Iatrogenic Vertebral Artery Injury during
Anterior Cervical Spine Surgery

A surgical technique called the anterior approach is utilized to address a range of conditions affecting the cervical spine, such as degenerative disorders, injuries, tumors, deformities, and infection.

The Smith-Robinson approach, which was first reported in 1955 and later modified by Southwick and Robinson in 1957 to reach C3 to T1, is likely the most commonly employed method. The anterior approach is a practical and convenient option for addressing pathologies originating from the anterior cervical spine.

It provides excellent exposure to multiple levels of the spine, allows thorough neural decompression, and enables solid reconstruction of the vertebral column. Anterior cervical procedures are frequently used to perform anterior cervical discectomy and fusion (ACDF) as well as anterior cervical corpectomy and fusion (ACCF).

It is essential to recognize the possibility of complications, even though most anterior approach procedures are executed with safety and efficacy. Possible complications of anterior approach procedures comprise incisional hematoma, dysphagia, esophageal perforation, injuries to the superior and recurrent laryngeal nerves, spinal cord and nerve root injury, as well as vertebral artery injury.

Due to its proximity to the surgical site, the vertebral artery (VA) is vulnerable to injury during anterior cervical spine surgery. Although iatrogenic vertebral artery injury (VAI) is uncommon, with an incidence rate of 0.18%–0.5%, it can cause significant intra- or postoperative bleeding, cardiac arrest, arteriovenous fistula, neurological complications, or even death.

Various factors that can elevate the risk of VAI have been identified:

1. 1. 1. Coarse Drilling: The most commonly reported cause of VAI is drilling during the surgical procedure. When performing decompression during anterior cervical surgery, coarse drilling can cause excessive lateral movement, particularly when drilling through a vertebra, disc, or foramen. This is especially true in cases where the bone has been softened due to infection or tumor growth.
      2. Loss of Landmarks: In anterior cervical surgery, two significant landmarks are the midline and the uncinate process. The midline serves as a reference point to determine the safe extent of lateral exposure and decompression during the surgical procedure, as well as the precise placement of instrumentation.
         Accurately identifying the midline may be challenging in certain situations, such as when a large, eccentric osteophyte is present. Loss of this landmark can result in excessive lateral drilling, leading to VAI.
         Located medial to the transverse foramen, the uncinate process has a distinct sharp and tapered articular surface that creates an uncovertebral joint. During surgery, the medial uncovertebral joint serves as a boundary for lateral dissection or drilling. As the uncinate process flattens over time, it becomes less effective in preventing VAI.
      3. Status of VA: There are three sections that comprise the extracranial vertebral artery.
         • Section 1 (V1): It arises from the subclavian artery and travels to the transverse foramen of C6.
         • Section 2 (V2): It travels from the transverse foramen of C6 to the transverse foramen of C1.
         • Section 3 (V3): It extends from C1 to the foramen magnum.
         • Intracranial portion of the VA (V4): It travels from the foramen magnum to the basilar artery.

The segments of the VA that are most at risk are the anterior portion of C7, the lateral segments from C3 to C7, and the posterior segments of C2 and C1. The path of V2 is the longest and it travels through a canal that is formed by bone and muscle.

It is also surrounded by an extensive network of veins. As a result, the most common injury during anterior cervical surgeries occurs to V2, since these surgeries are primarily performed in the area between C3 and C7.

There is often a difference in the diameter of the left and right VAs. Approximately 6% to 26% of patients have VAs of the same size, and the left VA is usually larger and considered the dominant vessel.

A significant correlation exists between the diameter of the transverse foramen and VA blood volume. Usually, the side with the larger transverse foramen indicates the dominant VA. The normal course and structure of the VA are usually assumed in most anterior cervical surgery techniques.

Patients with abnormal VAs pose an increased risk of injury during anterior cervical surgery as the traditional landmarks become unusable. Not identifying an anomalous VA can lead to an elevated risk of injury, even if lateral decompression is performed within safe limits that are generally accepted.

Usually, anatomical variations in the VAs are present from birth or associated with degeneration and pathological conditions. Studies investigating anatomical variations of the VAs have reported abnormal entrance levels in approximately 7.0% of cases, and in 1%–2% of cases, the VA formed a medial loop either into an unusually large transverse foramen, whose internal border was medial to the uncovertebral joint, or into the intervertebral foramen.

Patients with degenerative osteoarthritis undergo a process of adaptation in the VA, resulting in the development of a tortuous course and erosion of the posterolateral vertebral bodies. Certain pathological conditions can alter the condition of the VA. The occurrence of VA abnormalities shows a significant difference between rheumatoid arthritis patients and healthy volunteers (34% vs. 2%).

Pre-operative irradiation can lead to scarring of the arterial adventitia, which may result in VA rupture when retracting the surrounding soft tissue during surgery. Infection can lead to erosion and weakening of the artery wall, making it more susceptible to injury.

Identifying anomalies of the VA on plain CT or MRI scans can be challenging. According to the literature, plain CT images are only able to detect about half of VA anomalies.

Misplaced or displaced instruments: Rubbing or abutting of the artery wall can result in VAI, which may manifest as delayed symptoms or an abrupt hemorrhage.

There is currently no agreement on the best approach for managing VAI. In cases of VAI, prompt intervention is necessary to stop bleeding. Hemostasis can be achieved through tamponade using various hemostasis agents, including oxidized cellulose, matrix sealant, microfibrillar collagen, or gelfoam.

The application of tamponade can provide urgent hemostasis, which can be followed by immediate definitive treatment. This treatment may involve artery reconstruction, repair, or stent placement. Alternatively, the artery may be occluded using ligation, clipping, or endovascular coiling. In certain cases, tamponade is used as the primary treatment instead of a temporary measure for achieving hemostasis.

Emergent intubation and volume replacement may be required for neck swelling, dyspnea, and hypotension caused by delayed rupture and pseudoaneurysm hemorrhage.

Achieving restoration of blood flow through direct repair or endovascular stenting can yield excellent outcomes, however, both procedures are considered technically demanding. Additional muscle dissection and partial removal of the anterior transverse foramen rim are required to create sufficient space for direct repair.

This can be a challenging task, especially when the VAI is located on the opposite side of the original surgical approach, which may necessitate an extension of the existing incision or a separate incision. Additionally, obtaining sufficient space for direct repair may require further lateral dissection of muscles and partial removal of the anterior rim of the transverse foramen.

Prompt intraoperative or postoperative angiography may be a reasonable approach after VAI, particularly when the occlusion of the injured VA is a possibility, given that collateral circulation is seldom known beforehand. This can help assess the status of the bilateral VA before definitive treatment.

Performing artery occlusion without prior evaluation of VA status may pose a high risk of ischemic complications to the patient. Techniques such as tamponade, ligation, vascular clips, or endovascular occlusion should be avoided until the status of the VA has been determined through prompt intra-operative or postoperative angiography.

However, a postoperative angiography revealing a normal state of a damaged VA does not eliminate the possibility of a delayed hemorrhage or the formation of a pseudoaneurysm, which may occur days to years later. The postoperative period may be without complications until symptoms associated with pseudoaneurysm arise.

In cases where the injured VA is dominant, it is highly recommended to restore blood flow through repair or endovascular stent placement to minimize the risk of both immediate and delayed ischemic neurological complications. In patients who have sufficient collateralization and perfusion through the ipsilateral posteroinferior cerebral artery, sacrificing the injured VA may be a safe option.

If the VA is occluded through direct ligation or vascular clips, it is recommended to ligate or clip it both proximally and distally to prevent the possibility of delayed complications such as embolic or hemorrhagic issues, or the formation of arteriovenous fistula if only proximal ligation or clipping is performed.

Recent Advances

An alternative to direct exposure and suture repair is the use of endovascular stents, especially in cases of massive bleeding, hemodynamic instability, or lacerations on the posterior or posteromedial walls of the vessel.

Additionally, procedures such as stent-assisted angioplasty, embolization of pseudoaneurysm, and endovascular occlusion using coiling or balloons have been reported to yield favorable outcomes. Having a skilled endovascular team can facilitate the successful completion of these procedures.

Prevention is considered the optimal approach to managing VAI. Thorough evaluation of the cervical spine and VA for abnormalities or pathological alterations pre-operatively is crucial, particularly in patients with conditions such as degeneration, RA, tumors, or infections, to prevent VAI.

Angiography can be utilized to visualize both VAs and any anomalies present for evaluation purposes. If anomalies such as tortuous or dilated arteries that are displaced are detected, it is important to consider dominance. If anomalies are detected prior to surgery, alternative or innovative surgical techniques, or a posterior approach, may be considered.

Real-time image guidance, intraoperative CT, or 3D fluoroscopy-based navigation systems can be helpful during surgery to accurately determine anatomy and assist with decompression and instrument placement, especially when landmarks are not visible. Precise and controlled drilling can minimize the risk of injury compared to using coarse drilling techniques, thereby promoting stability during the procedure.

VAI, which can occur during anterior cervical surgery, is an infrequent yet potentially severe complication. The risk of VAI during anterior cervical surgery is increased by factors such as extensive lateral decompression, loss of landmarks, and anatomical variations or pathologic conditions of the VA. While tamponade can be effective in urgent cases, it is not a recommended definitive treatment due to a high risk of pseudoaneurysm formation.

It is necessary to identify collateralization before treatment and restore blood flow through direct repair or endovascular stenting when the dominant VA is injured. Precise pre-operative assessment and careful intra-operative manipulation with real-time radiographic guidance can also decrease the likelihood of VAI.

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