The incidence and treatment trends of pediatric proximal humerus fractures

Proximal humerus fractures in children comprise approximately 2% of all pediatric fractures [1]. They are usually caused by sport injuries, motor vehicle accidents, or birth trauma, while the usual mechanism of injury is hyperextension combined with external rotation of the shoulder. The fractures are either metaphyseal, which occur mostly in children 5–12 years of age [2, 3], or epiphyseal separations [4, 5]. Diagnosis is based on plain radiographs [6‐11] and fractures are classified according to their severity and anatomic location [12]. Fractures involving the growth plate are classified with the Salter-Harris (SH) fracture classification [2, 13‐16]. Displacement and angular deformity can be summarized using the Neer classification [3].

The proximal growth plate of the humerus is responsible for 80% of the bone’s longitudinal growth. Further, the periosteum is metabolically active in the immature skeleton [3, 12]; therefore, bone healing and spontaneous remodeling of proximal humerus fractures in children are usually good [17] and non-operative treatment preferred. However, the more displaced the fractures and the older the children are, the poorer the results will be [2, 17‐19]. Persistent deformity, such as shortening, may decrease the outcome [20]. Surgical fixation has traditionally been recommended in proximal humerus fractures when closed reduction is unsatisfactory due to interposed long head of biceps tendon, deltoid muscle or capsule [21, 22], and in cases of nerve or artery injuries. Percutaneous Kirschner wire pinning is the most usual fixation in children, often combined with closed reduction. Plate and screw fixation are rarely justified; however, many surgeons recommend the elastic stable intramedullary nailing (ESIN) technique because it is stable enough and safe regarding the surrounding soft tissues [4, 23, 24]. This technique is reported to have no increased association to skin irritation or infections and the bone healing is effective and the functional outcome appears to be good [25].

Pediatric upper extremity fractures in general have increased since the beginning of the 2000s [26], but closer epidemiological description and the recent treatment trends of the proximal humerus fractures are mostly unknown. The purpose of this research was to study the local incidence and treatment trends of proximal humerus fractures in children.

Contrary to the recent increasing trends in general pediatric upper extremity fractures [26, 28, 29], the incidence of proximal upper arm fractures has not increased during the last decade. Such different incidence trends between proximal humerus fractures and other upper extremity fractures (e.g. forearm and supracondylar humerus) is an interesting finding. The reason for the different trend of proximal humerus fractures remains unclear but can be explained by the specific injury mechanisms. Forearm and supracondylar humerus fractures were often caused by trampoline jumping [27], while proximal humerus fractures resulted from horse riding and high-energy winter sports, such as snowboarding. Greater trauma-energy may result more frequently in proximal humerus fractures than distal humerus or forearm fractures, which are usually caused by falling against the fully extended arm. From an epidemiological point of view, the number of backyard trampolines in the study area has increased since the beginning of 2000s [30, 31]; therefore, it is reasonable that trampoline related distal humerus injuries have increased [32]. However, any increase in horse riding or winter sports within the child population has not been reported in the area, to our knowledge. The annual incidence of proximal humerus fractures had no changing trend during the study period, and it was on average 31 fractures per 100,000 children every year. Proximal humerus fractures comprised approximately 2% of all fractures, compared to the total incidence of pediatric fractures (1630/100,000) in the country during the 2000s [33]. The total incidence of the proximal humerus fractures in this study was smaller than previously reported (68/100,000) by Larsen et al. in 1990 [19].

Regardless of the stable fracture incidence, surgical treatment of proximal humerus fractures had increased as an alternative to nonoperative treatment. This trend agrees the literature concerning childhood fractures in general: the operative treatment of childhood fractures has increased more than the fractures in a nationwide research of the study country [34]. Similar trend has been reported in Sweden between 1998 and 2007 [35]. However, there is no wide understanding about the recent trend of surgical treatment of proximal humerus fractures; only one recent study by Cruz et al. [36] reported an increase in the surgical treatment of proximal humerus fractures, the findings of which are strengthened by the present study. Analyzing 7520 proximal humerus fractures in the United States from 2000 to 2012, Cruz et al. found that surgical treatment increased from 39.3 to 46.4%. Nevertheless, there is sparse evidence supporting this recent change towards surgical fixation of proximal humerus fractures, and no clinical trials comparing the operative and nonoperative treatment in the modern era of fracture care are available [37].

It is generally accepted that boys suffer from bone fractures more often than girls [38]. More than 60% of all fractures affect boys [39]. Against this common trend, this study found that girls showed greater incidence of proximal humerus fractures than boys. Similar findings have been made in 2011 by Schalamon et al. [40]. Binder et al. [41] found that 50% of the patients with proximal humerus fractures were boys and girls (116). Such a gender distribution with girls being predominant, as also seen in the present study, seems extremely rare in children [42]. This is opposite to the gender distribution of corresponding fractures reported in the United States [36]. However, horse riding was found as the most common cause of injury, comprising up to 17% of all accidents in this population; since this activity is commonly considered more popular among girls, this may be one explanatory factor for the female predominance of this study. The mean age of patients suffering from proximal humerus fractures was 14 and 10 years old for boys and girls, respectively, which fits well with the general age distribution of childhood fractures [39].

For some reason, the redisplacement rate and need of later operation after primary nonoperative treatment was higher in this study than in the published literature. In 2017, Gladstein et al. [43] reported that only one patient out of 225 was re-operated on after failed nonoperative treatment. In the present study, 10 out of 286 primarily nonoperatively treated patients were surgically treated later due to a redisplacement. The difference in failed nonoperative treatment may be explained by the different clinical practice between the institutions; some surgeons may prefer nonoperative treatment primarily, and only go on to operative treatment after failed nonoperative treatment.

Primary displacement was found to be associated with operative fixation, while a bayonet position increased the risk of surgical fixation by 16-fold. Instead, even great angular deformity was not associated with increased surgical treatment. These findings are still reasonable, keeping in mind that just translational displacement (bayonet position) usually decreases the abduction motion of the shoulder, thus justifying surgical fixation [44]. In turn, angular deformity usually does not affect the functional performance of the arm, while the motion arches in shoulder joint are wide in general.

The weakness of the study was that the injury mechanism and associated background factors were not always well explained in the hospital charts. Injury history and clinical findings were based on the hospital registries. As a limitation, the number of patients who were operatively treated was not high, despite the long study period and satisfactory population at risk. A great majority of proximal humerus fractures are traditionally treated by nonoperative means. Further, there was no long-term follow-up data available, and the facture patients’ final recovery could not be determined.

The strength of this study was its inclusive population-based design: all patients in the geographic catchment area during the study period were included. There were no other pediatric trauma centers in the area and slight proximal humerus fractures were followed-up in the study center too, despite the potential first contact in primary health care. Treatment was the same for every patient despite their economic situation and possible insurance status. It is still possible that there were a few non-inhabitant patients who were treated outside the study center; however, their number must be infinitesimal.

The incidence of proximal humerus fractures in children has been stable, but the rate of operative treatment, rather than nonoperative treatment, has increased during the last decade. A bayonet position associates with surgical treatment; however, the reason for increasing surgical fixation remains unclear.