Evaluating Thumb Abduction Measurement Methods in Carpometacarpal Osteoarthritis

Overview

This study assessed the validity, reliability, and precision of intermetacarpal distance (IMD) measurement methods using tape and calipers to evaluate thumb palmar and radial abduction in individuals with carpometacarpal osteoarthritis (CMC1 OA). Findings demonstrated that both tape and caliper IMD methods provide reliable and valid measures, with improved reliability when averaging multiple trials.

Background

Thumb carpometacarpal joint osteoarthritis is a prevalent and symptomatic form of hand OA, especially in older women, characterized by decreased range of motion, pain, and functional limitations. Measuring thumb abduction is challenging due to the thumb's complex joint dynamics. Existing methods, including goniometry and technological tools, have variable reliability. The IMD method, particularly with calipers, has shown promise for radial abduction but lacks data for palmar abduction and tape measure use in CMC1 OA patients.

Data Highlights

Key Findings

• The tape measure IMD method was successfully adapted for assessing thumb palmar abduction in individuals with CMC1 OA.
• Both tape and caliper IMD methods demonstrated acceptable to excellent test–retest reliability for measuring thumb palmar and radial abduction.
• Using the mean of two or three trials improved measurement reliability compared to a single trial for both IMD methods.
• Construct validity of the IMD methods was supported, indicating these measures reflect functional thumb abduction ability in CMC1 OA.
• Placement of the tape on the dorsal surfaces of the 1st and 2nd metacarpal heads may introduce error due to joint enlargement; alternative approaches were developed to mitigate this.

Clinical Implications

Clinicians can reliably use the tape measure IMD method as a practical alternative to calipers for assessing thumb palmar and radial abduction in patients with CMC1 OA. Averaging multiple trials enhances measurement precision, supporting its use in monitoring disease progression and treatment efficacy. Careful tape placement is essential to avoid measurement errors related to joint swelling.

Conclusion

The study validates the use of tape and caliper IMD methods for reliable and accurate measurement of thumb abduction in CMC1 OA, with improved reliability when averaging multiple trials. These methods provide valuable tools for clinical assessment and monitoring of thumb function in this population.

References

1. References 1-24 as cited in source article