Eun-Su Moon

Comparison of the Predictive Value of Myelography, Computed Tomography and MRI on the Treadmill Test in Lumbar Spinal Stenosis

To date, there have been no prospective, objective studies comparing the accuracy of the MRI, myelo-CT and myelography. The purpose of this study is to compare the diagnostic and predictive values of MRIs, myelo-CTs, and myelographies. Myelographies with dynamic motion views, myelo-CTs, MRIs and exercise treadmill tests were performed in 35 cases. The narrowest AP diameter of the dural sac was measured by myelography. At the pathologic level, dural cross-sectional area (D-CSA) was calculated in the MRI and Myelo-CT. The time to the first symptoms (TAF) and the total ambulation time (TAT) were measured during the exercise treadmill test and used as the standard in the comparison of correlation between radiographic parameters and walking capacity. The mean D-CSA by CT was 58.3 mm2 and 47.6 mm2 by MRI. All radiographic parameters such as AP diameters and D-CSA have no correlation to TAF or TAT (p>0.05). Our data showed no statistically significant differences in the correlation of the patients walking capacity to the severity of stenosis as assessed by myelography, myelo-CT and MRI.

Surgical outcome of lumbar fusion surgery in patients with Parkinson disease.

Study Design Retrospective study. Objectives To investigate the overall surgical outcome of lumbar fusion surgery in patients with Parkinson disease (PD). Summary of Back ground Data Poor bone quality and muscular dysfunction are important clinical manifestations connected with musculoskeletal diseases in PD patients. These secondary changes caused by PD often result in spinal pathology, indicating spine operations for some patients with scoliosis, kyphosis, osteoporotic fracture, or degenerative spondylosis. However, little is known about the surgical outcome or prognosis of spine surgery in PD patients. Methods Lumbar fusion surgery was performed on 20 patients who had PD and degenerative spinal diseases. At the time of lumbar fusion surgery, the mean duration of PD, age, sex, the preoperative visual analog pain scale (VAS, 0 to 100 mm) for low back pain, Hoehn and Yahr staging, and other comorbidities were evaluated. Patients postoperative clinical outcome was measured using the criteria of Kim and Kim and VAS for back pain. Radiographic assessment was made using plain films and a dynamogram. Results At the time of the spine surgery, Hoehn and Yahr staging of PD was from 1 to 2 in all patients. Only 1 patient had a satisfactory outcome; a good result according to Kim and Kims criteria. The average postoperative VAS (mm) was 55.2, whereas the mean preoperative VAS (mm) was 53.9. Radiological assessment showed fusion status in 15 patients and probably no solid fusion mass in 5 patients. Conclusions A poor surgical outcome would be inevitable because of the worsening of symptoms owing to the natural history of PD. Therefore, our current study suggested surgical indication should be exercised cautiously in the patients with PD and spinal stenosis.

Life expectancy after lumbar spine surgery: one- to eleven-year follow-up of 1015 patients.

Study Design. Retrospective study. Objectives. To investigate the 10-year survival of a large number of elderly patients who underwent spine surgery for lumbar spinal stenosis, and to identify significant risk factors and compare them with age- and gender-matched controls from the general population. Summary of Background Data. There have been many studies on treatment options and surgical outcomes for lumbar spinal stenosis. However, survival outcomes after lumbar spinal stenosis surgery have not previously been studied. Because these operations are usually performed for elderly patients, we consider patient survival or life expectancy to be a significant outcome measure. Methods. Between January 1997 and June 2006, patients underwent spine surgery for lumbar spinal stenosis. The date of death was verified using records from the National Health Insurance Corporation. Cumulative 10-year survival was calculated using the Kaplan-Meier method, and the survival of patients who had undergone spine surgery was compared to that of age- and sex-matched members of the general population. A Cox multivariate regression analysis was used in order to compare the survival rates for different covariates. Results. Using Kaplan-Meier curves, the overall 10-year survival was 87.8% in patients 60 to 70 years old at surgery, and 83.8% in patients 70 to 85 years old at surgery. The 10-year survival rate of female patients and patients who underwent fusion surgery were higher than those of male patients and patients with nonfusion surgery. Compared to the adjusted corresponding portion in general population, the standardized mortality ratios were 0.21, 0.53, and 0.45 in patients aged 50 to 59, 60 to 69, and 70 to 85, respectively. Conclusion. Elderly patients who underwent spine surgery for spinal stenosis had reduced mortality compared to the corresponding portion of the general population. Therefore, surgery for spinal stenosis is a justifiable procedure even in elderly patients.

The Biomechanical Effect of Pedicle Screws' Insertion Angle and Position on the Superior Adjacent Segment in 1 Segment Lumbar Fusion

Study Design. A finite element analysis. Objective. To investigate the association between the position of an inserted pedicle screw and the corresponding facet contact force or intradiscal pressure. Summary of Background Data. Although superior facet joint violation by pedicle screws is not an uncommon occurrence in instrumented lumbar fusion surgery, its actual biomechanical significance is not well understood. Furthermore, the association between the position of the pedicle screw and the stress on the corresponding disc/facet joint has yet to be investigated. Methods. According to the positions of pedicle screws in L4 of the L4–L5 lumbar fusion, 4 L4–L5 fusion models were simulated. These models included the violation of both L3–L4 superior facet joints by pedicle screws (facet joint violation [FV] model), the nonencroachment of both L3–L4 superior facet joints by pedicle screws (facet joint preservation [FP] model), and the removal state of pedicle screws in the FV model (removal of violated pedicle screws [rFV] model). The facet joint contact [FC] model represented the scenario in which the pedicle screws did not encroach upon either facet joint but were inserted close to the L3–L4 facet joint surface. Moreover, the uninstrumented fusion [UF] model represented the uninstrumented L4–L5 fusion. In each scenario, the intradiscal pressures and facet contact forces at the L2–L3 and L3–L4 segments were analyzed under extension and torsion moments. Results. The FV model yielded the greatest increases in facet contact force and intradiscal pressure at the L3–L4 segment under extension and torsion moments. Following the FV model, the increases in intradiscal pressure and facet contact force were the second highest in the FC model followed by the FP model. Furthermore, the rFV model represented prominent reductions of previously increased facet contact force and intradiscal pressure at the L3–L4 segment. Conclusion. In models of 1-segment lumbar fusion surgery, the positions of pedicle screws were closely linked with corresponding disc stresses and facet contact forces. However, even in cases of facet violation by pedicle screws, removal of the pedicle screw after fusion completion can reduce facet contract forces and disc stresses under both extension and torsional moments.

The risk assessment of a fall in patients with lumbar spinal stenosis

Study Design. A prospective case control study. Objectives. To investigate the risk of a fall by using functional mobility tests in patients with lumbar spinal stenosis (LSS) via a comparison with patients with knee osteoarthritis (KOA). Summary of Background Data. LSS is a degenerative arthritic disease in the spine that results in decreasing function, impaired balance, and gait deficit, with increased levels of leg and back pain. This physical impairment may result in an increased risk of fall later in the disease process, as shown in KOA. However, there has been no study regarding the association between the risk of a fall and LSS. Methods. The study was an age- and weight-matched case control study consisting of two groups: one group consisting of 40 patients with LSS who were scheduled to undergo spine surgery (LSS group) and the other group consisting of 40 patients with advanced osteoarthritis in both knees, scheduled to undergo TKA on both knees (KOA group). For both groups, four functional mobility tests, such as a Six-Meter-Walk Test (SMT), Sit-to-Stand test (STS), Alternative-Step Test (AST), and Timed Up and Go Test (TUGT), were performed. Results. There was no difference in demographic data between both groups except for body mass index. For the SMT and STS, the patients in the LSS group spent significantly more time performing these tests than the patients in the KOA. For the AST, however, patients in the KOA group presented a statistically worse performance in functional mobility, compared with the LSS group. The mean TUGT time was not statistically different between the two groups. Conclusions. The current study highlights that patients with symptomatic LSS have a risk of a fall comparable with the patients who had degenerative KOA based on the results of functional mobility tests (SMT, STS, AST, and TUGT).

A validated finite element analysis of nerve root stress in degenerative lumbar scoliosis

Few studies have shown the relationship between the curve pattern and nerve root symptoms in degenerative lumbar scoliosis, and its mechanism remains unclear. We developed a finite element model of two patterns of scoliotic curves (isolated lateral bending curve, lateral bending combined with rotation curve). The stress on the nerve root was calculated on both sides (right and left) of the apex vertebra. In the lateral bending curves without rotation, the compressive nerve root stress on the concave side was greater than the tensile stress on the convex side at the apex vertebra. In contrast, when the segmental rotation of the vertebrae was added to the lateral bending curve, there was significantly higher tensile stress on the convex side, and lower compressive stress on the concave side. To conclude, rotatory listhesis may be an important pathomechanism in the development of neurologic symptoms on the convex side of the curve.

Analysis of biomechanical changes after removal of instrumentation in lumbar arthrodesis by finite element analysis

The purpose of this study is to investigate the change in biomechanical milieu following removal of pedicle screws in instrumented single level lumbar arthrodesis. Using a validated finite element (FE) model of the intact lumbar spine (L2–5), two scenarios of L3–4 lumbar fusion were simulated: posterolateral fusion (PLF) at L3–4 using pedicle screws (PLF with pedicle screws; WiP) and L3–4 lumbar posterolateral fusion state after removal of pedicle screws (PLF without pedicle screws; WoP). The WiP model had greater range of motion (ROM) at each adjacent segment than the WoP model. This phenomenon became pronounced at the proximal adjacent segment under flexion moment. Similarly, removal of pedicle screws (the WoP model) relieved the maximal von Mises stress at adjacent segments under 4 moments compared to the WiP model. This study demonstrated that removal of pedicle screws could decrease stiffness of fusion segments, which would reduce the disk stress of adjacent segments.

Changes in vitamin D status after surgery in female patients with lumbar spinal stenosis and its clinical significance.

Study Design. A prospective cohort study. Objective. To demonstrate the changes in vitamin D status after surgery in female patients with lumbar spinal stenosis (LSS), and its correlation with surgical outcomes. Summary of Background Data. In patients with LSS, general health including walking ability and nutritional status can be markedly improved by decompressive surgery. It can be hypothesized that such improvement may have a positive effect on their vitamin D status. Methods. In total, 31 female patients who underwent decompression and instrumented posterolateral fusion for LSS were enrolled. Serum 25-hydroxyvitamin D (25-OHD) level was measured before the surgery and at 1 year postoperative visit. According to serum 25-OHD level, patients were classified into 3 groups: (1) deficient group, when 25-OHD level was less than 20 ng/mL (< 50 nmol/L); (2) insufficient group, when 25-OHD level was between 20 to 30 ng/mL (50 nmol/L ⩽ 25-OHD < 75 nmol/L); (3) and normal group, when 25-OHD level was 30 ng/mL or more (≥75 nmol/L). The Oswestry Disability Index (ODI) score and health-related quality of life (EQ-5D) were compared according to the level of 25-OHD at 1 year postoperatively. Results. Preoperatively, there were 20 patients in the deficient group, 11 patients in the insufficient group and no patient in the normal group. There were no differences in age, body mass index, preoperative ODI scores, preoperative EQ-5D index scores, and EQ-5D visual analogue scale scores between the 2 groups. Mean preoperative 25-OHD level was 15.8 ng/mL (range, 5.2–29.4 ng/mL) and increased to 19.5 ng/mL (range, 6.3–47.7 ng/mL) 1 year after surgery (P = 0.075). Significant increase of 25-OHD was noted only in the deficient group (P = 0.017). Postoperatively, there were 18 patients in the deficient group, 8 patients in the insufficient group, and 5 patients in the normal group. In the postoperative deficient group, postoperative ODI scores and EQ-5D index scores showed significantly worse outcomes than those in the other groups. The changes in serum 25-OHD level were significantly correlated with the changes in ODI scores (r = −0.580; P = 0.001) and with the changes in EQ-5D index scores (r = 0.379; P = 0.035). In all the groups, postoperative ODI scores (r = −0.665; P < 0.001) and EQ-5D index scores (r = 0.601; P < 0.001) were significantly correlated with postoperative 25-OHD level. Conclusion. Vitamin D deficiency was common in patients with LSS. However, vitamin D status was improved after decompressive surgery, and postoperative 25-OHD level was significantly correlated with surgical outcomes.

The Quantitative Assessment of Risk Factors to Overstress at Adjacent Segments After Lumbar Fusion: Removal of Posterior Ligaments and Pedicle Screws

Study Design. Finite element method. Objective. To investigate the changes in the disc stress and range of motion (ROM) at adjacent segments after lumbar fusion based on whether or not pedicle screws are removed and whether or not the continuity of the proximal posterior ligament complex (PLC) is preserved. Summary of Background Data. The ablation of proximal PLC continuity and the presence of pedicle screws have been reported to affect the biomechanics at adjacent segments after lumbar fusion. However, there have been few studies regarding the quantitative assessment of their contribution to overstress at adjacent segments after lumbar fusion. Methods. In the validated intact lumbar finite element model (L2–L5), four types of L3–L4 fusion models were simulated. These models included the preservation of the PLC continuity with pedicle screws (Pp WiP), the preservation of PLC continuity without pedicle screws (Pp WoP), the sacrifice of PLC with pedicle screws (Sp WiP), and the sacrifice of PLC without pedicle screws (Sp WoP). In each scenario, the ROM, maximal von Mises stress of discs, and the facet joint contract force at adjacent segments were analyzed. Results. Among the four models, the Sp WiP yielded the greatest increase in the ROM and the maximal von Mises stress of the disc at adjacent segments under four moments. Following the SP WiP, the order of increase of the ROM and the disc stress was Pp WiP, Sp WoP, and Pp WoP. Furthermore, the increase of ROM and disc stress at the proximal adjacent segment was more than at the distal adjacent segment under all four moments in each model. The facet joint contact was also most increased in the Sp WiP under extension and torsion moment. Conclusion. The current study suggests that the preservation of the PLC continuity or the removal of pedicle screws after complete fusion could decrease the stress at adjacent segments, and their combination could act synergistically.

Restoration of bone turnover rate after decompression surgery in patients with symptomatic lumbar spinal stenosis: preliminary report.

Study Design. Prospective short-term longitudinal study. Objective. To investigate changes in the bone turnover rate in patients with lumbar spinal stenosis (LSS) before and after decompression surgery. Summary of Back ground Data. Decompression surgery enables elderly patients with LSS to participate in daily activities and physical exercise by reducing or alleviating leg and back pain. However, there have been no studies to date regarding the effect of decompression surgery on bone metabolism in such patients. Methods. Twenty-three patients with spinal stenosis who were scheduled to undergo decompression surgery were enrolled in our study. Ten patients were given oral bisphosphonates after the operation (B+ group), while the remaining 13 patients did not receive oral bisphosphonate (B− group). In both groups, walking distance without rest, the Oswestry Disability Index (ODI) scores, duration of symptoms, bone formation, and resorption markers, and bone mineral density were recorded before surgery. Three months after surgery, bone turnover markers, a single trial for walking distance without rest and ODI scores were measured for both groups. Results. Three months after the operation, the bone resorption marker u-NTx was decreased significantly for both groups. Although there was a decrease in bALP, a bone formation maker, in both groups, the change in each group was not statistical significant. Distance in a single trial walk was increased and ODI scores were decreased significantly for both groups. Conclusion. This study suggests that decompression surgery has a beneficial effect on bone metabolism in patients with LSS who have walking intolerance and limited physical activity.