Shoulder injuries in polytraumatized patients: an analysis of the TraumaRegister DGU®

Severe trauma is the sixth leading cause of death worldwide, and among young adults under 35 years of age, it is the leading cause of death and disability [1]. This changes the awareness from the patient’s survival to recovery, outcome, and quality of life after trauma. In polytraumatized patients, extremity injuries are highly prevalent, occurring in 58.6% of cases [2]. The outcome of polytraumatized patients is worse after additional extremity injuries since they may suffer from severe functional posttraumatic deficits [3‐6]. Therefore, the therapy of extremity injuries in multiple injured patients plays a major role in the long-term outcome.

In major trauma, injuries to the shoulder, including severe nerve and vessel injuries, are frequently seen [7] and may represent some of the most common musculoskeletal disorders appearing in the emergency room [8, 9]. In motorbike accidents and polytraumatized patients, upper extremity injuries are frequently seen [2, 10].

In the present literature, several studies highlight the relevance of scapular fractures in a severe trauma or shoulder injuries in general [11‐15]. Nevertheless, there are no studies of the TraumaRegister DGU® or similar international databases available that provide a complete overview of injuries of the shoulder in severe multiple trauma and their association with outcome, trauma mechanisms, or concomitant injuries.

The purpose of this study was to investigate the prevalence and clinical features of shoulder injuries in polytraumatized patients. Furthermore, the impact on mortality was assessed, and concomitant injuries were identified.

We presumed that, in the treatment of severely injured patients, the early identification of patients with a high risk for shoulder injuries might help reduce delayed diagnoses and decrease complications. We hypothesized a high prevalence of shoulder injuries in traffic accidents and a high prevalence of concomitant injuries of the thorax leading to an aggravated clinical course and higher ISS.

In severe trauma, approximately every third patient suffered a shoulder injury (n = 15,115, 27.9%). Patients in the shoulder group had a significantly increased ISS (29.2 ± 11.6 vs. 28.2 ± 11.9, p < 0.0001) and were older (47.4 ± 20.2 years vs. 46.4 ± 21.4 years, p < 0.0001). As men comprised the majority of all patients in severe trauma, at 72.5% of all cases, gender could not be identified as a risk factor (Table 1).

Shoulder injuries were highly associated with blunt trauma in 97.6% of the cases. Moreover, shoulder injuries were caused significantly more often by traffic accidents than by other causes (68.5% vs. 31.5%, p < 0.0001), especially in contrast to the non-shoulder group (60.5% vs. 39.5%, p < 0.0001). Focusing on traffic accidents, shoulder injuries were caused significantly more often by motorbike (20.6% vs. 13.4%), bicycle (10.5% vs. 6.8%), or pedestrian accidents (9.6% vs. 8.1%) (all p < 0.0001). Accidents with cars and trucks (26.7% vs. 31.2%), falls < 3 m (9.1% vs. 11.9%) and falls > 3 m (18.8% vs. 20.5%) were less frequently associated with shoulder injuries (all p < 0.0001) (Fig. 1).

Concerning the injury pattern of polytraumatized patients and associated concomitant injuries, shoulder injuries were significantly associated with thoracic (82.9% vs. 69.6%), head (56.1% vs. 52.2%), and spine (40.5% vs. 36.8%) injuries (all p < 0.0001). Injuries of the shoulder are less common in patients with abdominal (26.6% vs. 28.4%), pelvic (25.4% vs. 26.6%), or lower limb (35.5% vs. 38.2%) trauma (all p < 0.0001) (Fig. 2). Highlighting the thoracic injuries, shoulder injuries are associated significantly more often with severe thoracic injuries such as flail-chest, rib fractures, hemothorax, pneumothorax, lung contusion, and lung laceration (Fig. 3).

Analyzing the different entities of shoulder injuries in the shoulder group, the three most often recorded lesions were fractures of the clavicle 34%, scapula 26%, and proximal humerus 23%, followed by injuries of the nerves 4%, AC/SC-joint 3%, amputations 2%, vessel injuries 1%, and other (6%) (Fig. 4). With 83%, fractures make up the majority of shoulder injuries in severe trauma.

Concomitant injuries of the shoulder itself in the presence of proximal humerus fractures were frequently seen. Injuries to the scapula (11.3% vs. 9.2%), the AC/SC-joint (1.3% vs. 1.2%), nerves (6.6% vs. 0.9%), vessels (1.3% vs. 0.2%), and other (4.2% vs. 2.1%) (all p < 0.0001) occurred significantly more often in combination with a proximal humerus fracture. Whereas lesions of the clavicle (11.0% vs. 12.4%) (p < 0.0001) occurred less often in combination with a proximal humerus fracture (Fig. 5).

Reviewing and evaluating the outcome of both groups, the patients of the shoulder group spent on average 1.7 days more on ICU/IMCU and 2.1 days more in the acute care hospital (Table 1). On average, patients with shoulder injuries presented 1.7 more diagnoses than patients without shoulder injuries. According to our findings, the vast majority (85.5%) of our study population with shoulder injuries was discharged alive (Table 1).

The mortality rate decreased in the shoulder group (14.5% vs. 17.4%, p < 0.0001). In addition, a lower RISC II score was found in patients with shoulder injuries (15.5 ± 24.9 vs. 17.2 ± 27.1, p < 0.0001), highlighting the better prognosis of shoulder patients after multiple trauma. Furthermore, shoulder patients showed a more aggravated clinical course than non-shoulder patients, as they had a greater need for red blood cell concentrate (RBC) transfusions (24% vs. 21.4%, p < 0.0001) and were more likely to be admitted to the ICU/IMCU (91.7% vs. 93.5%, p < 0.0001). Patients in the shoulder group presented a GCS ≤ 8 less often than non-shoulder patients (27.4% vs. 28.3%, p = 0.0543) (all Table 1).

Concerning the operative treatment of lesions in shoulder trauma, our data showed that amputations (81.8%), vessel injuries (77.4%), and prox. humeral fractures (74.3%) were most likely to undergo surgical treatment. Clavicle fractures, nerve lesions, scapula fractures, and injuries to the AC/SC-joint were more often treated conservatively (Fig. 6). The rate of surgical treatment increased significantly with the severity of the injury (according to the documented AIS) (Fig. 7).

Extremity injuries have a high prevalence in severe multiple trauma, with 58.6% of multiple trauma patients presenting significant extremity injury. Affection of the clavicle is the third most common fracture in polytraumatized patients (10.4%), only surpassed by femoral (16.5%) and tibial (12.6%) fractures [2]. Previous studies already investigated lower limb and extremity injuries in severe trauma patients, indicating the need to analyze shoulder injuries in severe trauma [2, 17].

In this context, our findings can be summarized as followed.

Polytraumatized patients (ISS ≥ 16) with shoulder injuries:

The high prevalence of shoulder injuries (27.9%) in severely injured patients underlines the importance of understanding the main mechanisms and factors leading to shoulder injuries. Banerjee et al. already showed a 39.6% prevalence of upper extremity injury in polytraumatized patients [2]. Injuries of the shoulder girdle occur more frequently when compared to other upper extremity injuries in severe trauma, such as injuries of the hand (3.5%) [18] and fractures of the radius and ulna (15%) [2]. In our study of 15,115 patients with shoulder injuries, a clavicle fracture occurred most frequently (34%) followed by scapula fractures (26%) and proximal humerus fractures (23%). These findings are similar in some regards to Gottschalk et al. (44.3% clavicle fractures, 25.8% scapula fractures and 16.5% proximal humerus fractures) [7] and in contrast in some regards to Nordqvist et al. (53% proximal humerus fractures, 29% clavicle fractures, 3% scapular fractures) [13] and Veysi et al. (6.8% scapula fractures) [19]. In particular, scapula fractures are associated with high-energy trauma and are often accompanied by severe thoracic (rib fractures, pneumothorax, lung laceration), neurovascular injuries, spinal fractures and pelvic injuries in comparison to patients without scapula fractures [11, 20‐22], whereas scapula fractures do not increase the mortality [23]. Concerning concomitant injuries to the shoulder region itself, fractures of the clavicle occur more frequently together with scapula fractures in 25.2% than without the presence of a scapula fracture [11]. In our study, we analyzed concomitant injuries of the shoulder together with proximal humerus fractures that led to increased fractures of the scapula, but decreased fractures of the clavicle. Nevertheless, the deviations in the samples limit the comparability of the studies.

As initially hypothesized, the severity of the injury determines the rate of surgical treatment. Surgical therapy of proximal humerus fractures and injured vessels are very common. In contrast, scapula fractures and clavicle fractures underwent surgical therapy less often. Extraarticular scapula fractures represent approximately two-thirds of all scapula fractures [24] and are commonly treated conservatively [25]. In intraarticular scapula fractures, dislocation, or ipsilateral clavicle fractures (floating shoulder), surgery is the preferred treatment [26, 27]. Previous studies showed a good functional outcome after surgical treatment of complex fractures [28, 29]. The rate of opting for surgical treatment in amputations could be explained due to the “life before limb” strategy in severe trauma [30], as not all amputations received surgery. Unfortunately, detailed follow up of survival of amputated patients, or patients who underwent secondary surgical reconstruction of the amputated limbs could not be generated in the study and, therefore, patients might have died before a possible surgery. Nevertheless, depending on their injury, traumatic amputations and vessel injuries can quickly become life threatening and require immediate surgical treatment. Fractures of the proximal humerus in high-energy trauma are likely to present multiple parts and concomitant soft tissue and neurovascular injuries, leading to primary surgical treatment [31, 32]. A delay in the surgical treatment of proximal humerus fractures should be avoided, as that can lead to increased morbidity, length of hospital stay, and complications such as pneumonia and on-site infections [33]. In multiple injured patients, however, the decision to treat individual lesions surgically follows triage and damage control strategy [34]. This could also delay operative treatment of shoulder injuries. As polytraumatized patients present a variety of injuries, as well as systemic issues up to organ failure, the treatment might not only be decided due to the anatomic issue of the shoulder.

The associated concomitant injuries of shoulder injuries in the shoulder group aggravate the clinical course after severe multiple trauma. They received RBC transfusions, which are known to trigger complications and mortality dose dependence [35], significantly more often. Our findings confirm that shoulder injuries are strongly associated with injuries of the thorax, spine, and head (Figs. 2, 6). Thoracic injuries include the occurrence of pneumothorax, hemothorax, stable and unstable rib fractures, and pulmonary contusion and laceration. In American level 1 trauma centers, admitted patients with shoulder girdle injuries (mean ISS 17.8) presented concomitant thoracic injuries in 36.8%, and head injuries in 31.5% of the cases, respectively [7].

We hypothesize that the high correlation of thoracic injuries with shoulder injuries is caused by the anatomical proximity of these structures and, therefore, the thorax is likely to be simultaneously injured in a shoulder injury, and vice versa. Additionally, in the shoulder group we observed numerous motorbike accidents, which are known to increase the risk of thoracic injuries [36]. In severely injured patients, severe thoracic trauma increases the morbidity and mortality especially due to the increased risk of developing an acute respiratory distress syndrome (ARDS) [3, 37, 38]. Previous studies showed that up to 23.5% of thoracic injuries and 35.7% of scapula fractures are initially overlooked [4, 15]. Therefore, thoracic injuries should always be considered in the occurrence of shoulder injuries. Furthermore, the coexistence of moderate brain injury in combination with extracranial injuries in the polytraumatized patient leads to a doubled rate of mortality [39].

Due to severe concomitant injuries, our findings underline the importance of an early computed tomography scan (CT-scan) of severely traumatized patients, particularly as suggested by guidelines [5]. Additionally, a CT-scan-image-reconstruction (3D reconstruction) or CT-scan of the shoulder girdle is reasonable if there is any clinical or radiological suspicion of scapula fracture [40].

Nevertheless, structured and repeated clinical examinations (body check) remain a key aspect in acute trauma care, especially to identify concomitant injuries that may have been missed initially. Further studies showed that brachial plexus injuries may be present in 1% of multiple trauma patients [41]. With 4%, our data present a significant increase of nerve lesions in shoulder injuries. Injuries of the upper limb with neurological complications such as brachial plexus injuries frequently present severe functional disability in the follow-up and negatively affect the outcome [42, 43]. In a previous study of the Australian trauma registry, a prolonged stay, higher costs, and greater complexity of complications in patients with upper extremity injuries after major trauma were identified [44]. Extremity injuries, especially proximal humerus fractures, can cause long-term movement restrictions. This can lead to a loss of function and quality of life [45].

Focusing on the ISS and RISC II, shoulder patients presented a significantly increased ISS. Unexpectedly, the RISC II score and the mortality of the study population are lower in the shoulder group, and a contemporaneous increase with the ISS could not be shown. Initially, we assumed a higher RISC II and higher mortality in the shoulder group due to the increased ISS. Previous studies already showed a lower mortality rate in severely injured patients with scapular fractures and aggravated concomitant injuries [11, 23], but this remains controversial, as other authors showed an increased ISS and mortality rate in scapula fractures [15]. Nevertheless, the clinical relevance of an increased ISS in the shoulder group seems reasonable in correlation with a significant increase of concomitant thoracic, head, and spine injuries (Figs. 2, 6). In contrast, the non-shoulder group presented more abdominal trauma with a known mortality rate of up to 25% in severe trauma [46]. Blunt thoracic trauma only requires surgery in 10% of the cases [47]. Furthermore, an increased ISS followed by decreased mortality rate was observed in comparable studies on extremity and joint injuries [2, 17].

With regard to the higher ISS in the shoulder group, a previous study showed that a higher ISS could predict lower general health condition with respect to the long-term outcome after trauma [48]. However, it must be mentioned that the ISS has limitations in predicting the severity of the trauma as it does not represent physiological variables indicating shock symptoms, and multiple injuries in the same body region are not represented [49].

Regarding the mechanism of injury, traffic injuries have a huge impact on trauma cases worldwide and are the leading cause of death of young adults in Europe [50, 51]. This relevance is confirmed by our study, as the majority of our study population suffered from traffic accidents. Other national and international studies illustrate and support our findings, identifying traffic injuries as highly predictive for a traumatic affection of extremities, in particular upper extremity injuries [2, 52]. Furthermore, motorbike, bicycle, and pedestrian accidents have the highest incidence in our study population. Another study on motorbike accidents underlines our findings as motorbike accidents presented upper extremity injuries in 35% of their cases. Injuries of the shoulder girdle represent the largest group of upper extremity injuries, at 57% [10]. We assume that the unprotected exposure of the shoulder in motorbike, pedestrian, and bicycle accidents might be the main risk factor contributing to the significantly increased prevalence of shoulder injuries in these cases. In comparison, car and truck accidents and falls more often result in lower limb injuries [17, 53]. In car accidents, the so-called dashboard injury leads to major trauma of the lower extremity. The shoulder girdle is more protected in these injuries and, therefore, not frequently affected [17].

The present study has limitations, as the analyzed data is retrospective. As the participating hospitals have different levels of patient-centered care, the treatment after trauma could differ. As shoulder injuries could have been initially overlooked, there is a chance that shoulder injuries have been under reported. Furthermore, in polytraumatized patients, minor injuries may be omitted. The choice of diagnostics in the database leading to the diagnosis is not reported, so the accuracy of the data database is dependent on the individual examiner and submission of data in the register. Unfortunately, the exact specification of soft tissue injuries could not be classified.

In summary, our findings show that shoulder injuries in severely injured patients are frequently associated with severe concomitant injuries, mainly of the chest, head, and spine. High-speed traffic accidents are the most common injury mechanisms, particularly in motorbike, bicycle, and pedestrian accidents. Previous studies on extremity injuries of the TraumaRegister DGU® confirmed the increase of the ISS, duration of stay, and aggravated clinical course of extremity injuries [2, 17].

Shoulder injuries have an aggravating impact on the clinical course and prolong the clinical stay. As multiple trauma patients with shoulder injury present more diagnoses, the clinical management and treatment of the patient are aggravated. This is demonstrated by a higher initial ISS and longer stay on ICU/IMCU. Nevertheless, an increased rate of mortality in patients with shoulder injuries could not be identified. Our results correspond with empirical data in our daily clinical routine and other national and international findings in the literature. Furthermore, because of the large sample size of the analyzed study population and the high number of included trauma centers providing data, the clinical relevance of our findings seems significant. In the emergency room (ER) and in the tertiary survey, potential shoulder injuries and identified concomitant injuries should be closely considered.