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Foot Shape and Its Effect on Functioning in Royal Australian Air Force Recruits. Part 1: Prospective Cohort Study

Military Medicine, Jul 2005 by Esterman, Adrian, Pilotto, Louis

Objective: To determine whether foot shape (flat, normal, or cavus feet) affects functioning among military recruits. Methods: A total of 230 Royal Australian Air Force recruits embarking on a 10-week basic training course took part in a prospective cohort study of foot shape and its effect on functioning. Recruits were divided into three groups based on their foot shape, i.e., flat feet (n = 22), normal feet (n = 139), and cavus feet (n = 44), with the diagnosis being made from the arch index measured from their footprints. The groups were assessed at baseline and week 8. Outcome measures included pain, injury, foot health, and quality of life. Results: There were no significant differences in outcome measures at baseline. At the end of the trial, foot shape was not related to injury. The flat feet group had significantly poorer subjective physical health than did the normal feet group (p = 0.001). Conclusion: This study provides high-level evidence that foot shape has little impact on pain, injury, and functioning among military recruits.

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Introduction

Since the inception of the Australian Defence Force (ADF) and well before that in the British, U.S., and many other armed forces, having flat feet has disqualified people who wished to enlist. However, there is little in the way of documentary evidence regarding how these restrictions arose and what the consequences of accepting recruits with flat feet are.

Four previous articles that primarily examined foot shape and injuries incurred during military training have been published. The first two articles referred to an Israeli study that took place in 1983. This was a prospective cohort study of military recruits from selected combat units undertaking 14 weeks of basic training. In the first article, the diagnosis of foot shape was a clinical judgment made by a qualified orthopedic surgeon.' Stress fractures were separately recorded as being tibial, femoral, or metatarsal. The authors demonstrated a strong (and statistically significant) protective effect of flat feet against stress fractures. They indicated (but provided no data) that the same pattern was seen for femoral and tibial stress fractures and stress fractures overall. The authors made no attempt to measure or adjust for potential confounding variables.

The second article concentrated on the fact that 143 of the 295 recruits were provided at random with military stress orthotics.2 Interestingly, this was not mentioned in the earlier article that described the same study. Rather than use the subjective assessment of foot shape made by the orthopedist, the authors used three foot shape parameters measured from the foot X-rays, namely, calcaneal angle, forefoot angle, and arch height/foot length ratio. The authors used feet rather than individuals for the analysis, because they found that the calcaneal angle differed significantly between left and right feet and many of the stress fractures were unilateral. The authors found that, using the calcaneal angle as the measure of foot shape, the high-arched group was six times more likely to have received a femoral stress fracture than the low-arched group and was nearly twice as likely to have received a tibial stress fracture. However, the reverse was seen with metatarsal stress fractures, with the low-arched group being three times more likely to have received a stress fracture. Unfortunately, when the authors examined the other two measures of foot shape, with the exception of a higher incidence of metatarsal stress fractures in the lowarched group, defined by the arch height/foot length ratio, they did not find similar patterns of relative risk (RR).

A similar study was undertaken several years later with U.S. Army trainees undergoing a 12-week training program.3 The authors measured foot shape with several different parameters based on a photograph of the right foot. The authors found that, for all seven foot shape parameters measured, cavus feet (defined as the lowest quintile) consistently had the highest injury rate, followed by normal feet and finally flat feet (defined as the highest quintile), with the lowest rate. Of the seven foot shape parameters measured, the authors used the bony arch index (AI) (the navicular height/foot length ratio) in multivariate analyses, because it had the strongest association with injury at the univariate level. After adjustment for potential confounding variables, flat feet were a statistically significant protective factor against injury, whereas cavus feet were a statistically significant risk factor.

The final study by Kaufman et al.4 involved 449 male U.S. Navy Seals who had already undertaken fitness training and were completing a 25-week advanced course. The authors used a variant of the AI described by Cavanagh and Rodgers,5 as well as several other measures to define foot shape. Injuries were divided into stress fractures, periostitis, iliotibial band syndrome, patellofemoral syndrome, and Achilles tendinitis. Medical staff members were trained to standardize diagnoses. They found that both cavus and flat feet were associated with a higher risk of injury. However, no attempt was made to adjust for confounding variables, and the aforementioned findings were not statistically significant.

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Foot Shape and Its Effect on Functioning in Royal Australian Air Force Recruits. Part 1: Prospective Cohort Study

Military Medicine, Jul 2005 by Esterman, Adrian, Pilotto, Louis

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