Ipsilateral midshaft clavicle fracture and acromioclavicular joint dislocation: a review of literature and evidence-based diagnosis guidelines

Background: Ipsilateral midshaft clavicle fracture and AC joint dislocation are rare, with very few cases reported. Once the AC joint dislocation were missed diagnosis, the shoulder function may be affected and medical dispute was easy to occur. The aim of this study was to gather data relating to ipsilateral midshaft clavicle fracture and AC joint dislocation to develop evidence-based diagnosis guidelines as none are currently available. Methods: A study was conducted of the PubMed and Google Scholar databases to identify cases of ipsilateral midshaft clavicle fracture and AC joint dislocation. Data collected about each case included age and gender of the patient, mechanism of injury, fracture and dislocation classication. The authors report 2 additional ipsilateral midshaft clavicle fracture and AC joint dislocation cases. Results: 21 cases were identied for inclusion in this research, 19 from the literature and 2 reported by the authors. All the patients were injured by high energy trauma. For the midshaft fracture, 16/21 (76.2%) patients belonged to Type A classication, and 5/21 (23.8%) patients belonged to Type B classication. For AC joint dislocation, 11/21 (47.6%) patients belonged to Type IV classication, 4/21 (19.0%) patients belonged to Type VI classication, 5/21 (23.8%) patients belonged to Type III classication and 1/21 (4.7%) patients belonged to Type V classication. Conclusions: There are limited data available about the diagnosis of ipsilateral midshaft clavicle fracture and AC joint dislocation. From the cases reviewed, we nd that simple midshaft clavicle caused by high energy injuries may be associated with ipsilateral AC joint dislocation. Physical examination, careful observation of preoperative X-ray and uoroscopy including the AC joint during operation were key to diagnose the injury. of

Results: 21 cases were identi ed for inclusion in this research, 19 from the literature and 2 reported by the authors. All the patients were injured by high energy trauma. For the midshaft fracture, 16/21 (76.2%) patients belonged to Type A classi cation, and 5/21 (23.8%) patients belonged to Type B classi cation.
Conclusions: There are limited data available about the diagnosis of ipsilateral midshaft clavicle fracture and AC joint dislocation. From the cases reviewed, we nd that simple midshaft clavicle caused by high energy injuries may be associated with ipsilateral AC joint dislocation. Physical examination, careful observation of preoperative X-ray and uoroscopy including the AC joint during operation were key to diagnose the injury.
Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background
Mid-shaft clavicle fracture and acromioclavicular (AC) joint dislocation are very common injuries 17 . While concurrent injuries to both mid-shaft clavicle fracture and AC joint dislocation seem to be rare, most of the literatures 1-3, 5-10, 12-16, 18-22 are case reports. The latest review paper 11 reveals that incidence of ipsilateral clavicle fracture and AC joint dislocation is 6.8%, much more common than what was traditionally believed. This means that there are nearly 7 ipsilateral AC joint dislocation for every 100 midshaft clavicles. In order to avoid missed diagnosis of the AC joint dislocation, timely diagnosis of the unusual injuried is very important. There are currently no published evidence-based diagnosis guidelines or recommendations available The authors present a review of the literature relating to ipsilateral midshaft clavicle fracture and AC joint dislocation as well as 2 additional cases and for the rst time provide evidenced-based recommendations for the diagnosis of this rare injury

Methods
The study was conducted of the PubMed and Google Scholar databases to identify cases of ipsilateral midshaft clavicle fracture and AC joint dislocation. The references of relevant literatures were manually seeked to identify additional cases. Cases that included details about general conditions of the patient, mechanism of injury, fracture and dislocation classi cation, and radiological material were included in this research. Data collected about every case included age and gender of the patient, mechanism of injury, mid-shaft clavicle fracture and AC joint dislocation classi cation. The classi cation were identi ed by the description by author and judgment according to X ray. Except for the literature data, the authors report 3 more ipsilateral midshaft clavicle fracture and AC joint dislocation cases to add to the data analysis.
Data from all included cases were then tabulated to identify any mechanism of injury and classi cation There are 20 cases with the preoperative X-ray, and one case of the X-ray 9 reported by LANCOURT in 1990 was blurry and could not be used to con rm the classi cation. Thus, a total of 19 cases X-rays were adopted.
The rst reported cases of ipsilateral midshaft clavicle fracture and AC joint dislocation was published in 1992 by Wurtz 20 . He reported a series of 4 cases, all of whom sustained ipsilateral midshaft clavicle fracture and AC joint dislocation. Two patients were caused by falling from horse, one by Motor-vehicle accident and one by falling from bicycle. According to description of the author three of four patients had a Type-IV dislocation of the AC joint, one had a Type-II dislocation. The classi cation of the clavicle fracture was not described. According to the X-ray of case 1, the patten of clavicle fracture was type A according to OTA classi cation.
In 1995, Heinz et al 5 published a case of mid-shaft fracture of the clavicle with Type-IV AC joint dislocation, caused by landing directly onto the anterior aspect of his left shoulder in a track cyclist. The X-ray revealed that the mid-shaft clavicle fracture was oblique, type A classi cation. Juhn et al 6 described a type VI AC joint dislocation with middle-third clavicle fracture after impacting in ice hockey sport in a 21-year-old ice hockey player. The X-ray revealed that the mid-shaft clavicle fracture was oblique, type A classi cation.
Wisniewski 18 similarly described a type VI AC joint dislocation with midshaft clavicle fracture sustained after strucking on the back of the left shoulder by a passing car in a 32-year-old cyclist. The X-ray revealed that the midshaft clavicle fracture was oblique, type A classi cation.
Yeh PC et al 21 published a type IV AC joint dislocation with midshaft clavicle fracture after falling on a horse in a 46-year-old horseback rider. The X-ray revealed that the midshaft clavicle fracture was oblique, type A classi cation.
Kakwani RG et al 7 similarly described a type IV AC joint dislocation with midshaft clavicle fracture sustained by a road tra c accident in a 45-year-old man. The X-ray revealed that the midshaft clavicle fracture was spiral, type A classi cation.
More recently in 2011, Psarakis SA et al 12 published a type V AC joint dislocation with midshaft clavicle fracture caused by a road tra c accident in a 38-year-old man. The X-ray revealed that the midshaft clavicle fracture was spiral, type A classi cation.
In 2013, Woolf SK et al 19 published a type IV AC joint dislocation with midshaft clavicle fracture after ejecting through the open sunroof of a sport-utility vehicle in a high-speed rollover by a motor vehicle collision. The X-ray revealed that the midshaft clavicle fracture was spiral, type A classi cation. Grossi EA et al 4 published a type VI AC joint dislocation with midshaft clavicle fracture suffered a fall from a bicycle in a 19-year-old man. The X-ray revealed that the midshaft clavicle fracture was transverse, type A classi cation. Wijdicks CA et al 17 published a series of 2 patients, all of whom sustained ipsilateral midshaft clavicle fracture and AC joint dislocation. Case 1 was caused by motorcross bike accident with type B classi cation of the midshaft clavicle fracture, and case 2 was involved in a severe constellation of injuries from an ATV rollover, the patten of clavicle fracture was type B classi cation.
Paryavi E et al 11 reported a type IV AC joint dislocation with midshaft clavicle fracture in a rollover motor vehicle collision. The X-ray revealed that the midshaft clavicle fracture was transverse, type A classi cation. Beytemür O et al 1 published a type III AC joint dislocation with midshaft clavicle fracture in a rollover motor vehicle collision. The X-ray revealed that the midshaft clavicle fracture was oblique, type A classi cation.
In 2014, Solooki S et al 14 similarly described a type III AC joint dislocation with midshaft clavicle fracture after car turn over in a 40-year-old man. The X-ray revealed that the midshaft clavicle fracture was spiral, type A classi cation. Davies EJ et al 2 reported a type VI AC joint dislocation with midshaft clavicle fracture after a fall down stairs. The X-ray revealed that the midshaft clavicle fracture was spiral, type A classi cation. Tidwell JE et al 15 described a type IV AC joint dislocation in a 19-year-old man. He sustained direct impact to his right shoulder when driving an all-terrain vehicle after hitting a bridge and. The X-ray revealed that the midshaft clavicle fracture was oblique, type A classi cation.
In 2015, Madi et al 9 published a type IV AC joint dislocation with midshaft clavicle fracture a road tra c accident. The X-ray revealed that the midshaft clavicle fracture was oblique, type A classi cation. Sharma et al 13 described a type III AC joint dislocation with midshaft clavicle fracture and mid shaft humerus fracture sustained by a high velocity road tra c accident in a 65-year-old man. The X-ray revealed that the midshaft clavicle fracture was oblique, type B classi cation.
In 2017, Dong et al 3 reported a case of simultaneous bilateral midshaft clavicle fractures with left dislocation of the acromioclavicular joint (type IV classi cation ) aof the midshaft clavicle fracture, type B classi cation.

Authors' case 1
A 51-year-old female presented after a high-speed motor vehicle accident. He sustained his shoulder with marked ecchymosis, swelling, and tenderness at the mid-clavicle. The neurovascular status of the right upper extremity was normal. The X-ray (Fig. 1a) revealed that the left midshaft clavicle fracture was type B classi cation. ORIF was performed and the ipsilateral AC joint dislocation was found. Two k-wires were utilized for xing the AC joint (Fig. 1b). The k-wires were removed three months after the operation, the Xray showed the AC joint was normal (Fig. 1c).

Authors' case 2
A 43-year-old female was involved in a road tra c accident and suffered an injury to his left shoulder. He complained of his shoulder with marked ecchymosis, swelling, and tenderness at the mid-clavicle. The neurovascular status of the left upper extremity was normal. The X-ray (Fig. 2a) and CT (Fig. 2b) revealed that the left midshaft clavicle fracture was oblique, type A classi cation. After ORIF for midshaft clavicle fracture, the X ray postoperation reavealed of type III AC joint dislocation (Fig. 2c). Reviewed the preoperative X-ray (Fig. 2a, red circle), the gap of injuried AC joint widens signi cantly compared with the normal AC joint. Thus the preoperative type IV AC joint dislocation was missed diagnosis.
A summary of all 25 cases can be seen in Table I.

Discussion
The incidence of ipsilateral midshaft clavicle fracture and AC joint dislocation was not as low as one thought. Ottomeyer 11 has reported that the incidence of this injury is 6.8%, and the retrospective research reveals that the incidence of this injury is 3.0%. Although the incidence is lower than Ottomeyer report 11 , caution should be taken when treating midshaft clavicle fracture.
In order to obtain the relative true injury data, case reports 1-3, 5-10, 12-16, 18-22 which have the entire case data were selected, to analyze the features of midshaft clavicle fracture and AC joint dislocation.
According to the literatures about ipsilateral midshaft clavicle fracture and AC joint dislocation, it was found that all midshaft clavicle fractures belong to the relatively simple pattern of this injury. The majority of AC joint dislocation are type IV (10/19) and VI (4/19) which should be caused by direct high energy trauma on the shoulder. The mechanism of ipsilateral midshaft clavicle and AC joint dislocation is complex and has not been described so far. Few cases may be the major reason. Through the analysis of all the cases reported by various authors from different countries, it was found that all the patients were injured by high energy trauma, associated with relatively simple midshaft clavicle fracture and different type of AC joint dislocation. The study considered that the mechanism is direct high energy impact for shoulder combined with simultaneous torsion with the trunk. The direct trauma causes the AC joint dislocation rst, the high energy on the shoulder caused serious AC joint dislocation, then the trauma energy was transmitted towards medial of AC joint when torsion impact occurred, and the energy became weak. The midshaft clavicle is the mechanical weakness, midshaft clavicle fracture is prone to break with the spiral, oblique or wedge clavicle fracture.
Interestingly, the classi cation of AC joint dislocation identi ed by literatures 1-3, 5-10, 12-16, 18-22 is very different from the only review paper. Ottomeyer 11 reported that 18/26 were type II AC joint dislocation, 7/26 were type III and 1/26 was type V in the injury of ipsilateral midshaft clavicle fracture and AC joint dislocation. It was found that type IV and type VI AC joint dislocation were more common according to the literutures. There are several possible reasons, the rst is that the example reported by case report may be more severe for acromioclavicular joint dislocation, and imaging diagnosis is very clear, so it is easy to accept and publish. The second is that type II AC joint dislocation sometimes is not very easy to diagnose. This means that some cases of ipsilateral midshaft clavicle fracture and AC joint dislocation may be diagnosed with a clavicle fracture, the type II AC joint dislocation is easy to be misdiagnosed.
For ipsilateral midshaft clavicle and AC joint dislocation, the timely and correct diagnosis of AC joint dislocation is a key point. According to Rockwood classi cation, type III, V and IV injuries are easy to be diagnosed, while type II and IV are prone to be misdiagnosed. The type II AC joint dislocation may be changed to type III after xation of midshaft clavicle fracture, the noncontoured plate or iatrogenic injury of the coracoclavicular ligament is the possible reason. The type IV AC joint dislocation is not a common injury, caused by high energy injury with coracoclavicular ligament rupture, deltoid and trapezius tear injuries from distal clavicle. The distal clavicle is displaced towards the posterior position, thus sometimes it is prone to ignore this injury through the X-ray. When the gap of AC joint widens, type IV AC dislocation should be considered. Physical examination and CT scan can help in diagnosis.
Once the ipsilateral AC joint dislocation was found intraoperation, the k-wires can be used to x the AC joint. The incision needs to be extended laterally, expose the AC joint, clear the hematocele and soft tissue and then reduce the AC joint. Two k-wires were inserted from acromion to distal clavicle. After 3 months postoperation, the k-wires are recommended to be removed so that they won't splinter.
There are several substantial limitations to the study. First, the conclusions may not be generalizable because of the small number of cases. Second, identi cation of the midshaft clavicle fracture classi cation may not be very accurate, because some images were not very clear, identi cation for type  Table   Table I is not available with this version of the manuscript. Figure 1 a. one patient was diagnosed with midshaft clavicle fracture pre-operation. b. the ipsilateral AC joint dislocation was found intra-operation, and two k-wires were utilized for xing the AC joint. c. k-wires were removed three months after the operation.