Peripheral quantitative computed tomography: measurement sensitivity in persons with and without spinal cord injury

Area of Science:

• Orthopedics
• Radiology
• Bone Metabolism

Background:

• External tibia length measurements are crucial for assessing bone mineral density (BMD).
• Peripheral quantitative computed tomography (pQCT) is used to measure tibia trabecular BMD.
• Spinal cord injury (SCI) can affect bone density.

Purpose of the Study:

• To quantify the error in tibia length measurements using pQCT.
• To assess the impact of these measurement errors on scan location and tibia trabecular BMD in SCI patients.

Main Methods:

• Blinded comparison of tibia length measurements.
• pQCT analysis in able-bodied subjects and SCI patients.
• Quantification of BMD error due to slice placement variations.

Main Results:

• The projected worst-case tibia length measurement error resulted in a +/-3 mm pQCT slice placement error.
• Absolute BMD error was higher in able-bodied subjects (5.87 mg/cm(3)) compared to SCI subjects (4.5 mg/cm(3)).
• Percentage error in BMD was significantly larger in SCI subjects (4.56%) than in able-bodied subjects (2.23%).

Conclusions:

• Limb length measurement errors can account for up to 5% of BMD differences in cross-sectional studies.
• These findings are critical for accurate interpretation of BMD in populations with varying limb lengths and in SCI research.