The authors present the case of sciatica due to bicortical sacral screw impingement on the lumbosacral plexus across the anterior sacrum. The placement of sacral screw across the anterior sacral cortex carries significant inherent risks to neurovascular and visceral structures. However, the clinical reports of lumbosacral plexus involvement by the misplaced screw are not well documented in the literature. This is an unique case of sciatica due to sacral screw impingement on the lumbosacral plexus after motor vehicle accident(MVA), and confirmed by CT scan and intraoperative electrical stimulation. We reviewed sacral anatomy and preventive measures for avoiding complication of this type are discussed.
Electric Stimulation ; Lumbosacral Plexus* ; Motor Vehicles ; Sacrum ; Sciatica* ; Tomography, X-Ray Computed

STUDY DESIGN: Cross-sectional. PURPOSE: To examine the relationship between magnetic resonance imaging (MRI) morphology stenosis grades and preoperative walking ability in patients with lumbar canal stenosis (LCS). OVERVIEW OF LITERATURE: No previous study has analyzed the correlation between MRI morphology stenosis grades and walking ability in patients with LCS. METHODS: This prospective study included 98 consecutive patients with LCS who were candidates for surgery. Using features identified in T2-weighted axial magnetic, stenosis type was determined at the maximal stenosis level, and only trefoil and triangle stenosis grade types were considered because of sufficient sample size. Intraobserver and interobserver reliability were assessed by calculating weighted kappa coefficients. Symptom severity was evaluated via the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ). Walking ability was assessed using the Self-Paced Walking Test (SPWT) and JOABPEQ subscales. Demographic characteristics, SPWT scores, and JOABPEQ scores were compared between patients with trefoil and triangle stenosis types. RESULTS: The mean patient age was 58.1 (standard deviation, 8.4) years. The kappa values of the MRI morphology stenosis grade types showed a perfect agreement between the stenosis grade types. The trefoil group (n=53) and triangle group (n=45) showed similar preoperative JOABPEQ subscale scores (e.g., low back pain, lumbar function, and mental health) and were not significantly different in age, BMI, duration of symptoms, or lumbar stenosis levels (all p>0.05); however, trefoil stenosis grade type was associated with a decreased walking ability according to the SPWT and JOABPEQ subscale scores. CONCLUSIONS: These findings suggest preoperative walking ability is more profoundly affected in patients with trefoil type stenosis than in those with triangle type stenosis.
Asian Continental Ancestry Group ; Back Pain ; Constriction, Pathologic* ; Humans ; Lotus* ; Low Back Pain ; Magnetic Resonance Imaging* ; Orthopedics ; Prospective Studies ; Sample Size ; Spinal Stenosis* ; Walking*

OBJECTIVE: The clinical uses of screws are increasing with broader applications in spinal disorders. When screws are inserted repeatedly to achieve optimal position, tips of screw pitch may become damaged during insertion even though there are significant differences in the moduli of elasticity between bone and titanium. The effect of repeated screw insertion on pullout resistance was investigated. METHODS: Three different titanium screws(cortical lateral mass screw, cancellous lateral mass screw and cervical vertebral body screw) were inserted into the synthetic cancellous material and then extracted axially at a rate of 2.4mm/min using Instron(Model TT-D, Canton, MA). Each set of screws was inserted and pulled out three times. There were six screws in each group. The insertional torque was measured with a torque wrench during insertion. Pullout strength was recorded with a digital oscilloscope. RESULTS: The mean pullout force measurements for the cortical lateral mass screws(185.66N+/-42.60, 167.10N+/-27.01 and 162.52 N+/-23.83 for first, second and third pullout respectively: p=0.03) and the cervical vertebral body screws(386.0N+/-24.1, 360.2N+/-17.5 and 330.9N+/-16.7: p=0.0024) showed consecutive decrease in pullout resistance after each pullout, whereas the cancellous lateral mass screws did not(194.00N+/-36.47, 219.24N+/-26.58 and 199.49N(36.63: p=0.24). The SEM after insertion and pullout three times showed a blunting in the tip of the screw pitch and a smearing of the screw surface. CONCLUSIONS: Repetitive screw insertion and pullout resulted in the decrease of pullout resistance in certain screws possibly caused by blunting the screw tip. This means screw tips suffer deformations during either repeated insertion or pullout. Thus, the screws that have been inserted should not be used for the final construct.
Elasticity ; Titanium ; Torque

STUDY DESIGN: Case-control study. PURPOSE: To design a new tool for classifying lumbar spinal canal stenosis (CLSCS). OVERVIEW OF LITERATURE: Grading of patients with lumbar spinal canal stenosis (LSCS) is controversial. METHODS: The Oswestry disability index (ODI) and the neurogenic claudication outcome score (NCOS) were recorded. Four parameters, which indicate the severity of LSCS disease, including Hufschmidt-grade, grading of magnetic resonance imaging, self-paced walking test, and stenosis ratio (SR) were employed. For the SR, quartile analysis was applied for classifying LSCS and the Hufschmidt-grade was modified into a 4-grade score. An initial score was assigned to each metric based on the severity of LSCS. Using the inverse-variance weighting method, the relative weights of these domains and their categories were determined. The score for all of the cases was obtained based on their weight by summing up the points of the four variables. Quartile analysis was used and a CLSCS score was proposed. Finally, intra- and interobserver reliability, and validity were assessed. RESULTS: A total of 357 patients were studied. The final CLSCS score for each case ranged from 4 to 16.5. Based on the quartile analysis, using the new criteria set, the CLSCS score was divided into four categories: CLSCS<7 (grade 0); 7< or =CLSCS<10 (grade 1); 10< or =CLSCS<13 (grade 2); and 13< or =CLSCS< or =16.5 (grade 3). The kappa values of for the CLSCS score indicated a perfect agreement. The CLSCS was correlated with the ODI and NCOS. All patients with grade 3 CLSCS were observed in the surgical group. CONCLUSIONS: The CLSCS score can be helpful for classifying LSCS patients and in the decision-making process.
Case-Control Studies ; Classification* ; Constriction, Pathologic* ; Humans ; Magnetic Resonance Imaging ; Spinal Canal* ; Walking ; Weights and Measures

Among the various sacral fixation techniques used to enhance the strength of fixation, S1 screw placement in the sacrum is the most common method. Ventrolateral S1 screw placement through the sacral ala has been used alone or in combination with a medially-directed screw in the S1 pedicle to enhance pull-out resistance. Although the anatomical safe zone was identified, there is a risk of neurovascular injury particularly when the enhancement of fixation strength requires bicortical purchase. The purpose of this cadaver study is to re-evaluate the previous anatomical safe zone when using an S1 screw laterally directed toward the sacral ala. After dissecting the lateral safe zone of sacral ala in 12 human cadavers, K-wires were intentionally inserted deep into this zone. Each "safe" angle to the center of the safe zone was measured and the degree of risk to neurovascular structures was recorded on the basis of the distance in millimeters from the tips of the penetrating K-wires. The results are as follows: the mean safe angle to the center of the anatomical safe zone was 33.5degrees+/-9.3(20-50). Between 20 and 50 degrees, the range of safe angle was too wide. The distance between the tip of the K-wire and the sacroiliac joint, lumbosacral trunk, obturator nerve was 4.8mm+/-1(4-7.5), 6.8mm+/-1(6-9.5) and 6.8mm+/-3.2(0-10) respectively, while the anterior height between sacral cortex and lumbosacral trunk, internal iliac vein was 0mm and 2.1mm+/-1.8(0-5) respectively. In 29% of cases, the iliolumbar artery, the first branch of the internal iliac artery, abnormally crossed the middle of the safe zone. The sacroiliac joint, lumbosacral trunk, internal iliac vein and iliolumbar artery were at risk from laterally-directed S1 screws. This study shows that bicortical placement of S1 screws into the sacral ala presents unnecessary risks to neurovascular structures. It is concluded that the previous anatomical safe zone for bicortical S1 screw placement into the sacral ala was not surgically safe, and when lumbosacral fixation surgery is planned, operative techniques other than bicortical screw placement should be considered.
Arteries ; Cadaver ; Humans ; Iliac Artery ; Iliac Vein ; Intention ; Obturator Nerve ; Sacroiliac Joint ; Sacrum