Vertebral artery pseudoaneurysm complicating posterior C1-2 transarticular screw fixation: case report

Iatrogenic Vascular Injury Associated with Cervical Spine Surgery: A Systematic Literature Review

BACKGROUND

Iatrogenic vascular injury is an uncommon complication of anterior and/or posterior surgical approaches to the cervical spine. Although the results of this injury may be life-threatening, mortality/morbidity can be reduced by an understanding of its mechanism and proper management.

METHODS

We conducted a literature review to provide an update of this devastating complication in spine surgery. A total of 72 articles including 194 cases of vascular lesions following cervical spine surgery between 1962 and 2021 were analyzed.

RESULTS

There were 53 female and 41 male cases (in addition to 100 cases with unreported sex) with ages ranging from 3 to 86 years. The vascular injuries were classified according to the spinal procedures, such as anterior or posterior cervical spine surgery. The interval between the symptom of the vascular injury and the surgical procedure ranged from 0 to 10 years. Only two-thirds of patients underwent intra- or postoperative imaging and the most frequently injured vessel was the vertebral artery (86.60%). Laceration was the most common lesion (41.24%), followed by pseudoaneurysm (16.49%) and dissection (5.67%). Vascular repair was performed in 114 patients. The mortality rate was 7.22%, and 18.04% of patients had 1 or more other complications. Most presumed causes of vascular lesions were by instrumentation/screw placement (31.44%) or drilling (20.61%). Sixteen patients had an anomalous artery. Direct microsurgical repair was achieved in only 15 cases.

CONCLUSIONS

Despite increased anatomical knowledge and advanced imaging techniques, we need to consider the risk of vascular injury as a surgical complication in patients with cervical spine pathologies.

Power-Tool Use in Orthopaedic Surgery: Iatrogenic Injury, Its Detection, and Technological Advances: A Systematic Review

Power tools are an integral part of orthopaedic surgery but have the capacity to cause iatrogenic injury. With this systematic review, we aimed to investigate the prevalence of iatrogenic injury due to the use of power tools in orthopaedic surgery and to discuss the current methods that can be used to reduce injury.

Emergent Vertebral Artery Embolization during C12 Screw Fixation for Rheumatoid Arthritis

The subaxial screw fixation technique is commonly used for fixation in a wide range of cervical diseases, including traumatic, degenerative, and neoplastic diseases, rheumatoid arthritis (RA), and spondyloarthropathy. Although it is regarded as a relatively safe procedure, several complications may be encountered during surgery, such as vertebral artery (VA) and nerve root injuries, facet violation, and mass fracture. We report a case of endovascular embolization after VA injury during a high cervical spinal surgery. A 48-year-old woman was scheduled for C-1-2-3 posterior fixation. Plain radiography of the cervical spine revealed a severely unstable state. During dissection around the C1 lateral mass on the right side, sudden brisk arterial bleeding was observed. On vertebral angiography, flow voiding was noted above the right V3 portion. After checking patent collateral flow from the contralateral VA, routine coil embolization was performed to pack the V3 segment. Iatrogenic vascular injuries due to spinal surgery are rare but serious complications. For patients with RA, we recommend careful preoperative evaluation before a high cervical surgical procedure to avoid iatrogenic VA injury and endovascular interventions that are safe and effective in the diagnosis and treatment of such vascular injuries.

Anomalous Vertebral Artery During Cranio Vertebral Junction Surgery Using DCER (Distraction, Compression, Extension, and Reduction): Approach. and Its Repair

Introduction

Vertebral artery (VA) may run an anomalous course in congenital craniovertebral junction anomalies. Anomalous VA, though rare, is challenging to handle. An anomalous VA can get injured during exposure of craniovertebral junction, even in the experienced hands.

Objective

The objective of this article was to describe the technique of repairing the VA in case of its damage during exposure in the craniovertebral junction (atlantoaxial dislocation [AAD] with basilar invagination [BI]).

Procedure

The authors describe a case of VA artery injury in a case of severe BI & AAD, which was anomalous and coursing over the joints. Following the repair of injured VA, we proceeded with the surgery (distraction, compression, extension, and reduction [DCER]).

Conclusion

To avoid injury, it is important to always perform a CT 3-D angiogram, perform meticulous dissection under the microscope while exposing the joints, use variable impedance bipolar to control venous bleeding and always expose the side with non-dominant VA first.

CT angiographic evaluation of the V3 vertebral artery course in cases of occipitalized atlas, a study of 25 cases

OBJECTIVES

To study the relationship of the 3rd segment of the vertebral artery to the posterior arch of the atlas in patients with occipitalized atlas, using CT angiography.

METHODS

A retrospective study of 25 cases with complete or partially occipitalized atlas who underwent CT angiography evaluation. Fifty vertebral arteries were analyzed in relation to the respective/related half of the posterior arch of the atlas.

RESULTS

Out of 50 vertebral arteries, 35 (70%) were anomalous; 31 (62%) traversed though bony canal between the fused occiput and atlas, and 4 (8%) coursed between C1 and C2 (C2 segmental type of vertebral artery). Except one, all anomalous vertebral arteries were associated with a fused corresponding side of posterior arch of atlas.

CONCLUSION

The V3 portion of the vertebral artery assumes an anomalous course at the craniovertebral junction in most cases of occipitalized atlas, and this is strongly determined by the fusion status of the posterior arch of the atlas. Aberrations in its course are still seen despite expectations based on this fusion status. Preprocedural CT Angiography provides accurate information of its course to prevent iatrogenic VA injuries.

ADVANCES IN KNOWLEDGE

CT Angiography should be performed before any procedures at the craniovertebral junction in cases of occipitalized atlas to prevent iatrogenic, potentially catastrophic injuries to vertebral artery due to its anomalous course in most of these cases. There are very few such studies in the literature, none in radiology literature. We also describe some rare cases, including a case never described in any literature.

Techniques of cervical pedicle screw insertion in lower cervical spine - A review

Cervical pedicle screws (CPS) have been used for stabilization of lower cervical spine since its first description by Abumi et al., in 1994^, but the usage has been limited due to the feared complications. Cadaveric studies have discouraged use of CPS in lower cervical spine due to high misplacement rates. On the contrary, clinical studies have shown limited complications due to screw misplacements and have highlighted the benefits of CPS with its superior biomechanical strength. Therefore surgeons have always tried to find a reliable, reproducible and safe CPS insertion technique to expand the usage of CPS with minimal complications. As of today Abumi et al. technique is the most popular free-hand technique used by surgeons, though many modifications have evolved to make the CPS insertions more safe and reproducible. The free hand technique should be considered as the cornerstone technique for CPS insertion and the navigation tools are essential to improve the safety of CPS in complex surgeries with altered cervical anatomy. The present review brings together the literature on the various aspects of cervical pedicle anatomy, the free-hand screw insertion techniques with their modifications, the screw misplacement rates and complications.

Safe and bloodless exposure of the third segment of the vertebral artery: a step-by-step overview based on over 50 personal cases

Craniovertebral junction surgery usually requires the exposure of the third segment of the vertebral artery (V3). However, the complexity of musculature, a relatively high incidence of anomalies in the course of the vertebral artery (VA), and the presence of a rich venous plexus in this region make the V3 exposure challenging with a high risk of serious complications while taking down the suboccipital muscles in a single layer. A muscle dissection in interfascial layers, however, overcomes the drawbacks inherent in a blind dissection of the V3 as each of the muscles represents substantial landmark aiding subsequent step of the procedure and thus helping identify underlying anatomical structure early and safely. Moreover, along with a bloodless VA dissection off its surrounding venous plexus, it permits a safe and comfortable V3 exposure during the surgically demanding procedures.

Treatment of Odontoid Fractures in the Aging Population

Odontoid fractures are the most common cervical fracture type among the elderly population. Several treatment options exist for these patients, ranging from immobilization with a semirigid orthosis to surgical arthrodesis. This report reviews the key points in the management of odontoid fractures in the aged patient, including diagnosis, the various forms of conservative therapies, and the options for surgical intervention.

Delayed Migration of Fractured K-wire Causing Vertebral Artery Invagination After Anterior Atlantoaxial Fixation: A Case Report

BACKGROUND

Most of the physician's attention during spinal surgery, when using wires and screws, is toward the avoidance of injuries of critical structures (nerves and vessels). When such wires are broken during surgery, the most important point is to take them out safely or, if it is impossible, to leaf them in secure place and follow the patient closely. Migrations of broken Kirschner wire (K-wire) are well known in literature; however, to the best of our knowledge, migration of a fractured K-wire during anterior atlantoaxial fixation of cervical spine has not been reported in the literature.

CASE DESCRIPTION

We report a case in which a fractured K-wire was imbedded in the lateral mass of C1 for 3 years and then migrated to endanger the dominant right vertebral artery. By using posterior approach and drilling right part of posterior arch of C1, we manage to secure the vertebral artery. The broken K-wire was extracted successfully. In our case, with optimal follow-up, the burred wire inside hard bone was moved in delayed fashion to come out of the bone, grooving the dominant vertebral artery.

CONCLUSIONS

Our recommendation is to inspect the K-wire before using it and to try retrieve as much as possible when removing it.

Vertebral artery injury during foraminal decompression in "low-risk" cervical spine surgery: incidence and management

OBJECTIVES

Vertebral artery injury (VAI) during foraminal decompression in cervical spine surgery in the absence of repositioning or screw stabilization is rare. Without immediate recognition and treatment, it may have disastrous consequences. We aimed to describe the incidence and management of iatrogenic VAI in low-risk cervical spine surgery.

MATERIALS AND METHODS

The records of all patients who underwent surgical procedures of the cervical spine between January 2007 and May 2012 were retrospectively consecutively evaluated. Anterior cervical discectomy and fusion or arthroplasty as well as dorsal foraminal decompression through the Frykholm approach in degenerative diseases were defined as low-risk surgeries (n = 992).

RESULTS

VAI occurred in 0.3 % (n = 3) of 992 procedures: in one case during a dorsal foraminal decompression, and in two cases during the anterior cervical discectomy and fusion (ACDF) of two or four levels, respectively. In the first case, the VAI was intraoperatively misdiagnosed. Despite an initially uneventful course, the patient suffered hemorrhage from a pseudoaneurysm of the injured VA 1 month after surgery. The aneurysm was successfully occluded by endovascular coiling. In both ACDF cases, angiography and endovascular stenting of the lacerated segment proceeded immediately after the surgery. All three patients suffered no permanent deterioration.

CONCLUSIONS

In a high-volume surgical center, the incidence of VAI during low-risk cervical spine surgery is extremely low, comprising 0.3 % of all cases. The major risks are delayed sequels of the vessel wall laceration. In cases of VAI, immediate angiographic diagnostics and generous indications for endovascular treatment are obligatory.

Delayed Vertebral Artery Dissection after Posterior Cervical Fusion with Traumatic Cervical Instability: A Case Report

Vascular injury presented immediately after the penetration, but delayed onset of vascular symptom caused by an embolism or vessel dissection after cervical fusion or traumatic event is extremely rare. We present a case of a 56-year-old woman who underwent an operation for cervical fusion for type II Odontoid process fracture. She presented symptoms of seizure with hemiparesis in 6 days after the operation. Multifocal acute infarction due to an embolism from the left VA (V3 segment) dissection was observed without a definite screw breach the transverse foramen. We hereby reported the instructive case report of delayed onset of vertebral artery dissection after posterior cervical fusion with type II odontoid process fracture patient. When a cervical operation performed in the cervical trauma patient, even if no apparent VA injury occurs before and during the operation, the surgeon must take caution not to risk cerebral infarction because of the delayed VA dissection.

Multimodality management of vertebral artery injury sustained during cervical or craniocervical surgery

BACKGROUND

Iatrogenic vertebral artery (VA) injury is a rare but potentially devastating complication associated with cervical and craniocervical surgery.

OBJECTIVE

To retrospectively evaluate treatment modalities and outcomes associated with iatrogenic VA injury.

METHODS

Our institutional surgical database was queried for patients who underwent cervical or craniocervical surgery from January 1997 to August 2012.

RESULTS

During this time period, 8213 patients underwent cervical or craniocervical surgery, and 17 (0.2%) cases of VA injury were identified. Eight (47%) of these injuries occurred during C1-2 instrumentation procedures. Primary microsurgical repair of the VA was performed in 5 patients. Other cases were managed by either surgical or endovascular VA occlusion. Of the 17 patients, 15 underwent immediate angiography, 9 of whom were ultimately treated by the use of endovascular techniques.

CONCLUSION

VA injury is an uncommon complication of cervical and/or skull base surgery. Standardized management recommendations may help reduce complications associated with these rare but potentially devastating injuries.

Risk of vertebral artery injury: comparison between C1-C2 transarticular and C2 pedicle screws

BACKGROUND CONTEXT

To our knowledge, no large series comparing the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw have been published. In addition, no comparative studies have been performed on those with a high-riding vertebral artery and/or a narrow pedicle who are thought to be at higher risk than those with normal anatomy.

PURPOSE

To compare the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw in an overall patient population and subsets of patients with a high-riding vertebral artery and a narrow pedicle using computed tomography (CT) scan images and three-dimensional (3D) screw trajectory software.

STUDY DESIGN

Radiographic analysis using CT scans.

PATIENT SAMPLE

Computed tomography scans of 269 consecutive patients, for a total of 538 potential screw insertion sites for each type of screw.

OUTCOME MEASURES

Cortical perforation into the vertebral artery groove of C2 by a screw.

METHODS

We simulated the placement of 4.0 mm transarticular and pedicle screws using 1-mm-sliced CT scans and 3D screw trajectory software. We then compared the frequency of C2 vertebral artery groove violation by the two different fixation methods. This was done in the overall patient population, in the subset of those with a high-riding vertebral artery (defined as an isthmus height ≤ 5 mm or internal height ≤ 2 mm on sagittal images) and with a narrow pedicle (defined as a pedicle width ≤ 4 mm on axial images).

RESULTS

There were 78 high-riding vertebral arteries (14.5%) and 51 narrow pedicles (9.5%). Most (82%) of the narrow pedicles had a concurrent high-riding vertebral artery, whereas only 54% of the high-riding vertebral arteries had a concurrent narrow pedicle. Overall, 9.5% of transarticular and 8.0% of pedicle screws violated the C2 vertebral artery groove without a significant difference between the two types of screws (p=.17). Among those with a high-riding vertebral artery, vertebral artery groove violation was significantly lower (p=.02) with pedicle (49%) than with transarticular (63%) screws. Among those with a narrow pedicle, vertebral artery groove violation was high in both groups (71% with transarticular and 76% with pedicle screws) but without a significant difference between the two groups (p=.55).

CONCLUSIONS

Overall, neither technique has more inherent anatomic risk of vertebral artery injury. However, in the presence of a high-riding vertebral artery, placement of a pedicle screw is significantly safer than the placement of a transarticular screw. Narrow pedicles, which might be anticipated to lead to higher risk for a pedicle screw than a transarticular screw, did not result in a significant difference because most patients (82%) with narrow pedicles had a concurrent high-riding vertebral artery that also increased the risk with a transarticular screw. Except in case of a high-riding vertebral artery, our results suggest that the surgeon can opt for either technique and expect similar anatomic risks of vertebral artery injury.

Management of operative complications related to occipitocervical instrumentation

BACKGROUND

The continued evolution of instrumentation techniques for fusions at the craniovertebral junction has enabled surgical treatment of a wide range of developmental, neoplastic, traumatic, and degenerative conditions. There has been an increased recognition of the morbidity associated with the complications secondary to occipitocervical instrumentation.

OBJECTIVE

To present representative complications secondary to occipitocervical instrumentation in patients who presented to our institution and to emphasize underlying principles in diagnosis and management of craniovertebral disease conditions through illustrative examples of their presentation, management, and follow-up.

METHODS

Clinical records for patients referred to the senior author (A.H.M.) between 2005 and 2010 for evaluation and management of their symptoms arising as a consequence of surgical intervention by a different primary neurosurgeon were reviewed.

RESULTS

Eight patients were identified with representative complications secondary to occipitocervical instrumentation. These complications included incorrect surgical technique, persistent instability, hardware misplacement with potential for vascular injury, associated neural injury, and secondary complications of wound healing resulting from methyl methacrylate use. Surgical revision was required in 2 patients. The remaining patients improved with removal of the offending hardware and acrylic cement. All patients reported symptom resolution, and dynamic imaging studies on follow-up indicated stable alignment and bony fusion.

CONCLUSION

These cases serve as illustrative examples of the spectrum of neural, vascular, biomechanical, and instrument-related complications associated with occipitocervical arthrodesis. Basic principles of occipitocervical instrumentation that enable safe and successful treatment of craniovertebral junction disease conditions have been highlighted. Potential complications and management strategies are discussed.

Anomalous vertebral arteries in the extra- and intraosseous regions of the craniovertebral junction visualized by 3-dimensional computed tomographic angiography: analysis of 100 consecutive surgical cases and review of the literature

STUDY DESIGN

Consecutive case series and literature review.

OBJECTIVE

To describe the utility of 3-dimensional computed tomographic angiography (3D CTA) for evaluating vertebral artery (VA) anomalies before surgery.

SUMMARY OF BACKGROUND DATA

Recent advances in instrumentation surgery at the craniovertebral junction (CVJ) enable us to perform rigid internal fixation. However, the risk of VA injury as a complication of the surgery has become a major problem. Thus, the importance of preoperative evaluation of the VA course has been emphasized.

METHODS

Cases of 100 consecutive patients who underwent CVJ instrumentation surgery since July 1998 were analyzed. Occipitocervical/thoracic or C1-C2 posterior fusion was performed for atlantoaxial subluxation (AAS) in 59 patients and cervical fixation including C2 was required for middle-to-lower cervical lesions in 41 patients. Twenty-seven patients with AAS had a congenital skeletal anomaly (CSA) at the CVJ including os odontoideum and occipitalization of C1 (AAS-CSA[+] group). Anomalous VAs at the extra- and intraosseous regions were evaluated by 3D CTA.

RESULTS

No neurovascular injury occurred during surgery. Abnormal courses of the VA at the extraosseous region were detected in 10 cases: 2 had fenestration and 8 had a persistent first intersegmental artery. All 10 cases were in the AAS-CSA(+) group. A high-riding VA was detected in 31 cases. Fourteen out of the 31 cases were in the AAS-CSA(+) group, indicating 51.9% of the AAS-CSA(+) group had high-riding VA. In the AAS-CSA(+) group, a C1-C2 transarticular screw and C2 pedicle screw were actually inserted in 58% and 31% of the planned insertions, respectively.

CONCLUSION

The present findings suggest that the frequency of an abnormal VA at the extra- and intraosseous regions is increased when patients have AAS and CSA at the CVJ. Using preoperative 3D CTA, we can precisely identify anomalous VAs and thereby reduce the risk of their intraoperative injury.

The use of intra-operative blood gas analysis in the investigation of suspected iatrogenic vascular injury

BACKGROUND

Iatrogenic injury to the vertebral artery during posterior cervical fusion is a rare and potentially disastrous complication. Differentiating arterial from brisk venous bleeding would be ideal to assist in the intra-operative management. Definitive angiography is typically not feasible during most routine spine surgery.

CASE DESCRIPTION

We describe the case of a patient undergoing an occipitocervical fusion, where brisk bleeding was encountered during dissection of the CB lateral mass. While the dissection was thought to be superficial to critical structures, the nature of the hemorrhage could not be definitely determined by visual inspection by two senior surgeons. The hemorrhage did not readily cease with standard maneuvers such as, the application of various hemostatic agents. Simultaneous blood gas analysis was performed on samples obtained from the patient's radial artery and from the hemorrhage in the operative bed. Comparative analysis concluded that the bleeding encountered in the surgical field was venous in nature.

CONCLUSION

Blood gas analysis can be a useful adjunct in determining the nature of hemorrhage from vascular structures in spine surgery when visual inspection is indeterminate.

Delayed subarachnoid hemorrhage following failed odontoid screw fixation

Iatrogenic vascular injury is a rare but potentially devastating complication of cervical spine instrumentation. The authors report on a patient who developed an anterior spinal artery pseudoaneurysm associated with delayed subarachnoid hemorrhage after undergoing odontoid screw placement 14 months earlier. This 86-year-old man presented with spontaneous subarachnoid hemorrhage (Fisher Grade 4) and full motor strength on neurological examination. Imaging demonstrated pseudarthrosis of the odontoid process, extension of the odontoid screw beyond the posterior cortex of the dens, and a pseudoaneurysm arising from an adjacent branch of the anterior spinal artery. Due to the aneurysm's location and lack of active extravasation, endovascular treatment was not attempted. Posterior C1–2 fusion was performed to treat radiographic and clinical instability of the C1–2 joint. Postoperatively, the patient's motor function remained intact. Almost all cases of vascular injury related to cervical spine instrumentation are recognized at surgery. To the authors' knowledge, this is the first report of delayed vascular injury following an uncomplicated cervical fixation. This case further suggests that the risk of this phenomenon may be elevated in cases of failed fusion.

Seven Years of Experience With C2 Translaminar Screw Fixation: Clinical Series and Review of the Literature

BACKGROUND:

C2 translaminar screws offer biomechanical stability similar to that of other C2 fixation methods but with minimal risk to neural and vascular structures.

OBJECTIVE:

To report our experience with the technique since 2002 and to review the pertinent literature to advance the understanding of C2 translaminar screw fixation.

METHODS:

Fifty-two consecutive adult patients with disorders requiring axis stabilization were treated with C2 translaminar screws by a single surgeon. All patients underwent preoperative computed tomography scans to confirm the feasibility of screw placement. Patients were followed up with serial flexion/extension radiographs and/or computed tomography scans.

RESULTS:

The average age in our series was 58.1 years. One hundred three C2 translaminar screws were placed (average length, 28.9 mm). No vascular or neurological injuries occurred. Of 41 patients with sufficient follow-up (average, 13.3 months) to evaluate fusion, 1 instrumentation failure/pseudoarthrosis was observed. Five patients (average age, 78.7 years) died of complications related to medical comorbidities. In the literature, 169 cases of C2 translaminar fixation have been reported, with a fusion rate of 95.3% and no vertebral artery injuries. In biomechanical studies, C2 translaminar screws perform similarly to C2 pedicle screws and may outperform C2 pars screws in intact spine models. With disrupted atlantoaxial ligaments, constructs with C2 translaminar screws may not resist lateral bending as well as those with other screws, although they have more stability than uninstrumented, intact spines.

CONCLUSION:

This study reports 103 C2 translaminar screws, the largest single-surgeon series to date. C2 translaminar screws are a technically feasible, low-risk option for C2 fixation, with a 97.6% fusion rate in this series.

Posterior C1–2 fusion using a polyaxial screw/rod system for os odontoideum with bilateral persistence of the first intersegmental artery

The authors report the case of a patient with os odontoideum, myelopathy secondary to atlantoaxial instability, and bilaterally persistent first intersegmental artery at the craniovertebral junction. Instead of occipitocervical fusion, C1–2 posterior fusion was performed using a polyaxial screw/rod system. The information obtained from 3D CT angiography studies may highlight the potential risk of vertebral artery injury in advance and reduce the risk of an intraoperative vertebral artery injury. In addition, C-1 lateral mass screw placement may be a safe procedure for cases of atlantoaxial subluxation in which there are persistent C-1 intersegmental arteries.

End-to-End Anastomosis of an Unanticipated Vertebral Artery Injury during C2 Pedicle Screwing

Vertebral artery (VA) injury is a rare and serious complication of cervical spine surgery; this is due to difficulty in controlling hemorrhage, which can result in severe hypotension and cardiac arrest, and uncertain neurologic consequences. The authors report an extremely rare case of a 56-year-old woman who underwent direct surgical repair by end-to-end anatomosis of an unanticipated VA injury during C2 pedicle screwing. Postoperatively, the patient showed no neurological deterioration and computed tomography angiography of the VA demonstrated normal blood flow. Although direct occlusion of an injured VA by surgical ligation or endovascular embolization has been used for management of an unanticipated VA injury during surgery, these methods may be associated with significant morbidity and mortality. However, despite its technical demand, microvascular primary repair can restore normal blood flow and minimizes the risk of immediate or delayed ischemic complications. Here we report an iatrogenic VA injury during C2 pedicle screwing, which was successfully treated by end-to-end anastomosis.

Normal anatomical variations of the V₃ segment of the vertebral artery: surgical implications

OBJECT

The authors undertook this cadaveric and angiographic study to examine the microsurgical anatomy of the V₃ segment of the vertebral artery (VA) and its relationship to osseous landmarks. A detailed knowledge of these variations is important when performing common neurosurgical procedures such as the suboccipital craniotomy and the far-lateral approach and when placing atlantoaxial instrumentation.

METHODS

A total of 30 adult cadaveric specimens (59 sides) were studied using magnification × 3 to × 40 after perfusion of the arteries and veins with colored silicone. Seventy-three vertebral angiograms were also analyzed. The morphological detail of the V₃ segment was described and measured in both the cadavers and angiograms. Transarticular screws were placed into 2 cadavers and the relationship of the trajectory to the V₃ segment was analyzed.

RESULTS

The authors identified 4 sites along the V₃ segment that are anatomically the most likely to be injured during surgical approaches to the craniovertebral junction. In 35% of the cadaveric specimens the vertical portion of V₃ formed a posteriorly oriented loop that could be injured during surgical exposures of the dorsal surface of C-2. The mean distance from the midline to the most posteromedial edge of the loop was 25.6 ± 3.5 mm (range 20-35 mm) on the left side and 30.4 ± 3.8 mm (range 23-36 mm) on the right side. On lateral angiograms, this loop projected posteriorly, with a mean distance of 9.8 ± 3.5 mm (range 0-15.7 mm) on the right side and 11.7 ± 1.2 mm (range 10-13.6 mm) on the left side. The horizontal segment of V₃ can be injured when exposing the lower lateral occipital bone and when the C-1 arch is exposed. The mean distance from the inferior border of the occipital bone to the superior surface of the horizontal segment of V₃ was 6 ± 2.8 mm on the right side and 5.6 ± 2.3 mm on the left. In 12% of cases the authors found no space between the horizontal portion of V₃ and the occipital bone. The medial edge of the horizontal segment of V₃ was located 23 ± 5.5 mm (range 10-30 mm) from the midline on the right side and 24 ± 5.7 mm (range 15-32 mm) on the left side. The transition between the V₂-V₃ segments after exiting the C-2 vertebral foramen is the most likely site of injury when placing C1-2 transarticular screws or C-2 pars screws.

CONCLUSIONS

The normal variation of the V₃ segment of the VA has been described with quantitative measurements. An awareness of the anatomical variations and the relationships to the surrounding bony anatomy will aid in reducing VA injury during suboccipital approaches, exposure of the dorsal surfaces of C-1 and C-2, and when placing atlantoaxial spinal instrumentation.

Unilateral posterior atlantoaxial transarticular screw fixation in patients with atlantoaxial instability : comparison with bilateral method

OBJECTIVE

Bilateral C1-2 transarticular screw fixation (TAF) with interspinous wiring has been the best treatment for atlantoaxial instability (AAI). However, several factors may disturb satisfactory placement of bilateral screws. This study evaluates the usefulness of unilateral TAF when bilateral TAF is not available.

METHODS

Between January 2003 and December 2007, TAF was performed in 54 patients with AAI. Preoperative studies including cervical x-ray, three dimensional computed tomogram, CT angiogram, and magnetic resonance image were checked. The atlanto-dental interval (ADI) was measured in preoperative period, immediate postoperatively, and postoperative 1, 3 and 6 months.

RESULTS

Unilateral TAF was performed in 27 patients (50%). The causes of unilateral TAF were anomalous course of vertebral artery in 20 patients (74%), severe degenerative arthritis in 3 (11%), fracture of C1 in 2, hemangioblastoma in one, and screw malposition in one. The mean ADI in unilateral group was measured as 2.63 mm in immediate postoperatively, 2.61 mm in 1 month, 2.64 mm in 3 months and 2.61 mm in 6 months postoperatively. The mean ADI of bilateral group was also measured as following; 2.76 mm in immediate postoperative, 2.71 mm in 1 month, 2.73 mm in 3 months, 2.73 mm in 6 months postoperatively. Comparison of ADI measurement showed no significant difference in both groups, and moreover fusion rate was 100% in bilateral and 96.3% in unilateral group (p=0.317).

CONCLUSION

Even though bilateral TAF is best option for AAI in biomechanical perspectives, unilateral screw fixation also can be a useful alternative in otherwise dangerous or infeasible cases through bilateral screw placement.

Vertebral artery injury in cervical spine surgery: anatomical considerations, management, and preventive measures

BACKGROUND CONTEXT

Vertebral artery (VA) injury can be a catastrophic iatrogenic complication of cervical spine surgery. Although the incidence is rare, it has serious consequences including fistulas, pseudoaneurysm, cerebral ischemia, and death. It is therefore imperative to be familiar with the anatomy and the instrumentation techniques when performing anterior or posterior cervical spine surgeries.

PURPOSE

To provide a review of VA injury during common anterior and posterior cervical spine procedures with an evaluation of the surgical anatomy, management, and prevention of this injury.

STUDY DESIGN

Comprehensive literature review.

METHODS

A systematic review of Medline for articles related to VA injury in cervical spine surgery was conducted up to and including journal articles published in 2007. The literature was then reviewed and summarized.

RESULTS

Overall, the risk of VA injury during cervical spine surgery is low. In anterior cervical procedures, lateral dissection puts the VA at the most risk, so sound anatomical knowledge and constant reference to the midline are mandatory during dissection. With the development and rise in popularity of posterior cervical stabilization and instrumentation, recognition of the dangers of posterior drilling and insertion of transarticular screws and pedicle screws is important. Anomalous vertebral anatomy increases the risk of injury and preoperative magnetic resonance imaging and/or computed tomography (CT) scans should be carefully reviewed. When the VA is injured, steps should be taken to control local bleeding. Permanent occlusion or ligation should only be attempted if it is known that the contralateral VA is capable of providing adequate collateral circulation. With the advent of endovascular repair, this treatment option can be considered when a VA injury is encountered.

CONCLUSIONS

VA injury during cervical spine surgery is a rare but serious complication. It can be prevented by careful review of preoperative imaging studies, having a sound anatomical knowledge and paying attention to surgical landmarks intraoperatively. When a VA injury occurs, prompt recognition and management are important.

Vertebral artery injury during cervical spine surgery: a survey of more than 5600 operations

STUDY DESIGN

Retrospective survey.

OBJECTIVE

To clarify the present incidence and management of iatrogenic vertebral artery injury (VAI) during cervical spine surgery.

SUMMARY OF BACKGROUND DATA

VAI is a rare complication of cervical spine surgery, but it may be catastrophic. Anterior cervical decompression (ACD) and posterior atlantoaxial transarticular screw fixation (Magerl fixation) have been the main causes, with reported incidences of 0.3% to 0.5% and 0% to 8.2%, respectively. Popular new surgical techniques, such as cervical pedicle screw or C1 lateral mass screw fixation, also entail the potential risk of VAI.

METHODS

A questionnaire was sent to our affiliated hospitals requesting information regarding iatrogenic VAI during cervical spine surgery.

RESULTS

Seven spine surgeon groups and 25 general orthopedist groups responded to the questionnaire, with a response rate of 89%. The overall incidence of VAI was 0.14% (8 cases among 5641 cervical spine surgeries). The incidence in anterior cervical decompression procedures was 0.18% and that in Magerl fixation was 1.3%. Inexperienced surgeons tended to commit VAI more frequently. One case of VAI during C1 lateral mass screw fixation was included, whereas there was no case of VAI caused by cervical pedicle screw fixation. In the case of "VAI in the screw hole," hemostasis was obtained by tamponade or screw insertion, whereas "VAI in the open space" sometimes caused uncontrollable bleeding, in which embolization eventually stopped the bleeding. There were no deaths or apparent neurologic sequelae.

CONCLUSION

The incidence of VAI during cervical spine surgery from this survey was similar to or slightly less than that in the literature. Tamponade was effective in many cases, but prompt consultation with an endovascular team is recommended if the bleeding is uncontrollable. Preoperative careful evaluation of the vertebral artery seems to be most important to prevent iatrogenic VAI and to avoid postoperative neurologic sequelae.

CT analysis of the axis for transarticular screw fixation of rheumatoid atlantoaxial instability

OBJECTIVE

To investigate the morphological characteristics of the axis of rheumatoid arthritis (RA) patients with atlantoaxial instability and to determine, by means of sagittal reconstructed computed tomography (CT), the suitability for atlantoaxial transarticular screw fixation.

DESIGN AND PATIENTS

Twenty-seven patients, who had undergone reconstructed cervical spine CT scanning preoperatively and posterior atlantoaxial arthrodesis for atlantoaxial instability, were identified from a database for inclusion in this study. The isthmus height and internal height of the lateral mass of the axis were measured using digital imaging software.

RESULTS

The mean isthmus height and internal height of the lateral mass of the axis in RA patients (n=14) were significantly lower than in non-RA patients (n=13) (P<0.01). A high-riding vertebral artery (VA) was present in 54% (15 joints, 9 patients) of the 28 atlantoaxial joints in the RA group and in 12% (3 joints, 2 patients) of the 26 atlantoaxial joints in the non-RA group (P<0.01).

CONCLUSIONS

In RA patients, the axis showed more extensive thinning of the isthmus and lateral mass than in non-RA patients. A precise preoperative evaluation of screw trajectory using reconstruction CT imaging may be useful in atlantoaxial transarticular fixation, particularly for RA patients with atlantoaxial instability.

Intraoperative adverse events and related postoperative complications in spine surgery: implications for enhancing patient safety founded on evidence-based protocols

STUDY DESIGN

Prospective observational study.

OBJECTIVE

To assess the incidence and clinical consequence of intraoperative adverse events from a wide variety of spinal surgical procedures.

SUMMARY OF BACKGROUND DATA

In this study, adverse events were defined as any unexpected or undesirable event(s) occurring as a result of spinal surgery. A complication was defined as a disease or disorder, which, as a consequence of a surgical procedure, will negatively affect the outcome of the patient. We hypothesized that most adverse events would not result in complications that would be normally flagged through traditional practice audit approaches. By defining the incidence and types of adverse events seen in a spine surgical practice, we hope to develop preventative approaches to enhance patient safety.

METHODS

All postoperative clinical sequelae (i.e., complications) were prospectively identified, classified as to type, and graded (0 [none] to IV [death]) in 700 consecutive patients who underwent spine surgery (excluding > 300-day surgery microdiscectomies) at a university center from January 2002 to June 2003. To confirm data accuracy and assess the clinical sequelae of any adverse events, the medical records of these 700 patients were reviewed.

RESULTS

The overall incidence of intraoperative adverse events was 14% (98/700). A total of 23 adverse events led to postoperative clinical sequelae for an overall intraoperative complication incidence of 3.2% (23/700). Specific adverse events included dural tears (n = 58), spinal instrumentation-related events (n = 12), blood loss exceeding 5000 mL (n = 10), anesthesia/medical (n = 4), suspected or actual vertebral artery injury (n = 3), approach-related events (n = 3), esophageal/pharyngeal injury (n = 2), and miscellaneous (n = 6).

CONCLUSIONS

Adverse events can frequently occur (14%) during spinal surgery, however, the majority (76.5%) are not associated with complications. Improved patient safety can only be maximized by independent practice audit and the development of prospective methods to record adverse event data so that enhanced, evidence-based, clinical protocols can be developed.

Vascular injury and complication in neurosurgical spine surgery

Vascular injury is an uncommon, but not rare complication of spine surgery. The consequence of vascular injury may be quite devastating, but its incidence can be reduced by understanding the mechanisms of injury. Properly managing vascular injury can reduce mortality and morbidity of patients. A review of the literature was conducted to provide an update on the etiology and management of vascular injury and complication in neurosurgical spine surgery. The vascular injuries were categorized according to each surgical procedure responsible for the injury, i.e., anterior screw fixation of the odontoid fracture, anterior cervical spine surgery, posterior C1-2 arthrodesis, posterior cervical spine surgery, anterolateral approach for thoracolumbar spine fracture, posterior thoracic spine surgery, scoliosis surgery, anterior lumbar interbody fusion (ALIF), lumbar disc arthroplasty, lumbar discectomy, and posterior lumbar spine surgery. The incidence, mechanisms of injury, and reparative measures were discussed for each surgical procedure. Detailed coverage was especially given to vascular injury associated with ALIF, which may have been underestimated. The accumulation of anatomical knowledge and advanced imaging studies has made complex spine surgery safer and more reliable. It is not clear, however, whether the incidence of vascular injury has been reduced significantly in all procedures of spine surgery. Emerging new techniques, such as microendoscopic discectomy and lumbar disc arthroplasty, seem to be promising, but we need to keep in mind their safety issues, including vascular injury and complication.

Anomalous vertebral artery at the extraosseous and intraosseous regions of the craniovertebral junction: analysis by three-dimensional computed tomography angiography

STUDY DESIGN

This study examined the extraosseous and intraosseous anomalies of vertebral arteries in patients who underwent surgery of the craniovertebral junction.

OBJECTIVES

To describe the usefulness of three-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery.

SUMMARY OF BACKGROUND DATA

Previous studies using catheter angiograms have identified anomalous courses of the vertebral artery at the craniovertebral junction. Studies using computed tomography reconstruction also showed deviation of the vertebral artery groove at the C2 isthmus, demonstrating a risk of vertebral artery injury for C1-C2 transarticular screw placement. These analyses provided us with useful information for identifying anomalies of the vertebral artery, but they could not visualize the artery and its circumferential osseous tissue simultaneously, nor could they analyze the reciprocal anatomy of both tissues.

METHODS

Thirty-one consecutive patients who submitted to surgery at the craniovertebral junction were evaluated before surgery by three-dimensional computed tomography angiography. Eleven of the patients had congenital osseous anomalies at the craniovertebral junction including os odontoideum and ossiculum terminale. Anomalous vertebral arteries at the extraosseous region were visualized by three-dimensional reconstruction images, and the intraosseous deviation of the vertebral artery at the C2 isthmus was evaluated by multiplanar reconstruction images.

RESULTS

Extraosseous and/or intraosseous vertebral artery anomalies were detected in 9 cases. Eight of the 9 cases had osseous anomalies at the craniovertebral junction. Abnormal courses of the vertebral artery at the extraosseous region were detected in 4 cases: 2 had fenestration and 2 had persistent first intersegmental artery. Asymmetry of bilateral vertebral arteries was found in 5 cases: the right was dominant in 3 cases and the left in 2 cases. A high-riding vertebral artery at the C2 isthmus was detected in 5 cases. Based on these findings, we modified our surgical approach and the screw placement; consequently, no vertebral artery injury occurred.

CONCLUSIONS

In patients having osseous anomalies at the craniovertebral junction, the frequency of vertebral artery anomalies at the extraosseous and intraosseous regions is increased. With preoperative three-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and reduce the risk of intraoperative injury to the vertebral artery, in advance.

An anatomical study comparing standard fluoroscopy and virtual fluoroscopy for the placement of C1–2 transarticular screws

Object. The authors sought to compare radiation exposure, surgical time, and accuracy of screw placement when using either standard fluoroscopy or virtual fluoroscopy for the placement of C1–2 transarticular screws.

Methods. Twenty-two C1–2 transarticular screws were placed in 11 cadavers in a randomized and alternating order by using either standard fluoroscopy or virtual fluoroscopy (fluoronavigation). The radiation time, procedure time, and accuracy of screw placement were recorded and statistically compared. A small but statistically significant reduction in fluoroscopy time was noted with the virtual fluoroscopy technique but the surgical times were similar between the two techniques. The incidence of noncritical and critical breaches (those at risk of causing a neurovascular injury) was not significantly different between the two groups. Careful analysis of the C1–2 anatomy in these specimens underscored the importance of placing the screw path in a maximally dorsal and medial portion of the C-2 isthmus to avoid injury to the vertebral artery and to maximize the bone purchase of the C-1 lateral mass.

Conclusions. Although virtual fluoroscopy may represent a useful tool for transarticular screw placement, it does not supplant traditional surgical techniques and does not appear to lower the incidence of bone breaches that can occur when performing this demanding procedure.

Spontaneous Pseudoaneurysm of the Vertebral Artery in Behçet's Disease

A pulsatile mass and severe neck pain developed suddenly in a 15-year-old female patient suffering from Behçet's disease. Magnetic resonance imaging showed a pseudoaneurysm at the C3-C4 level that was 51 x 49 x 45 mm in size, originating from the left vertebral artery, with a thin neck and thrombus inside. Repair of the vertebral artery wall by percutaneous transluminal intervention was not successful. Because of the possibility of rupture, the patient underwent surgical repair. Ligation of the left vertebral artery was applied 1 cm above the origin of the subclavian artery. During the subsequent postoperative period, no further complications were seen. From our review of the literature, this is the first reported case of surgical treatment of spontaneous development of a pseudoaneurysm at the vertebral artery in association with Behçet's disease. Ligation of the vertebral artery can be safely used to control a pseudoaneurysm related to Behçet's disease.

Endovascular Treatment of a Vertebral Artery Pseudoaneurysm Following Posterior C1?C2 Transarticular Screw Fixation

We present a case of vertebral artery pseudoaneurysm after a posterior C1-C2 transarticular screw fixation procedure that was effectively treated with endovascular coil occlusion. Vertebral artery pseudoaneurysm complicating posterior C1-C2 transarticular fixation is extremely rare, with only one previous case having been reported previously. Endovascular occlusion is better achieved in the subacute phase of the pseudoaneurysm, when the wall of the pseudoaneurysm has matured and stabilized. Further follow-up angiographies are mandatory in order to confirm that there is no recurrence of the lesion.

Posterior transarticular screw fixation for chronic atlanto-axial instability

Treatment for chronic atlanto-axial instability remains problematic despite recent innovations in new surgical techniques and instrumentation. Our team reviewed a series of 23 cases of patients with chronic atlanto-axial instability who underwent posterior transarticular screw fixation operations between May 1998 and September 2002. Etiologies of these patients included failed prior surgery, rheumatoid arthritis, congenital anomalies and old odontoid fractures. The clinical presentations were nuchal pain and cervical myelopathy or radiculopathy, with sensory and/or motor deficits that persisted for more than 3 months. We routinely used external reduction to realign the C1-C2 axis prior to operating, and operated on patients using halo-vest fixation. After surgery, the halo-vest was replaced by a collar. In the post-operative follow-up, 22 of the 23 patients (96%) were found to have achieved solid, bony or fibrous union of the C1-C2 axis. Eleven of the 14 (79%) patients with pre-operative neck pain experienced immediate relief or significant improvement. Thirteen of the 20 patients (65%) with myelo-radiculopathy demonstrated improvement of previous motor deficits. Major morbidity included a vertebral artery (VA) injury and a malpositioned screw. No cases of mortality or neurological complications occurred in this series. Posterior transarticular C1-C2 screw fixation results in a high fusion rate without the additional need for rigid external immobilization. It allows good neurological recovery in cases of chronic atlanto-axial instability. Judicious pre-surgical planning and meticulous operative technique may avoid neurological complications and vertebral artery injury.

Pseudoaneurysm of the thoracic radiculomedullary artery with subarachnoid hemorrhage

✓ The authors report a rare case of a patient with a left-sided T-5 radiculomedullary artery pseudoaneurysm who presented with spinal subarachnoid hemorrhage (SAH). The patient, a 71-year-old woman, was hospitalized for progressive paraplegia and sensory loss with bladder and rectal dysfunction. Computerized tomography scanning revealed an SAH at the posterior fossa. Spinal T2-weighted magnetic resonance imaging demonstrated SAH and an inhomogeneous and slightly low signal intensity mass at T4–5. Spinal angiography revealed a tiny masslike staining without arteriovenous shunting. The resected specimen, which caused the spinal SAH, was diagnosed as a pseudoaneurysm based on operative and pathological findings.

Acute atlanto-axial post-operative subluxation following posterior C1/2 fusion

Two cases referred with acute post-operative C1/2 subluxation following posterior fusion are reported. Both cases had initial treatment for atlanto-axial instability with posterior cable (Brooks and interspinous) and graft techniques, and placed immediately in a Philadelphia collar. One case was found to have subluxed immediately post-operatively when failing to breathe following reversal of anaesthetic agents, and despite immediate realignment and reoperation was left with a significant quadriparesis. The other patient was noted to have subluxed on routine X-ray on day 4, and had no neurological deficit before or after reoperation. Risk factors for this dangerous complication are discussed and the techniques of C1/2 posterior fusion and stabilization are reviewed in detail. Surgeons performing atlanto-axial stabilization procedures should be familiar with and have expertize in the complete range of techniques described and choose the one most appropriate for the patient's individual requirements.

Anatomic relationship of the internal carotid artery to the C1 vertebra: A case report of cervical reconstruction for chordoma and pilot study to assess the risk of screw fixation of the atlas

STUDY DESIGN

A case of internal carotid artery impingement by the tip of a well-positioned C1-C2 transarticular screw is presented along with a pilot study involving radiologic and anatomic evaluation of human cadaveric specimens.

OBJECTIVE

To raise awareness that the internal carotid artery may be in close proximity to the anterior aspect of the atlas and at risk of injury during placement of C1-C2 transarticular screws or C1 lateral mass screws.

SUMMARY OF BACKGROUND DATA

To our knowledge, no cases of internal carotid artery injury or impingement have been reported with screw fixation of the atlas.

METHODS

A case of internal carotid artery impingement by a C1-C2 transarticular screw is presented. The C1-C2 rotation appeared to place the internal carotid artery in the path of the screw, prompting a pilot study. Three fresh-frozen human cadaveric head and neck specimens were fixed in different degrees of rotation. Thin-section computed tomography of the specimens was obtained in the plane of the atlas. The frozen specimens were sectioned in the same plane as the computed tomography images. Measurements were taken to assess the location of the internal carotid artery relative to the anterior aspect of the atlas.

RESULTS

Cervical rotation does not have a predictable effect on the location of the internal carotid artery. Medial angulation of a screw placed in the lateral mass of C1 appears to increase the margin of safety for the internal carotid artery. The internal carotid artery varies in location and may be within 1 mm of the ideal exit point of a bicortical transarticular screw or a C1 lateral mass screw.

CONCLUSIONS

The internal carotid artery is at risk during bicortical screw fixation of the atlas. We recommend a contrast-enhanced computed tomography to assess the location of the internal carotid artery before screw fixation of the atlas.