Central sensitization as a predictive factor for the surgical outcome in patients with lumbar spinal stenosis: a multicenter prospective study.

PURPOSE: The impact of central sensitization (CS) on neurological symptoms and surgical outcomes in patients with lumbar spinal stenosis (LSS) remains unknown. This study aimed to investigate the influence of preoperative CS on the surgical outcomes of patients with LSS. METHODS: A total of 197 consecutive patients with LSS (mean age 69.3) who underwent posterior decompression surgery with or without fusion were included in this study. The participants completed the CS inventory (CSI) scores and the following clinical outcome assessments (COAs) preoperatively and 12 months postoperatively: the Japanese Orthopaedic Association (JOA) score for back pain, JOA back pain evaluation questionnaire, and Oswestry Disability Index (ODI). The association between preoperative CSI scores and preoperative and postoperative COAs was analyzed, and postoperative changes were statistically evaluated. RESULTS: The preoperative CSI score significantly decreased at 12 months postoperatively and was significantly correlated with all COAs preoperatively and 12 months postoperatively. Higher preoperative CSI showed worse postoperative COAs and inferior postoperative improvement rates in the JOA score, VAS score for neurological symptoms, and ODI. Multiple regression analysis demonstrated that preoperative CSI was significantly associated with postoperative low back pain (LBP), mental health, quality of life (QOL), and neurological symptoms at 12 months postoperatively. CONCLUSIONS: Preoperative CS evaluated by CSI had a significantly worse impact on surgical outcomes, including neurological symptoms, disability, and QOL, especially related to LBP and psychological factors. CSI can be used clinically as a patient-reported measure for predicting postoperative outcomes in patients with LSS.

The Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ): A validation of the reliability of the Thai version.

BACKGROUND: The Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) was developed by the Japanese Orthopedic Association (JOA) for assessment of lower back pain and lumbar spinal disease. We aimed to translate the JOABPEQ into Thai and test its reliability and validity in the Thai context. METHODS: The original JOABPEQ was translated into Thai in accordance with international recommendations. Then 180 lumbar spinal disease patients (mean age 58.58 ± 11.97, 68.3% female) were asked to complete the Thai version of the JOABPEQ twice at 2-week intervals. Test-retest reliability was analyzed using the intra-class correlation coefficient (ICC). Internal consistencies were analyzed using Cronbach's alpha, while the construct validity was compared with the Thai version of the modified SF-36, and tested using the Spearman's rank correlation coefficient. RESULTS: The Thai JOABPEQ showed satisfactory test-retest reliability in all parameters (Intra-class Correlation Coefficient 0.761-0.862). The variables low back pain, walking ability, social life function, and mental health had satisfactory internal consistency (the respective Cronbach's α was 0.798, 0.721, 0.707, and 0.795). Only the lumbar function parameter showed moderate reliability (Cronbach's α = 0.654). All of the variables in the Thai JOABPEQ had a statistically positive correlation with the correspondent Thai SF-36 subscales (Spearman's rank correlation p value < 0.05). CONCLUSION: The Thai version of JOABPEQ had satisfactory internal consistency, test-retest reliability, and construct validity; it can be used as a reliable tool for assessing quality of life for lumbar spinal disease patients in Thailand.

Psychological effects of meditation at a Buddhist monastery in Myanmar.

BACKGROUND: Meditation is widely used as a therapeutic measure because it can effectively reduce stress, pain, and improve the mental health, but there are many unclear points about the psychological effects of meditation. AIMS: The purpose of this study is to verify the psychological effects of meditation. METHOD: The short version of Profile of Mood States (POMS-SF) and the Acceptance and Action Questionnaire-II (AAQ-II) were conducted to compare 97 Myanmar people practicing Vipassana contemplation training with 81 Myanmar nurses who did not have any experience with meditation. RESULTS: The results of our study revealed that meditation mitigated depressive mood, anger, hostility, and fatigue and increased vigor. The enhancement of psychological flexibility occurred only after practicing meditation for more than a year. CONCLUSIONS: It can be considered that meditation mitigates anger, hostility and fatigue and increases vigor at a relatively early stage after starting meditation practice, and if meditation practice is continued for more than a year, enhancement of psychological flexibility can also be expected.

Validation of the reliability of the Thai version of the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ).

BACKGROUND: The Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) was developed to resolve problems associated with the original evaluation of cervical myelopathic patients. The aim of this study was to translate the JOACMEQ into Thai as per international recommendations, and to test its reliability and validity in the Thai context METHODS: The JOACMEQ was translated into Thai, using international guidelines. Cervical myelopathy patients (n = 70; 31 males) were asked to complete the Thai version JOACMEQ twice (4 weeks apart). Test-retest reliability was analyzed using the intra-class correlation coefficient (ICC). Internal consistencies were analyzed using Cronbach's alpha, while the construct validity was compared with the Thai version modified SF-36; using the Spearman's rank correlation coefficient. RESULTS: The Thai JOACMEQ produced good reliability (i.e., the ICC was >0.9 in 2 parameters and >0.8 in one). Overall the Cronbach's α for the 24 questions showed very high internal consistency (Cronbach's α > 0.8) and almost all Cronbach's α showed satisfactory internal consistency except for bladder function. The Spearman's rank correlation for all the JOACMEQ parameters had a positive correlation with all Thai SF 36 subscales, especially the quality of life parameter, which showed a strong correlation with all SF-36 subscales. CONCLUSION: The Thai version of the JOACMEQ had satisfactory internal consistency and test-retest reliability: it also had good construct validity. It can therefore be used as a reliable tool for assessing quality of life for cervical myelopathy patients in Thailand.

Overactive bladder in cervical spondylotic myelopathy.

BACKGROUND: Overactive bladder (OAB) is a new disease concept defined by the International Continence Society in 2002. There have been no reports of OAB among patients with cervical spondylotic myelopathy assessed on the basis of symptom questionnaires. METHODS: One-hundred-and-six patients diagnosed with cervical spondylotic myelopathy and treated by use of laminoplasty were examined. The patients were classified into two groups, those identified as having OAB (OAB group) and those identified as not having OAB (non-OAB group), by use of the Overactive Bladder Symptom Score collected before and 1 year after surgery. The clinical results for the two groups were assessed. OAB symptom prevalence and post-operative symptom improvement were investigated 1 year postoperatively. RESULTS: Of the 106 patients, 50 were identified as having OAB (symptom prevalence 47.2%). Of these 50 patients, symptom improvement was observed for only 14 (28%) 1 year after surgery. For both groups good improvement on the basis of the Japanese Orthopedic Association score was observed 1 year postoperatively, but there were no significant differences between them. CONCLUSIONS: Post-operative improvement of OAB symptoms in cervical spondylotic myelopathy patients was low, which indicated that OAB was most frequently attributable to non-neurogenic and idiopathic, but not neurogenic, causes. It is considered necessary to tell patients with cervical spondylotic myelopathy that the possibility of post-operative OAB symptom improvement is not high when the explanation for informed consent is given before the operation.

Biomechanical effects of pedicle screw fixation on adjacent segments.

Various biomechanical investigations have attempted to clarify the aetiology of adjacent segment disease (ASD). However, no biomechanical study has examined in detail the deformation behaviour of the adjacent segments when both pure torque and an angular displacement load are applied to the vertebrae along multiple segments. The purpose of this study is to investigate the biomechanical effects of pedicle screw fixation on adjacent segments. Ten cadaveric lumbar spines (L2-L5) of boars were used. Control and fusion models were prepared by disc damage and pedicle screw fixation of each specimen, and then, bending and rotation tests were performed using a six-axis material tester. In the biomechanical tests regulated by an angular displacement load, the range of motion (ROM) of the cranial and caudal adjacent segments in antero-posterior flexion and lateral bending was increased by about 20 % (p < 0.05), and the maximal torque in the fusion model was about threefold (p < 0.05) that in the control model. And in axial rotation, the ROM of cranial and caudal adjacent segments was increased by about 100 % (p < 0.001), and the maximal torque was about sixfold (p < 0.01) that in the control model. The ROM of adjacent segments was significantly increased after pedicle screw fixation as assessed by biomechanical tests regulated by an angular displacement load, but not in those regulated by torque. We present the results of biomechanical tests regulated by torque and angular displacement and show that the maximum torque of the fusion model was larger than that of the control model in the biomechanical test regulated by an angular displacement load, suggesting that mechanical stress on the segments adjacent to the fused segment is large. We think that ASD arises after spinal fusion surgery as a mechanism to compensate for the ROM lost due to excessive fusion by pedicle screw fixation, so that a large torque may be applied to adjacent segments within a physiologically possible range, and it might gradually lead to a degenerative intervertebral disc or progression of spondylolisthesis in the adjacent segments.

An increase in height of spinous process is associated with decreased heights of intervertebral disc and vertebral body in the degenerative process of lumbar spine.

PURPOSE: Currently degeneration of the intervertebral disc and joint in the degenerative process of the lumbar spine has mainly attracted the attention, however, there are very few literatures focusing on the height of the spinous process. Our objective was to examine in what generation the change in spinous process height occurs and how the change is involved in the degenerative process of the lumbar spine. METHODS: CT or CT myelography of 1,015 patients, 536 males and 579 females were measured in 6 items, including the heights of the L4 and L5 vertebral bodies, the L4 and L5 spinous processes, the L4/5 intervertebral disc, and the L5/S1 intervertebral disc. All data of the 6 items were analyzed and compared between gender in 5 age groups (40s, 50s, 60s, 70s and 80s). RESULTS: The results indicated a significant increase in the height of the L4 and L5 spinous process (P < 0.01) in the 60- to 70-year-old group for both genders, and also showed that the L4 and L5 vertebral body height was significantly decreased in the 50- to 60-year-old group (P < 0.01 in males, P < 0.001 in females). CONCLUSIONS: Changes in the spinous process morphology followed degenerative changes of the intervertebral disc and vertebral body in the degenerative process of the lumbar spine. This result may suggest that the morphological change of an increase in the height of the spinous process may be a kind of biological defense reaction to stabilize the intervertebral portion.

Porosity of ß-tricalcium phosphate affects the results of lumbar posterolateral fusion.

STUDY DESIGN: Clinical case-control and cross-sectional study. OBJECTIVES: To determine the influence of different porosities of ß-tricalcium phosphate (ß-TCP) as a bone substitute combined with local autograft bone obtained from decompression for lumbar posterolateral fusion (PLF). SUMMARY OF BACKGROUND DATA: Several reports have documented a high bone fusion rate using ß-TCP as a bone substitute. ß-TCP is increasingly used to supplement autograft in lumbar PLF, but the influence of different porosities of ß-TCP for the lumbar PLF has not been reported. METHODS: Sixty patients who were diagnosed with lumbar degenerative diseases and treated with 2-level noninstrumented lumbar PLF were divided into 2 groups. Thirty patients were treated with 75% porous ß-TCP (ß-TCP-75 group), and the others were treated with 60% porous ß-TCP (ß-TCP-60 group). The clinical and radiographic results of each patient were assessed at 2 years postoperatively. RESULTS: Both the groups showed a good improvement rate of the Japanese Orthopaedic Association score (JOA score) at 2 years postoperatively, but there were no significant differences between them. The ß-TCP-75 group represented a bone fusion rate of 70.0% (64.7% in men, 76.9% in women) and the ß-TCP-60 group was 93.3% (87.5% in men, 100.0% in women). The latter exhibited a significantly better bone fusion rate than the ß-TCP-75 group (P<0.05). CONCLUSIONS: In lumbar PLF, 60% porous ß-TCP granules achieved a higher bone fusion rate than 75% porous ß-TCP granules.

Evaluation of Central Sensitization Inventory in Patients Undergoing Elective Spine Surgery in a Multicenter Study.

STUDY DESIGN: This study is a retrospective review. OBJECTIVE: Central sensitization (CS) is a neurological phenomenon that involves hypersensitivity of the central nervous system. The central sensitization inventory (CSI) was developed as a screening tool to assess CS-related symptoms. The purpose of this study was to evaluate the association of preoperative CSI scores with patient-reported outcome measures (PROMs) including neurological symptoms for patients who underwent spine surgeries in a multicenter study. METHODS: A consecutive 673 patients who underwent spine surgery at 8 different institutions were included in this study. Preoperative CSI scores were assessed for all subjects. The participants completed the following PROMs: the Oswestry Disability Index (ODI), the Japanese Orthopaedic Association (JOA) back pain evaluation questionnaire (JOABPEQ) for lumbar spinal diseases, and the JOA cervical myelopathy evaluation questionnaire (JOACMEQ) for cervical spinal diseases. The association of CSI scores with PROMs was statistically evaluated. RESULTS: The average CSI score for the total subjects was 23.6 ± 13.5. The subjects with CS-related symptoms (CSI ≥ 40) were 13.2% (n = 89). The CSI score showed a significant and weak-to-moderate correlation with the PROMs including neurological symptoms that included all the domains of the JOACMEQ for cervical spinal diseases, and JOABPEQ and ODI for lumbar spinal diseases. Among these, psychological factors had the most influence on the correlation with CSI score. CONCLUSION: Central sensitization evaluated by the CSI is related to neurological symptoms and health-related quality of life in patients undergoing elective spine surgery.

Does Central Sensitization Influence Outcomes of Lumbar Discectomy Surgery in Patients With Lumbar Disc Herniation? A Multicenter Prospective Study.

STUDY DESIGN: Multicenter prospective study. OBJECTIVE: Patients with central sensitization (CS) are reported to be at high risk of poor outcomes after spinal surgery. However, the influence of CS on surgical outcomes for lumbar disc herniation (LDH) remains unknown. This study aimed to examine the association between preoperative CS and surgical outcomes in LDH patients. METHODS: A total of 100 consecutive patients with LDH (mean age 51.2) who underwent lumbar surgery were included in this study. The extent of CS was evaluated using the central sensitization inventory (CSI), a screening tool for CS-related symptoms. The patients completed the following CSI and clinical outcome assessments (COAs) preoperatively and 12 months postoperatively: the Japanese Orthopaedic Association (JOA) score for back pain, JOA back pain evaluation questionnaire (JOABPEQ), and Oswestry Disability Index (ODI). The association between preoperative CSI scores, and preoperative and postoperative COAs was analyzed, and the postoperative changes were statistically evaluated. RESULTS: The preoperative CSI score significantly decreased 12 months postoperatively. Preoperative CSI scores showed a significant correlation with most COAs; however, a significant correlation was only identified in the social function and mental health domains of JOABPEC postoperatively. Higher preoperative CSI showed worse preoperative COAs; however, all COAs significantly improved regardless of CSI severity. There were no significant differences in any COAs among the CSI severity groups 12 months postoperatively. CONCLUSIONS: The results of this study showed that lumbar surgeries significantly improved the COAs regardless of preoperative severity of CS in patients with LDH.

Personality of outpatients with malignant tumors: a cross-sectional study.

BACKGROUND: There have been scarce large-scale studies investigating the personality of patients with malignant tumors. The purpose of this study is to determine the characteristic personality in malignant tumors outpatients. METHODS: Three thousand and three among 5013 consecutive outpatients who consented to answer the Japanese Maudsley Personality Inventory questionnaires were divided into two groups. 603 outpatients diagnosed with malignant tumors (M group) and the other 2400 outpatients (non-M group) were enrolled in this study. We determined three scores such as introversion/extroversion (E-score), neuroticism (N-score), and lie detection (L-score). All data were used to compare the two groups. RESULTS: Average E-score was slightly higher, and average N-score was slightly lower in M group than that in non-M group, and no significant differences between the two groups. However, the average L-score in M group was significant higher than that in non-M group (p < 0.01). CONCLUSION: Outpatients with malignant tumors showed a significantly higher L-score on MPI when compared with patients with non-malignant tumors. These results stress the importance of taking the mentality of patients with cancer into consideration when conducting treatment and care.

Magnetic resonance imaging findings of remnants of an intradural oil-based contrast agent: report of a case.

BACKGROUND: Myodil (iophendylate), an oil-based positive contrast media, now discontinued, was widely used for performing myelography 30-70 years ago. We identified this agent as the explanation for uncommon magnetic resonance imaging (MRI) findings in a patient with thoracic spinal fracture. DESIGN: Case report and literature review. FINDINGS: An 81-year-old man complained of back pain after falling down stairs. Anamnesis revealed that he had undergone myelography with an oil-based contrast agent about 60 years previously as a part of the diagnostic workup for back pain and sudden onset of gait difficulty. Plain radiography of the thoraco-lumbar spine showed a fracture of the eleventh thoracic vertebra and a radio-opaque, oval shadow at the level of the T9-T10 vertebrae. Many small radio-opaque dots with the appearance of a string of pearls were seen from T8 to L3 vertebrae. MRI revealed a sharply demarcated intradural extramedullary mass, of approximately 5 mm in diameter on the left side of the dura in the region of the T9-T10. The mass showed high signal intensity on T1-weighted MRI, and low signal intensity on T2-weighted MRI. CONCLUSIONS: Increased awareness of this rare presentation of procedures performed in the past is essential when atypical radiographic images are encountered. This case illustrates rare sequelae of Myodil use manifesting decades after administration.

Influence of Central Sensitization on Surgical Outcomes of Patients With Degenerative Cervical Myelopathy After Posterior Decompression Surgery: A Multicenter Prospective Study.

STUDY DESIGN: Multicenter prospective study. OBJECTIVE: The influence of central sensitization (CS) on neurological symptoms and surgical outcomes in patients with degenerative cervical myelopathy (DCM) remains unknown. This study aimed to investigate the effects of preoperative CS on surgical outcomes of patients with DCM following posterior decompression surgery. METHODS: 77 consecutive patients with DCM (mean age 67.1) who received posterior decompression surgery were included in this study. The participants completed CS inventory (CSI) scores and the following patient-reported outcome measures (PROMs) preoperatively and 12 months postoperatively: the Japanese Orthopaedic Association (JOA) score for cervical myelopathy and JOA cervical myelopathy evaluation questionnaire (JOACMEQ) for cervical spinal diseases. The association of preoperative CSI scores with preoperative and postoperative PROMs was analyzed, and their changes were statistically evaluated. RESULTS: The preoperative CSI score was significantly decreased at 12 months postoperatively, and it was significantly associated with the JOA score and JOACMEQ preoperatively and at 12 months postoperatively. However, no significant association was observed between preoperative CSI and the postoperative change of any PROMs at 12 months. The posterior decompression surgery significantly improved the JOA scores and 'lower extremity function' and 'quality of life (QOL)' domains of the JOACMEQ, independent of the severity of preoperative CSI score. Multiple regression analysis demonstrated that preoperative CSI was significantly associated with the 'QOL' domain of JOACMEQ and original JOA score at 12 months postoperatively. CONCLUSION: The CSI score can be an auxiliary indicator of surgical outcomes of patients with DCM following posterior decompression surgery.

Direction of the formation of anterior lumbar vertebral osteophytes.

BACKGROUND: X-ray images of lumbar degenerative diseases often show not only claw osteophytes, but also pairs of osteophytes that form in a direction away from the adjacent disc. We have investigated the direction of the formation of anterior lumbar vertebral osteophytes across the lumbar vertebrae using a sufficient number of lumbar radiographs, because osteophytes images can provide essential information that will contribute to the understanding of the pathology and progress of lumbar spine degeneration. METHODS: The direction of the formation of 14,250 pairs of anterior lumbar vertebral osteophytes across the adjacent intervertebral discs in 2,850 patients who were all over 60 years old was investigated. Anterior lumbar vertebral osteophytes were distributed into six groups based on the direction of extension of each pair of osteophytes across the intervertebral disc space. RESULTS: In L1-L2 and L2-L3, the number of patients classified into groups B (the pair of osteophytes extended in the direction of the adjacent disc) and C (almost complete bone bridge formation by a pair of osteophytes across the intervertebral disc space) was larger than that classified into group D (the pair of osteophytes extended in a direction away from the adjacent disc). In L3-L4, L4-L5 and L5-S1, the number of patients in group D was greater than that of patients belonging to groups B and C. CONCLUSION: Our study showed that pairs of osteophytes frequently formed in the direction of the adjacent disc in the upper lumbar vertebrae (L1-L2 and L2-L3) and in the direction away from the adjacent disc in middle or lower lumbar vertebrae (L3-L4, L4-L5, and L5-S1).

Biomechanical Problems Related to the Pedicle Screw System.

AIM: To assess biomechanical problems related to pedicle screw (PS) systems. MATERIAL AND METHODS: Functional spinal units (L3-4) of deer were evaluated using a 6-axis material testing machine. For the specimen models, we prepared an intact model, a damaged model, a PS model, and a crosslink model. We checked the range of motion (ROM) during bending and rotation tests. Eight directions were measured in the bending test: anterior, right-anterior, right, right-posterior, posterior, left-posterior, left, and left-anterior, and 2 directions were measured in the rotation test (right and left). RESULTS: ROMs of the PS model were smaller than those of the intact model in all directions. However, ROMs of the PS model in the rotation test were smaller than those of the damaged model and larger than those of the intact model. The stability of the crosslink model was better than that of the PS model during the bending test, but ROMs of the crosslink model were larger than those of the intact model during the rotation test. CONCLUSION: Excessive bending rigidity and rotational instability are the biomechanical problems related to PS systems. Based on these results, we speculate that one of the most significant causes of adjacent segment disease is excessive bending rigidity and one of the most important causes of instrumentation failure is rotational instability.

RETRACTED: Three-Minutes Sitting Test for evaluating lumbar foraminal stenosis: A preliminary report.

This article has been retracted.

Biomechanical Stability of a Cross-Rod Connection with a Pedicle Screw System.

BACKGROUND Surgery with pedicle screw instrumentation does not provide sufficient torsional stability. This leads to pseudoarthrosis, loosening of the pedicle screws, and, ultimately, implant failure. MATERIAL AND METHODS Functional spinal units from 18 deer were evaluated using a 6-axis material testing machine. As specimen models, we prepared an intact model, a damaged model, a cross-rod model, and a cross-link model. We measured the range of motion (ROM) during bending and rotation tests. RESULTS The range of motions of cross-rod model were almost equal to those of cross-link model during the bending test. In the rotation test, the average ranges of motion of the intact, cross-rod, and cross-link models were 2.9°, 3.1°, and 3.9° during right rotation and 2.9°, 3.1°, and 4.1° during left rotation, respectively. The range of motions of the cross-rod model were significantly smaller than those of the cross-link model during the rotation test. The range of motions of the intact model were significantly smaller than those of the cross-link model during the rotation test, but there were no statistically significant differences between the range of motions of intact model and cross-rod model during the rotation test. CONCLUSIONS The stability of spinal fixation such as cross-rod model is equal to the fixation using the pedicle screw system during bending tests and equal to that of the intact spine during rotation tests.

A survey of workplace violence against physicians in the hospitals, Myanmar.

OBJECTIVE: Workplace violence in hospitals is recently becoming a major global concern in many countries. However, in Myanmar, we have felt that patients and their families have rarely made unreasonable complaints in hospitals, and then, the purpose of this study is to report the current state of workplace violence in hospitals in Myanmar. Participants are 196 physicians (108 males and 88 females) in hospitals in Myanmar. RESULTS: A descriptive survey was conducted in regard to verbal abuse and physical violence from patients or the people concerned. At the results of this study, the percentages of physicians who have encountered verbal abuse and those who have encountered physical violence are markedly low (8.7 and 1.0%, respectively). The present study is the first to report the frequencies of verbal abuse and physical violence against physicians in a least developed country, and the results of the present study are important in terms of discussing workplace violence in hospitals.

Characteristics of Patients with High Lie Scores in a Personality Test.

BACKGROUND: It is reported that persons with high Lie score (L score) of a personality test are aggressively self-confident and are also related to depression or schizophrenia In this study, we examined the characteristics of patients with high L scores on the Maudsley Personality Inventory (MPI) and examined the significance of the L score. MATERIALS AND METHODS: We collected the data of 10789 subjects and examined the relationship between L score or the number of characteristic biased persons and the parameters of age, sex, education level, occupation, and degree of pain. Furthermore, we examined the changes in extraversion-introversion (E score), neuroticism (N score), and L scores at approximately 1 year after surgery in 1711 patients who underwent surgery at our university hospital or affiliated hospitals. RESULTS: L score was significantly higher among persons with a high degree of pain, and ratio of the characteristic biased persons in L score was significantly high among persons in their 40s to 60s, healthcare professionals and those with a high degree of pain. Moreover, L score scarcely changed between before and after surgery when compared with E score and N score. CONCLUSION: L score is not greatly influenced by an individual's state of mind or situation at different times, and may indicate the personality traits proper to the person. It is shown that L score may indicate the personality trait characteristics of persons who want to make themselves look good in the eyes of other.

Do the Position and Orientation of the Crosslink Influence the Stiffness of Spinal Instrumentation?

STUDY DESIGN: Biomechanical study of double-level pedicle screw constructs with or without crosslinks (CL) in an unstable model. OBJECTIVES: The purpose of this study is to investigate the optimal position and orientation of the CL. SUMMARY OF BACKGROUND DATA: Several reports have described biomechanical research on such CL, but no definite consensus has been reached regarding the effects. Very few studies have examined the position and orientation of the CL. The question of where and how the CL should be clinically set remains unanswered. METHODS: Ten cadaveric lumbar spines (L3-L5) of boars were used and 7 models were prepared by the sequential damage and spinal instrumentation of each specimen. Bending stiffness was measured in flexion, extension, lateral bending, and axial rotation for each model using 6-axis material tester under torque of 0 to ±3 N m. Results for each configuration were compared using analysis of variance and the Turkey-Kramer test. RESULTS: In flexion, extension, and lateral bending, 7 models showed similar stiffness with no significant differences. In axial rotation, stiffness increased significantly (P<0.05) in the cephalic, central, caudal, and oblique CL models in comparison with that of the no CL model, and stiffness of the horizontal 2 CL and oblique 2 CL models was significantly higher than that of cephalic, central, caudal, and oblique CL models (P<0.05). However, no significant differences in stiffness were seen between cephalic, central, and caudal CL models, between the central and oblique CL models, or between the horizontal and oblique 2 CL models. CONCLUSIONS: Concomitant use of CLs significantly increased axial rotational stiffness, even though stiffness in flexion, extension, and lateral bending was not increased. In addition, stiffness in axial rotation significantly improved with the use of 2 CLs instead of a single CL, and stiffness was unchanged by position and orientation of CL.