Radiographic measurement of the first metatarsal: a new technique to improve the accuracy of intermetatarsal angle measurement

BACKGROUND: The first intermetatarsal angle is a radiographic measurement frequently used in hallux valgus surgery. A plethora of techniques to obtain the angle exist, but no standardized technique is used to obtain the bisection of the first metatarsal. A novel technique, the Taylor-Metcalfe technique, has been developed and compared with two existing methods to identify the repeatability and reproducibility of the first metatarsal bisection. METHODS: To evaluate the measurement accuracy of the novel technique, we calculated the intraobserver and interobserver coefficients for the three techniques with 30 preoperative and 30 postoperative radiographs. RESULTS: The intraobserver coefficient of repeatability for the preoperative and postoperative measurements ranged from 2.1 to 4.4, with the novel technique obtaining the lowest values. The novel technique also obtained the lowest values for interobserver reproducibility, with values obtained ranging from 0.77 to 1.61. An existing technique had the lowest value for interobserver reproducibility for preoperative measurements, with the novel technique obtaining the lowest values for the remaining measurements. CONCLUSIONS: Compared with two existing techniques, a novel technique for accurately obtaining the bisection of the first metatarsal was consistently found to be reproducible and repeatable