Comparison of Two Methods Used to Assess First-Ray Mobility

Abstract

Mobility of the first-ray is associated with several common lower extremity disorders. However, the reliability and validity of clinical measurement remains unclear. In this study we examined first-ray mobility by using one hand to stabilize the lesser metatarsals while the clinician's other hand applied a displacement force to the head of the first metatarsal. The amount of mobility was graded as stiff, normal or hypermobile. We then used a well-validated mechanical device to perform similar tests and assessed validity, intrarater reliability and interrater reliability. Three clinicians having varied levels of experience graded first-ray mobility on 15 subjects. A separate investigator measured dorsal mobility with a mechanical device. Both methods of testing were repeated to assess measurement reliability. Reliability was estimated by kappa (K) statistics. Spearman correlation assessed the relationship between mobility graded manually and dorsal mobility measured by device. Manual examination intrarater K values ranged from 0.50 to 0.85, and interrater agreement from 0.09 to 0.16. Manual grading was not related (r = -0.21) to the absolute measure of total dorsal mobility made by device. This brings into question the validity and reliability of manual estimates of first-ray mobility.

Criterion-Related Validity of a Clinical Measure of Dorsal First Ray Mobility

“…Measurements of dorsal mobility in clinical populations typically range from 4 to 8 mm. 3,4,5 Measures recorded with the device were reliable, with an ICC equal to 0.98 and a SEM equal to 0.15 mm. An ICC gives comparison of 2 or more repeat measures.…”

“…12 A single examiner measured first ray dorsal mobility with the device (Figure 2). [3][4][5][6][7][8] The examiner (W.M.G.) operating the device was blinded from the results made with the rulers.…”

“…The device and protocol for testing are described elsewhere. [3][4][5][6][7][8] Measurements made with the device have been found to be reliable (ICCՆ 0.92; SEM Յ 0.35 mm), [3][4][5][6][7] and valid (ICC = 0.97), as judged by concurrent movement of the first ray as assessed with radiographs. 8 The device imposes a dorsiflexion force from beneath the first metatarsal head while measuring dorsal mobility of the first ray.…”

“…13,14 Glasoe et al 4 and more recently Cornwall et al 1 have questioned the diagnostic accuracy of this clinical test. Both groups of investigators found poor agreement between clinicianassessed ordinal-level hypomobile, normal, or hypermobile estimates of the first ray sagittal plane motion as compared to dorsal mobility measured by a mechanical device.…”

“…Both groups of investigators found poor agreement between clinicianassessed ordinal-level hypomobile, normal, or hypermobile estimates of the first ray sagittal plane motion as compared to dorsal mobility measured by a mechanical device. 1,4 Authors of clinical studies 9,10,12,15 have suggested ways to refine Morton's test procedure with intent to improve the measure. Grebing and Coughlin 9 found that motion available at the first ray is influenced by the position of the ankle and recommended that a neutral ankle position with the knee bolstered in slight flexion be adopted as the standard position of measurement.…”