The mechanical properties of the heel pad in unilateral plantar heel pain syndrome

Plantar heel pain syndrome has been attributed to entrapment neuropathy, pl antar fasciitis, calcaneal spurs, and stress fractures of the calcaneus, Al though deteriorated mechanical properties of the heel pads may play an impo rtant role in the pathogenesis of heel pain syndrome, this has received lit tle notice, In this study, a specially designed compression relaxation devi ce with a push-pull scale and a 10-MHz linear array transducer was used to determine thickness of the heel pad under different loading conditions, Twe nty consecutive patients aged 29 to 77 years with unilateral plantar heel p ain syndrome were enrolled. Thickness of heel pad bilaterally was measured when the heel pad was compressed by serial increments of 0.5 kg to a maximu m of 3 kg and then relaxed sequentially, The load-displacement curve during a loading-unloading cycle was plotted, and the compressibility index and e nergy dissipation ratio of the heel pad were calculated accordingly, Phase I displacement of the heel pad (from 0 to 1 kg load) on the painless side w as greater than that on the painful side (P < 0.01), but there was no stati stically significant difference between painless and painful sides in thick ness of unloaded heel pads, compressibility index, or energy dissipation ra tio (P > 0.05), In conclusion, the affected heel pad in plantar heel pain s yndrome was stiffer under light pressure than the heel pad on the painless side. The changed nature of chambered adipose tissue in a painful heel pad may be responsible for its increased stiffness under light pressure.