The impact of experience on recurrence rates after biopsy punch excision for pilonidal disease

Abstract Aim We present the outcomes and the recurrences of 848 patients with pilonidal disease (PD) treated by biopsy punch excision (BPE) and we weigh our results against progressively obtained operative experience. BPE is a modified ‘merged’ version of both the Bascom ‘pit picking’ procedure and the Gips procedure. It employs biopsy punches of different calibre, depending on whether treatment is in the natal cleft (calibre as small as possible) or lateral (larger calibre punches or even small incision). Sometimes this procedure is referred to as the Bascom–Gips procedure. Methods In all, 848 consecutive patients with PD were treated from January 2011 until December 2016 (sex 622 [73.4%] men and 226 [26.6%] women; median age 26.2 years, mean age 24.6 ± 28.99 [range 14–55] years, men 25.1 years, women 24.8 years). Of these 848 patients, 287 were operated in 2011–2012, 301 in 2013–2014 and 260 in 2015–2016. The recurrence rates were recorded 12, 24 and 60 months after surgery both cumulatively and by examining the outcomes of the three biennia individually (years of treatment 2011–2012 or group A, 2013–2014 or group B, 2015–2016 or group C). Results The mean operating time was 34 ± 24.45 min. Postoperative complications included early (<24 h; n = 22 or 2.6%) and delayed (>24 h; n = 26 or 3.1%) postoperative bleeding. Postoperative fluid collections (<2 weeks) occurred in 83/848 patients (9.8%) and included haematoma (n = 25) and seroma (n = 58). Full recovery was obtained after a mean of 21 ± 12.72 days and work/school/university activities were resumed after a mean of 4 ± 12.02 days. Twelve‐, 24‐ and 60‐month follow‐ups were possible in 725 (85.5%), 682 (80.4%) and 595 (70.2%) patients out of 848. An overall significant (ꭓ 2 = 16.87, P = 0.0002) difference was found in the recurrence rates: 59 recurrences/725 patients (or 8.1%) after 1 year, 89 recurrences/682 patients (or 13.0%) after 2 years and 98 recurrences/595 (or 16.4%) after 5 years. However, when subgrouping patients in three 24‐month subsets, the recurrence rates showed a steady and progressive decrease in the three biennia 2011–2012 (group A), 2013–2014 (group B) and 2015–2016 (group C) at 12‐, 48‐ and 60‐month follow‐ups. Recurrences after 12 months were 29/225 (12.9%), 19/285 (6.7%) and 11/215 (5.1%) (ꭓ 2 = 8.53, P = 0.014) in groups A, B and C respectively; after 24 months, 36/226 (15.9%), 31/242 (12.8%) and 22/214 (10.2%) (ꭓ 2 = 2.38, P = 0.30 N.S.) in groups A, B and C respectively; after 60 months, 38/194 (19.5%), 36/215 (16.7%) and 24/186 (12.9%) (ꭓ 2 = 2.23, P = 0.32) in groups A, B and C respectively. Conclusions BPE is an effective, disease‐targeted, minimally invasive and inexpensive way to treat PD. Its results are influenced by the experience of the team involved, especially regarding early recurrences/failure of surgery. At least 5‐year follow‐ups are needed to ascertain the outcome of surgery for PD.


INTRODUC TI ON
In the early 1980s Bascom showed that PD originates from hair follicles, hence giving solid scientific grounds to his minimally invasive surgery (MIS) approach [1,2], stating that 'wide excision of blocks of fat down to periosteum, an outmoded treatment, now seems equivalent to treating a pimple on the chin by cutting off the patient's head!' [3]. In 2008, Gips et al. [4] slightly modified Bascom's original MIS technique by employing trephines and disposable biopsy punches to excise only the diseased PD tissue. Recently, other MIS techniques have been developed, employing instruments such as fistuloscopes or hysteroscopes [5,6]. We perform biopsy punch excision (BPE), which is a modified 'merged' version of Bascom's 'pit picking' procedure and the Gips trephines procedure and employs biopsy punches often of different calibre, depending on whether treatment is in the natal cleft (calibre as small as possible) or lateral (larger calibre punches or even a small incision is performed).
Sometimes BPE is referred to as the Bascom-Gips procedure. We present the outcome of 848 PD patients operated from 2011 until 2016 by means of BPE and weigh PD recurrences against the progressively achieved experience with this technique. The hypothesis is that removal only of diseased tissue suffices to treat PD ('see and treat') and that this approach becomes particularly effective with experience.

Data handling and statistical analysis
Descriptive data were calculated as mean ± SD. The χ 2 test was carried out to define associations between categorical factors and groups. To assess whether data for independent samples were of Gaussian distribution, D′Agostino's K 2 normality and Levene's homoscedasticity tests were applied (where the null hypothesis is that the data are normally and homogeneously distributed). A significant cut-off level (α) was set at a P value of 0.05 (Statistica 7 package for Windows) [8].

RE SULTS
The mean operating time was 34 min (median 35, range 19-55).  Table 1). Figure 5 depicts the trend of recurrences with respect to consecutive cases. of the three biennia, also follow-ups after 24 and 60 months showed improving trends, with decreasing recurrences. These trends did not reach statistical significance, yet 5-year recurrences fell from 19.5% (in group A or first biennium 2011-2012) to 12.9% (in group C or third biennium 2015-2016), which confirms the importance of surgical 'experience' in BPE. 'Learning curves' are the visual representation of acquired experience, representing the rate of learning alongside repeated experiences or over time. Learning curves were first described in snails [11] and in the aircraft industry [12], and their importance has later been stressed in conventional, laparoscopic [13] and hi-tech surgery [14,15]. Our research confirms the importance of experience, especially in decreasing the rate of 'failed' surgery, even in BPE for PD.

DISCUSS ION
Full assessment of PD can be tricky; therefore other MIS techniques have been developed [5,6,16,17] which entail the use of a fistuloscope/paediatric hysteroscope, an obturator, a monopolar electrode (to be changed every few sessions), a brush and endoscopic forceps, all the equipment costing around €8000 or US$9400. These endoscopic procedures are based on the same sound approach; however, equally good results may be achieved with inexpensive instruments as long as these are handled by specially dedicated surgeons.
This study has some limitations. Although the data were collected prospectively, data analysis was only performed retrospectively. Besides, the lack of a control group may reduce the strength and impact of our results.

CON CLUS IONS
BPE is an effective, disease-targeted and inexpensive MIS way to treat PD, simple to perform but better handled by surgeons with experience in this technique, especially when early 'recurrences' (or 'failures') are considered. Its low cost, low recurrence rate, short operating time and rapid postoperative recovery all recommend BPE.
Finally, after surgery for PD, at least 5 years of follow-up are needed to determine the surgical outcome.

E TH I C S S TATEM ENT
This study was approved by our local ethics committee and writ-

I N FO R M ED CO N S ENT
Informed consent was obtained from all individual participants included in the study. Describe any efforts to address potential sources of bias 7

DATA AVA I L A B I L I T Y S TAT E M E N T
Study size 10 Explain how the study size was arrived at 6 Quantitative variables 11 Explain how quantitative variables were handled in the analyses. If applicable, describe which groupings were chosen and why