The effect of trauma and patient related factors on radial head fractures and associated injuries in 440 patients

The radial head is an important secondary stabilizer of the elbow [7]. Especially in combination with deficiency of the collateral ligaments or coronoid fractures, elbow stability heavily relies on an intact radial head [8]. Accurate recognition and assessment of all associated injuries are necessary to initiate the correct treatment of the injury; early adequate management is mandatory to improve the clinical outcome [8, 9]. The radial head fracture is, in general, believed to be an isolated, simple injury with a benign outcome. However, associated injuries with radial head fractures are increasingly recognized for their clinical significance [10‐12]. The current study revealed an 11 % risk of symptomatic associated injuries, which increases with age and Mason fracture type.

It is thought that the complexity of the injury is related to the amount of energy transferred during the trauma. However, in this study energy transfer during trauma was not related to associated injuries or Mason fracture type. Radial head fractures following HET occurred most frequently in young men. HET did not lead to more associated injuries or more complex radial head fractures than LET in the current study. The only predictors for more associated injuries were a higher Mason fracture type and a higher age. High-energy transfers through the elbow joint during trauma did not result in more concomitant injuries in young patients, in contrast to older patients that sustain LET more commonly. Based on these observations, we assume that additional injuries, next to radial head fractures, were also dependent on the intrinsic quality of bone and soft tissues and a frailty phenotype of the elderly patient. Therefore, complex elbow trauma in patients with a radial head fracture should be suspected based on patient characteristics rather than the mechanism of injury.

Mechanism of injury of radial head and neck fractures have been categorized by Duckworth et al. in low-energy (i.e. fall from standing height) and high-energy (e.g. sports trauma or fall from height), as is done in the current study [2]. They observed significant more HETs in males, and HET was defined as a significant risk factor for associated injuries. HETs occurred in 43 % of the 285 patients in their series and associated injuries were present in 7 % of patients. The current study identified 40 % of injuries as HET, and 11 % of patients had associated injuries. However, HETs were no significant risk factors for additional injuries in this series. One explanation for this difference might be that Duckworth analyzed both radial head and neck fractures, whereas we included only radial head fractures. They suggested that radial neck fractures were – more than radial head fractures – low-energy fragility fractures. Another explanation might be that associated injuries occur by the direction of impact during trauma rather than by the amount of energy transferred during trauma. McGinley et al. found that axial impact in neutral position of the forearm resulted in isolated radial head fractures, whereas loading in pronation resulted in more comminuted fractures with associated lesions of the interosseous membrane [13]. Thus, how the energy is transferred may be more important than how much energy is transferred during trauma.

In this study, associated injuries were more frequently observed in the elderly, and female patients with a radial head fracture were older than males. These findings are in agreement with suggestions that radial head fractures are potentially osteoporotic fractures [4]. Gebauer et al. recently performed cadaveric studies on the microarchitecture of the radial head. BMD and histomorphometric analysis were performed on radial heads of three different groups of cadavers; aged 20–40 years, 41–60 years, and 61–80 years. They showed a significant decrease in BMD with increasing age for men and women. Trabecular thickness significantly decreased with age, whereas trabecular separation significantly increased with age, leading to more radiolucency of the radial head on radiographs with aging. These age-related changes in microarchitecture of the radial head were suggested to reduce the biomechanical stability of the bone [14]. Since associated injuries were more commonly observed in older patients in the current study, we assume that older female patients with a radial head fracture overall have a diminished bone quality. As the extent of the injury varies with the position of the forearm during a fall, the way elderly fell may also account for the higher amount of associated injuries. Overall, a frailty phenotype is associated with a greater risk of fracture, disability and falls in elderly women [15]. It seems therefore critical to maintain optimal bone and soft tissues qualities, as well as overall physical condition, in the aging population in order to prevent more complex elbow injuries.

The more complex the radial head fracture is according to the Mason classification, the higher the frequency of associated injuries in the current study. Associated injuries were identified in almost half of the patients with a Mason type-3 fracture of the radial head. Kaas et al. noticed associated injuries on MRI in even 100 % of patients with a Mason type-3 fracture [16]. Therefore, thorough evaluation of the elbow by a preoperative CT- or MRI-scan and/or intraoperative stability testing using fluoroscopy might be preferable to adequately deal with possible associated injuries in all Mason type-3 fractures. With regard to Mason type-2 fractures, Rineer et al. identified concomitant injuries in 77 % of patients [17]. They divided Mason type-2 fractures in two groups based on the existence of cortical contact between the fracture fragment and the radial head. Fracture fragments without cortical contact led to a 21-times greater risk for associated injuries. Loss of cortical contact was in the current study seen in 37 % (17/46) of patients with associated injuries, versus 6 % (24/381) of patients without associated injuries. However, the distribution of radial head fractures among the Mason fracture types in the study from Rineer [17] is variant to those of Kaas [1], Duckworth [2], and the current study, as is the amount of associated injuries for Mason type-2 fractures. Nevertheless, as Rineer et al. concluded: ‘if imaging studies fail to demonstrate the presence of a complex elbow injury pattern, the surgeon should still have a high suspicion that some degree of occult instability may be present’ in Mason type-3 fractures and Mason type-2 without cortical contact [17].

The current study was with 440 included patients one of the largest studies on the epidemiology of radial head fractures [2, 1, 18, 19]. The influences of mechanism of injury on radial head and neck fractures and associated injuries have only been once reported before [2]. The current study focused both on modes of injury and patient related factors on associated injuries for radial head fractures, leading to other findings. This study had several limitations in addition to its retrospective nature. First, associated injuries were documented based on available imaging studies instead of standardized radiographic studies for all patients. For instance, a standard MRI was not performed, and the LCL lesions in this study were identified as avulsion fractures from the epicondyle or during surgical reconstruction of Mason type 3 fractures. However, since most associated injuries are not clinically relevant, it is not advised to perform MRI scans on a regular basis for radial head fractures [10]. Second, the interobserver reliability of the Mason classification is known to be only moderate [20]. In addition, it might be difficult to take standardized radiographs of the elbow in the acute setting because of pain. Third, there is no clear definition of amounts of energy that are transferred during different mechanisms of injury. Moreover, the direction of impact (axial, direct, rotation of forearm, etc.) during trauma, may be more important to sustain associated injuries than the kind of trauma [21].

Future research should concentrate on Mason type-2 and type-3 fractures and the association with clinically and therapeutically relevant associated injuries. The impact of energy transfer during trauma and its consequences on associated injuries should be established. The indications for additional imaging studies for these fractures need to be explored.