Reliability and sensitivity of joint space measurements in hand radiographs using computerized image analysis

Area of Science:

• Radiology
• Orthopedics
• Rheumatology

Background:

• Accurate measurement of joint space width is crucial for assessing joint health and disease progression.
• Standard clinical radiographs are widely used, but their sensitivity to subtle changes requires validation.

Purpose of the Study:

• To determine the sensitivity and reliability of proximal interphalangeal (PIP) and metacarpophalangeal (MCP) mean joint space measurements from standard clinical radiographs.
• To establish the threshold for detecting actual changes in joint size based on radiographic measurements in healthy subjects.

Main Methods:

• Repeat hand radiographs of healthy subjects were obtained using standard techniques at 3-5 day intervals.
• Measurements were taken with hands in a flat position and in various flexed positions.
• Custom software was used for mean joint space determination, with manual validation and analysis of variance for reproducibility.

Main Results:

• In standard positions, changes > 0.11 mm (approx. 7%) indicate a physical change in joint space width (95% probability).
• Averaging across fingers reduces the detectable change to 0.05 mm (approx. 3%).
• Radiographic joint space increased with MCP flexure and decreased with PIP flexure.

Conclusions:

• Mean finger joint space measurements from standard radiographs are reliable and sensitive in healthy subjects, even with minor hand position variations.
• Further research is needed to ascertain if joint space changes in arthritis patients over 6-12 months exceed these detectable limits.