Upper Extremities
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
Routine Projections (ARRT Required)
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
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.
