Bone Age Studies

Carla M. Allen; Taylor M. Otto

Upper Extremities

25 Bone Age Studies

Anatomy & Pathology

Anatomy Overview
Bone age (skeletal maturity) assessments evaluate ossification and epiphyseal fusion to determine the physiologic, rather than chronologic, age of a child. The examination focuses on the hand and wrist, where multiple ossification centers provide reliable indicators of skeletal development.

Primary Structures: carpals, metacarpals, phalanges, radius, ulna, distal humerus (occasionally)
Key Landmarks: distal radius and ulna epiphyses, phalangeal growth plates, carpal ossification centers

Common Pathologies and Indications

Endocrine and Growth Disorders: Growth hormone deficiency, hypothyroidism, precocious puberty, delayed puberty
Cretinism: Congenital hypothyroidism characterized by delayed ossification, widened cranial sutures, and slowed bone growth
Constitutional Growth Delay or Advanced Maturation: Evaluation of developmental timing
Pre- or Post-Surgical Evaluation: Particularly for orthopedic or endocrine surgical planning

Projections

PA Hand and Wrist (for Bone Age Evaluation)

CR Location & Positioning

SID: 40 inches
Patient position: Seated at the table, hand and forearm resting palm-down on the IR
Adjustments:
- Use the left hand and wrist (standardized for comparison with reference atlases)
- Fingers extended and slightly separated
- Forearm and hand in the same plane, palmar surface flat on IR
- If the wrist cannot be completely flat, place a small sponge under the hand to reduce rotation
CR: Perpendicular to the mid-metacarpal area, centered midway between the distal radius and proximal metacarpals
Pt. Instructions: Remain still; no breath-hold required
Exposure: Low-to-moderate kVp to visualize soft tissues and fine bone detail

Evaluation Criteria

Coverage: Entire hand and wrist, including distal radius and ulna, visible and centered
Rotation checks: Symmetric appearance of phalangeal shafts; equal spacing between metacarpal heads
Motion checks: Sharp trabecular markings and clear cortical margins
Technique checks: Adequate contrast to demonstrate individual ossification centers
Clinical aim: Provides an image for comparison to standardized bone-age atlases (Greulich & Pyle, Tanner-Whitehouse)

Optional Projection: Elbow (Surgeon-Specific)

CR Location & Positioning

SID: 40 inches
Patient position: Seated with arm extended in AP position
Adjustments: Shoulder, elbow, and wrist in same horizontal plane
CR: Perpendicular to mid-elbow joint
Pt. Instructions: Suspend motion
Exposure: Moderate kVp to show distal humeral and proximal ulnar/radial epiphyses

Evaluation Criteria

Coverage: Distal humerus and proximal radius and ulna including growth plates
Rotation checks: Epicondyles in profile, open joint space
Clinical aim: Demonstrates ossification centers at the elbow when required for orthopedic or endocrine assessment.

Comparison of Bone Age Assessment Methods

Feature	Greulich & Pyle (GP) Atlas	Tanner–Whitehouse (TW2 / TW3)
Basis of Evaluation	Standardized atlas of left hand and wrist radiographs (1950s U.S. population)	Numerical scoring of individual ossification centers in hand and wrist
Process	Single PA image compared visually to age-matched reference images	Assigns maturity scores to selected bones, sums them, and converts to skeletal age
Strengths	Simple, fast, and widely used; strong inter-observer consistency	Quantitative, reproducible, adaptable for longitudinal studies
Limitations	Based on homogeneous population; may not reflect ethnic or socioeconomic variation	More time-consuming; requires training and reference charts

Hows & Whys of Bone Age Radiography

Anatomy

Which bones are evaluated for skeletal maturity?
The carpals, metacarpals, phalanges, distal radius, and distal ulna, as they show predictable ossification patterns through childhood.
Why is the left hand typically used?
To maintain standardization with the Greulich and Pyle atlas, which was developed using left-hand images.

Positioning

Why is the hand placed palm-down for the PA projection?
To keep the carpal bones and growth plates closest to the IR, minimizing magnification and distortion.
Why must the hand and forearm be in the same plane?
To prevent foreshortening and ensure accurate bone length and alignment comparison with reference standards.
Why are fingers extended and slightly separated?
To avoid soft-tissue overlap and allow clear visualization of each phalangeal growth plate.

Technique & Image Evaluation

How can you tell if the hand was rotated?
Unequal concavity of the shafts of the metacarpals, unequal spacing between the metacarpal heads or asymmetric soft-tissue margins along the phalanges.
How can you tell the exposure was appropriate?
Cortical outlines are sharp, with visible trabecular patterns in the carpals and phalanges, and the growth plates are distinct but not overexposed.
How can you tell that the correct anatomy was included?
The image includes all carpals through the distal radius and ulna and the entire phalangeal series without cutoff.

Clinical Applications

Why is bone age important in pediatric imaging?
It helps correlate skeletal development with chronologic age, aiding diagnosis and treatment planning for endocrine or growth abnormalities.
How is skeletal age determined?
By comparing the radiograph to reference atlases (e.g., Greulich & Pyle or Tanner-Whitehouse methods).
Why might atlas-based assessment have limitations?
The Greulich & Pyle atlas was based on a homogeneous 1950s population and may not account for ethnic and genetic variations in modern, diverse populations.
Why might a surgeon request a bone age elbow in addition to the hand?
To evaluate additional ossification centers when assessing surgical readiness or limb-length discrepancy.