Image-guided transarticular atlanto-axial screw fixation

Potential intraoperative factors of screw-related complications following posterior transarticular C1-C2 fixation: a systematic review and meta-analysis

PURPOSE

This study aimed to evaluate the impact of several factors, including patients' intraoperative position, intraoperative visualization technique, fixation method, and type of screws and their parameters, on the frequency of intraoperative screw-associated complications in posterior transarticular C1-C2 fixation.

METHODS

A systematic review of the PubMed database between January 1986 and March 2018 was performed. The key inclusion criteria comprised detailed descriptions of the surgical technique and post-operative screw-associated complications.

RESULTS

The initial search resulted in 1041 abstracts, and a total of 54 abstracts were included in the present study. The overall number of operated patients was 2306. In this group, 4439 screws were inserted. The rate of screw-associated complications during the different time periods was estimated upon meta-analysis. Statistical analysis of the screw malposition rate, vertebral artery injury rate, screw breakage rate based on patients' intraoperative position, intraoperative visualization technique, fixation method, and type of implants and their parameters was also performed.

CONCLUSIONS

The factors that help reduce the rate of screw-associated complications include the intraoperative application of biplanar fluoroscopy or neuronavigation system, the use of 4 mm or thicker lag screws, and screw insertion through contraincisions using cannulated ported instruments. On the other hand, the potential risk factors of screw-associated complications include inadequate intraoperative head fixation using skeletal traction, uniplanar fluoroscopy-guided screw insertion, screw insertion using the posterior midline approach, and the use of 3.5 mm or thinner full-threaded screws. These slides can be retrieved under Electronic Supplementary Material.

Clinically relevant complications related to posterior atlanto-axial fixation in atlanto-axial instability and their management

BACKGROUND

The Magerl transarticular technique and the Harms-Goel C1 lateral mass-C2 isthmic screw technique are the two most commonly used surgical procedures to achieve fusion at C1-C2 level for atlanto-axial instability. Despite recent technological advances with an increased safety, several complications may still occur, including vascular lesions, neurological injuries, pain at the harvested bone graft site, infections, and metallic device failure.

METHODS

We retrospectively analyzed all patients (n=42 cases) undergoing a Harms-Goel C1-C2 fixation surgery with polyaxial C1 lateral mass screws and C2 isthmic screws at two different institutions between 2003 and 2012 and report clinical and radiological complications. One patient was lost to follow-up. The mean follow-up of the remaining 41 patients was 18.7 months (range 12-90). A clinically relevant complication was defined as a complication determining the onset of a new neurological deficit or requiring the need for a revision surgery.

RESULTS

A total of 14 complications occurred in 10 patients (24.4% of 41 patients). Greater occipital nerve neuralgia was evident in 4 patients (9.8%). All but one completely resolved at the end of the follow-up. Persistent neck pain was reported by 3 patients (7.3%), hypoesthesia by 1 patient (2.4%), and anesthesia in the C2 area on both sides in 1 patient (2.4%). Furthermore, a superficial, a deep, and a combined superficial and deep wound infection occurred in 1 patient each (2.4%). One patient (2.4%) had pain at the iliac bone graft donor site for several weeks with spontaneous resolution. A posterior progressive intestinal herniation through the iliac scar was seen in 1 case (2.4%), which required surgical repair. No vascular damages occurred. Altogether, 5/41 patients (12.2%) had a clinically relevant complication including 4 patients necessitating a revision surgery at the C1-C2 level (9.8%).

CONCLUSIONS

Atlanto-axial fixation surgery remains a challenging procedure because of the proximity of important neurovascular structures. Nevertheless, on the basis of our current experience, the C1 lateral mass-C2 isthmic screw technique appears to be safe with a low incidence of clinically relevant complications. Postoperative C2 neuralgia, as the most frequent problem, is due to surgical manipulation during preparation of the C1 screw entry point.

Radiation exposure to the surgeon and the patient during posterior lumbar spinal instrumentation: a prospective randomized comparison of navigated versus non-navigated freehand techniques

STUDY DESIGN

A prospective randomized study.

OBJECTIVE

To compare occupational radiation exposure to the surgeon, as well as the patient, during posterior lumbar spine instrumentation in 10 navigated cases (navigated) versus 11 cases using the freehand technique (non-navigated).

SUMMARY OF BACKGROUND DATA

The use of navigation increases the accuracy of posterior lumbar instrumentation.A further speculated benefit of navigation is the reduction of radiation exposure of the surgeon. However, this has so far not been evaluated in such comparative manner.

METHODS

Radiation exposure to the surgeon was measured by digital dosimeters placed at the level of the eye, chest, and dominant forearm. Radiation exposure was measured from the time of positioning of the patient to the end of the procedure both for navigated (intraoperative 3-dimensional [3D] fluoroscopy-based) and non-navigated (2-dimensional fluoroscopy-guided) freehand posterior lumbar spine instrumentations. A 3D fluoroscopic scan was routinely performed at the end of the procedure for all patients.

RESULTS

Patients were distributed evenly in the 2 groups in terms of sex, age, body mass index, and the number of operated levels. The accumulated radiation dose for the surgeon was significantly higher in the non-navigated group; up to 9.96 times. The radiation dose for the patient was higher with the freehand technique, 1884.8 cGy·cm (non-navigated) versus 887 cGy·cm (navigated), without reaching a statistically significant level.

CONCLUSION

Radiation exposure to the surgeon during pedicle screw placement with the freehand technique is up to 9.96 times greater than with the use of navigation. In the latter group, the only radiation exposure comes from the preoperative-level control and positioning of the 3D C-arm before 3D fluoroscopic acquisition. Furthermore, neuronavigation also reduces the cumulative dose for the patient.

LEVEL OF EVIDENCE

2.

Navigation, robotics, and intraoperative imaging in spinal surgery

Spinal navigation is a technique gaining increasing popularity. Different approaches as CT-based or intraoperative imaging-based navigation are available, requiring different methods of patient registration, bearing certain advantages and disadvantages. So far, a large number of studies assessed the accuracy of pedicle screw implantation in the cervical, thoracic, and lumbar spine, elucidating the advantages of image guidance. However, a clear proof of patient benefit is missing, so far. Spinal navigation is closely related to intraoperative 3D imaging providing an imaging dataset for navigational use and the opportunity for immediate intraoperative assessment of final screw position giving the option of immediate screw revision if necessary. Thus, postoperative imaging and a potential revision surgery for screw correction become dispensable.Different concept of spinal robotics as the DaVinci system and SpineAssist are under investigation.

Atlantoaxial fusion with transarticular screws: meta-analysis and review of the literature

OBJECTIVE

To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with transarticular screw (TAS) fixation.

METHODS

Online databases were searched for English-language articles published between 1986 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 TAS fixation. There were 45 studies including 2073 patients treated with TAS that fulfilled inclusion criteria. Meta-analysis techniques were used to calculate outcomes.

RESULTS

All studies provided class III evidence. The 30-day perioperative mortality rate was 0.8%, and the incidence of neurologic injury was 0.2%. The incidence of clinically significant malpositioned screws was 7.1% (confidence interval [CI], 5.7%-8.8%), the incidence of vertebral artery injury was 3.1% (CI, 2.3%-4.3%), and the rate of fusion with the TAS technique was 94.6% (CI, 92.6%-96.1%).

CONCLUSIONS

TAS fixation is a safe and effective treatment option for C1-2 instability with high rates of fusion (approximately 95%). Screw malposition and vertebral artery injury occurred in approximately 5% of patients. The successful insertion of TAS requires a thorough knowledge of atlantoaxial anatomy.

Image-guided placement of occipitocervical instrumentation using a reference arc attached to the headholder

OBJECTIVE

To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder.

METHODS

The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach.

RESULTS

No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred.

CONCLUSIONS

This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

Image-guided spine surgery: state of the art and future directions

Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers. The issue of where and when navigation technology should be used is still an issue of debate. It is the aim of this study to give an overview on the current knowledge concerning the technical capabilities of image-guided approaches and to discuss possible future directions of research and implementation of this technique. Based on a Medline search total of 1,462 publications published until October 2008 were retrieved. The abstracts were scanned manually for relevance to the topics of navigated spine surgery in the cervical spine, the thoracic spine, the lumbar spine, as well as ventral spine surgery, radiation exposure, tumor surgery and cost-effectivity in navigated spine surgery. Papers not contributing to these subjects were deleted resulting in 276 papers that were included in the analysis. Image-guided approaches have been investigated and partially implemented into clinical routine in virtually any field of spine surgery. However, the data available is mostly limited to small clinical series, case reports or retrospective studies. Only two RCTs and one metaanalysis have been retrieved. Concerning the most popular application of image-guided approaches, pedicle screw insertion, the evidence of clinical benefit in the most critical areas, e.g. the thoracic spine, is still lacking. In many other areas of spine surgery, e.g. ventral spine surgery or tumor surgery, image-guided approaches are still in an experimental stage. The technical development of image-guided techniques has reached a high level as the accuracies that can be achieved technically meet the anatomical demands. However, there is evidence that the interaction between the surgeon ('human factor') and the navigation system is a source of inaccuracy. It is concluded that more effort needs to be spend to understand this interaction.

Relationship of the internal carotid artery to the anterior aspect of the C1 vertebra: implications for C1-C2 transarticular and C1 lateral mass fixation

STUDY DESIGN

Anatomic study of the internal carotid artery (ICA) location with respect to C1 based on computed tomography (CT) scans with contrast medium.

OBJECTIVE

To measure the location of the ICA relative to the anterior aspect of C1 to assess the risk of placing C1-C2 transarticular or C1 lateral mass screws.

SUMMARY OF BACKGROUND DATA

Vertebral artery injury is a known risk from placement of screws in C1. A previous case report revealed an ideally placed C1-C2 transarticular screw abutting and narrowing the ICA. The risk of ICA injury from C1 screws is unknown.

METHODS

Fifty random head and neck CT scans with contrast medium were retrospectively analyzed. Measurements were taken bilaterally including the closest distance from the ICA lumen to C1 and the distance from the medial edge of the ICA to a line drawn along the medial border of the foramen transversarium. The risk of inserting bicortical C1-C2 transarticular and C1 lateral mass screws was estimated based on these measurements.

RESULTS

The mean distance from the ICA to C1 was 2.88 mm on the left and 2.89 mm on the right. The ICA lumen was medial to the foramen transversarium in 42 (84%) of 50 cases (mean: 2.78 mm on the left and 3.00 mm on the right). The proximity of the ICA to C1 posed moderate risk in 46% of cases and high risk in 12% (on at least one side).

CONCLUSION

Because of the risk of ICA injury from a drill bit or the tip of a bicortical screw, we recommend preoperative CT scan with contrast medium in all cases in which a screw is to be placed into C1. If the ICA is in close proximity to the anterior border of C1, unicortical fixation or a different fusion technique should be considered.