Radiostereometric analysis of postoperative motion after application of dynesys dynamic posterior stabilization system for treatment of degenerative 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.

Comparison of Cobb technique, quantitative motion analysis, and radiostereometric analysis in measurement of segmental range of motions after lumbar total disc arthroplasty.

STUDY DESIGN: Prospective clinical study. OBJECTIVE: To compare the amount of segmental motion in the sagittal plane after lumbar total disc arthroplasty (TDA) measured by using the Cobb technique, quantitative motion analysis (QMA), and radiostereometric analysis (RSA). SUMMARY OF BACKGROUND DATA: The aim of TDA is preservation of motion and therefore essential to properly quantify the motion. Clinically, segmental motion is measured by using the Cobb technique, which involves either the endplates or the implant as radiographic landmarks. This technique has been reported to have large intraobserver and interobserver variability. QMA and RSA are in vivo techniques that can measure the segmental motion with accuracy, but have not been compared with each other or compared with the Cobb technique in the literature. METHODS: Ten patients (6 males and 4 females, 47 + or - 7 y) with lumbar disc degeneration were surgically treated with ProDisc-L (Synthes Inc). Intraoperatively, tantalum beads were inserted into each vertebra and patients were followed postoperatively at 1 month, 1 year, and 2 years. At each follow-up time-point, biplanar flexion/extension radiographs were obtained and sagittal range of motion (ROM) of the index level was calculated by using the RSA technique. Clinical flexion/extension radiographs were also obtained and the sagittal ROM at the same level was calculated by using a modified Cobb technique. The clinical films were additionally analyzed by Medical Metrics for sagittal ROM using QMA. The results of the 3 measurement techniques were statistically analyzed and compared in pairwise fashion. RESULTS: A significant difference (P = 0.02) was observed between the Cobb technique (5.9 + or - 4.9) and RSA (3.5 + or - 2.4). A trend (P = 0.069) was also seen between QMA (5.7 + or - 4.7) and RSA. On paired-samples correlation, a significantly high correlation was seen between Cobb technique and QMA (r = 0.868, P < 0.001). A larger variability was seen when using the Cobb technique or QMA in comparison to the RSA. CONCLUSIONS: Sagittal ROM after TDA was similar between QMA and digital Cobb technique. A larger variability was seen between these techniques and RSA.

The Association of Sacral Table Angle Measurements With Spondylolytic and Spondylolisthetic Defects at the Lumbosacral Articulation: A Radiographic Analysis.

STUDY DESIGN: Retrospective radiographic study of 6 patients with L5 spondylolysis observed prospectively before the onset of lysis through adulthood. A radiographic analysis of 50 pediatric control subjects was compared with the study group. OBJECTIVE: To determine whether sacral table angle (STA) measurements bear etiologic association with the development of spondylolysis and/or subsequent spondylolisthesis. SUMMARY OF BACKGROUND DATA: Although radiographic parameters in association with spondylolysis and isthmic spondylolisthesis have been studied, no parameter has been shown to definitively have a role in development of this disease process. The STA is a recently described radiographic parameter useful in measuring anatomic changes across the lumbosacral articulation. This measurement's role as a predictor of pars lysis and subsequent slippage remains unknown. METHODS: The researchers examined the longitudinal plain radiographs of 6 patients observed from childhood, before the development of spondylolysis, through adulthood. Measurements of STA and percent slippage were performed. Fifty pediatric control subjects' radiographs were also examined with STA measurements. Statistical analysis was conducted on results. RESULTS: Mean STA of the study group before the development of spondylolysis was 95° ± 5.5°. Mean STA from the control group was 97.5° ± 4.3°. No statistical difference was found between groups (p > .05). No index patient had an abnormal STA before spondylolysis (less than 89°, defined as being outside 2 standard deviations from the control mean). Four of 6 index patients with spondylolysis developed spondylolisthesis. A negative correlation (r = .54) was seen for STA as a function of increasing percent slip when assessed longitudinally. CONCLUSIONS: Abnormal STA measurement was not seen before the development of spondylolysis in this study population. Decreasing STAs were seen secondarily in patients with L5 spondylolisthetic progression. This finding points to anatomic change and secondary remodeling of the upper sacrum as a result of slippage.

Abnormal brain chemistry in chronic back pain: an in vivo proton magnetic resonance spectroscopy study.

The neurobiology of chronic pain, including chronic back pain, is unknown. Structural imaging studies of the spine cannot explain all cases of chronic back pain. Functional brain imaging studies indicate that the brain activation patterns are different between chronic pain patients and normal subjects, and the thalamus, and prefrontal and cingulate cortices are involved in some types of chronic pain. Animal models of chronic pain suggest abnormal spinal cord chemistry. Does chronic pain cause brain chemistry changes? We examined brain chemistry changes in patients with chronic back pain using in vivo single- voxel proton magnetic resonance spectroscopy ((1)H-MRS). In vivo (1)H-MRS was used to measure relative concentrations of N-acetyl aspartate, creatine, choline, glutamate, glutamine, gamma-aminobutyric acid, inositol, glucose and lactate in relation to the concentration of creatine. These measurements were performed in six brain regions of nine chronic low back pain patients and 11 normal volunteers. All chronic back pain subjects underwent clinical evaluation and perceptual measures of pain and anxiety. We show that chronic back pain alters the human brain chemistry. Reductions of N-acetyl aspartate and glucose were demonstrated in the dorsolateral prefrontal cortex. Cingulate, sensorimotor, and other brain regions showed no chemical concentration differences. In chronic back pain, the interrelationship between chemicals within and across brain regions was abnormal, and there was a specific relationship between regional chemicals and perceptual measures of pain and anxiety. These findings provide direct evidence of abnormal brain chemistry in chronic back pain, which may be useful in diagnosis and future development of more effective pharmacological treatments.

Chronic pain patients are impaired on an emotional decision-making task.

Chronic pain can result in anxiety, depression and reduced quality of life. However, its effects on cognitive abilities have remained unclear although many studies attempted to psychologically profile chronic pain. We hypothesized that performance on an emotional decision-making task may be impaired in chronic pain since human brain imaging studies show that brain regions critical for this ability are also involved in chronic pain. Chronic back pain (CBP) patients, chronic complex regional pain syndrome (CRPS) patients, and normal volunteers (matched for age, sex, and education) were studied on the Iowa Gambling Task, a card game developed to study emotional decision-making. Outcomes on the gambling task were contrasted to performance on other cognitive tasks. The net number of choices made from advantageous decks after subtracting choices made from disadvantageous decks on average was 22.6 in normal subjects (n = 26), 13.4 in CBP patients (n = 26), and -9.5 in CRPS patients (n = 12), indicating poor performance in the patient groups as compared to the normal controls (P < 0.004). Only pain intensity assessed during the gambling task was correlated with task outcome and only in CBP patients (r = -0.75, P < 0.003). Other cognitive abilities, such as attention, short-term memory, and general intelligence tested normal in the chronic pain patients. Our evidence indicates that chronic pain is associated with a specific cognitive deficit, which may impact everyday behavior especially in risky, emotionally laden, situations.

Anterior cervical corpectomy and strut graft fusion using a different method.

BACKGROUND CONTEXT: Strut graft fusion after corpectomy is frequently indicated for certain pathologies in the cervical spine. The "key-hole" technique and "dove-tail" technique are the popular methods used to insert the strut graft at present. Segmental collapse secondary to seating of the graft on cancellous bone and cord injury from placement or dislodgement the graft are our concerns. Our method was designed to solve these possible problems without affecting the arthrodesis. PURPOSE: To evaluate the results of this method that allows the graft to seat on both the hard end plate and cancellous bone of the upper and lower contacting vertebrae in a easy and safe way after varying levels of corpectomy in the cervical spine. STUDY DESIGN: A retrospective clinical and radiographic study conducted by an independent observer was performed on 23 patients treated with this different strut grafting method after cervical corpectomy, with at least 2 years of follow-up. PATIENT SAMPLE: A total of 23 patients from 1983 to 1994 underwent fusion using our strut grafting method with fibular allograft packed with autogenous bone. No augmented internal instrumentation was used in all these patients. The patients with an incomplete record or less than 2 years of follow-up were excluded beforehand. OUTCOME MEASURES: Clinical outcome was assessed by a score based on three factors: neck pain, dependence on medicine and ability to return to work. The total score of these factors was seven. A score from 0 to 3 was defined as satisfactory, and a score from 4 to 7 was defined as unsatisfactory. The result of graft fusion, collapse of interbody height and loss of lordotic angle corrected by the graft were evaluated through the radiographic studies. METHODS: The operative technique creates a notch in the anterior cortex and end plate of the respective superior and inferior vertebraes. Cylinder allograft filled with autogenous cancellous bone was used as bone graft for all patients. The bone graft is cut with corresponding pegs at both ends. The graft is inserted into the corpectomy space with the pegs inserted into the notches and the remainder of the graft placed onto the preserved superior and inferior bony end plates. RESULTS: Twenty patients achieved successful fusion (87%). On average, the loss of anterior and posterior interbody height was 2.79 mm and 2.93 mm, respectively. The average loss of lordotic correction was 2.83 degrees. Eighty-three percent achieved satisfactory clinical outcomes. There were no neurologic injuries encountered during the operation. Partial graft dislodgment occurred in two patients (8.7%). CONCLUSIONS: This different method of strut grafting after cervical corpectomy has proven its safety and efficacy in its fusion and clinical results.

An in vivo kinematic comparison of dynamic lumbar stabilization to lumbar discectomy and posterior lumbar fusion using radiostereometric analysis.

BACKGROUND: Biomechanical studies have shown that dynamic stabilization restores the neutral zone and stabilizes the motion segment. Unfortunately, there are limitations to clinical measurement of lumbar motion segments when using routine radiographs. Radiostereometric analysis is a 3-dimensional technique and can measure the spinal motion segment more accurately than techniques using plain film radiographs. The purpose of this study was measure and compare the range of motion after dynamic stabilization, posterior lumbar fusion (PLF), and lumbar discectomy. METHODS: Four patients who underwent lumbar decompression and dynamic stabilization (Dynesys; Zimmer Spine, Inc., Warsaw, Indiana) for treatment of lumbar spondylosis were compared with 4 patients with a similar diagnosis who were treated by PLF and pedicle screw fixation (PLF group) and 8 patients who had undergone lumbar microdiscectomy (discectomy group) for treatment of radiculopathy. During the surgical procedure, 3 to 5 tantalum beads were placed into each of the operative segments. The patients were followed up postoperatively at 1 month, 1 year, and 2 years. At each follow-up time point, segmental motions (flexion, extension, and total sagittal range of motion [SROM]) were measured by radiostereometric analysis. RESULTS: Flexion, extension, and SROM measured 1.0° ± 0.9°, 1.5° ± 1.3°, and 2.3° ± 1.2°, respectively, in the Dynesys group; 1.0° ± 0.6°, 1.1° ± 0.9°, and 1.5° ± 0.6°, respectively, in the PLF group; and 2.9° ± 2.4°, 2.3° ± 1.5°, and 4.7° ± 2.2°, respectively, in the discectomy group. No significant difference in motion was seen between the Dynesys and PLF groups or between the Dynesys and discectomy groups in extension. Significant differences in motions were seen between the PLF and discectomy groups and between the Dynesys and discectomy groups in flexion (P = .007) and SROM (P = .002). There was no significant change in the measured motions over time. CONCLUSIONS: In this study a significantly lower amount of motion was seen after dynamic stabilization and PLF when compared with discectomy. A future study with a larger cohort is necessary to examine what effect, if any, these motions have on clinical outcomes.

Correlation of radiostereometric measured cervical range of motion with clinical radiographic findings after anterior cervical discectomy and fusion.

STUDY DESIGN: Prospective clinical study. OBJECTIVE: To evaluate the correlation between clinical radiographic findings and sagittal range of motion (ROM) measured using radiostereometric analysis (RSA) after anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Evaluation of fusion after ACDF continues to be difficult. Radiographic films including flexion/extension views are routinely used for this purpose. Unfortunately, routine radiographs are insensitive in demonstrating pseudarthrosis. RSA is an accurate technique that can be used in evaluation of segmental motion in vivo and can potentially be used in evaluation of spinal fusion. METHODS: Sixteen patients who underwent multi-level ACDF were enrolled in this study. The procedure was performed in the routine fashion; cervical plates were utilized in each case. Intraoperatively, 3 to 5 tantalum beads were inserted into each vertebral body. At the 1-year follow-up period, sagittal ROM of the operated segments was measured with RSA. In addition, each segment was clinically evaluated for evidence of radiographic fusion by using a 3-point grading system (fused, uncertain, pseudarthrosis) and by measuring the interspinous widening on flexion/extension films. The correlation between the radiographic findings and RSA measured sagittal ROM was evaluated. RESULTS: Fourteen 2-level and two 3-level procedures representing 31 motion segments were analyzed. The average sagittal ROM of all segments as measured by RSA was 1.3 +/- 1.4 degrees . The sagittal ROM of the segments with less than 2 mm of interspinous widening on clinical flexion/extension radiographs was measured at 1.1 degrees +/- 1.0 degrees with RSA, whereas the sagittal ROM of the segments with greater than 2 mm of interspinous widening was measured at 3.4 degrees +/- 2.9 degrees ; a significant correlation was noted between the 2-point grading method and the sagittal ROM (Pearson coefficient, r = 0.504, P = 0.004). Using the 3-point grading system, there were 20 levels graded as fused (0.8 degrees +/- 0.9 degrees ), 6 levels were graded as uncertain (1.7 degrees +/- 1.0 degrees ), and 4 levels were graded as pseudarthrosis (3.5 degrees +/- 2.7 degrees ). The pseudarthrosis group showed significantly greater motion than the fusion group (P = 0.005); a significant correlation was noted between the 3-point grading method and the sagittal ROM (Pearson coefficient, r = 0.561, P = 0.001). CONCLUSION: In this study, we evaluated the utility of RSA in evaluating segmental motion after ACDF and demonstrated a significant difference between segments that demonstrated radiographic evidence of fusion when compared with segments that demonstrated evidence of pseudarthrosis. RSA appears to be a quantitative technique capable of assisting in the evaluation of fusion.

Emotional health predicts pain and function after fusion: a prospective multicenter study.

STUDY DESIGN: Prospective. OBJECTIVES: To assess whether patients with poorer emotional health before fusion surgery will have worse pain and function after surgery, and to identify patient variables that predict fusion outcomes. SUMMARY OF BACKGROUND DATA: A systematic review of fusion outcomes studies reported an average of 68% "satisfactory" outcomes. The persistence of pain and functional limitations leads to emotional and financial costs. Therefore, it is important to identify the factors that affect fusion outcome. Research has explored psychosocial factors (e.g., depression, anxiety) as being important outcome predictors. METHODS: Data from subjects enrolled in a multisite trial of 2 fusion systems were analyzed. Subjects completed measures of health-related quality of life (SF-36), pain (visual analog scale), and function (Oswestry Disability Index). A total of 160 subjects completed measures before fusion, 155 completed measures 12 months after fusion, and 115 completed measures 24 months after fusion. Subject variables (i.e., age, gender, smoking, workers' compensation, and second surgery status) and presurgical pain/function were regressed on pain/function outcomes after surgery. This model was compared to one that included presurgical Mental Component Scores (MCSs), which is a SF-36 derived measure of emotional health, to determine whether MCS data significantly improved the prediction of pain/function. RESULTS: Higher presurgical MCS (i.e., better emotional health) predicted less back and leg pain after surgery. Similarly, higher presurgical MCS predicted better physical function after surgery. Other important predictors of pain and function were presurgical pain and function, workers' compensation, and smoking status. The associations were modest (2% to 9% of independent variance accounted for), but significant. CONCLUSIONS: Presurgical emotional status is one significant predictor of pain and function outcomes up to 2 years after fusion. Other significant predictors included workers' compensation status, smoking status, and presurgical pain/function. Studies to identify and intervenewith patients with poorer emotional status will clarify whether presurgical mental health intervention can improve pain and function outcomes after surgery or whether these patients are not candidates for surgery.

The natural history of spondylolysis and spondylolisthesis: 45-year follow-up evaluation.

STUDY DESIGN: A prospective study of spondylolysis and spondylolisthesis was initiated in 1955 with a radiographic and clinical study of 500 first-grade children. OBJECTIVE: To determine the natural history of spondylolysis and spondylolisthesis. SUMMARY OF BACKGROUND DATA: Most studies on the natural history of spondylolysis and spondylolisthesis are based on patient populations presenting with pain. Critical to any natural history investigation is the study of a population of affected individuals, whether symptomatic or not, from onset of the condition through their lives. METHODS: By study of a population from the age of 6 years to adulthood, 30 individuals were identified to have pars lesions. Data collection at a 45-year follow-up assessment included magnetic resonance imaging, a back pain questionnaire, and the SF-36 Survey. RESULTS: No subject with a pars defect was lost to follow-up evaluation once a lesion was identified. Subjects with unilateral defects never experienced slippage over the course of the study. Progression of spondylolisthesis slowed with each decade. There was no association of slip progression and low back pain. There was no statistically significant difference between the study population SF-36 scores and those of the general population the same age. CONCLUSIONS: This report is the only prospective study to document the natural history of spondylolysis and spondylolisthesis from onset through more than 45 years of life in a population unselected for pain. Subjects with pars defects follow a clinical course similar to that of the general population. There appears to be a marked slowing of slip progression with each decade, and no subject has reached a 40% slip.