The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

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A review of indocyanine green fluorescent imaging in surgery

The field of biomedical optics has matured rapidly over the last decade and is poised to make a significant impact on patient care. In particular, wide-field (typically > 5 cm), planar, near-infrared (NIR) fluorescence imaging has the potential to revolutionize human surgery by providing real-time image guidance to surgeons for tissue that needs to be resected, such as tumors, and tissue that needs to be avoided, such as blood vessels and nerves. However, to become a clinical reality, optimized imaging systems and NIR fluorescent contrast agents will be needed. In this review, we introduce the principles of NIR fluorescence imaging, analyze existing NIR fluorescence imaging systems, and discuss the key parameters that guide contrast agent development. We also introduce the complexities surrounding clinical translation using our experience with the Fluorescence-Assisted Resection and Exploration (FLARE™) imaging system as an example. Finally, we introduce state-of-the-art optical imaging techniques that might someday improve image-guided surgery even further.

https://journals.sagepub.com/doi/pdf/10.2310/7290.2010.00034

Image-Guided Surgery Using Invisible Near-Infrared Light: Fundamentals of Clinical Translation:

Object Several retrospective studies have demonstrated higher accuracy rates and increased safety for navigated pedicle screw placement than for free-hand techniques; however, the accuracy differences between navigation systems has not been extensively studied. In some instances, 3D fluoroscopic navigation methods have been reported to not be more accurate than 2D navigation methods for pedicle screw placement. The authors of this study endeavored to identify if 3D fluoroscopic navigation methods resulted in a higher placement accuracy of pedicle screws. Methods A systematic analysis was conducted to examine pedicle screw insertion accuracy based on the use of 2D, 3D, and conventional fluoroscopic image guidance systems. A PubMed and MEDLINE database search was conducted to review the published literature that focused on the accuracy of pedicle screw placement using intraoperative, real-time fluoroscopic image guidance in spine fusion surgeries. The pedicle screw accuracy rates were segregated according t...

The accuracy of pedicle screw placement using intraoperative image guidance systems.

STUDY DESIGN The insertional torque of pedicle screws using the cortical bone trajectory (CBT) was measured in vivo. OBJECTIVE To investigate the effectiveness of the CBT technique by measurement of the insertional torque. SUMMARY OF BACKGROUND DATA The CBT follows a mediolateral and caudocephalad directed path, engaging with cortical bone maximally from the pedicle to the vertebral body. Some biomechanical studies have demonstrated favorable characteristics of the CBT technique in cadaveric lumbar spine. However, no in vivo study has been reported on the mechanical behavior of this new trajectory. METHODS The insertional torque of pedicle screws using CBT and traditional techniques were measured intraoperatively in 48 consecutive patients. A total of 162 screws using the CBT technique and 36 screws using the traditional technique were compared. In 8 of 48 patients, the side-by-side comparison of 2 different insertional techniques for each vertebra were performed, which formed the H group. In addition, the insertional torque was correlated with bone mineral density. RESULTS The mean maximum insertional torque of CBT screws and traditional screws were 2.49 ± 0.99 Nm and 1.24 ± 0.54 Nm, respectively. The CBT screws showed 2.01 times higher torque and the difference was significant between the 2 techniques (P < 0.01). In the H group, the insertional torque were 2.71 ± 1.36 Nm in the CBT screws and 1.58 ± 0.44 Nm in the traditional screws. The CBT screws demonstrated 1.71 times higher torque and statistical significance was achieved (P < 0.01). Positive linear correlations between maximum insertional torque and bone mineral density were found in both technique, the correlation coefficient of traditional screws (r = 0.63, P < 0.01) was higher than that of the CBT screws (r = 0.59, P < 0.01). CONCLUSION The insertional torque using the CBT technique is about 1.7 times higher than the traditional technique. LEVEL OF EVIDENCE 2.

In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique.

Study design Systematic review of published prevalence of adjacent segment degeneration (ASD) after spine surgery. Objective To evaluate the prevalence of ASD in patients after cervical and lumbar spine surgery. Summary of background data ASD is a common complication after spine surgery in long-term follow-up. A large body of literature has been reported on the topic, but no meta-analysis of the epidemiological data on ASD has been published Methods We searched the MEDLINE until March 2012 published in English language that reported the prevalence of ASD after spine surgery. We determined the ASD rates by calculating proportions and 95% confidence interval (CI) for each study and then pooled the data to derive a pooled proportion and 95% CI. Results A total of 94 studies with 34,716 patients from 19 countries were included. The occurrence of radiograph ASD ranged from 4.8% to 92.2%, and the pooled prevalence was 29.3% (95% CI, 22.7%-35.8%) by the random-effects model. The occurrence of symptoms ASD ranged from 0.0% to 30.3%, and the pooled prevalence was 7.4% (95% CI, 6.4%-8.5%). In cervical position, the occurrence of radiograph ASD and symptoms ASD was 32.8% (95% CI, 17.8%-47.9%) and 6.3% (95% CI, 4.8%-7.8%); in lumbar position, the occurrence of radiograph ASD and symptoms ASD was 26.6% (95% CI, 21.3%-31.9%) and 8.5% (95% CI, 6.4%-10.7%). In the 0.5- to 2- or less, more than 2- to 5- or less, and more than 5- to 20- or less year diagnosis time, the radiograph ASD prevalence was 21.8% (16.0%-27.6%), 33.6% (21.8%-45.4%), and 37.4% (10.7%-64.1%), respectively; and the symptoms ASD prevalence was 6.5% (4.8%-8.1%), 12.1% (8.2%-16.0%), and 3.2% (2.5%-4.0%), respectively. Conclusion Spine surgery is associated with significant risk of ASD. These figures may be useful in the estimation of the burden of the ASD after spine surgery.

Prevalence of Adjacent Segment Degeneration after Spine Surgery: A Systematic Review and Meta-analysis.

Study design Seven different combinations of posterior screw fixation, with or without interbody support, were compared in vitro using nondestructive flexibility tests. Objective To study the biomechanical behavior of a new cortical screw (CS) fixation construct relative to the traditional pedicle screw (PS) construct. Summary of background data The CS is an alternative to the PS for posterior fixation of the lumbar spine. The CS trajectory is more sagittally and cranially oriented than the PS, being anchored in the pars interarticularis. Like PS fixation, CS fixation uses interconnecting rods fastened with top-locking connectors. Stability after bilateral CS fixation was compared with stability after bilateral PS fixation in the setting of intact disc and with direct lateral interbody fixation (DLIF) or transforaminal lateral interbody fixation (TLIF) support. Methods Standard nondestructive flexibility tests were performed in cadaveric lumbar specimens, allowing non-paired comparisons of specific conditions from 28 specimens (4 groups of 7) within a larger experiment of multiple hardware configurations. Condition tested and group from which results originated were as follows: (1) intact (all groups); (2) with L3-L4 bilateral PS-rods (group 1); (3) with bilateral CS-rods (group 2); (4) with DLIF (group 3); (5) with DLIF + CS-rods (group 4); (6) with DLIF + PS-rods (group 3); (7) with TLIF + CS-rods (group 2), and (8) with TLIF + PS-rods (group 2). To assess spinal stability, the mean range of motion, lax zone, and stiff zone at L3-L4 were compared during flexion-extension, lateral bending, and axial rotation. Results With intact disc, stability was equivalent after PS-rod and CS-rod fixation, except that PS-rod fixation was stiffer during axial rotation. With DLIF support, there was no significant difference in stability between PS-rod and CS-rod fixation. With TLIF support, PS-rod fixation was stiffer than CS-rod fixation during lateral bending. Conclusion Bilateral CS-rod fixation provided about the same stability in cadaveric specimens as PS-rod fixation regardless of the presence of interbody, TLIF, or DLIF support.

Biomechanics of Lumbar Cortical Screw-Rod Fixation Versus Pedicle Screw-Rod Fixation With and Without Interbody Support

Object Postsurgical pneumocephalus is an unavoidable sequela of craniotomy. Sufficiently large volumes of intracranial air can cause headaches, lethargy, and neurological deficits. Supplemental O2 to increase the rate of absorption of intracranial air is a common but unsubstantiated neurosurgical practice. To the authors' knowledge, this is the first prospective study to examine the efficacy of this therapy and its effect on the rate of pneumocephalus absorption. Methods Thirteen patients with postoperative pneumocephalus that was estimated to be ≥ 30 ml were alternately assigned to breathe 100% O2 using a nonrebreather mask (treatment group) or to breathe room air (control group) for 24 hours. Head computed tomography (CT) scans without contrast enhancement were obtained at the beginning and end of treatment or control therapy. A neuroradiologist blinded to the type of treatment used software to calculate the 3D volume of the pneumocephalus from the CT scans. The percentage of pneumocephalus absorption w...

Normobaric oxygen therapy strategies in the treatment of postcraniotomy pneumocephalus.

BACKGROUND: Intramedullary spinal ependymomas are rare tumors. OBJECTIVE: To provide a large retrospective review in the modern neuroimaging era from a tertiary center where aggressive surgical resection is favored. METHODS: Charts of intramedullary spinal ependymomas treated between 1983 and 2006 were reviewed. RESULTS: Sixty-seven cases were reviewed. The mean age was 45.6 years (range, 11-78 years) with a male-to-female ratio of 2:1. The most common location was the cervical spine, followed by the thoracic and lumbar spine. The average duration of symptoms was 33 months, with the most common symptom being pain and/or dysesthesias, followed by weakness, numbness, and urinary or sexual symptoms. Gross total resection was achieved in 55 patients and a subtotal resection was performed in 12 patients; 9 patients were treated with adjuvant radiation therapy. Mean follow-up was 32 months. The mean McCormick neurological grade at last follow-up was 2.0. The preoperative outcome correlated significantly with postoperative outcome (P , .001). A significant number of patients who initially worsened improved at their 3-month follow-up examination. Outcomes were significantly worse in patients undergoing subtotal resection with or without radiation therapy (P , .05). There were 3 recurrences. The overall complication rate was 34%. The primary complications were wound infections or cerebrospinal fluid leaks. CONCLUSION: Spinal cord ependymomas are difficult lesions to treat. Aggressive surgical resection is associated with a high overall complication rate. However, when gross total resection can be achieved, overall outcomes are excellent and the recurrence rate is low.

Surgical technique and outcomes in the treatment of spinal cord ependymomas, part 1: intramedullary ependymomas.

Object The authors present outcomes obtained in patients who underwent Gamma Knife surgery (GKS) at 1 institution as part of a multimodal treatment of refractory epilepsy caused by hypothalamic hamartomas (HHs). Methods Between 2003 and 2010, 19 patients with HH underwent GKS. Eight patients had follow-up for less than 1 year, and 1 patient was lost to follow-up. The 10 remaining patients (mean age 15.1 years, range 5.7–29.3 years) had a mean follow-up of 43 months (range 18–81 months) and are the focus of this report. Five patients had undergone a total of 6 prior surgeries: 1 transcallosal resection of the HH, 2 endoscopic transventricular resections of the HH, 2 temporal lobectomies, and 1 arachnoid cyst evacuation. In an institutional review board–approved study, postoperative complications and long-term outcome measures were monitored prospectively with the use of a proprietary database. Seven patients harbored Delalande Type II lesions; the remainder harbored Type III or IV lesions. Seizure frequenc...

Gamma Knife surgery for hypothalamic hamartomas and epilepsy: patient selection and outcomes.

OBJECTIVE: This is the largest contemporary series of distal posterior cerebral artery (PCA) aneurysms treated by use of endovascular coiling and stenting as well as surgical clipping, clip wrapping, and bypass techniques. We propose a new treatment paradigm.

METHODS: The location, size, type of aneurysm, clinical presentation, treatment, complications, and outcomes associated with 34 distal PCA aneurysms in 33 patients (15 females, 18 males; mean age, 44 years) were reviewed retrospectively.

RESULTS: The most common presenting symptom was headache in 19 (58%) followed by contralateral weakness or numbness in 6 (18%) and visual changes in 4 (12%). Eight aneurysms were giant. Of the remaining 26 aneurysms, 17 were fusiform/dissecting, 5 were saccular, and 4 were mycotic. Treatment was primarily endovascular in 22 patients, 12 of whom also had a concomitant surgical bypass procedure. Nine patients underwent microsurgical clipping, and 3 underwent combined treatment of clipping and coiling and/or stenting. There were no significant differences in outcomes between the groups (P=.078). The recurrence rate in patients undergoing coiling was 22% and 0% in patients undergoing clipping. Fourteen aneurysms (41%) involved treatment with an occipital artery-to-PCA bypass or an onlay graft. Compared with their preoperative status, these patients had significantly worse outcomes than those without a bypass (P=.013).

CONCLUSION: Bypass techniques for the treatment of distal PCA aneurysms are associated with a higher rate of complications than once thought. In our new treatment paradigm, bypass is a last resort and reserved for patients in whom balloon-test occlusion fails, who refuse parent-vessel sacrifice, and who cannot undergo primary stenting with coiling or clip wrapping.

Steve W. Chang

Papers

Biomechanics of Lumbar Cortical Screw-Rod Fixation Versus Pedicle Screw-Rod Fixation With and Without Interbody Support

Normobaric oxygen therapy strategies in the treatment of postcraniotomy pneumocephalus.

Surgical technique and outcomes in the treatment of spinal cord ependymomas, part 1: intramedullary ependymomas.

Gamma Knife surgery for hypothalamic hamartomas and epilepsy: patient selection and outcomes.

Treatment of distal posterior cerebral artery aneurysms: a critical appraisal of the occipital artery-to-posterior cerebral artery bypass.