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Kee D. Kim, J. Patrick Johnson, and Jesse D. Babbitz

Object

Thoracic pedicle screw fixation is effective and reliable in providing short-segment stabilization. Although the procedure is becoming more widely used, accurate insertion of the screws is difficult due to the small dimensions of thoracic pedicles, and the associated risk is high due to the proximity of the spinal cord. In previous studies authors have shown the accuracy of image-guided lumbar pedicle screw placement, but there have been no reported investigations into the accuracy of image-guided thoracic pedicle screw placement. The authors report their experience with such an investigation.

Methods

To evaluate the accuracy of image-guided thoracic pedicle screw placement in vitro and in vivo, thoracic pedicle screws were placed with an image-guidance system in five human cadavers and 10 patients. In cadavers, the accuracy of screw placement was assessed by postoperative computerized tomography and visual inspection and in patients by postoperative imaging studies. Of the 120 pedicle screws placed in five cadavers pedicle violation occurred in 23 cases (19.2%); there was one pedicle violation (4.2%) in each of the last two cadavers. Of the 45 pedicle screws placed in 10 patients, pedicle violations occurred in three (6.7%).

Conclusions

In comparison with historical controls, the accuracy of thoracic pedicle screw placement is improved with the use of an image-guidance system. It allows the surgeon to visualize the thoracic pedicle and the surrounding structures that are normally out of the surgical field of view. The surgeon, however, must be aware of the limitations of an image-guidance system and have a sound basic knowledge of spinal anatomy to avoid causing serious complications.

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Doniel Drazin, Terrence T. Kim, David W. Polly Jr, and J. Patrick Johnson

Image-guided surgery (IGS) has been evolving since the early 1990s and is now used on a daily basis in the operating theater for spine surgery at many institutions. In the last 5 years, spinal IGS has greatly benefitted from important enhancements including portable intraoperative CT (iCT) coupled with high-speed computerized stereotactic navigation systems and optical-based camera tracking technology.

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Terrence T. Kim, Doniel Drazin, Faris Shweikeh, Robert Pashman, and J. Patrick Johnson

Object

Intraoperative CT image–guided navigation (IGN) has been increasingly incorporated into minimally invasive spine surgery (MIS). The vast improvement in image resolution and virtual real-time images with CT-IGN has proven superiority over traditional fluoroscopic techniques. The authors describe their perioperative MIS technique using the O-arm with navigation, and they report their postoperative experience, accuracy results, and technical aspects.

Methods

A retrospective review of 48 consecutive adult patients undergoing minimally invasive percutaneous posterior spinal fusion with intraoperative CT-IGN between July 2010 and August 2013 at Cedars-Sinai Medical Center was performed. Two surgeons assessed 290 screws in a blinded fashion on intraoperative O-arm images and postoperative CT scans for bony pedicle wall breach. Grade 1 breach was defined to be < 2 mm, Grade 2 breach to be between 2 and 4 mm, and a Grade 3 breach to be > 4 mm. Additionally, anterior vertebral body breach was recorded.

Results

Of 290 pedicle screws placed, 280 (96.6%) were in an acceptable position without cortical wall or anterior breach. Of the 10 breaches (3.4%) 5 were lateral (50%), 4 were medial, and 1 was anterior; 90% of breaches were Grade 1–2 and all medial breaches were Grade 1. The one Grade 3 breach was lateral. No vascular or neurological complications were observed intraoperatively, and no significant postoperative complications were noted. The mean clinical follow-up period was 18 months (range 3–39 months). The overall clinical outcomes, measured using the visual analog scale (back pain scores), were improved significantly postoperatively at 3 months compared with preoperatively (visual analog score 6.35 vs 3.57; p < 0.0001). No revision surgery was performed for screw misplacement or neurological deterioration.

Conclusions

New CT-IGN with the mobile O-arm scanner has increased the accuracy of pedicle screw/instrumentation placement using MIS techniques. The authors' high (96.6%) accuracy rate in MIS compares favorably with historical published accuracy rates for fluoroscopy-based techniques. Additional advantages of CT-IGN over fluoroscopic imaging methods are lower occupational radiation exposure for the surgical team, reduced need for postoperative imaging, and decreased rates of revision surgery. For now, the authors simply conclude that use of intraoperative CT-IGN is safe and accurate.

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Jesse Jones, Alexander Lerner, Paul E. Kim, Meng Law, and Patrick C. Hsieh

Cervical spondylotic myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is a common neurosurgical disease that carries high morbidity. OPLL and other degenerative processes cause narrowing of the central canal, with subsequent spinal cord injury. Repeated minor trauma and vascular aberrations have been purported to underlie cervical spondylotic myelopathy, although the exact pathophysiological mechanism is unclear. Regardless, detection of early axonal damage may allow more timely surgical intervention and prediction of functional outcome. Diffusion tensor (DT) imaging of the cervical spine is a novel technique with improved sensitivity compared with conventional anatomical MR imaging that is currently available on most clinical scanners. This review describes the theoretical basis, application, and analysis of DT imaging as it pertains to neurosurgery. Particular emphasis is placed on OPLL.

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J. Patrick Johnson, Doniel Drazin, Wesley A. King, and Terrence T. Kim

Object

Video-assisted thoracoscopic surgery (VATS) has evolved for treatment of a variety of spinal disorders. Early incorporation with image-guided surgery (IGS) was challenged due to reproducibility and adaptability, limiting the procedure's acceptance. In the present study, the authors report their experience with second-generation IGS and VATS technologies for anterior thoracic minimally invasive spinal (MIS) procedures.

Methods

The surgical procedure is described in detail including operating room set-up, patient positioning (a lateral decubitus position), placement of the spinal reference frame and portal, radiographic localization, registration, surgical instruments, and the image-guided thoracoscopic discectomy.

Results

Combined IGS and VATS procedures were successfully performed and assisted in anatomical localization in 14 patients. The mean patient age was 59 years (range 32–73 years). Disc herniation pathology represented the most common indication for surgery (n = 8 patients); intrathoracic spinal tumors were present in 4 patients and the remaining patients had infection and ossification of the posterior longitudinal ligament. All patients required chest tube drainage postoperatively, and all but 1 patient had drainage discontinued the following day. The only complication was a seroma that was presumed to be due to steroid therapy for postoperative weakness. At the final follow-up, 11 of the patients were improved neurologically, 2 patients had baseline neurological status, and the 1 patient with postoperative weakness was able to ambulate, albeit with an assistive device.

The evolution of thoracoscopic surgical procedures occurring over 20 years is presented, including their limitations. The combination of VATS and IGS technologies is discussed including their safety and the importance of 3D imaging. In cases of large open thoracotomy procedures, surgeries require difficult, extensive, and invasive access through the chest cavity; using a MIS procedure can potentially eliminate many of the complications and morbidities associated with large open procedures. The authors report their experience with thoracic spinal surgeries that involved MIS procedures and the new technologies.

Conclusions

The most significant advance in IGS procedures has resulted from intraoperative CT scanning and automatic registration with the IGS workstation. Image guidance can be used in conjunction with VATS techniques for thoracic discectomy, spinal tumors, infection, and ossification of the posterior longitudinal ligament. The authors' initial experience has revealed this technique to be useful and potentially applicable to other MIS procedures.

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Paul N. Porensky, Patrick R. Maloney, Jeeho D. Kim, Justin A. Dye, and Peter C. Liacouras

OBJECTIVE

Decompressive craniectomy (DC) is the definitive neurosurgical treatment for managing refractory malignant cerebral edema and intracranial hypertension due to combat-related severe traumatic brain injury (TBI). To date, the long-term outcomes and sequelae of this procedure on host-country national (HCN) populations during Operation Iraqi Freedom (Iraq, 2003–2011), Operation Enduring Freedom (Afghanistan, 2001–2014), and Operation Freedom’s Sentinel (Afghanistan, 2015–2021) have not been described, specifically the process and results of delayed custom synthetic cranioplasty. The Joint Trauma System’s Clinical Practice Guidelines (JTS-CPG) for severe head injury counsels surgeons to discard the cranial osseous explant when treating coalition service members. Ongoing political and healthcare system instabilities often preclude opportunities for delayed cranioplasty by host-country assets. Various surgical options (such as hinge craniectomy) are inadequate in the setting of complicated cranial comminution from blast or missile injuries, severe cerebral edema, grossly contaminated wounds, complex polytrauma, and tissue devitalization. Delayed cranioplasty with a custom synthetic implant is a viable but logistically challenging alternative. In this retrospective review, the authors present the first patient series describing delayed custom synthetic cranioplasty in an HCN population performed during active military conflict.

METHODS

Patients were identified through the Joint Trauma System/Theater Medical Data Store, and subgroup analyses were performed to include mechanisms of injury, surgical complications, and clinical outcomes.

RESULTS

Twenty-five patients underwent DC between 2012 and 2020 to treat penetrating, blast, and high-energy closed head injuries per JTS-CPG criteria. The average time from injury to surgery was 1.4 days, although 6 patients received delayed care (3–6 days) due to protracted evacuation from local hospitals. Delayed care correlated with an increased rate of intracranial abscess and empyema. The average time to cranioplasty was 134 days due to a lack of robust mechanisms for patient follow-up, tracking, and access to NATO hospitals. HCN patients who recovered from DC demonstrated overall benefit from custom synthetic cranioplasty, although formal statistical analysis was impeded by a lack of long-term follow-up.

CONCLUSIONS

This review demonstrates that cranioplasty with a custom synthetic implant is a safe and feasible treatment for vulnerable HCN patients who survive their index DC surgery. This unique paradigm of care highlights the capabilities of deployed neurosurgical healthcare teams working in partnership with the prosthetics laboratory at Walter Reed National Military Medical Center.

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George Hanna, Terrence T. Kim, Syed-Abdullah Uddin, Lindsey Ross, and J. Patrick Johnson

OBJECTIVE

The purpose of this study was to describe the evolution of thoracoscopic spine surgery from basic endoscopic procedures using fluoroscopy and anatomical localization through developmental iterations to the current technology use in which endoscopy and image-guided surgery are merged with intraoperative CT scanning.

METHODS

The authors provided detailed explanations of their thoracoscopic spine surgery techniques, beginning with their early-generation endoscopy with fluoroscopic localization, which was followed with point surface matching techniques and early image guidance. The authors supplanted this with the modern era of image guidance, thoracoscopic spine surgery, and seamless integration that has reached its current level of refinement.

RESULTS

A retrospective review of single-institution thoracoscopic procedures performed by the senior author over the course of 19 years yielded a total of 160 patients, including 73 women and 87 men. The mean patient age was 55 years, and the range included patients 16–94 years of age. There were no patients with worsened neurological function. One hundred sixteen patients underwent surgery for thoracic disc herniation, 18 for underlying neoplasms with spinal cord compression, 14 for osteomyelitis and discitis, 12 for thoracic deformity with neurological changes, and 8 for traumatic etiologies.

CONCLUSIONS

More than 19 years of experience has revealed the benefits of integrating thoracoscopic spine surgery with intraoperative CT scanning and image-guided surgery, including direct decompression without manipulation of neural elements, superior 3D spatial orientation, and localization of complex spinal anatomy. With the exponential growth of machine learning, robotics, artificial intelligence, and advances in imaging techniques and endoscopic imaging, there may be further refinements of this technique on the horizon.

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Orin Bloch, Langston T. Holly, Jongsoo Park, Chinyere Obasi, Kee Kim, and J. Patrick Johnson

Object. In recent studies some authors have indicated that 20% of patients have at least one ectatic vertebral artery (VA) that, based on previous criteria in which preoperative computerized tomography (CT) and standard intraoperative fluoroscopic techniques were used, may prevent the safe placement of C1–2 transarticular screws. The authors conducted this study to determine whether frameless stereotaxy would improve the accuracy of C1–2 transarticular screw placement in healthy patients, particularly those whom previous criteria would have excluded.

Methods. The authors assessed the accuracy of frameless stereotaxy for C1–2 transarticular screw placement in 17 cadaveric cervical spines. Preoperatively obtained CT scans of the C-2 vertebra were registered on a stereotactic workstation. The dimensions of the C-2 pars articularis were measured on the workstation, and a 3.5-mm screw was stereotactically placed if the height and width of the pars interarticularis was greater than 4 mm. The specimens were evaluated with postoperative CT scanning and visual inspection. Screw placement was considered acceptable if the screw was contained within the C-2 pars interarticularis, traversed the C1–2 joint, and the screw tip was shown to be within the anterior cortex of the C-1 lateral mass.

Transarticular screws were accurately placed in 16 cadaveric specimens, and only one specimen (5.9%) was excluded because of anomalous VA anatomy. In contrast, a total of four specimens (23.5%) showed significant narrowing of the C-2 pars interarticularis due to vascular anatomy that would have precluded atlantoaxial transarticular screw placement had previous nonimage-guided criteria been used.

Conclusions. Frameless stereotaxy provides precise image guidance that improves the safety of C1–2 transarticular screw placement and potentially allows this procedure to be performed in patients previously excluded because of the inaccuracy of nonimage-guided techniques.

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Felipe C. Albuquerque, David J. Fiorella, Patrick P. Han, Vivek R. Deshmukh, Louis J. Kim, and Cameron G. Mcdougall

Object

Intracranial vertebral artery (VA) dissecting aneurysms often present with severe subarachnoid hemorrhage (SAH) and dramatic neurological injury. The authors reviewed the management of 23 cases in an effort to evaluate treatment efficacy and outcomes.

Methods

The records of 23 patients who underwent endovascular treatment were reviewed to determine symptoms, type of therapy, complications, and clinical outcomes. All patients were evaluated using records kept in a prospectively maintained database.

Ten men and 13 women (age range 35–72 years; mean age 49 years) were treated over an 8-year period. Twelve patients presented with poor-grade SAH, five with good-grade SAH, three with headache, and two with stroke. The other patient's aneurysm was discovered incidentally. Treatment included coil occlusion of the artery at the aneurysm in 21 patients and stent-assisted coil placement in two. Parent artery sacrifice was successful in all cases, whereas both patients treated with stent-assisted coil insertion suffered recurrences. No patient sustained permanent complications as a result of treatment. Two patients died due to the severity of their original SAH. Findings were normal in 14 patients on follow-up review (including five of the 12 presenting with poor-grade SAH), five had fixed neurological deficits but were able to care for themselves, and one was permanently disabled.

Conclusions

Despite their often aggressive neurological presentation, intracranial VA dissecting aneurysms can be managed safely with coil occlusion of the lesion and/or parent artery. Even patients presenting in poor neurological condition may improve dramatically.

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Joseph C. Hsieh, Doniel Drazin, Alexander O. Firempong, Robert Pashman, J. Patrick Johnson, and Terrence T. Kim

Object

Revision spine surgery, which is challenging due to disrupted anatomy, poor fluoroscopic imaging, and altered tactile feedback, may benefit from CT image-guided surgery (CT-IGS). This study evaluates accuracy of CT-IGS–navigated screws in primary versus revision spine surgery.

Methods

Pedicle and pelvic screws placed with the O-arm in 28 primary (313 screws) and 33 revision (429 screws) cases in which institutional postoperative CT scans were available were retrospectively reviewed for placement accuracy. Screw accuracy was categorized as 1) good (< 1-mm pedicle breach in any direction or “in-out-in” thoracic screws through the lateral thoracic pedicle wall and in the costovertebral joint); 2) fair (1- to 3-mm breach); or 3) poor (> 3-mm breach).

Results

Use of CT-IGS resulted in high rates of good or fair screws for both primary (98.7%) and revision (98.6%) cases. Rates of good or fair screws were comparable for the following regions: C7–T3 at 100% (good or fair) in primary versus 100% (good or fair) in revision; T4–9 at 96.8% versus 100%; T10–L2 at 98.2% versus 99.3%; L3–5 at 100% versus 99.2%; and pelvis at 98.7% versus 98.6%, respectively. On the other hand, revision sacral screws had statistically significantly lower rates of good placement compared with primary (100% primary vs 80.6% revision, p = 0.027). Of these revision sacral screws, 11.1% had poor placement, with bicortical screws extending > 3 mm beyond the anterior cortex. Revision pelvic screws demonstrated the highest rate of fair placement (28%), with the mode of medial breach in all cases directed into the sacral-iliac joint.

Conclusions

In the cervical, thoracic, and lumbar spine, CT-IGS demonstrated comparable accuracy rates for both primary and revision spine surgery. Use of 3D imaging of the bony pedicle anatomy appears to be sufficient for the spine surgeon to overcome the difficulties associated with instrumentation in revision cases. Although the bony structures of sacral pedicles and pelvis are relatively larger, the complexity of local anatomy was not overcome with CT-IGS, and an increased trend toward inaccurate screw placement was demonstrated.