Comparison of radiological measures for diagnosing flatfoot.

BACKGROUND: In the Taiwanese military, flatfoot is indicated by a calcaneal-fifth metatarsal angle (arch angle) ≥165°. However, the arch angle is not always easily defined. PURPOSE: To assess correlations between the arch angle and other radiographic measures and thus identify an alternative radiographic measure for diagnosing flatfoot. MATERIAL AND METHODS: Eighty-seven male Taiwanese military recruits were studied (median age 22 years, interquartile range 20-23 years). Lateral, weight-bearing radiographs were taken. Five radiographic measurements, including the calcaneal-fifth metatarsal angle (arch angle), medial arch angle (MAA), calcaneal pitch angle (CP), talus angle (TA), and talar-first metatarsal angle (TFM) were made. Correlations between the arch angle and all other measures were determined. A cut-off value for predicting flatfoot (arch angle ≥165°) was determined for each measure using the Youden index and receiver-operating characteristic (ROC) curves were generated for each measure to assess diagnostic accuracy. RESULTS: All measures were significantly correlated with arch angle (P < 0.05); however, the strongest correlation was for CP (ρ = -0.905, P < 0.001). CP was associated with the highest area under the ROC (0.988 vs. 0.711-0.912 for the other measures). Further, CP (cut-off <12.3°) had the highest sensitivity (92.0%), positive predictive value (76.7%), and negative predictive value (96.5%). TFM (>9.5°) had the highest specificity (90.3% vs. 88.75 for CP <12.3°). CONCLUSION: CP is inversely correlated with arch angle in Taiwanese male military recruits. CP < 12.3° is a significant predictor of flatfoot. Assessment of CP may be used as an alternative means of diagnosing flatfoot when the arch angle is not easily defined.

Synthesis, crystal structure, and solid-state NMR spectroscopy of a salt-inclusion stannosilicate: [Na3F][SnSi3O9].

A salt-inclusion stannosilicate, [Na3F][SnSi3O9], has been synthesized using a flux-growth method and characterized by single-crystal X-ray diffraction. The structure consists of six-membered silicate rings linked via corner sharing by SnIVO6 octahedra to form a 3-D framework that delimits two types of channels. The F atoms and Na atoms are located in the structural channels and form a dimer with the anti-Al2Cl6(g) structure. This stannosilicate adopts a new structure and is the first metal silicate that contains both Na+ and F- ions in the channels. The 19F and 29Si MAS NMR and 23Na MQMAS NMR spectra are consistent with the crystallographic results.