ObjectiveTo determine the entry point and screw implant technique in posterior pedicle screw fixation by anatomical measurement of adult dry samples of the axis so as to provide a accurate anatomic foundation for clinical application. MethodsA total of 60 dry adult axis specimens were selected for pedicle screws fixation. The entry point was 1-2 mm lateral to the crossing point of two lines: a vertical line through the midpoint of distance from the junction of pedicle medial and lateral border to lateral mass, and a horizontal line through the junction between the lateral border of inferior articular process and the posterior branch of transverse process. The pedicle screw was inserted at the entry point. The measurement of the anatomic parameters included the height and width of pedicle, the maximum length of the screw path, the minimum distance from screw path to spinal canal and transverse foramen, and the angle of pedicle screw. The data above were provided to determine the surgical feasibility and screw safety. ResultsThe width of upper, middle, and lower parts of the pedicle was (7.35±0.89), (5.50±1.48), and (3.97±1.01) mm respectively. The pedicle height was (9.94±1.16) mm and maximum length of the screw path was (25.91±1.15) mm. The angle between pedicle screw and coronal plane was (26.95±1.88)° and the angle between pedicle screw and transverse plane was (22.81±1.61)°. The minimum distance from screw path to spinal canal and transverse foramen was (2.72±0.83) mm and (1.98±0.26) mm respectively. ConclusionAccording to the anatomic research, a safe entry point for C2 pedicle screw fixation is determined according to the midpoint of distance from the junction of pedicle medial and lateral border to lateral mass, as well as the junction between the lateral border of inferior articular process and the posterior branch of transverse process, which is confirmed to be effectively and safely performed using the entry point and screw angle of the present study.
ObjectiveTo compare the fixation strength of optimum placed pedicle screw (OS) with re-directionally correctly placed pedicle screw (RS) following a violation of lateral pedicle. MethodsThirty fresh lumbar vertebrae (L1-5) were obtained from 6 pigs weighing 95-105 kg, male or female. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect screw path was created using direct visualization and fluoroscopy. A pedicle screw of 5 mm in diameter and 35 mm in length was placed with a digital torque driver (OS). On the other side, a lateral pedicle wall violation was created at the pedicle-vertebral body junction with a guide wire, a cannulated tap, and a pedicle probe. This path was then redirected into a correct position, developed, and instrumented with a 5-mm-diameter by 35-mm-long pedicle screw (RS). For each pedicle screw, the maximal torque, seating torque, screw loosening force, and post-loosening axial pullout were measured. Screw loosening and axial pullout were assessed using an MTS machine. ResultsMaximal insertion torque was (111.4±8.2) N·cm and (78.9±6.4) N·cm for OS and RS respectively, showing significant difference (Z=3.038, P=0.002). The seating torque was (86.3±7.7) N·cm and (59.7±5.3) N·cm for OS and RS respectively, showing significant difference (Z=2.802, P=0.005). The screw loosening force was (76.3±6.2) N and (53.0±5.8) N for OS and RS respectively, showing significant difference (Z=2.861, P=0.004). The post-loosening axial pullout force was (343.0±12.6) N and (287.0±10.5) N for OS and RS respectively, showing significant difference (Z=2.964, P=0.003). ConclusionCompared with OS, RS placement after a lateral wall violation shows significantly decreased maximal insertion torque, seating torque, screw loosening force, and post-loosening axial pullout. On this occasion, RS augmentation is a probable option for remediation.
Objective To compare the biomechanical properties of the anterior transpedicular screw-artificial vertebral body (AVB) and conventional anterior screw plate system (AP) in lower cervical spine by finite element study. Methods CT images (C1-T1) were obtained from a 38-year-old female volunteer. The models of intact C3-7 (intact group), AP fixation (AP group), and AVB fixation (AVB group) were established and analyzed by Mimics 14.0, Geomagic Studio 2013, and ANSYS 14.0 softwares. The axial force of 74 N and moment couple of 1 N·m were loaded on the upper surface and upper facet joint surfaces of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity and maximum equivalent stree of AP and AVB groups were recorded, and the range of motion (ROM) was also analyzed of 3 groups. Results The intact model of lower cervical spine (C3-7) was established, consisting of 286 382 elements and 414 522 nodes, and it was successfully validated with the previously reported cadaveric experimental data of Panjabi and Kallemeyn. The stress concentrated on the connection between plate and screw in AP group, while it distributed evenly in AVB group. Between AP and AVB groups, there was significant difference in maximum equivalent stress values under conditions of 74 N axial force, flexion, extension, and rotation. AVB group had smaller ROM of fixed segments and larger ROM of adjacent segments than AP group. Compared with intact group, whole ROM of the lower cervical spine decreased about 3°, but ROM of C3, 4 and C6, 7 segments increased nearly 5° in both AP and AVB groups. Conclusion As a new reconstruction method of lower cervical spine, AVB fixation provides better stability and lower risk of failure than AP fixation.
Objective To investigate short-term effectiveness of spinal navigation with the intra-operative three-dimensional (3D)-imaging modality in pedicle screw fixation for congenital scoliosis (CS). Methods Between July 2010 and December 2011, 26 patients with CS were treated. Of 26 patients, 13 patients underwent pedicle screw fixation using the spinal navigation with the intra-operative 3D-imaging modality (navigation group), while 13 patients underwent the conventional technique with C-arm X-ray machine (control group). There was no significant difference in gender, age, hemivertebra number and location, major curve Cobb angle, and Risser grade between 2 groups (P gt; 0.05). Operation time, operative blood loss, frequency of the screw re-insertion, and postoperative complication were observed. The pedicle screw position was assessed by CT postoperatively with the Richter’s standard and the correction of Cobb angle was assessed by X-ray films. Results All patients underwent the surgery successfully without major neurovascular complication. There was no significant difference in operation time, operative blood loss, and pedicle screw location between 2 groups (P gt; 0.05). A total of 58 screws were inserted in navigation group, and 3 screws (5.2%) were re-inserted. A total of 60 screws were inserted in control group, and 10 screws (16.7%) were re-inserted. There was significant difference in the rate of pedicle screw re-insertion between 2 groups (χ2=3.975, P=0.046). Patients of navigation group were followed up 6-24 months, and 6-23 months in control group. According to Richter’s standard, the results were excellent in 52 screws and good in 6 screws in navigation group; the results were excellent in 51 screws, good in 5 screws, and poor in 4 screws in control group. Significant difference was found in the pedicle screw position between 2 groups (Z= — 1.992, P=0.046). The major curve Cobb angle of 2 groups at 1 week and last follow-up were significantly improved when compared with preoperative value (P lt; 0.05), but there was no significant difference between 1 week and last follow-up (P gt; 0.05). No significant difference in correction rate of the major curve Cobb angle was found between 2 groups at last follow-up (t=0.055, P=0.957). Conclusion Spinal navigation with the intra-operative 3D-imaging modality can improve the accuracy of pedicle screw implantation in patients with CS, and effectually reduce the rate of screw re-insertion, and the short-term effectiveness is satisfactory.
Objective To investigate the effectiveness of posterior intrasegmental fixation with pedicle screw-lamina hook system and bone grafting for lumbar spondylolysis. Methods Between January 2005 and October 2009, 22 patients with lumbar spondylolysis underwent posterior intrasegmental fixation with pedicle screw-lamina hook system and bone grafting. There were 19 males and 3 females with an average age of 18.4 years (range, 12-26 years). The main symptom was low back pain with an average disease duration of 16 months (range, 8-56 months). The visual analogue scale (VAS) was 6.0 ± 1.2 and Oswestry disability index (ODI) was 72.0% ± 10.0% preoperatively. The X-ray films showed bilateral spondylolysis at L4 in 9 cases and at L5 in 13 cases. The range of motion (ROM) at upper and lower intervertebral spaces was (11.8 ± 2.8)°and (14.1 ± 1.9)°, respectively. ResultsAll incisions healed by first intention. All patients were followed up 12-45 months (mean, 25 months). Low back pain was significantly alleviated after operation. The VAS score (0.3 ± 0.5) and ODI (17.6% ± 3.4%) were significantly decreased at last follow-up when compared with preoperative scores (P lt; 0.05). CT showed bone graft fusion in the area of isthmus defects, with no loosening or breaking of internal fixator. At last follow-up, the lateral flexion-extension X-ray films of the lumbar spine showed that the ROM at upper and lower intervertebral spaces was (12.3 ± 2.1)°and (13.5 ± 1.7)°, respectively; showing significant differences when compared with preoperative values (P lt; 0.05). Pain at donor site of iliac bone occurred in 1 case, and was cured after pain release treatment. ConclusionThe posterior intrasegmental fixation with pedicle screw-lamina hook system and bone grafting is a reliable treatment for lumbar spondylolysis, having a high fusion rate, low complication rate, and maximum retention of lumbar ROM.
Objective To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis. Methods Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/ min. Results With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P lt; 0.05). In CPS group, the energy absorption gradually decreased (P lt; 0.05); in EPS group, significant difference was found between other different BMD levels (P lt; 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P gt; 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P lt; 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P lt; 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P gt; 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P gt; 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P lt; 0.05). Conclusion Compared with CPS, the EPS can significantly improve the fixation strength, especially in patients with osteopenia or osteoporosis.
【Abstract】 Objective To explore the clinical application and outcomes of preoperative second measurement of three-dimensional (3-D) CT reconstruction data for scoliosis orthopedic surgery. Methods Between August 2006 and March 2008, 11 patients with severe rigid scoliosis received surgery treatment, including 4 males and 7 females with an average age of 17.2 years (range, 15-19 years). Preoperative second measurement of 3-D CT reconstruction data was conducted to guide the surgery， including the angle and width of pedicle, the entry point, and the choice of screws whose lengths and diameters were suitable. A total of 197 pedicle screws were implanted. The operation time， blood loss， postoperative nerve function，and Cobb’s angles at sagittal and coronal view were all recorded， and the postoperative CT scan was performed to assess the accuracy of pedicle screw insertion according to Andrew classification. Results Pedicle screws were implanted within 1-11 minutes (mean, 5.8 minutes), and the blood loss was 450-2 300 mL (mean, 1 520 mL). The postoperative X-ray films showed the correction rates of Cobb’s angle were 68.5% in coronal view and 55.5% in sagittal view. The accuracy of pedicle screw insertion was rated as grade I in 77 screws (39.1%)，grade II in 116 screws (58.9%)， and grade III in 4 screws (2.0%) according to postoperative CT scan. All 11 cases were followed up 14 months to 2 years without any complications. Conclusion Preoperative second measurement of 3-D CT reconstruction data can make the surgery process easy and accurate in treatment of severe scoliosis.
【Abstract】 Objective To investigate the clinical significances of the thoracic pedicle classification determined by inner cortical width of pedicle in posterior vertebral column resection (PVCR) with free hand technique for the treatment of rigid and severe spinal deformities. Methods Between October 2004 and July 2010, 56 patients with rigid and severe spinal deformities underwent PVCR. A total of 1 098 screws were inserted into thoracic pedicles at T2-12. The inner cortical width of the thoracic pedicle was measured and divided into 4 groups: group 1 (0-1.0 mm), group 2 (1.1-2.0 mm), group 3 (2.1-3.0 mm), and group 4 (gt; 3.1 mm). The success rate of screw-insertion into the thoracic pedicles was analyzed statistically. A new 3 groups was divided according to the statistical results and the success rate of screw-insertion into the thoracic pedicles was analyzed statistically again. And statistical analysis was performed between different types of thoracic pedicles classification for pedicle morphological method by Lenke. Results There were significant differences in the success rate of screw-insertion between the other groups (P lt; 0.008) except between group 3 and group 4 (χ2=2.540，P=0.111). The success rates of screw-insertion were 35.05% in group 1, 65.34% in group 2, and 88.32% in group 3, showing significant differences among 3 groups (P lt; 0.017). According to Lenke classification, the success rates of screw-insertion were 82.31% in type A, 83.40% in type B, 80.00% in type C, and 30.28% in type D, showing no significant differences (P gt; 0.008) among types A, B, and C except between type D and other 3 types (P lt; 0.008). In the present study, regarding the distribution of different types of thoracic pedicles, types I, II a, and II b thoracic pedicles accounted for 17.67%, 16.03%, and 66.30% of the total thoracic pedicles, respectively. The type I, II a, and II b thoracicpedicles at the concave side accounted for 24.59%, 21.13%, and 54.28%, and at the convex side accounted for 10.75%, 10.93%, and 78.32%, respectively. Conclusion A quantification classification standard of thoracic pedicles is presented according to the inner cortical width of the pedicle on CT imaging: type I thoracic pedicle, an absent channel with an inner cortical width of 0-1.0 mm; type II thoracic pedicle, a channel, including type IIa thoracic pedicle with an inner cortical width of 1.1-2.0 mm, and type IIb thoracic pedicle with an inner cortical width more than 2.1 mm. The thoracic pedicle classification method has high prediction accuracy of screw-insertion when PVCR is performed.
【Abstract】 Objective To investigate the effectiveness of surgical treatment for discogenic low back pain (DLBP) by minimally invasive transforaminal lumbar interbody fusion (TLIF) combined with unilateral pedicle screw fixation (UPSF). Methods Between March 2006 and July 2009, 57 patients with single-level DLBP were treated by minimally invasive TLIF combined with UPSF, including 27 males and 30 females with an average age of 45.6 years (range, 38-61 years) and a disease duration of 3.8 years (range, 9 months to 11 years). The involved segments included L2，3 in 2 cases, L3，4 in 5 cases, L4，5 in 29 cases, and L5, S1 in 21 cases. The operative time, incision length, intraoperative blood loss, postoperative drainage volume, hospitalization times, fusion rate, and complications were observed. The effectiveness were evaluated through Oswestry disability index (ODI) and visual analogue score (VAS), and the operative outcomes were compared in different groups classified according to various pressures of the contrast medium and sensitivities to discoblock after inducing consistent pain. Results The operation time, incision length, blood loss, postoperative drainage volume, and hospitalization times were (84.6 ± 37.4) minutes, (3.4 ± 0.6) cm, (132.5 ± 23.2) mL, (58.7 ± 21.4) mL, and (6.5 ± 0.8) days, respectively. All patients were followed up 2 years and 2 months to 5 years and 4 months (mean, 3.2 years). At last follow-up, ODI and VAS scores were significantly improved when compared with preoperative scores (P lt; 0.05). The effectiveness according to ODI were excellent in 27 cases, good in 22 cases, fair in 6 cases, and poor in 2 cases, with an excellent and good rate of 86.0%. All patients acquired b interbody fusion. At last follow-up according to ODI and VAS scores, better results were found in patients of low-pressure sensitive group and high-sensitive discoblock group (P lt; 0.05). Conclusion Minimally invasive TLIF combined with UPSF is reliable for DLBP with minimal surgical trauma, less paravertebral tissue injury, and fewer complications, but the indications for operation must be strictly followed. Patients being sensitive to low-pressure or high-sensitive to discoblock can achieve better surgical results.
【Abstract】 Objective To study the effectiveness of computer assisted pedicle screw insertion in osteoporotic spinalposterior fixation. Methods Between December 2009 and March 2011, 51 patients underwent pedicle screw fixation using the computer assisted navigation (navigation group), while 41 patients underwent the conventional technique (traditional group). All patients had osteoporosis under the dual-energy X-rays absorptiometry. There was no significant difference in age, gender, bone mineral density, involved segment, preoperative complications, and other general status between 2 groups (P gt; 0.05). The amount of blood loss, the operation time, the rate of the pedicle screw re-insertion, and the postoperative complication were observed. The state of the pedicle screw location was assessed by CT postoperatively with the Richter’s classification and the fusion state of the bone graft was observed using three-dimensional (3-D) CT scans during follow-up. Results A total of 250 screws were inserted in navigation group, and 239 were inserted successfully at first time while the other 11 screws (4.4%) were re-inserted. A total of 213 screws were inserted in traditional group, and 190 were successful at first time while 23 screws (10.8%) were re-inserted. There was significant difference in the rate of screws re-insertion between 2 groups (χ2=6.919, P=0.009). Both the amount of blood loss and the operation time in navigation group were significantly less than those in traditional group (P lt; 0.05). According to Richter’s classification for screw location, the results were excellent in 240 screws, good in 10 screws innavigation group; the results were excellent in 191 screws, good in 21 screws, and poor in 1 screw in traditional group. Significant difference was noticed in the screw position between 2 groups (χ2=7.566, P=0.023). The patients were followed up (7.8 ± 1.5) months in navigation group and (8.7 ± 1.5) months in traditional group. No loosening, extraction, and breakage of the pedicle screw occurred in navigation group, and all these patients had successful fusion within 6 months postoperatively. While in traditional group, successful fusion was shown in the other patients by 3-D CT, except the absorption of bone graft was found in only 1 patient at 6 months after operation. And then, after braking by adequate brace and enhancing the anti-osteoporotic therapy, the bone graft fused at 9 months postoperatively. Conclusion The computer assisted navigating pedicle screw insertion could effective reduce the deviation or re-insertion of the screws, insuring the maximum stabil ity of each screw, mean while it can reduce the exposure time and blood loss, avoiding complication. The computer assisted navigation would be a useful technique which made the pedicle screw fixation more safe and stable in patients with osteoporosis.