Double trapezia sign: A new radiologic sign of scaphoid nonunion

In scaphoid nonunion, pseudarthrosis and sclerotic change occur at the nonunion site. These changes make a distal fragment look like a trapezium on plain radiographs and we called this phenomenon the double trapezia sign. The purpose of this study was to estimate the diagnostic reliability of the double trapezia sign and its clinical and prognostic implications for the scaphoid nonunion. A retrospective review of 124 patients who underwent surgical treatment because of scaphoid nonunion between January 2007 and December 2017 was performed. Two hand surgeons and 1 musculoskeletal radiologist reviewed preoperative plain radiographs independently. Each observer evaluated the plain radiographs in 2 separate sessions at least 3 weeks apart to assess intraobserver and interobserver reliabilities of the double trapezia sign. To assess clinical and prognostic implications of the double trapezia sign, the patients were divided into the positive and nonpositive groups, and several variables such as age, sex, duration of nonunion, size of the distal fragment, avascular necrosis (AVN) of the proximal fragment, type of bone graft, healing time, and failure rate were compared between the 2 groups. The kappa values of intraobserver and interobserver reliabilities were >0.8, corresponding to almost perfect agreement. There were 58 patients in the positive group and 66 patients in the nonpositive group. The mean duration of nonunion was 38.5 months in the positive group and 12.2 months in the nonpositive group (P < .001). The size of distal fragment was 49.6% and 60.9%, respectively (P < .001). The AVN of proximal fragment was 24.1% and 54.5%, respectively (P = .001). The mean healing time was 4.1 and 6.4 months, respectively (P < .001). The failure rate was 13.8% and 27.3%, respectively (P = .066). In conclusion, the double trapezia sign is a valuable radiographic sign of scaphoid nonunion. The double trapezia sign is easily identifiable on plain radiographs and has excellent intra- and interobserver reliabilities. The positive double trapezia sign implies mid-waist nonunion, long duration of nonunion, less possibility of AVN, and favorable postoperative prognosis.