In recent years, numerous reports have focused on the surgical treatment of Bado I type missed Monteggia fracture in children[,,,,], and several articles have discussed the effect of surgery on such condition. However, no researches are found to explore the influence of the relationship between ulnar bow sign and ulnar osteotomy angle on the surgical operation. The current paper aims to study above relationship on the surgical treatment of Bado I type missed Monteggia fracture in children.
Our data indicate that Angle formation of ulna in proximal ulnar osteotomy is related to the P-MUB and R-MUB. When the position of the ulnar bow sign is close to the middle of the ulna, then a larger angle is needed to achieve a stable reduction in the radial head, as shown in Figs. 4.
At present, the period from injury onset to surgery and the age of the child are widely accepted factors that influence surgical outcome. In addition to the above factors, accepted relevant articles are rarely reported. Oka et al. [] noted that dislocation time reached more than three years, the ulnar and radial notch became shallow, and the shape of radial head changed from normal disc shape to flat to dome shape. Nakamura et al.[] thought that the changes in osteoarthritis in young children were lighter than that in missed children, and such parameter is related to the time of dislocation. Wilkins[] suggested that surgery should be performed within 12 years of age. In recent years, a growing number of researchers believe that surgery is better when the patient is younger than 10 years old, and when the dislocation is less than 12 months old [,]. In the current study, the dislocation time of our selected cases were all within one year to eliminate the interference of dislocation time and age on the study. At the time of operation, the children were not over 10 years old, and no serious radial head deformity in imaging was present.
In 1994, Linclon[] examined five children with radial head dislocation but without ulnar fracture and observed a straight line made between the olecranon and metaphysis of the distal end of the ulna on the lateral radiograph of the entire ulnar length. The maximum average distance from the dorsal edge of the ulna to the line was substantially greater than 1 mm (range: 3.9 ± 0.4 mm). Meanwhile, the values observed for the control group were all within 1 mm. Hence, the concept of ulnar arch sign was proposed. Given the rapid healing of children’s fracture, the fracture line disappeared after 3 weeks, which left only the ulnar plastic deformation in the same direction as the radial head dislocation. The most common characteristic sign is the arch sign of ulna to the palmar side, that is, the Lincoln sign. Hoon Park[] noted that when Lincoln’s largest arch distance is small and located at the distal end of the ulna, a stable reduction can be achieved without ulnar osteotomy. They obtained satisfactory results by simple open reduction in five cases of children whose ulnar bow was inconspicuous and located at the distal ulna. Ulnar osteotomy is often needed when the MUB is greater than 3 mm and located at the proximal region. In the present study, we observed that the missed Bado type I Monteggia fractures in children were all accompanied with an ulnar bow sign located in the area 20–60% from the distal ulna. For areas within 40% of the distal ulna, we divided the cases into the middle and distal groups. When the bow sign is located in the middle part of the ulna, the maximum bow distance of the ulna is larger than that in the distal part. We speculate that this condition is related to the mechanism of injury. When a child is injured, with greater impact and closer fracture site to the end of ulna, an evident bowed sign forms at that point or appears eventually. The specific mechanism needs to be proven by biomechanical studies. In cases with evident bow sign in the middle part of ulna, the angle formed during operation is larger than that in the cases with no remarkable bow sign located in the distal part of ulna. This finding is possibly related to the interosseous membrane injury. Reverse angulation of the ulnar osteotomy is performed mainly through the interosseous membrane traction to obtain a satisfactory location of the radial head. The angle of correction required during the operation depends on the tension of the antebrachial interosseous membrane[[14–19]]. The bow sign of ulna can well reflect the severity of injury. A prominent ulnar bow sign indicates considerable severity of the interosseous membrane injury. Hence, substantial reverse angulation of ulna is needed to turn the radial head.
All patients in the present study received ulnar osteotomy for the treatment of children’s missed Bado type I Monteggia fracture. Several researchers[[14, 20, 21]] believe that the location of ulnar osteotomy should be at the proximal end of the ulna. The advantage of osteotomy in this setup is that this process can induce sufficient tension in the interosseous membrane to align the radial head in the correct anatomical position. All interosseous membranes should also be preserved to avoid limited forearm rotation. This finding is consistent with the osteotomy site in the present study. In this study, the rotation function of children after operation was slightly lost compared with that before operation. Group B presented a better rotation function than group A. However, no statistical difference was noted (Tables 2 and 3). Hsuan Yu[] believed that the radial head deformity, which is gradually aggravated in the chronic course of the disease, is an important factor that limits forearm rotation. In the current study, the disease course of all the children was within one year. CT scan showed no notable radial head deformity. Thus, no significant loss of rotation function was noted in all the children after the operation. Complications of the ulnar opening wedge osteotomy included nonunion and fixation failure. Despite these complications, we believe that the stable reduction of the ulna ensures radial head reduction.Our research presents several limitations. This research is a retrospective study given the extremely low incidence of missed Monteggia fracture and our relatively small sample size (24 cases). Selection bias may be present, indicating the need for further verification by a larger sample size, multicentre study or prospective research. P-MUBAt present, limited reports have discussed these topics. The indication for osteotomy is difficult to establish, hence indicating the need for further research.