A Method-Comparison Study Highlighting the Disparity between Osseous- and Skin-Based Measures of Foot Mobility

Area of Science:

• Biomechanics
• Orthopedics
• Radiology

Background:

• Foot mobility is crucial for understanding foot function and diagnosing conditions.
• Standard clinical measures of foot mobility are widely used but their accuracy relative to underlying bone movement is debated.

Purpose of the Study:

• To evaluate the validity of standard clinical foot mobility measures against radiographic skin-based and osseous measures.
• To determine the degree of agreement between different measurement techniques for arch height mobility, midfoot width mobility (MWM), and foot mobility magnitude (FMM).

Main Methods:

• 20 healthy participants (8-71 yr) underwent non-weight-bearing and weight-bearing assessments.
• Clinical foot mobility indices were derived from caliper-based measurements.
• Radiographic indices (skin-based and osseous) were obtained from concurrent AP and lateral radiographs.
• Bland and Altman analysis was used to assess agreement between measures.

Main Results:

• Clinical measures yielded significantly higher foot mobility indices (20%-250%) compared to radiographic and osseous measures (P < 0.01).
• Significant proportional bias was observed between clinical and radiographic measures.
• Osseous movement contributed variably (4%-87%) to skin-based mobility measures.
• Limits of tolerance for clinical and radiographic measures were generally larger than osseous movement.

Conclusions:

• Skin-based clinical and radiographic foot mobility measures are not interchangeable and are poor indicators of actual osseous mobility.
• The significant variability and bias highlight limitations of current skin-based clinical assessments.
• Further research into osseous measures is suggested, with a strong caution against relying on skin-based clinical foot mobility data.