Is a Right Angle the Right Angle? Normal Coronal Radiographic Alignment in the Pediatric Finger Phalanges

Area of Science:

• Orthopedic surgery
• Pediatric radiology
• Anatomy

Background:

• Accurate assessment of pediatric phalanx fracture displacement relies on understanding normal phalangeal alignment.
• Coronal plane alignment of pediatric phalanges has not been previously studied.
• Existing assumptions of perpendicularity between articular surfaces/physes and diaphyses are untested.

Purpose of the Study:

• To test the hypothesis that coronal plane relationships between pediatric phalangeal diaphyses, articular surfaces, and physes are not uniformly perpendicular.
• To assess variations in these relationships by digit and age.

Main Methods:

• Retrospective review of hand bone age radiographs from 80 children (2-18 years old).
• Measurement of angles between diaphysis and distal articular surface (D-DA), physis (D-P), and proximal articular surface (D-PA) for proximal (P1) and middle (P2) phalanges.
• Calculation of intra-rater and inter-rater reliability, confidence intervals for angles, and analysis of variance for age and sex variability.

Main Results:

• High intra-rater and inter-rater reliability (>0.90) generally observed.
• Only 47.8% of measured angles were within 90 degrees.
• Specific angles in the small finger (P1 ∠D-DA, P2 ∠D-P, P2 ∠D-PA) consistently deviated from 90 degrees.
• Ten of 24 angles varied significantly with age, particularly in the index and middle finger P1.

Conclusions:

• Coronal radiographic angles in pediatric finger phalanges frequently deviate from 90 degrees.
• Significant age-related variations exist in these angles.
• Phalangeal articular surfaces and physes are not uniformly perpendicular to diaphyses, necessitating consideration of digit, phalanx, age, and individual variability in clinical assessments.