Flexion-extension Radiographs Research Articles

Defining Pseudoarthrosis in the Cervical Spine With Differing Motion Thresholds

Calculate the apparent pseudarthrosis rate for anteriorly plated cervical spine fusions using different threshold levels of intervertebral rotation. Determine whether the apparent pseudarthrosis rate depends on the amount of intervertebral rotation used to characterize a fusion as a pseudarthrosis. Intervertebral motion at a spine fusion site is an important outcome measure in most spine fusion research studies. Intervertebral motion measures are used to determine if a device can be sold for use in spine fusion surgery. There is no consensus on how much motion is too much motion at a spine fusion site, and the intervertebral motion threshold that is used to define a pseudarthrosis is arbitrary. There are only limited data on the dependence of the pseudarthrosis rate on the threshold used to define a pseudarthrosis. Intervertebral motion at the fusion site was measured from flexion extension radiographs taken 1 year after cervical spine fusion using anterior plates and allograft in 200 patients. The number of cases where intervertebral motion at the fusion site exceeded thresholds between 1 degrees and 4 degrees were calculated. RESULTS.: The apparent pseudarthrosis rate varied from 6% when the intervertebral motion threshold was 4 degrees to 44% when the intervertebral motion threshold was 1 degrees . The apparent pseudarthrosis rate was highly dependent on the threshold of motion used to define a pseudarthrosis.

Anterior instrumentation for cervical spine tuberculosis: An analysis of surgical experience with 61 cases

To evaluate the efficacy of anterior instrumentation in patients with subaxial and cervicodorsal spinal tuberculosis in reconstruction of the spine, providing pain relief, neurological recovery and prevention of deformity. The records of 61 consecutive patients, of surgically treated spinal tuberculosis affecting C3 to D2 region, in our neuro and spinal surgery unit over a five-year period were retrospectively reviewed. Patients with involvement of the C3-C6 vertebrae underwent excision of the involved vertebrae and intervertebral discs followed by reconstruction with titanium implants by anterior approach. A transclavicular approach was used for patients with involvement of the C7-D2 vertebrae. A five-drug antituberculous regimen was administered for a period of one year. The follow-up ranged from 24 to 84 months (mean 38 months). Clinical and radiological assessment using flexion and extension radiographs was performed at 24 months for all cases. The neck pain score based on a visual analog scale (1-10) changed from a pre-operative average of 7 to 2 at follow-up after 4 months. Fifty-two patients (85%) had complete relief of pain while 16 patients who had Grade III to IV muscle strength regained complete power. The asymmetric wasting in patients with involvement of the cervicodorsal region did not recover completely. Flexion-extension radiographs at 24 months did not show any evidence of instability or nonunion. Anterior reconstruction using titanium plates and locking screws for stabilization of the subaxial and cervicodorsal region tuberculosis is a useful adjunct in preventing kyphotic deformity. A satisfactory segmental stability and fusion is achieved by this technique.

Novel treatment of basilar invagination resulting from an untreated C-1 fracture associated with transverse ligament avulsion

The authors describe the case of a traumatic C-1 ring fracture and transverse ligament injury in an otherwise healthy adult woman; the lesion was essentially untreated for 3 months and resulted in basilar invagination. On presentation 3 months postinjury, the patient complained of severe increasing suboccipital pain and a grinding sensation in her upper neck. Axial computerized tomography (CT) scans revealed a C-1 ring fracture, basilar invagination with the dens abutting the clivus, and significant lateral splaying of the C-1 lateral masses. Flexion-extension radiography demonstrated abnormal motion at the atlantoaxial junction. A unique surgical technique was used to address simultaneously the C1-2 instability, the displaced C-1 fracture, and basilar invagination without having to perform occipital fixation. The authors believe that an understanding of the mechanism of the cranial settling in this case (further splaying of the C-1 lateral masses and downward migration of the occipital condyles) permitted full reduction of the deformity; this was accomplished by performing a horizontal reduction of the C-1 lateral masses, using direct C-1 lateral mass screws, a rod compressor, and a cross-link. Postoperative CT scanning confirmed the success of reduction. The results in this report highlight a rare but important complication of untreated C-1 fracture and ligament disruption, and the authors describe a novel treatment technique with which to restore vertical alignment and preserve occipital C-1 motion. A variation of this technique may also be used to treat Type II transverse ligament injuries associated with C-1 ring fractures as an alternative to halo immobilization.

Changes of Sagittal Alignment and Mobility of Lumbar Spine After Artificial Disc Replacement

Purpose: To evaluate clinical outcomes of patients treated with artificial disc replacement (ADR) and to assess the capacity of this artificial disc replacement for preserving sagittal alignment and motion in the lumbar spine. Materials and Methods: 24 patients (10 men and 14 women, with a mean age of 46.7 (range 37-65) years) who underwent ADR in one or two segments of lumbar spine and followed up more than 12 months (range, 12-23 months) were reviewed. The level of pain was evaluated using visual analog scale (VAS) for low back and gluteal pain and functional outcome was evaluated using Oswestry Disability Index (ODI). Sagittal alignment and mobility of the lumbar spine were assessed in standing radiographs and dynamic flexion-extension radiographs. Results: The ODI improved from a mean of 33 (25-47) preoperatively to a mean of 11 (0-24) at the final follow-up. The VAS for lower back pain improved from 74 (50-100) to 23 (0-70) and for gluteal pain, the level improved from 52 (0-100) to 14 (0-60). The mean lordosis of the surgical segments was 16.7 preoperatively, 20.3 postoperatively, and 25.9 at final follow-up (p preoperatively, 36.9 postoperatively, and 49.4 at final follow-up (p preoperatively and 16.2 at the final follow-up, and that of the whole lumbar spine was 46.9 preoperatively and 48.1 at the final follow-up. Conclusion: These clinical results showed significantly less pain (VAS) and disability (ODI) after the ADR in the short term. In addition, the physiologic sagittal alignment and range of motion could be restored with ADR. The data from more patients and a longer follow-up will be needed to determine if these results can be maintained over the long term.

Lumbar instability and clinical symptoms: which is the more critical factor for symptoms: sagittal translation or segment angulation?

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. 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 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. 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.

Long-term follow-up on disc renarrowing after anterior lumbar interbody fusion with autogenous tricortical iliac crest graft

To have a retrospective review of the patients undergoing anterior lumbar interbody fusion (ALIF) with clinical and radiological assessment, and observe changing of graft after procedure and assess correlation between graft collapse and recurrence of radiculopathy. Sixty-seven consecutive patients undergoing ALIF only at L(4 - 5) with autologous iliac crest graft for intervertebral disc prolapse were followed-up for an average of 14 (2.5 - 32) years. The effect of the fusion was examined by the existence of radiolucent lines and bony continuity on plain radiographs and tomographs, or mobility on flexion-extension radiographs. The disc height was also measured. Lower limb radiculopathy was assessed based on the symptom and examination. Paired samples t-test was used for statistical analysis. Sixty-four patients with successful fusion were analyzed (fusion rate: 96%). All measurements in this study were completed by the same author, and the measurement error of more than 2 mm was statistically significant. According to this, graft collapse occurred in 55 patients (86%) and 9 patients (14%) had no graft collapse. In these 55 cases, the original disc height was (12.1 +/- 2.9) mm, increased immediately after the surgery to (16.2 +/- 1.9) mm, however re-narrowed to (12.9 +/- 2.7) mm at the first observation of solid fusion (a mean of 9 months, ranging from 5 to 14 months), which was not significant different compared to the original. There was no significant change in disc height after solid fusion and the disc space at the final follow-up was (12.6 +/- 2.3) mm. There was no radiculopathy observed in 52 cases (95%) during the follow-up. Disc space re-narrowing was observed in most cases after single level ALIF of L(4 - 5), however it was rarely less than the initial and unlikely to result in recurrence of radiculopathy.

Intravertebral vacuum phenomenon in osteoporotic compression fracture: report of 67 cases with quantitative evaluation of intravertebral instability.

The objectives of this study were to: 1) describe the incidence and clinical features of intravertebral vacuum phenomenon (IVVP) in a relatively large number of cases; 2) quantitatively evaluate intravertebral instability and determine the factors affecting instability; and 3) evaluate the efficacy of percutaneous vertebroplasty in the treatment of this phenomenon. A retrospective review was conducted of the records of 67 patients with IVVP among 652 consecutive cases of osteoporotic compression fracture. Comparisons between the IVVP group and a control group, a stable group, and an unstable group were conducted. Percutaneous vertebroplasty was performed in all patients. There were 67 patients (10.3%) in whom there were 70 vacuum phenomena of the intravertebral space. Intravertebral vacuum phenomena occurred predominantly in the thoracolumbar junction (81%) and in patients with a longer duration of symptoms (10.6 +/- 9.8 months) compared with the control group. Of 59 vertebrae for which flexion-extension radiographs were available, 26 vertebrae were categorized as stable and 33 as unstable. Twenty-one vertebrae (64%) had undergone compression fracture in the unstable group compared with nine (35%) compression fractures in the stable group. There were 28 (85%) fractures of the wedged vertebrae in the unstable group compared with 16 (61%) fractures in wedged vertebrae in the stable group. Percutaneous vertebroplasty was performed with successful clinical outcome. Intravertebral vacuum phenomenon is more common than has been previously appreciated. The results of this study indicate that biomechanics, not ischemic or avascular theory, may play an important role in pathogenesis of this phenomenon. Percutaneous vertebroplasty was found to be a minimally invasive and effective procedure for the treatment of IVVP.

Biomechanical evaluation of total disc replacement arthroplasty: an in vitro human cadaveric model.

This in vitro biomechanical study was undertaken to quantify the multidirectional intervertebral kinematics following total disc replacement arthroplasty compared to conventional stabilization techniques. Using an in vitro human cadaveric model, the primary objective was to compare the multidirectional flexibility properties and map the center of intervertebral rotation of total disc arthroplasty versus conventional threaded fusion cages and cages augmented with transpedicular fixation for single-level spinal instrumentation. The utilization of motion-preserving implants versus instrumentation systems, which stabilize the operative segments, necessitates improved understanding of their comparative biomechanical properties. A total of eight human cadaveric lumbosacral spines (L2 to sacrum) were utilized in this investigation and biomechanically evaluated under the following L4-L5 reconstruction conditions: 1) intact spine; 2) SB Charitè disc prosthesis; 3) BAK cages; and 4) BAK cages + ISOLA pedicle screw/rod fixation (anteroposterior). The superior (L3-L4) and inferior (L5-S1) intervertebral levels remained uninstrumented to quantify adjacent level properties. Multidirectional flexibility included pure, unconstrained moments (+/-8 Nm) in axial rotation, flexion-extension, and lateral bending, with quantification of the operative and adjacent level range of motion and neutral zone, which were normalized to the intact spine condition. The SB Charitè prosthesis indicated an average percentage increase in axial rotation range of motion by 44% compared to the intact condition (P < 0.05), whereas the BAK and anteroposterior reconstructions decreased range of motion by 29% and 80%, respectively (P < 0.05). The SB Charitè was significantly different from BAK and combined anteroposterior reconstructions (P < 0.05). Flexion-extension indicated a minor increase in range of motion for the SB Charitè (3%) versus the intact disc (P > 0.05), whereas the BAK and anteroposterior stabilization groups resulted in significant decreases in range of motion (BAK = 57%, anteroposterior = 93%) (P < 0.05) when compared to the intact and SB Charitè conditions. Based on flexion-extension radiographs, the intervertebral centers of rotation were in the posterior one-third of the operative intervertebral disc only for the SB Charitè reconstruction and intact spine condition, with definitive evidence of physiologic intervertebral translation (intact 2.06 +/- 77 mm; SB III = 1.9 +/- 0.98 mm). Total disc arthroplasty serves as the next frontier in the surgical management of discogenic spinal pathology. The SB Charitè restored motion to the level of the intact segment in flexion-extension and lateral bending and increased motion in axial rotation. The anterior annular resection necessary for device implantation and unconstrained design of the prosthesis account for this change in rotation. The normal lumbar flexion-extension axis of rotation is an ellipse rather than a single point. Only disc replacement rather than pedicle instrumentation or BAK interbody instrumentation preserves the kinematic properties and normal mapping of segmental motion at the operative and adjacent intervertebral disc levels.

Titanium mesh cages for cervical spine stabilization after corpectomy: a clinical and radiological study.

Reconstruction after anterior cervical decompression has involved the use of tricortical iliac crest bone or fibular strut grafts, but has been associated with significant morbidity. In this study the authors evaluated the efficacy of titanium mesh cages (TMCs) for stability and fusion following anterior cervical corpectomy. Thirty-seven patients were prospectively evaluated during a 4-year period. The majority presented with spinal cord compression (97%) often due to cervical spondylosis (87%). The TMC was filled with iliac crest bone chips or Surgibone and stabilized by anterior cervical plates (ACPs). The changes in settling ratio, coronal and sagittal angles, and sagittal displacement were determined at 3, 6, and 12 months; immediate postoperative radiographs were used as baseline. Flexion-extension radiographs and computerized tomography (CT) scans (obtained at 1 year) were examined to assess stability, fusion, and bone growth within the TMC. Complications such as settling, telescoping, migration, and pseudarthrosis were not observed. Dynamic radiography revealed spinal stability in all patients. Cage-related complications occurred in 2.7% (TMC malplacement [one patient]), surgery-related complications in 10.8%, and graft-related complications in 21.6%. Evidence of bone growth into the TMC was documented in 16 (95%) of 17 patients on CT scans. The mean cage height-related settling rates were 4.46% at 3 months (31 patients [p = 0.066]), 3.89% at 6 months (28 patients [p = 0.028]), and 4.35% at 1 year (27 patients [p = 0.958]). The mean sagittal displacement changed by 3.9% (23 patients [p = 0.73]). The mean coronal and sagittal angles changed 2.89 degrees (30 patients [p = 0.498]) and 2.09 degrees (29 patients [p = 0.001]) at 1 year, respectively, or at last follow up from baseline. No significant differences in the radiological indices were seen when multilevel vertebrectomy cases were compared with single-level vertebrectomy (p = 0.221), smoking status, or age. Conclusions. Titanium mesh cages, in combination with ACPs, are safe and effective for vertebral replacement in the cervical spine.

Vertical instability in spondylolisthesis: a traction radiographic assessment technique and the principle of management.

Lateral radiographs of the lumbar spine were taken of 40 patients with lumbar spondylolisthesis. These radiographs were taken in the neutral, flexion, and extension positions for both erect and recumbent postures, and also in the prone and supine positions with traction applied via a traction table. To define and demonstrate the presence of "vertical instability" in spondylolisthesis, and to determine the most useful radiographic views for clinical purposes and analysis of the surgical principle. Lateral radiographs of patients in flexion and extension are widely used to obtain quantitative and qualitative data on lumbar spondylolisthesis. Changes in lumbar disc height and segmental translation in a group of patients with spondylolisthesis have been demonstrated with the addition of traction and compression. Lateral and flexion extension radiographs of the lumbosacral spine in 37 patients with spondylolisthesis taken in standing and recumbent positions and under pelvic traction in the prone or supine positions were suitable for analysis. The changes in disc area, intervertebral kyphotic slip angle, and amount of anteroposterior shift (olisthesis) were measured from the radiographs using a computer digitizer. The disc area was normalized against the area of the superior vertebra, and the amount of anteroposterior shift was normalized against the anteroposterior width of the superior vertebra. Inter- and intraobserver error was found to be negligible, and results were analyzed by paired t test. Maximum slip angle, maximum olisthesis, and minimum normalized disc area were found with the subject under erect flexion. Conversely, prone traction and recumbent extension produced minimum slip angle, whereas the lowest anteroposterior shifts were seen with the subject under prone and supine traction. Prone traction also resulted in a significantly larger normalized disc area than any other posture. The change in kyphotic slip angle between erect flexion and prone traction is correlated with the change in normalized olisthesis and disc area. Erect flexion and prone traction radiographs represent the extremes of subluxation and reduction of the olisthesis, respectively, and the change in olisthesis seen between these extremes is correlated with the change in disc area and the intervertebral slip angle. Vertical laxity of the affected functional spinal unit resulting from disc degeneration produces laxity in the ligaments and disc anulus, allowing olisthetic motion. Restoration of disc height in turn restores tension to the soft tissues around the disc and results in a spontaneous reduction of the subluxation. Restoration and maintenance of disc height with a spacer or interbody fusion therefore is recommended as a goal in the treatment of spondylolisthesis. When spondylolytic spondylolisthesis involves a posterior column deficiency, additional reconstruction of this column with posterior instrumentation is recommended. Application of the traction radiographic technique in planning for spondylolisthesis reduction is discussed along with the technique of stabilization.

Vertical Instability in Spondylolisthesis

Study Design. Lateral radiographs of the lumbar spine were taken of 40 patients with lumbar spondylolisthesis. These radiographs were taken in the neutral, flexion, and extension positions for both erect and recumbent postures, and also in the prone and supine positions with traction applied via a traction table. Objectives. To define and demonstrate the presence of “vertical instability” in spondylolisthesis, and to determine the most useful radiographic views for clinical purposes and analysis of the surgical principle. Summary of Background Data. Lateral radiographs of patients in flexion and extension are widely used to obtain quantitative and qualitative data on lumbar spondylolisthesis. Changes in lumbar disc height and segmental translation in a group of patients with spondylolisthesis have been demonstrated with the addition of traction and compression. Methods. Lateral and flexion extension radiographs of the lumbosacral spine in 37 patients with spondylolisthesis taken in standing and recumbent positions and under pelvic traction in the prone or supine positions were suitable for analysis. The changes in disc area, intervertebral kyphotic slip angle, and amount of anteroposterior shift (olisthesis) were measured from the radiographs using a computer digitizer. The disc area was normalized against the area of the superior vertebra, and the amount of anteroposterior shift was normalized against the anteroposterior width of the superior vertebra. Inter- and intraobserver error was found to be negligible, and results were analyzed by paired t test. Results. Maximum slip angle, maximum olisthesis, and minimum normalized disc area were found with the subject under erect flexion. Conversely, prone traction and recumbent extension produced minimum slip angle, whereas the lowest anteroposterior shifts were seen with the subject under prone and supine traction. Prone traction also resulted in a significantly larger normalized disc area than any other posture. The change in kyphotic slip angle between erect flexion and prone traction is correlated with the change in normalized olisthesis and disc area. Conclusions. Erect flexion and prone traction radiographs represent the extremes of subluxation and reduction of the olisthesis, respectively, and the change in olisthesis seen between these extremes is correlated with the change in disc area and the intervertebral slip angle. Vertical laxity of the affected functional spinal unit resulting from disc degeneration produces laxity in the ligaments and disc anulus, allowing olisthetic motion. Restoration of disc height in turn restores tension to the soft tissues around the disc and results in a spontaneous reduction of the subluxation. Restoration and maintenance of disc height with a spacer or interbody fusion therefore is recommended as a goal in the treatment of spondylolisthesis. When spondylolytic spondylolisthesis involves a posterior column deficiency, additional reconstruction of this column with posterior instrumentation is recommended. Application of the traction radiographic technique in planning for spondylolisthesis reduction is discussed along with the technique of stabilization.

Treatment of multilevel cervical spondylotic myeloradiculopathy with posterior decompression and fusion with lateral mass plate fixation and local bone graft.

This is a retrospective review of 32 patients with multilevel cervical myelopathy treated by laminectomy and lateral mass plate fusion. The prognosis of surgically treated myelopathy is evaluated as well as prognostic factors for recovery of myelopathy. Diagnoses included cervical spondylosis or ossification of the posterior longitudinal ligament. Final follow-up was at 15.2 months (mean) postoperatively. Myelopathy was graded preoperatively and postoperatively by the system of Nurick. All patients had preoperative radiographs and magnetic resonance imaging (MRI). The presence of abnormal T2-weighted MRI signal (myelomalacia) was noted. Postoperative studies included flexion-extension radiographs to assess fusion and MRI to evaluate decompression of neural elements and resolution of myelomalacia. Severity of preoperative Nurick myelopathy, presence of myelomalacia, and age were evaluated as potential prognostic indicators for surgically treated myelopathy. Mean Nurick score improved from 2.6 (range 1-4) to 1.8 (range 0-3) postoperatively (p < 0.0001). Twenty-two patients (71%) had improvement in Nurick grade of at least one point, and nine showed no improvement. No patients had deterioration of Nurick grade. Preoperative myelomalacia was noted in 15 (47%) patients, and all 15 had residual myelomalacia postoperatively. Severe myelopathy, age, and myelomalacia had no prognostic value for improvement of myelopathy. Complications included pseudarthrosis (3%), wound infection (9%), and transient C5 palsy (6%). This study demonstrates excellent outcomes from laminectomy and fusion in multilevel cervical myelopathy. A high rate of improvement of myelopathy was observed, neurologic deterioration did not occur, and complication rates were low. Severe myelopathy and myelomalacia on preoperative MRI had no prognostic value.

Implantation of an empty carbon fiber composite frame cage after single-level anterior cervical discectomy in the treatment of cervical disc herniation: preliminary results.

The authors sought to evaluate retrospectively the radiological and clinical outcome of anterior cervical discectomy followed by implantation of an empty carbon fiber composite frame cage (CFCF) in the treatment of patients with cervical disc herniation and monoradiculopathy. Twenty-five consecutive patients (12 men, 13 women, mean age 45 years) with monoradiculopathy due to cervical disc herniation were treated by anterior cervical discectomy followed by implantation of an empty CFCF cage. On lateral flexion-extension radiographs segmental stability at a mean follow up of 14 months (range 5-31 months) was demonstrated in all 25 patients, and bone fusion was documented in 24 of 25 patients. The mean anterior intervertebral body height was 3.4 mm preoperatively and 3.8 mm at follow up in 20 patients. In these patients the mean segmental angle (angle between lower endplate of lower and upper vertebra) was 0.9 degrees preoperatively and 3.1 degrees at follow up. In the remaining five patients preoperative images were not retrievable. Self-scored neck pain based on a visual analog scale (1, minimum; 10, maximum) changed from a preoperative average of 5.6 to an average of 2 at follow up; radicular pain was reduced from 7.7 to 2.1 postoperatively. Analysis of the SF12 questionnaires showed a significant improvement in both the physical capacity score (preoperative mean 32.4 points; follow up 46 points) and the mental capacity score (preoperative mean 45.8 points; follow up 57.5 points). Implantation of an empty CFCF cage in the treatment of cervical disc herniation and monoradiculopathy avoids donor site morbidity associated with autologous bone grafting as well as the use of any supplementary material inside the cage. Restoration or maintenance of intervertebral height and thus segmental lordosis and a very high rate of segmental stability and fusion are achieved using this technique.

Degenerative lumbar spondylolisthesis-induced radicular compression: nonfusion-related decompression in selected patients without hypermobility on flexion-extension radiographs.

The authors conducted a study to determine the results of decompressive surgery without fusion in selected patients who presented with radicular compression syndromes caused by degenerative lumbar spondylolisthesis and in whom there was no evidence of hypermobility on flexion-extension radiographs. The medical records and radiographs obtained in 49 patients were reviewed retrospectively. Clinical status was quantified by summing self-assessed Prolo Scale scores. All 49 patients (55% female, mean age 68.7 years) presented with leg pain accompanied by lumbalgia in 85.7% of the cases. Preoperatively the median sum of Prolo Scale scores was 4. The mean preoperative degree of forward vertebral displacement was 13.5% and was located at L-4 in 67% of the cases. Osseous decompression alone was performed in 53%, and an additional discectomy at the level of displacement was undertaken in the remaining patients because of herniated discs. Major complications (deep wound infection) occurred in 2%. During a mean follow-up period of 3.73 years, 10.2% of the patients underwent instrumentation-assisted lumbar fusion when decompression alone failed to resolve symptoms. At last follow up the median overall Prolo Scale score was 8. Excellent and good results were demonstrated in 73.5% of the patients. Prolonged back pain (r = 0.381) as well as the preoperative degree of displacement (r = 0.81) and disc space height (r = 0.424) influenced outcome (p < or = 0.05); additional discectomy for simultaneous disc herniation at the displaced level did not influence outcome (p > 0.05). These results appear to support a less invasive approach in this subgroup of elderly patients with degenerative lumbar spondylolisthesis-induced radicular compression syndromes and without radiographically documented hypermobility. Additional discectomy for simultaneous disc herniation of the spondylolisthetic level did not adversely influence the outcome. Complication rates are minimized and fusion can eventually be performed should decompression alone fail. A prospective controlled study is required to confirm these results.

9:43 Spinal fusion and smoking: is pseudarthrosis the cause for poorer clinical outcome?

Purpose of study: Nicotine consumption by spinal fusion patients is associated with increased pseudarthrosis risk and poorer clinical outcome. This study examines the relationship between smoking and clinical outcome independent of fusion success.Methods used: Patients with symptomatic lumbar disc disease were enrolled in prospective studies to examine the efficacy of recombinant human bone morphogenic protein (rhBMP)-2 on an absorbable collagen sponge (InFuse; Medtronic, Minneapolis, MN) as a bone graft substitute for anterior lumbar interbody fusion (ALIF). All patients underwent single level ALIF with an LT-cage (Medtronic) containing either iliac crest autograft (control) or InFuse. Clinical outcome data were collected preoperatively, and at 1.5, 3, 6, 12 and 24 months after surgery. This included the Oswestry Disability Questionnaire Short Form (SF)-36 back profile and back pain questionnaires. Radiographic outcomes were assessed at 6, 12 and 24 months after surgery. Successful fusion required evidence of bridging trabecular bone on computed tomography scans and radiographs, and the presence of less than 50 of angular motion and less than 3 mm translation on flexion-extension radiographs, and no radiolucent lines covering more than 50% of the implant surface. Patients who had consumed nicotine by smoking within 6 months of surgery were identified as smokers. In order to exclude the effect of pseudarthrosis, we compared the outcome data between smokers and nonsmokers in the subgroup of patients who had achieved successful fusion.of findings: At 24 months after surgery, a total of 303 patients had achieved successful fusion: 211 nonsmokers (93.3% fusion rate) and 92 smokers (88.3% fusion rate). The following graphs depict the clinical outcome in these patients (Figs. 1, 2, 3, and 4) .Relationship between findings and existing knowledge: There is a significant relationship between smoking and clinical outcome independent of fusion success for ALIF procedure.Overall significance of findings: Independent of fusion outcome, there were differences in clinical outcome between smokers and nonsmokers. Nonsmoking patients with successful fusion had superior Oswestry scores (significant 6 and 12 months postoperative), superior SF-36 physical scores (significant 12 and 24 months postoperative), superior SF-36 mental scores (significant 6 and 12 months postoperative) and less back pain (significant 6 months postoperative) compared with smoking patients with successful fusion. The adverse effects of nicotine on osteogenesis and spinal fusion may not fully explain the poorer clinical outcome in patients who smoke.Disclosures: Device or drug: rhBMP-2 / absorbable collagen, investigational device. Status: investigational.Conflict of interest: Harvinder Sandhu, grant research support; Harvinder Sandhu, consultant for Medtronic Sofamor Danek.

Biomechanical evaluation of total disc arthroplasty: an in-vitro human cadaveric model

Purpose of study: This in-vitro biomechanical study was undertaken to compare the multidirectional flexibility properties and map the instantaneous axis of rotation (IAR) of total disc arthroplasty versus conventional threaded fusion cages and cages augmented with transpedicular fixation for single-level spinal reconstruction.Methods used: A total of eight human cadaveric lumbosacral spines (L3 to sacrum) were used in this investigation and biomechanically evaluated under the following L4–L5 reconstruction conditions: 1) intact spine; 2) SB Charitè Disc Prosthesis; 3) BAK cages; 4) BAK cages + ISOLA pedicle screw/rod fixation (anteroposterior). The superior (L3–L4) and inferior (L5–S1) intervertebral levels remained unconstrained to quantify adjacent level properties. Multidirectional flexibility testing included pure, unconstrained moments (±8 Nm) in axial rotation, flexion-extension and lateral bending, with quantification of the operative and adjacent level range of motion (ROM) and neutral zone (NZ), which were normalized to the intact condition. Stepwise flexion-extension radiographs were digitized and used to calculate the intervertebral IAR for the operative and adjacent levels.of findings: The SB Charitè prosthesis indicated an average percentage increase in axial rotation ROM by 44% compared with the intact condition (p<.05), whereas the BAK and anteroposterior reconstructions decreased ROM by 29% and 80%, respectively (p<.05). The SB Charitè was significantly different from BAK and combined anteroposterior reconstructions (p<.05). Flexion-extension indicated a minor increase in ROM for the SB Charitè (3%) versus the intact disc (p>.05), whereas the BAK and anteroposterior stabilization groups resulted in significant decreases in ROM (BAK=57%, anteroposterior=93%) (p<.01) when compared with the intact and SB Charitè conditions. Based on flexion-extension radiographs, the intervertebral centers of rotation were in the posterior 33% of the operative intervertebral disc only for the SB Charitè reconstruction, with definitive evidence of physiologic intervertebral translation (6 mm).Relationship between findings and existing knowledge: The SB Charitè restored motion to the level of the intact segment in flexion-extension and lateral bending and increased motion in axial rotation. The anterior annular resection necessary for device implantation and unconstrained design of the prosthesis account for this change in rotation. The normal flexion-extension axis of rotation of a motion segment is an ellipse rather than a single point. Only disk replacement rather than pedicle instrumentation or BAK interbody instrumentation preserves the normal mapping of segmental motion at the operative level and the adjacent vertebral spinal levels.Overall significance of findings: Total disk replacement is currently the only method of restoring mobility to the degenerative lumbar disc. This serves as the first comprehensive biomechanical study comparing the operative level multidirectional flexibility characteristics between total disc arthroplasty, interbody arthrodesis cages and pedicle screw spinal instrumentation.Disclosures: Device or drug: SB Charitè Prosthesis. Status: Investigational. Device or drug: BAK/L cages. Status: Approved. Device or drug: Isola Pedicle screws and rods. Status: approved.Conflict of interest: Ryan W. Cunningham, grant research support: Waldemar Link Inc.

Anterior lumbar interbody fusion with LT-cages: the influence of workers compensation status on chronological clinical outcome

Purpose of study: Workers compensation status is a predictor of clinical outcome in patients undergoing spinal fusion. The intent of this study was to examine the influence of workers compensation status on the chronological outcome of patients undergoing anterior lumbar interbody fusion (ALIF) with intervertebral fusion cages.Methods used: Patients with symptomatic lumbar disc disease were enrolled in prospective studies to examine the efficacy of recombinant human bone morphogenic protein (rhBMP)-2 on an absorbable collagen sponge (InFuse; Medtronic) as a bone graft substitute for ALIF. All patients underwent single-level ALIF with an LT cage (Medtronic) containing either iliac crest autograft (control) or InFuse. Clinical outcome data were collected preoperatively, and at 1.5, 3, 6, 12 and 24 months after surgery. This included the Oswestry Disability Questionnaire, Short Form (SF)-36 back profile and back pain questionnaires. Radiographic outcomes were assessed at 6, 12 and 24 months after surgery. Successful fusion required evidence of bridging trabecular bone on computed tomography scans and radiographs, and the presence of less than 50 of angular motion and less than 3 mm translation on flexion-extension radiographs, and no radiolucent lines covering more than 50% of the implant surface. Workers compensation status was determined in all patients preoperatively.of findings: Of a total of 413 patients enrolled, 136 patients (33%) were receiving workers compensation at the time of surgery and 277 patients (77%) were not. Of these, 109 workers compensation and 215 noncompensation patients were seen at the 24-month follow-up point. Figs. 1 to 5 depict the clinical outcome at each of the follow-up periods (Figs. 1, 2, 3, 4, and 5).Relationship between findings and existing knowledge: We demonstrate a significant influence of workers compensation status on the chronological outcome of patients undergoing ALIF with intervertebral fusion cages.Overall significance of findings: There were no differences in the fusion rates between compensation and noncompensation patients at each of the evaluation periods. Oswestry, SF-36 physical component, SF-36 mental component and back pain scores were significantly better in the noncompensation patients at each follow-up period. Noncompensation patients continued to experience improvement in their Oswestry, SF-36 physical component and back pain scores between the 12-month and 24-month follow-up periods, whereas compensation patients reached maximum improvement at the 12-month follow-up period.Disclosures: Device or drug: rhBMP-2/absorbable collagen sponge, investigational device. Status: investigational.Conflict of interest: Harvinder Sandhu, grant research support, and, consultant.

Saturday, November 2, 2001 4:13–4:56 pm Concurrent Session 8A: Artificial Disc: 4:13 Long-term flexion-extension range of motion of the Prodisc I disc prosthesis

Purpose of study: The theoretical rationale for the disc replacement prosthesis as an alternative to arthrodesis is the avoidance of junctional degeneration by preservation of motion at the instrumented segment. The purpose of this study is to quantify radiographically the in vivo flexion-extension range of motion (ROM) of the Prodisc I disc prosthesis at long-term follow-up. In addition, the relationship between ROM of the prosthetic discs and junctional disc degeneration at the level above disc prostheses is examined.Methods used: This study is a retrospective review of active flexion-extension radiographs of 34 patients who had placement of 50 Prodisc I disc prostheses at an average follow-up of 8.6 years (7 to 10). All patients underwent disc replacement surgery for the treatment of chronic mechanical back pain secondary to degenerative disc disease. Flexion-extension ROM was measured by Cobb's method at every instrumented level, as well as at the cephalad junctional level. Junctional levels were examined for radiographic signs of disc degeneration, such as loss of disc space height or marginal osteophyte formation. Two-tailed unpaired Student's t testing was performed to examine the relationship between junctional degeneration and the ROM of disc prostheses below junctional levels.of findings: We found that ROM in the Prodisc I prosthesis is preserved in flexion and extension at long-term follow-up, although ROM is less than that reported in asymptomatic individuals. Mean flexion-extension ROM for disc prostheses was 3.5 degrees at L2–L3, 4.0 degrees at L3–L4, 4.5 degrees at L4–L5 and 3.2 degrees at L5–S1. Of the 34 junctional levels evaluated, 9 showed signs of disc degeneration. However, none of these required further surgery at last follow-up. The mean flexion-extension ROM of a prosthesis below a degenerated junctional disc was 1.4 degrees compared with 5.0 degrees for prostheses below a junctional disc without radiographic signs of degeneration (p=.015).Relationship between findings and existing knowledge: No previous studies have documented the in vivo ROM of the Prodisc I prosthesis at long-term follow-up. Furthermore, no studies have examined the relationship between the development of junctional degeneration and disc prosthesis ROM. It is not clear how much motion must be maintained to avoid junctional degeneration. Previous authors have found that flexion-extension ROM in asymptomatic individuals is so variable that norms of motion cannot be precisely defined [1].Overall significance of findings: The documentation of in vivo motion of disc prostheses at long-term follow-up is essential to justify their use. Without preservation of some motion, a disc prosthesis amounts to an expensive arthrodesis equivalent. It is evident from our study that there is a relationship between ROM of a disc prosthesis and the development of junctional disc degeneration. We believe that these data support the use of a disc prosthesis instead of arthrodesis in selected patients.Disclosures: Device or drug: Prodisc. Status: investigational.Conflict of interest: Federico Girardi, consultant; Federico Girardi, stockholder; Frank Cammisa, Jr., consultant; Frank Cammisa, Jr., stockholder; Thierry Marnay, consultant and stockholder: Spine Solutions Inc.

Bilateral decompressive surgery in lumbar spinal stenosis associated with spondylolisthesis: unilateral approach and use of a microscope and tubular retractor system

The objective of this study was to assess the feasibility and efficacy of treating spondylolisthesis-related spinal stenosis via unilateral approach bilateral decompression in which METRx-MD instrumentation is placed. Eight consecutive patients with spinal stenosis underwent bilateral decompressions via a unilateral approach in which METRx-MD instrumentation was placed. The procedures were performed on an outpatient basis after induction of general anesthesia. The patients underwent preoperative and 3-month postoperative plain radiography in which flexion-extension x-ray films were obtained. Preoperative and postoperative magnetic resonance imaging was also performed. All radiographs and neuroimages were read by a single radiologist blinded to the clinical results. Eight vertebral levels in the eight patients were surgically decompressed (in one patient an additional level of nonspondylolisthesis-related stenosis was decompressed). The mean operative time was 92 minutes and the mean blood loss was 33 ml/level. Preoperatively stenosis was severe in five patients, moderate/severe in two, and moderate in one; postoperatively stenosis was absent in five, mild in two, and mild/moderate in one. Motion was detected on flexion-extension radiographs in three patients, but on early (3-month) postoperative radiographs there was no evidence of progression. By following the authors' procedure, minimally invasive bilateral decompression of acquired spinal stenosis associated with spondylolisthesis can be successfully performed on an outpatient basis, with reasonable operative times, minimal blood loss, and acceptable morbidity.

Segmental Lumbar Spine Instability at Flexion–Extension Radiography can be Predicted by Conventional Radiography

AIM: To identify plain radiographic findings that predict segmental lumbar spine instability as shown by functional flexion–extension radiography. MATERIALS AND METHODS: Plain radiographs and flexion–extension radiographs of 215 patients with clinically suspected lumbar spine instability were analysed. Instability was classified into anterior or posterior sliding instability. The registered plain radiographic findings were traction spur, spondylarthrosis, arthrosis of facet joints, disc degeneration, retrolisthesis, degenerative spondylolisthesis, spondylolytic spondylolisthesis and vacuum phenomena. Factors reaching statistical significance in univariate analyses (P<0.05) were included in stepwise multiple logistic regression analysis. RESULTS: Degenerative spondylolisthesis (P=0.004 at L3–4 level andP=0.017 at L4–5 level in univariate analysis and odds ratio 16.92 at L4–5 level in multiple logistic regression analyses) and spondylolytic spondylolisthesis (P=0.003 at L5–S1 level in univariate analyses) were the strongest independent determinants of anterior sliding instability. Retrolisthesis (odds ratio 10.97), traction spur (odds ratio 4.45) and spondylarthrosis (odds ratio 3.20) at L3–4 level were statistically significant determinants of posterior sliding instability in multivariate analysis. CONCLUSION: Sliding instability is strongly associated with various plain radiographic findings. In mechanical back pain, functional flexion–extension radiographs should be limited to situations when symptoms are not explained by findings of plain radiographs and/or when they are likely to alter therapy. Pitkänen, M. T. et al. (2002). Clinical Radiology57, 632–639.