Tag: pedicle screw

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Robotic Spine Surgery: Systematic Review of Common Error Types and Best Practices

Operative Neurosurgery 28:295–302, 2025

• Robotic systems enhance accuracy in pedicle screw placement, reducing complications and hospital stays.

• Common errors in robotic spine surgery include registration, skiving, and interference errors.

• Registration errors occur due to imaging discrepancies or unexpected intraoperative movements.

• Skiving errors result from sliding of drilling instruments, often due to poor entry points.

• Interference errors arise from unintended interactions with soft tissue or robotic system malfunctions.

• Best practices include meticulous preoperative planning and careful patient positioning to minimize errors.

• High BMI and female sex are risk factors for screw deviation due to bone quality issues.

• Modern systems use sharp burrs to reduce skiving by ensuring smooth entry points.

• Soft tissue management is crucial to prevent interference errors during surgery.

• Intraoperative imaging helps confirm accurate screw placement, reducing registration errors.

• Screw failure rates: Registration errors (60%), skiving errors (26.8%), interference errors (19.5%).

• Newer robotic systems show improved accuracy but still face challenges with registration errors.

• Study limitations include varied resources, surgeon experience, and subjective error reporting.

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Impact of landmark crater creation on improving accuracy of pedicle screw insertion in robot-assisted scoliosis surgery

European Spine Journal (2024) 33:4730–4739

This study evaluated the impact of the Landmark Crater (LC) method on pedicle perforation rates in robot-guided surgery for pediatric scoliosis for each pedicle diameter.

Methods Seventy-six scoliosis patients underwent robot-assisted posterior spinal fusion. The cohort consisted of 19 male and 57 female patients, with a mean ± standard deviation age of 17.5 ± 7.7 years and a preoperative Cobb angle of 57.0 ± 18.5°. The LC method is a method in which craters that serves as a landmark are created in advance at the planned PS insertion site of all pedicles within the intraoperative CT imaging area. The patients were divided into the LC group, in which PS insertion was performed using the LC method, and the control group using the conventional PS insertion method. Overall and pedicle perforation rates for each pedicle outer diameter were compared between the groups by Fisher’s exact test.

Results The LC group exhibited a significantly lower pedicle major perforation rate than did the control group (2.7% vs. 6.2%, P = 0.001). The perforation rates in pedicles with a pedicle outer diameter > 6 mm, 4–6 mm, 2–4 mm, and < 2 mm were 0.61%, 1.6%, 5.1%, and 21%, in the LC group and 0.75%, 4.1%, 12%, and 50% in the control group, respectively.

Conclusion In robot-assisted surgery for pediatric scoliosis, the LC method enabled significantly lower pedicle perforation rates over the conventional method. Both the LC and conventional methods exhibited higher perforation rates for smaller pedicle diameters.

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Accurate placement of thoracolumbar pedicle screws using a handheld iOS-based navigation device

The Spine Journal 24 (2024) 1671−1677

Accurate pedicle screw placement is a challenge with reported misplacement rates of 10% and higher. A handheld navigation device (HND) may provide accuracy equal to CT-based navigation (CT-Nav) but without the cost and complexity.

OBJECTIVE: To study the accuracy of a handheld navigation device for pedicle screw placement. STUDY DESIGN: This prospective cross-sectional study with consistently applied reference standard enrolled 20 patients undergoing 92 pedicle screw placements.

PATIENTS: Patients who underwent pedicle screw placement between May 2022 and September 2022.

OUTCOME MEASURES: Pedicle screw placement accuracy per Gertzbein−Robbins.

METHODS: Once the screw pilot hole was established, the proposed trajectory of the HND was compared with that proposed by CT-Nav. Postoperatively, screw accuracy was graded according to Gertzbein−Robbins by a blinded radiologist based on CT scans. Accuracy was compared between the two systems and published control for fluoroscopy assisted and CT-Nav placement using Bayesian posterior distribution.

RESULTS: The trajectory proposed by the HND and CT-Nav were in agreement in 98.9% (95% Exact CI; 94.09%−99.97%). The HND accuracy was 98.9% with 91 screws rated “A” and 1 rated “C”. Noninferiority to fluoroscopic placement was achieved because the one-sided normalapproximation 95% CI Lower Bound (LB) of 95.3% is greater than the Performance Goal (PG) of 83.4%. Posthoc analysis demonstrated that the probability of superiority of the HND relative to the historical accuracy rate of 91.5% for fluoroscopy assisted procedures is >0.999 and that the HND’s accuracy rate is within 4.5% of CT-Nav of 95.5% is >0.999. No adverse events or intra-operative complications associated with HND were observed. There was 1 (1.1%) intra-operative repositioning and no reoperations for any reason.

CONCLUSIONS: The accuracy rate of the HND was 98.9%, and the proposed trajectory matched with CT-Nav in 98.9% of the time. This is superior to the historical published accuracy rate for fluoroscopy-assisted procedures and equivalent to the historical published accuracy rate for CT-Nav.

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Midpoint of C7 Lateral Mass Serves as an Accurate Reference Point for the Placement of T1 Pedicle Screws: An Anatomic Study

Operative Neurosurgery 26:323–329, 2024

Free-hand placement of T1 pedicle screws can often be challenging. A reliable freehand technique for placement of T1 pedicle screws can overcome some of the difficulties associated with poor fluoroscopy in this region. The purpose of this study was to propose a novel anatomic landmark for accurate identification of the T1 entry point using the midpoint of the C7 lateral mass as a reference point. Our hypothesis is that the midpoint of the C7 lateral mass is within 1–2 mm of the center of the T1 pedicle.

METHODS: Using 3-dimensional reconstruction software, the pedicle of T1 and the lateral mass of C7 were isolated to assess the location of the T1 pedicle relative to the C7 lateral mass. Specifically, the distance between the center of the T1 pedicle and the center of the C7 lateral mass was measured on 40 computed tomography scans. Furthermore, a clinical validation of this technique was performed by assessing the postoperative computed tomography scans of 53 patients undergoing cervicothoracic instrumentation. The Gertzbein and Robbins classification system was used to grade the accuracy of T1 pedicle screw placements in all patients using this technique.

RESULTS: The average horizontal deviation + SD from centers of the T1 pedicle and the C7 lateral mass was 0.398 mm ± 0.953 mm. The T1 pedicle on average was slightly medial to the center of the C7 lateral mass. A total of 98.1% of T1 pedicle screws placed in vivo using the free-hand technique were of Grade A.

CONCLUSION: In this article, we demonstrate that the center of the C7 lateral mass overlays the T1 pedicle and the optimal entry point is immediately below the midpoint of the C7 lateral mass. This approach provides a practical and accurate landmark in posterior cervicothoracic spine procedures that reduce the need for additional radiation exposure or increased operative time with image-guided techniques.

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Retrospective single-surgeon study of prone versus lateral robotic pedicle screw placement: a CT-based assessment of accuracy

J Neurosurg Spine 39:490–497, 2023

Lateral lumbar interbody fusion including anterior-to-psoas oblique lumbar interbody fusion has conventionally relied on pedicle screw placement (PSP) for construct stabilization. Single-position surgery with lumbar interbody fusion in the lateral decubitus position with concomitant PSP has been associated with increased operative efficiency. What remains unclear is the accuracy of PSP with robotic guidance when compared with the more familiar prone patient positioning. The present study aimed to compare robot-assisted screw placement accuracy between patients with instrumentation placed in the prone and lateral positions.

METHODS The authors identified all consecutive patients treated with interbody fusion and PSP in the prone or lateral position by a single surgeon between January 2019 and October 2022. All pedicle screws placed were analyzed using CT scans to determine appropriate positioning according to the Gertzbein-Robbins classification grading system (grade C or worse was considered as a radiographically significant breach). Multivariate logistic regression models were constructed to identify risk factors for the occurrence of a radiographically significant breach.

RESULTS Eighty-nine consecutive patients (690 screws) were included, of whom 46 (477 screws) were treated in the prone position and 43 (213 screws) in the lateral decubitus position. There were fewer breaches in the prone (n = 13, 2.7%) than the lateral decubitus (n = 15, 7.0%) group (p = 0.012). Nine (1.9%) radiographically significant breaches occurred in the prone group compared with 10 (4.7%) in the lateral decubitus group (p = 0.019), for a prone versus lateral decubitus PSP accuracy rate of 98.1% versus 95.3%. There were no significant differences in BMI between prone versus lateral decubitus cohorts (30.1 vs 29.6) or patients with screw breach versus those without (31.2 vs 29.5). In multivariate models, the prone position was the only significant protective factor for screw accuracy; no other significant risk factors for screw breach were identified.

CONCLUSIONS The present data suggest that pedicle screws placed with robotic assistance have higher placement accuracy in the prone position. Further studies will be needed to validate the accuracy of PSP in the lateral position as single-position surgery becomes more commonplace in the treatment of spinal disorders.

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Ideal entry point and trajectory for C2 pedicle screw placement in children: a 3D computed tomography study

European Spine Journal (2022) 31:3426–3432

Purpose To identify the ideal entry point for pediatric C2 pedicle screw and to obtain parameters of it for the indication of pediatric atlantoaxial fusion arthrodesis.

Methods The pediatric cervical CT images were reconstructed into the 3D digital models and the C2 vertebrae were separated. The location of ideal entry point and screw placement related linear and angular parameters were assessed on the 3D digital models.

Results A total of 214 pedicles from 107 C2 digital models were analyzed. The average entry point for C2 was 3.80 ± 2.78 mm medial to the lateral notch (LN) and 2.57 ± 1.70 mm superior to the LN. The average pedicle diameter (PD) was 6.02 ± 1.31 mm, and the average pedicle screw length (PSL) was 25.63 ± 3.46 mm. Statistical differences were found between different sex for PD and PSL (P < 0.05). As patient age increases, using the most lateral and inferior edge of the lateral mass as a reference marker, the entry point tends to move medial and cephalad, when using the LN as a reference marker, the entry point tends to move medial and slightly caudad. Univariate linear regression analysis suggested that these linear parameters were associated with age (P < 0.01).

Conclusion In this study, we found that the measurement results of C2 pedicle screw varied based on sex, laterality, and ages for children younger than 18 years. The entry point of the screws facilitating ideal trajectory tends to change in a linear way as a function of age. This information helps the surgeon to establish the specific anatomy related to C2 pedicle screw placement to facilitate fixation in the pediatric patients.

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Clinical accuracy and initial experience with augmented reality–assisted pedicle screw placement

J Neurosurg Spine 36:351–357, 2022

Augmented reality (AR) is a novel technology which, when applied to spine surgery, offers the potential for efficient, safe, and accurate placement of spinal instrumentation. The authors report the accuracy of the first 205 pedicle screws consecutively placed at their institution by using AR assistance with a unique head-mounted display (HMD) navigation system.

METHODS A retrospective review was performed of the first 28 consecutive patients who underwent AR-assisted pedicle screw placement in the thoracic, lumbar, and/or sacral spine at the authors’ institution. Clinical accuracy for each pedicle screw was graded using the Gertzbein-Robbins scale by an independent neuroradiologist working in a blinded fashion.

RESULTS Twenty-eight consecutive patients underwent thoracic, lumbar, or sacral pedicle screw placement with AR assistance. The median age at the time of surgery was 62.5 (IQR 13.8) years and the median body mass index was 31 (IQR 8.6) kg/m2. Indications for surgery included degenerative disease (n = 12, 43%); deformity correction (n = 12, 43%); tumor (n = 3, 11%); and trauma (n = 1, 4%). The majority of patients (n = 26, 93%) presented with low-back pain, 19 (68%) patients presented with radicular leg pain, and 10 (36%) patients had documented lower extremity weakness. A total of 205 screws were consecutively placed, with 112 (55%) placed in the lumbar spine, 67 (33%) in the thoracic spine, and 26 (13%) at S1. Screw placement accuracy was 98.5% for thoracic screws, 97.8% for lumbar/S1 screws, and 98.0% overall.

CONCLUSIONS AR depicted through a unique HMD is a novel and clinically accurate technology for the navigated insertion of pedicle screws. The authors describe the first 205 AR-assisted thoracic, lumbar, and sacral pedicle screws consecutively placed at their institution with an accuracy of 98.0% as determined by a Gertzbein-Robbins grade of A or B.

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The comparative accuracy and safety of fluoroscopic and navigation-based techniques in cervical pedicle screw fixation: systematic review and meta-analysis

J Neurosurg Spine 35:194–201, 2021

The goal of this study was to evaluate the comparative accuracy and safety of navigation-based approaches for cervical pedicle screw (CPS) placement over fluoroscopic techniques.

METHODS A systematic search of the literature published between January 2006 and December 2019 relating to CPS instrumentation and the comparative accuracy and safety of fluoroscopic and intraoperative computer-based navigation techniques was conducted. Several databases, including the Cochrane Library, PubMed, and EMBASE, were systematically searched to identify potentially eligible studies. Data relating to CPS insertion accuracy and associated complications, in particular neurovascular complications, were extrapolated from the included studies and summarized for analysis.

RESULTS A total of 17 studies were identified from the search methodology. Eleven studies evaluated CPS placement under traditional fluoroscopic guidance and 6 studies addressed outcomes following navigation-assisted placement (3D C-arm or CT-guided placement). Overall, a total of 4278 screws were placed in 1065 patients. Misplacement rates of CPS were significantly lower (p < 0.0001) in navigation-assisted techniques (12.51% [range 2.5%–20.5%]) compared to fluoroscopy-guided techniques (18.8% [range 0%–43.5%]). Fluoroscopy-guided CPS insertion was associated with a significantly higher incidence of postoperative complications relating to neurovascular injuries (p < 0.038), with a mean incidence of 1.9% compared with 0.3% in navigation-assisted techniques.

CONCLUSIONS This systematic review supports a logical conclusion that navigation-based techniques confer a statistically significantly more accurate screw placement and resultant lower complication rates.

 

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C2 medial pedicle screw: a novel “in-out-in” technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus

J Neurosurg Spine 33:281–287, 2020

The authors describe a novel “in-out-in” technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period.

METHODS Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase.

RESULTS Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients.

CONCLUSIONS This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

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Safety and accuracy of robot-assisted versus fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery

J Neurosurg Spine 30:615–622, 2019

The object of this study was to compare the safety and accuracy of pedicle screw placement using the TiRobot system versus conventional fluoroscopy in thoracolumbar spinal surgery.

METHODS Patients with degenerative or traumatic thoracolumbar spinal disorders requiring spinal instrumentation were randomly assigned to either the TiRobot-assisted group (RG) or the freehand fluoroscopy-assisted group (FG) at a 1:1 ratio. The primary outcome measure was the accuracy of screw placement according to the Gertzbein-Robbins scale; grades A and B (pedicle breach < 2 mm) were considered clinically acceptable. In the RG, discrepancies between the planned and actual screw placements were measured by merging postoperative CT images with the trajectory planning images. Secondary outcome parameters included proximal facet joint violation, duration of surgery, intraoperative blood loss, conversion to freehand approach in the RG, postoperative hospital stay, and radiation exposure.

RESULTS A total of 1116 pedicle screws were implanted in 234 patients (119 in the FG, and 115 in the RG). In the RG, 95.3% of the screws were perfectly positioned (grade A); the remaining screws were graded B (3.4%), C (0.9%), and D (0.4%). In the FG, 86.1% screws were perfectly positioned (grade A); the remaining screws were graded B (7.4%), C (4.6%), D (1.4%), and E (0.5%). The proportion of clinically acceptable screws was significantly greater in the RG than in the FG (p < 0.01). In the RG, the mean deviation was 1.5 ± 0.8 mm for each screw. The most common direction of screw deviation was lateral in the RG and medial in the FG. Two misplaced screws in the FG required revision surgery, whereas no revision was required in the RG. None of the screws in the RG violated the proximal facet joint, whereas 12 screws (2.1%) in the FG violated the proximal facet joint (p < 0.01). The RG had significantly less blood loss (186.0 ± 255.3 ml) than the FG (217.0 ± 174.3 ml; p < 0.05). There were no significant differences between the two groups in terms of surgical time and postoperative hospital stay. The mean cumulative radiation time was 81.5 ± 38.6 seconds in the RG and 71.5 ± 44.2 seconds in the FG (p = 0.07). Surgeon radiation exposure was significantly less in the RG (21.7 ± 11.5 μSv) than in the FG (70.5 ± 42.0 μSv; p < 0.01).

CONCLUSIONS TiRobot-guided pedicle screw placement is safe and useful in thoracolumbar spinal surgery. Clinical trial registration no.: NCT02890043 (clinicaltrials.gov)

 

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Use of the Airo mobile intraoperative CT system versus the O-arm for transpedicular screw fixation in the thoracic and lumbar spine

J Neurosurg Spine 29:397–406, 2018

Navigation-enabling technology such as 3D-platform (O-arm) or intraoperative mobile CT (iCT-Airo) systems for use in spinal surgery has considerably improved accuracy over that of traditional fluoroscopy-guided techniques during pedicular screw positioning. In this study, the authors compared 2 intraoperative imaging systems with navigation, available in their neurosurgical unit, in terms of the accuracy they provided for transpedicular screw fixation in the thoracic and lumbar spine.

METHODS The authors performed a retrospective analysis of clinical and surgical data of 263 consecutive patients who underwent thoracic and lumbar spine screw placement in the same center. Data on 97 patients who underwent surgery with iCT-Airo navigation (iCT-Airo group) and 166 with O-arm navigation (O-arm group) were analyzed. Most patients underwent surgery for a degenerative or traumatic condition that involved thoracic and lumbar pedicle screw fixation using an open or percutaneous technique. The primary endpoint was the proportion of patients with at least 1 screw not correctly positioned according to the last intraoperative image. Secondary endpoints were the proportion of screws that were repositioned during surgery, the proportion of patients with a postoperative complication related to screw malposition, surgical time, and radiation exposure. A blinded radiologist graded screw positions in the last intraoperative image according to the Heary classification (grade 1–3 screws were considered correctly placed).

RESULTS A total of 1361 screws placed in 97 patients in the iCT-Airo group (503 screws) and in 166 in the O-arm group (858 screws) were graded. Of those screws, 3 (0.6%) in the iCT-Airo group and 4 (0.5%) in the O-arm group were misplaced. No statistically significant difference in final accuracy between these 2 groups or in the subpopulation of patients who underwent percutaneous surgery was found. Three patients in the iCT-Airo group (3.1%, 95% CI 0%–6.9%) and 3 in the O-arm group (1.8%, 95% CI 0%–4.0%) had a misplaced screw (Heary grade 4 or 5). Seven (1.4%) screws in the iCT-Airo group and 37 (4.3%) in the O-arm group were repositioned intraoperatively (p = 0.003). One patient in the iCT-Airo group and 2 in the O-arm group experienced postoperative neurological deficits related to hardware malposition. The mean surgical times in both groups were similar (276 [iCT-Airo] and 279 [O-arm] minutes). The mean exposure to radiation in the iCT-Airo group was significantly lower than that in the O-arm group (15.82 vs 19.12 mSv, respectively; p = 0.02).

CONCLUSIONS Introduction of a mobile CT scanner reduced the rate of screw repositioning, which enhanced patient safety and diminished radiation exposure for patients, but it did not improve overall accuracy compared to that of a mobile 3D platform.

 

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Reduced Acute Care Costs With the ERAS ® Minimally Invasive Transforaminal Lumbar Interbody Fusion Compared With Conventional Minimally Invasive Transforaminal Lumbar Interbody Fusion

Neurosurgery 83:827–834, 2018

Enhancing Recovery After Surgery (ERAS (R)  ) programs have been widely adopted throughout the world, but not in spinal surgery. In this report, we review the implementation of a “fast track”surgery for lumbar fusion and its effect on acute care hospitalization costs.

OBJECTIVE: To determine if a “fast track” surgery methodology results in acute care cost savings.

METHODS: Thirty-eight consecutive ERAS patients were compared with patients undergoing conventional minimally invasive transforaminal lumbar interbody fusion. Differences between these groups included the use of endoscopic decompression, injections of liposomal bupivacaine, and performing the surgery under sedation in the ERAS R  group.

RESULTS: Patients had similar medical comorbidities (2.02 vs 2 for ERAS R  and comparator groups, respectively; P = .458). Body mass index was similar (26.5 vs 27.0; P = .329). ERAS R  patients were older (65 vs 59 yr, P= .031). Both groups had excellent clinical results with an improvement of 23% and 24%, respectively. Intraoperative blood loss was less (68±31 cc vs 231±73, P<0.001). Length of staywas also less with ERAS R  surgery, at ameanof 1.23±0.8 d vs 3.9 ± 1.1 d (P = 0.009). When comparing ERAS R  surgery to standard minimally invasive transforaminal lumbar interbody fusion, the total cost for the acute care hospitalization was $19212vs $22656, respectively(P<0.001). This reflected an average of $3444 in savings, which was a 15.2% reduction.

CONCLUSION: ERAS (R)  programs for spinal fusion surgery have the potential to reduce the costs of acute care. This is made possible by leveraging less invasive interventions to minimize soft tissue damage.

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Navigation and Robotics in Spinal Surgery: Where Are We Now?

Neurosurgery 80:S86–S99, 2017

Spine surgery has experienced much technological innovation over the past several decades. The field has seen advancements in operative techniques, implants and biologics, and equipment such as computer-assisted navigation and surgical robotics.

With the arrival of real-time image guidance and navigation capabilities along with the computing ability to process and reconstruct these data into an interactive three-dimensional spinal “map”, so too have the applications of surgical robotic technology.

While spinal robotics and navigation represent promising potential for improving modern spinal surgery, it remains paramount to demonstrate its superiority as compared to traditional techniques prior to assimilation of its use amongst surgeons.

The applications for intraoperative navigation and image-guided robotics have expanded to surgical resection of spinal column and intradural tumors, revision procedures on arthrodesed spines, and deformity cases with distorted anatomy.

Additionally, these platforms may mitigate much of the harmful radiation exposure in minimally invasive surgery to which the patient, surgeon, and ancillary operating room staff are subjected. Spine surgery relies upon meticulous fine motor skills to manipulate neural elements and a steady hand while doing so, often exploiting small working corridors utilizing exposures that minimize collateral damage.

Additionally, the procedures may be long and arduous, predisposing the surgeon to both mental and physical fatigue. In light of these characteristics, spine surgery may actually be an ideal candidate for the integration of navigation and robotic-assisted procedures.

With this paper, we aim to critically evaluate the current literature and explore the options available for intraoperative navigation and robotic-assisted spine surgery.

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Treatment of unstable thoracolumbar junction fractures

treatment-of-unstable-thoracolumbar-junction-fractures

Acta Neurochir (2016) 158:1883–1889

The surgical management of thoracolumbar burst fractures frequently involves posterior pedicle screw fixation. However, the application of short- or long-segment instrumentation is still controversial. The aim of this study was to compare the outcome of the short-segment fixation with inclusion of the fracture level (SSFIFL) versus the traditional long-segment fixation (LSF) for the treatment of unstable thoracolumbar junction fractures.

Methods From December 2009 to February 2014, 60 patients with unstable thoracolumbar junction fractures (T11-L2) were divided into two groups according to the number of instrumented levels. Group 1 included 30 patients treated by SSFIFL (six-screw construct including the fracture level). Group 2 included 30 patients treated by LSF (eight-screw construct excluding the fracture level). Local kyphosis angle (LKA), anterior body height (ABH), posterior body height (PBH), ABH/PBH ratio of fractured vertebra, and Asia Scale Impairment Scale were evaluated.

Results The two groups were similar in regard to age, sex, trauma etiology, fracture level, fracture type, neurologic status, pre-operative LKA, ABH, PBH, and ABH/PBH ratio and follow-up (p > 0.05). Reduction of post-traumatic kyphosis (assessed with LKA) and restoration of fracture-induced wedge shape of the vertebral body (assessed with ABH, PBH, and ABH/PBH ratio) at post-operative period were not significantly different between group 1 and group 2 (p = 0.234; p = 0.754). There was no significant difference between the two groups in term of correction loss at the last follow-up too (LKA was 15.97° ± 5.62° for SSFIFL and 17.76° ± 11.22° for LSF [p = 0.427]). Neurological outcome was similar in both groups.

Conclusions Inclusion of fracture level in a short-segment fixation for a thoracolumbar junction fractures results in a kyphosis correction and in a maintenance of the sagittal alignment similar to a long-segment instrumentation. Finally, this technique allowed us to save two or more segments of vertebral motion.

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Unskilled unawareness and the learning curve in robotic spine surgery

SpineAssist™ robot system

Acta Neurochir (2015) 157:1819–1823

Robotic assistance for the placement of pedicle screws has been established as a safe technique. Nonetheless rare instances of screw misplacement have been reported.The aim of the present retrospective study is to assess whether experience and time affect the accuracy of screws placed with the help of the SpineAssist™ robot system.

Methods Postoperative computed tomography (CT) scans of 258 patients requiring thoracolumbar pedicle screw instrumentation from 2008 to 2013 were reviewed. Overall, 13 surgeons performed the surgeries. A pedicle breach of >3 mm was graded as a misplacement. Surgeons were dichotomised into an early and experienced period in increments of five surgeries.

Results In 258 surgeries, 1,265 pedicle screws were placed with the aid of the robot system. Overall, 1,217 screws (96.2 %) were graded as acceptable. When displayed by surgeon, the development of percent misplacement rates peaked between 5 and 25 surgeries in 12 of 13 surgeons. The overall misplacement rate in the first five surgeries was 2.4%(6/245). The misplacement rate rose to 6.3 % between 11 and 15 surgeries (10/158; p=0.20), and reached a significant peak between 16 and 20 surgeries with a rate of 7.1 % (8/112; p= 0.03). Afterwards, misplacement rates declined.

Conclusions A major peak in screw inaccuracies occurred between cases 10 and 20, and a second, smaller one at about 40 surgeries. One potential explanation could be a transition from decreased supervision (unskilled but aware) to increased confidence of a surgeon (unskilled but unaware) who adopts this new technique prior to mastering it (skilled). We therefore advocate ensuring competent supervision for new surgeons at least during the first 25 procedures of robotic spine surgery to optimise the accuracy of robot-assisted pedicle screws.

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Safety and accuracy of robot-assisted versus fluoroscopy-guided pedicle screw insertion for degenerative diseases of the lumbar spine


Robot-assisted spine surgery

J Neurosurg Spine 20:636–643, 2014

Recent years have been marked by efforts to improve the quality and safety of pedicle screw placement in spinal instrumentation. The aim of the present study is to compare the accuracy of the SpineAssist robot system with conventional fluoroscopy-guided pedicle screw placement.

Methods. Ninety-five patients suffering from degenerative disease and requiring elective lumbar instrumentation were included in the study. The robot cohort (Group I; 55 patients, 244 screws) consisted of an initial open robot-assisted subgroup (Subgroup IA; 17 patients, 83 screws) and a percutaneous cohort (Subgroup IB, 38 patients, 161 screws). In these groups, pedicle screws were placed under robotic guidance and lateral fluoroscopic control. In the fluoroscopy-guided cohort (Group II; 40 patients, 163 screws) screws were inserted using anatomical landmarks and lateral fluoroscopic guidance. The primary outcome measure was accuracy of screw placement on the Gertzbein-Robbins scale (Grade A to E and R [revised]). Secondary parameters were duration of surgery, blood loss, cumulative morphine, and length of stay.

Results. In the robot group (Group I), a perfect trajectory (A) was observed in 204 screws (83.6%). The remaining screws were graded B (n = 19 [7.8%]), C (n = 9 [3.7%]), D (n = 4 [1.6%]), E (n = 2 [0.8%]), and R ( n = 6 [2.5%]). In the fluoroscopy-guided group (Group II), a completely intrapedicular course graded A was found in 79.8% (n = 130). The remaining screws were graded B (n = 12 [7.4%]), C (n = 10 [6.1%]), D (n = 6 [3.7%]), and E (n = 5 [3.1%]). The comparison of “clinically acceptable” (that is, A and B screws) was neither different between groups (I vs II [p = 0.19]) nor subgroups (Subgroup IA vs IB [p = 0.81]; Subgroup IA vs Group II [p = 0.53]; Subgroup IB vs Group II [p = 0.20]). Blood loss was lower in the robot-assisted group than in the fluoroscopy-guided group, while duration of surgery, length of stay, and cumulative morphine dose were not statistically different.

Conclusions. Robot-guided pedicle screw placement is a safe and useful tool for assisting spine surgeons in degenerative spine cases. Nonetheless, technical difficulties remain and fluoroscopy backup is advocated.

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Anterior Cervical Reconstruction With Pedicle Screws After a 4-Level Corpectomy

Spine 2012 ; 37 : E927 – E930

Anterior reconstruction after multilevel corpectomy is a challenging technique, and there are many reports on its complications. Graft dislodgement is one of the major complications after long cervical fusion. The main cause of failure seems to be a lack of stability in the conventional reconstruction technique. However, pedicle screws for posterior cervical reconstruction show remarkable stability. We describe a new technique of anterior cervical reconstruction with pedicle screws and fibular strut grafting.

Methods. Seven patients with multilevel cervical myelopathy were treated with this new reconstruction technique after a 4-level corpectomy. We describe this new technique and review the patients’ clinical history, results of radiographical imaging, and outcomes. Clinical outcomes were assessed preoperatively and at 3 months postoperatively. Postoperative radiographs were assessed 3 months and 6 months postoperatively.

Results. The mean operative time was 182 minutes and the mean blood loss was 271 mL. The average Japanese Orthopaedic Association score for cervical myelopathy improved from 11.5 points preoperatively to 14.5 points 3 months postoperatively. No patients experienced major complications, such as neurological deterioration, infection, or massive blood loss. There was no case of reconstruction failure, graft dislodgement, migration, or screw displacement.

Conclusion. To our knowledge, this is the first description of an anterior cervical reconstruction approach, using pedicle screws and fibular strut grafting after a 4-level corpectomy. It is likely that this technique will result in better clinical outcomes with fewer complications in the treatment of patients with multilevel cervical myelopathy.

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Clinical Assessment of Percutaneous Lumbar Pedicle Screw Placement Using the O-Arm Multidimensional Surgical Imaging System

Neurosurgery 70:990–995, 2012 DOI: 10.1227/NEU.0b013e318237a829

Increasing popularity of minimally invasive surgery for lumbar fusion has led to dependence upon intraoperative fluoroscopy for pedicle screw placement, because limited muscle dissection does not expose the bony anatomy necessary for traditional, freehand techniques nor for registration steps in image-guidance techniques. This has raised concerns about cumulative radiation exposure for both surgeon and operating room staff. The recent introduction of the O-arm Multidimensional Surgical Imaging System allows for percutaneous placement of pedicle screws, but there is limited clinical experience with the technique and data examining its accuracy.

OBJECTIVE: We present the first large clinical series of percutaneous screw placement using navigation of O-arm imaging and compare the results with the fluoroscopyguided method.

METHODS: A retrospective review of a 24-month period identified patients undergoing minimally invasive lumbar interbody fusion. The O-arm was introduced in the middle of this period and was used for all subsequent patients. Accuracy of screw placement was assessed by examination of axial computed tomography or O-arm scans.

RESULTS: The fluoroscopy group included 141 screws in 42 patients, and the O-arm group included 205 screws in 52 patients. The perforation rate was 12.8% in the fluoroscopy group and 3% in the O-arm group (P < .001). Single-level O-arm procedures took a mean 200 (153-241) minutes, whereas fluoroscopy took 221 (178-302) minutes (P < .03).

CONCLUSION: Percutaneous pedicle screw placement with the O-arm Multidimensional Intraoperative Imaging System is a safe and effective technique and provided improved overall accuracy and reduced operative time compared with conventional fluoroscopic techniques.

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Accuracy of Image-Guided Pedicle Screw Placement Using Intraoperative Computed Tomography- Based Navigation With Automated Referencing. Part II: Thoracolumbar Spine

Neurosurgery 69:1307–1316, 2011 DOI: 10.1227/NEU.0b013e31822ba190

Image-guided spinal instrumentation may reduce complications in spinal instrumentation.

OBJECTIVE: To assess accuracy, time efficiency, and staff radiation exposure during thoracolumbar screw instrumentation guided by intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS: In 55 patients treated for idiopathic and degenerative deformities, 826 screws were inserted in the thoracic (T2–T12; n = 243) and lumbosacral (L1–S1; n = 545) spine, as well as ilium (n = 38) guided by iCT-N. Up to 17 segments were instrumented following a single automated registration sequence with the dynamic reference arc (DRA) uniformly attached to L5. Accuracy of iCT-N was assessed by calculating angular deviations between individual navigated tool trajectories and final implant positions. Final screw positions were also graded according to established classification systems. Clinical and radiological outcome was assessed at 12 to 14 months.

RESULTS: Additional intraoperative fluoroscopy was unnecessary, eliminating staff radiation exposure. Unisegmental K-wire insertion required 4.6 6 2.9 minutes. Of the thoracic pedicle screws 98.4% were assigned grades I to III according to the Heary classification, with 1.6% grade IV placement. In the lumbar spine, 94.4% of screws were completely contained (Gertzbein classification grade 0), 4.6% displayed minor pedicle breaches ,2 mm(grade 1), and 1% of lumbar screws deviated by.2 to,4 mm (grade 2). The accuracy of iCT-N progressively deteriorates with increasing distance from the DRA, but allows safe instrumentation of up to 12 segments.

CONCLUSION: iCT-N using automated referencing allows for safe, highly accurate multilevel instrumentation of the entire thoracolumbosacral spine and ilium, rendering additional intraoperative imaging dispensable. In addition, automated registration is time-efficient and significantly reduces the need for re-registration in multilevel surgery.

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Accuracy of Image-Guided Pedicle Screw Placement Using Intraoperative Computed Tomography- Based Navigation With Automated Referencing, Part I: Cervicothoracic Spine

Neurosurgery 69:782–795, 2011 DOI: 10.1227/NEU.0b013e318222ae16

Image-guided spinal instrumentation reduces the incidence of implant misplacement.

OBJECTIVE: To assess the accuracy of intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS: In 35 patients (age range, 18-87 years), a total of 248 pedicle screws were placed in the cervical (C1-C7) and upper and midthoracic (T1-T8) spine. An automated iCT registration sequence was used for multisegmental instrumentation, with the reference frame fixed to either a Mayfield head clamp and/or the most distal spinous process within the instrumentation. Pediculation was performed with navigated drill guides or Jamshidi cannulas. The angular deviation between navigated tool trajectory and final implant positions (evaluated on postinstrumentation iCT or postoperative CT scans) was calculated to assess the accuracy of iCT-N. Final screw positions were also graded according to established classification systems. Mean follow-up was 16.7 months.

RESULTS: Clinically significant screw misplacement or iCT-N failure mandating conversion to conventional technique did not occur. A total of 71.4% of patients self-rated their outcome as excellent or good at 12 months; 99.3% of cervical screws were compliant with Neo classification grades 0 and 1 (grade 2, 0.7%), and neurovascular injury did not occur. In addition, 97.8% of thoracic pedicle screws were assigned grades I to III of the Heary classification, with 2.2% grade IV placement. Accuracy of iCT-N progressively deteriorated with increasing distance from the spinal reference clamp but allowed safe instrumentation of up to 10 segments.

CONCLUSION: Image-guided spinal instrumentation using iCT-N with automated referencing allows safe, highly accurate multilevel instrumentation of the cervical and upper and midthoracic spine. In addition, iCT-N significantly reduces the need for reregistration in multilevel surgery.

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