Biomechanical Study on Atlantoaxial Dislocation Combined with Basilar Invagination by Different Posterior Internal Fixation Methods / 医用生物力学

Objective To investigate biomechanical differences of two posterior occipitocervical internal fixation techniques for treating basilar invagination with atlantoaxial dislocation (BI-AAD). Methods Intra-articular cage + posterior occipital plate+C2 pedicle screw (Cage+C2PS+OP), and intra-articular cage+C1 lateral mass screw+C2PS (Cage+C1LMS+C2PS) models were established based on occipitocervical CT data of the BI-AAD and clinical operation scheme, and the stability of atlantoaxial joint and stress distribution characteristics of C2 endplate and implanted instruments under different motion states were analyzed. Results Compared with the Cage+C1LMS+C2PS model, the atlantoaxial range of motion ( ROM) under flexion, extension, lateral bending and axial rotation in the Cage+C2PS+OP model were reduced by 5. 26% , 33. 33% , 43. 75% , -5. 56% , and stress peak of screw-rod fixation system were reduced by 47. 81% , 60. 90% , 48. 45% , 39. 14% , respectively. Under two internal fixation modes, stresses of C2 endplate and cage were mainly distributed on the compressive side during the motion, and both the screw-bone interface and the caudal side of screw subjected to large loading. Conclusions Two internal fixation methods could provide similar stability. However, the stress concentration of screw-rod system was more obvious and the possibility of screw loosening and fracture was greater under Cage+ C1LMS+C2PS fixation.

Design and application of fulcrum screws for atlantoaxial dislocation / 中国组织工程研究

BACKGROUND: Atlantoaxial dislocation often needs surgery for reduction, and posterior screw-rod fixation fusion is the most commonly used surgery. However, the current screw-rod fixation system often increases the reduction effect by increasing the degree of curvature of connecting rod, causing great difficulty of placing rod, which increases the probability of spinal cord injury. OBJECTIVE: To evaluate the preliminary results of fulcrum screws for atlantoaxial dislocation. METHODS: From January 2017 to December 2018,11 patients with atlantoaxial dislocation were selected from General Hospital of Southern Theater Command of PLA, including 4 males and 7 females, at the age of 8-51 years. All patients were treated with posterior screw-rod fixation fusion: Conventional posterior cervical screws were implanted on both sides of the atlas and pivot screws were implanted on both sides of the axis. Atlantodental interval and Japanese Orthopaedic Association scores were recorded before and after operation. Patients were followed up and underwent X-ray and CT to estimate reduction, fixation and bone graft fusion. This study was approved by the Ethics Committee of General Hospital of Southern Theater Command of PLA. RESULTS AND CONCLUSION: (1) Eleven patients underwent operations successfully without vertebral artery or spinal nerve injury. (2) All patients were followed up for 3-12 months, with an average of 6 months. The symptoms of neck pain and neurological dysfunction were improved in varying degrees. All patients obtained atlantoaxial bone fusion, with an average fusion time of 6 months. (3) At postoperative 1 week, X-ray and CT images showed that atlantoaxial reduction was satisfactory and internal fixation was in good position. (4) Atlantodental interval reduced from preoperatively (6.8±1.5) mm to postoperatively (2.4±0.9) mm (f=17.854, P=0.000). Japanese Orthopaedic Association score increased from preoperatively (14.1±1.3) to postoperatively (15.9±0.9) (f=-10, P=0.000). (5) No complication occurred during follow-up, without recurrence or dislocation. (6) These results showed that using fulcrum screw in posterior screw-rod fixation fusion has an effective reduction for treating atlantoaxial dislocation and its preliminary clinical effects are satisfactory.

A Comparative Study between Pedicle Screw Instrumentation with Posterolateral Fusion and Pedicle Screw Instrumentation with Interbody Fusion in Patients of Lumbar Spondylolisthesis

Background: Many different treatment modalities have been advocated by different authors from time to time for lumbarspondylolisthesis. Many cases, the condition can be treated conservatively. However, when the symptoms persist, surgeryneeds to be performed. The principle of underlying surgery includes stabilization of the slipping vertebrae. Various operativemethods encompassing this principle include stabilization with pedicle screw fixation and fusion which can either posterolateralor interbody fusion, anterior lumbar interbody fusion, posterior lumbar interbody fusion, or transforaminal lumbar interbodyfusion. The objective of this study was to compare the surgical efficacy in terms of stability and fusion achieved using pediclescrew-rod instrumentation with posterolateral fusion and pedicle screw-rod instrumentation with interbody fusion in lumbarspondylolisthesis and to study THE functional and clinical recovery using the Revised Oswestry Disability Index score.Materials and Methods: A prospective study was carried out to compare the clinical and radiological outcomes between Pediclescrew-rod instrumentation with either posterolateral fusion and interbody fusion after adequate decompression in patient oflumbar spondylolisthesis. All patients as per the inclusion criteria were admitted, underwent surgery between March 2010 andMarch 2012, and were included in the study.Results: The total of 50 patients was included in our study. Both male and female patients were equally distributed in both thegroups, wherein postreolateral fusion had 13 female patients and those with interbody fusion had 13 male patients. Our studyshows marked improvement in Revised Oswestry Disability score postoperatively with good-to-excellent results in both thegroups. We achieved good solid radiological fusion earliest on the 3rd month in both the groups with good stability.Conclusion: Our results showed similar clinical and functional outcome in both the groups with no significant statistical differencefound. However, we conclude that in cases where reduction is required and there is instability affecting the three column ofspine interbody fusions with pedicle screws-rod instrumentation provide a more solid mechanical construct.

Therapeutic observation of subcutaneous pedicle screw-rod system with modified placement for Tile B pelvic fractures / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the feasibility and therapeutic effect of subcutaneous pedicle screw-rod system with modified placement in treatment of Tile B pelvic fractures.</p><p><b>METHODS</b>From June 2014 to August 2015, 14 patients with Tile B pelvic fractures were treated by subcutaneous pedicle screw-rod system with modified placement in the anterior inferior iliac spine and pubic tubercle. There were 8 males and 6 females, aged from 23 to 65 years with an average of 42 years. Operative time, intraoperative blood loss, fracture healing and postoperative complication were observed and clinical effects were evaluated by Matta reduction standard and Majeed score.</p><p><b>RESULTS</b>All patients were followed up from 8 to 15 months with an average of 10.5 months. Operative time was 25 to 45 min with an average of 32 min;intraoperative blood loss was 10 to 35 ml with an average of 18 ml. All fractures got primary healing and healed time was 9 to 14 weeks with an average of 12.5 weeks. No postoperative incision infection, internal fixation failure and ectopic ossification were found, 4 cases occurred unilateral lateral femoral cutaneous nerve injury and 1 case occurred unilateral femoral nerve paralysis, but all restored finally. According to Matta criteria, reduction was excellent in 7 cases, good in 5 cases, fair in 2 case. According to Majeed score system, the functional evaluation at last follow-up was excellent in 5 cases, good in 7 cases, fair in 2 cases with the average score of 81.50±8.05.</p><p><b>CONCLUSIONS</b>Subcutaneous pedicle screw-rod system with modified placement in the anterior inferior iliac spine and pubic tubercle have advantages of strong reduction, less trauma and complications, and is a promising surgical method in the treatment of Tile B pelvic fractures.</p>

Treatment of single segment lumbar degenerative disease with Quadrant assisted MIS-TLIF single side pedicle screw system / 中国综合临床

Objective To investigate the clinical efficacy of unilateral small incision Quadrant channel assisted MIS?TLIF unilateral pedicle screw fixation system in the treatment of degenerative lumbar disease. Methods From January 2011 to December 2013,a total of 56 cases with low back and leg pain were selected in the People′s Hospital of Dongguan,including 25 cases with lumbar disc herniation,18 cases with lumbar tube stenosis,10 cases with discogenic low back pain,2 cases of recurrence after posterior lumbar spine surgery,1 case of recurrence after transforaminal endoscopic surgery. Unilateral pedicle screw fixation was performed in the treatment of MIS?TLIF with expandable pipeline system. VAS and Oswestry dysfunction index scoring system( ODI) were used to evaluate of pain and functional recovery in patients with preoperative and postoperative pain and functional recovery,the Suk method was used to observe the bone graft fusion. Results There were 5 cases of non operative side waist back pain after operation,and the waist circumference and anti?inflammatory pain relief were improved after treatment. One case of postoperative subcutaneous fat liquefaction, was cured by dressing change. One patient with recurrence of MED intraoperatie cerebrospinal fluid leakage,was cured after treatment by the bed,dehydration and others. Other complications such as infection,screw loosening, nerve root injury and other complications had no found. After 1 month,the VAS score from preoperative ( 6. 82 ±0. 92) points fell to (1. 95±0. 55) points,ODI score from preoperative (35. 21±2. 73) points fell to (10. 05 ±1. 72) points, significantly improved compared with the preoperative, the differences were statistically significant( t=36. 775,65. 858,P<0. 05) ,based on the fusion of Suk judgment method,2 cases of patients with possible fusion,the rest were fusion. Conclusion Unilateral small incision under the quadrant assisted MIS?TILF unilateral pedicle nail stick system has obvious advantages in treatment of degenerative lumbar spine disease,as long as we choose to suitable cases and most patients can obtain satisfactory results.

Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration

STUDY DESIGN: The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. PURPOSE: To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel cross-link instrumentation, and to determine the effect of the cross-links. OVERVIEW OF LITERATURE: Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. METHODS: Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Student's t-tests. RESULTS: The spinous process group required a significantly greater pullout force for construct failure than the control group (p=0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p<0.001 and p=0.003, respectively). However, there was no difference between the control and cross-link groups. CONCLUSIONS: A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and flexion-compression testing compared to un-cross-link constructs. This configuration provided more resistance to middle-column damage under flexion-compression testing than conventional cross-link configuration.

Biomechanics effect of screw-rod internal fixation for Tile B2 pelvic fractures / 医用生物力学

Objective To investigate the validity of screw-rod system for fixing pelvic fractures by comparing the biomechanical behaviors from using screw-rod system or steel plate for fixing Tile B2 type pelvic fractures. Methods The finite element models of normal pelvis including ligaments, and Tile B2 fractured pelvis fixed by different screw-rod fixations (2 screws at fractured side, 3 screws at fractured side and at healthy side), and steel plate fixation were established. The vertical load (500 N) was applied on the upper terminal plate of the first body of the sacrum to simulate pelvis load during double-leg standing, single-leg standing and sitting. The displacement and stress distributions on normal pelvis and fractured pelvis with screw-rod fixation or with steel plate fixation were compared and analyzed. Results Both the screw-rod system and steel plate could effectively fix the fractured pelvis, and the fixation models showed similar displacement and stress distribution as normal pelvis. The largest displacement of fractured pelvis with 3-screw fixation on the diseased side was smallest under each working condition, and its stress level was also obviously lower than that of the other internal fixation models. During double-leg standing, compared with 2 screws fixation, 3 screws at healthy side fixation, and steel plate fixation, the Von Mises stress for 3 screws at fractured side fixation was reduced by 30.4%, 20.8%, 20.3%; during single-leg standing, the Von Mises stress for 3 screws at fractured side fixation was reduced by 31.8%,25.4%,18.5%; during sitting, the Von Mises stress for 3 screws at fractured side fixation is reduced by -6.5%,28.0%,61.1%,respectively. Conclusions The screw-rod system can fix Tile B2 pelvic fracture effectively, especially for 3-screw fixation on the fractured side. The results can provide the theory basis for clinical treatment of pelvic fracture.

Posterior Internal Fixation with Pedicle Screw Rod System for Upper Cervical Vertebra Injury：16 Cases Report / 中国康复理论与实践

Objective To observe the feasibility of posterior internal fixation with pedicle screw rod system for upper cervical vertebra injury. Methods 16 patients with upper cervical vertebra injury accepted posterior pedicle screw system internal fixation were reviewed. Re-sults Venous plexus behind C2 damaged in operation in a case, who needed a microscope for hemostasis. No complication, such as neurologi-cal symptoms worse, cerebrospinal fluid leakage, hematoma and infection of incision happened post operation. The neurological symptoms improved 81.8%in all the 7 cases who complained before operation. No complication was found in the follow-up 3 to 18 months after dis-charge. Their activities of upper cervical was basically unaffected. Conclusion Posterior internal fixation with pedicle screw rod system can provide stable support for patients with upper cervical injury.

Posterior Internal Fixation with Pedicle Screw Rod System for Upper Cervical Vertebra Injury: 16 Cases Report / 中国康复理论与实践

@#Objective To observe the feasibility of posterior internal fixation with pedicle screw rod system for upper cervical vertebra injury. Methods 16 patients with upper cervical vertebra injury accepted posterior pedicle screw system internal fixation were reviewed. Results Venous plexus behind C2 damaged in operation in a case, who needed a microscope for hemostasis. No complication, such as neurological symptoms worse, cerebrospinal fluid leakage, hematoma and infection of incision happened post operation. The neurological symptoms improved 81.8% in all the 7 cases who complained before operation. No complication was found in the follow-up 3 to 18 months after discharge. Their activities of upper cervical was basically unaffected. Conclusion Posterior internal fixation with pedicle screw rod system can provide stable support for patients with upper cervical injury.

The Comparison of the Results Between AO Internal Fixator (Long lever-arm) and Screw-Rod System (Short lever-arm) Through Posterior Approach in Unstable Thoracolumbar Fractures / 대한척추외과학회지

STUDY DESIGN: Prospective study. OBJECTIVES: To analyze the outcome of posterior reduction and fixation with the AO internal fixator and with the screw-rod system in unstable thoracolumbar fractures and to investigate differences in effectiveness between the two methods. SUMMARY OF LITERATURE REVIEW: In unstable thoracolumbar fractures, fixation with the AO internal fixator is an effective method for posterior reduction. However, the results of correction are quite variable. MATERIALS AND METHODS: We analyzed 51 patients with unstable thoracolumbar fractures who underwent correction through posterior approach between 1997 and 2003. We divided the patients into two groups: Patients in Group A (25 cases) were treated with the AO internal fixator, and patients in Group B (26 cases) were treated with the screw-rod system. We added transpedicular bone grafts for 17 patients in Group A. We evaluated correction of deformity (anterior and posterior height of vertebral body, sagittal index, disc height), loss of correction, spinal canal clearance, and neurological recovery. RESULTS: Comparing correction of deformity, we saw better results in Group A than in Group B in regards to sagittal index and anterior height of vertebral body. However, we saw a higher degree of correction loss in the anterior height of the vertebral body in Group A. We grafted autogenous bone into the fracture site by transpedicular approach for 17 patients in Group A. We saw less correction loss in the anterior vertebral body height and sagittal index. In regard to spinal canal clearance, we saw better results in Group A (18%) than in Group B (10%). As for neurological recovery, we could not find any statistically significant difference between the two groups. CONCLUSIONS: Through an operative procedure, we could achieve better results in restoration of anterior vertebral height and canal clearance with the AO internal fixator system. Further study is necessary to keep the reduced state of vertebral height.

Early Results from Posterior Cervical Fusion with a Screw-Rod System

PURPOSE: We performed 65 cases of posterior fusion surgery for cervical and/or high thoracic lesions using a polyaxial screw-rod system. PATIENTS AND METHODS: A total of 486 screws were implanted in 65 patients. RESULTS: Fixation of the screws was carried out over an average of 2.9 spinal segments. Upon evaluation by postoperative CT scans, twelve (2.5%) screws had suboptimal trajectories but two of these revealed radiculopathy in one patient and required screw repositioning. No vascular sequelae resulted. There has been no segmental motion in any of the cases to date. As for other complications, there was one case of dural tearing and two cases of lateral mass fractures. There were no infections or other wound healing problems or hardware failures. No patients had neurological deterioration after surgery. There were statistically significant improvements in the mean Neck Disability Index (NDI) scores and Visual Analogue Scale (VAS) scores in the preoperative and late postoperative follow-up evaluations. Although further studies are required to establish the long-term results of fusion rates and clinical outcomes. CONCLUSION: We cautiously suggest that the posterior polyaxial screw-rod system can be safely used as a primary or additional fusion method in this risky region. The successful and safe use of this method is dependent on a precise preoperative surgical plan and tactics for ensuring safe screw fixation.

Clinical Experiences and Usefulness of Cervical Posterior Stabilization with Polyaxial Screw-Rod System

OBJECTIVE: The objective of this study is to investigate the safety, surgical efficacy, and advantages of a polyaxial screw-rod system for posterior occipitocervicothoracic arthrodesis. METHODS: Charts and radiographs of 32 patients who underwent posterior cervical fixation between October 2004 and February 2006 were retrospectively reviewed. Posterior cervical polyaxial screw-rod fixation was applied on the cervical spine and/or upper thoracic spine. The surgical indication was fracture or dislocation in 18, C1-2 ligamentous injury with trauma in 5, atlantoaxial instability by rheumatoid arthritis (RA) or diffuse idiopathic skeletal hyperostosis (DISH) in 4, cervical spondylosis with myelopathy in 4, and spinal metastatic tumor in 1. The patients were followed up and evaluated based on their clinical status and radiographs at 1, 3, 6 months and 1 year after surgery. RESULTS: A total of 189 screws were implanted in 32 patients. Fixation was carried out over an average of 3.3 spinal segment (range, 2 to 7). The mean follow-up interval was 20.2 months. This system allowed for screw placement in the occiput, C1 lateral mass, C2 pars, C3-7 lateral masses, as well as the lower cervical and upper thoracic pedicles. Satisfactory bony fusion and reduction were achieved and confirmed in postoperative flexion-extension lateral radiographs and computed tomography (CT) scans in all cases. Revision surgery was required in two cases due to deep wound infection. One case needed a skin graft due to necrotic change. There was one case of kyphotic change due to adjacent segmental degeneration. There were no other complications, such as cord or vertebral artery injury, cerebrospinal fluid leak, screw malposition or back-out, or implant failure, and there were no cases of postoperative radiculopathy due to foraminal stenosis. CONCLUSION: Posterior cervical stabilization with a polyaxial screw-rod system is a safe and reliable technique that appears to offer several advantages over existing methods. Further biomechanical testings and clinical experiences are needed in order to determine the true benefits of this procedure.

Surgical Treatment of Unstable Thoracolumbar Fractures with Posterior Approach / 대한정형외과학회잡지

PURPOSE: To analyze the results of posterior reduction with AO internal fixator or screw-rod system in thoracolumbar fracture and to find an adequate method of treatment. MATERIALS AND METHODS: We analyzed 40 cases of unstable thoracolumbar fractures who were operated with posterior approach without additional anterior approach. All cases were divided into two groups by the instrument used: Group A (25 cases) with AO internal fixator and Group B (15 cases) with screw-rod system. They were classified according to AO classification. RESULTS: There was no significant difference in correction and maintenance of sagittal index among types of AO classification except neurological recovery which was better in Type A. AO internal fixator had better results than screw-rod system in correction and maintenance of sagittal index, but no difference in neurological recovery. Eleven cases had more than 5 degrees of correction loss at final follow-up. In these cases, we found several findings; decreased vertebral body height, decreased disc height, bony collapse around screw at superior segment, metal loosening between rod and screw and metal breakage of screw. CONCLUSIONS: We concluded that AO internal fixator was good for the posterior reduction of thoracolumbar fracture in this study. But we think that continuous follow-up and further study are needed.