CHARACTERISTICS OF INTRINSIC FOOT MUSCLE AND PLANTAR FASCIA MORPHOLOGY IN ADOLESCENTS - COMPARISON WITH ADULTS

S. Arima¹, N. Maeda¹, M. Komiya¹, S. Tsutsumi¹, H. Ishihara¹, Y. Ikuta^2,3, Y. Mikami⁴, Y. Urabe¹

¹Hiroshima University, Department of Sports Rehabilitation, Graduate School of Biomedical and Health Sciences, Hiroshima, Japan, ²Hiroshima University Hospital, Department of Orthopedic Surgery, Graduate School of Biomedical and Health Sciences, Hiroshima, Japan, ³Hiroshima University Hospital, Department of Rehabilitation, Hiroshima University Hospital, Hiroshima, Japan, ⁴Hiroshima University Hospital, Department of Rehabilitation, Hiroshima, Japan

Background: The foot arch is important for the foot to absorb shock while weight bearing loads (Josh et al., 2006). The plantar fascia maintains the foot arch as a static support mechanism and the intrinsic foot muscle as a dynamic support mechanism. Although the foot arch growth matures around the age of 12, it has been reported that there are some cases of the incomplete formation of the foot arch even later in adolescence. (Oda et al., 2009). To resolve the foot problems in adolescents, it will be necessary to characterize the intrinsic foot muscle and plantar fascia in adolescents. However, there have been no reports comparing the intrinsic foot muscle and plantar fascia morphology of adolescents with those of adults.

Purpose: This study aimed to clarify the characteristics of intrinsic foot muscle and plantar fascia morphology in adolescents by comparing those morphology of adolescents and adults.

Methods: The subjects were adolescents (24 males, 13.8±0.7 y.o.; 18 females, 13.6±1.1 y.o.) and adults (20 males, 24.6±2.8 y.o.; 18 females, 21.5±1.6 y.o.) right feet. The foot arch height ratio was calculated from the foot length and navicular bone height as an index of the foot arch. The cross-sectional area (CSA) and thickness of intrinsic foot muscle (the abductor hallucis, flexor digitorum brevis, and flexor hallucis brevis), as well as the thickness of the plantar fascia, were measured using an ultrasound imaging system (HI Vision Avius; Hitachi Aloka Medical, Tokyo, Japan). Height, body weight, foot length, the foot arch height ratio, and intrinsic foot muscle and plantar fascia morphology were compared between adolescent and adult subjects by gender with unpaired t-test.

Results: Foot length did not differ between adolescents and adults for both sexes. Height, body weight, and the foot arch height ratio were significantly lower in adolescents of both sexes (p<0.05). In the intrinsic foot muscle morphology, only CSA and thickness of the flexor hallucis brevis were significantly lower in adolescents of both sexes (p<0.05).

Conclusions: Foot length growth almost stops around 14 y.o. in males and 12 y.o. in females (Masuyama et al., 2012). Since the foot matures earlier than height and body weight, we infer that there were no marked differences in foot length or in the morphology of most foot intrinsic muscle and plantar fascia between adolescents and adults. Only the flexor hallucis brevis had smaller CSA and thickness in the adolescents. The flexor hallucis brevis plays an important role in maintaining the foot arch (Latey et al., 2018), suggesting that the characteristics of the flexor hallucis brevis morphology may be related to the incomplete formation of the foot arch.

Implications: Although the intrinsic foot muscle and plantar fascia morphology of the adolescent may not differ markedly from that of the adult, strengthening the flexor hallucis brevis and increasing the foot arch height are likely to be necessary.

Funding acknowledgements: We have no funding acknowledgment in this study.

Keywords:
Adolescent
Intrinsic foot muscle
Foot arch

Topics:
Sport & sports injuries
Musculoskeletal: lower limb
Disability & rehabilitation

Did this work require ethics approval? Yes

Institution: Hiroshima University

Committee: The Ethical Committee for Epidemiology of Hiroshima University

Ethics number: E-941