Hallux valgus is a progressive foot deformity characterized by a lateral deviation of the hallux with corresponding medial deviation of the first metatarsal. Late-stage changes may render the hallux painful and without functional utility, leading to impaired gait. Various environmental, genetic, and anatomical predispositions have been suggested, but the exact cause of hallux valgus is unknown. Evidence indicates that conservative intervention for hallux valgus provides relief from symptoms but does not reverse deformity. Part 1 of this perspective article reviews the literature describing the anatomy, pathomechanics, and etiology of hallux valgus. Part 2 expands on the biomechanical initiators of hallux valgus attributed to the first metatarsal. Theory is advanced that collapse of the arch with vertical orientation (tilt) of the first metatarsal axis initiates deformity. To counteract the progression of hallux valgus, we use theory to discuss a possible mechanism by which foot orthoses can bolster the arch and reorient the first metatarsal axis horizontally.

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.

The hypermobile first ray has been implicated as contributing to the cause and progression of hallux valgus deformity. Deformity of the hallux is often accompanied by an enlarged first intermetatarsal (IM 1-2) angle. It has been hypothesized that subjects having an abnormally large IM 1-2 angle have laxity of the first ray. Objectives of this study were to compare dorsal mobility of the first ray in subjects with hallux valgus to asymptomatic controls, and to investigate the relationship between dorsal mobility and the IM 1-2 angle. Fourteen subjects (age 23-81) with hallux valgus were matched by gender and age to control subjects. The IM 1-2 angle was measured from radiographs. A load-cell device measured dorsal mobility of the first ray under a standard load of 55 N. Pearson's correlation coefficient identified a marginal correlation (r = .51) between IM 1-2 angle and dorsal mobility. An independent t-test showed a statistically (P < 0.01) larger amount of dorsal mobility in the group of subjects having hallux valgus. Mobility of the first ray was increased in subjects with hallux valgus and a large IM 1-2 angle may be an indicator of increased dorsal mobility.

There were group differences. Eversion of the calcaneus and adduction of the first ray were increased, and the first-ray axis was inclined 24 degrees over middle stance in women with deformity compared with 6 degrees in control participants. Results may identify risk factors of hallux valgus and inform nonoperative treatment (orthoses, exercise) strategies.

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The need for measuring the mobility of the first ray has been identified. The purpose of this study was to test the reliability and validity of a device built to measure the relative vertical displacement of the first ray. Twenty fresh frozen cadaver feet were sampled (mean age of donor was 70+/-13 years). Dorsal mobility of the first ray was measured by device over three trials of repeated loading using 20 N, 35 N, 55 N and 85 N of force. Radiographs served as the criterion standard for validation of the device. Vertical displacement was measured from x-ray by a digitizing procedure that recorded movement of the first ray during loading. Reliability of the device assessed by intraclass correlation coefficients (ICC) was .98 with standard errors of the measurement calculated to be 0.35 mm. A correlation of agreement value of .97 was determined for the two methods of measurement. Analysis of variance testing found a significant interaction between force and method of measurement. Tukey post-hoc analysis found no difference (F<1.70) between the two methods of measuring first ray displacement in cadaver specimens when the force applied did not exceed 55 N. At 85 N of force (F = 10.05), unwanted movement of the second metatarsal caused the device to overestimate the amount of displacement that occurred specific to the first ray. This measure of first ray mobility should help clinicians and researchers to better investigate foot pathology resulting from faulty mechanics of the first ray.

Objective. The first ray plays a role in the development of bunion foot deformity, but for unknown reasons. This prospective, cross-sectional study investigated first ray kinematics in women with rheumatoid arthritis (RA) and bunion. Methods. Nine participants having RA-bunion were analyzed in comparison to a control group (n ‫؍‬ 10). Data were acquired using a magnetic resonance scanner. Conditions were standardized to simulate gait midstance, heel off, and terminal stance. Foot posture (hallux angle, intermetatarsal angle, arch angle, and calcaneus angle) and relative first ray position angles/helical axis parameters registered across gait conditions were measured. An analysis of variance model compared data between groups and across conditions, and correlation assessed the relationship between selected variables. Results. Eversion of the calcaneus averaged 9°, and adduction of the first ray was increased (F ‫؍‬ 6.29, P ‫؍‬ 0.02) by >4.6°a cross conditions in the RA-bunion group. There was an interaction (F ‫؍‬ 7.73, P ‫؍‬ 0.01) for the first ray axis. Followup comparisons identified increased inclination of the first ray axis over middle stance compared to late stance in the group with RA and bunion. There was moderate correlation (r ‫؍‬ ؊0.42) between the calcaneus angle of eversion and inclination of the first ray axis. Conclusion. Optimal treatment for bunion has not been defined. This research identified calcaneus eversion and first ray adduction, as well as inclination of the first ray axis as risk factors of bunion. This result may inform the evaluation and treatment of bunion in women with RA.

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