragments can be Found in Large Amounts in Pilonidal Sinus Nests.

PURPOSE: Hair has been identified as the causative agent of Pilonidal Sinus Disease (PSD). Stiffer, dark hair as well as hairiness has been postulated as causative factors. Astonishingly, despite the early clinical significance of this condition (Hodges in Boston Med Surg J 2:485-486, 1880), macroscopic and microscopic examinations of hair inside pilonidal sinus cavities have been scarce. The purpose of this study was to study the morphological aspects of the hair found in PSD in order to determine the origin of the hair. METHODS: Hair from inside pilonidal sinus cavities was collected intraoperatively from 20 PSD patients. Additionally, occipital, lumbar and intergluteal hair was harvested from the same patients and compared to the hair of volunteer-matched pair patients admitted to the hospital at the same time for non-PSD surgery. Intra- and intergroup variations of hair length were characterized with analysis of variance. Numbers and lengths of pilonidal sinus nest hair were recorded. Hair was examined clinically and with light and scanning electron microscopy using surface enhancing gold and carbon dust coating techniques. RESULTS: Analysis of 624 pilonidal sinus nest hair samples from 20 independent sinus cavities revealed that hair within pilonidal sinus nests is rootless in 74%. Shorter hair was found inside the pilonidal sinus compared to other sites (length 0.9 ± 0.7 cm p < 0.0001). Furthermore, hair found inside of the sinus was significantly shorter than hair protruding from pores (p < 0.000). Hair samples show razor sharp but no broken or split ends. On electron microscopy, these spiky hair ends resemble cut hair ends. Pilonidal hair nests contained between 1 and over 400 hair fragments. CONCLUSION: Short hair fragments with rootless sharp cut ends were found within pilonidal sinus cavities. Morphologically, these fragments resemble short cut rather than intact body hair. Since short cut hair, e.g., derived from the head potentially enters the pilonidal cavity more easily than longer hair, the source of these cut hair fragments needs to be eliminated when aiming to prevent Pilonidal Sinus Disease.

Strength of Occipital Hair as an Explanation for Pilonidal Sinus Disease Caused by Intruding Hair.

BACKGROUND: Pilonidal sinus disease is thought to be caused by intrusion of hair into healthy skin; loose hair in the intergluteal fold is thought to promote disease. However, compelling evidence to support these postulates is lacking; the cause of pilonidal sinus disease remains uncertain. OBJECTIVE: To determine whether particular properties of hair are associated with susceptibility to pilonidal sinus disease, we compared physical properties of hairs of patients with pilonidal sinus disease with hairs from control subjects who were matched for sex, BMI, and age. DESIGN: This was an experimental study with establishment of a mechanical strength test for single hairs to quantify the maximum vertical force that a hair could exert, following tests of strength of occipital, lumbar, and intergluteal hair. SETTINGS: Hair from patients with pilonidal sinus disease and matched control subjects were harvested from patients of the St. Marienhospital Vechta Department of Procto-Surgery. PATIENTS: A total of 17 adult patients with pilonidal sinus disease and 217 control subjects were included. MAIN OUTCOME MEASURES: ANOVA and intraclass and interclass variations of data gained from mechanical strength tests of occipital, lumbar, and intergluteal hair were included. RESULTS: Vertical hair strength was significantly greater in patients with pilonidal sinus disease. Occipital hair exhibited 20% greater, glabella sacralis 1.1 times greater, and intergluteal hair 2 times greater strength in patients with pilonidal sinus disease than in matched control subjects (all p = 0.0001). In addition, patients with pilonidal sinus disease presented with significantly more hair at the glabella sacralis and in the intergluteal fold. LIMITATIONS: The study was limited by its relatively small number of patients from a specific cohort of European patients. CONCLUSIONS: Occipital hair exhibited considerable vertical strength. Because occipital hair exerted the greatest force and cut hair fragments were found in the pilonidal nest in large quantities, these data suggest that pilonidal sinus disease is promoted by occipital hair. See Video Abstract at http://links.lww.com/DCR/A435.