Fractures of the clavicle constitute 2.6% of all adult fractures1. There is an increasing trend toward fixation of midshaft fractures, the most common subgroup2,3. Techniques include plate fixation, intramedullary screw fixation, and elastic nail osteosynthesis. Reported complications include wound dehiscence, infection, arterial injury4-7, and neurological injury8.
An air embolus can occur as air enters from the surgical site into the venous system down a pressure gradient9. Diagnosis is difficult; outcomes range from subclinical to fatal and relate to the volume and rate of entrainment. An embolus can obstruct the right ventricular outflow and is associated with high mortality. It is particularly frequent with beach-chair positioning during posterior fossa neurosurgery10.
To our knowledge, no prior report of this phenomenon exists in the context of clavicle surgery, despite the risks involved with patient positioning and surgical anatomy. We report a fatal case of air embolus secondary to subclavian vein injury during fixation of a midshaft clavicular fracture (performed by an independent surgeon) and suggest ways to prevent this complication. The family was informed that data concerning the case would be submitted for publication, and they provided consent.
A thirty-four-year-old man fell from a boat and sustained an isolated displaced midshaft clavicular fracture. He was referred to an orthopaedic surgeon. Approximately six weeks later, he had no clinical or radiographic signs of healing, and he underwent open reduction and internal fixation.
A general anesthetic was administered, and the airway was secured with a laryngeal mask. No nitrous oxide was used. A cervical block was administered. The patient was positioned without the head up, but a sandbag was placed under the affected shoulder. The clavicle was exposed with use of a straight incision in the line of the clavicle and taken down to bone. A six-hole locking lateral clavicle plate was positioned superiorly. Locking drill guides were utilized. A Bristow elevator (Fig. 1), which was held by an assistant, was placed on the inferior surface of the clavicle to protect against inadvertent drill penetration. The final screw was the most medial. On withdrawal of the drill from this site, profuse low-pressure bleeding was noted.
The plate was removed, and the subclavian vein was exposed by rotating the medial aspect of the clavicle. A tear in the vein was identified. The bleeding was controlled with vascular loops that were placed proximal and distal to the tear. Despite control of the bleeding and aggressive fluid resuscitation, the patient went into shock. He was intubated, and a presumptive diagnosis of pneumothorax was made. A chest tube was inserted, but no pneumothorax was found. A vascular surgeon urgently explored the subclavian vein and artery. There was no ongoing hemorrhage or other injury. No vascular repair attempt was made since the patient was deteriorating rapidly and a cause had not yet been identified. A central venous line was inserted, and air was aspirated from the right atrium, suggestive of an air embolus. Despite these measures, the patient did not respond and was declared deceased one hour later.
The case was referred to the coroner. The report stated that the cause of death was an “air embolism and severe hemorrhage” as a result of “perforation of the right subclavian vein.” Findings included 20 to 30 mL of air in the right atrium and a 25-mm perforation of the subclavian vein directly below the most medial screw hole.
This case demonstrates the risk of iatrogenic injury to the subclavian vein, resulting in a fatal air embolus during surgical fixation of a clavicular fracture. The risk of vein injury depends on (1) the anatomy of the subclavian vein (relative location and proximity to the clavicle), (2) the anatomy of the clavicle (dimensions relevant to drill depth), and (3) the surgical technique (control of instrument depth and trajectory).
The subclavian vessels follow an oblique course along the length of the clavicle. At the medial end, the vein lies posterosuperior to the clavicle, and passes inferior to it at the lateral end (Fig. 2). The vein lies anterior to the artery, closer to the posterior border of the clavicle and thus at higher risk for injury11.
The subclavian vein is located at a mean of 4.8 mm behind the medial third of the clavicle12. It can be adherent to the clavicle (Table I). This relationship may be distorted in delayed fixation, nonunion, infection, or revision surgery. The vein may be closer or scarred to the clavicle after fracture, presenting a higher risk for iatrogenic injury from drills, retractors, or aggressive dissection.
The at-risk trajectory is a range since the subclavian vein is a tubular structure (Fig. 3)13. However, the principle remains that the vein lies posterior to the clavicle medially, and inferior to it laterally.
Also important to the risk of drill penetration is the fact that clavicle dimensions are highly variable. The smallest diameter may be as little as 6.7 mm in the mid-diaphysis14. If the subclavian vein is adherent to the clavicle, as can occur with delayed fracture surgery, a drill penetration of just over 6.7 mm may damage the vein.
Drill stops have been suggested to minimize the risk of “plunging”14, but they do not guarantee safety. Safety relies on the exact length of the drill stop, which is difficult to determine preoperatively. Surgeons may advance the drill without taking due care for anatomic variability and also may not drill across the widest diameter (or the center) of the medulla12. Preoperative measurement of clavicle depth on a radiograph can provide a guide.
Blunt retractors are used as protection on the far side of the clavicle but require more dissection15, and were not effective with this patient. It is also conceivable that the dissection required to place the retractor played a role in the tearing of the vein. An effective retractor must be correctly positioned in order to contain and prevent deflection of the drill-bit. Digital palpation on the undersurface can be used, but it poses a direct risk to the surgeon.
Unicortical screw fixation would eliminate the risk of vessel penetration. In an experimental sawbone model, the unicortical fixation failed because of pullout of the screws from the bone, which was not seen in bicortical fixation16.
When practical, the drill should be aimed away from the subclavian vessels. A superior plate is safest medially12. An anterior plate may be best for the middle and lateral thirds of the clavicle where the vein is inferior17. Although the vessels lie farther away from the clavicle laterally and are at lower risk, an accidental “plunge” with a drill could injure them. A custom plate designed with a “twist” and placed on the superior surface medially and the anterior surface laterally would provide the ideal trajectory for avoiding vascular injury. However, the fracture configuration may prevent the ideal orientation of such a plate.
An intramedullary nail may reduce the risk of vessel injury. However, perforation with the reamer or nail could occur. Intramedullary nails are unsuitable for some fracture configurations18.
Currently, we recommend the following approach: (1) assess risk factors (e.g., small clavicle, medial fracture, osteoporosis, comminution, nonunion, malunion, previous surgery, or infection), (2) perform a three-dimensional computed tomographic angiogram in high-risk patients, (3) advise the anesthetist of the risk preoperatively and prior to drilling, (4) perform subperiosteal dissection of the clavicle so the drill and screws can be visualized at the perforation of the second cortex, (5) do not breach the posterior periosteum because it acts as a layer between the instruments and vessels, (6) use a new or sharp drill-bit for each case, (7) direct the drill inferiorly for the medial screws and posteriorly for the lateral screws, and (8) advance the drill slowly with high revolutions per minute, paying attention to the change in pitch and feel to determine when the drill is almost through the second cortex.
Risk factors for air embolus involve any event that increases the pressure gradient between the surgical site (atmospheric pressure) and venous system (right atrial pressure). This includes negative intrathoracic pressure19, hypovolemia11, and positioning in which the operative site is higher than the right atrium. The subclavian vein retains its patency because of its soft-tissue attachments, allowing large volumes of air to enter if it is injured11.
Measures to prevent air emboli include maintaining normovolemia, avoiding venous injury, and strict hemostasis20. Management of air embolus is aimed at preventing additional air entry. The wound should be submerged in saline solution. The patient should be immediately placed into a Trendelenburg (head down) position and then rolled with the left side down. Rolling the patient to the left attempts to move the embolus away from the right ventricular outflow tract21. Positive pressure ventilation can be considered. A right atrial catheter can aspirate air and reduce bubble size22. The vessel needs to be rapidly controlled. An urgent referral to a vascular surgeon is recommended. An occlusive dressing may prevent additional air entry but does not allow surgical access23.
Based on the anatomy, surgical techniques, and nature of an air embolus in clavicular fracture surgery, we recommend the following preventative methods: (1) to enhance awareness, provide education concerning the risk as well as preoperative planning to assess clavicle dimensions and vascular anatomy, (2) use subperiosteal dissection, and (3) use a drill trajectory aimed inferiorly in the medial third, and posteriorly in the central and lateral thirds if possible.
If an injury occurs, we recommend aggressive resuscitation, submerging the wound with saline solution to prevent air entry, placing the patient in the Trendelenburg position, intubation, and exploration and repair of the vessel. A high index of suspicion and early vascular surgical referral is required. Although serious, an air embolus remains a rare complication, and standard operative techniques remain appropriate for open reduction and fixation of clavicular fractures.
Note: The authors extend our condolences to the family and thank them for encouraging medical review. We thank the Coroner’s Office for assistance in providing information on this case and the treating surgeon who supported this publication. In addition, we also thank Dr. Philip Duke, President of the Shoulder and Elbow Society of Australia 2010-2012, who was an expert witness to the Coroner’s Court and facilitated this review.
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Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.