Epidemiology and treatment of acute elbow dislocations: current concept based on primary surgical ligament repair of unstable simple elbow dislocations

Purpose Acute elbow dislocations are complex injuries that predispose to chronic instability and pain. The ideal treatment strategy is part of controversial discussion and evidence-based recommendations for the treatment could not be concluded from the literature. The purpose of the present study was to assess current epidemiological data, injury pattern, and the changing trend for treatment. Methods This study presents a retrospective review of 72 patients ≥ 18 years of age who were treated in our level I trauma centre with acute elbow dislocations from 2014 to 2018. The data were acquired by analysis of the institution’s database, and radiological examinations. Results The average age of the patients was 48.5 years (range 18–86). The ratio of male to female patients was 1.9:1. A fall onto the outstretched arm (42%) was the most common injury mechanism. By classification, 42% of the elbow dislocations were simple, and 58% complex. A total of 85% of patients underwent surgery including 73% of the simple elbow dislocations due to remaining instability or non-congruency of the reduced elbow. The indication for surgical treatment correlated merely with the grade of instability and displacement, but not with age. Conclusion Acute elbow dislocations need identification of the precise injury pattern and instability after reduction of the elbow joint. To achieve a congruent and stable joint, we recommend primary surgical repair as first-line treatment for patients with unstable simple and complex elbow dislocation independent of age.


Introduction
The treatment of acute elbow dislocations is a challenge due the complex interaction between the bony articulations of the elbow joint, the capsuloligamentous structures, and dynamic muscle restraints [1]. Comprehension of the elbow anatomy and the relative contribution of the various elements to elbow stability is important in developing an algorithm for diagnosis and treatment [1]. Additionally, early recognition of the precise injury pattern is critical in restoring elbow function and preventing chronic instability and pain [2]. Despite improvement in understanding of these lesions and a recent increasing trend for early surgical ligament repair, evidence-based recommendations for the treatment could not be concluded from literature [3]. This study was performed to better characterise the current epidemiology, injury pattern, and the trend for surgical treatment of these injuries as important step towards definition of a robust treatment algorithm.

Patients and methods
Approval from the institutional review board of the medical faculty (GN19-390) was obtained prior to performing this retrospective study. The study included all patients ≥ 18 years of age with acute elbow dislocations who were treated in our level I trauma centre according our treatment algorithm between 2014 and 2018 ( Fig. 1).

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The data were collected by analysis of the institution's database, and radiological examinations. Information obtained included age, gender, injury mechanism, injury pattern, and mode of treatment. Concerning the injury mechanism, low-energy trauma (i.e., fall from standing or seating height), and high-energy trauma (i.e., fall from height greater than standing, motor vehicle accident, sport accident, bicycle accident) were distinguished.
Elbows were usually reduced in the emergency department under analgesia and conscious sedation. After reduction, a comprehensive examination of the joint stability was performed under anaesthesia. Radiographs were performed after reduction in all cases. Stable and reducible injuries were treated conservatively. The indication for surgical treatment included: (1) radiological subluxated or non-congruent joint after reduction, (2) elbows that required an extension limitation over 30° to 45° to maintain reduction, (3) detected instability under anaesthesia, and (4) displaced complex elbow dislocations. All operative patients were treated by surgeons specialised in orthopaedic trauma care.
In non-operative patients, early mobilisation occurred using a hinged orthosis within 2 weeks after trauma. After operative treatment, a long arm cast was applied for 2 weeks. Afterwards, a hinged orthosis was recommended for 4 weeks. Extension was limited for 3 weeks and gradually increased. Forced supination and pronation were restricted for 6 weeks. Full weight-bearing was allowed after a total period of 12 weeks.
Statistical evaluation was performed using chi-square test and Fisher's exact test. Values of p < 0.05 were considered statistically significant.

Distribution of age versus injury pattern
Evaluating the distribution of age versus injury pattern, 42% (24/57) of adult patients sustained simple elbow dislocations, and 58% (33/57) complex elbow dislocation, versus 40% (6/15), and 60% (9/15) of the elderly patients. The differences were not statistically significant (p = 0.883). This indicates that adult and elderly patients were just as likely to sustain complex elbow dislocations.

Distribution of injury mechanism versus injury pattern
Analysing the distribution of injury mechanism versus injury pattern, 63% (19/30) of the patients with lowenergy trauma sustained simple elbow dislocations, and 37% (11/30) complex elbow dislocations, respectively, 26% (11/42), and 74% (31/42) in cases of high-energy   trauma. Thereby, the percentage of complex elbow dislocation increased significantly (p = 0.002) with the intensity of the injury mechanism, at the expense of simple elbow dislocations.

Distribution of age versus mode of treatment
A total of 85% (61/72) of patients underwent surgery. Evaluating the relationship between age and mode of treatment, 84% (48/57) of the adult patients were treated operatively versus 87% (13/15) of the elderly patients. The difference was not statistically different (p = 1.000). Therefore, in the present study population, elderly patients were not less likely to get surgical treatment as compared to adult patients.

Discussion
Age and gender are both important factors for defining risk for sustaining acute elbow dislocations [4,5,8]. Previous studies have indicated a male predominance in the occurrence of elbow dislocations and a significantly higher risk for this injury for adult patients [8,9]. The results of the present study were congruent showing predominantly male patients and a similar age profile.
Most elbow dislocations are the result of falls onto the outstretched arm [3,6,8,10]. Our data were similar in elderly patients with 73% of the elbow dislocations occurring as the result of a fall. However, in the adult population, high-energy trauma was the most common cause of injury (67%).
Posterior dislocations have proven to be the most common direction of displacement by far and can be further subdivided into posterolateral and posteromedial, of which posterolateral accounts for over 80% [3,11]. The results of the present study were consistent with 79% posterior dislocations, thereof 71% posterolateral.
Concerning injury pattern, the literature indicates that simple elbow dislocations are the most common type of injury, and up to 20% of dislocations are associated with fractures [3,12]. Our data were different with a higher rate (58%) of complex elbow dislocations. This could be due, in part, to our higher proportion of high-energy trauma in the adult population.
Simple elbow dislocations are mainly treated with conservative management in current literature [3,7,[13][14][15]. Many authors have reported favorable results after conservative treatment for simple elbow dislocations [10,13,16,17]. Additionally, some studies have reported more satisfactory results after conservative treatment compared to surgical management [11,18]. However, indication for surgical repair is generally recommended in unstable elbow dislocations, in which primary ligament repair demonstrated satisfactory outcomes [11,17,[19][20][21]. Therefore, it is standardly indicated to determine the treatment method of simple elbow dislocations according to the stability after reduction of the elbow joint [7,17]. If the elbow is radiological subluxated or non-congruent after reduction, unstable under anaesthesia, or requires an  extension limitation over 30-45° to maintain reduction, unstable simple elbow dislocation has to be diagnosed, recommending early ligament repair [7]. Our data were consistent, but the percentage of patients with unstable simple elbow dislocations was higher compared to current data. In our study cohort, surgery had to be performed in 73% of the simple elbow dislocations due to remaining instability or non-congruency of the reduced elbow. Congruently, disruption of both the medial and lateral collateral ligament was detected in 45% of the cases compared to isolated medial in 45%, and lateral in 9%. The treatment principles of complex elbow dislocations are mainly reduction of the joint, stabilisation of associated fractures, and early motion [2,4,12]. Ligament repair and hinged external fixators are necessary in some cases to restore stability for early motion [11,12,[22][23][24]. The results of the present study were similar. Screws (41%) predominated the surgical treatment of the radial head compared to transosseous suture (43%) for the ulnar coronoid process, and locking plate (90%) for the olecranon. Ligament repair with suture anchor occurred in most complex elbow dislocations (74%), while protective fixation was applied in 28%.
Age has been shown to be a major determinant of nonoperative management [25]. Contrary, in the current study, elderly patients were just as likely to get surgical treatment as adult patients due to a variety of reasons. First, the high percentage of complex elbow dislocations (60%). Second, it was also due to a personal request of the elderly patients who are now more active than ever and often prefer surgical treatments that do not hamper their activities.
Some limitations must be considered for the present study. First, the study design was retrospective. Second, our data provided no information on outcomes. Even though this study contributes to currently available epidemiological data, the definite answer regarding appropriate algorithm for treating acute elbow dislocations requires prospective long-term outcome studies.

Conclusion
In conclusion, the treatment method of acute elbow dislocation has to be determined according precise injury pattern and instability after reduction of the elbow joint. To achieve a congruent and stable joint, we recommend primary surgical repair as first-line treatment for patients with unstable simple and complex elbow dislocation independent of age.
Funding Open Access funding enabled and organized by Projekt DEAL.
Code availability Not applicable.

Compliance with ethical standards
Conflict of interest N. Mühlenfeld, J. Frank, T. Lustenberger, I. Marzi, and A. L. Sander declare that they have no conflict of interest.

Availability of data and material Not applicable.
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