Rhinogoniometer: Validation of an Instrument for Rhinoplasty

Overview

The position of the tip cartilages affects nasal function. When those cartilages sit too high, the angle between them is usually under 60 degrees, which can leave the nostril opening prone to collapse. The study validated the rhinogoniometer, an instrument for measuring that angle during surgery, against computerized image analysis and tested whether two surgeons obtain the same readings.

Sections of note

• Validation study in 31 primary rhinoplasty patients.
• The angle of divergence, formed between the two outer arms of the tip cartilages, was measured during surgery.
• Rhinogoniometer readings were compared with computerized analysis.
• A significant difference was found between the two methods overall, P equals 0.034.
• On average the instrument read 3.7 degrees smaller than the software.
• Where both methods measured above 75 degrees, the discrepancy between them was larger, P equals 0.022.
• For angles up to 75 degrees, the instrument read on average 0.79 degrees higher than the software.
• Comparing readings between two different surgeons showed a significant difference, P less than 0.023, though the authors state the measurements were reproducible.

What it means for a patient

• The instrument lets a surgeon measure cartilage position during the operation rather than estimating it.
• Accuracy was close to the software reference in the range where the clinical decision matters, under 75 degrees.
• The abstract reports both a significant difference between surgeons and a conclusion that readings are reproducible, which are difficult to reconcile.
• Thirty one patients is a small validation sample.

Why this paper matters

Cartilage malposition is diagnosed by inspection and feel, which varies between surgeons, and the resulting nostril collapse is a common functional complaint. This instrument turns that judgment into a number during surgery. Whether measuring the angle changes surgical decisions or outcomes is not tested.

Terms

• Rhinogoniometer: a surgical instrument for measuring the angle between the tip cartilages.
• Lower lateral cartilages: the paired cartilages forming the nasal tip.
• Cephalic malposition: tip cartilages sitting higher and more sideways than normal.
• Angle of divergence: the angle formed between the two outer arms of the tip cartilages.
• External nasal valve: the nostril opening, which can collapse and block airflow.
• Reproducibility: whether different observers obtain the same measurement.