Distal part of ulna and radius is the junction of dense bone and cancellous bone. Cortical bone becomes thinner in this area. There is a lack of compact and regular bone plates and units. Epiphysis exists at the distal part of radius and ulna in children, where the growth rate exceeds the calcification of bone, resulting in relatively low bone mineral density. Therefore, distal part of ulna and radius is an anatomic weak area, which is prone to fracture. Distal radius-ulna fractures are common in children, and most of them are closed injuries [1, 2]. The most common fracture types are palmar dorsum overlapping displacement. It is rare of long oblique type, spiral type and comminuted type.
Children under 8 years old after fracture have a strong shaping ability [10]. Most of the children in this age group can be treated conservatively [11, 12]. The molding time can be as long as several months. Older children may have incomplete shaping and even residual local deformities [13, 14]. The conservative treatment is usually closed reduction and plaster external fixation. Before reduction, operators should be clear with the strength, direction of external force and the traction effect of osteofascial and muscle on the fracture fragment. After understanding the mechanism of injury, fracture displacement is reduced by reversing injury mechanism. Most of the children can achieve satisfactory reduction by simple traction and manual reduction [3,4,5]. However, during the period of plaster fixation, due to the regression of forearm swelling and plaster loosening, about one third of children with fracture redisplacement were reported in literatures [15,16,17]. If redisplacement of the fracture is not serious, it can be untreated. However, if redisplacement of the fracture is significant, it needs to be reduced again. Due to serrated fracture site in some children, length of the distal part is small and direct traction is weak, which makes it difficult to remove the insertion. At this time, satisfactory reduction can not be achieved by only closed reduction. Forced closed reduction can aggravate soft tissue injuries, lead to neurovascular stretch injuries, and even lead to osteofascial compartment syndrome, epiphyseal injuries and other serious complications [18]. Most fractures of distal radius-ulna are straight fractures in children. The distal fragment displaces to the dorsal side. Most of the dorsal periosteum is intact, the broken sites are not easy to pull apart, and the fracture sites are still overlapped. Sometimes soft tissues or periosteum are inserted at the fracture site, which will prevent fracture reduction. In addition, some children struggle and do not cooperate in the process of reduction, which brings difficulties to manual reduction. All of these reasons will lead to the failure of closed reduction. When manual closed reduction fails, scholars still have disputes about which technique to use for reduction.
Operators may solve the problem of irreducible distal radius-ulna fractures by open reduction technique. According to displacement of the fracture, incision can be made on the palmar or dorsal side. However, open reduction is traumatic, bleeding, leaving surgical scars, and even a certain probability of damaging epiphysis, resulting in growth arrest and other serious complications. Some scholars used minimally invasive prying reduction technique of Kirschner wires in the treatment of irreducible distal radius fractures in children [19, 20]. Pavone et al. reported the midterm results of surgical treatment of displaced proximal humeral fractures in children [21]. They showed excellent results with a minimally invasive treatment with percutaneous k-wires. The excellent outcomes they observed led them to prefer the mini-invasive surgical approach in NH grade III fractures [21]. As a reduction tool, Kirschner wire is usually inserted at the fracture site, which works through the lever principle. However, a fine Kirschner wire is easy to bend, and the force may be insufficient when prying through the lever principle. When a thick Kirschner wire is used for prying, its sharp tip may aggravate injury of soft tissues, and even cause nerve and blood vessel injuries. When soft tissues are inserted at the fracture site, it is necessary to release soft tissues, and at this time, Kirschner wire can not play a good role. So, is there a more suitable tool to achieve the purpose of prying reduction?
The authors used mosquito forceps in older children with distal radius-ulna fractures, and achieved satisfactory reduction effects. Mosquito forceps are small and fine, with blunt tips, and are always available in the operating room. This design allows it to be inserted through a minimally invasive incision. Mosquito forceps can provide enough strength during prying reduction without increasing the risk of nerve and vascular injuries. Therefore, mosquito forceps can be a good tool for prying reduction. The authors’ retrospective study shows that, compared with limited open reduction, it has shorter incision length, less bleeding and shorter operation time of prying reduction with mosquito forceps. Due to the minimally invasive incision, only 0.5 cm, children feel mild pain postoperatively. A smaller incision means less damage to soft tissues and blood supplies, so that there is less bleeding during the operation process, and the incision is easier to heal. It can significantly shorten the hospitalization time of children after operation, which is also in line with the concept of accelerating rehabilitation. However, the fluoroscopy times were slightly increased during prying reduction. Clinicians should pay attention to radiation protection. Although both groups achieved good wrist functions, incidence of common postoperative complications was lower in PRMF group. Importantly, there are some pitfalls of PRMF technique that surgeon should avoid. Firstly, pay attention to gentle prying, do not break the fracture fragments. Secondly, in the process of prying, the two teeth of mosquito forceps should be closed to avoid clamping nerves and blood vessels. Thirdly, when the assistant assists through longitudinal traction, pay attention to avoid soft tissue traction injury. Fourthly, do not use the tip of mosquito forceps to probe the distal part of the fracture fragment excessively, so as to avoid damaging the epiphysis.
There are still some limitations in this study. The number of children included in this study was small, and the follow-up time was short. This study was limited to the metaphysis of the distal radius and ulna, and did not include children with epiphyseal fractures. Sometimes, metaphyseal fracture and epiphyseal fracture can occur in one child at the same time. In addition, this study was a single center clinical study. In the future, the authors will further carry out multi-center clinical research. The above deficiencies will be corrected in further research.