Diagnostic Accuracy of Harris Imprint Index, Chippaux-Smirak Index, Staheli Index Compared With Talar-First Metatarsal Angle for Screening Arch of Foot.

Objective: To determine the diagnostic accuracy and reliability of the Harris imprint index (HII), Chippaux-Smirak index (CSI), and Staheli index (SI) compared with the talar-first metatarsal angle.

Methods: Data was collected at the orthotic and prosthetic clinic, Thammasat University Hospital from January 1, 2016 to August 31, 2020. The three footprints were measured by the rehabilitation physician and the orthotist. The talar-first metatarsal angle was measured by the foot and ankle orthopaedist.

Results: The data from 198 patients with 274 feet was analyzed. The diagnostic accuracy of the footprint triad showed that CSI was the most accurate in pes planus prediction, followed by HII and SI (area under the receiver operating characteristic curve [AUROC]=0.73, 0.68, 0.68, respectively). In pes cavus, HII was the most accurate, followed by SI and CSI (AUROC=0.71, 0.61, 0.60, respectively). For pes planus, the intra-observer reliability by Cohen's Kappa was 0.92 for HII, 0.97 for CSI, and 0.93 for SI, the inter-observer reliability 0.82, 0.85, and 0.70, respectively. For pes cavus, the intra-observer reliability was 0.89 for HII, 0.95 for CSI, and 0.79 for SI, inter-observer reliability of 0.76, 0.77, and 0.66, respectively.

Conclusion: The accuracy of HII, CSI, and SI was fair in screening of pes planus and pes cavus. The intra- and inter-observer reliability were in the moderate to almost perfect range by Cohen's Kappa.