Abstract
BackgroundThere currently are no recommended standards for reporting kinematics of the first-metatarsophalangeal joint. This study compared 2 different rotation sequences of Cardan angles, with implications for understanding the measurement of hallux valgus deformity.MethodsThirty-one women (19 hallux valgus; 12 controls) participated. All were scanned in an open-upright magnetic resonance scanner, their foot posed to simulate the gait conditions of midstance, heel-off, and terminal stance. Using computer processes, selected tarsals were reconstructed into virtual bone models and embedded with principal-axes coordinate systems, from which the rotation matrix between the hallux and first metatarsal was decomposed into Cardan angles. Joint angles were then compared using a within factors (rotation sequence and gait condition) repeated-measures analysis of variance (ANOVA).ResultsOnly the transverse plane-first sequence consistently output incremental increases of dorsiflexion and abduction across gait events in both groups. There was an interaction (F ≥ 25.1; p < 0.001). Follow-up comparisons revealed angles were different (p < 0.05) at terminal stance.ConclusionsDifferent rotation sequences yield different results. Extracting the first rotation in the transverse plane allows for the resting alignment of the hallux to deviate from the sagittal plane. Therefore, representing first-metatarsophalangeal joint kinematics with the transverse plane-first rotation sequence may be preferred, especially in cases of hallux valgus deformity.
Highlights
There currently are no recommended standards for reporting kinematics of the first-metatarsophalangeal joint
Regardless of group or sequence, dorsiflexion increased across gait conditions
Abduction increased an average of 5° from MS to terminal stance (TS), and about 20° from heel off (HO) to TS in both groups when angles were represented with the transverse-first sequence, but not when represented with the sagittal plane-first sequence (Figure 4)
Summary
There currently are no recommended standards for reporting kinematics of the first-metatarsophalangeal joint. Cardan angles are quantified as ordered rotations about 3 axes, and represent joint motion displacements in the anatomical body planes. Foot dorsiflexion/plantar flexion joint rotations occur about the mediolateral-axis in the sagittal plane; inversion/eversion about the longitudinal-axis in the frontal plane; adduction/abduction about the vertical axis in the transverse plane. Research describing 1-MTP joint with Cardan angles compute frontal plane (in/eversion) motion as the last order-of-rotation [6,7,8,9,10,11]. There is no consensus, on whether the first order-of-rotation should be computed in sagittal plane (dorsi/plantar flexion) [6,7] or the transverse plane (add/abduction) [10,11], especially in people with hallux valgus foot deformity [12]
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