Effect of pedicle screw misplacement on the pull-out strength using personalized finite element modeling.

Intraoperative misplacement of vertebral pedicle screws is prevalent. While a pedicle screw misplacement of up to 4 mm is often considered safe by clinical standards, this may reduce the pull-out strength thereby increasing the risk of postoperative screw loosening. This study aimed to compare the pull-out strength of ideally-placed and misplaced pedicle screws via personalized finite element (FE) modeling simulations. Three-dimensional FE models to simulate pull-out tests of pedicle screws were constructed. Vertebral geometries and material properties were both determined based on computed tomography images from lumbar spine (L1-L5) of a 29-year-old healthy male individual. Pedicle screws were bilaterally placed under four conditions: ideal placement (no cortex perforation) as well as minor medial, minor lateral, and severe lateral misplacements causing cortex perforations. Minor and severe misplacements corresponded to, respectively, grades C and D of the Gertzbein classification. After meshing and voxel-based vertebral material assignments based on two distinct mappings from literature, pull-out strengths were estimated by considering a strain-based damage model to accurately simulate bone fractures. Results indicated that the mean of FE-predicted pull-out forces for ideally-placed screws (1583 and 2412 N for material mappings 1 and 2, respectively) was within the range of previous experimental data (ranging from 1016 to 2443 N) thus confirming the model validation. The mean of all pull-out forces for each misplaced screw group was significantly smaller (p < 0.05) than that of the ideally-placed screws, e.g., 20 % for minor medial, 22 % for minor lateral, and 37 % for severe lateral misplacements. These findings indicated that even clinically-acceptable screw misplacements (up to 4 mm) could significantly reduce the pull-out strengths of pedicle screws thus imposing higher risk of postoperative screw loosening. To avoid these common screw misplacements, the use of advanced approaches for pedicle screw placements appears to be imperative.

Delayed neurological deficit due to a medially misplaced thoracic pedicle screw during adolescent idiopathic scoliosis correction: a complication 6 years in the making.

PURPOSE: Neurological deficits developing years after pedicle screw misplacement is a rare phenomenon. Here, we report level IV evidence of a previously asymptomatic medial thoracic pedicle screw resulting in paraparesis after a motor vehicle accident. METHODS: A 21-year-old male presented with acute onset of paraparesis following a motor vehicle collision. Six years prior this incident, the patient underwent a thoracolumbar fusion T4-L4 for AIS performed by an outside orthopedic surgeon. CT scan and CT myelogram illustrated decreased spinal canal diameter and cord compression from a medial T8 pedicle screw. RESULTS: Surgical removal of the misplaced pedicle screw resulted in a gradual complete recovery sustained over a period of 2 years. This case is compared to those reported in the literature review between 1981 and 2019 concerning delayed neurological deterioration related to misplaced pedicle screw. CONCLUSION: This case reports a delayed neurological deficit implicating a misplaced pedicle screw. This phenomenon remains rare since 5 cases were reported in the literature over the last 4 decades. It calls into focus the need for confirmation of safe instrumentation during the intraoperative period. It also illustrates the potential difficult decision-making in regard to asymptomatic misplaced instrumentation. LEVEL OF EVIDENCE: IV.

In idiopathic scoliosis distances of spinal cord to thoracic pedicle are within 2 mm in a large region of the thoracic apex.

Despite a 15% misplacement rate of screws in idiopathic scoliosis surgery, little is known about the relationship between pedicles and nerve structures in the entire thoracic curve. This study aimed to explore the spinal cord's proximity to the pedicle wall at each thoracic vertebra in the entire thoracic curve, while considering different anatomical changes. Spinal cord to medial pedicle distances were measured on magnetic resonance imaging in 73 patients who underwent posterior spinal fusion with pedicle screw instrumentation. Associations with different variables were examined. A total of 51 patients (69.9%) showed a distance within 2 mm at the apex vertebra on the concave side, more than 50% had a distance within 2 mm in the next thoracic vertebra level above and below, and more than 25% two levels above and below. Weak correlations were found between proximity of the spinal cord at the apex vertebra and vertebra's level and Cobb angle on the concave side (r = - 0.310, P = 0.008, r = 0.380, P = 0.001, respectively). These results emphasize the importance of thorough assessment when placing thoracic pedicle screws in idiopathic scoliosis patients. Further research is warranted to develop surgical strategies aimed at preventing potentially neurological complications resulting from screw misplacement.

Pulse-train versus single-pulse t-EMG stimulation for intraoperative neurophysiologic monitoring of thoracic pedicle screws in adolescent idiopathic scoliosis.

OBJECTIVE: To assess the PTS method in neuromonitoring of thoracic pedicle screws in a young cohort of AIS patients. The accuracy of both PTS (Pulse-train stimulation) and SPS (Single-pulse stimulation) techniques in the detection of misplaced thoracic screws was compared with special reference to the screws placed at the concavity and the convexity of the curve. PATIENTS AND METHODS: A single-center prospective clinical cohort study. LEVEL OF EVIDENCE II: Twelve AIS patients who underwent elective surgery were included in this study. Screw stimulation using repetitive constant-current stimulus train of variable intensities was first performed after screw insertion. SPS was performed immediately after PTS. Postoperatively, CT scan was used to check the final position of the screws. A total of 246 thoracic pedicle screws were placed. Thresholds of screws placed in the convexity and the concavity were compared. RESULTS: Invasion of the spinal canal was postoperatively confirmed in 29 of the pedicle screws. The SPS technique detected three (10.3%) of these screws using a threshold limit of 12 mA. The PTS technique detected 25 (86.2%) of the 29 misplaced screws using threshold of 30 mA (negative predictive value, 93.1%). When using a PTS threshold of < 20 mA, the positive predictive value was 70%. SPS did not detect any of the misplaced screws at the apex level of the scoliotic curves, and PTS detected 10 out of 17 of these screws. Overall, area under the ROC curve was 0.82 for PTS and 0.61 for SPS. CONCLUSIONS: PTS is a reliable method for detecting medially misplaced screws among young AIS patients undergoing scoliosis surgery. PTS provides more accurate predictions than SPS and improves the identification of screws invading the spinal canal at the apex or near the apex levels.

Freehand screw insertion technique without image guidance for the cortical bone trajectory screw in posterior lumbar interbody fusion: what affects screw misplacement?

OBJECTIVE: Cortical bone trajectory (CBT) screw insertion using a freehand technique is considered less feasible than guided techniques, due to the lack of readily identifiable visual landmarks. However, in posterior lumbar interbody fusion (PLIF), after resection of the posterior anatomy, the pedicles themselves, into which implantation is performed, are palpable from the spinal canal and neural foramen. With the help of pedicle wall probing, the authors have placed CBT screws using a freehand technique without image guidance in PLIF. This technique has advantages of no radiation exposure and no requirement for expensive devices, but the disadvantage of reduced accuracy in screw placement. To address the problem of symptomatic breaches with this freehand technique, variables related to unacceptable screw positioning and need for revisions were investigated. METHODS: From 2014 to 2020, 182 of 426 patients with single-level PLIF were enrolled according to the combined criteria of L4-5 level, excluding cases of revision and isthmic spondylolisthesis; using screws 5.5 mm in diameter; and operated by right-handed surgeons. We studied the number of misplaced screws found and replaced during initial surgeries. Using multiplanar reconstruction CT postoperatively, 692 screw positions on images were classified using previously reported grading criteria. Details of pedicle breaches requiring revisions were studied. We conducted a statistical analysis of the relationship between unacceptable (perforations > 2 mm) misplacements and four variables: level, laterality, spinal deformity, and experiences of surgeons. RESULTS: Three screws in L4 and another in L5 were revised during initial surgeries. The total rate of unacceptable screws on CT examinations was 3.3%. Three screws in L4 and another in L5 breached inferomedial pedicle walls in grade 3 and required revisions. The revision rate was 2.2%. The percentage of unacceptable screws was 5.2% in L4 and 1.7% in L5 (p < 0.05), whereas other variables showed no significant differences. CONCLUSIONS: A freehand technique can be feasible for CBT screw insertion in PLIF, balancing the risks of 3.3% unacceptable misplacements and 2.2% revisions with the benefits of no radiation exposure and no need for expensive devices. Pedicle palpation in L4 is the key to safety, even though it requires deeper and more difficult probing. In the initial surgeries and revisions, 75% of revised screws were observed in L4, and unacceptable screw positions were more likely to be found in L4 than in L5.

Pedicle screw accuracy in thoracolumbar fractures- is routine postoperative CT scan necessary?

BACKGROUND: While several studies report on accuracy rates of pedicle screws, risk factors associated with inaccurate pedicle screw positioning in patients with thoracolumbar fractures are reported rarely. CT scan as a routine postoperative control is advocated by various authors, however its necessity remains unclear. METHODS: Two hundred forty-five patients were included in this retrospective study. Percutaneous dorsal instrumentation was most commonly performed (n = 201). Classification of Zdichavsky et al. and Rao et al. were used to classify screw misplacement and anterior perforation was further evaluated according to the extent of perforation (< 2 mm; > 2 mm). Multivariate analysis was performed to identify risk factors for misplacement of screws. RESULTS: One thousand sixty-eight pedicle screws were inserted in 245 patients. Misplacement was found in 51 screws (4.8%) in 42 patients (17.1%) according to the classification of Zdichavsky et al. and in 75 screws (7.0%) in 64 patients (26.1%) according to the classification of Rao et al.. An anterior perforation of the vertebral cortex was found in 56 screws (5.2%). Multivariate analysis showed fracture location in the upper thoracic (p = 0.048) and lumbar spine (p = 0.013) to be the only independent predictors for screw misplacement. In addition a significant correlation between pedicle diameter and the occurrence of screw malposition was found (p = 0.003). No consequences were drawn from postoperative routine CT in asymptomatic patients. CONCLUSION: An overall low rate of screw misplacement was found with fracture location in the upper thoracic and lumbar spine being the only factors independently associated with the risk of screw misplacement. No consequences were drawn from postoperative routine CT in asymptomatic patients. Therefore its use has to be discussed critically.

Comparison of a ceiling-mounted 3D flat panel detector vs. conventional intraoperative 2D fluoroscopy in plate osteosynthesis of distal radius fractures with volar locking plate systems.

OBJECTIVES: To compare intraoperative 3D fluoroscopy with a ceiling-mounted flat panel detector in plate osteosynthesis of distal radius fractures (AO/OTA 2R3C1.2) with volar locking plate systems to conventional 2D fluoroscopy for detection of insufficient fracture reduction, plate misplacement and protruding screws. METHODS: Using a common volar approach on 12 cadaver forearms, total intraarticular distal radius fractures were induced, manually reduced and internally fixated with a 2.4 distal radius locking compression plate. 2D (anterior-posterior and lateral) and 3D (rotational) fluoroscopic images were taken as well as computed tomographies. Fluoroscopic images, Cone Beam CT (CBCT), 360° rotating sequences (so called "Movies") and CT scans were co-evaluated by a specialist orthopedic surgeon and a specialist radiologist regarding quality of fracture reduction, position of plate, position of the three distal locking screws and position of the three diaphyseal screws. In reference to gold standard CT, sensitivity and specifity were analyzed. RESULTS: "Movie" showed highest sensitivity for detection of insufficient fracture reduction (88%). Sensitivity for detection of incorrect position of plate was 100% for CBCT and 90% for "Movie." For intraarticular position of screws, 2D fluoroscopy and CBCT showed highest sensitivity and specifity (100 and 91%, respectively). Regarding detection of only marginal intraarticular position of screws, sensitivity and specifity of 2D fluoroscopy reached 100% (CBCT: 100 and 83%). "Movie" showed highest sensitivity for detection of overlapping position of screws (100%). When it comes to specifity, CBCT achieved 100%. Regarding detection of only marginal overlapping position of screws, 2D fluoroscopy and "Movie" showed highest sensitivity (100%). CBCT achieved highest specifity (100%). CONCLUSION: As for assessment of quality of fracture reduction and detection of incorrect position of plate as well as overlapping position of the three diaphyseal screws CBCT and "Movie" are comparable to CT - especially when combined. Particularly sensitivity is high compared to standard 2D fluoroscopy.

Part 1: Outcome of Posterior Pelvic Ring Injuries and Associated Prognostic Factors - A Five-Year Retrospective Study of One Hundred and Sixty Five Operated Cases with Closed Reduction and Percutaneous Fixation.

PURPOSES: The aim of this study was to evaluate: 1. the outcome of pelvic ring fractures treated by closed reduction and percutaneous fixation, 2. the prognostic factors associated with a poor quality reduction, 3. the prognostic factors associated with ilio-sacral screws misplacement and 4. the prognostic factors associated with nonunion. METHODS: Data from medical charts for all patients admitted with unstable posterior pelvic ring injuries from 2009 to 2013 were extracted. A total of 165 patients with a mean age of 40 years were included. One hundred and five patients were reviewed at a mean of 32 months of follow-up. The prognostic factors analyzed were clinical and radiological factors. Tile B and Tile C pelvic ring fractures were compared and analyzed separately. Then specific statistical analysis was performed using a logistic regression model to eliminate confusion factors. RESULTS: An excellent or good clinical result was achieved for 94 patients (90%). An excellent or good reduction was achieved for 141 patients (85%). Nonunion rate, smoking patients, bad reductions, age of patients and ISS score were significantly higher in Tile C group. To eliminate confusion factors we used a multivariate analysis logistic regression model. Only unstable vertical bilateral posterior injuries (Tile C2 and C3) were independent prognostic factors for unsatisfactory reduction (p = 0.001; OR = 4.72; CI 95% [2.08-16.72]). Screw misplacement was recorded for 30 patients (16%) and sacral dysmorphia was an associated prognostic factor (p = 0.0001; OR = 15.6; CI95% [3.41-98.11]). Nonunion was recorded for ten patients (6%) and smoking was an associated prognostic factor (p = 0.01, OR = 5.12; CI95% [1.1-24.1]). CONCLUSIONS: Posterior pelvic ring fractures treated by closed reduction and percutaneous fixation are associated with excellent/good clinical results if excellent/good reduction and bone healing are achieved without screw misplacement. Bilateral unstable vertical posterior pelvic ring injuries, and sacral dysmorphia are risk factors for bad quality reduction and screw misplacement respectively.

Effect of different multiplanar reformation algorithms on image quality of intraoperative three-dimensional fluoroscopy.

Different multiplanar reformation (MPR-512 and -256) algorithms of intraoperative acquired 3-D-fluoroscopy data exist without recommendations for use in the literature. To compare algorithms, 3-D-fluoroscopic data sets of 46 radius fractures were blinded and processed using MPR-256 and -512 (Ziehm, Vision-Vario 3D). Each reformatted data set was analysed to evaluate image quality, fracture reduction quality and screw misplacements. Overall image quality was higher rated in the MPR-512 compared with the MPR-256 (3.2 vs. 2.2 points, scale 1-5 points), accompanied by a reduced number of scans that could not be analysed (10 vs. 19%). Interobserver evaluation of fracture reduction quality was fair to moderate (independent of the algorithm). In contrast, for screw misplacements MPR-depended ratings were found (MPR-256: fair to moderate; MPR-512: moderate to substantial). Optimization of post-processing algorithms, rather than modifications of image acquisition, may increase the image quality for assessing implant positioning, but limitations in evaluating fracture reduction quality still exist.

Accuracy of Patient-Specific Template-Guided Versus Freehand Cervical Pedicle Screw Placement from C2 to C7: A Randomized Cadaveric Study.

BACKGROUND: Dorsal spinal instrumentation with cervical pedicle screws (CPS) and rod constructs is performed for numerous pathologies of the cervical spine, although technically demanding. Screw misplacement is biomechanically disadvantageous and carries the risk of neurovascular sequelae. The aim of this study was to assess the accuracy of patient-specific, template-guided CPS placement from C2 to C7 compared with the freehand technique. METHODS: Patient-specific targeting guides were used for placement of 3.5 mm CPS from C2 to C7 in 4 cadaveric specimens. Template-guided instrumentation was randomized for each cervical level and side and the contralateral side instrumented likewise but with the freehand technique. No fluoroscopy was used at all, and the spinal canal was not opened for the freehand technique. Accuracy was assessed by computed tomography, grading perforations using a 2-mm increment method, and time efficiency was compared between the 2 techniques. RESULTS: In total, 48 screws were inserted with an equal distribution of 24 screws (50%) in each of the 2 groups. Outer pedicle width averaged 5.1 ± 1.0 mm (range 2.7-7.8); 66.7% (n = 16) of template-guided versus 20.8% (n = 5) of freehand CPS were fully contained within the pedicle (P = 0.001), whereas 91.7% (n = 22) versus 50% (n = 12) were within the <2 mm "safe" zone (P = 0.001). The mean time for instrumentation per level and side was 03:09 ± 01:37 minutes for the template-guided versus 02:32 ± 01:04 minutes for the freehand technique (P = 0.132). CONCLUSIONS: In a cadaver model, template-guided CPS placement has a significantly greater accuracy than the freehand technique. This accuracy is comparable with navigated techniques reported in the literature.

[Robot assisted sacroiliac screw placement with a modified method of screw path planning].

Objective: To introduce a robot-assisted modified method of sacroiliac screw path planning in order to reduce the incidence of screw misplacement. Methods: The study involved 13 patients suffering from posterior pelvic injuries treated by percutaneous sacroiliac screw in Yantai Shan Hospital from August 2016 to May 2018. The patients included 9 males and 4 females, aged from 18 to 70 years (mean age 46.2 years). Causes of injury were traffic accidents (n=7), crushing injury (n=4) and fall from height (n=2). According to AO classification, 8 cases were classified with type B fractures (3 with type B1 and 5 with type B2), and 5 cases with type C fractures (2 with type C1, 1 with type C2, 2 with type C3). All the patients were treated by robot-assisted percutaneous sacroiliac screws (AO cannulated screws with a diameter of 7.3 mm) with an improved method of screw path planning. The screw placement time, blood loss, postoperative neurological, vascular and visceral function etc were observed. X-ray and CT were checked in the follow-up after the operation. Visual analogue scale (VAS) score was used to assess the pain degree of patients one week after the surgery. Results: All the sacroiliac screws were successfully implanted once with the robot-assisted improved method of screw path planning. The mean placement time of single screw was 15.9 min and the mean blood loss for single screw placement was less than 1 ml. No clinical manifestations of injuries of blood vessels, internal organs and lumbosacral nerve was found after the operation. The postoperative X-ray films and CT showed that none of the sacroiliac screws wore out the sacral body or the sacral wing's frontal cortex. Also, it was found that none of the sacroiliac screws strayed into the sacral canal and the intervertebral space. The mean VAS score decreased from preoperative 6.9 (4-10) to postoperative 1.8(0-3). Conclusion: The robot-assisted improved method of screw path planning contributes to safe and accurate sacroiliac screw placement.

[Relevance of spinal navigation in reconstructive surgery of the cervical spine]. / Relevanz der spinalen Navigation in der rekonstruktiven Halswirbelsäulenchirurgie.

BACKGROUND: Spinal navigation has made significant advances in the last two decades. After initial experiences with pedicle screws in the thoracic and lumbar spine, technological improvements have resulted in their increased application in the cervical spine. Instrumentation techniques like cervical pedicle screws, lateral mass screws in C1 and transarticular screws C1/C2 have become standard due to the application of image guidance. TECHNIQUE: Different navigation techniques can be distinguished based on the type of imaging. In the cervical spine, the preoperative computer tomography (CT) scan that requires intraoperative matching is still the standard of care due to the high image quality. 3D fluoroscopy navigation techniques are currently widely used in the lumbar spine, but the reduced image quality obviates the application in the more sophisticated cervical anatomy or the cervicothoracic region. The future availability of intraoperative CT scans (iCT) combines the advantages of high image quality with those of intraoperative image acquisition. This will lead to a wider use of image guidance in the cervical spine and will enable the surgeon to apply minimally invasive techniques with higher accuracy. APPLICATION: The successful application of spinal navigation is based on the technical knowledge of navigation systems and its exercise in daily routine. Only the sufficient experience of the clinical staff makes it possible to standardize operational procedures to increase patient safety, reduce radiation dose and shorten operation time.

Reoperation within 2 years after lumbar interbody fusion: a multicenter study.

PURPOSE: Posterior lumbar interbody fusion (PLIF)/transforaminal lumbar interbody fusion (TLIF) can have complications that require reoperation. The goal of the study was to identify risk factors for reoperation within 2 years after PLIF/TLIF. METHODS: A retrospective analysis of a prospective multicenter database was performed for patients who underwent PLIF/TLIF. A total of 1363 patients (689 males and 674 females) were identified, with an average age of 65.9 years old. Comorbidities, perioperative ASA grade, and operative factors were compared between patients with and without reoperation. Risk factors for reoperation were identified in multivariate logistic analysis. RESULTS: There were 38 reoperations within 2 years after PLIF/TLIF (2.8%). The original surgical procedures were open PLIF (n = 26), open TLIF (n = 10), and minimally invasive surgery (n = 2). Reoperation was due to adjacent segment degeneration (ASD) (n = 10), surgical site infection (SSI) (n = 9), screw misplacement (n = 6), postoperative epidural hematoma (n = 6), pseudoarthrosis (n = 4), and cage protrusion (n = 3). Number of levels fused and dural tear were significantly associated with reoperation. In analysis of complications requiring reoperation, SSI was related to diabetes mellitus and dural tear, and postoperative epidural hematoma was related to fusion of two or more levels, EBL, and operation time. In multivariate logistic regression, fusion of two or more levels (HR 2.19) was significantly associated with reoperation. CONCLUSION: Surgical invasiveness, as reflected by number of fused levels, operation time, EBL and dural tear, was associated with reoperation. Fusion of two or more levels is a strong risk factor for reoperation within 2 years after initial PLIF/TLIF. These slides can be retrieved under Electronic Supplementary Material.

Accuracy of minimally invasive percutaneous thoracolumbar pedicle screws using 2D fluoroscopy: a retrospective review through 3D CT analysis.

BACKGROUND: In the literature, there is a large variation in the reported misplacement rates of pedicle screws. The use of minimally invasive surgical techniques is increasing and as such there has only been a small amount of data to look at the misplacement rate of percutaneously inserted thoracic and lumbar pedicle screws. METHODS: A retrospective analysis of post-operative computed tomography (CT) scans were performed on 108 patients who underwent minimally invasive percutaneously inserted thoracic and lumbar pedicle screws by a single surgeon. Analysis of the screw trajectory using strict guidelines was performed using multiplanar reconstruction CT scan data to determine the accuracy of the pedicle screws. RESULTS: A total of 614 screws were inserted in vertebral levels T2 to S1. Twenty-five (4.07%) screws were considered misplaced having breached the pedicular cortex. Thoracic pedicle screws had a statistically higher misplacement rate than lumbar pedicle screws (14.67% vs. 2.60% respectively, P<0.001). A single screw required replacement (0.16%) and there were no permanent neurological deficits. The misplacement rates were lower than those reported for open screw placement and equivalent to 3D CT navigated misplacement rates. CONCLUSIONS: Percutaneously inserted pedicle screws using 2D fluoroscopy offers a safe and accurate option for spinal stabilisation with an extremely low misplacement rate and morbidity. Overall, the low misplacement rates were equivalent and in most cases lower compared to open and computer assisted navigation techniques. However, we would recommend that given a misplacement rate of 14.67% for thoracic pedicle screws that computer assisted navigation may be able to offer further improvements in accuracy.

[Intraoperative virtual implant planning for volar plate osteosynthesis of distal radius fractures]. / Intraoperative virtuelle Implantatplanung bei der volaren Plattenosteosynthese distaler Radiusfrakturen.

BACKGROUND: Digital planning of implants is in most cases conducted prior to surgery. The virtual implant planning system (VIPS) is an application developed for mobile C-arms, which assists the virtual planning of screws close to the joint line during surgery for treatment of distal radius fractures with volar plate osteosynthesis. The aim of this prospective randomized study was to acquire initial clinical experiences and to compare the VIPS method with the conventional technique. METHOD: The study included 10 patients for primary testing and 30 patients with distal radius fractures of types A3, C1 and C2, divided in 2 groups. In the VIPS group, after placement of the plate and fracture reduction, a virtual 3D model of the plate was matched with the image of the plate from the fluoroscopic acquisition. Next, the length and position of the screws close to the joint line were planned on the virtual plate. The control group was treated with the same implant in the conventional way. Data were collected regarding screw replacement, fluoroscopy and operating room (OR) times. RESULTS: The VIPS group included six A3, one C1 and eight C2 fractures, while the control group consisted of six A3 and nine C2 fractures. Three screws were replaced in the VIPS group and two in the control group (p = 0.24). The mean intraoperative fluoroscopy time of the VIPS group amounted to 2.58 ± 1.38 min, whereas it was 2.12 ± 0.73 min in the control group (p = 0.26). The mean OR time in the VIPS group was 53.3 ± 34.5 minutes and 42.3 ± 8.8 min (p = 0.23) in the control group. CONCLUSION: The VIPS enables a precise positioning of screws close to joint line in the treatment of distal radius fractures; however, for routine use, further development of the system is necessary.

Comparison of intraoperative flat panel imaging and postoperative plain radiography for the detection of intraarticular screw displacement in volar distal radius plate ostheosynthesis.

OBJECTIVES: To investigate if intraoperative 3D flat panel imaging improves the detection of radiocarpal intraarticular screw misplacement (RCSM) in comparison to standard postoperative x-ray. METHODS: In a study on cadaver specimens, we evaluated the sensitivity and specificity to detect RCSM using X-ray, intraoperative 3D-fluoroscopy as well as the digital volume tomography. The gold standard reference was computed tomography. RESULTS: Sensitivity for the detection of RCSM for X-ray was 58% and specificity 88%. For DVT, the sensitivity to detect RCSM was 88% and the specificity 53%. For 3D-fluoroscopy, the sensitivity for RCSM was 68% and specificity 95%. When combining the methods, the best performance was found, when combining the two intraoperative imaging methods, with a resulting sensitivity of 88% and a specificity of 73%. CONCLUSIONS: Intraoperative 3D fluoroscopy and digital volume tomography appear to be at least as sensitive and specific to detect RCSM than the regular postoperative radiography in two planes. However, especially discrete screw misplacements can be missed with either method. LEVEL OF EVIDENCE: Level IV. Diagnostic device study.

Management of C1-2 traumatic fractures using an intraoperative 3D imaging-based navigation system.

OBJECT: Fractures of C-1 and C-2 are complex and surgical management may be difficult and challenging due to the anatomical relationship sbetween the vertebrae and neurovascular structures. The aim of this study was to evaluate the role, reliability, and accuracy of cervical fixation using the O-arm intraoperative 3D image-based navigation system. METHODS: The authors evaluated patients who underwent a navigation system-based surgery for stabilization of a fracture of C-1 and/or C-2 from August 2011 to August 2013. All of the fixation screws were intraoperatively checked and their position was graded. RESULTS: The patient population comprised 17 patients whose median age was 47.6 years. The surgical procedures were as follows: anterior dens screw fixation in 2 cases, transarticular fixation of C-1 and C-2 in 1 case, fixation using the Harms technique in 12 cases, and occipitocervical fixation in 2 cases. A total of 67 screws were placed. The control intraoperative CT scan revealed 62 screws (92.6%) correctly placed, 4 (5.9%) with a minor cortical violation (<2 mm), and only 1 screw (1.5%) that was judged to be incorrectly placed and that was immediately corrected. No vascular injury of the vertebral artery was observed either during exposition or during screw placement. No implant failure was observed. CONCLUSIONS: The use of a navigation system based on an intraoperative CT allows a real-time visualization of the vertebrae, reducing the risks of screw misplacement and consequent complications.

Endovascular aortic injury repair after thoracic pedicle screw placement.

Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws.