SLR - June 2016 - Steve Huynh

An Ankle-Foot Orthosis with a Lateral Extension Reduces Forefoot Abduction in Subjects with Stage II Posterior Tibial Tendon Dysfunction

Reference: Neville C, Bucklin M, Ordway N, Lemley F. An Ankle-Foot Orthosis with a Lateral Extension Reduces Forefoot Abduction in Subjects with Stage II Posterior Tibial Tendon Dysfunction. J Orthop Sports Phys Ther, 2016 Jan; 46(1):26–33.  

Scientific Literature Review

Reviewed By: Steve Huynh, DPM
Residency Program: Wyckoff Heights Medical Center

Podiatric Relevance: Conservative care has been suggested for treatment of stage II PTTD, including the use of orthotic devices. Orthotic designs vary from in-shoe foot orthoses to more aggressive AFOs. The goal for using an orthotic device is to correct forefoot abduction or unload the tibialis posterior tendon and support structures, such as the spring ligament. The purpose of this study was to test a lateral-extension component in controlling foot kinematics (specifically, forefoot abduction) in participants with stage II PTTD while walking. It was hypothesized that an AFO with a lateral extension would be associated with a greater decrease in forefoot abduction compared to a standard AFO design and using shoes without any device.

Methods: The study included 15 patients with a diagnosis of stage II PTTD; each participant was casted for custom standard AFOs and AFOs with a lateral extension component. Every patient underwent a series of walking trials by attaching marker triads with a 12-camera motion-analysis system to test each of the two AFOs and with shoe-only condition in random order. The velocity of each participant was maintained within 5 percent using an infrared timing system for all walking trials. This allowed comparison between the two AFOs and shoe-only condition at a constant velocity for this repeated measures study. The kinematic data included hindfoot inversion/eversion, forefoot plantar flexion/dorsiflexion and forefoot abduction/adduction during the gait cycle.

Results: A lateral-extension component added to a standard AFO corrected forefoot abduction by an average of 4.1° compared to not wearing an AFO, with a shoe only, and by 2.6° compared to a standard AFO without the lateral-extension component. In addition, the two AFOs resulted in greater hindfoot inversion and forefoot plantar flexion compared to the shoe-only condition at loading response. There was no statistically significant difference between the two AFOs in frontal and sagittal plane changes.

Conclusions: The article implies the modified AFOs with a lateral-extension should be considered to improve the correction of flexible flatfoot abduction with stage II PTTD. AFOs with or without the lateral-extension appear to assist equally in frontal and sagittal plane correction. In clinical practice, UCBL and ISDS are often prescribed to treat pediatric flexible flatfoot deformity; and functional UCBLs are also prescribed for treatments of stage II PTTD adult patients; however, the limitation of the study did not compare foot kinematics between AFOs with a lateral-extension with different UCBLs that are also used to treat stage II PTTD pediatrics and adult patients. Further studies are needed to compare foot kinematics between AFOs with a lateral-extension and existing CFOs.

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