M-Plasty Excision and Skin Repair (Combined Linear and Advancement Flaps)—An Analysis of Tissue Conservation Based on Euclidean Plane Geometry Model

Introduction: M-plasty is a complex surgical technique by creating two opposing skin flaps completed by central linear closure.¹ The success and cardinal feature of M-Plasty in comparison with conventional elliptical skin repair or other skin flaps stemmed are its significant reduction in excision of healthy skin tissue and reduction in overall wound perimeter and exposure vis-à-vis of the latter.²

Presentation: To illustrate and better understand the mechanism and degree of skin conservation, a vigorous and unbiased analysis of percentage tissue conservation with M-plasty by an Euclidean plane geometry model was performed.

The following tissue conservation quantitative analysis is based on the area of tissue removed, length, and width of excision.

The percentage reduction in tissue excision is calculated as follows:

1. Define variables.

Let’s denote A = Area.

A ellipse: Area of elliptical excision.

A M-plasty: Area of M-plasty excision.

A Flap: Area of triangular flap.

P reduction: Percentage reduction in tissue excision.

2. Calculate the areas.

For elliptical excision:

A ellipse = p × L/2 × W/2

Where L is the length and W is the width of the ellipse.

M-Plasty:

M-plasty involves creating an M-shaped incision with two triangular flaps,³ the excised area A. M-plasty is the total of the primary defect and the flaps.

The triangular base is b and the height is h,

then: A flap = ½ × b × h

To estimate the area reduction.

A lesion: Area of the lesion

A ellipse extra?: Extra tissue excised in an ellipse

A M-plasty extra: Extra tissue is excised around the lesion in an M-plasty.

Thus:

A ellipse = A lesion + A ellipse extra

A M-plasty = A lesion + A M-plasty extra

3. Calculate percentage reduction

P reduction = {(A ellipse-A M-plasty)/A ellipse)} × 100%.

4. Example calculation

Let’s assume:

Length of ellipse, L = 5 cm

Width of ellipse, W = 2 cm

The base of the triangle, b = 1 cm

Height of triangle, h = 0.5 cm

A lesion ˜ 2 cm square (arbitrary)

Elliptical Excision Area:

A ellipse = p × 5/2 × 2/2 = p × 2.5 × 1 = 2.5p ˜ 7.85 cm²

M-Plasty area:

A flap = ½ × 1 × 0.5 = 0.25 cm2

A M-plasty-extra = 0.25 × 4 = 1.0 cm² in approximation

A M-plasty = A lesion + A M-plasty extra = 2 + 1 = 3 cm²

Percentage reduction:

P reduction = [(7.85 − 3) / 7.85)] × 100% = (4.35/7.85) × 100% ˜ 61.8%.

The actual percentage reduction can vary based on the specific dimensions and surgical technique used.³ The pivoting variables are the length/width ratio of the marked ellipse and dimensions of the triangular advancement flaps (b and h).

Conclusion: From this analysis, M-plasty results in an approximate 61.8% reduction in the excision of healthy tissue compared with a standard elliptical excision for the same lesion. This parallel with the author’s clinical experience of 35 to 60% reduction. M-plasty (single or double advancement flaps) is appropriate in significant tissue conservation which is relevant to patient safety.

Publication History

Article published online:
07 February 2025