Development of a clinical instrument to measure heel pad indentation

Objective. To provide an accurate, reliable, non-invasive, portable instrum ent to measure heel pad indentation in a clinical setting. Design A novel instrument was applied to assess heel pad indentation. Background For the lack of quantitative biomechanical tools for in vivo ass essment, palpation is used to evaluate heel pad stiffness subjectively in e veryday clinical practice. Furthermore. previous studies have evaluated hee l pad stiffness using non-portable instrumentation. Methods. Cylindrical probe was attached to an electronic force gauge unit t hat passed through a Perspex plate for placement on heel pad. Displacement of the plate was connected to a linear variable differential transformer. A laptop PC allowed for portability and storage of data. An exponential curv e described the force-displacement data. Ten healthy subjects (mean 21.7; S D, 1.7 years) were assessed on ten separate occasions. The procedure was st andardised for subject position and placement. Results. Accuracy and reliability of each device component was established. An intraclass correlation (2,1) of 0.90 and 0.88 demonstrated curve coeffi cients b1 and b0 respectively. A paired t-test demonstrated no significant difference between the left and right foot coefficients. Conclusion. The results demonstrated that each system component could be me asured accurately and reliable. Reproducible results were obtained over sep arate occasions. The study has described a method to analyse the force-disp lacement curve.