What measurements are included in arm span for pediatric patients with physical disabilities?

Arm Span Measurement Components

Arm span is measured as the distance between the tips of the middle fingers when both arms are stretched horizontally against a ruler, measured to the nearest millimeter. 1

Measurement Technique

• The patient should stretch both arms horizontally against a ruler or measuring device 1
• The measurement extends from the tip of the middle finger of one hand to the tip of the middle finger of the opposite hand 1
• Readings should be recorded to the nearest millimeter for precision 1
• The measurement error is approximately 0.5 cm, which is comparable to the error in standard height measurements 1

Clinical Application in Pediatric Disabilities

For children with osteogenesis imperfecta and other skeletal abnormalities, arm span should be measured using the "hill and valley method" with a flexible tape measure that follows the curves of the arms. 1

• This modified technique accounts for multiple upper extremity fractures, surgical rodding, and bowing deformities that are common in conditions like osteogenesis imperfecta 1
• The flexible tape measure follows the contours of the arm rather than measuring in a straight line 1
• This approach is particularly important when spinal abnormalities, severe growth retardation, or skeletal deformities make standard height measurements unreliable 1

When to Use Arm Span as Height Surrogate

• Arm span serves as an alternative to standing height in children with spinal abnormalities including kyphosis or scoliosis 1, 2
• It is appropriate for nonambulatory children who cannot stand for height measurement 2
• Arm span is highly correlated with actual height (R²=0.93-0.97) in children aged 2-6 years 2, 3
• The measurement is particularly valuable for calculating predicted lung function values, which are heavily dependent on height in their formulae 1

Important Caveats

• In children with osteogenesis imperfecta, arm span measurements may be challenging due to multiple upper extremity fractures, rodding, and bowing of the arms 1
• Clinicians should critically interpret pulmonary function results that appear excessively good in severe skeletal dysplasias, as these may reflect inaccurate predictions from the height-based equations 1
• The relationship between arm span and trunk/leg proportions may vary across ethnic groups and successive birth cohorts, potentially affecting the accuracy of height predictions 1