The accuracy and safety of image-guidance system using intraoperative fluoroscopic images: an in vitro feasibility study

O-arm navigation versus C-arm guidance for pedicle screw placement in spine surgery: a systematic review and meta-analysis

BACKGROUND

O-arm and C-arm are commonly used in spine surgery to guide pedicle screw placement. However, concerning the accuracy and efficiency of them, no systematical review and meta-analyses are available to help surgeons make comparisons.

PURPOSES

This study aims to investigate the accuracy and efficiency of O-arm-navigated versus C-arm-guided pedicle screw placement in thoracic and lumbar spine surgery. It would help surgeons choose the optimal technique for pedicle screw placement.

PATIENTS AND METHODS

A systematic review and meta-analyses were performed after searching the PubMed, Embase, and Cochrane databases to identify all studies that assessed the accuracy and efficiency of navigation coupled with O-arm and conventional C-arm fluoroscopy.

RESULTS

Eight studies were finally recruited in this systematic review, all of which reported pedicle screw placement outcomes related to accuracy or efficiency in both C-arm and O-arm groups. Five studies showed higher screw insertion accuracy in the O-arm group, while one study showed no significant difference. And the pooled results also indicated that the incidence of screw misplacement in the C-arm groups is higher. Moreover, the pooled results from five studies indicated no significant difference in insertion time between C-arm and O-arm.

CONCLUSIONS

Navigation coupled with O-arm imaging displayed a lower efficiency outcome in pedicle screw placement compared to conventional C-arm fluoroscopy. However, in terms of accuracy, O-arm navigation had significant advantages in accuracy over conventional C-arm fluoroscopy.

Computer-assisted Surgery for Scaphoid Fracture

The computer-assisted surgery (CAS) has significantly improved the accuracy, reliability and outcomes of traumatic, spinal, nerve surgery and many other operations with a less invasive way. The application of CAS for scaphoid fractures remains experimental. The related studies are scanty and most of them are cadaver researches. Some intrinsic defects from the registration procedure, scan and immobilization of limbs may inevitably result in deviations. Some deviations become more obvious with operations of small bones (such as scaphoid) although they are acceptable for spine and other orthopedic surgeries. We reviewed the current literatures on the applications of CAS for scaphoid operation and summarized technical principles, scan and registration methods, immobilization of limbs and their outcomes. On the basis of the data, we analyzed the limitations of this technique and envisioned its future development.

Accuracy of minimally invasive percutaneous thoracolumbar pedicle screws using 2D fluoroscopy: a retrospective review through 3D CT analysis

BACKGROUND

In the literature, there is a large variation in the reported misplacement rates of pedicle screws. The use of minimally invasive surgical techniques is increasing and as such there has only been a small amount of data to look at the misplacement rate of percutaneously inserted thoracic and lumbar pedicle screws.

METHODS

A retrospective analysis of post-operative computed tomography (CT) scans were performed on 108 patients who underwent minimally invasive percutaneously inserted thoracic and lumbar pedicle screws by a single surgeon. Analysis of the screw trajectory using strict guidelines was performed using multiplanar reconstruction CT scan data to determine the accuracy of the pedicle screws.

RESULTS

A total of 614 screws were inserted in vertebral levels T2 to S1. Twenty-five (4.07%) screws were considered misplaced having breached the pedicular cortex. Thoracic pedicle screws had a statistically higher misplacement rate than lumbar pedicle screws (14.67% vs. 2.60% respectively, P<0.001). A single screw required replacement (0.16%) and there were no permanent neurological deficits. The misplacement rates were lower than those reported for open screw placement and equivalent to 3D CT navigated misplacement rates.

CONCLUSIONS

Percutaneously inserted pedicle screws using 2D fluoroscopy offers a safe and accurate option for spinal stabilisation with an extremely low misplacement rate and morbidity. Overall, the low misplacement rates were equivalent and in most cases lower compared to open and computer assisted navigation techniques. However, we would recommend that given a misplacement rate of 14.67% for thoracic pedicle screws that computer assisted navigation may be able to offer further improvements in accuracy.

Comparison of Effective Dose of Radiation During Pedicle Screw Placement Using Intraoperative Computed Tomography Navigation Versus Fluoroscopy in Children With Spinal Deformities

BACKGROUND

We compared the effective dose of radiation associated with pedicle screw placement in posterior spinal fusion in children using intraoperative computed tomography (CT) navigation versus intraoperative fluoroscopy (C-arm).

METHODS

In this review of posterior spinal fusion patients, height, weight, local density function, dose area product, body region, number of views, and part of the body were used to calculate the effective dose to the patient in millisieverts (mSv) in 37 children in whom pedicle screw placement was aided by intraoperative CT versus 44 children in whom pedicle screw placement was aided by C-arm. Both groups had posterior spinal fusions during the same time period by 3 surgeons between November 2012 and August 2013. Calculation of the radiation dose was made by the following method: for the C-arm, and the fluoroscopic/digital acquisitions part of the CT examinations, we estimated the effective dose using the program PCXMC 2.0. For the cross-sectional imaging part of the CT examinations, we used the dose-length product from the radiation dose reports of the CT unit and published dose-length product to effective dose conversion factors. The overall effective dose for the CT group was the total of the cross-sectional imaging dose and the fluoroscopic/digital acquisition imaging dose. An unpaired T test was used to determine significant difference between the C-arm and CT navigation groups.

RESULTS

The average effective dose was 1.48±1.66 mSv for the CT patients and 0.34±0.36 mSv for the C-arm patients. These values for the 2 groups are significantly different (P=0.0012). Obese children had very high mSv values in the CT group.

CONCLUSIONS

Intraoperative CT for navigational instrumentation placement associated with spinal fusion in children results in significantly more radiation to the child than C-arm. Families need to be counseled about radiation exposure associated with intraoperative CT, especially in obese children. Intraoperative CT use should be tailored to placing instrumentation where the benefit is the highest.

LEVEL OF EVIDENCE

Level II.

Intraoperative cone beam-computed tomography with navigation (O-ARM) versus conventional fluoroscopy (C-ARM): a cadaveric study comparing accuracy, efficiency, and safety for spinal instrumentation

STUDY DESIGN

Cadaveric laboratory study.

OBJECTIVE

To compare the accuracy, efficiency, and safety of intraoperative cone beam-computed tomography with navigation (O-ARM) with traditional intraoperative fluoroscopy (C-ARM) for the placement of pedicle screws.

SUMMARY OF BACKGROUND DATA

Radiation exposure remains a concern with traditional methods of intraoperative imaging in spine surgery. The use of O-ARM has been proposed for more accurate and efficient spinal instrumentation. Understanding radiation imparted to patients and surgeons by O-ARM is important for assessing risks and benefits of this technology, especially in light of evolving indications.

METHODS

Four surgeons placed 160 pedicle screws on 8 cadavers without deformity. Eighty pedicle screws were placed using O-ARM and C-ARM each. Instrumentation was placed bilaterally in the thoracic (T1-T6) spine and lumbosacral junction (L5-S1) using a standard open technique, whereas minimally invasive surgery technique was used at the lumbar 3 to 4 (L3-L4) level. A "postoperative" computed tomography (CT) scan was performed on cadavers where instrumentation was done using the C-ARM. An independent musculoskeletal radiologist assessed final images for screw position. Time required to set up and instrumentation was recorded. Dosimeters were placed on multiple aspects of cadavers and surgeons to record radiation exposure.

RESULTS

There were no differences in breach rate between the O-ARM and C-ARM groups (5 vs. 7, χ= 0.63, P = 0.4). The setup time for the O-ARM group was longer than that for the C-ARM group (592 vs. 297 s, P < 0.05). However, the average total time was statistically the same (1629 vs. 1639 s, P = 0.96). Radiation exposure was higher for surgeons in the C-ARM group and cadavers in the O-ARM group. When a "postoperative" CT scan was included in the estimation of the total radiation exposure, there was less of difference between the groups, but still more for the O-ARM group.

CONCLUSION

In cadavers without deformity, O-ARM use results in similar breach rates as C-ARM for the placement of pedicle screws. Time for instrumentation is shorter with the O-ARM, but requires a longer setup time. The O-ARM exposes less radiation to the surgeon, but higher doses to the cadaver.

LEVEL OF EVIDENCE

N/A.

Comparing results of posterior spine fusion in patients with AIS: Are two surgeons better than one?

AIMS

Spinal deformity surgery is one of the most complicated procedures performed in pediatric orthopedics. These surgeries can account for long operative times and blood losses. Finding ways to limit patient morbidity undergoing these procedures may benefit many. We hypothesized that utilizing two fellowship trained pediatric spinal deformity surgeons would lead to decreased operative time and blood loss when compared with single surgeon. We felt very little difference would be found in terms of curve correction.

METHODS

A retrospective review of spinal deformity surgeries performed at two institutions was performed. At one institution, the standard of care was to have two fellowship deformity trained surgeons perform all deformity surgeries simultaneously, while at the second institution posterior spinal fusions performed by individual surgeons were performed. The single surgeon cohort was further divided based on instrumentation type (pedicle screw vs hybrid constructs). Cases for this review were limited to posterior spinal fusions without osteotomies in patients with idiopathic or idiopathic like curves. Cohorts were compared pre-operatively for age at surgery, sex, BMI, largest Cobb angle. Intra-operative comparisons included total EBL, instrumentation type screws vs hybrid, levels fused, and operative time. Comparisons between largest remaining Cobb, EBL/level, time/level, lowest recorded Hb, allogenic transfusion requirements, length of PICU stay, and total length of hospital stay were then made. Pair-wise student t-tests was performed between cohorts with significance defined as a p-value of 0.05 or less.

CONCLUSIONS

Twenty-four patients were found in the (BMP) cohort, where as eighty-two were found in the control group. No significant difference in age, sex, starting hemoglobin, BMI*, or maximum pre-operative Cobb between cohorts was found. A significantly lower number of levels were fused in the BMP cohort than the control (9 ± 2 vs 11 ± 2) p < 0.001, and likewise a significantly shorter operative time (average >2 h) was seen in the BMP cohort. Interestingly, no difference in estimated blood loss, blood loss/level fused, operative time/level fused was observed, yet a significantly greater drop in hemoglobin (average 1 g) p = 0.001 and allogenic transfusion rate was seen in the control group (4% (1/24) vs 29% (24/82)) p = 0.01. A greater improvement in Cobb angle was seen in the BMP group 46 ± 8 vs 35 ± 10° p < 0.001. No differences were seen in nights in the PICU and peri-operative complications, however patients in the BMP averaged nearly 1day less in the hospital than in the control group. Utilizing a blood management program including two surgeons in spinal deformity surgery appears to decrease operative time, blood loss, and improve curve correction. Confounding factors such as differences in number of fusion levels, curve types, instrumentation type, and institutional practices prevents drawing definitive conclusions. This is the first study to show potential benefits of utilizing a blood management program with dual surgeons in spinal deformity cases.

Randomized clinical study to compare the accuracy of navigated and non-navigated thoracic pedicle screws in deformity correction surgeries

STUDY DESIGN

Randomized clinical trial (level I evidence).

OBJECTIVE

To compare the accuracy of non-navigation and Iso-C based navigation in pedicle screw fixation in thoracic spine deformities.

SUMMARY OF BACKGROUND DATA

Thoracic pedicle screw insertion for spinal deformity correction can be associated with increased pedicle breaches. Iso-C based navigation has been reported to improve the accuracy of pedicle screw placement, but its use in the presence of deformity has not been reported.

METHODS

Twenty-seven patients with scoliosis and 6 patients with kyphosis had a total of 478 thoracic pedicle screws. The average Cobb angle was 58.4 degrees +/- 8 degrees (range 50 degrees -80 degrees), and the mean kyphotic angle was 54.6 degrees +/- 4 degrees (range 51 degrees -76 degrees). By random allocation, 17 patients had screw insertion under navigation (242 screws) and 16 under fluoroscopic control (236 screws). The 2 groups were compared for accuracy of screw placement, time for screw insertion, and the number of times the C-arm had to be brought into the field. Two independent blinded observers determined accuracy using postoperative computed tomography assessments.

RESULTS

There were 54 (23%) pedicle breaches in the non-navigation group as compared to only 5 (2%) in the navigation group (P < 0.001). Thirty-eight screws (16%) in the non-navigation group had penetrated the anterior or lateral cortex compared to 2 screws (0.8%) in the navigation group. Average screw insertion time in the non-navigation group was 4.61 +/- 1.05 minutes (range 1.8-6.5) compared to 2.37 +/- 0.72 minutes (range 1.16-4.5) in navigation group (P < 0.01). The C-arm had to be moved into the operation field on an average of 1.5 +/- 0.25 times (range 1-3) per screw. With single screening data, an average of 11.4 pedicles (range 9-14) could be visualized without necessity to bring the C-arm into operating field again.

CONCLUSIONS

Iso-C navigation increases accuracy, and reduces surgical time and radiation in thoracic deformity correction surgeries.

Radiation exposure during pedicle screw placement in adolescent idiopathic scoliosis: is fluoroscopy safe?

STUDY DESIGN

With institutional review board approval, prospective data were collected during fluoroscopically guided pedicle screw placement.

OBJECTIVE

To estimate a surgeon's radiation exposure with all screw constructs during surgery to repair idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

To our knowledge, there is no established consensus regarding the safety of radiation exposure during fluoroscopically guided procedures.

METHODS

A surgeon was outfitted intraoperatively with a thermoluminescent dosimeter to estimate radiation exposure to his whole body and thyroid gland.

RESULTS

The index surgeon is projected to receive 13.49 mSv of whole body ionizing radiation and 4.31 mSv of thyroid gland irradiation annually. The National Council on Radiation Protection's current recommendations set lifetime dose equivalent limits for classified workers (radiologists) at 10 mSv per year of life and at 3 mSv for nonclassified workers (spinal surgeons). At the levels estimated, a surgeon beginning his/her career at age 30 years would exceed the lifetime limit for nonclassified workers in less than 10 years. The National Council on Radiation Protection limits the single-year maximum safe dosage to the thyroid to 500 mSv; the yearly exposure estimated here is significantly less.

CONCLUSIONS

The spinal surgeon's intraoperative radiation exposure may be unacceptable. Spinal surgeons should be considered classified workers and monitored accordingly. Methods to lower radiation dosage seem strongly indicated.

Standard multiplanar fluoroscopy versus a fluoroscopically based navigation system for the percutaneous insertion of iliosacral screws: a cadaver model

OBJECTIVES

To compare the safety and efficiency of standard multiplanar fluoroscopy (StdFluoro) and virtual fluoroscopy (VirtualFluoro) for use in the percutaneous insertion of iliosacral screws.

DESIGN

: Human cadaver study comparing 2 imaging modalities during iliosacral screw insertion; imaging randomized from side to side.

SETTING

Bioskills laboratory in a medical school.

PARTICIPANTS

Twenty-nine embalmed whole human cadavers without prior hip or pelvic surgery.

INTERVENTION

Iliosacral screws were inserted into the S1 bodies using a percutaneous insertion technique. Screws were inserted on one side using StdFluoro, and on the other side, screws were placed using VirtualFluoro.

MAIN OUTCOME MEASUREMENTS

Time necessary for imaging preparation, screw insertion, and actual fluoroscopy were recorded. Accuracy and safety of screw placement was assessed using computed tomography and an anatomic dissection of the pelvis.

RESULTS

: Fifty-six of 58 iliosacral screws were placed within the desired bony corridor of the posterior pelvis. One screw placed using each method was inserted erroneously, but both were relatively minor deviations. There were no obvious injuries to major vessels or nerve roots. The total surgical time required for preparation of imaging and screw insertion averaged 7.3 minutes using StdFluoro and 6.7 minutes using VirtualFluoro (P = 0.4). Although the time necessary for screw insertion using VirtualFluoro averaged only 3.5 minutes, compared to 7.0 minutes for StdFluoro (P < 0.05), this time savings was offset by that required for application and calibration of tracking devices when using VirtualFluoro. The average fluoroscopy time using StdFluoro method was 26 seconds, whereas that for the VirtualFluoro was only 6 seconds (P < 0.01).

CONCLUSIONS

Most of the percutaneous iliosacral screws were safely inserted using StdFluoro and VirtualFluoro, and total surgical times were similar using both methods. As VirtualFluoro continues to evolve, improved efficiency in operative times may be expected. Currently, the most beneficial aspect of using VirtualFluoro during the insertion of percutaneous iliosacral screws appears to be significantly decreased use of fluoroscopy when compared to StdFluoro.