Finite Element Analysis Comparing the Biomechanical Parameters in Multilevel Posterior Cervical Instrumentation Model Involving Lateral Mass Screw versus Transpedicular Screw Fixation at the C7 Vertebra.

STUDY DESIGN: Basic research. PURPOSE: This finite element (FE) analysis (FEA) aimed to compare the biomechanical parameters in multilevel posterior cervical fixation with the C7 vertebra instrumented by two techniques: lateral mass screw (LMS) vs. transpedicular screw (TPS). OVERVIEW OF LITERATURE: Very few studies have compared the biomechanics of different multilevel posterior cervical fixation constructs. METHODS: Four FE models of multilevel posterior cervical fixation were created and tested by FEA in various permutations and combinations. Generic differences in fixation were determined, and the following parameters were assessed: (1) maximum moment at failure, (2) maximum angulation at failure, (3) maximum stress at failure, (4) point of failure, (5) intervertebral disc stress, and (6) influence of adding a C2 pars screw to the multilevel construct. RESULTS: The maximum moment at failure was higher in the LMS fixation group than in the TPS group. The maximum angulation in flexion allowed by LMS was higher than that by TPS. The maximum strain at failure was higher in the LMS group than in the TPS group. The maximum stress endured before failure was higher in the TPS group than in the LMS group. Intervertebral stress levels at C6-C7 and C7-T1 intervertebral discs were higher in the LMS group than in the TPS group. For both models where C2 fixation was performed, lower von Mises stress was recorded at the C2-C3 intervertebral disc level. CONCLUSIONS: Ending a multilevel posterior cervical fixation construct with TPS fixation rather than LMS fixation at the C7 vertebra provides a stiff and more constrained construct system, with higher stress endurance to compressive force. The constraint and durability of the construct can be further enhanced by adding a C2 pars screw in the fixation system.

Emergency Treatment of Cervical Vertebromedullary Trauma: 10 Years of Experience and Outcome Evaluation.

OBJECTIVE: The aim of the study is to identify and validate, through the recording of clinical and radiological data, the different surgical approaches and treatments valid for most subaxial cervical dislocation fractures and whether there is an advantage from using an anterior approach rather than a posterior approach and conversely.. MATERIAL AND METHODS: A retrospective study was carried out analyzing the case history of the last 10 years of vertebromedullary traumas treated at the spine surgery unit of the Policlinico Gemelli in Rome. Data on surgical timing, American Spinal Injury Association (ASIA) scores for neurological damage, and subsequent assessments on recovery, survival, and mortality were also examined. RESULTS: A total of 80 patients were treated: 50 by the posterior approach, 24 by the anterior approach, and six by the double approach. Our average follow-up time was 4.2 years. A prevalence of surgery with the posterior approach was noted. We observed the worsening of cervical kyphosis about 15 months after the trauma in two cases treated with the posterior approach alone. A second surgical treatment was performed in these patients. One of these patients underwent an anterior fusion; the other case underwent a posterior revision because the patient had ankylosing spondylitis. Although we found no statistically significant difference in outcomes between the various surgical treatments, in this retrospective study, we analyzed the characteristics and outcomes of cervical spine injuries that required surgical treatment. CONCLUSION: The aim of surgery in unstable cervical spine injuries should be to reduce and stabilize the damaged segment, maintain lordosis, and decompress when indicated. The optimal choice of surgical approach and treatment, or its superiority in terms of outcomes, remains a debated issue.

Hidden blood loss and its influencing factors after minimally invasive percutaneous transpedicular screw fixation in thoracolumbar fracture.

BACKGROUND: Minimally invasive percutaneous transpedicular screw fixation (MIPTSF) is generally accepted as a minimally invasive treatment for thoracolumbar fracture. However, hidden blood loss (HBL) caused by this procedure is usually disregarded. This study aimed to investigate the amount of HBL and its influencing factors after MIPTSF in thoracolumbar fracture. METHODS: Between October 2017 and December 2020, a total of 146 patients (106 males and 40 females, age range 21-59 years) were retrospectively examined, and their clinical and radiological data were recorded and analyzed. The Pearson or Spearman correlation analysis was used to investigate an association between patient's characteristics and HBL. Multivariate linear regression analysis was performed to elucidate the related clinical or radiological factors of HBL. RESULTS: A substantial amount of HBL (164.00 ± 112.02 ml, 40.65% of total blood loss (TBL)) occurred after transpedicular screw internal fixation. Multivariate linear regression analysis revealed that HBL was positively associated with TBL (p < .001), percentage of vertebral height loss (VHL) (p < .001), percentage of vertebral height restoration (VHR) (p < .001), numbers of fractured vertebrae (P = .013), and numbers of fixed vertebral segments (P = .002). CONCLUSION: A large amount of HBL was incurred in patients undergoing MIPTSF in thoracolumbar fracture. More importantly, TBL, percentage of VHL, percentage of VHR, the numbers of fractured vertebrae and fixed vertebral segments were independent risk factors for HBL.

Posterior Transpedicular Screw Fixation of Subaxial Vertebrae: Accuracy Rates and Safety of Mini-laminotomy Technique.

BACKGROUND AND AIM: Posterior cervical transpedicular screw fixation has the strongest resistance to pullout forces compared with other posterior fixation systems. Here, we present a case on the use of this technique combined with a mini-laminotomy technique, which serves as a guide for accurate insertion of posterior cervical transpedicular screws. MATERIALS AND METHODS: We retrospectively analyzed data from 40 patients who underwent this procedure in our clinic between January 2014 and March 2017. RESULTS: The study population comprised 27 males (67.5%) and 13 females (32.5%) aged 15-80 years (median, 51.5 years). Surgical indications included trauma (n = 18, 45%), degenerative disease (n = 19, 47.5%), spinal infection (n = 2, 5%), and basilar invagination due to systemic rheumatoid disease (n = 1, 2.5%). In the 18 trauma patients, 14 short-segment (1-2 levels) and 4 long-segment (≥3 levels) posterior cervical instrumentation and fusion procedures were performed. The mini-laminotomy technique was used in all patients to insert, direct, and achieve exact screw fixation in the pedicles. Pedicle perforations were classified as medial or lateral and were also graded. Among the 227 cervical pedicle fixations performed, 48 were at the C3 level, 49 at C4, 60 at C5, 50 at C6, and 20 at C7. Axial computed tomography scan measurements showed that 205 of 227 (90.3%, Grade 0 and 1) screws were accurately placed, whereas 22 (9.69%, Grade 2 and 3) were misplaced. However, no additional neurological injury due to misplacement was observed. CONCLUSION: As negligible complications were observed when performed by experienced surgeons, the mini-laminotomy technique can be safely used for posterior transpedicular screw fixation in the subaxial vertebrae for single-staged fusion.

Accuracy of 837 pedicle screw positions in degenerative lumbar spine with conventional open surgery evaluated by computed tomography.

BACKGROUND: The spatial and directional accuracy of the positioning of pedicle screws in the lumbosacral spine with conventional open surgery assessed by computed tomography (CT) has been published in several studies, systematic reviews and meta-analyses with a short-term follow-up. Inaccurate pedicle screw insertion may cause neurologic symptoms and weakens the construct. METHODS: The data of 147 patients operated on with transpedicular screw fixation based on anatomical landmarks, supported by fluoroscopy, by a senior neurosurgeon in our clinic between 2000 and 2010 were analyzed retrospectively. The accuracy of the pedicle screw position was assessed by using postoperative CT images and graded in 2-mm increments up to 6 mm by two independent surgeons and partly by an independent radiologist. RESULTS: A total of 837 lumbosacral pedicle screws were inserted in 147 randomly selected patients by a senior neurosurgeon. A mean accuracy of 85.7% of the screws being inside the pedicles was identified by the surgeon observers, with 3.3% being perforated 4 mm or more outside the pedicles. Postoperative neurologic symptoms were observed on the side corresponding to the breach in an average of 25.9% of patients with pedicle perforations, and 89.2% of the misplaced screws were either medially or inferiorly inserted. CONCLUSIONS: Screw application reached a mean accuracy of 85.7% based on anatomical landmarks supported by fluoroscopy, warranting computer-assisted navigation for increased accuracy. Our results of 24 patients (16.3%) with the breached screws indicate that the direction of the breach may be more important than the absolute deviation in causing new neurologic symptoms.

A prospective clinical study comparing MI-TLIF with unilateral versus bilateral transpedicular fixation in low grade lumbar spondylolisthesis.

BACKGROUND: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has become one of the standard techniques for approaching ipsilateral decompression, anterior column fusion, and posterior stabilization. This procedure is usually accompanied by the placement of bilateral transpedicular screws in the corresponding segment. The purpose of this study was to evaluate the clinical efficacy of unilateral screw fixation compared with bilateral fixation in patients diagnosed with low-grade symptomatic lumbar spondylolisthesis who underwent an MI-TLIF technique. METHODS: A prospective and comparative study was performed in 67 patients with grade 1 symptomatic lumbar spondylolisthesis. The sample was allocated on both unilateral fixation group (n=33) and bilateral fixation group (n=34). Clinical outcomes were evaluated using Oswestry Disability Index (ODI), visual analogue scale (VAS) for leg and back pain, and Short Form 36 Health Survey (SF-36), preoperatively, and at 1, 3, 6, and 12 months postoperatively. Changes over time and differences between the groups were analyzed. Statistical analyses included: Friedman test, Student's t-test and Mann-Whitney's U. A two-tailed P value of <0.05 was considered significant. RESULTS: During 1-year of evaluation there were no significant clinical differences between both groups. CONCLUSIONS: Patients with grade 1 symptomatic lumbar spondylolisthesis treated with MI-TLIF with unilateral screw fixation had similar clinical results than those treated with bilateral fixation at 12 months postoperatively.

Morphometric analysis of the lumbar vertebrae in the Turkish population using three-dimensional computed tomography: correlation with sex, age, and height.

BACKGROUND: Morphometric measurements of lumbar vertebrae are different in European and Asian populations. Transpedicular screws are candidates for the ideal method to treat instability of lumbar vertebrae and provide very strong stabilisation. Our study reflects the variation of morphometric measurements of lumbar vertebrae in the Turkish population according to sex, age, and height. The aim of our study was to measure the transverse pedicle diameter (TPD), vertical pedicle diameter (VPD), pedicle axis length (PAL), and transverse pedicle angle (TPA) of the lumbar vertebrae, using three-dimensional computed tomography (3D-CT), and assess variations according to sex, age, and height. MATERIALS AND METHODS: Prospective cohort, Therapeutic Level III, Urban Level III Trauma Centre. The study design adopted a morphometric analysis using 3D-CT of the lumbar vertebrae in the Turkish population, with variation in terms of sex, age, and height and comparison with previous studies. In 240 cases, measurements of TPC, VPD, PAL, and TPA with 3D-CT were performed on a total of 1200 lumbar vertebrae. The values at each lumbar level were compared in groups based on sex, age, and height. RESULTS: The results of our study determined the normal values of TPD, VPD, PAL, and TPA of lumbar vertebrae in the Turkish population using 3D-CT. Additionally there were variations in TPD, VPD, and PAL according to sex, age, and height. TPA varied according to age, while no difference was found in terms of sex or height. CONCLUSIONS: The morphometric measurements of lumbar vertebrae in the Turkish population are similar to western populations. Sex, age, and height are factors affecting reliable screw choice.

Anterior transpedicular screw fixation of cervical spine: Is it safe? Morphological feasibility, technical properties, and accuracy of manual insertion.

OBJECT Due to lack of construct stability of the current anterior cervical approaches, supplemental posterior cervical approaches are frequently employed. The use of an anterior-only approach with anterior transpedicular screws (ATPSs) has been proposed as a means of providing 3-column fixation. This study was designed to investigate the feasibility of anterior transpedicular screw (ATPS) fixation of cervical spine, to obtain the morphological measurements for technical prerequisites, and to evaluate the accuracy of the ATPS using fluoroscopy. METHODS The study included both radiological and anatomical investigations. The radiological investigations were based on data from cervical spine CT scans performed in 65 patients. Technical prerequisites of ATPS were calculated using OsiriX for Mac OS. In the anatomical part of the study, 30 pedicles (C3-7) from 6 formalin-preserved cadavers were manually instrumented. Measurements obtained included pedicle width (PW), pedicle height (PH), pedicle transverse angle (PTA), distance of the entry point from the midline (DEPM), and distance of the entry point from the superior endplate (DEPSEP). The authors also analyzed screw position in the manually instrumented vertebrae. RESULTS The mean PW and PH values showed a tendency to increase from C-3 to C-7 in both males and females. The means were significantly larger for both PW and PH in males than in females at all levels (p = 0.001). The overall mean PTA value was significantly lower at C-7 (p < 0.0001). The mean value for the distance of entry point from the midline (DEPM) represented a point at the contralateral side of the pedicle for every level except C-7. The mean DEPSEP values showed significant differences between all levels (p < 0.0001). Seven of the 30 screws were identified as breaching the pedicle (23.3%); these screw malplacements were seen at C-3 (3 screws), C-4 (2 screws), and C-5 (2 screws). CONCLUSIONS The morphological measurements of this study demonstrated that ATPS fixation is feasible in selected cases. They indicate that ATPS insertion using a fluoroscopy-assisted pedicle axis view is safe at the C-6 and C-7 levels, but the results at the other levels did not prove the safety of this technique.

Clinical and radiological outcomes of segmental spinal fusion in transforaminal lumbar interbody fusion with spinous process tricortical autograft.

STUDY DESIGN: A retrospective study. PURPOSE: To investigate clinical and radiological outcomes when using spinous process as a tricortical autograft for segmental spinal fusion in transforaminal lumbar interbody fusion (TLIF). OVERVIEW OF LITERATURE: Interbody spinal fusion is one of the important procedures in spinal surgery. Many types of autografts are harvested at the expense of complications. Clinical and radiographic results of patients who underwent TLIF with intraoperative harvested spinous process autograft in Prasat Neurological Institue, Bangkok, Thailand, were assessed as new technical innovation. METHODS: Between October 2005 to July 2009, 30 cases of patients who underwent TLIF with spinous process tricortical autograft were included. Clinical evaluations were assessed by visual analog scales (VAS) and Prolo functional and economic scores at the preoperation and postoperation and at 2 years postoperation. Static and dynamic plain radiograph of lumbar spine were reviewed for achievement of fusion. RESULTS: Initial successful fusion time in lumbar interbody fusion with spinous process tricortical autograft was 4.72 months (range, 3.8-6.1 months) postoperation and 100% fusion rate was reported at 2 years. Our initial successful fusion time in lumbar interbody fusion was compared to the other types of grafts in previous literatures. CONCLUSIONS: The use of intraoperative harvested spinous process tricortical autograft has overcome many disadvantages of harvesting autograft with better initial successful fusion time (4.72 months). VAS and Prolo scores showed some improvement in the outcomes between the preoperative and postoperative periods.

Clinical and Radiological Outcomes of Segmental Spinal Fusion in Transforaminal Lumbar Interbody Fusion with Spinous Process Tricortical Autograft

STUDY DESIGN: A retrospective study. PURPOSE: To investigate clinical and radiological outcomes when using spinous process as a tricortical autograft for segmental spinal fusion in transforaminal lumbar interbody fusion (TLIF). OVERVIEW OF LITERATURE: Interbody spinal fusion is one of the important procedures in spinal surgery. Many types of autografts are harvested at the expense of complications. Clinical and radiographic results of patients who underwent TLIF with intraoperative harvested spinous process autograft in Prasat Neurological Institue, Bangkok, Thailand, were assessed as new technical innovation. METHODS: Between October 2005 to July 2009, 30 cases of patients who underwent TLIF with spinous process tricortical autograft were included. Clinical evaluations were assessed by visual analog scales (VAS) and Prolo functional and economic scores at the preoperation and postoperation and at 2 years postoperation. Static and dynamic plain radiograph of lumbar spine were reviewed for achievement of fusion. RESULTS: Initial successful fusion time in lumbar interbody fusion with spinous process tricortical autograft was 4.72 months (range, 3.8-6.1 months) postoperation and 100% fusion rate was reported at 2 years. Our initial successful fusion time in lumbar interbody fusion was compared to the other types of grafts in previous literatures. CONCLUSIONS: The use of intraoperative harvested spinous process tricortical autograft has overcome many disadvantages of harvesting autograft with better initial successful fusion time (4.72 months). VAS and Prolo scores showed some improvement in the outcomes between the preoperative and postoperative periods.

Unilateral vertebral plate decompression, interbody fusion and pedicle screw fixation in treatment of lumbar disc berniation / 第二军医大学学报

Objective:To explore the application and efficiency of unilateral vertebral plate decompresaion,interbody fusion and pedicle screw fixation in treatment of lumbar disc herniation. Methods1From Feb. 2006 to Feb. 2008,24 patients underwent unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation. The patients were followed up for one year and the following data were recorded:operation time,estimated blood loss,duration of hospital-stay,short-term and medium-term clinical outcome. Results1 All patients had their low back pain and/or lower extremity radicular pain improved during the one year follow-up. The last follow-up showed that the numbers of patients with Oswestry Disability Index( ODI) P0-PS were 5 , 11, 6, 2,0, and 0, respectively. The clinical outcomes determined by modified JOA criteria showed that 18 patients had excellent outcomes,4 had good outcomes,and 2 had fair outcomea,with the excellent and good outcomes occupying 91. 67%. Conclusion1 The unilateral fixation can be used in patients with lumbar disc herniations who need lumbar spinal fusion. The medium-term outcomes is satisfactory.

The Effect of Vertebral Wedge Angle to the Change of Kyphotic Angle by the Posterior Instrumentation Method in Thoracolumbar Spine Fracture / 대한척추외과학회지

STUDY DESIGN: Retrospective study OBJECTIVES: To examine the effect of transpedicular screw fixation on fractured vertebrae about the vertebral wedge angle (VWA) after posterior instrumentation of the thoracolumbar fracture, determine the effect of reduced VWA on the change in the Kyphotic angle (KA), and minimize loss of reduction of KA. SUMMARY OF THE LITERATURE REVIEW: Maintenance of the KA of a thoracolumbar fracture after surgery is important for the radiologic and functional outcome. MATERIALS AND METHODS: Forty patients, who had undergone posterior instrumentation in a thoracolumbar fracture between February 2006 and February 2008 and followed-up for more than one year, were enrolled in this study. The patients were divided into two groups according to transpedicular screw fixation (Group A) or not (Group B) including fractured vertebrae. The evaluation was performed by measuring the changes in the KA and VWA taken after the injury, immediate after surgery and 1 year after surgery. RESULTS: There was correlation between groups A (transpedicular screw fixation on fractured vertebrae) and B (no transpedicular screw fixation on the fractured vertebrae) regarding the correction of the VWA and the loss of correction KA, (p<0.05). CONCLUSIONS: Reduction of the VWA is an important factor for preventing reduction loss of the KA, and transpedicular screw fixation including fractured vertebrae would help reduce the VWA. Therefore, the operator must pay attention to the increase in VWA to maintain the KA through short segment transpedicular screw fixation including fractured vertebrae.

Metal Failure in patients with Short-segmental Pedicle Screw Fixation and Fusion for Degenerative Lumbar Disease: Comparison Monoaxial with Polyaxial Screw / 대한척추외과학회지

STUDY DESIGN: Retrospective study OBJECTIVE: To evaluate the factors affecting metal failure and screw loosening of short-segmental (1- or 2-segmental) monoaxial or polyaxial screw fixation for degenerative lumbar disease. SUMMARY OF LITERATURE REVIEW: There was a report on metal failure and screw loosening in short-segmental monoaxial and polyaxial screw fixation in degenerative lumbar disease. MATERIALS AND METHODS: This study examined 227 cases who underwent short-segmental transpedicular screw fixation and vertebral fusion for a degenerative lumbar. RESULTS: Metal failure of transpedicular screws was detected in 6 cases, 3 each in groups A and B. Screw loosening occurred in 16 and 43 cases in group A and B, respectively. Both groups had a similar incidence of spinal stenosis with instability and spondylolisthesis. The failure rate and screw loosening according to the fusion level was also similar. The failure and screw loosening rates was higher in the cases who did not undergo PLIF than in the cases who underwent PLIF but the difference was not statistically significant. CONCLUSION: The metal failure and screw loosening rates after transpedicular screw fixation and spinal fusion procedures for degenerative lumbar diseases using monoaxial screws and polyaxial screws were similar.

Operative Treatment for Hangman Fracture of the Axis: Review of Fixation Methods and Indications / 대한척추외과학회지

OBJECTIVES: To evaluate the surgical indications and to compare the results of the anterior plate fixation and transpedicular fixation in cases of traumatic spondylolisthesis of the axis. MATERIALS AND METHODS: From 1987 to 2001, eighteen of 26 cases of traumatic spondylolisthesis of the axis were treated by anterior plate fixation and 8 of 26 by transpedicular screw fixation. Two of 8 cases received unilateral screw fixation and 6bilateral fixation. Two cases of the transpedicular screw fixation group were treated by additional posterior plate fixation. Oper-ativeindication was an unstable fracture, namely, with over 3.5 mm of anterior displacement, over 10 degrees of angulation, i.e., Levine types II, IIA, III, and IA. Postoperatively, Philadelphia orthosis or a soft collar was applied for 6 to 8 weeks. RESULTS: All cases achieved bone union. One case of neck pain, three cases of neck motion limitation and three cases of a kyphotic deformity exceeding 10degrees were observed in the posterior transpedicular screw fixation group. In terms of surgical complications, two cases of transient dysphagia were observed in the anterior plate fixation group and two cases of screw malposition in the transpedicular screw fixation group. The transpedicular screw fixation technique has some associated problems, such as a large operative wound scar, a large bleeding volume, and technical difficulty. CONCLUSION: Both the anterior plate fixation and transpedicular screw fixation methods are useful treatment methods for Levine type II, IIA and III hangman fracture for early bone union and early rehabilitation. The anterior plate fixation technique is easi-er and has fewer complications than posterior transpedicular screw fixation, therefore, the ranspedicular screw fixation method should be confined to the management of type IA fracture with rotational displacement.

Evoked EMG Monitoring During Transpedicular Fixation of Lumbosacral Spine

OBJECTIVE: The purpose of this study is to evaluate the searching stimulus intensity at each pedicle and to identify the most vulnerable roots in transpedicular screw fixation of lumbosacral spine. METHOD: Thirty-two patients with unstable lumbosacral vertebra were treated with intrapedicular screw fixation. Small holes were made by an air drill on the pedicle from L2 to S1 for screw fixation. Constant current stimulation pulses(0.2 msec duration) were delivered through a ball-tipped nasopharyngeal probe used to palpate the walls of each pedicle, and observation was made of electromyogram(EMG) evoked lower extremity muscles. The probes were placed in each pedicular wall manually, and evaluated for searching stimulus intensity, the current necessary to evoked EMG. RESULTS: The cases that the searching stimulus intensity was above 5 mA were 99 cases(97%), above 10 mA were 61 cases(59.8%) and below 5 mA were 3 cases(2.9%). The vastus medialis muscle is most sensitive in L2(100%) and L3(78.9%), tibialis anterior is in L4(81.8%), Peroneus longus is in L5(50.5%) and gastrocnemius is in S1(87.5%). CONCLUSION: We can regard the searching stimulus intensity as 5 mA and the root located at Infero-medial side of pedicle is most vulnerable in transpedicular screw fixation. Furthermore, stimulus-evoked EMG monitoring during transpedicular spine instrumentation is helpful to avoid neural tissue injury.

Computer-assisted Orthopaedic surgery (AOS): from pedicle screw insertion to further applications.

Computer assisted orthopaedic surgery is a new but rapidly evolving field. Based on previous research and development in the area of stereotactic neuronavigation a few groups have adapted these technologies for the image interactive insertion of pedicle screws. The present paper summarizes past and current work in the field of computer assisted orthopaedic surgery and describes the state of the art of research and future innovations, particularly in in vivo applications.

Results of Transpedicular Screw Fixation in Spondylolisthesis of the Lumbar Spine

The auther studied 54 lumbar spondylolisthesis patients diagnosed and treated with transpedicular screw fixation and bony fusion at our Hosptial between January 1990 and December 1994, and analysed the outcome. The results may be summarized as follows: 1) Of the 54 cases, 17 were degenerative spondylolisthesis and 37 were spondylolytic spondylolisthesis. Occurrence peaked during the fifth and sixth decades. 2) Posterolateral fusion(P.L.F) was performed in 37 cases and posterior lumbar interbody fusion(P.L.I.F) in eight ; P.L.F and P.L.I.F in combination was performed in nine cases. The mean follow-up period was 25 months. 3) In no patients was significant neurologic injury or functional root loss seen. Complications included two instrument failures and one wound infection. 4) Radiologic and clinical outcome was better in degenerative than in spondylolitic spondylolisthesis. 5) The radiologic and clinical outcome of bony fusion types P.L.F and P.L.I.F was the same. 6) The surgical result as evaluated by Mc.Nab's criteria was satisfactory in 81% of patients.

Surgical Experience of transpediculr Screw Fixation of the Spine

Vertebral transpedicular screws provide secure attachment for posterior spinal fixation device, the authors had experienced 29 cases of transpedicular screw fixation to obtain fixations of the thorcolumbar and lumbar spine instability, the patients were operated between February, 1992, and May, 1995. Spinal Fusion was attempted at one to four levels of thoracic and lumbar spine. Follow-up period was from 6 to 33 months, averaging 16 months. The result was summerized as follows: 1) Of the 29 cases, 20 were spondylolisthesis and 9 were fracture and dislocation. 10 patients(34.5%) were 30 years old, and 20 cases(69%) were female. Mean age was 42 years. 2) The symptom included low back pain, sciatica and intemittant claudificaton in the order of incidence. 3) The sites of spondylolisthesis were L4-5 in 12 cases(60%) and L5-S1 in 8 cases(40%). The average degree of slippage in spondylolisthesis was Meyerding's grade I(85%). The sites of fracture were T12 in 5 cases(55.6%), L1 in 2 cases(22.2%), L2 with L3 in 1case(11.1%) and L1 in 1 case(11.1%). 4) There was no patient with significant neurologic injury or functional root loss. A screw malposition was observed in one case. 5) The results of operations were considered exellent in 16 cases(55%), good in 10 cases(35%) and fair in 3 cases(10%), and satisfactory bony fusion was obtained.

Evaluation of Clinical Result of Transpedicular Screw Fixation and Modified Posterior Fusion for Lumbar Spondylolisthesis

During the past five years(1990. 7-1995. 6,) eighteen patients with symptomatic lumbar spondylolisthesis whose neurogenic intermittent claudication appeared within fifteen minutes of walking, but otherwise suffered from no significant disc herniation at the involved level, underwent operation. The lumbar spine was stabilized by transpedicular screw fixation and modified posterior fusion instead of posterior lumbar interbody fusion(PLIF). There were three males and fifteen females and the average age was fourty-seven years(range, thirty-six to sixty-four years). After an average follow-up period of thirty-one months(range, fifteen to fifty-two months), the result were excellent in eight, good in seven, moderate in two, and poor in one patients. The satisfactory result of 83.3 percent of the patients suggested that the modified posterior fusion, instead of posterior lumbar interbody fusion, in which the spinous process, the lamina, the facet joint, and only the base of the transverse process were included, after transpedicular screw fixation in lumbar spondylolis thetic patients would be enough when there is no significant disc herniation at the involved level.

Posterior Lumbar Interbody Fusion with Pedicle Screw Fixation for Lumbar Spondylolisthesis

The theoretical advantages of spondlylolisthesis reduction-fixation are substantial, but some questions such as excessive risk and morbidity relative to in situ fusion remain unresolved yet. This study included 10 consecutive patients(2 male, 8 female) who underwent posterior lumbar interbody fusion(PLIF) with transpedicular instrumentation(AKITA pedicular screw system) over the past six menths from July to December 1993. All patients were isthmic type, adult(between 30 and 57) and between grades I and II. Claudication was the most common symptom. All patients were operated upon by one surgeon(C.K.P.) and follow-up was conducted through patient interviews and examinations, both clinically and rediologically. The patients were followed postoperatively from 6 to 12 months. There were no neurologic complication related to the procedures. The clinical outcomes assessed more than 6 months postoperatively were as follows:improvement, 9/10;stationary 1/10. Radiologically, the mean reduction rate of slippage(preoperative percentage slip-postoperrative one/preoperative one x100) was 4.3% and all patients developed solid fusion. In conclusion, patients who underwent PLIF supplemented with transpedicular fixation had good overall clinical and radiological outcomes without significant neurological complications related to PLIF or screw placement.