Abstract
BackgroundMetatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH) that causes pain. The high pressure under the MH can be reduced by adequately applying metatarsal pads (MPs). Plantar pressure measurements may provide a method to objectively evaluate pressure loading under the MH. However, it is still unclear if the decrease in plantar pressure under the MH after MP treatment is associated with subjective improvement. This study aims to explore the correlations between subjective pain improvement and outcome rating, and the plantar pressure parameters in metatarsalgia patients treated using MPs.MethodsThirteen patients (a total of 18 feet) with secondary metatarsalgia were included in this study. Teardrop-shaped MPs made of polyurethane foam were applied just proximal to the second MH by an experienced physiatrist. Insole plantar pressure was measured under the second MH before and after MP application. Visual analog scale (VAS) scores of pain were obtained from all subjects before and after 2 weeks of MP treatment. The subjects rated using four-point subjective outcome scales. The Wilcoxon signed-rank test was used to analyze the difference between the plantar pressure parameters and VAS scores before and after treatment. The Kruskal-Wallis test was applied to compare the plantar pressure parameters in each outcome group. Pearson's correlation was applied to analyze the correlation between the changes in plantar pressure parameters and VAS scores. Statistical significance was set as p < 0.05.ResultsMP application decreased the maximal peak pressure (MPP) and pressure-time integral (PTI) under the second MH and also statistically improved subjective pain scores. However, neither the pre-treatment values of the MPP and PTI shift in the position of the MPP after treatment, nor the age, gender and body mass index (BMI) of the subjects were statistically correlated with subjective improvement. Declines in the PTI and MPP values after MP application were statistically correlated with the improvement in VAS scores (r = 0.77, R2 = 0.59, p < 0.001; r = 0.60, R2 = 0.36, p = 0.009).ConclusionWe found that the successful decline in the PTI and MPP under the second MH after MP application was correlated to subjective pain improvement. This study provides a strategy for the further design and application of MPs for metatarsalgia treatment.
Highlights
Metatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH) that causes pain
We found that the declines in the pressure-time integral (PTI) and maximal peak pressure (MPP) under the MH after metatarsal pads (MPs) application correlated with significant pain improvement
We found that the decline in the PTI value after MP placement correlated well with that in the Visual analog scale (VAS) scores, while the decline in the MPP value correlated moderately (r = 0.77, R2 = 0.59 versus r = 0.60, R2 = 0.36)
Summary
Metatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH) that causes pain. Primary metatarsalgia is mainly related to repetitive pressure loading under the MH, which exceeds the focal tissue tolerance and leads to inflammation and pain [1,2,5] Many conditions such as pes cavus, pes planus, hyperpronated feet, hallux valgus and claw/hammer toe will increase pressure loading under the MH. In another way, fat pad atrophy, properties change (in DM or RA) or displacement (in claw/hammer toes) will decrease the tolerance of the tissue under the MH to the pressure loading. Fat pad atrophy, properties change (in DM or RA) or displacement (in claw/hammer toes) will decrease the tolerance of the tissue under the MH to the pressure loading This disequilibrium in biomechanics is associated with metatarsalgia [2,3]. Besides pressure loading under the MH, the pathomechanism that includes an abnormal inflammation process, neuropathy, fat pad atrophy, etc. is more complex in secondary metatarsalgia
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