Effect of 3D printed insoles for people with flatfeet: A systematic review.

This systematic review aimed to evaluate custom-made 3D printed insoles for people with flatfeet. PubMed, Embase, ISI web of knowledge, ProQuest, Scopus, and Cochrane databases, were searched from inception until January 2022. The quality assessment of included studies was performed through the Downs and Black checklist. A narrative analysis was performed since a meta-analysis could not be conducted. Ten studies including 225 subjects with flexible flatfeet were chosen for final evaluation. Although the evidence from selected literature was generally weak, using insoles with 3D printing technology may positively affect pain (comfort score) and foot function, with no significant change in vertical loading rate during walking or running. There were discrepancies among studies for plantar pressures, center of pressure trajectories, 3D ankle joint kinematics and kinetics of gait while wearing these insoles. Dose-response effects of medial posting on 3D printed insoles suggested beneficial effects on lower limb gait biomechanics in people with flatfeet. There was insufficient evidence to conclude the comparison between 3D printed insoles and other types of insoles. In conclusion, using a 3D printed insole may improve comfort score and foot function in people with flatfeet.

Association of arch height with ankle muscle strength and physical performance in adult men.

Differences in arch height may have a certain impact on lower extremity muscle strength and physical performance. However, there is little evidence from investigation of the possible correlation of arch height with ankle muscle strength and physical performance measures. Sixty-seven participants took part in this study. Arch height index (AHI) was assessed and categorized using a 3-dimension foot scanner. Ankle muscle strength was measured employing a dynamometer. Physical performance measures including agility, force and proprioception were randomly tested. Compared to the medium AHI, the high AHI had lower plantarflexion and inversion peak torque. The high AHI also had lower peak torque per body weight value for plantarflexion and inversion at 120°/s (P = 0.026 and 0.006, respectively), and dorsiflexion at 30°/s (P = 0.042). No significant ankle muscle strength difference was observed between the low and medium AHI. Additionally, AHI was negatively correlated with eversion and inversion peak torque at 120°/s, and negatively associated with plantarflexion, eversion and inversion peak torque per body weight at both 30°/s and 120°/s (r ranged from -0.26 to -0.36, P values < 0.050). However, no significant relationship was found between arch height and physical performance measures. The results showed that high arches had lower ankle muscle strength while low arches exhibited greater ankle muscle strength. Arch height was negatively associated with ankle muscle strength but not related to physical performance. We suggest that the lower arch with greater ankle muscle strength may be an adaptation to weight support and shock absorption.

Gender Differences in Adult Foot Shape with 3D Foot Scanner

OBJECTIVE: To analyze gender differences in adult foot shape with 3D foot scanner METHOD: Subjects included 1,107 feet of 872 healthy volunteers (male: 325, female: 547) without foot deformity. Total 23 foot parameters (foot length, inside joint length, outside joint length, ball girth, ball width, grading point length, vamp height, vamp length, waist girth point length, waist point length, waist height, waist girth, instep girth point length, instep point length, instep height, instep girth, short heel girth, long heel girth, throat opening, vamp waist angle, waist instep angle, instep-vamp height ratio, instep- ball girth ratio) were measured with 3D foot scanner. Univariate t-test was used to assess significant differences between men and women for each foot parameter, standardized to stature and foot length. RESULTS: For a given stature, 20 of 23 foot parameters were greater in men than women (p<0.05). For a given foot length, 13 of 23 foot parameters were greater in men than women (p<0.05). CONCLUSION: This study demonstrated that female feet were different from male feet in a number of shape characteristics. These differences should be taken into account in the manufacture of women's shoes.

Change of Foot Measurements with Weight Bearing by 3-D Foot Scanner

OBJECTIVE: To evaluate the influence of weight-bearing on foot shape measured by 3-D foot scanner. METHOD: Forty-two feet of twenty-one normal subjects were studied. The foot length, width, girth and arch parameters under non weight-bearing and weight-bearing conditions were measured by 3-D foot scanner (Nexcan(R), K & I, Korea), analysis software (EnFOOT(r), K & I, Korea) and 3-D foot arch measurement program. RESULTS: The foot length, ball width, ball girth, waist girth, instep girth, short heel girth, long heel girth and length from heel point to proximal arch point significantly increased under weight-bearing condition (p<0.01). However, vamp height, waist height, instep height, length of arch, height of arch, width of arch, length from heel point to distal arch point, maximal arch height and volume of arch were significantly decreased under 50% weight-bearing condition (p<0.01). CONCLUSION: Foot parameters associated with length, width and girth increased but volume, width, length, and height of medial longitudinal arch decreased under weight bearing condition. We suggest that these findings under weight- bearing condition result from the pronation of subtalar joint and the decrement of heights of transverse and longitudinal arch heights.

Three Dimensional Analysis of the Medial Longitudinal Arch of Foot

OBJECTIVE: To evaluate and quantify the medial longitudinal arch of foot using a 3-D foot scanner and 3-D arch measurement program. METHOD: 997 subjects (363 men and 634 women) were selected. The foot length, width, girth and medial longitudinal arch parameters were measured with a 3-D foot scanner (Nexcan(r), K&I, Korea), analysis software (EnFOOT(R), K&I, Korea) and 3-D measurement program of the medial longitudinal arch. RESULTS: The mean arch lengths were 100.3 mm for men, 90.4 mm for women. The mean arch height and arch volume in both genders were 14.7 mm, 12.1 mm and 10.3 cm3, 6.0 cm3, respectively. We compared the arch parameters of both genders by univariate analysis of variance and in most cases the parameters of men were larger than those of women. Moderate positive relationships were found between foot length and arch width of talonavicular joint in cases of men, foot length and length from heel point to distal arch point in both genders (Pearson correlation coefficient > 0.3, p<0.01). CONCLUSION: We evaluated the medial longitudinal arch of Korean feet three dimensionally. These data sould be a useful reference for making shoes, insoles, and orthoses.