Displaced acromion fracture associated with anterior glenohumeral subluxation in a polytrauma patient: a case report

Background: Fractures of the acromion process of the scapula are a rare entity that account for approximately 7% to 16% of all scapula fractures, which in turn account for 0.5% to 1% of all fractures in the body. These fractures usually occur from direct trauma to the shoulder or as a result of overuse injuries to the shoulder joint. Given the rare incidence of these fractures, there are currently no treatment guidelines for treating these fractures when diagnosed. Case presentation: In this case report, we discuss how a secondarily diagnosed displaced acromion fracture associated with anterior glenohumeral joint subluxation in a polytrauma patient was surgically treated. After surgical xation of this fracture and accordingly neutralizing all the dislocating tension forces exerted by the deltoid muscle, the glenohumeral joint was spontaneously relocated postoperatively. Conclusion: Patient with shoulder trauma should be carefully examined for acromion fractures. Acromion fractures can be treated with good results with early surgical treatment and proper xation. Surgical treatment is important to regain shoulder functions, as it enables early rehabilitation.

forces exerted by the deltoid muscle, the glenohumeral joint was spontaneously relocated postoperatively.
Conclusion: Patient with shoulder trauma should be carefully examined for acromion fractures. Acromion fractures can be treated with good results with early surgical treatment and proper xation. Surgical treatment is important to regain shoulder functions, as it enables early rehabilitation.

Introduction:
Fractures of the acromion process of the scapula are a rare entity that account for approximately 7-16% of all scapula fractures, which in turn account for 0.5-1% of all fractures in the body (1)(2)(3). The acromion is a large bony process located at the superior end of the scapula, projecting anteriorly to allow articulation with the lateral end of the clavicle. These fractures usually occur from direct trauma to the shoulder or as a result of overuse injuries to the shoulder joint. Given the rare incidence of these fractures, there are currently no treatment guidelines for treating these fractures when diagnosed (4).
In this case report, we discuss how a secondarily diagnosed dislocated acromion fracture associated with anterior glenohumeral joint subluxation in a polytrauma patient was surgically treated.
This case report is in compliance with the SCARE guidelines for case reporting (5).
Case Report: The patient was a 63-year-old Caucasian male who was hit by a truck while riding his bicycle. Upon the arrival of the paramedics and trauma surgeon at the scene, the patient had a Glasgow Coma scale score of 4 and an Injury Severity Score of 24.The patient was intubated and transported via helicopter to the emergency department of our Level I Trauma center. The patient presented in our emergency department intubated with a right Gastillo grade IIIB open elbow fracture. After performing a full body trauma computed tomography (CT) scan, the patient was treated according to damage control orthopedic principles. The open elbow wound was debrided, an elbow-spanning external xator was applied, and a vacuum-assisted negative-pressure wound coverage was used. Postoperatively, the patient was transferred to our ICU. Collateral history revealed that the patient was an otherwise healthy, non-smoking, non-drug using, right-handed guitar teacher. According to his legal guardian, the patient had a fully functional right shoulder joint that had no prior trauma or surgery and was never a source of pain, discomfort, or limitation. The patient relied heavily on his right upper extremity in his daily living as a musician. While the patient was sedated and intubated in the ICU, examination revealed right shoulder swelling and bruising with otherwise intact skin. However, it was 6 days after admission, during positioning for a routine wound debridement of the right elbow, that the treating surgeon noted that the shoulder joint seemed unstable. This intraoperative assessment was con rmed by an incidental nding on a chest x-ray performed directly after the operation. Examination of the x-ray showed a displaced acromion fracture ( Fig. 1) that was not detected on the primary polytrauma CT scan. Accordingly, a dedicated CT scan of the shoulder was performed on the following day. At that time, a right displaced acromion fracture associated with an anterior subluxation of the glenohumeral joint was diagnosed ( Fig. 2). The acromion fracture was type I according to the Ogawa classi cation, type 3 according to the Kuhn classi cation, and type A1.2 according to the AO/OTA. Based on the new ndings and after discussing the treatment options with the legal guardian of the patient, we proceeded with surgical xation of the acromion to restore shoulder stability. The operation was performed in the beach chair position. The detached fragment of the acromion was rst localized under uoroscopy, and two 2 cm skin incisions were made, one anterior and one posterior on the lateral aspect of the fragment. Next, a 1.5 mm diameter cable was threaded through a 4-hole plate, and the plate was passed through the incisions to sit on the lateral aspect of the acromion. A second pair of 2 cm skin incisions was made for the medial, intact acromion, one anteriorly and one posteriorly. A 2 mm hole was drilled through the medial acromion from anterior to posterior adjacent to the acromioclavicular joint. Subsequently, a second 1.5 mm cable wire was threaded through the anterior skin incision, through the 2 mm drill hole, and out of the posterior skin incision. Finally, both anterior and posterior ends of the cable wire lateral to the acromion fragment were shuttled subcutaneously and were then pulled out of the anterior and posterior incisions medial to the acromion fragment using a clamp allowing the 2 anterior ends of both cable wires and the 2 posterior ends of both cable wires to be tightly intertwined together, and the 4-hole plate, previously placed at the lateral end of the displaced acromion fracture, to be pulled directly against the lateral acromion ( Fig. 3A-D).
By sequentially increasing the tension on the anterior and posterior intertwined cable wires, the previously displaced fragment was able to be brought in direct contact with the intact medial acromion and the dislocating tension forces of the deltoid were then neutralized. Accordingly, an anatomical reduction of the acromion fracture was not necessary. Both ends of the intertwined cable wires were then shortened, bent, and buried subcutaneously. Fluoroscopy was used to check the reduction and xation of the acromion fragment, and all 4 skin incisions were closed in layers.
The intraoperative x-rays showed a reduced acromion, which in turn resulted in an anatomically articulating glenohumeral joint surface. This was also documented by the postoperative CT scans (Fig. 4). Postoperatively, the patient returned to the ICU, where he was further monitored until he was eventually transferred to a neuro-rehabilitation center for further rehabilitation. The patient later presented 3 months post operatively for re-implanting the skull after the initial craniotomy and accordingly a follow up CT was performed. The CT scan showed a healed acromion fracture and an anatomically articulating glenohumeral joint surface. Unfortunately, the patient wasn't able to recover cognitively from his head trauma and accordingly no clinical examination of the shoulder could be made.

Discussion:
Acromion fractures in polytrauma patients can be easily overlooked and the diagnosis is often delayed. When inadequately treated, these fractures may eventually lead to pain, limited range of motion, subacromial impingement, as well as rotator cuff injury (6).
Acromion fractures can be classi ed based on one of three classi cation systems. Ogawa and Naniwa classi ed acromion fractures based on their location in regards to the spinoglenoid notch, in which fractures lateral to the notch are Type 1 and fractures medial to the notch are Type 2 (7). Kuhn et al., on the other hand, used a classi cation algorithm based on fracture displacement. Accordingly, acromion fractures where classi ed as follows: Type 1, minimally displaced; Type 2, displaced without impacting the subacromial space; and nally Type 3, displaced with a reduction of the subacromial space (8). The AO/OTA classi cation system is based on the level of fracture comminution as well as fracture displacement (9). In our case report, the acromion fracture is classi ed as Type I according to Ogawa since the fracture is lateral to the spinoglenoid notch, Type 3 according to Kuhn since it was a displaced fracture resulting in reduction of the subacromial space and A1.2 according to AO/OTA since it is an extra-articular segmented fracture.
Since these fractures are rare, there is no suggested treatment guideline, and accordingly, there is no preferred or recommended surgical approach. Acromion fractures can be treated with K-wire xation, tension band constructs, cannulated screws, or plate-and-screw constructs. Goss recommended the use of tension band technique and reported good results (1). Hill et al. used a plate for all acromion fractures in a study of 13 patients with good patient satisfaction, with only one case in which the plate was removed due to implant irritation (4). In addition, Zhu et al. recommended the use of perpendicular double-plate constructs with a locking system after evaluating this approach in a study including 9 patients with Type 3 acromion pedicle fracture with a displacement of more than 1 cm. In their study, Zhu et al. reported favorable results with good patient satisfaction rates and good Constant and DASH scores in their patients (10). In our case, we chose a combination of plate and cerclage wires, since this was an avulsion fracture of the lateral aspect of acromion with comminution.
When surgical intervention is indicated for fractures of the acromion is also a matter of debate. It is unclear if we should be more aggressive with such fractures and offer early surgical treatment, or we should take a more conservative approach and only intervene when the conservative therapy seems to be inadequate. A study by Kim et al. compared early and late surgical treatment of acromion fractures in 353 patients and found that all the patients who were surgically treated at an earlier time showed favorable pain and functional outcome scores, with all patients returning to their pre-fracture activities (11).
Conversely, Hill et al. showed that the patients who underwent delayed treatment of acromion fractures were also able to return to their pre-injury function levels, similar to patients treated acutely (4). In our case, since the glenohumeral joint was under tension forces from the deltoid muscle which resulted in anterior subluxation of the joint, we opted for surgical treatment. We observed that after reducing the acromion fracture, these displacing tension forces of the deltoid muscle were subsequently neutralized, which in turn resulted in an anatomically articulating glenohumeral joint. Moreover, in an attempt to prevent any further injuries to the muscle itself, we opted for a minimally invasive approach to preserve the deltoid muscle integrity and function.
Unfortunately, our patient had major head trauma and was directly transferred to a neurological rehabilitation center, and as such, we could not assess the patient's satisfaction or collect functional outcome scores.

Conclusion:
Patient with shoulder trauma should be carefully examined for acromion fractures. Acromion fractures can be treated with good results with early surgical treatment and proper xation. Surgical treatment is important to regain shoulder functions, as it enables early rehabilitation. Unfortunately, in our case we could not provide any statement on the clinical follow up since the patient wasn't able to recover his cognitive abilities and accordingly was in a persistent state of coma.

Declarations
Ethical approval: Not applicable. A signed consent form from the guardian of the patient is available upon request.

Figure 1
Initial diagnosis of acromion fracture on the right side as an incidental nding on chest x-ray, where on the left is the initial chest x-ray and on the right the x-ray 6 days after admission.

Figure 2
Representative CT scan slice 3D reconstruction showing the displaced acromion fracture, the coracoid process fracture as well as the anterior glenohumeral subluxation.  Representative postoperative CT scan slices in the coronal and axial planes and 3D reconstruction showing the surgically anatomically reconstructed acromion leading to reduction of the glenohumeral joint.

Figure 5
Representative CT scan slices three months postoperatively in the coronal and axial planes healed acromion fracture.