Three recently published studies address the clinical effects and provision of orthoses. One study evaluated several foot orthotics as treatment for pressure from hallux valgus deformity, another assessed the ability of foot orthotics to restore function of the metatarsal phalangeal joint (MPJ) in patients with hallux limitus, and the third attempted to determine if the shank-to-vertical-angle (SVA) can be used as a parameter to evaluate the alignment of an AFO-footwear combination (AFO-FC).
Biomechanical Evaluation of Custom Foot Orthoses for Hallux Valgus Deformity, published online June 6 in The Journal of Foot & Ankle Surgery, compared the hallux valgus deformity pressure parameters seen in standard footwear with no orthotic and the pressure observed in the same footwear under three different orthotic conditions: full length, ¾ length, and sulcus length. The forefoot pressure at a hallux valgus deformity was recorded with pressure sensors placed on the plantar, medial, and dorsal surfaces of the first metatarsal head.
The study participants performed walking trials without an orthotic and then with a full-length, ¾-length, and sulcus-length orthotic. The average pressure and maximum pressure of each area was recorded for each orthotic condition, and comparisons were made across the groups.
According to the study’s authors, plantar pressures were decreased with use of the full-length and ¾-length orthotics, dorsal pressures were increased with the use of the full-length and sulcus-length orthotics, and significant changes in medial pressure were not seen with the addition of any orthotic compared with standard footwear alone. However, they wrote, a trend toward increased medial pressures was seen with the full- and sulcus-length orthotics, and the ¾-length orthotic condition exhibited a trend toward decreased medial pressures. While the researchers said they were unable to demonstrate that the use of a custom foot orthotic significantly decreases the medial pressures on the first metatarsal head in patients with hallux valgus deformity, they found that the ¾-length orthotic was less likely to negatively affect the dorsal or medial pressures, which were noted to increase with use of the sulcus- and full-length orthotic. Because of this, they suggested that if a clinician uses this treatment option, a ¾-length orthotic might be a better choice than a sulcus- or full-length orthotic.
The next study, published June 10 online before print in Prosthetics and Orthotics International, measured whether custom-made foot orthotics increased the range of mobility (ROM) of the MPJ in patients with hallux limitus. The study cohort consisted of 20 participants (40 feet) diagnosed with hallux limitus. A control group and an experimental group wore the same custom-made foot orthotics; in the experimental group a support element under the first MPJ was added to the orthotics.
Two measurements were taken with both groups: the relaxed position of the first MPJ and the maximum extension of the hallux. These measurements were taken before use of the foot orthotics and again six months after application of the treatment. According to the study’s authors, the results for the experimental group showed an improvement of 4.5 degrees in the relaxed position and 22.2 degrees in the maximum extension, statistically significant for both measurements, and demonstrating that the use of the foot orthotics designed in the study restored ROM of the first MPJ.
The third study, published online May 27 in Gait and Posture, evaluated effects of adjustments often used to tune AFOs. The authors, noted that the effectiveness of an AFO-FC may partly depend on the alignment of the ground reaction force with respect to lower-limb joint rotation centers, reflected by joint angles and moments. Further, adjusting, (i.e., tuning) the AFO-FC’s properties could affect the alignment, which may be guided by monitoring the SVA. Thus, the research looked into how monitoring the SVA can be used to evaluate the tuning of an AFO-FC, and whether, during walking, the SVA responds to variations in heel height and footplate stiffness. The study also measured whether heel height and footplate stiffness would reflect changes in joint angles and net moments in healthy adults.
Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral, rigid AFOs. The AFO-FC heel height was increased to impose an SVA of 5 degrees, 11 degrees, and 20 degrees, and combined with a flexible or stiff footplate. For each trial, the SVA, joint flexion-extension angles, and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The SVA significantly increased with increasing heel height, resulting in an increase in knee flexion angle and internal knee extensor moment. The authors found that the stiff footplate reduced the effect of heel height on the internal knee extensor moment, while the internal ankle plantarflexion moment increased, and effects of heel height and footplate stiffness on the hip joint were limited.
The authors said that the results support the potential to use the SVA as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower-limb angles and moments.