The Effect of Arch Height and Body Mass on Plantar Pressure

Carine HM van Schie, MSc, PhD; , Andrew JM Boulton, MD, FRCP

Disclosures

Wounds. 2000;12(4) 

In This Article

Discussion

The results of the present study indicate that there is a trend towards greater medial pressure loading in subjects with low-arched feet. However these trends did not reach statistical significance, probably due to the large variability of pressure measurements in general. In addition, it was demonstrated that subjects with a lower arch, as measured with the arch index, have a greater BMI. This suggests a causal link between higher body mass and increased flattening of the arch of the foot during walking.

Our results agree with those of Atkinson-Smith and Betts,[13] Bevans,[34,35] Song and Hillstrom,[14] and Mueller, et al.[36] All these authors report on the effect of foot type on dynamic foot function and thereby the site of foot ulcer and callus formation. In the present study, only weak associations were observed between a low arch and more medially loading of the foot during walking; however, the trends observed do support the theory that foot pressures are affected by foot structure.

Morag and Cavanagh[11] and Cavanagh, et al.,[12] provided contradictory findings compared to the present study. Their results indicated that a high arch was associated with higher peak pressure at the first MTH, as a positive correlation was observed between metatarsal inclination and peak pressure at the first MTH (r = 0.37). These results are contradictory to the finding in the present study of a weak positive association between arch index and peak pressure at the first MTH, which indicates that lower-arched feet have higher pressures. The only explanation for the discrepancy of results could be that different study populations have been assessed in the last two mentioned studies. In fact, these were the only two studies that limited the investigations to normal non-pathological feet. Perhaps within a group of subjects with normal aligned feet there is a positive relationship between arch height and peak pressure at first MTH.

The suggestion that a greater foot surface could be associated to lower foot pressures appears completely unfounded. Even more so after the observation of an inverse relation between peak pressure at first MTH and the ratio height/foot surface (r = -0.44, p<0.05), indicating that higher peak pressures are associated with a smaller ratio height/foot surface (i.e., a relatively larger foot surface).

The effect of body mass on peak plantar pressure was significant, although only explaining around 16 percent of the variance of peak pressure under the foot and several MTH regions of the foot. The strength of association observed in this study agrees with previous reports from Soames[18] and from Cavanagh, et al.,[15] and is slightly higher than reported by Ahroni, et al.[5] Although body mass may not have a major effect on plantar pressure, it is reasonable to assume that a higher body mass should cause higher foot pressures within a given foot structure compared to a lower body mass. This concept has been investigated by Vela, et al.,[37] who assessed foot pressures of healthy subjects without added weight and with an additional 9.1 and 18.2 kg. The results of this study do support the theory that an increase in weight does increase plantar foot pressures. It also indicates that within overweight subjects, a loss of body weight should result in lower plantar foot pressures.

To summarize, arch height of the foot did have a small effect on dynamic plantar pressure. The association observed does support the general belief that low-arched feet have higher pressures on the medial side of the foot, as reported by the majority of studies investigating this issue. In addition, subjects with a lower arch (higher arch index) appeared to have a greater BMI. The significant association between body mass and plantar pressure is in agreement with the observed association between BMI, arch index and foot pressures. To conclude, arch height and body mass have a significant but small effect on peak plantar pressure. The effect of arch height on plantar pressure can possibly be explained by the effect of BMI on arch height during weight bearing.

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