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.
目的 评价微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折的中期临床疗效。 方法 2002年9月－2007年9月，采用微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折30例。其中男16例，女14例;年龄18～65岁，平均39.8岁。骨折节段:胸11者3例， 胸12者13例， 腰1者12例， 腰者22例。所有骨折按AO分型，均为A3型。受伤至手术时间6 h～6 d，平均45 h。分析术后影像学指标、疼痛评分及功能障碍指数。 结果 患者均获随访，随访时间3～9年，平均5.2年。术后各时间点伤椎前缘高度及后凸Cobb角均较术前明显恢复（P＜0.01）。术后伤椎高度随随访时间延长逐渐下降，后凸Cobb角逐渐增大。取出内固定物后、术后2年、末次随访时动力位X线片上骨折椎体前后相对滑移距离分别为（1.9 ± 0.3）、（2.1 ± 0.2）、（2.1 ± 0.3）mm，两两比较差异无统计学意义（P＞0.05）。术后1、2年及末次随访时疼痛视觉模拟评分分别为（2.5 ± 1.2）、（2.5 ± 1.1）、（2.4 ± 1.3）分，两两比较差异无统计学意义（P＞0.05）。末次随访时Denis腰痛分级：P1级13例，P2级12例，P3级5例。功能障碍指数为（11.4 ± 3.1）分，获优23例、良5例、可2例。 结论 单纯微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折中期临床效果满意，脊柱稳定性良好。Objective To mid-term efficacy of the technique of minimally invasive pedicle screw fixation on thoracolumbar burst fracture. Methods From September 2002 to September 2007, 30 patients were treated with minimally invasive pedicle screw fixation for thoracolumbar fracture. There were 16 males and 14 females with the mean age of 39.8 years (range,18-65 years). The injured level of was T11 in 3 cases, T12 in 13 cases, L1 in 12 cases, and L2 in 2 cases. The type of thoracolumbar fractures of all the patients was A3 according to AO classification. The during from injury to operation was 6 hours to 6 days with an average of 45 hours. The index of image and pain and disability index were evaluated after operation. Results All patients were followed up for 3 to 9 years with the mean of 5.2 years. Their average sliding distance after operation for removing internal fixation was (1.9 ± 0.3), and (2.1 ± 0.2) mm 2 years after the operation and (2.1 ± 0.3) mm at the latest follow-up. There was no significant difference (P＞0.05). Their average score was (2.51 ± 1.2) 1 year after the operation, was (2.42 ± 1.1) 2 year after the operation, and was (2.36 ± 1.3) at the latest follow-up (P＞0.05). According to Denis score system to evaluate index of lumbago, there was P1 in 13 cases, P2 in 12 cases, and P3 in 5 cases. The score of Oswestry Disability Index (ODI) was 11.4 ± 3.1 at the latest follow-up. Twenty-one cases gotexcellent therapeutic result, five cases got good and two were moderate. Conclusions Minimally invasive pedicle screw fixation for the treatment of thoracolumbar burst fracture provide satisfactory clinical results. The vertebral body and adjacent vertebral body have a good stability.
目的 评价微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折的中期临床疗效。 方法 2002年9月－2007年9月，采用微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折30例。其中男16例，女14例;年龄18～65岁，平均39.8岁。骨折节段:胸11者3例， 胸12者13例， 腰1者12例， 腰者22例。所有骨折按AO分型，均为A3型。受伤至手术时间6 h～6 d，平均45 h。分析术后影像学指标、疼痛评分及功能障碍指数。 结果 患者均获随访，随访时间3～9年，平均5.2年。术后各时间点伤椎前缘高度及后凸Cobb角均较术前明显恢复（P＜0.01）。术后伤椎高度随随访时间延长逐渐下降，后凸Cobb角逐渐增大。取出内固定物后、术后2年、末次随访时动力位X线片上骨折椎体前后相对滑移距离分别为（1.9 ± 0.3）、（2.1 ± 0.2）、（2.1 ± 0.3）mm，两两比较差异无统计学意义（P＞0.05）。术后1、2年及末次随访时疼痛视觉模拟评分分别为（2.5 ± 1.2）、（2.5 ± 1.1）、（2.4 ± 1.3）分，两两比较差异无统计学意义（P＞0.05）。末次随访时Denis腰痛分级：P1级13例，P2级12例，P3级5例。功能障碍指数为（11.4 ± 3.1）分，获优23例、良5例、可2例。 结论 单纯微创椎弓根钉内固定技术治疗胸腰椎爆裂骨折中期临床效果满意，脊柱稳定性良好。Objective To mid-term efficacy of the technique of minimally invasive pedicle screw fixation on thoracolumbar burst fracture. Methods From September 2002 to September 2007, 30 patients were treated with minimally invasive pedicle screw fixation for thoracolumbar fracture. There were 16 males and 14 females with the mean age of 39.8 years (range,18-65 years). The injured level of was T11 in 3 cases, T12 in 13 cases, L1 in 12 cases, and L2 in 2 cases. The type of thoracolumbar fractures of all the patients was A3 according to AO classification. The during from injury to operation was 6 hours to 6 days with an average of 45 hours. The index of image and pain and disability index were evaluated after operation. Results All patients were followed up for 3 to 9 years with the mean of 5.2 years. Their average sliding distance after operation for removing internal fixation was (1.9 ± 0.3), and (2.1 ± 0.2) mm 2 years after the operation and (2.1 ± 0.3) mm at the latest follow-up. There was no significant difference (P＞0.05). Their average score was (2.51 ± 1.2) 1 year after the operation, was (2.42 ± 1.1) 2 year after the operation, and was (2.36 ± 1.3) at the latest follow-up (P＞0.05). According to Denis score system to evaluate index of lumbago, there was P1 in 13 cases, P2 in 12 cases, and P3 in 5 cases. The score of Oswestry Disability Index (ODI) was 11.4 ± 3.1 at the latest follow-up. Twenty-one cases gotexcellent therapeutic result, five cases got good and two were moderate. Conclusions Minimally invasive pedicle screw fixation for the treatment of thoracolumbar burst fracture provide satisfactory clinical results. The vertebral body and adjacent vertebral body have a good stability.
Objective To review the progress of the pedicle screw augmentation technique by bone cement. Methods Recent literature about the pedicle screw augmentation technique by bone cement was reviewed and analysed. The characters were summarized. Results Pedicle augmentation technique includes the augmentation of ordinary solid pedicle screw and hollow pedicle screw. Both types could increase the fixation strength and gain satisfactory clinical results. Bone cement leakage had a certain incidence rate, but most of cases were asymptom. Conclusion Bone cement augmentation of pedicle screw is an effective and safe internal fixation for poor bone condition.
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 assess the effectiveness of single-level lumbar pedicle subtraction osteotomy for correction of kyphosis caused by ankylosing spondylitis. Methods Between July 2006 and July 2010, 45 consecutive patients with kyphosis caused by ankylosing spondylitis underwent single-level pedical subtraction osteotomy. There were 39 males and 6 females with an average age of 36.9 years (range, 21-59 years). The average disease duration was 18.6 years (range, 6-40 years). All patients had low back pain, fatigue, abnormal gaits, and disability of looking and lying horizontally. Radiological manifestations included sacroiliac joints fusion, bamboo spine, pelvic spin, and kyphosis. Cervical spine was involved in 30 patients; thoracolumbar spine was affected in 15 patients. Results Wound hydrops and dehiscence occurred in 1 case, and was cured after debridement; primary healing of incision was obtained in the other patients. Two patients had abdominal skin blisters, which were cured after magnesium sulfate wet packing. Forty-two patients were followed up 24-74 months (mean, 30 months). All osteotomy got solid fusion. The average bony fusion time was 6.8 months (range, 3-12 months). All patients could walk with brace and looked or lied horizontally postoperatively. The Scoliosis Research Society-22 Patient Questionnaire (SRS-22) score, T1-S1 kyphosis Cobb angle, L1-S1 lordosic Cobb angle, sagittal imbalance distance, and chin-brow vertical angle at 1 week and last follow-up were significantly improved when compared with those at preoperation (P lt; 0.05), but no significant difference was found between at 1 week and last follow-up (P gt; 0.05). Conclusion Single-level pedicle subtraction osteotomy has satisfactory effectiveness for the correction of kyphosis caused by ankylosing spondylitis.
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.