Digital Measurements With Hallux Valgus Before and After Modified Long Oblique Osteotomy

Radiographic measurements of the hallux valgus (HV) angle (HVA) and the first intermetatarsal angle (IMA_1-2) are important for assessing the severity of HV. The purpose of the present study was to digitally investigate the intraobserver and interobserver reliability of various methods for measuring HVA and IMA_1-2, as well as each axis composing them, such as axes of the first proximal phalanx (PP1), the first metatarsal (MT1), and the second metatarsal (MT2) in patients with a metatarsal shaft osteotomy-modified long oblique osteotomy. Three orthopedic surgeons measured the HVA, IMA_1-2, and the angles between axes of PP1, MT1, and MT2, and the digitally-set reference line (α, β, and γ, respectively) using 6 different methods for 39 patients with a minimum of 1 year of follow-up after operative treatment. The intraobserver and interobserver intraclass correlation coefficients (ICC) and agreements were calculated. Significant differences were observed within the methods with regard to preoperative HVA, IMA_1-2, α, and β, and postoperative IMA_1-2 and β. Intraobserver and interobserver ICC were high or very high in most methods. For HVA and IMA_1-2, the method connecting the center of the head through the center of the base showed the highest agreement. For α, β, and γ, this method showed the highest agreement, more than 80% intraobserver and interobserver agreement and a discrepancy of <2°. A digital method connecting the center of the head through the center of the base was regarded as the least variable for the HV evaluation and the assessment of the radiographic results in a metatarsal shaft osteotomy-modified long oblique osteotomy.