| With the development of social economy and the coming of aging society,the number of elderly patients is increasing,and the incidence of spinal degenerative disease is getting higher and higher.Most of patients are elderly people with poor surgical tolerance,and because of a wide range of degenerative hyperplasia,the operation is more difficult.Due to the appearance of internal fixation,the surgical effect has been improved and the postoperative complications have been reduced.However,the fixation associated complications makes surgeons think about better and more reasonable method to insert the screws.There are various methods of fixation and no matter which fixation the basis is the local anatomical marks and the relative position of anatomy.The measurement of the anatomical markers and relative position before or during the surgery is beneficial to the improvement of the accuracy of the screw placement and the reduction of postoperative complications.Posterior cervical lamina decompression and lateral mass screw fixation as one of the posterior cervical surgery,has satisfactory outcomes on the treatment of multistage cervical spondylotic myelopathy.The strength in the lateral mass screw was lower than that in cervical pedicle when inserted in the cervical spine,but the strength in the lateral mass screw could provide the enough stability for cervical surgery.However the lateral mass screw is safer,easier to insert and the complications are more infrequent.Because of these advantages,lateral mass screws have become the one of the most co mmonly used fixation in posterior cervical surgery.Roy Camille first reported the practice of lateral mass screws in clinical and put forward the method of screw insertion.After that,Magerl,Anderson and An introduced the method of lateral mass screws placement,respectively.Vertebral artery and nerve root injuries are two serious iatrogenic complications caused by improperplacement of the lateral mass screws.Because of the anatomical differences between individuals or the anatomical structure differences of each vertebra of the same individual,the placement of lateral mass screws should also be individualized.The same angle and direction sometimes are not appropriate when applied to all patients or all vertebrae.So we put forward our individualized method of inserting the lateral mass screws to avoid the situation.The lumbar pedicle screw,as a kind of high strength instrumentation,can provide i mmediate stable fixation.Lumbar decompression and fusion surgery with the pedicle screws can effectively prevent segmental instability and reduce the risk of palindromia.Since the lumbar pedicle screw was first reported by Harrington for its application,it had been widely used in various types of lumbar surgery.Pedicle screws could provide the stability of the three columns and have an irreplaceable position in some operations and diseases.There are important nerve roots passing through the inside and below the lumbar pedicle.When pedicle screws are misplaced,they may irritate the nerve root and lead to pedicle screw related complications,which may need revision surgery when the symptoms are severe.There are some placement techniques that are widely used including Roy-Camille technique,Magerl technique and Weinstein technique.Because of the anatomical differences between individuals or the anatomical structure differences of each vertebra of the same individual,the placement of lumbar pedicle screws should also be individualized.So we put forward our individualized method of inserting the lumbar pedicle screws to avoid the situation.Part 1 The study on the anatomy of the cervical and lumbar screwsObjective: Our purpose was to provide anatomical evidence for the placement of lumbar pedicle screws and cervical lateral mass screws by measuring the preoperative anatomic structures and related angles of lumbar vertebrae and cervical vertebrae on x-rays and CT scans.Methods: From January 1,2017,30 consecutive cervical spondylosis patients with preoperative lumbar CT scans,X-rays and with neurologic symptoms were included in this study.The anatomical data of the lateral massin the cervical spine and the pedicle in the lumbar spine were measure using the Synapse system.Cervical spine measurement: anatomical data was measured in each vertebra in C3-7: 1)cervical canal transverse diameter;2)transverse diameter of transverse foramen and the measurements were on both left and right sides;3)the distance between the medial cortex of transverse foramen and the lateral cortex of the cervical canal,and the measurements were on both left and right sides;4)the distance between the lateral cortex of lateral mass and the lateral wall of the transverse foramen,and the measurements were on both left and right sides.Lumbar spine measurement:anatomical data was measured in each vertebra in L1-5 on x-ray: 1)pedicle height;2)the angle between the connecting line of upper and lower facet joints and the posterior edge of the vertebral body.Anatomical data was measured in each vertebra in L1-5 on 1-mm CT scans: 1)pedicle width and the measurements were on both left and right sides.2)When the entry point was on the outer edge of the superior facet joint,the entry angle was measured.That was the angle between tangent of vertebral outer edge from outer edge of the superior facet joint and tangent of cervical canal outer edge from outer edge of the superior facet joint;3)When the entry point was on the root of the processus transverses,the entry angle was measured.That was the angle between tangent of vertebral outer edge from the root of the processus transverses and tangent of cervical canal outer edge from the root of the processus transverses.Results: No statistical difference was found in transverse diameter of the cervical spinal canal between C3-7(P=0.731).The transverse diameter of C3-6 transverse foramen were similar,while the transverse diameter of C7 transverse foramen was significantly lower than that of other vertebras.The transverse diameter of left transverse foramen was larger than that of the right side except for C7 vertebra.The medial cortex of transverse foramen was medial to the lateral cortex of the cervical canal in C3-6 vertebral body.The transverse foramen of the C4 vertebral body is the most medial vertebrae than the others.From C4 to the upper or lower vertebral body,the distance betweenmedial cortex of transverse foramen and the lateral cortex of the cervical canal was gradually increasing.Only the medial cortex of C7 transverse foramen was lateral to the lateral cortex of the cervical canal.The distance between lateral cortex of lateral mass and lateral cortex of transverse process was increasing from C3 to C5,while that distance was rapidly decreasing at C6 and C7 vertebrae.The lumbar pedicle height was similar in L1-5 on the x-ray,and the maximum width of the pedicle occurs on the L5 vertebra,gradually increasing from L1 to L5.The width of the pedicle of the lumbar vertebrae is less than the height.The angle between connecting line of upper and lower facet joints and the posterior edge of the vertebral body was limited in 5degree,and the average angle was around 1.5 degrees.The entry angle was smaller when entry point was on the outer edge of the superior facet joint than on the root of the processus transverses no matter which vertebral body.No matte entry point was on the outer edge of the superior facet joint or on the root of the processus transverses,the minimum value of entry angle appeared in the L1 and the max value of entry angle appeared in the L5 vertebra.Part 2 Individualized strategy for posterior cervical lateral mass screw placementObjective: New strategies of cervical lateral mass screw placement was proposed based on individual and intraoperative anatomic landmarks and preoperative imaging measurement.X-ray and 1 mm CT scans were used to evaluate the screw position postoperatively.Patients were followed up to evaluate the clinical outcomes by different kinds of questionnaires.Methods: From July 2014 to March 2015,24 patients with multisegmental cervical spondylotic myelopathy who underwent with C3-C6 cervical posterior laminectomy decompression and lateral mass screw fixation were included in the current study.The lateral mass screws were inserted using our technique according to the analysis of preoperative imaging data and the anatomical landmarks during the operation.The position of the lateral mass screws and the curvature of the cervical spine were measured by X-ray.The neurologic function of the patients were evaluated by the JapaneseOrthopaedic Association Scores(JOA),Neck Disability Index(NDI)and its classification.Results: The operation of the patients was carried out successfully.The operation time and blood loss were 472.92 + 165.49 minutes and 166.46 +37.78 ml,respectively.Postoperative CT scans showed that all 192 lateral mass screws were placed in absolutely safe or relatively safe area,of which149 screws(77.6%)were located in the absolute safety area,and 43 screws(22.34%)were located in relatively safe areas.The cortex of transverse foramen and the spinal canal were clear and no evidence of injury was found.The safety angles of C3-C6 lateral mass screws were 23.83 + 2.06 degrees,21.21 + 1.72 degrees,18.13 + 1.85 degrees and 23.13 + 2.17 degrees,respectively.The abduction angles of C3-C6 lateral mass screws were 42.54 +5.07 degrees,40.08 + 4.79 degrees,37.77 + 6.12 degrees and 41.58 + 4.55 degrees.There were no serious complications occurred,such as iatrogenic fracture,neurovascular injury,dura tear,hematoma,or infection.However,1patient had unilateral C5 nerve paralysis after operation,and at the last follow-up visit(25 months),the patient’s muscle strength of the deltoid and biceps brachii basically restored to normal.During follow-up visit,there were no obvious complications,such as delayed neurological deterioration,delayed neurovascular injury,delayed wound infection,screw and / or rod loosening,breakage or shift.The average follow-up time of 24 patients was 25.79(20-30)months.No significant loss of CCI at last follow-up visit than preoperative CCI was found(P=0.111).The JOA score was significantly higher than that preoperative(P<0.001),and the NDI score of the patients was significantly lower than that preoperative(P<0.001).The recovery rate of neurologic symptoms was 60.49% + 13.46%.Preoperative NDI ranking system included5 patients with mild dysfunction,14 cases of moderate dysfunction,4 cases of severe disability and 1 cases of complete dysfunction;Postoperative NDI ranking system included 6 cases without dysfunction,16 patients with mild dysfunction,1 cases of moderate dysfunction,1 cases of severe dysfunction,there was a statistically significant difference between preoperative andfollow-up(P<0.001).Part 3 Individualized strategy for posterior lumbar pedicle screw placementObjective: New strategies of c lumbar pedicle screw placement was proposed based on individual and intraoperative anatomic landmarks and preoperative imaging measurement.X-ray and 1 mm CT scans were used to evaluate the screw position postoperatively.Patients were followed up to evaluate the clinical outcomes by different kinds of questionnaires.Methods: From March 2011 to January 2012,74 patients with disc herniation or spinal stenosis who underwent PLIF or TLIF surgery were included in the current study and the pedicle screws were inserted using our technique.The entry point is located at the outer edge of the upper facet joint down towards the transverse process 4 mm;the vertical line of upper and lower facet joints was used to determine the direction deviating from the axis plane.X-ray and CT were used to evaluate the position of the screws and to measure the related angles.The pedicle screw related anatomic measurements were performed on CT.Angle α was the angle between the ideal trajectory and the axial plane.The angle β was the angle between the upper endplate of the vertebral body and the axial plane.And the α-β was the angle between the ideal trajectory and the upper endplate of the vertebral body.Positive number represented the ideal trajectory was cephalad deviating from the axis plane,while negative number represented the ideal trajectory was caudad deviating from the axis plane.The neurologic function of the patients were evaluated by JOA scores,NDI(The Oswestry Disability Index)scores and VAS(Visual Analogue Scale/Score)scores.Results: The operation of the patients was carried out successfully and no serious complications were found.A total of 62 patients(27 men and 35 women,with an average age of 58.95 + 8.45 years old)finished the followed-up visit for more than three years.The average operation time was169.60 + 41.21 minutes,and the average blood loss was 489.52 + 189.38 ml.A total of 274 pedicle screws were inserted in 62 patients,including 14 pediclescrews(5.11%)in L1,30 pedicle screws(10.95%)in L2,64 pedicle screws(23.36%)in L3 pedicle,100 pedicle screws(36.50%)in L4 and 66 pedicle screws(24.09%)in L5.According to Lothar Wiesner’s classification,11screws(4.01%)penetrated the cortex in I degree;2 screws(0.73%)penetrated the cortex in II degree.There were 9 pedicle screws penetrated the cortex on axial CT scans,including 6 screws(2.19%)penetrating the lateral cortex of the pedicle(5 screws in I degree and 1 screw in II degree)and 1 screws(0.36%)penetrating the medial cortex of the pedicle in I degree.There were 3screws(1.09%)penetrating the front cortex of the vertebra including 2 screws in I degree and 1 screw in II degree.There were 6 pedicle screws penetrated the cortex on Sagittal CT scans and 3 of them which penetrated the front cortex were the same screws as that on axial CT scans.Other 3 screws(1.09%)penetrated the pedicle cortex in I degree including 2 screws penetrating the upper cortex of pedicle and 1 screw penetrating the lower cortex of pedicle.There were statistically significant differences between β and α-β,︱β︱and︱α-β︱in L1-5 except for the ︱β︱and︱α-β︱in L4 which showed no significant difference.The average follow-up time of the patients was46.03(36-60)months.There were significant differences between the JOA score,the ODI score and the VAS score preoperative and postoperative,preoperative and at last follow-up visit.The recovery rate of patients was52.92% + 19.10% according to JOA score.No nerve injury was found in all patients.After operation,4 patients had hypoesthesia in the related nerve root domination area,3 of them recovered completely at the last follow-up visit,1cases did not recover completely at the last follow-up,but they were significantly relieved than preoperative.No fusion failure,screw loosening,breakage or shift was found at the last follow-up visit.Conclusions:1.C3-6 vertebral body is suitable for the placement of lateral mass screw,while C7 vertebral body has characteristics of both cervical spine and thoracic spine with transverse foramen tending to disappear and more lateral position and wider pedicle.So we suggest applying pedicle screw in C7 instead oflateral mass screw.The pedicle in lumbar vertebrae is large,which can satisfy the safety of pedicle screw placement.The lumbar connecting line between upper and lower facet joint is almost parallel to the posterior edge of the vertebral body,which can be used as an ideal reference plane for selecting the angle when inserting the pedicle screws.2.The method of lateral mass screw placement introduced in the current study is safe and easy to understand and apply.The method with high accuracy could avoid the problem caused by individual differences,anesthesia,muscle and other factors.This technique help patients get better clinical efficacy and more satisfactory recovery of nerve function.In addition,the study proposed three areas to access the trajectory of the screws: absolutely safe area,relatively safe area and dangerous area.3.Lumbar pedicle screws are widely used in many kinds of posterior surgeries with various methods of screw placement.However the risk of neurovascular injury cannot be ignored.Our method selects the entry point as outer edge of the superior articular process downwards the transverse process4 mm.The angle diverting from the axial plane is determined by connecting line between the upper and lower facet joints and the angle diverting from the sagittal plane is determined by the parallelogram law.The method with high accuracy could avoid the problem caused by individual differences,anesthesia,muscle and other factors.After assess of postoperative CT scans,no neurovascular injury,screw loosening,fracture and release were found. |
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