Pedicle Axis Research Articles

A New Pilot Hole Preparation System for Percutaneous Pedicle Screw Placement - A Randomized Controlled Study.

Randomized controlled study. To introduce a new pilot hole preparation system for percutaneous pedicle screw placement and investigate its efficiency and safety in comparison with the conventional method. Placing screws accurately, rapidly, and safely with less radiation exposure is critical for minimally invasive Lumbar interbody fusion (LIF). Optimizing pilot hole preparation instruments has important clinical implications. A total of 60 patients (180 screws) were included in this study. All patients were randomized into two groups (new system vs conventional method) and performed single-level minimally invasive percutaneous fixation, interbody fusion, and unilateral decompression. Basic information, time of pilot hole preparation, time of screw placement, and fluoroscopy time were recorded. Screw placement accuracy was graded based on the Gertzbein-Robbins scale, and the angle between the screw axis and the pedicle axis was collected in postoperative CT. There was no statistical difference in basic information between the two groups. The mean time of single pilot hole preparation was 4.08±1.01 min in the new system group and 5.34±1.30 min in the conventional method group (P<0.001). The time of single screw placement was significantly shorter in the new system group (0.82±0.20 vs 1.72±0.33min), and the fluoroscopy time was also less in the new system group (13.70±3.42 vs 19.95±5.50 s) (P<0.001). Screw placement accuracy assessment showed that there were 85 (94.45%) A-grade screws in the new system group while 76 (84.44%) A-grade screws in the conventional method group (P=0.027). The new pilot hole preparation system has shown significant reductions in the time of pilot hole preparation, time of screw placement, and radiation exposure, and has good clinical application value.

Caudal vertebra rat free flap in the groin: A preliminary study of a new combined osteocutaneous flap model

IntroductionMurins were used for microsurgical training but in the literature, only a few papers reported about murin combination of flaps and fewer about osteocutaneous ones. We proposed a rat model of a combined osteocutaneous flap in which the pedicle axis is intentionally lengthened. Technical noteFrom June to August 2020, one corpse and eight living Albinos Wistar rats were dissected. The 4th vertebra was harvested with its vessels and transferred to the groin with end-to-side anastomosis to the femoral vessels. Surviving rats were dissected to explore the combined osteocutaneous flap. Only two rats survived until second dissection. Transfixiant arterial and veinous stitches were observed in failed procedures. Caudal pedicles and epigastric pedicles were permeable in surviving animal with bleeding of the vertebra body surface. DiscussionPerspective of simultaneous vertebral free flap and bone graft could build up a potential rat model of comparison with a prelaminar flap.

Free-hand technique of C7 pedicle screw insertion using a simply defined entry point without fluoroscopic guidance for cervical spondylotic myelopathy patients with C3 to C6 instrumented by lateral mass screws: a retrospective cohort study

BackgroundNowadays, both lateral mass screw (LMS) and pedicle screw were effective instrumentation for posterior stabilization of cervical spine. This study aims to evaluate the feasibility of a new free-hand technique of C7 pedicle screw insertion without fluoroscopic guidance for cervical spondylotic myelopathy (CSM) patients with C3 to C6 instrumented by lateral mass screws.MethodsA total of 53 CSM patients underwent lateral mass screws instrumentation at C3 to C6 levels and pedicle screw instrumentation at C7 level were included. The preoperative 3-dimenional computed tomography (CT) reconstruction images of cervical spine were used to determine 2 different C7 pedicle screw trajectories. Trajectory A passed through the axis of the C7 pedicle while trajectory B selected the midpoint of the base of C7 superior facet as the entry point. All these 53 patients had the C7 pedicle screw inserted through trajectory B by free-hand without fluoroscopic guidance and the postoperative CT images were obtained to evaluate the accuracy of C7 pedicle screw insertion.ResultsTrajectory B had smaller transverse angle, smaller screw length, and smaller screw width but both similar sagittal angle and similar pedicle height when compared with trajectory A. A total of 106 pedicle screws were inserted at C7 through trajectory B and only 8 screws were displaced with the accuracy of screw placement as high as 92.5%.ConclusionIn CSM patients with C3 to C6 instrumented by LMS, using trajectory B for C7 pedicle screw insertion is easy to both identify the entry point and facilitate the rod insertion.

Is the morphology of the apical pedicles influenced by apical rotation or the coronal curve magnitude in adolescent idiopathic scoliosis?: a radiographic assessment.

Asymmetry in pedicle anatomy is most distinctly noted around the apex of the curve. The correlation of pedicle dysmorphia with apical vertebral rotation (AVR) and coronal Cobb angle (CCA) has not been studied. To establish whether pedicle dysmorphism is linked to curve magnitude CCA and the AVR in adolescent idiopathic scoliosis (AIS). Preoperative plain whole spine standing radiographs and non-contrast computed tomography (CT) scans of 25 AIS patients that were operated at a single centre from 2013 to 2019 were retrospectively reviewed by 3 independent co-investigators. CCA was noted on the standing radiograph, whereas the AVR was measured on the axial cuts of CT scan. Pedicle morphometric measurements were performed for apical and periapical pedicles. These included apical vertebra (when present), 2 vertebrae above (U1 and U2) and below (B1 and B2) the apex vertebra/disc. The pedicle morphometric measurements were performed on CT scans. We assessed the transverse pedicle diameter, transverse cancellous channel diameter, sagittal pedicle diameter, pedicle length and pedicle axis length. Correlation tests between various pedicle morphometric measurements, AVR and the curve magnitude (Cobb angle) was performed by the Pearson correlation test. The apex of the major curve was in the thoracic spine in 20 patients, thoracolumbar in three patients and in the lumbar spine in two patients. The mean Cobb angle was 61.5 ± 9.3° and the mean AVR was 28.4 ± 17.8°. A positive correlation was noted with the AVR for U1 concave pedicle length (r = 0.45, p = 0.03), pedicle axis length of the U2 concave pedicle (r = 0.6, p = 0.04), transverse pedicle diameter of the convex apical vertebrae (r = 0.82, p = 0.00009) and the convex apical transverse pedicle diameter (r = 0.80, p = 0.002). A negative correlation with the AVR was noted for U2 convex pedicle length (r = -0.51, p = 0009), transverse cancellous channel diameter of the U2 concave pedicle (r = -0.42, p = 0.04) and apical concave pedicle (r = -0.78, p = 0.002) and the sagittal pedicle diameter for the convex pedicle of U2 (r = -0.45, p = 0.03) and apex(r = -0.59, p = 0.04). The Cobb angle did not show a significant correlation with any of the pedicle measurements at any of the levels on the convex and the concave sides. Pedicle asymmetry and dysmorphism demonstrate a morphometric association with the apical vertebral rotation than the curve magnitude. The pedicle length and the pedicle axis length increase on the concave apical and periapical region with increase in AVR. The transverse cancellous channel diameter significantly decreases on the concave apical region with the increase in AVR. The sagittal pedicle diameter decreases on the convex side with the increase in AVR.

Anatomical and imaging measurements of the angle between the axis of the lumbar pedicle and lateral isthmus margin and its clinical significance

BackgroundThis study aims to explore the measurement of the angle between the axis of the pedicle and the lateral margin of the isthmus on the lumbar spine, and investigate its clinical significance.MethodsThe angle was measured on 120 normal adults’ X-ray and 25 dry anatomical specimens. 60 screws were placed by junior residents on 6 wet specimens through the freehand technique. 30 screws were placed on one side with their original experience. After learning the techniques mentioned in the study, 30 screws were placed on the other side. The specimens were examined by X-ray and CT, and the angles of the screw paths and the integrity of the pedicle were evaluated.ResultsThe angles of 120 subjects and 25 anatomical specimens show a gradually increasing trend. The differences among each segment were statistically significant (P < 0.05), but the difference in the same segment between the X-ray and the anatomical specimens was not statistically significant (P > 0.05). Furthermore, the differences in L1, L2, and L3 between the two genders were not statistically significant (P > 0.05). However, the angles were larger in female group than in male group in L4 and L5, and the differences were statistically significant (P < 0.05). The difference in the deviation rate of screw placement before and after the learning was statistically significant only in the L5 segment (P < 0.05). The difference in overall excellence rate was statistically significant (P < 0.05).ConclusionsThe measurement of the angle between the axis of the pedicle and the lateral margin of the isthmus on the lumbar can improve the accuracy of the lumbar sagittal screw angle.

Should planning of cervical pedicle screws be race specific? Computed tomography–based morphometric analysis

Introduction: The neurovascular surgical structures are protected by quantitative understanding of cervical pedicle morphology and aiding in better surgical outcome. Aim of the study is to do morphometric analysis of subaxial cervical pedicle by noncomputerized computed tomography (CT) scans. Materials and Methods: From 50 volunteers, a total of 500 cervical pedicles were evaluated using axial and sagittal CT scan. Five parameters such as outer pedicle width (OPW), inner pedicle width (IPW), pedicle height (PH), pedicle transverse angle (PTA) and pedicle axis length (PAL) were analyzed. Result: OPW, IPW, PH, and PAL show increase in values from C3 to C7, while PTA shows a decrease in value from C3 to C7. Conclusion: The cervical pedicle dimension of our study population was smaller than other studies carried out on Asian and European population. Hence, the planning for pedicle screw fixation should be race specific.

Application of the pedicle axis view in percutaneous screw placement for type III fracture dislocation of the sacroiliac joint

AimTo investigate the clinical application of axial view projection of the pedicle in percutaneous screw placement for type III fracture dislocation of the sacroiliac joint.MethodsPercutaneous sacroiliac screw fixation was performed in 29 patients with type III sacroiliac joint fractures under X-ray fluoroscopy (C-arm) using axial view projection of the pedicle after preoperative traction reduction and preoperative preparation. The study included 19 males and 10 females, aged 20 to 75 years old, with a mean age of 42.1 ± 3.4 years.ResultsThe total operative time ranged between 44 and 135 min, with a mean of 95.5 ± 9.4 min. The intraoperative fluoroscopy time ranged between 15 and 42 s, with a mean of 25 ± 4.7 s. The intraoperative blood loss ranged between 5 and 10 ml, with a mean of 7.1 ± 1.3 ml. According to the Matta scoring system, excellent outcomes were achieved in 25 cases, whereas good outcomes were achieved in 4 cases. Based on the definition by Neo et al., pedicle screw positions were categorized into four grades: grade 0 (33 screws), grade I (2 screws), grade II (2 screws), and grade III (0 screws). Excellent outcomes were achieved in 94.6% of Grade 0 and I screws. According to Majeed’s functional score, 21 cases achieved excellent outcomes, whereas 8 cases achieved good outcomes. The 29 patients were followed between 3 and 18 months, with a mean of 7.1 ± 1.2 months. All patients achieved anatomical reduction with accurate screw placement and successful healing of their fractures, with no cases of bone penetration or neurovascular injury.ConclusionAxial view imaging of the pedicle using fluoroscopy is a convenient and rapid fluoroscopy method for percutaneous screw placement for type III fracture dislocation of the sacroiliac joint, with a high rate of success, good safety, and short fluoroscopy time.

Perpendicular probing and screwing technique: A simple method for accurate pedicle screw placement based on the human internal reference frame for angle estimation.

The pedicle screw (PS) is widely used for spinal fixation surgery. However, PS malpositioning can cause critical complications; thus, the accuracy of ascertaining PS trajectory is paramount. This study aimed to demonstrate the accuracy and safety of a simple and cost-effective PS placement technique using a human internal reference frame for angle estimation. Ex vivo lumbar porcine spine samples were fixed to a wooden board with rostrocaudal and mediolateral rotational angles adjusted by two angle vises. PS entry points (EPs) were identified using clear anatomical vertebral landmarks. PS placement was performed on one side using the perpendicular probing and screwing technique (PPST), wherein the attitude angle of the sample was adjusted such that the longitudinal axis of the target pedicle was perpendicular to the ground. The pedicle probe and PS driver were manually maintained perpendicular to the ground during probing and PS placement. PS placement on the contralateral side was performed freehand as a control. Offsets between the preoperatively planned and implanted PS rotational angles measured using computed tomography for PPST and freehand method were analyzed. Pedicle wall penetration was also evaluated. The mean ± standard error of the medial rotational offsets was 5.83° ± 0.57° in the freehand group versus 2.89° ± 0.31° in the PPST group (p <0.001), and the rostrocaudal rotational offsets were 4.81° ± 0.65° in the freehand group versus 2.92° ± 0.45° in the PPST group (p = 0.01). The mean pedicle wall penetration distance was significantly reduced by PPST (0.28 ± 0.12 mm vs 0.80 ± 0.17 mm in the freehand group, p = 0.0071). Thus, PPST improved PS positioning accuracy, resulting in reduced pedicle wall penetration and increased PS placement safety. This simple technique is also potentially cost-effective for institutions without computer-assisted surgical systems.

The Classification of Axial Deformity in Patients with Basilar Invagination.

To summarize the variation types of the axis in patients with basilar invagination (BI), then propose a classification scheme of the axis deformity. From December 2013 to September 2020, 92 patients (male 42, female 50) who were diagnosed with BI were studied retrospectively. Based on the imaging data of CT, the width and height of the axis pedicle and the sagittal diameter of the lateral mass were measured in each patient. According to the development of axis pedicle and lateral mass, the types of axis variation were summarized, and then the classification scheme of axis deformity was put forward. All cases were analyzed and axis deformities were divided into four types. Type I: the axis is basically normal (53 cases, 57.6%). Type II: axis lateral mass is dysplasia (eight cases, 8.7%), which includes two subtypes: type IIA, the axis unilateral lateral mass is dysplasia (three cases); type IIB, the axis bilateral lateral masses are all dysplasia (five cases). Type III: axis pedicle is dysplasia (11 cases, 12%), which is subdivided into two subtypes: type IIIA, the axis unilateral pedicle is dysplasia (six cases); type IIIB, the axis bilateral pedicles are all dysplasia (five cases). Type IV: axis pedicle and lateral mass are all dysplasia (20 cases, 21.7%), this type contains the following four subtypes: type IVA, the unilateral axis pedicle and unilateral lateral mass (contralateral or ipsilateral) are all hypoplasia (four cases); type IVB, the unilateral axis pedicle and bilateral lateral masses are all hypoplasia (five cases); type IVC, the bilateral axis pedicles and unilateral lateral mass are all dysplasia (seven cases); type IVD, the bilateral axis pedicles and bilateral lateral masses are all dysplasia (four cases). The left and right abnormal lateral mass sagittal diameter (Type II) was (7.23 ± 1.39) mm and (5.96 ± 1.37) mm, respectively, the left and right abnormal pedicle width (Type III) was (2.61 ± 1.01) mm and (3.23 ± 0.66) mm, respectively, left and right abnormal pedicle height (Type III) was (5.43 ± 2.19) mm and (4.92 ± 1.76) mm, respectively. Moreover, the classification scheme has good repeatability and credibility. The classification about axis deformity could provide personalized guidance for axis screw placement in the BI and other upper cervical surgery, and axis screw placement errors would be effectively avoided.

The effect of axis pedicle and intra-axial vertebral artery on C 2 pedicle screw placement

To investigate the influence of axis pedicle and intra-axial vertebral artery (IAVA) alignment on C 2 pedicle screw placement by measuring the data of head and neck CT angiography. The axis pedicle diameter (D), isthmus height (H), isthmus thickness (T), and IAVA alignment types were measured in 116 patients (232 sides) who underwent head and neck CT angiography examinations between January 2020 and June 2020. Defined the IAVA offset direction by referencing the vertical line through the center of C 3 transverse foramen on the coronal scan, it was divided into lateral (L), neutral (N), and medial (M). Defined the IAVA high-riding degree by referencing the horizontal line through the outlet of the C 2 transverse foramen, it was divided into below (B), within (W), and above (A). The rate of pedicle stenosis, high-riding vertebral artery, and different IAVA types were calculated, and their relationships were analysed. Simulative C 2 pedicle screws were implanted by Mimics 19.0 software, and the interrelation among the rates of pedicle stenosis, high-riding vertebral artery, IAVA types, and vertebral artery injury were analyzed. The rate of C 2 pedicle stenosis was 33.6% (78/232), and the rate of high-riding vertebral artery was 35.3% (82/232). According to the offset direction and the degree of riding, IAVA was divided into 9 types, among which the N-W type (29.3%) was the most, followed by the L-W type (19.0%) and the L-B type (12.9%), accounting for 60.9%. The vertebral artery injury rate of simulative implanted C 2 pedicle screws was 35.3% (82/232). The vertebral artery injury rate in patients with pedicle stenosis and high-riding vertebral artery was significantly higher than that who were not ( P<0.001). The rate of pedicle stenosis, high-riding vertebral artery, and vertebral artery injury were significantly different among IAVA types ( P<0.001), and M-A type was the most common. Vertebral artery injury is more common in pedicle stenosis and/or high-riding vertebral artery and/or IAVA M-A type. Preoperative head and neck CT angiography examination has clinical guiding significance.

Comprehensive analysis of pedicle screw implantation in the C7 vertebra using computed tomography-based three-dimensional models

BackgroundFrom a biomechanical point of view, pedicle screws (PS) are better than other kinds of screws for implantation in the seventh cervical vertebra (C7). However, the application of PS is limited because of the high risk of severe complications. It is essential to define the optimal entry point and trajectory. The aim of this study was to comprehensively analyze the starting point and trajectory for C7 PS insertion using three dimensional (3D) models.MethodsOverall, 60 subjects aged 18 to 67 years old were included. All CT images were used to construct 3D computer models of the C7 vertebrae. A new coordinate system was established for the next evaluation. The pedicle axis was calculated with respect to the entire pedicle; then, the ideal entry point, screw diameter and length, sagittal angle and lateral angle were assessed.ResultsAll the ideal entry points were located at the medial superior to lateral notch (LN), and the mean distance between the entry point and LN was 5.86 ± 1.67 mm in the horizontal direction and 3.47 ± 1.57 mm in the vertical direction. The mean distance between the entry point and the middle point of the inferior edge of the C6 articular process (MP) was 0.74 ± 1.83 mm in the horizontal direction. The mean sagittal angle of the pedicle axis was 90.42°, and the mean pedicle transverse angle was 30.70°. The average diameter and length of the PS were 6.51 ± 0.76 mm and 31.58 ± 4.40 mm, respectively.ConclusionsThis study provided a novel method to calculate the ideal starting point and trajectory for C7 PS insertion. These measurements may be helpful for preoperative planning. It is recommended that 3D CT imaging is used preoperatively to carefully evaluate the anatomy of each individual.

A morphometric analysis of thoracolumbar vertebrae in goat by computed tomography.

The goat spine is widely used as an animal model for preclinical research in human medicine to test new spinal implants and surgical procedures. Therefore, precise morphometric data are needed. This study aims to provide morphometric data of the goat thoracolumbar vertebrae and to define the parameters/characteristics of the optimum implantation corridors for pedicle screws in the thoracolumbar spine in goat. Eleven 36-month-old adult alpine goats were included in this study, and a sample of 198 vertebrae was measured. Subsequently, transverse and sagittal images were obtained using a multi-detector-row helical computed tomography (CT) scanner. Measurements of the vertebral bodies (ventral body width VBW, ventral body depth VBD, ventral body height ventral VBHv, ventral body high dorsal VBHd, spinal canal depth SCD, spinal canal width SCW), pedicles (pedicle length PDL, pedicle width PDW, pedicle angle PA and pedicle axis length PAL), intervertebral disc (DT) and transverse process length (TPL) were performed with dedicated software. The vertebral bodies and the spinal canal were wider than deep, mostly evident in the lumbar region. The intervertebral discs were as much as 65.7% thicker in the lumbar spine than in the thoracic spine. The pedicles were longer than wide over the thoracic and lumbar spines. The insertion angles in pedicle were approximately 30° for the T2-T4 segment, 25° for the T5-T6 segment, 23° for the T6 to T11 segment, 20° for T11 to L3, 25° for L4 and 30° for L5 and L6. In conclusion, the generated data can serve as a CT reference for the caprine thoracolumbar spine and may be helpful in using the goat spine as an animal model for human spinal research.

Optimal screw positioning in cervical pedicles to avoid complications.

Cervical instability can be caused by a variety of factors, including trauma, tumors, or infection. The cervical transpedicular screw (CPS) is one of the most modern procedures for treating cervical instability. Despite the fact that numerous innovative techniques for CPS have been proposed, the appropriate screw entry points and screw directions have yet to be thoroughly established. The aim of this study is to determine the screw insertion angles and screw entry point distances based on reference points, pedicle axis lengths, and pedicle axis intersections for each vertebra from cervical (C) C2 to C7 in both right and left by gender and age groups. In this study, computed tomography (CT) images of patients who underwent cervical examination for any reason were evaluated retrospectively. A total of 100 patients (59 men and 41 females), ranging in age from 18 to 79 years (mean 43 years), were randomly selected for the study. Patients with a history of cervical pathology or surgery were excluded. CT images turned into 3D reconstructed images and density settings were made so that bone tissue could be best observed using OsiriX software. Pedicle axis length (PAL), pedicle transverse angle (PTA), pedicle sagittal angle (PSA), distance of screw entry point to lateral notch (DLN), distance of screw entry point to inferior articular process (DIAP), and pedicle axis intersections were measured. According to our findings, the optimal entry point should be 2-4 mm medial to the lateral notch and 8-12 mm superior to inferior articular process. PTA ranges between 30 to 45°, while PSA ranges between 11 to 15°. Except for the C2 pedicles, which were slightly shorter, the pedicle axis lengths (PAL) were similar from C3 to C7 in the total group. The intersection of the right and left pedicle axes was determined to be the most in C4 (51.21% in females and 72.88% in males). This study has shown that intersections of the pedicle axis must be considered in both genders, especially in C4. Standardizing optimal entry points and trajectories is crucial for improving the CPS technique's safety and effectiveness.

Pedicle Screw Plowing in Adolescent Idiopathic Scoliosis: How Common Is It and Is It a Problem?

Multicenter retrospective review. To calculate overall incidence of pedicle screw "plowing" in adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF). To identify risk factors for pedicle screw plowing and associated postoperative outcomes, including loss of correction and revision rate. Curve correction of AIS generates perpendicular stresses that can cause pedicle screws to lose alignment and "plow" through pedicles craniocaudally. We reviewed records of 1057 patients who underwent PSF for AIS from 2002 to 2015. Preoperative and first postoperative erect radiographs were evaluated by two observers to determine (1) presence of plowing and (2) subsequent loss of correction (LOC). Plowing was defined as more than 25° sagittal angulation compared with pedicle axis or entry of the most dorsal part of the screw outside the pedicle projection. LOC was defined as postoperative change in focal angulation of an instrumented spinal level, when in consensus of both reviewers. Bivariate analyses were performed (alpha = 0.05). Nineteen thousand five hundred sixty nine screws were assessed across our cohort of 1057 patients. Both observers agreed that 48 patients (4.5%) demonstrated plowing of more than or equal to one pedicle screw. For 72 screws (0.4%), both observers noted plowing, most commonly through the cranial cortex of the pedicle (65/72 screws) and at the lowest instrument vertebra (LIV) (17/72 screws). Factors associated with plowing included larger curves (P = 0.02); lower mean pedicle screw density (P = 0.0003); skeletal immaturity as measured by open triradiate cartilage (P = 0.04); and younger chronological age at time of surgery (P = 0.04). LOC occurred in 13 patients, most commonly at LIV (P < 0.0001). Revision rate for loss of screw fixation was higher in the plowing group (P = 0.003). Pedicle screw plowing occurred in 4.5% of AIS patients, especially in those skeletally immature and with decreased implant density. Plowing commonly occurred in the cranial direction and was associated with LOC, particularly at the LIV.Level of Evidence: 3.

Does intraoperative 3D navigation improve SpineJack vertebral augmentation in thoracic and lumbar compression fracture?

IntroductionThe aim of this retrospective study was to evaluate the effect of navigation on the positioning of the SpineJack implant in the treatment of thoracic and lumbar compression fractures. MethodsBetween January 2018 and December 2019, all patients operated on for thoracic or lumbar fracture using the SpineJack device in stand-alone were included in this single-center study. The positioning of the SpineJack implant was analyzed on axial CT views by measuring the angle between the axis of the pedicle and the axis of the final implant. The relationships between implant positioning and the use of navigation or fluoroscopy, pedicle dimensions and levels of injury were analyzed. Surgical time, radiation exposure, radiological findings and complications were assessed. ResultsOne hundred patients were included, for 103 fractured vertebrae and a total of 205 implants, 148 placed under standard fluoroscopy and 57 with the Surgivisio navigation system. For pedicle diameters≥5mm (165 implants), the positioning of the implant relative to the axis of the pedicle was significantly better in the navigation group: 2°±1.4° (range, 0–7°) in the fluoroscopy group versus 1.2°±1.1° (range, 0–5°) in the navigation group (p=0.04). There were no significant differences in reduction of vertebral kyphosis angle or mean operating time. Dose area product (DAP) was significantly higher with navigation: 4.43Gy.cm2 versus 0.47Gy.cm2 (p<0.001) and dose to the surgeon significantly lower: 0.5 versus 1.6μSv (p<0.001). No difference was found regarding complications. Subgroup analysis showed significantly greater operative time and patient irradiation in the fluoroscopy group when pedicle diameter was less than 5mm. ConclusionThis study demonstrates the interest of navigation for positioning the SpineJack implant with respect to the pedicle axis in vertebrae with pedicle diameter≥5mm. This study also confirmed the reliability of navigation and lower radiation dose to the surgeon, regardless of the fracture level. Navigation reduced operating time and patient irradiation for vertebrae with pedicle diameter<5mm. Level of evidenceIV; retrospective study.

Volvulus of the gallbladder: Beware of aberrant biliary anatomy

Gallbladder volvulus (GBV) is an uncommon differential in the acute surgical abdomen, which may incur significant morbidity if missed. Less than 500 cases have been reported in the literature, with few diagnosed pre-operatively. It is defined as the rotation of the gallbladder on its mesentery along the axis of the cystic pedicle, although cases of torsion of the gallbladder fundus itself have been reported. An 82-year-old lady presented with a worsening 5 day history of right upper quadrant pain with associated nausea, anorexia. She had worsening pain and noticed a 'lump' in her abdomen, along with subjective fevers. On examination, her abdomen was tender, with a non-pulsatile mass in the RUQ with voluntary guarding. The computed tomography Abdo-Pelvis revealed a distended gallbladder extended up to the pelvis with multiple gallstones. Stranding of fat around the gallbladder was noted, with wall thickening up to 7 mm at the fundus - with overall appearances consistent with acute cholecystitis. An open cholecystectomy was performed, with the intraoperative finding of GBV. There were multiple small arteries supplying the gallbladder, with no definitive cystic artery. The extra-hepatic biliary anatomy was aberrant with a long-cystic duct exiting through the cystic plate. Post-operatively recovery was uncomplicated. GBV is an important differential of RUQ pain, requiring immediate intervention. It is often misdiagnosed as cholecystitis. Imaging is variable in detecting GBV, and early surgical intervention remains the mainstay of both diagnosis and treatment. However, surgeons should beware that unrecognized aberrant biliary anatomy can result in higher morbidity.

Subaxial Cervical Pedicle Screw Placement With Direct Visualization of Pedicle Borders: 2-Dimensional Operative Video.

Pedicle screws provide superior fixation of the subaxial cervical spine to other techniques. However, a high degree of accuracy is required for safe placement given the proximity of pedicles to critical neurovascular structures. A variety of techniques are described to maximize accuracy, including freehand, fluoroscopy-guided, and neuronavigation-based methods. We present a technique for the placement of pedicle screws in the subaxial cervical spine using direct visualization of the pedicle in a patient who required an occipito-cervical fusion construct in the setting of a C2 chordoma. A laminotomy or laminectomy is performed laterally to allow for visualization of the medial, superior, and inferior walls of the pedicle. The entry point for screw placement is determined based on pedicle anatomy and is typically 1 to 2 mm lateral to the midpoint of the lateral mass, just below the base of the superior articulating process. Screw trajectory is determined by visualizing the pedicle borders and is aimed at the junction of the medial pedicle wall, with the posterior vertebral body down the pedicle axis. Tactile feedback (loss of resistance) is used to assess for a breach while drilling. The cannulation is then tapped, and the screw is placed in a standard fashion. Direct visualization of pedicle anatomy can be a useful adjunct to guide the safe placement of subaxial pedicle screws when superior fixation is required or when normal anatomy is distorted. The technique may be combined with fluoroscopic or navigation-based techniques to provide real-time anatomic guidance during screw placement. The patient provided informed, written consent for this procedure before surgery. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Computerized Tomographic Based Study of Thoracic Spine Morphology in Relevance to Pedicle Screw Fixation in Pakistani Population

Objective: To study the thoracic spine anatomy for accurate placement of pedicle screws using computerized tomography.&#x0D; Material and Methods: CT scans of 200 patients were included in our study. T1 to T12 vertebrae morphology was studied for each patient. Following measurements were taken, 1: Transverse pedicle width, 2 = Depth of anterior cortex along pedicle axis, 3 = Transverse pedicle angle, 4 = canal dimensions, 5 = vertebral body height anterior and posterior, 6 = mid vertebral body width.&#x0D; Results: Transverse pedicle width decreased from T1 (4.06 ± 0.50 mm) to T4 (3.72 ± 0.17 mm) and then gradually increases to T12 (6.08 ± 0.60 mm). Depth of the anterior vertebral cortex remained constant from T1 to T4 and gradually increases up to T12. Transverse pedicle angle remained constant from T1 to T4 with a maximum at T4 (23.39 ± 3.15 mm) and then gradually decreased to T12 (3.99 ± 2.16 mm). Anteroposterior (AP) canal dimensions were minimum at T7 (17.03 ± 1.01 mm) and maximum at T2 (21.2 ± 1.07 mm). Interpedicular (IPD) canal dimensions were minimum at T6 (19.18 ± 1.6 mm) and maximum at T3 (23.18 ± 1.2 mm). Anterior vertebral body height was minimum at T1 (16.9 ± 1.34 mm) and maximum at T12 (27.14 ± 1.34mm). Posterior vertebral body height was minimum at T1 (18.8 ± 1.13 mm) and maximum at T12 (29.76 ± 1.43 mm).&#x0D; Conclusion: A detailed anatomy of the thoracic spine is essential for surgical planning to decrease postoperative complications.

Subaxial Cervical Pedicular Screw Insertion via the Nonanatomic Axis: Technical Notes and Preliminary Clinical Report.

Retrospective study. To report the technical details of subaxial cervical pedicular screw insertion via the nonanatomic axis (nAA-CPS) and evaluate its clinical safety and accuracy. The nAA-CPS technique was performed in 21 patients. Preoperative and intraoperative management-related details are described, and a manipulation protocol is presented. Clinical outcomes were used to assess the safety and accuracy of screws was evaluated using postoperative computed tomography (CT) according to the pedicle perforation grading system, and the nonanatomic pedicle transverse angle (nPTA) and nonanatomic pedicle axis length (nPAL) were assessed based on pre- and postoperative CT images. According to "one constant entry point (EP) and two perpendicular trajectory angles" protocol, nAA-CPS was performed without much interference from the muscles. No intraoperative or postoperative neurovascular complications related to the technique were observed. Of the 112 inserted screws, 78 (69.64%) were assessed as grade 0, 24 (21.43%) as grade 1, 4 (3.57%) as grade 2 and 6 (5.36%) as grade 3. The overall rate of correct position (grades 0 and 1) was 91.07% (102/112), and the rate of malposition was 8.93% (10/112), including five screws implanted medially and the other five laterally. The nPTA was highly consistent on pre- and postoperative CT (P < .05), while postoperative nPAL was significantly shorter than preoperative nPAL (P > .05). Clinically, the accuracy and safety of nAA-CPS was similar to the traditional CPS technique. The protocol, derived from previous radiological studies and workshops, greatly helped standardize clinical manipulation; thus, nAA-CPS is a promising alternative to the traditional CPS.

Torsion of wandering spleen, splenectomy and autotransplantation of splenic slices

The aim of this research is to highlight the peculiarity of the incident, to discuss the decision for the transplant splenic slices, and to present the positive results of this approach. The case includes a 14-year-old girl who was presented with atypical abdominal pain last year. Ultrasound imaging showed an abdominal mass in the left lower abdomen. Following that, a CT was performed where the wandering spleen was imaged. Doppler control revealed relatively good blood flow, but partial spleen stems rotation while blood tests revealed thrombocytopenia. However, during the surgical procedure, the spleen appeared 2 ½ times veering the axis of the vascular pedicle. The decision to splenectomy was made due to the presence of small clots during palpation of the vasculature, the appearance of thrombocytopenia, and the technically inadequate splenopexy due to the large vascular pedicle. Partial spleen auto-transplantation on the omental was subsequently carried out. The follow up provided satisfactory results in size and function. The wandering spleen has difficulty in its clinical diagnosis. Visual inspection could document the diagnosis. The suggested treatment is splenopexy, but in the decision for splenectomy, as in this case, with evidence of viable splenic tissue, the successful autotransplantation of splenic slices reduces the risk of splenectomy complications, such as the post-splenectomy sepsis.