Influence of Ulnar Bow Sign on Surgical Treatment of Missed Bado Type I Monteggia Fracture in Children

Abstract PurposeThe present study aimed to explore the influence of ulnar bow on the surgical treatment of Bado type I missed Monteggia fracture in children.MethodsThis study is a retrospective review of 24 patients between November 2010 and March 2019. All patients were treated with open reduction of the radial head and ulnar opening wedge osteotomy without annular ligament reconstruction. The mean interval between injury onset and surgery was five months (range: 2–12 months). The average age of participants at the time of surgery was 6.4 years (range: 3–10 years). We evaluated the maximum ulnar bow (MUB) and MUB position (P-MUB) via radiography. The patients were divided into middle group (group A: 14 cases, MUB located at 40% to 60% of the distal ulna) and distal group (group B: 10 cases, MUB located at 20% to 40% from the distal end of the ulna) based on P-MUB. The mean period of follow-up was 37 months (range: 6–102 months).ResultsAt the last follow-up, all the children showed stable reduction of the radial head, and the flexion function of elbow joint improved after operation (P<0.05). Group A presented a larger the ratio of maximum ulnar bow(R-MUB) and angle of ulnar osteotomy(OA) than group B (P<0.05). There was statistically significant difference between group A and Group B in the P-MUB (P < 0.05). The osteotomy angle was positively correlated with the R-MUB (R2 =0.497,P=0.013), The osteotomy angle was positively correlated with the P-MUB (R2=0.731,P=0.000), The R-MUB is proportional to the P-MUB (R2 =0.597,P=0.002). The regression equation of P-MUB and osteotomy angle: Angle=7.064+33.227* P-MUB (R2=0.459, P =0.000).ConclusionWhen the ulnar bow is positioned at the middle ulna, a stable reduction of radial head need to be achieved through a larger angle in the ulnar osteotomy. If the position of maximum ulnar bow (P-MUB) is closer to the middle of the ulna or the ratio of maximum ulnar bow (R-MUB) is larger, the osteotomy angle is larger.