The invention of new anterior spinal instrumentation prototype: a structural analysis of KKU expandable cage.

OBJECTIVE: Report the invention and structural analysis of the new model of anterior spinal instrumentation (KKU expandable cage) that is expandable for space filling after vertebral body resection while simultaneously stabilize the upper vertebra with the lower vertebra, to tolerate the thoracolumbar physiologic load and augment the interbody arthrodesis of the spine. MATERIAL AND METHOD: The new model of expandable anterior spinal instrumentation, named KKU expandable cage, was invented and designed using the computer. The structural property of this instrumentation was tested and analyzed using the computer based structural analysis software. RESULTS: The KKU expandable cage made out of 316L stainless steel is 0.0301044 kg in mass and 3.76305 x 10(-6) m3 for volume. The outer diameter of the device is 23 mm and the height can expand from 20 mm to 35 mm for space filling after thoracolumbar vertebrectomy. The stress in the device after applying the maximal thoracolumbar physiologic compression load (1250N) is between 11692.7 N/m2 to 94.7266 x 10(6) N/m2, less than compression strength of the 316L stainless steel (170 x 10(6) N/m2). CONCLUSION: The stainless steel 316 L KKU expandable cage for anterior spinal instrumentation can withstand the maximal thoracolumbar physiologic compression load without failure whereas its expandable property enable it to fill and fit in the space reaching the height of 35 mm. Therefore, the insertion of this device into a space after thoracolumbar or lumbar corpectomy or vertebrectomy for the vertebral osteomyelitis or vertebral metastasis is appropriate. The device can also stabilize the spine and tolerate the maximal physiologic compression load of the thoracolumbar vertebrae. Therefore, the device helps decrease the need for bone graft or bone substitute in these patients.

Reliability of the medical outcomes study short-form survey version 2.0 (Thai version) for the evaluation of low back pain patients.

OBJECTIVES: To determine the reliability of Thai version of the medical outcomes study short-form survey version 2.0 (SF-36V2) in low back pain patients. MATERIAL AND METHOD: The authors developed the Thai version of the Medical Outcomes Study Short-Form Survey version 2.0 (SF-36V2) and tested it in 100 low back pain patients. Reliability of the Thai version of SF-36V2 was assessed by internal consistency using Chronbach's alpha coefficient and item-scale correlation. RESULTS: The authors demonstrated that the Chronbach's alpha coefficient of the physical health and mental health summary scales were 0.93 and 0.92 respectively. The Chronbach's alpha coefficient of eight scales in the Thai version of the SF-36V2 ranging was 0.72 - 0.94. The Chronbach's alpha coefficient tested in acute or chronic low back pain patients whether they have back pain only or back pain with radiculopathy ranging was 0.72-0.93. The item correlation coefficient for the 35 items within the eight health aspects ranged from 0.43 to 0.8. CONCLUSION: The Thai version of the Medical Outcomes Study Short-Form Survey version 2.0 (SF-36V2) is a reliable tool for assessing functional disability of low back pain in Thai patients.

Reliability of the Roland - Morris Disability Questionnaire (Thai version) for the evaluation of low back pain patients.

OBJECTIVE: To determine the reliability of the Thai version of the Roland - Morris disability questionnaire in low back pain patients. MATERIAL AND METHOD: To develop Thai version of the Roland - Morris disability questionnaire and test it in 120 low back pain patients. Reliability of the Thai version of the Roland - Morris disability questionnaire was assessed by internal consistency using Cronbach's alpha coefficient. RESULTS: The overall Cronbach's alpha coefficient of the scale was 0.83. The Cronbach's alpha coefficient of each question in the Thai version of the Roland - Morris disability questionnaire exceeded 0.7 (range, 0.71- 0.93). The Cronbach's alpha coefficient tested in acute or chronic low back pain patients whether they have back pain only or back pain with radiculopathy which also exceeded 0.7 (range, 0.83-0.87). CONCLUSION: The Thai version of the Roland - Morris disability questionnaire is a reliable tool for assessing functional disability of low back pain in Thai patients.

The midpedicular and interpedicular distance of thoracolumbar vertebrae.

OBJECTIVES: 1. To introduce the measurement of the midpedicular distance (MPD) as an alternative to the interpedicular distance (IPD). 2. To measure the IPD and MPD of T11, T12, L1 and L2 vertebrae on anteroposterior (AP) plain film of the normal spine. 3. To study the relationship of the IPD and MPD of T11 to L2 of the normal spine. STUDY DESIGN: Thoracolumbar AP plain film of 89 subjects (39 males, 50 females) with an average age of 47.6 years (range 21-78 years) from the roentgenographic files were included. Both the IPD and MPD of T11, T12, L1 and L2 were measured by two observers. The mean difference of IPD and MPD at these four levels were compared by using a one-way ANOVA. The relationship of the IPD and MPD measured from the T11 to L2 levels were evaluated using the simple linear regression model. RESULTS: The mean IPD was progressively wider (p = 0.000) from the T11 to L1 level, but no significant difference (p = 0.308) was found between the mean IPDs of L1 and L2. The mean MPD of each level was significantly different from the others (p = 0.000) except the mean MPDs of T12 and L1 (p = 1.000). Both the IPD and MPD had a statistically significant linear relationship with the level of the vertebrae from T11 to L2 (p = 0.000) with the coefficients of determination (R2) of 0.39 and 0.28, respectively. CONCLUSION: More care should be taken in clinical practice when measuring the IPD of a fractured vertebra relative to those of adjacent lower levels in order to determine whether or not widening has occurred, especially IPD L1 vis-à-vis IPD L2. MPD measurement has no advantage over the IPD measurement but is a useful alternative when a comparison of the pedicular distance of L1 and L2 is needed.