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Study Design: A retrospective cohort., Background: Degenerative spondylolisthesis (DS) with lumbar stenosis is a well-studied pathology and diagnosis is most commonly determined by a combination of magnetic resonance imaging (MRI) and standing radiographs. However, routine upright imaging is not universally accepted as standard in all practices. To the best of our knowledge, there has been no study investigating the incidence of missed diagnosis of DS evident only on standing lateral or dynamic radiographs when compared with sagittal alignment on MRI., Objective: The authors hypothesize that supine MRI evaluation alone in lumbar degenerative disease will significantly underestimate the incidence of DS. Secondary hypothesis is that there will be no significant difference in detecting spondylolisthesis when comparing dynamic flexion-extension radiographs to standing lateral radiographs., Methods: We retrospectively evaluated all patients presenting to spine clinic for degenerative lumbar conditions from July 2004 to July 2006 who had an MRI, upright lateral, and flexion-extension radiographs at our institution. The incidence of DS found on dynamic flexion-extension radiographs but not on MRI was determined. We then reviewed each and compared flexion-extension versus standing lateral views to determine whether there was any significant difference in detecting anterolisthesis., Results: Of 416 patients with eligible studies, 109 were found to have DS at levels L4-L5, L5-S1, or L3-L4 based on flexion-extension radiographs. Of these, only 78 were found to have a corresponding spondylolisthesis on MRI, leaving 31/109 (28%) of DS levels undiagnosed on MRI. No additional anterolisthesis cases were detected on standing flexion-extension verses standing lateral radiographs., Conclusions: Routine standing lateral radiographs should be standard practice to identify DS, as nearly 1/3 of cases will be missed on supine MRI. This may have implications on whether or not an arthrodesis is performed on those patients requiring lumbar decompression. Flexion-extension radiographs demonstrated no added value compared with standing lateral x-rays for the purposes of diagnosing DS.

Study Design: This was a prospective, nonrandomized study., Objectives: To assess the accuracy of O-arm navigation-based pedicle screw insertion in lumbar degenerative spondylolisthesis and to compare it with free-hand pedicle screw insertion technique in matched population., Summary of Background Data: O-arm navigation is latest in navigation technology that can provide real-time intraoperative images in 3 dimensions while placing the pedicle screws to improve intraoperative pedicle screw accuracy. Degenerative lumbar spondylolisthesis is a locally unstable pathology and placement of pedicle screws can cause increased rotation and translation of the vertebral body. However, is this motion detected by the tracker placed across the unstable segment, is a matter of debate. Inability to detect these positional changes can lead to pedicle perforation while inserting screws using navigation. No study has evaluated the role of O-arm navigation in this patient population., Materials and Methods: The study population was divided into 2 groups with 19 patients each, one comprising patients who underwent O-arm navigation-based pedicle screw insertion (group 1) and the other comprising patients who underwent free-hand pedicle screw insertion technique (group 2). A total of 152 pedicle screws were implanted in 38 patients for 1-level instrumented fusion for degenerative lumbar spondylolisthesis. Intraoperative 3-dimensional computed tomography scans using the O-arm were obtained for all patients after insertion of pedicle screws. The images were reviewed intraoperatively and postoperatively for the analysis of pedicle breaches. Assessments in either of the group included (i) accuracy of placement of screws; (ii) the rate and direction of perforation; and (iii) the number of segments the perforated screw was away from the navigation tracker., Results: Mean age of patients in group 1 (O-arm navigation-assisted) was 60 years (SD 11.25; range, 37-73 y), whereas in group 2 (free-hand pedicle screw) was 62 years (SD 18.07; range, 36-90 y). Overall anatomic perforation rate was 12.5% (19/152). Individually, group 1 had 14.47% (11/76) of perforations in comparison with 10.53% (8/76) observed in group 2. The difference was not statistically significant. The lateral margin was the most common site of perforation in both group 1 (64%, 7/11) and group 2 (62.5%, 5/8). Functional perforation rate for the series was 3.3% (5/152), with group 1 having 2.63% (2/76) and group 2 having 3.95% (3/76). The rate of perforation (PR) was significantly higher statistically when the tracker was placed 3 or more [PR 37.5% (6/16)] spinal segments away from instrumented segment compared with when it was placed 1 (0%) or 2 [PR 13.89% (5/36)] spinal segments away. Overall, 11 screws (11/152, 7.24%) had grade 2 perforations and had to be revised. No neurological complications were observed in the series., Conclusions: O-arm navigation does not provide any significant advantage over conventional free-hand pedicle screw insertion technique in patients with single-level degenerative spondylolisthesis. The accuracy is dependent on the distance of the tracker from the level of instrumentation. Lateral perforations are more common because of instability at the instrumented level leading to translation and rotation of the vertebral body while placing pedicle screws leading to preferential lateral trajectory. These lateral perforations could not be prevented by using navigation. However, no significant complications were noted in either technique.

Study Design: A prospective study of 2 different fusion techniques for the treatment of single-level degenerative spondylolisthesis., Objective: To determine whether the addition of an intervertebral cage improves the clinical outcome and fusion rate of patients undergoing posterior lumbar interbody fusion (PLIF) after decompression for degenerative spondylolisthesis., Summary of Background Data: The surgical approach that should be used for degenerative spondylolisthesis is a controversial issue. Decompression and PLIF with an interbody cage is widely used. Theoretical advantages in favor of PLIF include anterior column support, indirect foraminal decompression, restoration of lordosis, and reduction of the slip via ligamentotaxis. Despite numerous publications, the scientific support for the PLIF method is, however, weak., Materials and Methods: A prospective study was carried out including 59 patients with degenerative spondylolisthesis. Average age of patients was 66 years: 34 males and 25 females. Patients were divided into 2 treatment groups: group 1-32 patients with PLIF with interbody graft and group 2-27 patients with PLIF with cage. Minimum 2-year follow-up. Outcomes were assessed by measuring preoperative and postoperative lordotic angles. SF-12 physical and mental health scores were recorded along with visual analogue scores for pain. Complications were also recorded., Results: No significant difference in the postoperative lordotic angles was achieved between the 2 techniques. Nonsignificant difference in the clinical outcomes between both the techniques., Conclusions: We have found the use of a cage to achieve lumbar interbody fusion in the treatment of degenerative lumbar spondylolisthesis does not confer any significant advantages in terms of restoration of lumbar lordosis, improvement in clinical symptoms, or relief of pain postoperatively.

Study Design: Cross-sectional evaluation of sacro-pelvic morphology and orientation as well as spondylolisthesis prevalence in a cohort of young gymnasts., Objective: To evaluate the prevalence of spondylolisthesis in a cohort of gymnasts, as well as the associated demographic characteristics and sacro-pelvic morphology and orientation., Summary of Background Data: Numerous studies have shown that sagittal sacro-pelvic morphology and orientation is abnormal in spondylolisthesis. Sacro-pelvic morphology and orientation in gymnasts and their relationship with spondylolisthesis have never been analyzed., Methods: Radiologic evaluation of 92 gymnasts was performed to identify spondylolisthesis, and to measure pelvic incidence, pelvic tilt, sacral slope, and sacral table angle. In the presence of spondylolisthesis, the slip percentage was measured. Different demographic and training characteristics were evaluated. Radiographic parameters were compared with reference values published for asymptomatic children and adolescents, and for subjects with spondylolisthesis., Results: A 6.5% prevalence of spondylolisthesis was found in our cohort. The weekly training schedule was the only statistically significant different demographic characteristic between the 2 groups, at 20.6±5.4 versus 14.4±5.6 h/wk for subjects with and without spondylolisthesis, respectively. Pelvic incidence, pelvic tilt, sacral slope, and sacral table angle were 69±20, 15±13, 54±11, and 88±7 degrees in gymnasts with spondylolisthesis, and 53±11, 10±6, 43±9, and 94±6 degrees in gymnasts without spondylolisthesis, respectively. When compared with asymptomatic individuals, pelvic incidence and pelvic tilt were slightly superior in gymnasts without spondylolisthesis. Pelvic incidence, sacral slope, and sacral table angle were significantly different between gymnasts with and without spondylolisthesis., Conclusions: The prevalence of spondylolisthesis in young gymnasts was similar to that observed in the general population. Sagittal sacro-pelvic morphology and orientation was abnormal in gymnasts with spondylolisthesis. Sagittal sacro-pelvic morphology and orientation was also slightly different in gymnasts without spondylolisthesis when compared with the normal population. The present study supports an association between spondylolisthesis and abnormal sacro-pelvic orientation and morphology.

Study Design: A cross-sectional imaging study., Objective: To investigate the relationship between cervical and lumbar spine lesions in patients with rheumatoid arthritis (RA), and to analyze associated factors in those with concurrent cervical and lumbar endplate erosion (EE)., Summary of Background Data: Both the lumbar and cervical spines are often involved in RA, but little is known about the relationship between cervical and lumbar lesions. EE is often found in the spine of RA patients, but its prevalence and associated factors have not been well studied., Methods: We enrolled 201 RA patients in this study. Cervical lesions (horizontal and vertical atlantoaxial dislocation, subaxial subluxation) and lumbar lesions (vertebral fracture, scoliosis, spondylolisthesis) were evaluated on plain radiographs. EE was evaluated on sagittal T1-weighted magnetic resonance images, and graded into 4 categories. The prevalence of each lesion was calculated, and correlations between general cervical and lumbar lesions and between cervical and lumbar EE were analyzed. To assess the clinical condition of RA, we evaluated disease duration, Steinbrocker stage, modified Stanford Health Assessment Questionnaire results, and Disease Activity Score for 28 joints with the erythrocyte sedimentation rate. Factors associated with concurrent lumbar and cervical EE were analyzed using multiple logistic regression analysis., Results: Cervical lesions were found in 42.3% of patients and lumbar lesions in 56.2%. There was no significant correlation between the presence of cervical and the presence of lumbar lesions, but patients with cervical subaxial subluxation were significantly more likely to have lumbar spondylolisthesis. Cervical EE (≥1 points) was found in 61.2% of patients and lumbar EE in 39.3%. Total cervical EE score was significantly correlated with lumbar EE score. Moderate/high disease activity, Steinbrocker stage IV, and severe cervical or lumbar disk degeneration were associated with concurrent cervical and lumbar EE., Conclusions: Some cervical lesions are significantly associated with lumbar spinal lesions. Concurrent cervical and lumbar EE are related to RA disease activity and peripheral joint deterioration, suggesting that RA activity may play an important role in total spinal involvement.

Study Design: Retrospective radiographic analysis., Objective: To determine which lumbar interbody technique is most effective for restoring lordosis, increasing disk height, and reducing spondylolisthesis., Summary of Background Data: Lumbar interbody fusions are performed in hopes of increasing fusion potential, correcting deformity, and indirectly decompressing nerve roots. No published study has directly compared anterior, lateral, and transforaminal lumber interbody fusions in terms of ability to restore lordosis, increase disk height, and reduce spondylolisthesis., Materials and Methods: Lumbar interbody fusion techniques were retrospectively compared in terms of improvement of lordosis, disk height, and spondylolisthesis between preoperative and follow-up lateral radiographs., Results: A total of 220 consecutive patients with 309 operative levels were compared by surgery type: anterior (184 levels), lateral (86 levels), and transforaminal (39 levels). Average follow-up was 19.2 months (range, 1-56 mo), with no statistical difference between the groups. Intragroup analysis showed that the anterior (4.5 degrees) and lateral (2.2 degrees) groups significantly improved lordosis from preoperative to follow-up, whereas the transforaminal (0.8 degrees) group did not. Intergroup analysis showed that the anterior group significantly improved lordosis more than both the lateral and transforaminal groups. The anterior (2.2 mm) and lateral (2.0 mm) groups both significantly improved disk height more than the transforaminal (0.5 mm) group. All 3 groups significantly reduced spondylolisthesis, with no difference between the groups., Conclusions: After lumbar interbody fusion, improvement of lordosis was significant for both the anterior and lateral groups, but not the transforaminal group. Intergroup analysis showed the anterior group had significantly improved lordosis compared to both the other groups. The anterior and lateral groups had significantly increased disk height compared to the transforaminal group. All the 3 groups significantly reduced spondylolisthesis, with no difference between the groups.

Study Design: This is a retrospective study., Objective: To investigate the risk factors for radiographic L5-S1 disk height reduction after lumbar posterolateral floating fusion surgery., Summary of Background Data: We investigated data from 86 patients (45 men) who underwent posterolateral floating fusion surgery from 2007 to 2010. The follow-up was from 2 to 6 years. The mean age of the patients was 65.4 years., Methods: L5-S1 disk height was calculated and >2 mm reduction was defined as significant. Age, sex, height, weight, body mass index, number of fused levels, grade of disk degeneration, disk height and diameter, sacrolumbar alignment, alignment of fused level, achievement of union, and proximal adjacent segment disorder at final follow-up were compared. Univariate and multivariate logistic regressions were performed., Results: L5-S1 disk height reduction occurred in 14 patients (30.2%). The number of fused levels was significantly greater (1.8±0.8 vs. 1.4±0.6) in patients without disk height reduction. Radiology showed a significant change of L1-S1 sacrolumbar alignment after surgery in patients without disk height reduction (0.3±6.6 vs. -4.5±7.6 degrees). The height of the disk posterior to the L5-S1 intervertebral disk before surgery was significantly greater (7.3±2.1 vs. 6.1±2.1 mm) in patients without disk height reduction. In multivariate logistic regression analysis, fusion of >3 levels was a significant risk factor for L5-S1 disk height reduction., Conclusions: In posterolateral floating fusion surgery, there was a higher risk of L5-S1 disk height reduction and consequent foraminal stenosis in patients with multiple-level fusion. Surgical methods and fusion levels should be chosen after considering their association with L5-S1 disk height reduction.

Study Design: This study was retrospectively conducted on 51 patients with L5-S1 spondylolisthesis., Objective: This study was conducted to compare a total of 11 pelvic parameters, such as the level of displacement by Meyerding method, lumbar lordosis, sacral inclination, lumbosacral angle, slip angle, S2 inclination, pelvic incidence (PI), L5 inclination, L5 slope, pelvic tilt (PT), and sacral slope (SS) between low-grade and high-grade spondylolisthesis, and to investigate a correlation of the level of displacement by Meyerding method with other pelvic parameters., Methods: Pelvic parameters were measured using preoperational erect lateral spinal simple radiographs. The patients were divided into 39 patients with low-grade spondylolisthesis and 12 patients with high-grade spondylolisthesis before analysis. In all patients of both groups, 11 radiographic measurements including the level of displacement by Meyerding method, lumbar lordosis, sacral inclination, lumbosacral angle, slip angle, S2 inclination, PI, L5 inclination, L5 slope, PT, and SS were performed. T test and Pearson correlation analysis were conducted to compare and analyze each measurement., Results: As for the comparison between the 2 groups, a statistically great significance in the level of displacement by Meyerding method, lumbosacral angle, slip angle, L5 incidence, PI, and L5 slope (P≤0.001) was shown. Meanwhile, a statistical significance in the sacral inclination and PT (P<0.05) was also shown. However, no statistical significance in the S2 incidence and SS was shown. A correlation of the level of displacement by Meyerding method with each parameter was analyzed in the both the groups. A high correlation was observed in the lumbar lordosis, lumbosacral angle, slip angle, L5 incidence, and L5 slope (Pearson correlation coefficient, P=0.01), as well as the sacral inclination, PI, and PT (Pearson correlation coefficient, P=0.05). Meanwhile, no correlation was shown in the S2 incidence and SS., Conclusions: A significant difference in the lumbosacral angle, slip angle, L5 incidence, PI, L5 slope, sacral inclination, and PT was shown between the patients with high-grade spondylolisthesis and patients with low-grade spondylolisthesis. Among the aforementioned measurements, the PI showed a significant difference between the 2 groups and also had a significant correlation with the dislocation level in all the patients.

Study Design: Case report of 3 patients with high-grade isthmic spondylolisthesis treated using a novel minimally invasive technique using a posterior transsacral rod., Objective: To assess the efficacy, safety, and advantages of this approach in the treatment of high-grade L5-S1 spondylolisthesis., Summary of Background Data: Surgical treatment of high-grade isthmic spondylolisthesis at the L5-S1 level is technically demanding. The most commonly used procedure is posterior spinal fusion. In this report, we present a new minimally invasive technique for the treatment high-grade isthmic spondylolisthesis in 3 patients with sagittally balanced spines., Materials and Methods: Three patients with high-grade L5-S1 spondylolisthesis underwent L4-S1 fusion with percutaneous pedicle screw fixation supplemented with a transsacral rod implanted through a tubular retractor. We report technical details, clinical, and radiologic results at follow-up., Results: All 3 patients suffered from grade 3 or 4 L5-S1 spondylolisthesis. All patients had neutral sagittal balance on preoperative imaging. There were no postoperative complications and all 3 patients were discharged within 48 hours. At final follow-up (range, 13-18 mo), all patients were pain free off all narcotic pain medication and fusion was observed in all 3 patients., Conclusions: We have shown the technical feasibility of anterior and posterior fusion for severe L5-S1 spondylolisthesis using a minimally invasive percutaneous technique through a transsacral approach. The main advantage of a posterior transsacral axial rod fixation is that it creates a structurally sound anterior column support, thus eliminating the problems related to bone grafts and eliminating the complications associated with an anterior approach. Our preliminary results suggest that this technique is feasible and seems to be associated with favorable outcome, although larger studies are warranted to verify these findings.

Study Design: Prospective study of the sagittal spino-pelvic parameters and deformity parameters in low-grade isthmic spondylolisthesis preoperation and postoperation., Objective: To better understand how the surgery influences sagittal spino-pelvic alignment in low-grade spondylolisthesis., Summary of Background Data: Over the past decade, the importance of the sagittal spino-pelvic parameters was recognized. However, the postoperative change of sagittal balance parameters in low-grade spondylolisthesis was still unclear., Methods: Forty-nine patients (mean age, 53.2±7.2 y) with low-grade L5-S1 isthmic spondylolisthesis and 60 normal volunteers (mean age, 44.5±8.4 y) were included in the study. Each subject had a radiograph that allowed measurement of sagittal spino-pelvic parameters before and after surgery. The follow-up duration was at least 2 years. Sagittal spino-pelvic parameters and deformity parameters were measured for comparison., Results: Pelvic incidence, pelvic tilt (PT), sacral slope, lumbar lordosis (LL), lumbar 5 incidence, and lumbosacral angle of normal volunteers were smaller than those of spondylolisthesis patients. All of the parameters changed significantly after the posterior lumbar interbody fusion. Postoperative PT reduced by 4.9 degrees, which had no significant difference compared with the control group (P=0.601). The changes of slip degree and height of the intervertebral disk revealed correlation with the increase of LL (r=-0.483, P=0.003; r=0.365, P=0.010)., Conclusion: The improvement of PT may play an important role in the reconstruction of the sagittal alignment and therapeutic outcome. The restoration of the slip degree and height of the intervertebral disk would increase the LL with a wedged cage. To get a better LL, the size and geometry of the cage was recommended to be evaluated before surgical treatment.

Study Design: A retrospective study of medium-term results., Objective: To describe a technique for posterior decompression using microsurgical lumbar flavectomy (MLF) without facetectomy, which is based on the anatomic features of the ligamentum flavum, and to examine the clinical outcomes of patients with lumbar spinal spondylolisthesis with lower extremity symptoms rather than low back pain, who underwent this procedure by 2 different approaches., Summary of Background Data: Posterior decompression with fusion has been the optimal and standard operative treatment for lumbar degenerative spondylolisthesis. Alternatively, minimally invasive procedures have been used for the treatment of lumbar degenerative spondylolisthesis with favorable outcomes., Methods: A bilateral laminotomy (BL group) was performed on 44 consecutive patients, and bilateral decompression by a unilateral approach (BDU group) was performed on 23 consecutive patients. The mean follow-up period was 7.0 years. The Japanese Orthopaedic Association score and recovery rate were obtained, and radiographic assessment was performed using plain radiograms on the lateral view while standing in flexion, neutral, and extension postures before surgery and at the final follow-up., Results: The Japanese Orthopaedic Association score at the final follow-up was improved in the BL and BDU groups, compared with that before MLF. The mean recovery rate was 72.4% and 68.4%, respectively. The mean % slip increased at the final follow-up, compared with that before surgery in both groups, except for the % slip in the extension posture in the BDU group. However, there was no significant difference in the dynamic % slip in the flexion-extension posture between before surgery and at the final follow-up., Conclusions: Clinical and radiologic parameters were not significantly different between the 2 groups. This technique of MLF using either approach did not increase the dynamic % slip and showed favorable medium-term clinical results in cases of lumbar degenerative spondylolisthesis.

Study Design: Retrospective cohort study., Objective: The objective of the study was to analyze segmental balance in patients with isthmic spondylolisthesis undergoing single-level transforaminal lumbar interbody fusion (TLIF)., Summary of Background Data: Sagittal malalignment of the fused segment was suggested to be associated with degeneration of the adjacent segment. Meticulous surgical technique and particular attention to hardware positioning with the aim to restore segmental balance at the fusion level have been recommended to achieve better long-term clinical outcomes, but no single study addressed all proposed factors., Methods: Standard lateral radiographs of the lumbosacral spine in the neutral standing position were retrospectively obtained for 32 patients undergoing single-level TLIF. Preoperative versus postoperative versus final follow-up (12 to 60 mo) values of translational slip (TS), posterior disc space height (PDSH), and segmental lordosis (SL) were compared using paired samples t test. Change in SL postoperatively between groups of next grouping variables: type and position of the interbody device, and rod contouring, was compared using 2-tailed independent samples t test. Association between position of the interbody device and immediate PDSH was addressed with regression analysis postoperatively and at final follow-up., Results: Mean TS decreased (P<0.001) and mean PDSH increased (P=0.002), but no significant change in SL occurred postoperatively (P=0.811). Increase in SL was observed with ventral positioning of the interbody device (P=0.009) and with bending of connecting rods (P=0.023). During follow-up, there was increase in TS (P=0.002) and decrease in PDSH (P<0.001) and SL (P<0.001) compared with postoperative values. Lower PDSH was found to be associated with more ventral positioning of the interbody device, both postoperatively (P=0.035) and at final follow-up (P=0.029)., Conclusions: This study demonstrates that reduction of TS and restoration of disc space height are readily achieved with single-level TLIF. However, to establish an increase in SL consistent rod contouring and meticulous anterior placement of the interbody device should be applied. Excessive ventral positioning of the cages might result in insufficient disc space height restoration.

Study Design: Cadaveric Study., Objective: To compare a fluoroscopic imaging system with computed tomography (CT) and radiographs in detection of spondylolysis and radiation exposure in a cadaver model., Summary of Background Data: Lumbar spondylolysis is defined as a defect or fracture of the pars interarticularis and occurs with or without anterior spondylolisthesis. CT scan is the gold standard imaging study for spondylolysis but is limited by the supine position, which may cause reduction of anterolisthesis and by ionizing radiation, which limits the frequency of follow-up scans., Methods: Thirteen intact cadaveric lumbar spine segments with 26 pars were randomized to be left intact or to undergo simulated fracture using a 1.3 mm oscillating microsurgical saw. Fifteen pars underwent simulated fracture and 11 pars were left intact. Lumbar spine segments were imaged using plain radiographs, multiplanar fluoroscopic imaging, and conventional CT scan. The images were interpreted by 3 observers blinded to the number and location of defects. Radiation exposure and doses were recorded from all imaging units., Results: Average radiation doses were 0.0025 mSv for each radiograph, 0.23 mSv (low dose) and 0.47 mSv (high dose) for fluoroscopic imaging, and 1.5 mSv for conventional CT imaging (pediatric dose setting). Evaluation of radiographs for spondylolysis had sensitivity of 98% and specificity of 97%. Evaluation using low-dose fluoroscopic images, high-dose fluoroscopic images, and CT scan images correctly identified the status of all pars based on multiplanar images; sensitivity and specificity were 100%. Kappa analysis demonstrated a value of 0.89 for radiographic interpretation indicating excellent agreement. Kappa values describing agreement for image interpretation for fluoroscopic imaging and CT scan were equal to 1.0, representing perfect agreement., Conclusions: Three-dimensional fluoroscopic imaging provides comparable diagnostic imaging with CT scan in an experimental cadaveric model of spondylolysis using up to 85% less radiation than conventional CT scan.

Study Design: Prospective., Objective: To explore the feasibility and accuracy of thoracic and lumbar pedicle guidewire placement using a newly developed Spine Bull's-Eye Robot with the pedicle standard axis view (PSAV)., Summary of Background Data: Placement of pedicle screws in the thoracic spine is considered to be particularly risky surgery and is associated with a relatively high rate of screw misplacement. Use of robot-assisted surgery may improve the accuracy of pedicle screw placement., Methods: The study included 204 pedicles (T1-L5) from 6 human vertebrae and 5 pedicles from 3 patients. Computed tomographic reconstruction of target vertebrae was performed for surgical planning. Using the PSAV, a guidewire (1.2 mm diameter, 13.5 cm length) was inserted into the "bull's-eye" (the center of the pedicle circular projection) using the remotely operated Spine Bull's-Eye Robot. After surgery, vertebral body axial and lateral radiographs, and computed tomographic scans were used to assess the guidewire trajectory. Planned and actual (postoperative) measures for transverse section angle, sagittal section angle, and the superior/inferior and medial/lateral vertical distances from the entry point were compared., Results: The PSAV was acquired clearly in 203 of 209 (97.1%) pedicles; the guidewire was successfully inserted in each of these pedicles. There were no significant differences between any of the planned and actual (postoperative) measures. All of the pedicles for which guidewire placement was abandoned (because of lack of bull's-eye resolution in the PSAV) were small upper thoracic specimens, exhibiting evidence of decalcification, presumably because of preservation procedures. None of the patients experienced complications associated with guidewire placement., Conclusions: Use of the Spine Bull's-Eye Robot with PSAV seems be an accurate and feasible approach for guidewire (and thus pedicle screw) placement in the thoracic and lumbar spine.

Study Design: A case-control study., Objective: To analyze the facet joint orientation in the sagittal plane [pedicle-facet angle (P-F angle)] and facet tropism, and clarify the relationship between P-F angle and the amount of vertebral slipping in degenerative spondylolisthesis (DS) patients on multislice computed tomography using multiplanar reformations techniques., Summary of Background Data: Some studies have indicated a correlation between DS and an increased sagittal orientation of the facet joints. However, the facet orientation has not been fully elucidated and it had been measured only in the transverse plane of computed tomography and magnetic resonance imaging. Although the P-F angle had been measured on the plain radiographs, accurate measurement was difficult to obtain because of the technical limitations., Methods: A total of 156 patients, who came to our hospital for low back pain and/or sciatica were divided into 2 groups. The DS group comprised of 78 patients with DS at L4-L5, and the control group comprised of 78 patients without spondylolisthesis. The P-F angle and tropism were measured in the sagittal plane on multi-slice computed tomography using multiplanar reformations techniques., Results: The P-F angles at L4-L5 were 117.02±6.89 degrees (left), 115.95±6.02 degrees (right) in the DS group and 106.71±3.19 degrees (left), 105.58±3.07 degrees (right) in the control group, respectively (P₁<0.01, P(r)<0.01). The facet tropism at L4-L5 in the DS group was significantly increased, compared with that in the control group (P=0.004). The mean P-F angle at L4-L5 did not correlate with the amount of vertebral slipping (r=0.176, P=0.122)., Conclusions: The P-F angle was the highest at L4-L5 both in the DS and the control group, which might explain the fact that L4 vertebra is more likely to slip forward. The P-F angle of the slipped vertebra alone was more horizontally inclined and facet tropism in the sagittal plane may relate well to DS.

Study Design: Case series., Objective: To describe a minimally invasive surgical technique for treatment of lumbosacral spondylolisthesis., Summary of Background Data: Traditional surgical management of lumbosacral spondylolisthesis is technically challenging and associated with significant complications. Minimally invasive surgical techniques offer patients treatment alternatives with lower operative morbidity risk. The combination of percutaneous pedicle screw reduction and an axial presacral approach for lumbosacral discectomy and fusion is an option for the surgical management of low-grade lumbosacral spondylolisthesis., Methods: Twenty-six consecutive patients with symptomatic L5-S1 level isthmic spondylolisthesis (grade 1 or grade 2) underwent axial presacral lumbar interbody fusion and percutaneous posterior fixation. Study outcomes included visual analogue scale for axial pain severity, Odom criteria, and radiographic fusion., Results: The procedure was successfully completed in all patients with no intraoperative complications reported. Intraoperative blood loss was minimal (range, 20-150 mL). Median hospital stay was 1 day (range, <1-2 d). Spondylolisthesis grade was improved after axial lumbar interbody fusion (P<0.001) with 50% (13 of 26) of patients showing a reduction of at least 1 grade. Axial pain severity improved from 8.1±1.4 at baseline to 2.8±2.3 after axial lumbar interbody fusion, representing a 66% reduction from baseline (95% confidence interval, 54.3%-77.9%). At 2-year posttreatment, all patients showed solid fusion. Using Odom criteria, 81% of patients were judged as excellent or good (16 excellent, 5 good, 3 fair, and 2 poor). There were no perioperative procedure-related complications including infection or bowel perforation. During postoperative follow-up, 4 patients required reintervention due to recurrent radicular (n=2) or screw-related (n=2) pain., Conclusions: The minimally invasive presacral axial interbody fusion and posterior instrumentation technique is a safe and effective treatment for low-grade isthmic spondylolisthesis.

Study Design: Prospective case series, Objective: This was designed to precisely measure motion after posterior dynamic stabilization using Dynesys instrumentation., Summary of Background Data: The Dynesys posterior dynamic stabilization system, which stabilizes the spinal segment while potentially decreasing the risk of adjacent segment disease, is undergoing evaluation by the US Food and Drug Administration for treatment of degenerative spondylolisthesis without fusion. Evaluation of adjacent segment disease requires precise characterization of motion on the surgical level. Unfortunately, routine clinical radiographic techniques are imprecise and unreliable for full characterization of spinal segment motion. Radiostereometric analysis, which is very precise and reliable for in vivo measurement of motion, was used to examine spinal segment motion after dynamic stabilization with Dynesys., Methods: Six patients (age 59+/-7 y) underwent posterior decompression followed by posterior stabilization using Dynesys instrumentation (4 one-level, 2 two-levels). Three to 5 tantalum beads were placed in each vertebral body. Postoperative biplanar radiographs were obtained in flexion, extension, right, and left lateral bending, and 3-dimensional reconstruction was performed using radiostereometric analysis at 3, 6, 12, and 24 months postoperatively. The translations and rotations of the superior vertebral body were measured relative to the inferior vertebral body., Results: Over the 24-month follow-up period, mean flexion, extension, left, and right lateral bending of the motion segments were noted to be 1.0 degrees, 2.4 degrees, 0.6 degrees, and 0.6 degrees or less, respectively. There were no statistically significant changes in the degree of motion. During follow-up, no significant changes in neutral position of the device were noted in any of the 3 planes, and minimal translation was noted in the postoperative period., Conclusions: The Dynesys dynamic instrumentation system seems to stabilize degenerative spondylolisthesis. As expected in the degenerative lumbar spine, the segmental motion of the implanted level in this study was limited and considerably less than normal spinal motion.

Study Design: Prospective, nonrandomised, single center., Objective: To study the clinico-radiologic and functional outcome after transfacetal screw fixation and fusion for low-grade degenerative spondylolisthesis of the lumbar spine., Summary of Background Data: Surgery for degenerative spondylolisthesis conventionally involves instrumented fusion using 3 column pedicle screw fixation systems. Recently transfacetal fusion techniques have been reported to produce good results without the surgical morbidity associated with posterolateral fusion and the neurologic complications associated with pedicle screw fixation., Methods: 30 patients with low-grade degenerative spondylolisthesis of the lumbar and lumbosacral spine underwent transfacetal fusion using 2 cortical screws and local cancellous bone grafts., Results: Clinical and radiologic evidence of fusion was obtained in 29 patients. One patient developed pseudoarthrosis with progression of slip and was reoperated. Quadruple visual analog scores and Oswestry disability assessment showed a significant improvement at 1-year follow-up., Conclusions: Degenerative spondylolisthesis with lower grade slips and normal anterior structures represent an ideal indication for transfacetal fusion. This is a simple and useful technique for short segment fusions of the lumbar spine.

Study Design: Retrospective clinical study to compare the percutaneous screw placement precision of isocentric C-arm (Iso-C) 3-dimensional fluoroscopy-navigated pedicle screw implantation and conventional fluoroscopy., Objective: The purpose of this study was to evaluate the accuracy of clinical percutaneous pedicle screw placement (PPSP) using Iso-C 3-dimensional fluoroscopy navigation., Summary of Background Data: The technique of PPSP recently has been applied to internal fixation for segmental lumbar instability as a form of minimally invasive spine surgery. The percutaneous insertion technique requires surgical skill and experience. The 3-dimensional fluoroscopy-based image-guidance navigation system has been proven to be effective in guiding accurate PPSP in the lumbar area of cadavers. However, there have been few clinical reports comparing the accuracy of Iso-C 3-dimensional fluoroscopy-navigated pedicle screw implantation and the conventional fluoroscopy method., Methods: Here, 300 percutaneous pedicle screws were evaluated; half of them were inserted under Iso-C 3-dimensional navigation and the others under fluoroscopy. The accuracy of pedicle screw placement was examined postoperatively using an axial 2-mm slice computed tomography. Screw malpositioning was classified either as exposed screw (<50% of the screw outside the pedicle) or perforated pedicle (>50% of the screw outside the pedicle boundaries)., Results: Of the 150 pedicle screws placed with Iso-C 3-dimensional fluoroscopy-based image-guide assistance, 11 (7.3%) were classified as exposed screws and 0 (0%) as perforated pedicle. Of the 150 pedicle screws inserted under fluoroscopy, 18 (12%) were classified as exposed screw and 5 (3.3%) as perforated pedicle. The difference in frequency of screw misplacement between the procedure using Iso-C 3-dimensional fluoroscopy-based image-guide assistance and that using fluoroscopy was statistically significant (P<0.05; chi test)., Conclusions: This study demonstrates the feasibility of placing percutaneous posterior lumbar pedicle screws with the assistance of Iso-C 3-dimensional navigation.

Study Design: Retrospective cohort study., Objective: The objective of this study is to document and review the surgical technique and the clinical and radiographic outcomes after instrumented reduction and transforaminal lumbar interbody fusion of mid and high-grade adult isthmic spondylolisthesis., Summary of Background Data: Although high-grade slips make up a distinct minority of all patients afflicted with spondylolisthesis, approximately 2% in most series, the treatment of this small cohort of patients has been the topic of on going, and often heated debate. Recently, there has been a trend in the literature toward the combination of instrumented posterior spinal fusion (PSF) and interbody fusion with or without reduction. Although spine surgeons have used this procedure as a tool to treat patient's with spondylolisthesis of any cause, there is no report in the literature describing the results of neural element decompression, transforaminal interbody fusion (TLIF) reduction, and instrumented PSF of the listhetic vertebrae in the treatment of high and mid-grade isthmic spondylolisthesis., Methods: From 1999 to 2003, 13 patients with mid and high-grade isthmic spondylolisthesis (Meyerding grades II, III, or IV) who failed conservative treatment were treated by posterior lumbar decompression, TLIF at the disk space of the level of the slip, instrumented PSF, and reduction of the listhetic vertebrae. Standing lumbar radiographs were taken preoperatively, at the time of the initial postoperative visit and at regular intervals thereafter. Several radiographic parameters were noted including degree of anterolisthesis, slip angle, sacral inclination, and disk height. Statistical comparisons were made with 2-tailed paired t tests., Results: The average anterolisthesis, normalized to the superior endplate diameter, was 51.0%+/-16.6% preoperatively, 13.2%+/-11.8% immediately postoperative, and 17.0%+/-12.6% at final follow-up (Table 1). Of the 10 patients with sufficient radiographic follow-up, all but one had radiographic evidence of solid bony union at the time of final radiographic examination. Follow-up averaged 21.5 months and ranged from 11 to 48 months., Conclusions: This study represents a unified approach to the solitary diagnosis of mid and high-grade adult isthmic spondylolisthesis, adding further information to the growing body of literature for the TLIF procedure.

Study Design: A preliminary study about extraforaminal lumbar interbody fusion (ELIF) technique for the treatment of isthmic spondylolisthesis., Objective: To introduce a new surgical fusion technique for isthmic spondylolisthesis with minimally invasive procedure., Summary of Background Data: Posterolateral fusion, posterior lumbar interbody fusion, and anterior lumbar interbody fusion with posterior fixation are the options of the surgical treatment for isthmic spondylolisthesis. Still, complications can be related to these approaches. The authors tried to approach directly to lesion-the exiting nerve root, to decompress and to stabilize with minimally invasive procedure. Through extraforaminal approach, we can expose the exiting nerve root only to perform interbody fusion without intra-abdominal dissection or exposing central dura and traversing nerve root., Methods: Five patients with isthmic spondylolisthesis underwent ELIF with percutaneous pedicle screw fixation (PPF) between August 2005 and April 2007. In all subjects, the 3-cm-long posterior skin incisions were made bilaterally about 6 to 8 cm lateral from the midline. The multifidus muscle was separated with blunt dissection from the longissimus muscles. We identified the isthmus and neural foramen, removed fibrocartilage and the lateral border of ligamentum flavum covering the exiting nerve root, separated the soft tissue attached to the root and the transverse process, and retracted the root to perform discectomy. We prepared the endplates, cages with allograft, inserted them under C-arm fluoroscopic guidance, and performed the procedures on the contralateral side. After the arthrodesis, posterior instrumentation was augmented with PPF., Results: Five patients underwent ELIF+PPF; despite a small number of cases, the outcomes were satisfactory., Conclusions: ELIF technique makes exposing only the exiting nerve root easy to perform interbody fusion without violating either the abdominal cavity or the posterior musculoligamentous and the bony stabilizers of the spine. This may be considered as one of the minimally invasive surgical options for isthmic spondylolisthesis.

Study Design: Retrospective clinical data analysis., Objective: To compare clinical results with radiologic results of 2 fusion techniques for adult low-grade isthmic spondylolisthesis., Summary of Background Data: There is clear evidence that lumbar interbody fusion using anterior and posterior approaches provides a high fusion rate, good sagittal alignment, and good clinical outcomes. However, there are no recent studies that compare these 2 fusion techniques., Methods: Between March 2004 and December 2004, 48 patients underwent instrumented mini-anterior lumbar interbody fusion (ALIF) and 46 underwent instrumented mini-transforaminal lumbar interbody fusion (TLIF). The mean follow-up periods were 32.6 and 29.7 months, respectively., Results: The mean visual analog scale (VAS) scores for back and leg pain decreased, respectively, from 7.7 and 7.5 to 2.9 and 2.7 in the ALIF group and from 7.0 and 6.3 to 2.3 and 2.2 in the TLIF group. The mean Oswestry disability index (ODI) scores improved from 51.4% to 23.2% in the ALIF group and from 52% to 14.4% in the TLIF group. In both groups, the VAS and ODI scores significantly changed preoperatively to postoperatively (P<0.001). However, statistical analysis showed no significant difference in postoperative VAS/ODI scores between groups. Radiologic evidence of fusion was noted in 95.8% and 92.3% of the patients in the ALIF group and the TLIF group, respectively. In both the groups, changes in the disc height, segmental lordosis, degree of listhesis, and whole lumbar lordosis (WL) between the preoperative and postoperative periods were significant except for WL in the TLIF group. The amount of change between preoperative and postoperative disc height, segmental lordosis, and WL demonstrated significant intergroup differences (P<0.05)., Conclusions: The mini-ALIF group demonstrated key radiographic advantages compared with the mini-TLIF group for adult low-grade isthmic spondylolisthesis. However, clinical and functional outcomes did not demonstrate significant differences between groups.

Study Design: A clinical retrospective study was conducted., Objective: To evaluate the clinical and radiographic outcomes of 25 consecutive patients with symptomatic high-grade isthmic spondylolisthesis at L5-S1 treated by decompression and transvertebral, transsacral strut grafting with fibular allograft., Summary of Background Data: Symptomatic high-grade isthmic spondylolisthesis serves as a challenging clinical problem. Traditional treatment by in situ posterolateral arthrodesis has been associated with pseudarthrosis rates up to 50%. Even with successful posterolateral fusion, the graft is in an unfavorable biomechanical environment, owing to it being under tension, which can allow for progression of lumbosacral kyphosis (slip angle) and sagittal translation (slip). Open reduction of spondylolisthesis improves the biomechanical situation by allowing a trapezoidal interbody graft at L5-S1, but is associated with neurologic deficits in up to 30% of patients. The technique used in this particular study achieves the biomechanical goal of a structural interbody construct without the necessity of anatomically reducing the translational slip. The fibular strut grafts were placed through an anterior approach as part of an anterior/posterior procedure, or via a posterior approach as part of a posterior-only procedure., Methods: A consecutive series of 25 symptomatic patients with high-grade isthmic spondylolisthesis at L5-S1 had an average age of 29.8 years. Six patients were 16 years or younger. Eight patients underwent a posterior-only approach with posterior transosseous fibular strut grafting across S1 into the L5 vertebral body combined with posterolateral arthrodesis L4-S1 using a pedicle screw-rod construct. Seventeen patients underwent a combined anterior/posterior approach with transosseous fibular allograft strut grafting at L5-S1 and L4-L5 interbody arthrodesis using a femoral ring allograft supplemented with L4-S1 posterior pedicle screw-rod instrumentation. No reduction attempts were performed, other than those occurring spontaneously by patient positioning and decompression. Patients were evaluated for clinical improvement and radiographically. Clinical outcomes were measured with the scoliosis research society outcome instrument. Radiographs were followed for arthrodesis, translation, and slip angle. Mean follow-up was 39 months (range, 30 to 71 mo). All patients preoperatively had a grade III to V slip using the Meyerding classification (mean 3.7). The slip angle averaged 37 degrees., Results: The postoperative mean slip grade was 3.5 compared with 3.7 preoperatively (no significant difference). The mean slip angle improved to 27 degrees (8 to 40 degrees) postoperatively from 37 degrees (13 to 51 degrees) preoperatively (P<0.05). All patients went on to a stable arthrodesis, with no progression in slip or slip angle. There were no permanent neurologic deficits among any of the subjects, and all patients demonstrated improvement in their preoperative gait disturbance. Scoliosis research society functional outcome score showed 24/25 extremely satisfied or somewhat satisfied at latest follow-up., Conclusions: Treatment by this method showed improvement in lumbosacral kyphosis while avoiding the neurologic injury risk associated with open slip-reduction maneuvers. Despite no reduction in translational deformity, this technique offers excellent fusion results, good clinical outcomes, and prevents further sagittal translation and lumbosacral kyphosis progression.

Objectives: The surgical approach that should be used for degenerative spondylolisthesis (DS) is a controversial issue. Decompression and posterolateral fusion (PLF) with or without lumbar interbody fusion is widely used. Many studies have compared the outcomes of these 2 approaches, but the appropriate indications for these approaches are still unclear. The authors retrospectively studied the effects of posterior lumbar interbody fusion (PLIF) after PLF for the treatment of DS., Methods: Forty patients who underwent single level decompression and posterior instrumentation for DS at L4-5 and were followed for at least 2 years were retrospectively studied. The patients were divided into 4 groups: the stable PLF group (S-PLF, n=13); the stable PLF with additional PLIF group (S-PLIF, n=11); the unstable PLF group (U-PLF, n=8); and the unstable PLF with additional PLIF group (U-PLIF, n=8). Clinical and radiographic comparisons were carried out between the S-PLF and S-PLIF groups, and between the U-PLF and U-PLIF groups., Results: Clinical assessments, using the improvements of the Oswestry Disability Index (ODI) and the Visual Analog Scale (VAS), were statistically significantly different between the 2 unstable groups (DeltaU-PLF DeltaS-PLIF, P=0.029), and the disc height increment was significantly different between the 2 stable groups (DeltaS-PLF

Study Design: Prospective, matched, and controlled study., Objective: To evaluate the efficacy of hydroxyapatite-bioactive glass ceramic composite (Chitra-HABg) as a stand-alone graft substitute in promoting posterolateral fusion in the lumbar spine as compared with autologous bone., Background: The use of ceramics as stand-alone graft substitutes in posterolateral fusion remains controversial. The Chitra-HABg is a new composite that has undergone clinical trials in various orthopedic applications with excellent clinical and radiologic outcomes., Methods: Twenty-four patients underwent instrumented posterolateral fusion, with Chitra-HABg laid on the left intertransverse bed and autogenous graft on the right side. The primary outcome measure was radiologic consolidation of the graft, and secondary outcome measures were the work status and the Modified Oswestry Disability index. The McNamara and Student chi test were applied for statistical analysis., Results: Although the study was prematurely terminated owing to the high incidence of resorption of Chitra-HABg, 22 of the 24 subjects were followed-up for a minimum of 1 year. At the end of 1-year, excellent radiologic outcome was seen on the right side (autogenous graft) in all the cases, whereas 95% (21/22) of the cases had poor consolidation on the left side (Chitra-HABg). The clinical outcome was rated as good in 16/22 (73%) patients, fair in 5, and poor in only 1 patient, but this had no statistically significant association with the consolidation of the fusion mass., Conclusions: This study clearly demonstrates that hydroxyapatite-bioactive glass ceramic composites (Chitra-HABg) has no role as stand-alone bone graft substitutes in posterolateral fusion of the lumbar spine, as the composite undergoes resorption without the formation of bridging callus., Level of Evidence: Level 1.

Study Design: Retrospective study of surgical technique and clinical outcome., Objectives: To examine the technique and outcomes of anterior lumbar interbody fusion (ALIF) surgery for a lumbosacral junction in a steep sacral slope., Summary of Background Data: There are no studies on the outcome and technical pitfalls on ALIF surgery for a lumbosacral junction in a steep sacral slope., Materials and Methods: Six female patients (mean age of 55.67 y; range, 42 to 69) who had a steep sacral slope underwent ALIF surgery for degenerative (2 patients) and spondylolytic (4 patients) spondylolisthesis. The average follow-up duration was 29.33 months (range, 27 to 33 mo). The following parameters were used to assess the outcomes: slip angle, slip percentage, sacral inclination, lumbosacral angle, sacral slope, and distance from the upper margin of the pubis symphysis to the sacral plane. The level of pain was measured using the visual analog pain scale score. The function was assessed using the Oswestry Disability Index (ODI) score. Satisfaction surveys were also carried out. Statistical analysis was performed using a Friedman test. A P value <0.05 was considered significant., Results: The mean sacral inclination, lumbosacral angle, sacral slope, and distance from the upper margin of the pubis symphysis to the sacral plane were 37.34 degrees (range, 28.55 to 48.92 degrees), 12.20 degrees (range, 5.09 to 16.5 degrees), 40.70 degrees (range, 30.54 to 49.98 degrees), and 22.06 cm (range, 16.13 to 29.72 cm), respectively. The mean correction of slip percentage and slip angle was 35.46%, and 9.3 degrees, respectively. The mean visual analog pain scale score decreased from 8.5 (back pain) and 7.3 (leg pain) to 1.8 (back pain) and 1.8 (leg pain) after surgery (P=0.001). The mean ODI scores also reflected the improved status (ODI of 64.7 before surgery to 8.5 after surgery; P=0.001). The patient's satisfaction was relatively high. All the patients had radiographically solid fusion at the latest follow-up. There were no significant complications encountered in this study., Conclusions: In selected cases, a steep sacral slope may not be an absolute contraindication of ALIF. Moreover, the C-arm-guided reduction and cage insertion method is a reliable way of treating spondylolisthesis in those with a steep sacral slope.

Since the Food and Drug Administration approved the Babgy-Kuslich BAK cage for anterior lumbar interbody fusion (ALIF), various threaded interbody fusion devices have been introduced. Bone dowels offer several theoretical advantages over cages with regard to stress shielding; the purpose of this study was to assess the efficacy of bone dowels in interbody fusion. All patients undergoing ALIF performed by the senior author between 1998 and 2001 were retrospectively reviewed. Patients' preoperative and postoperative neurologic status, functional status, and both back and radicular pain were assessed according to a previously published outcome measure. Between 1998 and 2000, 23 patients underwent ALIF with cortical femoral allograft bone dowels. One patient underwent simultaneous bone dowel and titanium cage placements and was therefore excluded from further analysis. The 22 remaining patients underwent a total of 33 fused segments; of these, 21 patients were available for follow-up. Mean clinical follow-up was 30.6 months. Mean imaging follow-up was 21 months. There were 5 instances of radiographic nonunion (3 symptomatic and 2 asymptomatic). The incidence of technical failures and complications related to the bone dowels was 17%. Bone dowels failed and caused symptoms only in patients with a stand-alone ALIF. There were no clinical failures in patients treated with supplemental anterior or posterior spinal fixation. These data demonstrate that marginal fusion rates and functional success rates can be achieved using stand-alone bone dowels for ALIF. The clinical success and fusion rates are significantly higher if ALIF dowels are shielded from stress with rigid spinal instrumentation.

Introduction: In scoliosis patients treated with long segment spinal fusion, degenerative changes like retrolisthesis and disc space narrowing below fusion have been observed. However, there is disagreement concerning their incidence and dependency on the location of the lowest instrumented vertebra., Materials and Methods: To evaluate temporal changes in disc height and posteroanterior displacement (indicating listhesis) below fusion, 40 patients with adolescent idiopathic scoliosis, mainly treated with Cotrel-Dubousset instrumentation, were retrospectively investigated in this longitudinal study with a follow-up of on average 9.2 years (median 9.4 y) after surgery. Disc height and displacement were measured from lateral radiographs by means of distortion-compensated roentgen analysis (DCRA). Additionally, a mathematical model was developed to determine the influence of vertebral tilt in scoliosis on disc height and displacement., Results: Overall, no significant decrease in disc height was observed during follow-up. Concerning listhesis a small but significant retrolisthesis was found in segments L2/L3 and L3/L4. Compared with normative data, there was no significant listhesis for the L5/S1 segment. Nevertheless, separating the study group into subsamples of identical distal fusion level revealed a significant correlation between the amount of posteroanterior displacement at L5/S1 and the location of the lowest instrumented vertebra. With a reduction of free motion segments, listhesis increased into posterior direction. Taking the tilt correction into account led to considerably increased values of disc height whereas displacement was affected only to a minor degree., Conclusions: Long segment spinal fusion in young patients with idiopathic scoliosis did not lead to disc space narrowing during 9.2 years follow-up. However, the observed increase in retrolisthesis potentially indicates the initiation of a degenerative process. These only minimal changes might be referred to the preservation of a physiologic lumbar lordosis. Without correction for vertebral tilt disc space narrowing is overestimated.

Objective: Stabilization of the cervicothoracic junction is challenging but commonly required in patients with traumatic, neoplastic, congenital, and postlaminectomy conditions. Although extensive research has been performed on stabilization of the cervical spine, there remains a paucity of published data on instrumentation at the cervicothoracic junction. Using 2-column, 3-column, and corpectomy instability models, a biomechanical analysis was performed on the effects of increasing the number of posterior segmental fixation points and/or anterior column reconstruction at the cervicothoracic junction., Methods: Multidirectional flexibility testing was performed utilizing a 6-degree-of-freedom spine simulator and 7 fresh-frozen human cadaveric spines (occiput-T6). After intact spine analysis, each specimen was destabilized and reconstructed as follows: (1) C7/T1 2-column injury with posterior instrumentation; (2) C7/T1 3-column injury with posterior instrumentation; (3) C7/T1 3-column injury with anterior interbody cage/plate and posterior instrumentation; and (4) C7/T1 3-column injury plus C7 corpectomy with anterior cage/plate and posterior instrumentation. All reconstruction groups were tested with posterior instrumentation (screws connected by dual-diameter rods) from C5-T1, C5-T2, and C5-T3., Results: For 2-column injuries, there were no statistically significant differences in flexibility (P>0.05), although there was a trend toward reduced flexibility with increasing levels of thoracic fixation. For 3-column injuries, posterior fixation alone resulted in excessive flexibility in flexion/extension even with instrumentation to T3 (P<0.05). With the addition of anterior column instrumentation, there were no observed differences in flexion/extension and lateral bending. For axial rotation, instrumentation to T1 alone demonstrated increased motion relative to the intact spine (P<0.05). The 3-column injury with corpectomy model demonstrated similar flexibility properties to the 3-column injury model., Conclusions: With 3-column instability posterior segmental fixation alone from C5-T3 was inadequate, and the addition of anterior instrumentation restored flexibility to the intact condition. There was a strong trend toward reduced flexibility with increasing levels of thoracic fixation in all instability models.

Objective: To review the operative time differences between computer-assisted spinal navigation versus serial radiography., Summary of Background Data: There have been multiple studies describing the use of computer-assisted image guided surgery (IGS) in the application of spinal instrumentation. Techniques have evolved to allow attainment of multilevel visualization intraoperatively both successfully and safely. These have proven to result in low screw misplacement rates, low incidence of radiation exposure and excellent operative field viewing. As a result, image guidance has become an increasingly accepted and practiced form of intraoperative spinal navigation. However, potential limitations to IGS have been described including longer operating times. Many studies have looked at the success of beneficial outcomes; however, none to our knowledge have reviewed such described operative time increments with IGS., Methods: The authors performed a retrospective database analysis of 105 patients undergoing posterior L5-S1 spine fusion with pedicle screw instrumentation for isthmic spondylolisthesis with and without the use of fluoroscopy-based image guidance. This was followed by a chart review of anesthesia operative time documentation. Subsequent time calculations and statistical analysis were performed for comparison., Results: Computer-assisted image-guided spine surgery has overall demonstrated shorter mean operative times when compared with intraoperative serial radiography technique; an average of 40 minutes less per case (P<0.001). There is also less variation in operative times using image guidance, with 13 of 43 (30%) cases using serial x-ray lasting more than 3.75 hours compared with none of the 57 done via image guidance (P<0.001). The operative duration for both procedures trended downward over time. For both procedural cohorts operating room time continued to decrease as of the most recent year being performed. Lastly, in an attempt to minimize such a confounding factor as a learning curve, the last 20 cases in each group were compared. There was an average difference of about 22 minutes less for the image guidance group but missed being statistically significant (P=0.0503)., Conclusions: Image-guided spinal surgery did not cause an increase in operative time. In the best scenario, image navigation saved a statistically significant (P<0.001) amount of time in the operating room. At its worst, fluoroscopy-based image-guided navigation is not significantly different from standard serial radiography.

Introduction: Spondylolysis and spondylolisthesis grade 0, 1, and 2 are mainly asymptomatic but with aging process and different factors some back pain can occur and lead to chronic low back pain. The conservative treatment with physiotherapy and steroid injection is the gold standard but in some cases is not efficient enough and a surgical treatment is proposed., Objectives: The goal of this study is to propose a new technique to treat grade 0, 1, and 2 spondylolisthesis with an anterior video-assisted fusion and stabilization., Methods: Twenty patients with chronic low back pain since more than 2 years and resistant to conservative therapy were included in this protocol. Clinical signs and radicular pain were noted. They were evaluated preoperatively and postoperatively until the last follow up using Oswestry score and visual analog score (VAS) for leg and back pain. X-rays showed grade 0 (8 cases), 1 (10 cases), and 2 (2 cases) spondylolisthesis according to Meyerding classification with disc collapse (bulging disc). MRI showed in all cases a disc degeneration with at least black disc and/or endplates changes with Modic I or II. All patients were operated using an anterior video-assisted retroperitoneal approach, with discectomy and fusion using an anterior impacted cage filled with autologous cancellous bone from the iliac crest and an anterior fixation with a triangular plate (Pyramid, Medtronic, Memphis). The follow up at 3, 6, 12, and 24 months was done with clinical and radiologic evaluation. In case of problem a computed tomography scan was performed., Results: There were 11 women and 9 men, with and average age of 39 years old and a BMI of 25.6. All spondylolistheses occurred at level L5. The average slippage was 19%. All L5S1 discs were black, 8 had a Modic I changes in the endplates and 2 had Modic II. The shape of L5 vertebra was abnormal (trapezoidal) in 7 cases. All anterior approaches were performed without vascular, urologic, or digestive complication. Blood loss was inferior to 100 mL. All patients had a soft brace for 8 weeks postoperatively. There was no retrograde ejaculation for the 9 men and no sexual dysfunction reported by the women. One patient had no pain relief and was reoperated for posterior pedicular screw fixation. It was obvious that there was a pseudarthrosis even after the posterior fixation and an anterior transperitoneal revision was performed with the removal of the interbody device and iliac crest bone graft packing alone. A propioni bacterium acnes germ was found responsible for the anterior nonunion. This revision surgery with antibiotics treatment was successful. One of the patients with grade 2 had an additional posterior screw fixation with a minimally invasive pedicle screw system (Sextant, Medtronic, Memphis). Nineteen patients had a good fusion at 2 years follow-up (95%), mean Oswestry score improved from 74% preoperative to 21% postoperative at the last follow-up. Visual analog score (VAS) for back pain improved from 6.5 to 2.7 and VAS for leg pain improved from 6.2 to 3.4. Satisfaction rate was 90%. All active patients except two, were back to work at an average of 5.5 months (6 wk to 1 y). The 2 patients still not working were the nonunion and a work compensation., Conclusions: The results of this technique compare favorably with posterior stabilization and fusion (posterior lumbar interbody fusion and postero-lateral fusion) reported in the literature. Unlike posterior lumbar interbody fusion, however, it seems that the complication rate due to the approach is much lower, the fusion rate is similar. Grade 2 SPL is the limitation of the technique. The main advantage of the technique is to avoid posterior muscle damage and a quick recovery with no blood loss. Preservation of adjacent level disease can be assessed only after long-term follow-up.

Introduction: This study determines whether recombinant human bone morphogenetic protein-2 (rhBMP-2) (12 mg at the rate of 1.5 mg/mL) delivered on an absorbable collagen sponge with an added bulking agent can increase posterolateral lumbar spine fusion success rates and decrease time for fusion with autogenous bone grafts., Method: A prospective, single institution, clinical case-matched, radiographic, cohort study was undertaken. A total of 52 patients underwent posterolateral lumbar arthrodesis with pedicle screw instrumentation. The experimental group (n=41) underwent placement of Iliac crest bone graft (ICBG) with InFUSE (12 mg/level at the rate of 1.5 mg/mL). The control group (n=11) consisted of sex-matched patients, consecutively collected over the same time period with an instrumented posterolateral arthrodesis and ICBG placed in the intertransverse space., Outcome Measures: Thin-cut (2 mm) axial, coronal, and sagittal reconstructions were blindly evaluated for evidence of bridging bone and cortication of the fusion mass by 3 separate reviewers. Fusions were graded and an overall score was given to the quality of the fusion mass., Results: Fifty patients (ICBG alone n=11; ICBG/rhBMP-2 n=39) were available for CT evaluation at 2-year follow-up. An overall 97% (68/70 levels; Definite+Probably Fused) fusion rate in the rhBMP-2 group was achieved as compared to the 77% fusion rate (17/22 levels) in the ICBG alone group (P<0.05). In the rhBMP-2 group, 92% of the patients (36/39 patients) received an overall excellent subjective fusion rating as compared to 27% (3/11) in the control group (P<0.05). There was no computed tomographic evidence of soft-tissue ossification, dural ossification, or laminar bone regrowth in any patient., Conclusions: The adjunctive use of rhBMP-2 and ICBG seems to be safe and results in significantly larger and more consistent posterolateral fusion masses.

Objective: We retrospectively reviewed the results of 100 consecutive transforaminal lumbar interbody fusions (TLIFs) performed at one institution. The preoperative diagnoses included degenerative disk disease (55), spondylolisthesis (41; 22 isthmic, 19 degenerative), and degenerative adult scoliosis (4). There were 64 single-level, 33 two-level, 2 three-level, and 1 four-level TLIF (140 levels)., Methods: The fusion mass was assessed by an independent observer using biplanar radiography, whereas clinical outcomes were assessed by means of several established outcome measures., Results: By level, the posterolateral fusion was judged to be probably or definitely solid in 78% of levels, whereas the interbody fusion was radiographically solid in 88% of levels, for an overall 93% fusion success/patient (94%/level). All patients had >24 months of postoperative clinical follow-up, and 82 patients (82%) were available for outcome measure assessment at an average follow-up of 34 months (range 24-61 months) postoperatively. Eighty-one percent of these patients reported a >50% decrease in their symptoms, and 76% of patients were satisfied with their results to the degree that they would have the procedure again. However, a large percentage of patients experienced incomplete relief of their symptoms. Twenty patients sustained minor complications, and there were no major complications., Conclusions: We conclude that TLIF is a safe and effective method of achieving lumbar fusion with a 93% radiographic fusion success and a nearly 80% rate of overall patient satisfaction but frequently results in incomplete relief of symptoms. Complications resulting from the procedure are uncommon and generally minor and transient.

Lumbosacral dislocations are rare high-energy injuries most often reported as isolated cases. Improved outcomes from major trauma means that these cases will likely become more common. We report six cases treated at our institution in the last decade. Nonoperative care in two cases resulted in severe deformity and pain and required late reconstruction. Surgical decompression, reduction, and stabilization with posterior pedicle screw instrumentation resulted in a stable lumbosacral junction, although in one case, implant failure required revision with anterior column reconstruction to achieve that stability. Nerve root injuries recovered. Two cases had pre-existing spondylolysis/spondylolisthesis. Clinical results were very satisfactory if there was no pre-existing chronic low back pain, although overall function was determined by outcome from other injuries sustained at the initial trauma.

Objective: A systematic review of the radiographic and clinical outcomes of adult patients undergoing surgery for low-grade isthmic spondylolisthesis was performed to determine whether conclusions could be made regarding the optimal choice of surgically managing adult low-grade isthmic spondylolisthesis., Methods: We tabulated the radiographic and clinical outcomes of patients who underwent a posterior procedure alone, an anterior procedure alone, or a combined anterior and posterior procedure. We also evaluated the influence of covariates such as laminectomy, spinal internal fixation, smoking, and secondary gain issues on these outcomes. Patients were pooled, and a chi analysis was performed to determine the relationship between surgical approach and patient outcome. A covariate analysis was performed to determine the influence of a laminectomy, spinal fixation, smoking, and secondary gain issues on these outcomes., Results: The available literature consisted primarily of retrospective case series, with only 4 of 34 reports being prospective randomized controlled studies. Patients with combined anterior and posterior procedures were most likely to achieve a solid fusion and a successful clinical outcome. The use of spinal fixation also increased the chance of fusion and successful clinical outcome., Conclusions: A pooling of the surgical literature on adult low-grade spondylolisthesis indicates that a combined anterior and posterior procedure most reliably achieves fusion and a successful clinical outcome. The literature, however, is primarily retrospective and heterogeneous with respect to indications for surgery and methods of evaluating outcome, providing a compelling rationale for a prospective randomized controlled trial of the various surgical approaches to this problem.

Posterior lumbar interbody fusion (PLIF) is a standard surgical technique for the lumbar degenerative diseases. However, some problems such as collapse or retropulsion of the grafted bone and pseudoarthrosis have been reported when autogenous or cadaveric bone is used. Two iliac bone blocks with one-side cortex and one dense hydroxyapatite (HA) block were grafted together into the interbody space as in a sandwich. Cancellous bone chips locally harvested were also grafted onto the anterior and lateral aspect of the HA block. Twenty-six patients (12 males, 14 females) who could be followed minimally for 2 years were examined. The surgical outcome of each patient was evaluated by the Japanese Orthopaedic Association Assessment of Treatment of Low Back Pain (JOA score) and the recovery rate. Radiographic evaluation was based on the extent of bony union, the presence of a clear zone in the upper or lower margin of the HA block, cracking of the HA block, sinking of the HA block, and changes in lumbar-sagittal alignment pre- and postoperatively. The overall recovery rate ranged from 42.9% to 100% (mean 88.3%). Bony union was confirmed in 25 patients (96.2%). Clear zone was observed in 9 of 68 contact surfaces (13.2%). Sinking was observed in 8 of 34 segments (23.5%), and cracking of HA block was observed in 6 segments (17.6%). A mean loss of lordosis was found to be 2.4 degrees . The dense HA block is a useful substitute for autogenous bone graft for PLIF.

Purpose: The existing literature lacks a functional outcomes study addressing instrumented posterior lumbar fusion surgery for isthmic spondylolisthesis in physically active patients. Presently, spinal surgeons can provide only anecdotal advice when discussing operative outcomes with these patients. This is a nonrandomized analysis of consecutive military servicemen treated operatively for chronic back pain and low-grade isthmic spondylolisthesis with single-level lumbar disc degeneration with emphasis on functional outcomes. The purpose was to evaluate patient-assessed function/pain/satisfaction and military job performance in U.S. servicemen treated with posterior lumbar interbody fusion (PLIF)., Methods: Thirty consecutive U.S. military servicemen with chronic low back pain and low-grade lumbar isthmic spondylolisthesis were referred to the same surgeon at a military treatment facility. All servicemen were treated operatively with instrumented PLIF using autogenous iliac crest bone graft, one or two nonthreaded interbody cages (Brantigan or Harms), and a four-pedicle screw/rod construct. A concomitant bilateral posterolateral fusion was performed in all 30 cases. The average follow-up time was 15 months (range 12-48 months). Twenty-five of the 30 servicemen completed a functional outcomes questionnaire (American Academy of Orthopaedic Surgeons/Scoliosis Research Society) with emphasis on pre- and posttreatment function, pain, and satisfaction. The servicemen were also evaluated using standard military job performance parameters., Results: Three of the 30 servicemen (10%) requested and received a disability discharge from the military for back pain that continued throughout the postoperative period and prevented return to military duty. An additional 8 of the original 30 soldiers (27%) required some form of permanent physical activity limitation (situps/pushups/running/lifting) to permit their return to military duty, and 19 of 30 (63%) soldiers were able to return to full and unrestricted military duty after surgery. Those soldiers who were able to return to unrestricted military duty (n = 19) did so at an average of 6 months post treatment (range 2-16 months). Of the soldiers who were able to return to military duty, 21 of 30 (70%) were able to complete the posttreatment military physical fitness test at an average of 8 months postoperatively (range 2-32 months). No significant differences were observed between premorbid and postsurgical physical fitness test scores. There was a trend toward lower postsurgical scores. Complications included dural tear (n = 4), unilateral transient lower extremity paresthesia (n = 1), and wound seroma requiring reoperation (n = 1)., Conclusions: In this nonrandomized study of 30 U.S. servicemen with chronic low back pain, low-grade isthmic spondylolisthesis, and single-level lumbar disc degeneration, instrumented PLIF surgery was associated with a high rate of return to functional military duty. Outcomes with respect to posttreatment pain, function, and satisfaction were high in patients treated with instrumented PLIF.

Objective: 76 patients who underwent laminoplasty for cervical spondylotic myelopathy were investigated regarding the impact of preoperative and postoperative degenerative spondylolisthesis on their neurologic outcome., Methods: Radiographs were obtained 1 year postoperatively to investigate range of motion (ROM), lordotic curvature, and postoperative spondylolisthesis., Results: By 1 year after surgery, 85% of those spondylolistheses present preoperatively had either resolved or improved on neutral lateral radiographs. The cross-sectional area of the spinal cord at the site of spondylolisthesis was measured using preoperative computed tomography myelography. Clinical results were evaluated by the recovery rate using Japanese Orthopaedic Association score. Patients with posterior spondylolisthesis showed a significantly poorer postoperative recovery rate. Intervertebral ROM in patients with preoperative spondylolisthesis was reduced, whereas cervical alignment had not deteriorated after laminoplasty. The group with posterior spondylolisthesis showed a significant reduction in the cross-sectional area of the spinal cord at the site of spondylolisthesis. Postoperative spondylolisthesis appeared in 15 patients, 10 of whom had preoperative spondylolisthesis at an adjacent site., Conclusion: The cause of poorer surgical results of those patients with preoperative posterior spondylolisthesis appears to be related to a higher degree of spinal cord compression than with preoperative anterior spondylolisthesis.

Lumbar instability often causes clinical symptoms, and spondylolisthesis is a main factor of the low back pain. Segmental lumbar instability generally is due to a degenerative or listhesic process of the lumbar spine and radiological imaging is essential to diagnose it. Lumbar spine segmental mobility has commonly been studied by dyanamic radiographic methods. Dynamic X-rays, with maximal extension and flexion of the lumbar tract, represents the most widely used technique and a valid method to estimate sagittal segmental lumbar motion. Between 1998 and 2002 we treated 75 patients for low-grade spondylolisthesis. All patients underwent a preoperative dynamic X-rays examinination, to evaluate the degree of the lumbar mobility. We report a supine-prone position as new method to clearly estimate the slipping of lumbar vertebrae. The patients had a standard lateral X-rays film in the supine position, and then in the "prone" position. We compared the two methods and we found a higher degree of listhesis in 19 cases (14 I grade, 5 I-II grade), while there was no difference in 56 cases. The higher degree of listhesis was in the prone position. We believe that the supine-prone position is an economic method and should be mandatory performing a dynamic X-rays examination.

Background: The relationship between radiologic instability and its symptoms is controversial. Previous authors consider flexion-extension radiographs to be of little value in evaluating instability; however, the current authors consider the variation of results in evaluating radiologic instability to be the result of limitations in previous researchers' methods., Methods: In this report, sagittal translation and angulation at the L4-L5 segment were measured in flexion-extension films in 1,090 outpatients with low back and/or leg pain using a three-landmark measuring method. The symptoms of four groups with and without 3-mm translation and with and without 10 degrees angulation were compared for all the patients and for 280 age-matched patients using a scoring system. The age-matched patients were followed up for 4.6 years., Results: Results showed that patients with > or = 3-mm translation had significantly lower scores, indicating a limitation in their daily activities due to pain, than patients < 3-mm translation; however, no difference was observed between the groups in terms of angulation. The group with > or = 3-mm translation and > or = 10 degrees angulation significantly demonstrated the lowest scores at both evaluations during the initial visit and follow-up. This group had been suffering from low back and/or leg pain the longest and had visited the hospital significantly more often than other groups., Conclusion: In conclusion, translation of the lumbar segment has a greater influence than angulation on lumbar symptoms. The presence of both radiologic factors could be an indicator for persistence of the symptoms.

Acute traumatic L5-S1 spondylolisthesis is a rare condition, almost exclusively the result of major trauma, frequently associated with L5 transverse process fracture and neurologic deficit. In recent years, open reduction and internal fixation with posterior stabilization has been the method of treatment most frequently reported. In the current case, the lesion was found in a victim of an automobile accident. Signs of a right L5 root deficit but no sphincter dysfunction were present. A computed tomography scan revealed several fractures in the posterior parts of L5 and anterior displacement of L5 on S1. A magnetic resonance imaging (MRI) scan verified that the lesion was indeed acute by showing the ruptured L5 disc and posterior ligaments, thereby demonstrating the importance of MRI in the planning of the treatment of these lesions. This case was successfully treated with an acute circumferential instrumented L4-S1 spondylodesis.

The radiographs of 35 consecutive adult patients with isthmic spondylolisthesis who underwent a transforaminal lumbar interbody fusion (TLIF) with one or two Brantigan carbon fiber cages and pedicle screw instrumentation were evaluated. Anterolisthesis, disk space height, and slip angle were measured in preoperative and postoperative standing neutral radiographs. Anterolisthesis was reduced and disk space height was increased with the TLIF procedure. Average slip angle, however, was not significantly altered. The restoration of lordosis across the listhetic disk space correlated with a more anterior placement of the interbody cage within the disk space. The TLIF technique, performed with the Brantigan cage and pedicle screw instrumentation, appears to be able to restore disk height and reduce forward translation in patients with isthmic spondylolisthesis, but improvement in sagittal alignment is dependent upon anterior placement of the interbody device.

Lumbar shear injuries are a rare injury with few cases documented in the literature. They are the result of hyperextension combined with anteroposterior shearing forces. Those with near-complete displacement are usually associated with significant neurologic deficit. Presented here is a case of L4-L5 fracture-dislocation with no neurologic loss.

The current study is a biomechanical study using a cadaveric model of L5-S1 spondylolisthesis. The purpose of the current study was to compare, in a cadaveric model of simulated L5-S1 spondylolisthesis, the biomechanical stiffness of transdiscal fixation with traditional pedicle screw fixation, and transdiscal fixation with combined interbody/pedicle screw fixation. The surgical management of L5-S1 spondylolisthesis is a challenge because of the difficulties in achieving a reliable arthrodesis in the face of high mechanical forces. A method of lumbosacral fixation that has been used successfully in moderate grades of spondylolisthesis at our institution involves the use of transdiscal S1 pedicle screws. With this technique, S1 pedicle screws are placed through the S1 pedicle, through the superior endplate of S1, through the inferior endplate of L5, to terminate in the L5 body. Eighteen fresh human cadaveric (age 59-88 years) L5-S1 motion segments were obtained. The end of each intact motion segment was potted up to its midbody in a 10-cm-diameter polyvinylchloride end-cap using dental cement. The intact specimen was then biomechanically tested as follows: 1) axial compression (500 N), 2) flexion (10 Nm), 3) extension (10 Nm), 4) right lateral bending (10 Nm), and 5) left lateral bending (10 Nm). Stiffness values were calculated from the load-deflection curves obtained. Spondylolisthesis was then simulated by displacing L5 on S1 (% slip average = 41.3%) after performing a radical L5-S1 discectomy, L5 laminectomy, and bilateral L5-S1 facetectomies. The 18 motion segments were divided into two groups. Group I (n = 10) was biomechanically tested (as above) after pedicle screw fixation and again after replacing the S1 pedicle screws with transdiscal screws. Group II (n = 8) was biomechanically tested (as above) after combined interbody/pedicle screw fixation and again after fixation with transdiscal screws. Load-deflection curves were obtained each time, and stiffness values were calculated from the curves. Transdiscal fixation was 1.6-1.8 times stiffer than pedicle screw fixation (p < 0.05) in all loading modes tested. There were no differences in stiffness between transdiscal fixation and combined interbody/pedicle screw fixation. In a cadaveric model of simulated L5-S1 spondylolisthesis, transdiscal L5-S1 fixation produced a 1.6-1.8 times stiffer construct than traditional pedicle screw fixation. Further, the stiffness of the transdiscal fixation was equal to that of a combined interbody/pedicle screw fixation.

Posteroanterior fusion using a fibular strut autograft has been advocated for the surgical treatment of high-grade lumbosacral spondylolisthesis. We report here the treatment of a 14-year-old girl using an S2-L5 fibular autograft, which resulted in the postoperative complication of a sigmoid colon perforation. Techniques for recognizing, treating, and avoiding this complication are presented.

Degenerative lumbar spondylolisthesis with spinal stenosis is commonly treated with laminectomy. Recent reports have consistently supported the incremental clinical benefit of associated in situ arthrodesis with or without instrumentation. Resection of the lamina may result in intraoperative dural tear or epidural scar formation. Fifty-six consecutive patients with back pain, neuroclaudication, or both, in addition to degenerative spondylolisthesis with spinal stenosis, underwent a surgical procedure that incorporated fusion after reduction of the spondylolisthesis deformity with preservation of the lamina and the balance of the posterior elements. Clinical records were reviewed and patients interviewed at a mean of 33 months after surgery. Oswestry Disability Index scores were obtained independently at baseline and at a late review. Late imaging was available a mean of 28 months after operation. Clinical and imaging analyses and Oswestry scoring confirmed results comparable to the published outcomes of in situ fusion after formal laminectomy. Resection of the lamina may not be necessary in the treatment of degenerative lumbar spinal stenosis with spondylolisthesis.

Radiographs of 3,259 outpatients with low back disorders were examined for age, gender, level, direction, degree of slip, lumbar lordosis, pedicle-facet (P-F) angle, facet shape, and disc height. Degenerative lumbar spondylolisthesis was found in 284 (8.7%) of the patients, of which 83 were excluded. Single-level spondylolisthesis was present in 132 of the 201 patients studied, including 93 cases of anterolisthesis and 39 of retrolisthesis, the former being predominant at L4 and in women and the latter at L2 and equal between the genders. Multilevel spondylolisthesis in 69 patients included 65 (94%) of two-segment slip, 21 anterior, 25 posterior, and 19 combined, and 4 cases of three-segment retrolisthesis. Factors related to anterolisthesis were increased P-F angle and W-shaped facet joint; statistically, however, no factors were found statistically related to retrolisthesis. Multilevel anterolisthesis was considered to occur from factors similar to those previously reported for single-level anterolisthesis, and the pathomechanism of retrolisthesis is different from that of anterolisthesis.

Using a specialized orthopedic software package, the authors investigated the sagittal spinal shape and the position of the pelvis in the space in patients with isthmic spondylolisthesis and in persons with no such symptoms. Digitized lateral spinal radiographs of 30 healthy volunteers and 48 patients were evaluated. The absolute values and significant correlations between parameters were analyzed. The pelvic parameters correlated well with lordosis, which shows sagittal balance in the asymptomatic group. The hyperlordosis and the horizontally positioned sacrum in isthmic spondylolisthesis enlarge the tensile force component of gravity, which may cause the lysis. Finally, the authors developed a new balance between the pelvis and the spine after slipping of the vertebral body. The degree of slipping correlated well with the sacrofemoral anatomic constant (incidence), which is unique in each person.