How reproducibly can human ear ossicles be measured? A study of inter-observer error

Area of Science:

• Biological anthropology
• Bioarchaeology
• Forensic anthropology

Background:

• Ear ossicles (malleus and incus) are underutilized in biological anthropology.
• Accurate and reproducible measurements are crucial for deriving biological information from these bones.

Purpose of the Study:

• To determine inter-observer measurement error for malleus and incus bones.
• To assess the reliability of measurements taken from digital images of ear ossicles.
• To provide recommendations for future studies on ear ossicle morphometrics.

Main Methods:

• Measurements were taken on digital images of malleus (N=119) and incus (N=124) bones from an early medieval German cemetery.
• Two observers performed measurements using a digital microscope.
• Inter-observer errors and reliability coefficients were calculated for two imaging methods: separately acquired images versus the same set of photographs.

Main Results:

• Mean inter-observer error ranged from 0.50-9.59% for malleus and 0.67-7.11% for incus.
• Reliability coefficients ranged from 0.72-0.99 for malleus and 0.61-0.98 for incus.
• Using the same set of photographs for measurements yielded lower error and higher reliability compared to separate image acquisition.

Conclusions:

• Measurements of malleus and incus using digital microscopy are reproducible.
• Standardizing measurement methods, particularly using shared image sets, is recommended to minimize inter-observer error.
• Addressing measurement error is essential for accurate data interpretation and combining results across studies in bioarchaeology.