Objective To evaluate the biomechanical stability of a newly-designed Y type pedicle screw (YPS) in osteoporotic synthetic bone. Methods The osteoporotic synthetic bone were randomly divided into 3 groups (n=20). A pilot hole, 3.0 mm in diameter and 30.0 mm in deep, was prepared in these bones with the same method. The YPS, expansive pedicle screw (EPS), and bone cement-injectable cannulated pedicle screw (CICPS) were inserted into these synthetic bone through the pilot hole prepared. X-ray film examination was performed after 12 hours; the biomechanical stability of YPS, EPS, and CICPS groups was tested by the universal testing machine (E10000). The test items included the maximum axial pullout force, the maximum running torque, and the maximum periodical anti-bending. Results X-ray examination showed that in YPS group, the main screw and the core pin were wrapped around the polyurethane material, the core pin was formed from the lower 1/3 of the main screw and formed an angle of 15° with the main screw, and the lowest point of the inserted middle core pin was positioned at the same level with the main screw; in EPS group, the tip of EPS expanded markedly and formed a claw-like structure; in CICPS group, the bone cement was mainly distributed in the front of the screw and was dispersed in the trabecular bone to form a stable screw-bone cement-trabecular complex. The maximum axial pullout force of YPS, EPS, and CICPS groups was (98.43±8.26), (77.41±11.41), and (186.43±23.23) N, respectively; the maximum running torque was (1.42±0.33), (0.96±0.37), and (2.27±0.39) N/m, respectively; and the maximum periodical anti-bending was (67.49±3.02), (66.03±2.88), and (143.48±4.73) N, respectively. The above indexes in CICPS group were significantly higher than those in YPS group and EPS group (P<0.05); the maximum axial pullout force and the maximum running torque in YPS group were significantly higher than those in EPS group (P<0.05), but there was no significant difference in the maximum periodical anti-bending between YPS group and EPS group (P>0.05). Conclusion Compared with EPS, YPS can effectively enhance the maximum axial pullout force and maximum rotation force in the module, which provides a new idea for the design of screws and the choice of different fixation methods under the condition of osteoporosis.
ObjectiveTo explore the efficacy of percutaneous pedicle screw internal fixation and minimally invasive lateral small incisions lesion debridement and bone graft fusion via dilated channels in the treatment of lumbar tuberculosis.MethodsThe clinical data of 22 cases of lumbar tuberculosis treated with percutaneous pedicle screw internal fixation combined with dilated channels with minimally invasive lateral small incision lesion debridement and bone graft fusion between January 2016 and June 2018 were retrospectively analyzed. There were 12 males and 10 females, with an average age of 47.5 years (range, 22-75 years). The affected segments were L2, 3 in 5 cases, L3, 4 in 8 cases, and L4, 5 in 9 cases, with an average disease duration of 8.6 months (range, 4-14 months). Preoperative neurological function was classified according to the American Spinal Injury Association (ASIA), with 3 cases of grade C, 9 cases of grade D, and 10 cases of grade E. The operation time, intraoperative blood loss, and postoperative complications were recorded. At preoperation, 3 months after operation, and last follow-up, the C reactive protein (CRP) and erythrocyte sedimen- tation rate (ESR) were tested to evaluate tuberculosis control; the pain visual analogue scale (VAS) score was used to evaluate the recovery of pain, and the Oswestry disability index (ODI) was used to evaluate the function recovery of the patient’s lower back; the kyphosis Cobb angle was measured, and the loss of Cobb angle (the difference between the Cobb angle at last follow-up and 3 months after operation) was calculated. At last follow-up, the ASIA classification was used to evaluate the recovery of neurological function, and the effectiveness was evaluated according to the modified MacNab standard.ResultsThe operation time was 110-148 minutes (mean, 132.8 minutes) and the intraoperative blood loss was 70-110 mL (mean, 89.9 mL). Two patients experienced fat liquefaction of the incision and delayed healing; the incisions of the remaining patients healed by first intention. All patients were followed up 18-24 months, with an average of 21.3 months. All bone grafts achieved osseous fusion, the pedicle screws were fixed in reliable positions, without loosening, displacement, or broken rods. There was no recurrence of tuberculosis. The ESR, CRP, VAS scores, ODI scores, and kyphosis Cobb angle of the affected segment at 3 months after operation and last follow-up were significantly improved (P<0.05); there were no significant differences between at last follow-up and 3 months after operation (P>0.05), and the loss of Cobb angle was (0.6±0.5)°. The patient’s neurological function recovered significantly. At last follow-up, the ASIA grades were classified into 1 case with grade C, 1 case with grade D, and 20 cases with grade E, which were significantly improved when compared with preoperative grading (Z=−3.066, P=0.002). According to the modified MacNab standard, 16 cases were excellent, 3 cases were good, 2 cases were fair, and 1 case was poor. The excellent and good rate was 86.4%.ConclusionPercutaneous pedicle screw internal fixation combined with dilated channels with minimally invasive lateral small incisions lesion debridement and bone graft fusion has the advantages of less bleeding, less trauma, and faster recovery, which is safe and effective in the treatment of lumbar tuberculosis.
ObjectiveTo investigate reliability and short-term effectiveness of axis laminar screws for reducible atlantoaxial dislocation (RAAD).MethodsA clinical data of 41 patients with RAAD who were admitted between February 2013 and February 2018 and met the inclusion criteria was retrospectively analyzed. The atlases in all patients were fixated by lateral mass screws, and the axes were fixed by laminar screws in 13 cases (LS group) and by pedicle screws in 28 cases (PS group). There was no significant difference in gender, age, and preoperative Japanese Orthopedic Association (JOA) score between the two groups (P>0.05). The effectiveness was estimated by post-operative JOA score; and the accuracy of the axis screw, atlantoaxial bone graft fusion, and the fixation stability were examined by X-ray film and CT.ResultsAll incisions healed by first intention. All patients were followed up 12-17 months (mean, 13.8 months) in LS group and 12-20 months (mean 14.1 months) in PS group, and the difference in follow-up time was not significant (Z=−0.704, P=0.482). At last follow-up, JOA scores were 13.9±1.6 in LS group and 14.3±1.8 in PS group, which significantly improved when compared with the pre-operative scores in the two groups (t=−9.033, P=0.000; t=−15.835, P=0.000); while no significant difference was found between the two groups (t=−0.630, P=0.532). Twenty-five screws of 26 screws in LS group and 54 screws of 56 screws in PS group were implanted accurately, with no significant difference in the accuracy of the axis screw between the two groups (Z=−0.061, P=0.951). All patients obtained atlantoaxial bone graft fusion, except 1 case in PS group. There was no significant difference in the atlantoaxial bone graft fusion between the two groups (Z=−0.681, P=0.496).ConclusionFor RAAD, Axis laminar screws can maintain the atlantoaxial primary stability and had a good short-term effectiveness. So, it could be an alternative and reliable technique for axis screw.
Accurate placement of pedicle screws is a key factor of spinal surgery. Investigation of a new real-time intra-operative monitoring method is an important area of clinical application research which makes a contribution to planting pedicle screw accurately. Porcine spines were chosen as experimental objects.The changes of reduced scattering coefficient (μ's) along normal puncture path, medial perforation path and lateral perforation path were measured and studied. A conclusion is drawn that there are two distinct peaks throughout the puncture process, appearing at the junction of cancellous bone and cortical bone, at the beginning and at the end, respectively. The reduced scattering coefficient is proved to be a good monitoring factor which can identify whether the screw is about to reach the critical position of the spine puncture. Moreover, the variation provides an important reference for spinal surgical navigation process.
Objective To investigate the effectiveness of computer-assisted and robot-assisted atlantoaxial pedicle screw implantation for the treatment of reversible atlantoaxial dislocation (AAD). MethodsThe clinical data of 42 patients with reversible AAD admitted between January 2020 and June 2023 and met the selection criteria were retrospectively analyzed, of whom 23 patients were treated with computer-assisted surgery (computer group) and 19 patients were treated with Mazor X spinal robot-assisted surgery (robot group). There was no significant difference in gender, age, T value of bone mineral density, body mass index, etiology, and preoperative Japanese Orthopaedic Association (JOA) score, Neck Dysfunction Index (NDI) between the two groups (P>0.05). The operation time, screw implantation time, intraoperative blood loss, hand and wrist radiation exposure, and complications were recorded and compared between the two groups. Gertzbein classification was used to evaluate the accuracy of screw implantation. JOA score and NDI were used to evaluate the function before operation, at 3 days after operation, and at last follow-up. At last follow-up, the status of screws and bone fusion were observed by neck three-dimensional CT. Results The operation time and hand and wrist radiation exposure of the computer group were significantly longer than those of the robot group (P<0.05), and there was no significant difference in the screw implantation time and intraoperative blood loss between the two groups (P>0.05). All patients were followed up 11-24 months, with an average of 19.6 months. There was no significant difference in the follow-up time between the two groups (P>0.05). There was no significant difference in the accuracy of screw implantation between the two groups (P>0.05). Except for 1 case of incision infection in the computer group, which improved after antibiotic treatment, there was no complication such as nerve and vertebral artery injury, screw loosening, or breakage in the two groups. The JOA score and NDI significantly improved in both groups at 3 days after operation and at last follow-up (P<0.05) compared to those before operation, but there was no significant difference between the two groups (P>0.05). At last follow-up, 21 patients (91.3%) in the computer group and 18 patients (94.7%) in the robot group achieved satisfactory atlantoaxial fusion, and there was no significant difference in the fusion rate between the two groups (P>0.05). ConclusionComputer-assisted or robot-assisted atlantoaxial pedicle screw implantation is safe and effective, and robotic navigation shortens operation time and reduces radiation exposure.
ObjectiveTo compare the safety and accuracy of pedicle screw placement assisted by robot system with freehand pedicle screw placement in upper thoracic surgery.MethodsBetween December 2017 and December 2019, 39 cases with upper thoracic pedicle screw internal fixation were included in the study, including 19 cases in robot group (group A, robot assisted pedicle screw placement) and 20 cases in freehand group (group B, freehand pedicle screw placement). There were 104 screws implanted in group A and 108 screws in group B. There was no significant difference in age, gender composition, body mass index, disease type, number of screws implanted, and segmental distribution between the two groups (P>0.05). The operation time, intraoperative blood loss, and postoperative drainage were recorded and compared between the two groups. CT scan was performed in all patients at 2 days after operation to evaluate the screw accuracy based on the Gertzbein-Robbins grading standard.ResultsThe operation time of group A was significantly longer than that in group B (t=2.759, P=0.009). There was no significant difference in intraoperative blood loss and postoperative drainage between the two groups (t=−0.796, P=0.431; t=−0.814, P=0.421). At 2 days after operation, according to Gertzbein-Robbins grading standard, the accuracy of pedicle screw implantation in group A were grade A in 94 screws, grade B in 9 screws, and grade C in 1 screw; and in group B were grade A in 72 screws, grade B in 26 screws, grade C in 9 screws, and grade D in 1 screw; the difference between the two groups was significant (Z=4.257, P=0.000). The accuracy rate of group A was 99.04%, and that of group B was 90.74%, showing significant difference (χ2=7.415, P=0.006).ConclusionCompared with traditional freehand pedicle screw placement, robot-assisted pedicle screw placement significantly improves the accuracy and safety of screw placement without increasing the bleeding and postoperative drainage.
ObjectiveTo evaluate the clinical efficacy of domestic minimally-invasive percutaneous screw system for thoracolumbar fractures without neurological damage. MethodsSixty patients suffering from unstable thoracolumbar fractures without obvious neurologic deficits treated from January 2011 to April 2012 were studied retrospectively. The patients were divided into two groups:group A (domestic minimally-invasive percutaneous screw system) and group B (imported minimally-invasive percutaneous screw system). Perioperative parameter, pre-and post-operative imaging indexes, visual analog scale (VAS) and modified MacNab evaluation standard were studied for comparison. ResultsAll the patients were followed up from 6 to 18 months with an average of (12.2±3.0) months. The Cobb's angle and anterior height of the fracture vertebral body changed significantly in each group (P<0.05). There was no significant difference in incision size, surgical time, postoperative improvement of Cobb's angle, anterior height of the fracture vertebral body and accuracy of pedicle screw placement between the two groups (P>0.05). ConclusionDomestic minimally-invasive percutaneous screw system is reliable with minimal invasion, which is comparable to imported minimally-invasive percutaneous screw system.
Objective To explore the clinical effect of PSIS-A robot-assisted percutaneous screw in the treatment of thoracolumbar fracture. Methods Patients with thoracolumbar fracture who were hospitalized in Mianyang Orthopedic Hospital between August 2022 and January 2024 and required percutaneous pedicle screw f ixation were selected. Patients were divided into robot group and free hand group by random number table. Operative time, intraoperative bleeding, intraoperative radiation dose and time, implant accuracy rate, small joint invasion rate, Visual Analogue Scale score for pain and other indexes were compared between the two groups. Results A total of 60 patients were included. Among them, there were 28 cases in the robot group and 32 cases in the free hand group. On the third day after surgery, the Visual Analogue Scale score of the robot group was better than that of the free hand group (P=0.003). Except for intraoperative bleeding and radiation frequency (P>0.05), the surgical time, average nail implantation time, and intraoperative radiation dose in the robot group were all lower than those in the free hand group (P<0.05). The accuracy and excellence rate of nail planting in the robot group were higher than those in the free hand group (94.6% vs. 84.9%; χ2=7.806, P=0.005). There was no statistically significant difference in the acceptable accuracy rate (96.4% vs. 91.1%; χ2=3.240, P=0.072) and the incidence of screw facet joint invasion (7.2% vs.14.1%; χ2=3.608, P=0.058) between the two groups. Conclusion The application of PSIS-A type robot assisted percutaneous minimally invasive pedicle screw fixation in the treatment of thoracolumbar fr actures is promising.
Objective To biomechanically compare the maximum pull-out strengths among two pedicle screws and three salvage techniques using poly methylmethacrylate (PMMA) augmentation in osteoporotic sacrum, and to determine which PMMA augmentation technique could serve as the salvage fixation for loosening sacral pedicle screws. Methods Eleven sacra were harvested from fresh adult donated cadavers, aged from 66 to 83 years (average 74.4 years) and included 5 men and 6 women. Radiography was used to exclude sacra that showed tumor or inflammatory or any other anatomic abnormal ities. Following the measurement of bone mineral density, five sacral screw fixations were sequentially establ ished on the same sacrum as follows: unicortical pedicle screw (group A), bicortical pedicle screw (group B), unicortical pedicle screw with the traditional PMMA augmentation (group C), ala screw with the traditional PMMA augmentation (group D), and ala screw with a kyphoplasty-assisted PMMA augmentation technique (group E). According to the sequence above, the axial pull-out test of each screw was conducted on a MTS-858 material testing machine. The maximum pull-out forces were measured and compared. The morphologies of PMMA augmented screws after being pulled-out were also inspected. Results The average bone mineral density of 11 osteoporotic specimens was (0.71 ± 0.08) g/cm2 . By observation of the pull-out screws, groups C, D, E showed perfect bonding with PMMA, and group E bonded more PMMA than groups C and D. The maximum pull-out forces of groups A, B, C, D, and E were (508 ± 128), (685 ± 126), (846 ± 230), (543 ± 121), and (702 ± 144) N, respectively. The maximum pull-out strength was significantly higher in groups B, C, and E than in groups A and D (P lt; 0.05), and in group C than in groups B and E (P lt; 0.05). There was no significant difference in pull-out strength between groups A and D, and between groups B and E (P gt; 0.05). Conclusion For sacral screw fixation of osteoporotic patients with bone mineral density more than 0.7 g/cm2, bicortical pedicle screw could acquire significantly higher fixation strength than the unicortical. Once the loosening of pedicle screw occurs, the traditional PMMA augmentation or ala screw with kyphoplasty-assisted PMMA augmentation may serve as a suitable salvage technique.
ObjectiveTo discuss the security and effectiveness of fixing the unstable region of sagittal injured unit symmetrically with pedicle screws combined with bone graft fusion for treating thoracolumbar fractures.MethodsA series of 65 patients with a single level thoracolumbar fracture between November 2011 and November 2015 were included in the study. There were 41 males and 24 females with an average age of 36.7 years (range, 23-60 years). The fracture segments included T7 1 case, T9 in 2 cases, T10 in 4 cases, T11 in 8 cases, T12 in 14 cases, L1 in 19 cases, L2 in 13 cases, L3 in 3 cases, and L4 in 1 case. According to AO classification, there were 34 cases classified as type A, 27 cases type B, and 4 cases type C. The neurological function was evaluated by American Spinal Injury Association (ASIA) grade score, there were 1 case at grade A, 2 cases grade B, 6 cases grade C, 15 cases grade D, and 41 cases grade E. The thoracolumbar injury severity score (TLICS) was 4 in 9 cases, 5 in 29 cases, 6-8 in 23 cases, 9-10 in 4 cases. The time form injury to operation was 2-12 days (mean, 5.3 days). The fractured vertebra, along with the superior and inferior discs were defined as a injured unit and divided into three parts on the sagittal position: region Ⅰ mainly including the superior disc, cephalic 1/3 of injured vertebra, and posterior ligamentous complex as to oppose; region Ⅱ mainly including the middle 1/3 of injured vertebra, pedicles, lamina, spinous process, and supraspinal ligament; region Ⅲ mainly including the inferior disc, caudal 1/3 of injured vertebra, and posterior ligamentous complex as to oppose. The unstable region was defined as the key injured region of the vertebra. Pedicle screws were fixed symmetrically and correspondingly with bone grafting to treat thoracolumbar fractures. The neurological status, ratio of anterior body height, and sagittal Cobb angle were collected at preoperation, immediate after operation, and last follow-up to evaluate surgical and clinical outcomes.ResultsAll patients accepted operation safely and were followed up 12-24 months (mean, 17.3 months). Cerebrospinal fluid leakage occurred in 3 patients, and cured by symptomatic treatment. There was no complications such as loosening, displacement, and breakage of internal fixator. Bony fusion was achieved in all patients at 10-13 months (mean, 11.4 months) after operation. At last follow-up, according to ASIA grading, 1 case was grade A, 1 grade B, 3 grade C, 9 grade D, and 51 grade E, showing significant difference when compared with preoperative data (Z=–2.963, P=0.014). The ratio of anterior body height at preoperation, immediate after operation, and last follow-up were 53.2%±6.8%, 91.3%±8.3%, 89.5%±6.6% respectively; and the sagittal Cobb angle were (16.3±8.1), (2.6±7.5), (3.2±6.8)° respectively. The ratio of anterior body height and the sagittal Cobb angle at immediate after operation and at last follow-up were significantly improved when compared with preoperative values (P<0.05), but no significant difference was found between at immediate after operation and at last follow-up (P>0.05).ConclusionIt is safe and reliable to treat thoracolumbar fractures under the principle of fixing the unstable region of injured unit symmetrically with pedicle screws combined with bone grafting.