SLR - January 2021 - Jacob R. Bolling

Segmental Foot and Ankle Kinematic Differences Between Rectus, Planus, and Cavus Foot Types

Reference: Kruger K.M., Graf A., Flanagan A., et. al.: Segmental Foot and Ankle Kinematic Differences Between Rectus, Planus, and Cavus Foot Types. J. Biomech. 2019. 

Level of Evidence: 3

Scientific Literature Review

Reviewed By: Jacob R. Bolling, DPM
Residency Program: Saint Vincent Hospital – Worcester, MA 

Podiatric Relevance: This article looks into documenting the different biomechanical dynamics of the three main foot types that podiatrists work with every day: Cavus, Rectus and Planus foot types. Each foot type comes with its own challenges, and can also lead to new deformity developments, like hallux limitus in planus foot types or claw toe deformities in cavus foot types. The purpose of the study was to develop a consensus on segmental foot kinematic data among healthy adult individuals with rectus, cavus and planus foot types.

Methods: The study included 33 volunteer subjects who reported no symptoms or history of foot problems. Foot types were evaluated based on measuring the resting calcaneal stance position (RCSP) and confirmed with static weightbearing radiographs. Eleven people were assigned to each group of Cavus, Rectus and Planus foot types. Each subject participated in an instrumented gait analysis, including segmental foot analysis, using the Milwaukee Foot Model  (MFM). Subjects also had weight-bearing radiographic films taken of the foot in AP, Lateral and adjusted hindfoot projections while standing on the foot positioning template. Vicon’s Nexus software was used in the clinical gait analysis, and the average numbers for the kinematic curves was used for the purposes of the analysis of this study. The study utilized the analysis of variance (ANOVA), omnibus F-test, pair-wise comparisons using Tukey-HSD, and the method of LAAST.

Results: The overall movement of the tibia, hindfoot and forefoot were analyzed and documented in the sagittal, transverse and coronal planes. Only minor differences were identified in the sagittal and coronal planes in the tibia. No differences were identified between Rectus and Planus Groups in regards to the tibia. In the coronal plane, the hindfoot of the Rectus Group showed significant change in the hindfoot. Significant differences were found between the three foot types in the sagittal, coronal and transverse planes between the different foot types. As for the forefoot data, significant changes were seen in the sagittal, transverse and coronal planes between each of the foot types as well. 

Conclusions: The purpose of the study was to develop a consensus on segmental foot kinematic data among healthy adult individuals with rectus, cavus and planus foot types. The study was limited in that only 11 subjects within a limited age group for each foot type were analyzed with three trials per subject being analyzed. The authors believe the MFM is limited in its capacity to analyze hindfoot motion as it combined the motion in the talocrural and subtalar joints, of which future studies can investigate these differences. This provides a baseline for patients that have these foot types but do not yet show symptoms, and may aid in prevention planning of such symptoms. 

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