Pedicle Screw Misplacement Research Articles

P117. Navigated robotic assistance improves pedicle screw accuracy in minimally invasive surgery of the thoracolumbar spine: 341 patients in a single institution

BACKGROUND CONTEXT As the field of robot-assisted spine surgery continues to progress and grow, radiographic evaluation of pedicle screw accuracy in a surgical setting is of high interest. Advances in medical imaging and technology have improved pedicle screw placement accuracy, from fluoroscope-guided placement to computer-aided navigation. PURPOSE The purpose of this study is to assess the pedicle screw accuracy of 341 consecutive cases in which navigated robotic assistance was used in a private practice clinical setting. STUDY DESIGN/SETTING Retrospective chart review. PATIENT SAMPLE A total of 341 consecutive patients. OUTCOME MEASURES Screw accuracy, screw offset, complications. METHODS A retrospective, Institutional Review Board-exempt review of 341 navigated robot-assisted spine surgery cases was performed at a single private institution. Radiographic evaluation of screw tip and screw tail offset distance and angulation from preoperative plan to actual final placement based on intraoperative computerized tomography (CT) images was analyzed and calculated. Additionally, pedicle screw malposition, reposition and return to operating room (OR) rates were reviewed. A CT-based Gertzbein and Robbins System (GRS) was used to classify pedicle screw accuracy. The GRS system classifies screws with the rating of A or B as accurate, and C, D, or E as inaccurate placement. The accuracy percentage was calculated by dividing the number of accurate screws placed with robotic navigation by the total cohort. RESULTS In the 341 cases analyzed, 1,929 thoracolumbar pedicle screws were placed. Thirty-one screws (6 patients) deviated from robot use due to surgeon discretion. Of the 1,929 pedicle screws inserted by navigated robotic guidance, only .005% (9/1929) were repositioned intraoperatively. The average age was 66.8 years, and 48% of the patients were male. Average body mass index was 29.31 kg/m2. The majority of the surgical diagnoses were degenerative disc disease (248) and adjacent segment disease (72). The average offset from preoperative plan to actual final placement was 1.7±1.3mm from the tip, 1.6±1.0mm from the tail, and 2.0±1.4° of angulation. Based on the GRS CT-based grading, 97.8% (1,886/1,928) screws were graded A or B, 2.0% (40/1,928) screws were graded C, and 0.2% (3/1,928) screws were graded D. A total of three complications that required a return to the OR were reported: interbody removal, deep wound infection, and wound vacuum-assisted closure. None were related to robotic guidance or pedicle screws. CONCLUSIONS This study demonstrated a high level of accuracy (97.8%) in the clinical use of navigated, robot-assisted surgery in 341 cases. FDA DEVICE/DRUG STATUS ExcelsiusGPS (Globus Medical) (Approved for this indication)

110. Clinical significance of lateral pedicle screw malposition in the lumbar spine

BACKGROUND CONTEXT The risks of pedicle screw malposition have largely focused on medial malposition and neurological injury. Although lateral malposition is considered relatively benign, no previously reported study has focused specifically on clinical outcomes associated with lateral screw malposition. We hypothesize that lateral pedicle screw breach has a negative effect on fusion rates and clinical outcomes following elective single-level posterior lumbar fusion (PLF). PURPOSE Not applicable. STUDY DESIGN/SETTING Not applicable. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable. METHODS Retrospective review of a prospective multicenter cohort of patients undergoing single-level instrumented PLF with local autograft bone for degenerative disease. Twelve-month postoperative computed tomography (CT) was reviewed for breach direction, severity of screw-associated pedicle breach and fusion status. Patients with lateral breach were compared to patients with no breach. Patients with nonlateral screw malposition were excluded. Outcomes measures included Oswestry Disability Index (ODI), Numerical Pain Rating Scale (NPRS) for back pain, and SF-36 physical function. Improvement in back pain was defined as a ≥35% change (minimal clinically important difference) at follow-up. Outcomes were analyzed using multivariable linear and logistic regression and were adjusted for age, procedure, level, and/or baseline pain score. RESULTS A total of 154 patients underwent 12-month postoperative CT. Forty-five patients (30.6%) demonstrated one or more lateral breaches and were compared to 102 patients with no breach. After adjusting for baseline scores and fusion level, patients with one or more breaches had, on average, ODI score decreases that were 2.44 points less (p=0.454) and SF-36 score increases that were 2.04 points less (p=0.040) than patients with no lateral breach. Breach was also associated with a large decrease in the odds of achieving back pain relief (OR=0.37, 95%CI: 0.15, 0.91) after adjusting for baseline NPRS. There was no observed effect of breach on the odds of non-union (multiple breaches OR=1.97, 95% CI: 0.66, 5.97). CONCLUSIONS The current study did not observe an association between laterally malpositioned pedicle screws and nonunion or disability scores. However, these results are consistent with a modest negative effect on physical functioning scores and self-reported back pain. This suggests that surgeons may anticipate poorer clinical outcomes among patients with laterally malpositioned screws. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Neurological events due to pedicle screw malpositioning with lateral fluoroscopy-guided pedicle screw insertion.

The risk of novel postoperative neurological events due to pedicle screw malpositioning in lumbar fusion surgery is minimized by using one of the several image-guided techniques for pedicle screw insertion. These techniques for guided screw insertion range from intraoperative fluoroscopy to intraoperative navigation. A practical technique consists of anatomical identification of the screw entry point followed by lateral fluoroscopy used for guidance during insertion of the screw. This technique is available in most clinics and is less expensive than intraoperative navigation. However, the safety of lateral fluoroscopy-guided pedicle screw placement with regard to novel postoperative neurological events due to screw malposition has been addressed only rarely in the literature. In this study the authors aimed to determine the rate of novel postoperative neurological events due to intraoperative and postoperatively established screw malpositioning during lateral fluoroscopy-assisted screw insertion. Included patients underwent lateral fluoroscopy-assisted lumbosacral screw insertion between January 2012 and August 2017. The occurrence of novel postoperative neurological events was analyzed from patient files. In case of an event, surgical reports were screened for the occurrence of intraoperative screw malposition. Furthermore, postoperative CT scans were analyzed to identify and describe possible screw malposition. In total, 246 patients with 1079 screws were included. Novel postoperative neurological events were present in 36 patients (14.6%). In 8 of these 36 patients (3.25% of the total study population), the neurological events could be directly attributed to screw malposition. Screw malpositioning was caused either by problematic screw insertion with immediate screw correction (4 patients) or by malpositioned screws for which the malposition was established postoperatively using CT scans (4 patients). Three patients with screw malposition underwent revision surgery without subsequent symptom relief. Lateral fluoroscopy-assisted lumbosacral screw placement results in low rates of novel postoperative neurological events caused by screw malposition. In the majority of patients suffering from novel postoperative neurological events, these events could not be attributed to screw malpositioning, but rather were due to postoperative neurapraxia of peripheral nerves, neuropathy, or intraoperative traction of nerve roots.

Transabdominal Motor Action Potential Monitoring of Pedicle Screw Placement During Minimally Invasive Spinal Procedures: A Case Study.

Precise pedicle screw placement is a critical skill during minimally invasive spinal surgeries but can pose various challenges. Techniques such as electromyography (EMG) have been traditionally utilized for this purpose but have several shortcomings. Transabdominal motor action potential (TaMAP) has been examined as a possible effective neuromonitoring alternative and is hypothesized to provide important data on symptomatic malpositioned pedicle screws. The current study seeks to determine whether TaMAP may be an advantageous technique in the neuromonitoring of percutaneous pedicle screw placement during minimally invasive spinal procedures. The methodology involved recording TaMAP signals at the outset and the conclusion of spinal surgical procedures in human participants, for which comparisons were made of pre- and post-operative data. Results revealed that TaMAP signals remained stable during accurate pedicle screw placement and degraded during a case of inaccurate placement, for which initial misplaced hardware altered the depolarization threshold and resulted in substantial signal alteration. These results suggest that TaMAP, which is stable, repeatable, and reflects real-time information, can potentially be used as a reliable and more precise indication of accuracy in pedicle screw placement during spinal surgeries. This is the first TaMAP study conducted in human participants.

Incidence of pedicle breach following open and minimally invasive spinal instrumentation: A postoperative CT analysis of 513 pedicle screws applied under fluoroscopic guidance.

BackgroundEven though pedicle screw application is a common procedure, and in-spite of spine surgeons being proficient with the technique, mal-positioning of pedicle screws can still occur. We intend to determine by postoperative CT analysis, the incidence of pedicle screw breach in the thoracolumbar spine despite satisfactory intraoperative placement confirmed by fluoroscopy.Materials and methodsConsecutive patients diagnosed with thoracolumbar fractures who underwent open or minimally invasive posterior stabilization under fluoroscopic guidance were retrospectively reviewed. Postoperative CT scans of patients were analysed to determine the incidence of pedicle breach despite satisfactory intraoperative placement, and also to determine the factors that can predict a breach during intraoperative assessment.ResultsA total of 61 patients with 513 thoracolumbar pedicle screws were available for analysis. Based on our postoperative CT assessment, 28 screws (5.5%; 18 thoracic screws; 10 lumbar screws) had breached the pedicle. There were 14 minor (<3 mm) and 14 major (≥3 mm) breaches. The minimally invasive technique had a significantly lower breach rate compared to open surgery (1.9% vs. 7.9%). By retrospectively analysing the intra-operative fluoroscopic images, we determined certain parameters that could predict a breach during surgery.ConclusionPedicle breaches can still be present despite satisfactory placement of screws visualized intra-operatively. A medial breach is most likely when the length of the pedicle screw spans only up to 50% of the vertebral body as seen on the lateral view but the pedicle screw tip has already transgressed the midline as seen on an AP view. A lateral breach is likely when the tip of the pedicle screw is overlapped by the screw head or is only minimally visualized on an AP view.

The \u201cslide technique\u201d\u2014a novel free-hand method of subaxial cervical pedicle screw placement

BackgroundCervical Pedicle Screw (CPS) placement is a challenging work due to the high risk of neurovascular complications. Although there have been several different free-hand or navigation assisted techniques for CPS placement, perforations may occur during screw insertion, especially lateral perforation. The objective of this manuscript is to describe a novel free-hand technique for subaxial CPS placement (C3–C7) and to evaluate if it decreases the chances of perforation.MethodsThirty-two patients undergoing surgery with CPS instrumentation (C3–C7) at our institute between June 2017 and December 2018 were included in this study. All the patients had cervical trauma, and pedicle screw insertion was performed according to the free-hand “slide technique”. The lamina, lateral mass and facet joint of the target area were exposed and the optimal entry point was found on the lateral mass posterior surface. A pedicular probe was then inserted and gently advanced. During the pedicle probe insertion, the cortex of the medial margin of the pedicle acted as a slide to permit the safe insertion of the screw. If the pedicle screw pathway was intact, the screw of the appropriate size was carefully placed. Three-dimensional (3D) CT imaging reconstruction was performed in all the patients after surgery, and screw perforations were graded with the Gertzbein-Robbins classification.ResultsThirty-two patients who met the inclusion criteria were included in this study. A total of 257 CPSs (C3–7) were inserted, of which 41 CPSs were in C3, 61 CPSs were in C4, 55 CPSs were in C5, 53 CPSs were in C6, and 47 CPSs were in C7. The diameter and length of CPSs were 3.5 mm and 22–26 mm respectively. According to the Gertzbein-Robbins classification, grade 0, 231 screws; grade 1, 19 screws; and grade 2, 7 screws. No neurovascular complications occurred stemming from malpositioning of pedicle screws. Among perforated screws (26 screws), there were 16 lateral perforations, 5 medical perforations, and 4 inferior perforations.ConclusionsThe initial usage result shows the “slide technique” is a safe, effective and cost-effective technique for pedicle screw placement in the cervical spine. This is the first report of such a technique, and further studies are needed.

The influence of comorbidity on the results of surgical treatment of elderly and senile patients with degenerative lumbar spinal stenosis

Objective. To analyze the influence of somatic comorbidity on the results of surgical treatment of elderly and senile patients with degenerative lumbar spinal stenosis.Material and Methods. The study design corresponds to a single-center non-randomized retrospective cohort study with level 3 evidence (OCEBM Levels of Evidence Working Group. The Oxford 2011 Levels of Evidence). The influence of somatic comorbidity on quality of life after surgery for degenerative lumbar spinal stenosis was analyzed in 962 patients 60–85 years old. Analysis and evaluation of the results of the study was carried out in two groups of patients with radicular compression syndrome: Group 1 (less than 5 points according to White – Panjabi criteria) included 625 (65%) patients, and Group 2 (5 or more points according to White – Panjabi criteria) – 337 (35%) patients.Results. Body mass index of patients in Group 1 was statistically significantly lower than in Group 2. Repeated surgical interventions performed during the first year after the primary operation were statistically significantly more frequent in Group 1, and those performed after 3–4 years were more frequent in Group 2 (BMI ≥ 30) due to the development of adjacent level disease. In obese patients, the duration of surgery, blood loss and postoperative hospital stay are statistically significantly increased. One year after surgery, a statistically significant negative effect of increase in BMI on the parameters of back pain, lower limb pain, functional adaptation, and quality of life was revealed in both groups of patients. No association of obesity and complication rates was noted. In Group 2, the incidence of adjacent level disease 2–5 years after the primary operation was higher in patients with BMI ≥ 30 compared with patients with BMI &lt; 30 and with patients in Group 1. It was found that somatic comorbidity and the age of patients statistically significantly prolonged postoperative hospital stay in Group 1 and did not affect its duration in Group 2. No effect of the comorbidity index on the quality of life was noted. Osteoporosis was statistically significantly associated with an increase in the frequency of technical complications during surgery (malposition of pedicle screws, cage migration, and damage to the vertebral endplates).Conclusion. Obesity is statistically significantly associated with an increase in postoperative hospital stay, surgery duration and blood loss, and is a predictor of the development of instability of the spinal motion segment and adjacent level disease. Obese patients have higher levels of back and lower limb pain and worse quality of life parameters after surgical interventions than patients with normal body weight. When using minimally invasive technologies in the surgical treatment of degenerative lumbar spine pathology, the number of complications in obese patients is not higher than in patients with normal body weight. The effect of comorbidity on the results of minimally invasive surgery for degenerative lumbar pathology was not detected. Osteoporosis affects the frequency of technical complications during surgery.

Radiographic findings for surgery-related complications after pedicle subtraction osteotomy for thoracolumbar kyphosis in 230 patients with ankylosing spondylitis.

The purpose of this study was to investigate the rate of and the risk factors for surgery-related complications demonstrated on radiography after pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis in patients with ankylosing spondylitis (AS). The authors retrospectively reviewed the medical records of 230 consecutive patients with thoracolumbar kyphosis due to AS who had undergone 1-level PSO at a single institution in the period from 2010 to 2017. The causes of surgery-related complications were divided into two types: surgical/technical failure and mechanical failure. The patients consisted of 20 women and 210 men, with an average age of 43.4 years. The average follow-up period was 39.0 months. The preoperative sagittal vertical axis was 18.5 ± 69.3 cm, which improved to 4.9 ± 4.6 cm after PSO. Of the 77 patients (33.5%) who experienced minor or major surgery-related complications, 56 had complications related to surgical/technical failure (overall incidence 24.3%) and 21 had complications related to mechanical failure (overall incidence 9.1%). Fourteen patients (6.1%) underwent reoperation. However, among the 77 patients with complications, the rate of revision surgery was 18.2%. The most common radiological complications were as follows: sagittal translation in 24 patients, coronal imbalance in 20, under-correction in 8, delayed union in 8, and distal junctional failure and kyphosis in 8. The most common causes of reoperation were coronal imbalance in 4 patients, symptomatic malposition of pedicle screws in 3, and distal junctional failure in 3. Delayed union was statistically correlated with posterior sagittal translation (p = 0.007). PSO can provide acceptable radiographic outcomes for the correction of thoracolumbar kyphosis in patients with AS. However, a high incidence of surgery-related complications related to mechanical failure and surgical technique can develop. Thorough radiographic investigation before and during surgery is needed to determine whether complete ossification occurs along the anterior and posterior longitudinal ligaments of the spine.

Intraoperative Radiation Exposure for Patients with Double-Curve Idiopathic Scoliosis in Freehand-Technique in Comparison to Fluoroscopic- and CT-Based Navigation.

In the operative treatment of idiopathic scoliosis, posterior correction and fusion in freehand technique is a proven procedure and is frequently performed. Malpositioned pedicle screws can result in serious neurovascular complications. Intraoperative fluoroscopy and neurophysiological measurements are performed to ensure the correct position of pedicle screws. Newer procedures with fluoroscopic- and computertomographic-assisted navigation are advertised as less dangerous and with a more accurate screw position. Is the freehand technique used in the surgical treatment of idiopathic scoliosis safer than other methods with regard to complications caused by screw malposition and intraoperative radiation exposure? Register data of 34 consecutive idiopathic scoliosis patients with two structural curves (Lenke 3 and 6) were collected prospectively in our scoliosis center and were retrospectively analyzed. The following parameters were evaluated: total radiation product, time of fluoroscopy, number of fused segments, time of operation, blood loss, screw-related complications and number of instrumented pedicle screws. All values were given as mean ± standard deviation and statistically analyzed. Finally, our data were compared on accuracy of screw placement and radiation exposure to data from literature with screw placement under navigation. Average age at the time of surgery was 23.6 ± 12 years. The average thoracic curve was 69.2 ± 14.2° preoperatively and 21.7 ± 12.8° postoperatively (correction 69.9%), the average lumbar curve was 64.3° ± 10.8° preoperatively and corrected to 15.6 ± 10.4° postoperatively (correction 76.2%). The total radiation product per patient was 145.7 ± 86.1 cGy*cm², the time of fluoroscopy 31.7 ± 23.5 s (11.5 segments), the time of operation 267.2 ± 64.1 min and the blood loss 700.4 ± 522.3 ml. A total of 803 pedicle screws were placed. No screw-associated complications were detected in the entire collective. The comparison of our data with freehand placement of pedicle screws to literature data showed a noticeable higher radiation exposure for the patient during fluoroscopic- and computertomographic-assisted navigation. The results showed that positioning of pedicle screws with freehand technique in patients with idiopathic scoliosis is accompanied with considerably lower intraoperative radiation exposure compared to fluoroscopic- or computertomographic-assisted navigation. An increased radiation exposure of these typically young patients is associated with an increased long-term risk for the occurrence of radiation-induced malignant diseases. With appropriate surgical experience, placement of pedicle screws in freehand technique is safe and effective and with similar accuracy than screws placed under navigation, but produces significantly less radiation exposure to the patients.

Is the Risk of Aorta Injury or Impingement Higher During Correction Surgery in Patients with Severe and Rigid Scoliosis?

To evaluate the position of the aorta relative to the spine and the risk of aortic injury during correction surgery in patients with idiopathic severe and rigid scoliosis (main curve Cobb angle >90° and flexibility <30%). Twenty-seven patients with severe right thoracic/thoracolumbar scoliosis were recruited. The entry point-aorta distance (EAD), the left pedicle-aorta angle (α), the left aorta angle (β), and the vertebral rotation angle (γ) were measured from 4 vertebrae above (A4) to 4 below (B4) the apical vertebra (Apex) to quantify the spatial relationship between aorta and spine. We simulated the pedicle screw misplacement with variable direction error, length, and diameter to analyze the potential risk of aortic injury. The aorta shifted laterally and posteriorly as it descended from A4 and moved back medially and anteriorly from Apex. The potential risk of aortic injury increased with the augment of direction error and/or length of the screw, but the tendency was not significant with the augment of diameter. The risk peaked at A4, A3, and B2, when the screw length was 40 mm and diameter was 5.0 mm, and the direction error was 30°, whereas the risk was lowest at the apical level 14.3% (0%-40.7%) in any scenarios. In patients with severe and rigid scoliosis, the aorta shifted more laterally and posteriorly, and the injury risk was lower at the apical level, compared with moderate scoliosis. Most potential risks can be minimized by careful preoperative planning and the assistance of intraoperative navigation or robotics.

Percutaneous Transforaminal Endoscopic Lumbar Interbody Fusion for Degenerative Lumbar Diseases: A Consecutive Case Series with Mean 2-Year Follow-Up

Conventional open surgical procedures may cause massive dissections of the spine, higher perioperative complications, prolonged hospitalization, protracted rehabilitation programs and recovery. Percutaneous endoscopic lumbar interbody fusion (PELIF) is an evolving treatment option. To present the detailed procedure and preliminary clinical and radiologic results of PELIF for degenerative lumbar diseases. A retrospective cohort study. A university affiliated tertiary hospital. The medical records of patients with degenerative lumbar diseases who underwent PELIF between January 2016 and December 2017 were retrospectively reviewed. Surgical level, surgical time, blood loss, hospital length of stay, and perioperative complications were discussed. Patients were also evaluated for pain by the Visual Analog Scale (VAS), and functional assessment by the Oswestry Disability Index (ODI) and the 36-Item Short Form Health Survey (SF-36), including Physical Component Summary (PCS) and Mental Component Summary (MCS) preoperatively, postoperatively, and during the follow-up period. Thirty-nine consecutive patients (25 men and 14 women) with a mean age of 59.0 years (range, 39-77 years) were enrolled. The average surgical time was 213.8 ± 31.7 minutes (range, 185-324 minutes). Mean estimated blood loss was 25.0 ± 12.6 mL (range, 15-50 mL). At the latest follow-up visit, the VAS scores for back pain, leg pain, ODI, and SF-36 (MCS/PCS) scores improved 89.5%, 95.0%, 71.2%, and 37.5%/58%, respectively. Reoperations were performed in one patient for residual disc mass and one for misplacement of pedicle screw. Fusion was achieved in all patients. The presented results are preliminary and should be interpreted taking the limitations into account, including nonrandomized design, relatively small sample size, and less intensive follow-up period. The presented PELIF technique seems to be a promising surgical alternative for the treatment of patients with specific degenerative lumbar diseases. Randomized studies with larger sample size and long-term follow-up duration are needed to validate the superiorities of this versatile surgery. Endoscopic, minimally invasive spine surgery, lumbar interbody fusion, disc herniation, spondylolisthesis.

Accuracy of pedicle screw insertion for unilateral open transforaminal lumbar interbody fusion: a side-by-side comparison of percutaneous and conventional open techniques in the same patients

BackgroundThe aim of the study was to compare the accuracy of percutaneous pedicle screw (PPS) insertion (P-side) with that of conventional open screw insertion (O-side) during unilateral open transforaminal lumbar interbody fusion (TLIF) in the same patients. We also sought to determine the incidence of pedicle screw misplacement and to identify relevant risk factors.MethodsThe study was a retrospective analysis of prospectively collected data for 766 pedicle screws placed in 181 consecutive patients who underwent a unilateral open-TLIF procedure in the lumbosacral spine. Our minimally invasive TLIF was performed by unilateral open freehand insertion of pedicle screws for decompression on one side and PPS on the opposite side. Using this approach, we were able to compare the accuracy of PPS insertion with that of conventional open screw insertion in the same patients. There were 383 PPSs and 383 screws inserted by the open method. The accuracy of screw placement was evaluated on reconstructed computed tomography images obtained postoperatively, and screw misplacement was classified. Potential risk factors for screw misplacement were investigated in three-level mixed-effects logistic regression analysis.ResultsThirty-four screws (8.9%) were misplaced on the P-side and 37 (9.5%) were misplaced on the O-side; the difference was not statistically significant (P = 0.803). Subclassification analysis revealed minor perforation of 28 screws (7.3%) on the P-side and 32 (8.4%) on the O-side, moderate perforation of 5 screws (1.3%) on the P-side and 4 (1.0%) on the O-side, and severe perforation of 1 screw (0.3%) on each side. Three-level mixed-effects logistic regression analysis identified body mass index as a significant risk factor for screw misplacement on the P-side (odds ratio 1.194, 95% confidence interval 1.066–1.338).ConclusionsAccuracy of pedicle screw insertion was not significantly different between PPS insertion and conventional open screw insertion in the same patients. Body mass index had a significant influence on the risk of screw misplacement in PPS insertion.

Malpositioned pedicle screw in spine deformity surgery endangering the aorta: report of two cases, review of literature, and proposed management algorithm

Case reports and review of the literature with a proposed management algorithm. To report two cases of a potential vascular complication due to an incorrectly placed pedicle screw (PS) during spine deformity surgery. Relevant literature regarding the management of vascular complications is reviewed, and an evidence-based management algorithm is proposed. Aortic lesions represent a rare but potentially life-threatening complications with spine deformity and revision surgery, significantly increasing the risk. A management algorithm for an aortic lesion in the case of a malpositioned PS has not yet been published. Case 1: An 18-year-old female with proximal thoracic spinal non-instrumented fusion underwent a revision corrective procedure due to a progressive right-sided thoracolumbar compensatory curve. However, postoperative computed tomography (CT) performed to evaluate the position of the PS revealed malposition of the left T9 PS, which was abutting the descending aorta with CT angiography excluding the perforation of the aorta. Case 2: A 17-year-old male was scheduled for correction of Lenke 3-C-N adolescent idiopathic scoliosis. Postoperative routine evaluation with low-dose CT revealed a left T9 PS paravertebral malposition, and subsequent CTA demonstrated that the thread of the PS was in contact with the descending thoracic aorta and an unlikely hemodynamically significant vessel injury. Successful removal of both malpositioned PS was performed. In the first case, a cardiovascular surgeon attended the operation if an urgent thoracotomy was needed, and in the second case, additional video-assisted thoracoscopic control of the aorta was performed during PS removal. Preoperative imaging in spinal surgery is essential to avoid major vascular and other complications when placing PS, especially in thoracic deformities. When a potential major vessel complication emerges, an interdisciplinary approach and an appropriate management algorithm are mandatory to make the best clinical decisions. 4.

Comparative Analysis of Surgical Outcomes of C1–2 Fusion Spine Surgery between Intraoperative Computed Tomography Image Based Navigation-Guided Operation and Fluoroscopy-Guided Operation

ObjectiveFixation of the C1–2 segment is challenging because of the complex anatomy in the region and the need for a high degree of accuracy to avoid complications. Preoperative 3D-computed tomography (CT) scans can help reduce the risk of complications in the vertebral artery, spinal cord, and nerve roots. However, the patient may be susceptible to injury if the patient’s anatomy does not match the preoperative CT scans. The intraoperative 3D image-based navigation systems have reduced complications in instrument-assisted techniques due to greater accuracy. This study aimed to compare the radiologic outcomes of C1–2 fusion surgery between intraoperative CT image-guided operation and fluoroscopy-guided operation. MethodsWe retrospectively reviewed the radiologic images of 34 patients who underwent C1–2 fusion spine surgery from January 2009 to November 2018 at our hospital. We assessed 17 cases each of degenerative cervical disease and trauma in a study population of 18 males and 16 females. The mean age was 54.8 years. A total of 139 screws were used and the surgical procedures included 68 screws in the C1 lateral mass, 58 screws in C2 pedicle, nine screws in C2 lamina and C2 pars screws, four lateral mass screws in sub-axial level. Of the 34 patients, 19 patients underwent screw insertion using intraoperative mobile CT. Other patients underwent atlantoaxial fusion with a standard fluoroscopy-guided device. ResultsA total of 139 screws were correctly positioned. We analyzed the positions of 135 screws except for the four screws that performed the lateral mass screws in C3 vertebra. Minor screw penetration was observed in seven cases (5.2%), and major pedicle screw penetration was observed in three cases (2.2%). In one case, the malposition of a C2 pedicle screw was confirmed, which was subsequently corrected. There were no complications regarding vertebral artery injury or onset of new neurologic deficits. The screw malposition rate was lower (5.3%) in patients who underwent intraoperative CT-based navigation than that for fluoroscopy-guided cases (10.2%). And we confirmed that the operation time can be significantly reduced by surgery using intraoperative O-arm device. ConclusionSpinal navigation using intraoperative cone-beam CT scans is reliable for posterior fixation in unstable C1-2 pathologies and can be reduced the operative time.

End Vertebra Versus Apical Vertebra: Where Are We More Likely to Misplace in Spine Deformity?

Pedicle screws placement remains technically demanding. The thoracic curve apex is considerably difficult due to its unique morphology and severe rotation. In comparison the upper end vertebrae have smaller pedicles and limited soft tissue exposure. This study seeks to evaluate the likelihood of screw misplacement at the end vertebra and apex. A retrospective review of preoperative and postoperative computed tomographic (CT) scans of spinal deformity patients who underwent posterior spinal fusion with pedicle screw constructs between 2004 and 2011 was performed. Pedicles located at the upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV), and the major and minor apices were evaluated. Pedicle morphology was studied on preoperative CT and screw placement on postoperative CT. In total, 188 patients met the inclusion criteria, 172 had preoperative CT scans and 133 had postoperative CT scans. The UIV had a significantly lower percentage of normal pedicles (type A) compared with apex major, apex minor, or LIV (59.1% vs. 76.1% vs. 77.3% vs. 98.7%; P<0.001). UIV had significantly the lowest percentage of normal normally placed screws compared with LIV, apex major, or apex minor (69.4% vs. 97.3% vs. 87.6% vs. 92.1%; P<0.001). In a logistic regression adjusted for preoperative Cobb angles, UIV was more likely to have screws misplaced (odds ratio =7.56; 95% confidence interval, 4.01-14.30; P<0.001) and abnormal pedicles (odds ratio=2.81; 95% confidence interval, 1.52-5.19; P=0.001) compared with any other location studied. In abnormal pedicles, 41 (39.8%) of the 103 UIV screws were misplaced, whereas 10 (16.4%) of the 61 apex major, apex minor, or LIV screws were misplaced (P=0.007). The UIV presents more of a risk for pedicle screw misplacement and abnormal morphology when compared with LIV and apical vertebra. We believe these findings can aid in the surgeon's preoperative and intraoperative management to ensure increased success in accurate and safe pedicle screw placement. Level III.

Image-guided pedicle screws using intraoperative cone-beam CT and navigation. A cost-effectiveness study

Image-guided surgery using intraoperative cone-beam CT and navigation improves screw placement accuracy rates. However, this technology is associated with high acquisition costs. The aim of this study is to evaluate the costs of revision surgery from symptomatic pedicle screw malposition to justify whether the costs of acquiring intraoperative navigation justify the expected benefits. This is a retrospective cost-effectiveness analysis of consecutive patients who had pedicle screw instrumentation using intraoperative cone-beam CT and navigation compared with patients who underwent freehand pedicle screw instrumentation at our institution over 4 years. The costs associated with revision surgery for symptomatic pedicle screw malposition (excess length of stay, intensive care, theatre time, implants and additional outpatient appointments) were calculated. A total of 19 patients had symptomatic screw malpositioning requiring revision surgery. None of these patients had screws inserted under navigation. Revision surgery accounted for an extra 304 bed days and an additional 97 h theatre time. The total extra spent over 4 years was £464,038. When compared to the costs of revision surgery for screw malpositioning, it was cost neutral to acquire and maintain this technology. Intraoperative image-guided surgery reduces reoperation rates for symptomatic screw malposition and is cost-effective in high volume centers with improved patients outcomes. High acquisition and maintenance cost of such technologies is economically justifiable.

Measurement of thoracic and lumbar pedicle dimensions in Nigerians using computed tomography

Background: Pedicle screws are often used to stabilise the spine. They afford the benefit of a three-column control of the spine. The technique of pedicle screw insertion is familiar and has a well-documented safety profile during lumbar and thoracic spinal surgery. However, complications such as cerebrospinal fluid leakage due to pedicle screw misplacement, neurological irritation and pedicle penetration may occur. Therefore, knowledge of the dimensions of spinal pedicles is necessary for the fixation of pedicular screws to avoid possible complications. Aims: The aim of this study was to determine the maximal diameter and axial length of thoracic and lumbar pedicles in a homogenous African population using computed tomography (CT). This would establish normative data on the average size of pedicle screws that would be required during the surgery, hence maximising pull-out strength while reducing the possibility of revision of the pedicle screw placement. Methods: It is a retrospective study where the transverse pedicle width, axial pedicle length and sagittal pedicle width of T1–L5 were measured on 100 patients; 50 males, 50 females with normal spinal architecture using a 128-slice Toshiba CT scanner. Results: The mean axial length in the thoracic and lumbar vertebrae ranged from 31.76 ± 2.92 mm (T1) to 43.02 ± 3.32 mm (T12) and from 45.07 ± 2.40 mm (L5) to 46.32 ± 2.28 mm (L3), respectively. The mean TPW at the thoracic and lumbar vertebrae ranged from 4.53 ± 0.69 (T4) to 7.78 ± 1.31 mm (T12) and from 6.81 ± 1.25 mm (L1) to 12.95 ± 1.49 mm (L5), respectively. The mean sagittal diameter of thoracic and lumbar vertebrae ranged from 5.78 ± 1.07 mm (T1) to 10.98 ± 1.37 (T12) and from 9.51 ± 1.31 mm (L2) to 9.78 ± 1.61 (L4), respectively. Conclusion: The dimensions of thoracic and lumbar pedicles measured in this study vary with those obtained from other populations. This strengthens the case for customising the existing range of spinal pedicle screws according to local population characteristics.

Computer-assisted surgical navigation is associated with an increased risk of neurological complications: a review of 67,264 posterolateral lumbar fusion cases.

Pedicle screw malposition may result in neurological complications following posterolateral lumbar fusions (PLF). While computer-assisted navigation (NAV) and intraoperative neuromonitoring (ION) have been shown to improve safety in deformity surgeries, their use in routine PLFs remain controversial. This study assesses the risk of complications and reoperation for pedicle screw revision following PLF with and without ION and/or NAV surgery. Retrospective analyses were performed using the Truven Health MarketScan® databases to identify patients that had primary PLF with and without NAV and/or ION for degenerative lumbar disorders from years 2007-2015. Patients undergoing concomitant interbody fusions, spinal deformity surgery or fusion to the thoracic spine were excluded. Complications and reoperation for pedicle screw revision within 90 days of surgery were assessed. During the study period, 67,264 patients underwent PLFs. NAV only was used in 3.5% of patients, ION only in 17.9% and both NAV and ION in 0.8% of patients. In univariate analyses, there was a difference in the risk of neurological injuries among groups (NAV only: 1.4%, ION only: 0.8%, NAV and ION: 0.5%, No NAV or ION: 0.6%, P<0.001). In multivariable models, the use of NAV was associated with a higher risk of neurological complications when compared to ION only or no ION or NAV [NAV vs. ION only: odds ratio (OR) and 95% confidence interval (CI) =2.1 (1.4, 3.2), P=0.002; NAV vs. no ION or NAV: OR and 95% CI =2.5 (1.7, 3.5), P<0.001]. There was no difference in reoperation rates among the groups (P=0.135). Although the overall risk of neurological complications following PLFs is low, the use of NAV only was associated with an increased risk of neurological complications. No differences were observed in the rates of pedicle screw revision among groups.

The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility.

Retrospective chart review. To determine if obtaining a prone computed tomography (CT)-scan can better delineate a questionable screw-aorta relationship. Pedicle screw misplacement rate is reported between 6% and 15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention. One hundred eleven spinal deformity patients who underwent Posterior spinal fusion from 2004 to 2009 were evaluated. Patients with concerning screw-aorta relationship underwent additional prone CT scan. Mobility of the aorta was determined and distance was compared using prone and supine CT scans. Two thousand two hundred ninety five screws were reviewed, 36 screws in 18 patients were in proximity to the aorta. Fourteen screws (nine patients) appeared to be impinging the aorta. On prone CT, 13 out of the 14 instances the aorta moved away from the screw. The average distance at the screw level was 13.6 ± 4.8 mm in supine position and 8.9 ± 5.4 mm in prone position (P = 0.001). In one instance the relationship was unchanged on prone CT. No screw was noted to violate the lumen or distort the aorta. Supine CT scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization. 3.

Accuracy and reliability of spinal navigation: An analysis of over 1000 pedicle screws

PurposeTo estimate the rate of pedicle screw malpositioning associated with placing pedicle screws using intraoperative computed tomography (CT)-guided spinal navigation. MethodsWe analysed the records of 219 patients who underwent pedicle screw fixation using O-arm-based navigation. Screw placement accuracy was evaluated on intraoperative CT scans acquired after pedicle screw insertion. Breaches were graded according to the Gertzbein classification (grade 0–III). ResultsOf 1152 pedicle screws included, 47 had pedicle violations noted on intraoperative CT. Pedicle screw violation was noted for 17 of 241 screws placed in the cervical spine (overall breach rate, 7.05%; 3.73% and 3.3% with grade I and II, respectively), for 11 of 300 screws placed in the thoracic spine (overall breach rate, 3.67%; 2%, 1%, and 0.67% with grade I, II, and III, respectively), and for 22 of 611 screws placed in the lumbar spine (overall breach rate, 3.6%; 2.29% and 0.82% with grade I and II, respectively). The rate of accuracy of pedicle screw fixation was 93%, 96.33%, and 96.4% for the cervical, thoracic, and lumbar spine, respectively. ConclusionsUsing O-arm-based intra-operative three-dimensional scans for navigation can improve the reliability, accuracy, and safety of pedicle screw placement, reducing the risk for reoperation and hospitalization due to implant-related complications. Further improvement may be achieved by adequate consideration of potential sources of errors.