Parallelogram Excision: An Algorithmic Approach for Excision Designs in High-Tension Skin Areas.

Introduction: The excision of lesions that are not oriented along the skin tension lines may cause the surgeon to design extremely broad elliptical preoperative markings, with the intent to follow the tension lines as recommended for the best postoperative course and the best quality scars. The aim of this study is to describe and clinically apply a new surgical technique called the parallelogram excision technique, in which the traditional ellipse with a major axis parallel to the tension lines is converted into a parallelogram whose lesser sides are coincident with the local skin tension lines. This technique was specifically conceived for lesions whose major axis is non-coincident with skin tension lines, and the primary advantage is that it reduces the amount of healthy tissue excised.

Methods: Preliminarily to this clinical study, a comparative geometrical analysis was conducted between various excision shapes and angles using Geometry Pad version 2.7.10 (Bytes Arithmetic LLC) and verifying the data obtained through AutoCAD 2D 2016 (Autodesk, San Rafael, CA, USA), with the purpose of optimizing the technique from a geometrical point of view. A comparison was performed between the theoretical traditional elliptical excision and the hypothetical parallelogram excision. A pilot proof of concept clinical study was performed to verify the validity of the excisional design proposed. The patients considered for parallelogram excision suffered from skin lesions with a diameter no greater than 4 cm and oriented 45° to 60° with respect to tension lines. In order to limit variability, patients' ages were between 40 and 80, and the selected areas were limbs, sternum and dorsum. Scar quality was assessed with the validated POSAS method at 6 months post-operation.

Results: The geometrical analysis of the parallelogram's design showed that it allows a diminution of the excised healthy skin compared to the traditional ellipse. The clinical series included 16 patients, with a mean age of 63.5. Of these, nine patients were men and seven were women. Diagnoses included basal cell carcinoma in seven cases, dysplastic naevus in five patients, Bowen's disease in three individuals, and one case where a wider excision of a malignant melanoma was performed. Six-month follow up results showed: (1) an uneventful postoperative course; (2) good scar healing with an observer's POSAS median score of 16 and a patient's POSAS median score of 19; and (3) complete excision of lesions.

Conclusions: When indicated, the parallelogram excision technique appears to be a good option for the excision and primary closure of skin lesions that are not parallel to skin tension lines, since it allows a reproducible and surgeon-friendly method of preoperative marking and implies a favorable use of the local tension, which determines good quality scars. The amount of healthy tissue removed is smaller compared to traditional elliptic excisions.