The "Keystone Angle": Geometry in Preservation Rhinoplasty

Nele G, Cavaliere A, Schonauer F.

What this paper says

The authors propose measuring the angle where bone meets cartilage on the bridge before surgery, and using it to choose which preservation technique suits each nose.

Overview

The shape of the bony bridge significantly affects how a nose looks in profile. The authors define the keystone angle as the angle formed between the bony and cartilaginous parts of the bridge. They note that a V shaped bony bridge typically has a sharper keystone angle than an S shaped one, and that an ideally flat bridge corresponds to an angle of 180 degrees.

Sections of note

Article type: brief conceptual proposal. Level of evidence V, the lowest grade.
The keystone angle is defined as the bone to cartilage angle of the bridge.
A V shaped bony bridge is described as having a more acute keystone angle than an S shaped bony bridge.
Ideal bridge flatness is stated to correspond to a keystone angle of 180 degrees.
Different techniques can be used to reach that ideal.
Proposal: preoperative assessment of the keystone angle should guide which technique is chosen for each patient.
No patient numbers, measurements, outcomes or techniques matched to angles appear in the abstract.

What it means for a patient

The profile line of the bridge is not uniform. Where bone meets cartilage there is an angle, and how sharp it is shapes the side view.
The proposal is that this angle be measured before surgery, so the technique fits the starting anatomy rather than being applied uniformly.
The abstract carries no findings. It does not state which technique suits which angle, and reports no results.
No patients were studied, and the concept has not been validated.

Why this paper matters

Preservation rhinoplasty keeps the bridge intact, so the starting shape of the bridge largely determines the result, which makes preoperative shape assessment more consequential than in conventional surgery. Naming a measurable geometric property gives surgeons something to record. Whether the angle predicts which technique works best is untested.

Terms

Keystone area: where the nasal bones meet the upper lateral cartilages and septum.
Bony dorsum: the upper part of the bridge formed by the nasal bones.
Cartilaginous dorsum: the lower part of the bridge formed by cartilage.
Preservation rhinoplasty: reshaping that keeps native nasal structures intact.
Lateral view: the profile view of the face seen from the side.

Summary written by rhinoplasty.cc from the abstract, 2026-09-09; not medical advice. The authors' own abstract follows.

From the abstract

“Rhinoplasty outcome may depend on different factors and bony dorsum shape has proven to significantly influence the lateral view result. The "Keystone angle" corresponds to the osseocartilaginous angle formed between bony and cartilaginous dorsum. Usually, the "V" shaped bony dorsum is characterized by a more acute…”

Excerpt; the full abstract is on PubMed.