The rate of screw misplacement in segmental pedicle screw fixation in adolescent idiopathic scoliosis

Augmented reality in spine surgery - past, present, and future

BACKGROUND CONTEXT

Augmented reality (AR) is increasingly recognized as a valuable tool in spine surgery. Here we provides an overview of the key developments and technological milestones that have laid the foundation for AR applications in this field. We also assess the quality of existing studies on AR systems in spine surgery and explore potential future applications.

PURPOSE

The purpose of this narrative review is to examine the role of AR in spine surgery. It aims to highlight the evolution of AR technology in this context, evaluate the existing body of research, and outline potential future directions for integrating AR into spine surgery.

STUDY DESIGN

Narrative review.

METHODS

We conducted a thorough literature search to identify studies and developments related to AR in spine surgery. Relevant articles, reports, and technological advancements were analyzed to establish the historical context and current state of AR in this field.

RESULTS

The review identifies significant milestones in the development of AR technology for spine surgery. It discusses the growing body of research and highlights the strengths and weaknesses of existing investigations. Additionally, it presents insights into the potential for AR to enhance spine surgical education and speculates on future applications.

CONCLUSIONS

Augmented reality has emerged as a promising adjunct in spine surgery, with notable advancements and research efforts. The integration of AR into the spine surgery operating room holds promise, as does its potential to revolutionize surgical education. Future applications of AR in spine surgery may include real-time navigation, enhanced visualization, and improved patient outcomes. Continued development and evaluation of AR technology are essential for its successful implementation in this specialized surgical field.

100 Complex posterior spinal fusion cases performed with robotic instrumentation

Robotic navigation has been shown to increase precision, accuracy, and safety during spinal reconstructive procedures. There is a paucity of literature describing the best techniques for robotic-assisted spine surgery for complex, multilevel cases or in cases of significant deformity correction. We present a case series of 100 consecutive multilevel posterior spinal fusion procedures performed for multilevel spinal disease and/or deformity correction. 100 consecutive posterior spinal fusions were performed for multilevel disease and/or deformity correction utilizing robotic-assisted placement of pedicle screws. The primary outcome was surgery-related failure, which was defined as hardware breakage or reoperation with removal of hardware. A total of 100 consecutive patients met inclusion criteria. Among cases included, 31 were revision surgeries with existing hardware in place. The mean number of levels fused was 5.6, the mean operative time was 303 min, and the mean estimated blood loss was 469 mL. 28 cases included robotic-assisted placement of S2 alar-iliac (S2AI) screws. In total, 1043 pedicle screws and 53 S2AI screws were placed with robotic-assistance. The failure rate using survivorship analysis was 18/1043 (1.7%) and the failure rate of S2AI screws using survivorship analysis was 3/53 (5.7%). Four patients developed postoperative wound infections requiring irrigation and debridement procedures. None of the 1043 pedicle screws nor the 53 S2AI screws required reoperation due to malpositioning or suboptimal placement. This case series of 100 multilevel posterior spinal fusion procedures demonstrates promising results with low failure rates. With 1043 pedicle screws and 53 S2AI screws, we report low failure rates of 1.7% and 5.7%, respectively with zero cases of screw malpositioning. Robotic screw placement allows for accurate screw placement with no increased rate of postoperative infection compared to historical controls. Level of evidence: IV, Retrospective review.

Photoacoustic Imaging and Characterization of Bone in Medicine: Overview, Applications, and Outlook

Photoacoustic techniques have shown promise in identifying molecular changes in bone tissue and visualizing tissue microstructure. This capability represents significant advantages over gold standards (i.e., dual-energy X-ray absorptiometry) for bone evaluation without requiring ionizing radiation. Instead, photoacoustic imaging uses light to penetrate through bone, followed by acoustic pressure generation, resulting in highly sensitive optical absorption contrast in deep biological tissues. This review covers multiple bone-related photoacoustic imaging contributions to clinical applications, spanning bone cancer, joint pathologies, spinal disorders, osteoporosis, bone-related surgical guidance, consolidation monitoring, and transsphenoidal and transcranial imaging. We also present a summary of photoacoustic-based techniques for characterizing biomechanical properties of bone, including temperature, guided waves, spectral parameters, and spectroscopy. We conclude with a future outlook based on the current state of technological developments, recent achievements, and possible new directions.

Retrospective analysis of reasons and revision strategy for failed thoracolumbar fracture surgery by posterior approach: a series of 31 cases

OBJECTIVES

This study aimed to analyze the reasons for failed thoracolumbar fracture treated with posterior surgical approaches and to discuss the revision strategies for the surgical treatment.

METHODS

We retrospectively studied the patients that received failed thoracolumbar fracture (T11-L2) treatment with posterior approach and underwent revision surgery in our spine department from March 2010 to December 2020.

RESULTS

A total of 31 patients were included in this study. There were 4 (12.9%) cases of A3, 2 (6.5%) cases of B1, 5 (16.1%) cases of B2, 7 (22.6%) cases of B3, and 13 (41.9%) cases of C, according to the AO classification for thoracolumbar injuries. For load sharing classification, 26 (83.9%) cases ≥7, and 5 (16.1%) cases < 7. Regarding to the reasons for surgery failure, 26 cases (83.9%) were due to fracture of the internal fixation (pedicle screw or connecting rod) and kyphosis, 3 cases (9.7%) were due to misplacement of the posterior pedicle screw, 1 case (3.2%) was due to incomplete posterior decompression, and 1 case (3.2%) was due to scoliosis after the removal of the internal fixation. The revision surgery methods included: 2 cases (6.5%) with anterior approach, 17 cases (54.8%) with posterior approach, and 12 cases (38.7%) with posterior and anterior approach. All the patients were followed-up for 12-24 months after the revision surgery, and successful bony fusion with no internal fixation failure was observed. The kyphosis angle improved significantly after the revision surgery in 26 patients at the last follow-up, and the final correction rate was 91.8%. Frankel grading system, visual analog scale (VAS), Oswestry Disability Index (ODI) showed significant improvement at the last follow-up.

CONCLUSIONS

Types B and C of thoracolumbar fracture, load sharing classification ≥7, and the posterior approach could lead to a high failure rate. Fracture of the internal fixation was the main reason for surgery failure. Performing the posterior approach is inappropriate for every thoracolumbar fracture. Reasonable revision surgery can achieve good results for posterior surgery failure in most cases.

Uso de guia tridimensional personalizado no preparo do orifício do pedículo piloto em deformidades da coluna vertebral

Objective  The present study aimed to develop and evaluate the use of customized guides in patients undergoing surgery to correct vertebral deformity with a pedicular fixation system.

Methods  Four patients with spinal deformity (three with idiopathic scoliosis and one with congenital kyphoscoliosis) underwent surgical treatment to correct the deformity with a pedicular fixation system. Prototypes of 3D cost guides were developed and evaluated using technical feasibility, accuracy, and radiation exposure.

Results  The present study included 85 vertebral pedicles in which pedicle screws were inserted into the thoracic spine (65.8%) and into the lumbar spine (34.2%). Technical viability was positive in 46 vertebral pedicles (54.1%), with 25 thoracic (54%) and 21 lumbar (46%). Technical viability was negative in 39 pedicles (45.9%), 31 of which were thoracic (79.5%), and 8 were lumbar (20.5%). In assessing accuracy, 36 screws were centralized (78.2%), of which 17 were in the thoracic (36.9%) and 19 in the lumbar spine (41.3%). Malposition was observed in 10 screws (21.7%), of which 8 were in the thoracic (17.4%) and 2 in the lumbar spine (4.3%). The average radiation record used in the surgical procedures was of 5.17 ± 0.72 mSv, and the total time of use of fluoroscopy in each surgery ranged from 180.3 to 207.2 seconds.

Conclusion  The customized guide prototypes allowed the safe preparation of the pilot orifice of the vertebral pedicles in patients with deformities with improved accuracy and reduced intraoperative radiation.

[Study on robot-assisted pedicle screw implantation in adolescent idiopathic scoliosis surgery]

Objective

To investigate the safety and accuracy of robot-assisted pedicle screw implantation in the adolescent idiopathic scoliosis (AIS) surgery.

Methods

The clinical data of 46 patients with AIS who were treated with orthopedics, bone graft fusion, and internal fixation via posterior approach between June 2018 and December 2019 were analyzed retrospectively. Among them, 22 cases were treated with robot-assisted pedicle screw implantation (robot group) and 24 cases with manual pedicle screw implantation without robot assistance (control group). There was no significant difference in gender, age, body mass index, Lenke classification, and preoperative Cobb angle of the main curve, pain visual analogue scale (VAS) score, Japanese Orthopaedic Association (JOA) score between the two groups ( P>0.05). The intraoperative blood loss, pedicle screw implantation time, intraoperative pedicle screw adjustment times, and VAS and JOA scores after operation were recorded. The Cobb angle of the main curve was measured on X-ray film and the spinal correction rate was calculated. The screw position and the accuracy of screw implantation were evaluated on CT images.

Results

The operation completed successfully in the two groups. The intraoperative blood loss, pedicle screw implantation time, and pedicle screw adjustment times in the robot group were significantly less than those in the control group ( P<0.05). There was 1 case of poor wound healing in the robot group and 2 cases of mild nerve root injury and 2 cases of poor incision healing in the control group, and there was no significant difference in the incidence of complications between the two groups ( P=0.667). All patients in the two groups were followed up 3-9 months (mean, 6.4 months). The VAS and JOA scores at last follow-up in the two groups were superior to those before operation ( P<0.05), but there was no significant difference in the difference of pre- and post-operative scores between the two groups ( P>0.05). The imaging review showed that 343 screws were implanted in the robot group and 374 screws in the control group. There were significant differences in pedicle screw implantation classification and accuracy between the two groups (89.5% vs 79.1%)( Z=-3.964, P=0.000; χ ²=14.361, P=0.000). At last follow-up, the Cobb angles of the main curve in the two groups were significantly lower than those before operation ( P<0.05), and there was significant difference in the difference of pre- and post-operative Cobb angles between the two groups ( t=0.999, P=0.323). The spinal correction rateswere 79.82%±5.33% in the robot group and 79.62%±5.58% in the control group, showing no significant difference ( t=0.120, P=0.905).

Conclusion

Compared with manual pedicle screw implantation, robot-assisted pedicle screw implantation in AIS surgery is safer, less invasive, and more accurate.

Augmented Reality in Spine Surgery: A Narrative Review

Augmented reality (AR) navigation refers to novel technologies that superimpose images, such as radiographs and navigation pathways, onto a view of the operative field. The development of AR navigation has focused on improving the safety and efficacy of neurosurgical and orthopedic procedures. In this review, the authors focus on 3 types of AR technology used in spine surgery: AR surgical navigation, microscope-mediated heads-up display, and AR head-mounted displays. Microscope AR and head-mounted displays offer the advantage of reducing attention shift and line-of-sight interruptions inherent in traditional navigation systems. With the U.S. Food and Drug Administration's recent clearance of the XVision AR system (Augmedics, Arlington Heights, IL), the adoption and refinement of AR technology by spine surgeons will only accelerate.

Combined Ultrasound and Photoacoustic Image Guidance of Spinal Pedicle Cannulation Demonstrated With Intact ex vivo Specimens

OBJECTIVE

Spinal fusion surgeries require accurate placement of pedicle screws in anatomic corridors without breaching bone boundaries. We are developing a combined ultrasound and photoacoustic image guidance system to avoid pedicle screw misplacement and accidental bone breaches, which can lead to nerve damage.

METHODS

Pedicle cannulation was performed on a human cadaver, with co-registered photoacoustic and ultrasound images acquired at various time points during the procedure. Bony landmarks obtained from coherence-based ultrasound images of lumbar vertebrae were registered to post-operative CT images. Registration methods were additionally tested on an ex vivo caprine vertebra.

RESULTS

Locally weighted short-lag spatial coherence (LW-SLSC) ultrasound imaging enhanced the visualization of bony structures with generalized contrast-to-noise ratios (gCNRs) of 0.99 and 0.98-1.00 in the caprine and human vertebrae, respectively. Short-lag spatial coherence (SLSC) and amplitude-based delay-and-sum (DAS) ultrasound imaging generally produced lower gCNRs of 0.98 and 0.84, respectively, in the caprine vertebra and 0.84-0.93 and 0.34-0.99, respectively, in the human vertebrae. The mean ± standard deviation of the area of -6 dB contours created from DAS photoacoustic images acquired with an optical fiber inserted in prepared pedicle holes (i.e., fiber surrounded by cancellous bone) and holes created after intentional breaches (i.e., fiber exposed to cortical bone) was 10.06 ±5.22 mm ² and 2.47 ±0.96 mm ², respectively (p 0.01).

CONCLUSIONS

Coherence-based LW-SLSC and SLSC beamforming improved visualization of bony anatomical landmarks for ultrasound-to-CT registration, while amplitude-based DAS beamforming successfully distinguished photoacoustic signals within the pedicle from less desirable signals characteristic of impending bone breaches.

SIGNIFICANCE

These results are promising to improve visual registration of ultrasound and photoacoustic images with CT images, as well as to assist surgeons with identifying and avoiding impending bone breaches during pedicle cannulation in spinal fusion surgeries.

Use of intraoperative navigation for posterior spinal fusion in adolescent idiopathic scoliosis surgery is safe to consider

PURPOSE

The use of image-guided stereotactic navigation is increasing in use in treating AIS; however, no studies have investigated perioperative outcomes and short-term adverse events compared with non-navigated procedures. The aim of the present study is to use a large national pediatric database to assess the rate of utilization of intraoperative navigation in pediatric patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis (AIS) and to compare thirty-day outcomes of navigated vs. non-navigated surgery.

METHODS

The NSQIP-Pediatric database was queried for cases of posterior fusion for AIS. Patients were stratified by whether or not a concurrent code for stereotactic navigation was used (CPT 61,783). Year of procedure, demographics, comorbidities, operative variables and perioperative adverse outcomes were abstracted and assessed using univariate and multivariate analysis.

RESULTS

Overall, 12,739 non-navigated patients and 340 navigated patients were identified. The use of navigation increased from 0.5% of cases in 2012 to 5.2% of cases in 2018. Demographics, comorbidities, and number of levels fused did not differ between navigated and non-navigated patients. Navigated cases were on average 41 min longer than non-navigated cases (268.6 vs. 309.6 min p < 0.001), with 9.84% more cases requiring transfusion (65.0% vs 75.6%, p < 0.001). Hospital stay for navigated cases was an average of 0.4 days shorter (3.9 days vs 4.3 days, p = 0.001). On multivariate analysis, navigated cases had higher odds of prolonged surgery (OR = 2.13, p < 0.001) and lower odds of prolonged length of stay (OR = 0.28, p < 0.001).

CONCLUSION

Although the use of navigation for AIS posterior fusion was associated with longer operative time, post-operative hospital stay was shorter and other perioperative adverse outcomes were not significantly different between groups.

Gold Nanoclusters for NIR-II Fluorescence Imaging of Bones

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for deep tissue visualization. Development of novel clinical translatable NIR-II probes is crucial for realizing the medical applications of NIR-II fluorescence imaging. Herein, the glutathione-capped gold nanoclusters (AuNCs, specifically Au₂₅ (SG)₁₈ ) demonstrate highly efficient binding capability to hydroxyapatite in vitro for the first time. Further in vivo NIR-II fluorescence imaging of AuNCs indicate that they accumulate in bone tissues with high contrast and signal-background ratio. AuNCs are also mainly and quickly excreted from body through renal system, showing excellent ribs and thoracic vertebra imaging because of no background signal in liver and spleen. The deep tissue penetration capability and high resolution of AuNCs in NIR-II imaging render their great potential for fluorescence-guided surgery like spinal pedicle screw implantation. Overall, AuNCs are highly promising and clinical translatable NIR-II imaging probe for visualizing bone and bone related abnormalities.

Comparison of Navigated versus Fluoroscopic-Guided Pedicle Screw Placement Accuracy and Complication Rate

OBJECTIVES

Accurate placement of the pedicle screw is requisite for any successful spinal instrumentation procedure. Screw insertion can be achieved using free-hand and fluoroscopic- or navigation-guided techniques. We sought to assess the variation in accuracy between fluoroscopic- and navigation-guided techniques, which are both used in Sheffield Teaching Hospitals National Health Service Trust, a tertiary spine referral center.

METHODS

Using a retrospective study design, we assessed all the pedicle screws placed between 2013 and 2018. Radiographic and clinical assessment of all cases was performed.

RESULTS

We studied 176 spinal instrumented cases, with a total of 831 screws implanted, out of which 296 (35.6%) were navigated and 535 (64.4%) were fluoroscopic guided. Pathology treated included spinal stenosis, spondylolisthesis, tumors, and trauma. Suboptimal screw position was identified in 2.03% (n = 6) of the navigation-guided series and 4.11% (n = 22) of the fluoroscopic-guided series with an overall screw misplacement rate of 3.4%. Evaluating surgeons' individual accuracy rates revealed that suboptimal screw placement registered a higher variation for the fluoroscopy-guided technique, and the misplacement rate was higher for surgeons with a lower volume of cases.

CONCLUSIONS

Use of navigation during spinal instrumentation helps lower the rate of screw misplacement for spinal surgeons who are at the beginning of their learning curve or do not frequently perform this kind of procedure. Navigation-guided spinal instrumentation is more accurate compared with fluoroscopic-guided techniques and appears to have a lower complication rate.

Photoacoustic imaging for surgical guidance: Principles, applications, and outlook

Minimally invasive surgeries often require complicated maneuvers and delicate hand-eye coordination and ideally would incorporate "x-ray vision" to see beyond tool tips and underneath tissues prior to making incisions. Photoacoustic imaging has the potential to offer this feature but not with ionizing x-rays. Instead, optical fibers and acoustic receivers enable photoacoustic sensing of major structures-such as blood vessels and nerves-that are otherwise hidden from view. This imaging process is initiated by transmitting laser pulses that illuminate regions of interest, causing thermal expansion and the generation of sound waves that are detectable with conventional ultrasound transducers. The recorded signals are then converted to images through the beamforming process. Photoacoustic imaging may be implemented to both target and avoid blood-rich surgical contents (and in some cases simultaneously or independently visualize optical fiber tips or metallic surgical tool tips) in order to prevent accidental injury and assist device operators during minimally invasive surgeries and interventional procedures. Novel light delivery systems, counterintuitive findings, and robotic integration methods introduced by the Photoacoustic & Ultrasonic Systems Engineering Lab are summarized in this invited Perspective, setting the foundation and rationale for the subsequent discussion of the author's views on possible future directions for this exciting frontier known as photoacoustic-guided surgery.

Validity of a Novel Free-Hand Pedicle Screw Placement Training Tool

INTRODUCTION

This study establishes the construct validity of a low-cost training platform designed for high-repetition training of the skills required for fluent use of the five specific tools described for free-hand pedicle screw placement and breach avoidance.

METHODS

A total of 19 participants were included and divided into three groups based on spine surgery experience. Participants were asked to place five pedicle screws into the model. The performance was assessed by recording breaches, technical criteria (0 to 44 points), time to completion, and angulation of the screws. Success (no breaches, no protrusions) frequency (success/time) was calculated and analyzed.

RESULTS

Participants included three spine surgeons, seven advanced trainees (who had placed >10 pedicle screws), and nine inexperienced trainees. None of the screws placed by the spine surgeons breached the pedicle wall. Eight of 35 screws placed by advanced trainees (22.9%) and 31 of 45 screws placed by inexperienced trainees (68.9%) had a pedicle breach. Spine surgeons had a higher median success frequency compared with inexperienced trainees and advanced trainees (P = 0.015). The time needed to place a screw decreased over time (P < 0.0001). There was a trend toward an association between increased training level and decreased time to place five screws (P = 0.076). Increased training level was associated with greater total points scored (P < 0.0001). More screws placed by inexperienced trainees were further away from the ideal pedicle axis compared with those placed by advanced trainees or spine surgeons.

CONCLUSION

An association exists between training level and performance on the pedicle screw model, which suggests construct validity when evaluating our model's use for teaching surgeon learners. The model is easily assembled and is an alternative spine surgery training tool that overcomes limited availability and considerable costs of other training platforms. It can be used in high repetition to establish tool-skill fluency.

LEVEL OF EVIDENCE

Level I.

Photoacoustic imaging of a human vertebra: implications for guiding spinal fusion surgeries

It is well known that there are structural differences between cortical and cancellous bone. However, spinal surgeons currently have no reliable method to non-invasively determine these differences in real-time when choosing the optimal starting point and trajectory to insert pedicle screws and avoid surgical complications associated with breached or weakened bone. This paper explores 3D photoacoustic imaging of a human vertebra to noninvasively differentiate cortical from cancellous bone for this surgical task. We observed that signals from the cortical bone tend to appear as compact, high-amplitude signals, while signals from the cancellous bone have lower amplitudes and are more diffuse. In addition, we discovered that the location of the light source for photoacoustic imaging is a critical parameter that can be adjusted to non-invasively determine the optimal entry point into the pedicle. Once inside the pedicle, statistically significant differences in the contrast and SNR of signals originating from the cancellous core of the pedicle (when compared to signals originating from the surrounding cortical bone) were obtained with laser energies of 0.23-2.08 mJ (p  <  0.05). Similar quantitative differences were observed with an energy of 1.57 mJ at distances  ⩾6 mm from the cortical bone of the pedicle. These quantifiable differences between cortical and cancellous bone (when imaging with an ultrasound probe in direct contact with each bone type) can potentially be used to ensure an optimal trajectory during surgery. Our results are promising for the introduction and development of photoacoustic imaging systems to overcome a wide range of longstanding challenges with spinal surgeries, including challenges with the occurrence of bone breaches due to misplaced pedicle screws.

Development of a Saw Bones Model for training pedicle screw placement in scoliosis

Objective

The purpose of this study was to determine if a Sawbones Scoliosis Model could be used as a simulator to train residents in placing pedicle screws—a complex procedure with a steep learning curve. Surgical simulation, a common tool teaching residents complex procedures in a safe environment, was staged using a Sawbones Scoliosis Model. Ten junior and ten senior residents out of 25 total possible residents (80%) were instructed how to place pedicle screws using the free-hand technique. They were then asked to place them unilaterally from T4 to L4 and were assessed on completion time, accuracy placement accuracy, and overall competency using an objective rating scale.

Results

Senior residents had an average time to completion of 38.9 ± 4.7 min vs. junior’s 50.1 ± 11.7 min, and a pedicle screw accuracy of 43.6 ± 6.4% vs. junior’s 44.4 ± 17.4%. Overall competency scores were similar for both groups; however, senior residents scored higher in the time and motion subdomain. Senior residents had a faster completion time and were more efficient, suggesting greater experience in spine surgery. The low rate of screw accuracy in both groups validates that simulation is a safe way for trainees to learn complex tasks.

Intraoperative image guidance compared with free-hand methods in adolescent idiopathic scoliosis posterior spinal surgery: a systematic review on screw-related complications and breach rates

BACKGROUND CONTEXT

Severe adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity requiring surgery to stop curve progression. Posterior spinal instrumentation and fusion with pedicle screws is the standard surgery for AIS curve correction. Vascular and neurologic complications related to screw malpositioning are concerns in surgeries for AIS. Breach rates are reported at 15.7%, implant-related complications at 1.1%, and neurologic deficit at 0.8%. Free-hand screw insertion remains the prevailing method of screw placement, whereas image guidance has been suggested to improve placement accuracy.

PURPOSE

This study aimed to systematically review the screw-related complication and breach rates from posterior spinal instrumentation and fusion with pedicle screws for patients with AIS when using free-hand methods for screw insertion compared with image guidance methods.

STUDY DESIGN

This is a systematic review of prognosis, comparing image guidance with no image guidance in surgery.

PATIENT SAMPLE

One randomized controlled trial and multiple prospective cohort studies that reported complication or breach rates in posterior spinal instrumentation and fusion with pedicle screws for AIS.

OUTCOME MEASURES

Number of complications and breaches reported in databases or recorded from postoperative imaging.

METHODS

Databases searched included MEDLINE, Embase, CINAHL, CENTRAL, and Web of Science. Studies of Level 3 evidence or greater as defined by the Centre for Evidence-Based Medicine were included. Articles were screened to focus on patients with AIS undergoing posterior fusion with pedicle screws or hybrid systems. Two independent reviewers screened abstracts, full texts, and extracted data. The Quality in Prognostic Studies (QUIPS) appraisal tool was used to determine studyrisk of bias (ROB). Level of evidence summary statements were formulated based on consistency and quality of reporting.

RESULTS

Seventy-nine cohort studies were identified, including four comparing computed tomography (CT) guidance with free-hand methods head-to-head, eight on image guidance, and 671. on free-hand methods alone. Moderate evidence from individual head-to-head studies show CT guidance has lower breach rates than free-hand methods. No complications were found in these studies. From individual cohort studies, moderate evidence shows CT guidance has lower point estimates of breach rates than free-hand methods at 7.9% compared with 9.7%-17.1%. Screw-related complication rates are conflicting at 0% in CT navigation compared with 0%-1.7% in 13 low- and moderate-quality studies.

CONCLUSIONS

Although point estimates on breach rates are decreased with CT navigation compared with free-hand methods, complication rates remain conflicting between the two methods. Current evidence is limited by small sample sizes, lack of comparison groups, and poorly predefined complications. Randomized controlled trials with larger samples with standardized definitions and recording of predefined breach and complication occurrences are recommended.

Surgical Treatment of Thoracolumbar Segmental Spinal Dysgenesis: Optimal Type of Fusion

OBJECTIVES

We sought to evaluate long-term results of surgical treatment of thoracolumbar segmental spinal dysgenesis (SSD).

METHODS

We analyzed 8 patients with thoracolumbar SSD treated in our institution. Each case was evaluated for specific clinical and radiologic criteria and types and outcomes of treatment.

RESULT

The average age of primary surgery was 3.4 years (median 3.4 years, range 1.7-7 years). The average correction of kyphosis was 49.3° (mean 45°, from 25°-75°) and scoliosis 10.6° (mean 10°, from 0°-25°). Average follow-up time was 3.2 years (mean 2.6 years, from 1.8-5.6 years). Neurologic improvement was also achieved in all patients. The Japanese Orthopaedic Association scale score (Benzel's modification) was increased by 2.5 points on average (mean 2.5 points, from 2-5 points). One patient had complications: pseudarthrosis and rod fracture followed by refusion.

CONCLUSIONS

Our treatment strategy provides favorable deformity correction and neurologic improvement. It is limited by immature vertebral structures in newborns and infants, who should be carefully monitored from birth with braces until they reach the age when a fixing tool can be used.

How Does Patient Radiation Exposure Compare With Low-dose O-arm Versus Fluoroscopy for Pedicle Screw Placement in Idiopathic Scoliosis?

BACKGROUND

Intraoperative C-arm fluoroscopy and low-dose O-arm are both reasonable means to assist in screw placement for idiopathic scoliosis surgery. Both using pediatric low-dose O-arm settings and minimizing the number of radiographs during C-arm fluoroscopy guidance decrease patient radiation exposure and its deleterious biological effect that may be associated with cancer risk. We hypothesized that the radiation dose for C-arm-guided fluoroscopy is no less than low-dose O-arm scanning for placement of pedicle screws.

METHODS

A multicenter matched-control cohort study of 28 patients in total was conducted. Fourteen patients who underwent O-arm-guided pedicle screw insertion for spinal fusion surgery in 1 institution were matched to another 14 patients who underwent C-arm fluoroscopy guidance in the other institution in terms of the age of surgery, body weight, and number of imaged spine levels. The total effective dose was compared. A low-dose pediatric protocol was used for all O-arm scans with an effective dose of 0.65 mSv per scan. The effective dose of C-arm fluoroscopy was determined using anthropomorphic phantoms that represented the thoracic and lumbar spine in anteroposterior and lateral views, respectively. The clinical outcome and complications of all patients were documented.

RESULTS

The mean total effective dose for the O-arm group was approximately 4 times higher than that of the C-arm group (P<0.0001). The effective dose for the C-arm patients had high variability based on fluoroscopy time and did not correlate with the number of imaged spine levels or body weight. The effective dose of 1 low-dose pediatric O-arm scan approximated 85 seconds of the C-arm fluoroscopy time. All patients had satisfactory clinical outcomes without major complications that required returning to the operating room.

CONCLUSIONS

Radiation exposure required for O-arm scans can be higher than that required for C-arm fluoroscopy, but it depends on fluoroscopy time. Inclusion of more medical centers and surgeons will better account for the variability of C-arm dose due to distinct patient characteristics, surgeon's preference, and individual institution's protocol.

LEVEL OF EVIDENCE

Level III-case-control study.

Precision and accuracy of consumer-grade motion tracking system for pedicle screw placement in pediatric spinal fusion surgery

Adolescent idiopathic scoliosis (AIS) is a 3-dimensional spinal deformity involving lateral curvature and axial rotation. Surgical intervention involves insertion of pedicle screws into the spine, requiring accuracies of 1mm and 5° in translation and rotation to prevent neural and vascular complications. While commercial CT-navigation is available, the significant cost, bulk and radiation dose hinders their use in AIS surgery. The objective of this study was to evaluate a commercial-grade Optitrack Prime 13W motion capture cameras to determine if they can achieve adequate accuracy for screw insertion guidance in AIS. Static precision, camera and tracked rigid body configurations, translational and rotational accuracy were investigated. A 1-h camera warm-up time was required to achieve precisions of 0.13mm and 0.10°. A three-camera system configuration with cameras at equal height but staggered depth achieved the best accuracy. A triangular rigid body with 7.9mm markers had superior accuracy. The translational accuracy for motions up to 150mm was 0.25mm while rotational accuracy was 4.9° for rotations in two directions from 0° to 70°. Required translational and rotational accuracies were achieved using this motion capture system as well as being comparable to surgical-grade navigators.

Switching to a Pediatric Dose O-Arm Protocol in Spine Surgery Significantly Reduced Patient Radiation Exposure

BACKGROUND

Intraoperative computed tomography and image-guided navigation improve the accuracy of screw placement. Radiation exposure to the patient remains a primary drawback. The objective of the present study was to compare the total intraoperative radiation dose and assess the resultant image quality for O-arm-assisted pedicle screw insertion, among 3 protocols: default (manufacturer recommended), institutional (reduced dose utilized in our institution), and pediatric (new protocol with lowest dose).

METHODS

Thirty-seven consecutive patients under the age of 18 years underwent posterior instrumentation of the spine and underwent an intraoperative O-arm scan. Techniques (kV and mAs) for default and institutional dose settings were manually adjusted based on spinal level and body weight. Pediatric dose techniques were 80 kV/80 mAs with no adjustment for level or weight. The number of scans repeated because of inadequate imaging was assessed, and the mean estimated effective dose between the 3 protocols was compared.

RESULTS

Sixty-eight scans were performed in 37 consecutive patients with mean age of 14 years and mean weight of 55 kg. For reference, the effective radiation dose of a chest x-ray is approximately 0.10 mSv. Use of the default protocol resulted in higher mean effective dose per scan of 4.65 mSv, whereas institutional protocol resulted in 2.37 mSv. The pediatric protocol reduced the mean dose to 0.65 mSv. The total effective dose per surgery was: 1.17 mSv (pediatric), 3.83 mSv (institutional), and 12.79 mSv (default) (P<0.0001 each). All scans lead to satisfactory image quality except in 1 patient >100 kg with stainless steel implants. There were no neurological or other implant-related complications. The pediatric protocol resulted in satisfactory image quality with the lowest total radiation dose, only 1/10 of that of the default protocol.

CONCLUSIONS

We successfully switched to a pediatric low-dose O-arm protocol in clinical practice, reducing the dose to <1/4 of the mean annual natural background radiation. This may allow use of intraoperative computed tomography and navigation for pedicle screw placement without excessive radiation exposure to young patients.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Learning curve of 3D fluoroscopy image-guided pedicle screw placement in the thoracolumbar spine

BACKGROUND CONTEXT

During the past decade, a disproportionate increase of spinal fusion procedures has been observed. Along with this trend, image-guided spine surgery has been experiencing a renaissance in the recent years. A wide range of different navigation systems are available on the market today. However, only few published studies assess the learning curves concerning these new spinal navigation techniques. So far, a study on the learning curve for intraoperative three-dimensional fluoroscopy (3DFL)-navigated pedicle screw (PS) placement is still lacking.

PURPOSE

The purpose of the study was to analyze the learning curve for 3DFL-navigated thoracolumbar PS placement.

STUDY DESIGN/SETTING

The study design included a prospective case series.

PATIENT SAMPLE

A cohort of 145 patients were recruited from January 2011 to June 2012.

OUTCOME MEASURES

The outcome measures were duration of intraoperative 3D scans, PS placement, PS accuracy on postoperative computed tomography (CT) scans, and PS-related revisions and complications.

METHODS

From the introduction of spinal navigation to our department in January 2011 until June 2012, the learning curve for the duration of intraoperative 3D scan acquisition (navigation or control scan) and placement time per screw, intraoperative screw revisions, screw-related complications, revision surgeries, and PS accuracy on postoperative CT scans were assessed in 145 patients undergoing dorsal navigated instrumentation for 928 PS (736 lumbosacral and 192 thoracic). The observed time span was divided into four intervals. Results of the second, third, and last periods were compared with the first (reference) period, respectively.

RESULTS

The mean navigation 3D scan time decreased (first and fourth periods) from 15.4±7.8 (range, 4-40) to 8.4±3.3 (3-15) minutes (p<.001). The mean control 3D scan time (after PS placement) decreased from 11.2±4.8 (5-25) to 6.6±3.0 (3-15) minutes (p<.001). The mean PS insertion time decreased from 5.3±2.5 (1-15) to 3.2±2.3 (1-17) minutes (p<.001). The mean proportion of correctly positioned PS (all 928) according to the Gertzbein and Robbins classification grades A and B increased initially from 83.1% (first period) to 95.1% (second period, p=.001), 96.4% (third period, p=.002), and 92.4% (fourth period, p=.049). No learning effect was found with respect to intraoperative screw revisions. There was one revision surgery.

CONCLUSIONS

We could demonstrate significant learning effects for 3DFL-navigated PS placement with regard to intraoperative 3D scan acquisition, PS placement time, and PS accuracy.

Application of 3D rapid prototyping technology in posterior corrective surgery for Lenke 1 adolescent idiopathic scoliosis patients

A retrospective study to evaluate the effectiveness of 3-dimensional rapid prototyping (3DRP) technology in corrective surgery for Lenke 1 adolescent idiopathic scoliosis (AIS) patients. 3DRP technology has been widely used in medical field; however, no study has been performed on the effectiveness of 3DRP technology in corrective surgery for Lenke 1 AIS patients. Lenke 1 AIS patients who were preparing to undergo posterior corrective surgery from a single center between January 2010 and January 2012 were included in this analysis. Patients were divided into 2 groups. In group A, 3-dimensional (3D) printing technology was used to create subject-specific spine models in the preoperative planning process. Group B underwent posterior corrective surgery as usual (by free hand without image guidance). Perioperative and postoperative clinical outcomes were compared between 2 groups, including operation time, perioperative blood loss, transfusion volume, postoperative hemoglobin (Hb), postoperative complications, and length of hospital stay. Radiological outcomes were also compared, including the assessment of screw placement, postoperative Cobb angle, coronal balance, sagittal vertical axis, thoracic kyphosis, and lumbar lordosis. Subgroup was also performed according to the preoperative Cobb angle: mean Cobb angle <50° and mean Cobb angle >50°. Besides, economic evaluation was also compared between 2 groups. A total of 126 patients were included in this study (group A, 50 and group B, 76). Group A had significantly shorter operation time, significantly less blood loss and transfusion volume, and higher postoperative Hb (all, P < 0.001). However, no significant differences were observed in complication rate, length of hospital stay, and postoperative radiological outcomes between 2 groups (all, P>0.05). There was also no significant difference in misplacement of screws in total populations (16.90% vs 18.82%, P = 0.305), whereas a low misplacement rate of pedicle screws was observed in patients whose mean Cobb angle was >50° (9.15% vs 13.03%, P = 0.02). Besides, using 3DRP increased the economic burden of patients (157,000 ± 9948.85 Ren Min Bi (RMB) vs 152,500 ± 11,445.52 RMB, P = 0.03). Using the 3D printing technology before posterior corrective surgery might reduce the operation time, perioperative blood loss, and transfusion volume. There did not appear to be a benefit to using this technology with respect to complication rate and postoperative radiological outcomes; however, 3D technology could reduce the misplacement rate in patients whose preoperative mean Cobb angle was >50°. Besides, it also increased the patients' hospital cost. Therefore, future prospective studies are needed to elucidate the efficacy of this emerging technology.

Safety of pedicle screws and spinal instrumentation for pediatric patients: comparative analysis between 0- and 5-year-old, 5- and 10-year-old, and 10- and 15-year-old patients

STUDY DESIGN

Retrospective study.

OBJECTIVE

To investigate the safety of pedicle screws and constructs for infantile and juvenile patients with spinal deformity.

SUMMARY OF BACKGROUND DATA

Few studies have examined the safety and complication rates associated with the usage of pedicle screw for children younger than 10 years.

METHODS

Radiographical and clinical data were collected of patients treated with pedicle screws at a single institution. Patients were divided into 2 groups based on age (0-5 yr old, 5-10 yr) and compared with an older cohort of 10- to 15-year-old patients. Patient demographics, screw adjustment, and complication data were collected for each group. Outcomes were analyzed using analysis of variance (P < 0.05).

RESULTS

In total, 5054 pedicle screws were analyzed: 176 in the 0- to 5-year-old group (31 patients), 659 in the 5- to 10-year-old group (68 patients), and 4219 in the 10- to 15-year-old group (234 patients). Mean follow-up was 3.1 ± 1.8 years (range, 3 mo-9 yr). There were 7 pedicle screw-associated complications (3 required revision surgery). Overall pedicle screw-associated complication rates were 2.1% per patient and 0.1% per screw. There were no neurological complications associated with misplacement of a pedicle screw. The pedicle screw-associated complication rates per patient and per screw were 3.2% and 0.6% in the 0- to 5-year-old group, 2.9% and 0.3% in the 5- to 10-year-old group, and 1.7% and 0.1% in the 10- to 15-year-old group (P > 0.05). The 5- to 10-year-old group had a significantly higher overall surgically related complication rate (34%) than the 0- to 5-year-old group (7%) and the 10- to 15-year-old group (6%) (P = 0.005), primarily due to the "growth friendly" constructs common in this age group.

CONCLUSION

Pedicle screws can be used for infantile or juvenile patients, although complication rates associated with pedicle screws tended to be slightly higher in the younger groups.

Are More Screws Better? A Systematic Review of Anchor Density and Curve Correction in Adolescent Idiopathic Scoliosis

STUDY DESIGN

Systematic review of clinical studies.

OBJECTIVES

To critically evaluate existing literature to determine whether increased anchor or implant density (screws, wires, and hooks per level fused) results in improved curve correction for adolescent idiopathic scoliosis (AIS) surgery.

SUMMARY OF BACKGROUND DATA

Wide variability exists in the number of screws used for AIS surgery. High numbers of pedicle screws are increasingly used, but there is limited evidence to support this as best practice.

METHODS

Online English-language databases were searched to identify articles addressing anchor density. Articles were reviewed for anchor type/number, radiographic measures, and patient-reported outcomes.

RESULTS

Of 196 references identified, 10 studies totaling 929 patients met the inclusion criteria. Reported mean anchor density varied from 1.06 to 2.0 implants per level fused. Mean percent coronal curve correction varied from 64% to 70%. Two studies (463 patients) analyzed hook, hybrid (combined hooks and screws), and screw constructs as a single cohort. Both found increased correction with high-density constructs (p = .01, p < .001), perhaps as a result of the hooks and hybrid constructs. Eight retrospective studies and 1 prospective randomized, controlled trial had predominantly screw constructs (466 patients). Increased anchor density was not associated with improved curve correction. The studies evaluating screw density are significantly underpowered to detect a difference in curve correction.

CONCLUSIONS

Wide heterogeneity in anchor density exists in the surgical treatment of AIS. Reports evaluating the effects of increased anchor density are mostly retrospective and significantly underpowered to detect a difference in curve correction and patient outcomes. At this time, there is insufficient evidence to show that anchor density affects clinical outcomes in AIS.

Our experience and early results with a complementary implant for the correction of major thoracic curves

PURPOSE

In our article, we would like to introduce a new auxiliary implant called the CAB hook, for use in posterior approach scoliosis surgery.

METHODS

Since 2007, we operated 42 patients with the CAB hook with an average preoperative Cobb angle of 59.3° (28°-92°). In three cases, the posterior approach was preceded by ventral release and Halo traction. In four cases, besides the CAB hooks, SCS hooks and pedicular screws, in three cases both CAB and SCS hooks, in nine cases CAB hooks with SCS pedicular screws, and in 23 cases, only CAB were used. The average follow-up time was 21.6 month (2-51).

RESULTS

All the patients are satisfied with the results. No reoperation was needed due to the loss of correction, pain, implant failure, or infection. The average postoperative Cobb angle decreased to 24.7° (4°-60°). Based on this we calculated the Cincinnati Correction Index (CCI), which was 1.53 (0.7-4.8), which means that our correction exceeded the flexibility of the spine based on the lateral bending X-ray by 53 %.

CONCLUSION

As with all new surgical techniques and implants after the short learning curve, we were able to improve the degree of correction and decrease the time of surgery. One of the advantages of the CAB hook is that besides a few implant-specific instruments, no special instrumentation is required for insertion, and image intensifier need not be used.

Biomechanical analysis of vertebral derotation techniques for the surgical correction of thoracic scoliosis. A numerical study through case simulations and a sensitivity analysis

STUDY DESIGN

Biomechanical analysis of vertebral derotation techniques for the surgical correction of thoracic scoliosis.

OBJECTIVE

To model and analyze vertebral derotation maneuvers biomechanically to maximize the tridimensional correction of scoliosis and minimize the implant-vertebra forces.

SUMMARY OF BACKGROUND DATA

Vertebral derotation techniques were recently developed to improve the correction of scoliotic deformities in the transverse plane. Those techniques consist in applying a combination of moments and forces using a vertebral derotation device, cohesively linked to the thoracic apical pedicle screws, to derotate the spine and the rib cage. However, many variations of the technique exist and the correction mechanisms are not fully understood to achieve an optimal correction of scoliosis.

METHODS

A biomechanical model was developed to simulate the instrumentation surgery numerically of 4 Lenke type 1 patients with scoliosis, instrumented using a vertebral derotation device and vertebral derotation maneuvers as major correction technique. Then, for each case, 32 additional instrumentation surgical procedures were simulated to better understand the biomechanics of the vertebral derotation technique, varying the implant type and density, the number of derotation levels, the vertebral derotation angle and the posteriorly oriented force applied during the maneuver.

RESULTS

On average, among 32 additional simulations, there was an important variability of the resulting apical vertebral rotation (15°) and the mean resultant implant-vertebra force (205 N) but little variability for the main thoracic Cobb angle (6°) and the thoracic kyphosis (4°). The implant type, the implant density and the vertebral derotation angle were the parameters that most influenced the correction of scoliosis. The correction in the coronal and transverse planes was improved using monoaxial pedicle screw density of 2 and a bilateral vertebral derotation maneuver on 3 levels at the apex of the thoracic curve, with an extra 15° applied on the vertebral derotation device. When reducing the implant density by 50%, it was possible to reduce the mean implant-vertebra forces while keeping a good correction.

CONCLUSION

Biomechanically, it is possible to significantly improve the correction of thoracic scoliotic deformities, particularly in the transverse plane, when using vertebral derotation maneuvers.