Normal or Not? Acetabular Morphology Is Not a Binary Classification.

Area of Science:

• Orthopaedic surgery
• Radiology
• Biostatistics

Background:

• Orthopaedic decision-making relies on clinical judgment, radiological measurements, and standards.
• Hip pathology is often viewed as a mechanical issue, analyzed using geometric and statistical methods.
• Useful clinical measurements must be simple, reproducible, and linked to condition risk.

Purpose of the Study:

• To critically evaluate current radiographic measurements for hip dysplasia risk assessment.
• To differentiate between population-based normative data and outcome-driven decision limits.
• To trace the evidence supporting commonly used hip morphology measurements.

Main Methods:

• Review of the origins, current application, and statistical validity of key hip measurements.
• Analysis of reproducibility and clinical decision-making utility for specific angles and classifications.
• Examination of nomenclature drift and dataset validation issues.

Main Results:

• Common hip measurements like the lateral center-edge angle and Tönnis angle have questionable validation against their reference datasets.
• Nomenclature inconsistencies lead to miscommunication in clinical practice.
• The current phenotypic risk model may be less effective than a continuous dose-response model.

Conclusions:

• Legacy morphological risk models for hip dysplasia may not effectively curtail osteoarthritis progression.
• There is a need to reconstruct or fundamentally re-evaluate hip morphology assessment models.
• Clinical reliance on unvalidated or outdated measurements warrants critical review.