Transolecranon fracture-dislocation of the elbow is common in adults but rare in children. There is no report on the incidence of children at present, and most cases are caused by high energy injuries [9]. Most reports describe this injury occurring when a high-energy is applied directly to the proximal dorsal forearm with the obstruction of the trochlea to olecranon, which causes olecranon fracture associated with anterior dislocation of the proximal ulna and radius together [10]. However, it has been reported that when the elbow is in a hyperextended position, the proximal ulna acts against the olecranon fossa, which results in olecranon fracture. The further sustained effect of external force results in anterior dislocation of the distal complex of fracture [4]. Transolecranon fracture-dislocation of the elbow is a type of anterior dislocation in which compromise of the ulnohumeral articulation occurs through an complex injury to the proximal ulna, while the annular ligament and the proximal radioulnar joint remain intact [11].
In adults, fractures of the olecranon or proximal ulna are often serious. Type II fractures (comminuted type) are common, and most patients have coronoid process fractures. Therefore, stable anatomic reduction of the proximal ulna in adults with transolecranon fracture-dislocation is complex and difficult. Fixation of K-wires combined with reconstruction plate is often required, and bone grafts may sometimes be needed [12]. But in our cases, 11 patients suffered simple type of proximal ulna fracture. And 4 patients had comminuted type, 3 of them with coronoid process fracture. This difference may be related to children's periosteum hypertrophy, bone flexibility and relative relaxation of the elbow ligament, however, the situation is completely different in adults (shown in Fig 1). Therefore, we believe that most transolecranon fracture-dislocations in children are simple type and not as complicated and serious as those in adults. This conjecture has not been reported before.
In children, transolecranon fracture-dislocation is easily misdiagnosed as a type I Monteggia fracture and divergent anterior dislocation of the elbow with olecranon fracture. The characteristic Monteggia lesions are fracture-dislocations of the forearm, and the defining lesion is a dislocation of the proximal radioulnar joint. In addition, Monteggia’s classification of fracture-dislocations does not include ulnohumeral articulation. For treatment of these fractures, it is necessary to restore the normal alignment of the proximal ulna, which is fundamentally different from that of transolecranon fracture-dislocation. In this study, transolecranon fracture-dislocation of the elbow was a type of anterior dislocation of the elbow, while the proximal radioulnar joint remained intact. This is also different from Suzuki's report of a case of divergent anterior dislocation of the elbow with olecranon fracture [13]. This report described olecranon fracture of the ulna and anterior dislocation of the elbow joint with dislocation of the upper radioulnar joint and complete rupture of the annular ligament [13]. Therefore, the essential difference between transolecranon fracture-dislocation and type I Monteggia fracture and divergent anterior dislocation of the elbow with olecranon fracture is that the upper radioulnar joint is intact and stable. So, once the olecranon fracture has gained anatomic reduction, the brachioradial joint can be automatically reduced and matched, and the elbow can also be stabilized.
The dislocation of elbow in most children can been successfully reduced with closed reduction under local anaesthesia, based on the force of the injury mechanism. After reduction of dislocation, only a midline longitudinal dorsal incision was used for open reduction and internal fixation for olecranon fractures, which is conducive to early functional training of the elbow. If closed reduction failed, open exploration, reduction and internal fixation can be performed. The ulnar trochlear notch is 180° around the trochlea. Its integrity is important for the stability of elbow [14]. The interlocking of the olecranon and the coronoid process in their corresponding fossae on the distal aspect of the humerus provides additional stability at the extremes of ulno-humeral motion. Therefore, ulnar olecranon fractures should be anatomically reduced, especially in patients with coronoid process fractures, to restore the normal depth and width of the trochlear notch as much as possible [15]. If not, it will lead to instability or subluxation of the brachioradialis joint. The failure of treatment is due to improper treatment of the coronoid process fracture or incomplete restoration of the normal anatomical structure of the proximal ulna [16]. Olecranon fractures in children are usually less serious than those in adults, and these fractures in children are most often simple. Corradin used a cannulated screw to fix the olecranon fracture especially in older patients who did not have a comminuted fracture, with good effects and less complications [17]. However, considering the damage to the epiphysis and epiphyseal growth plate, we did not choose this fixation method. Therefore, reconstruction by smooth K-wires and tension bands is relatively easy and safe, without the combination of reconstruction plate. In addition, as proximal fracture fragment is small, the use of reconstruction plates may damage the epiphysis of the olecranon. However, K-wires combined with plate fixation is still needed in children with comminuted fracture. In our cases with simple type fractures, 10 patients received tension band with K-wire fixation(shown in Fig. 2), and one patient with a short oblique fracture underwent bone plate fixation. In 4 patients with comminuted fractures, internal fixation was K-wires combined with reconstruction plates (shown in Fig. 3).
The elbow was fixed with a plaster bracket for 3 weeks postoperation and function training was started after plaster removal. Patients were followed for an average of 30.2 months (range, 24–48 months). At the last follow-up, the therapeutic efficacy was evaluated at the final follow-up by the Mayo elbow performance score (MEPS) as excellent in 11 cases, as good in 3 cases and as fair in one case. At the last follow-up, a limitation of 10° of elbow extension has been recorded in this child, but with no impact on normal function.
There are many limitations to this study. First, this is a retrospective analysis, and the number of cases of each type is small, therefore we were not able to carry out statistical comparative analysis. In addition, the follow-up time of some patients was short, so whether there would be later development of complications is still difficult to predict.