Recent trends in children's elbow dislocation with or without a concomitant fracture

The elbow is a complex joint, composed of three bones which all articulate, allowing it to move in three planes. Ulno-humeral joint dislocation can occur in posterior, anterior, medial or lateral directions [1, 2]. The posterior direction is the most common [3]. The trauma mechanism leading to elbow dislocation is usually similar to that of elbow fractures: a fall on an outstretched hand [4]. Dislocation is often accompanied by bone fracture, while avulsion of the medial epicondyle is the most common concomitant injury [1]. Other bone fractures associated with the dislocation are at lateral humeral condyle, radial head, olecranon and coronoid process of the ulna [5]. Prompt reduction and external splint immobilization of a simple elbow dislocation are associated with good results [2, 5‐8]. A displaced fracture, however, may indicate surgical fixation to hold the joint congruent [3, 5, 9].

Of all joints, the elbow is the most common in children to become dislocated [5]. The annual rate of elbow dislocation is 3–6% of all elbow injuries in children [10]. Nevertheless, epidemiological studies concerning childhood elbow dislocation are extremely sparse: to our knowledge the only research on the annual incidence in an unselected population is by Josefsson and Nilsson, who reported 178 dislocations in adults and children in 1971–1982 in Malmö, Sweden [11]. The childhood fracture pattern has changed during the last 40 years. There is no understanding of the recent incidence and potential change in incidence of elbow dislocation in children. In contrast, many other paediatric injuries in the upper extremities have been found to have increased in recent years [12, 13]. For example, forearm shaft fractures have increased fourfold in the last decade and supracondylar humeral fractures by 30% at the same time [12, 14, 15].

This study was performed to analyse the incidence and potential changing trends in elbow dislocation in children. Associative fractures, particularly in the medial epicondyle, were to be analysed. We hypothesized that elbow dislocation in children has increased in recent years, similarly to many upper-extremity fractures.

The mean incidence of elbow dislocation was 6.4 per 100,000 children during the long study period (1996–2014). There was no change in the incidence. The findings are important because the previous understanding of the epidemiology of childhood elbow dislocation is markedly limited and based on the epidemiological findings four decades ago. However, our findings are surprising, keeping in mind that upper-extremity fractures rather than lower-extremity fractures have increased in children recently. For example, forearm fractures (distal, middle and proximal) increased by 31% and upper-arm fractures by 39% over 22-year period (1983–2005) in Helsinki, Finland [13]. The injury mechanism of elbow dislocation is mostly the same as that of forearm or elbow fractures: a fall on the arm. Therefore, it remains unclear why fractures in the elbow region have increased steadily but the same trend is not seen with elbow dislocations. There may be not only environmental reasons, for example changed recreational activities, but also biological reasons behind this finding: biological changes may have affected bone structure rather than ligaments and may have resulted in an increasing incidence of fractures in children. Childhood bone fractures tend to be multifactorial in nature and both external and internal factors may exist. Bone characteristics like bone mineral content and bone size are lower in children and adolescents who suffer from fractures. It has been found out that low bone mineral density predicts new fractures [17, 18]. Maternal smoking is associated with increased risk of childhood fractures [19]. Similarly, we suppose that there are both external and internal causes resulting in joint dislocations, too, in children patients.

An associated fracture was found in 44% of the patients, which is less than previously reported: Carlioz and Abols reported associative fractures in 64% [20] and Rasool in 75% [1] of patients. Di Gennaro et al. reported a bone fracture in connection with dislocation in 67.5% of cases [7]. However, we utilized a population-based study setting and radiographs were available for all; our results are certain. A medial epicondyle fracture was the most usual associative fracture, which is in accordance with reports in the literature [1, 7]. We therefore analysed medial epicondyle fractures (N = 30) separately, revealing satisfactory outcomes in 82% of surgically treated patients. In turn, 63% of non-operatively treated patients had satisfactory short-term outcomes. The difference did not reach statistical significance and the groups were small. However, this trend is in line with reports in current literature [21]. Operative fixation has been found to be superior to non-operative treatment in cases of medial epicondyle fracture among patients with elbow dislocation according to a recent study of 498 patients [22]. Regardless of fracture union rate, clinical or functional disabilities seem to be minimal after non-operative treatment of medial epicondyle fracture with or without associated elbow dislocation [8]. In general, the aim of operative treatment in cases of elbow dislocation with an associated fracture is to maximize an early return to daily mobilization and high-level activity [22].

There are some limitations in this study. Only short-term outcomes of medial epicondyle fracture could be determined, although, long-term outcomes would be important as regards childhood trauma, justifying further research with longer follow-up periods [23, 24]. Despite the population-based study setting, there may have been a few isolated cases that were treated elsewhere, for example during a holiday trip, and were therefore not enrolled. As another weakness, the fractures were diagnosed by radiographs, possibly resulting in the fact that not all osteochondral fractures were found. Magnetic resonance imaging was not performed in the cohort [25] due to practical reasons [8]. As a strength, this is the only study concerning the incidence and recent trend in childhood elbow dislocation in a normal child population since the 1980s, to best of our knowledge. The patients were children and adolescents of < 16 years of age in a particular geographical study area comprising both rural and urban regions. An appropriate population-at-risk size was determined by using official statistics and the incidence numbers are precise. The follow-up time was not long but sufficient to demonstrate the immediate results and complications, in particular the need of reoperation. The original radiographs of all patients were re-reviewed for the purpose of the study.

The mean incidence of elbow dislocation was 6.0 per 100,000 in children and showed no changes in trend in 1996–2014, in contrast to paediatric fractures in that area. Trampoline jumping was the most usual reason for elbow dislocation, which was not benign injury in nature in all cases.