Circular Knife

What it is

The Circular Knife (also called a ring knife or myringotomy ring knife) carries a small, circular or semi-circular blade at the tip of a slender handle. The blade geometry allows the surgeon to trace the circumference of the tympanic membrane or perforation margin in a single continuous motion — something no straight or sickle blade can do without multiple repositionings. The result is a uniform, clean edge all the way around the membrane, which is critical for consistent graft take.

When & how it's used

Used during myringoplasty and tympanoplasty to freshen the edges of a tympanic membrane perforation before graft placement. The perforation margin must be denuded of its epithelial edge (the squamous epithelium that has rolled inward over time) to expose a raw, vascular rim that will accept and incorporate the graft. The circular knife performs this circumferential freshening in a single controlled pass. Also used to score the annular region when a total or near-total drum replacement is planned.

The circular knife addresses one of the most technically specific steps in tympanoplasty: freshening the perforation margin. Graft failure is often traced back to inadequate edge preparation — if any epithelialised rim is left around the perforation, the graft will not incorporate and the repair will break down. The ring blade of the circular knife allows a single, uninterrupted circumferential incision that a straight or angled blade cannot replicate without multiple strokes and repositionings.

Design features

• Ring or semi-circular blade: traces the full circumference of a perforation margin in one continuous motion
• Slender shaft: passes through an aural speculum under the operating microscope without obscuring the field
• Blade sized to perforation: small and large ring variants to match the diameter of the defect
• Stainless steel, autoclavable: withstands standard steam sterilisation

Why perforation edge freshening matters

A chronic tympanic membrane perforation does not have a raw edge. Over time, the squamous epithelium of the outer drum surface migrates inward and rolls over the edge of the perforation, creating a smooth, epithelialised rim. A graft placed against this rim cannot achieve vascular union — the epithelium acts as a barrier. Before any graft is placed, this rolled edge must be removed to expose the underlying fibrous layer and vascular stroma.

The circular knife removes this edge cleanly and in one pass. The alternative — using a straight knife or scissors to nibble around the margin — introduces more handling, more bleeding points, and less consistent edge geometry.

Position in the tympanoplasty sequence

The circular knife is used in the early-to-middle phase, after the tympanomeatal flap is raised and before graft placement:

1. Flap knife → canal incisions
2. Sickle knife → flap development and annular incision
3. Elevator → flap reflection, middle-ear exposure
4. Circular knife → perforation edge freshening
5. Cup / crocodile forceps → middle-ear preparation
6. Graft placement and flap re-draping

Frequently Asked Questions

What is a circular knife used for in ear surgery? It is used to freshen the edges of a tympanic membrane perforation before graft placement in myringoplasty or tympanoplasty. The ring blade removes the inward-rolled epithelial rim around the perforation, exposing a raw vascular edge that will incorporate the graft.

Why does the perforation edge need to be freshened? A chronic perforation develops an epithelialised margin — squamous skin that has migrated over the edge. A graft cannot bond to epithelium; it needs a raw, vascular surface. Skipping edge freshening is a leading cause of graft failure.

Can the same result be achieved with scissors or a straight knife? Technically yes, but less efficiently. Scissors and straight knives require multiple repositionings to work around a circular margin, each introducing additional handling and bleeding. The ring blade achieves the same result in one continuous stroke with a consistently uniform edge depth.

What size ring blade should be used? The ring diameter should approximate the perforation size — a small ring for central perforations up to roughly 3–4 mm in diameter, a large ring for subtotal or near-total defects. Using a blade significantly larger than the perforation risks freshening healthy drum tissue unnecessarily.