Study results were too significant

This is a prospective, single-blinded, randomized-controlled study comparing a new method (slump-sitting) with the conventional method (forward erect bending) of performing lumbar spine flexion X-rays.

Power calculation was performed based on preliminary pilot results using a clinically set difference of 10 degrees (SD 15 degrees) change in mean global lumbar spine flexion between sitting and standing postures. An estimated sample population of 100 patients was deemed necessary for this study to fulfill a statistical power of 90% and a two-sided 5% significance level.

Block randomization of every 4 subjects was performed at the beginning of the study to ensure equal numbers of subjects in both study arms for comparison and these results were concealed in envelopes.

During the clinical consult, history taking was performed as per a usual clinic visit. Specific patient's details including age, occupation, presence and severity of back pain, presence and severity of leg pain, and neurological symptoms were documented. Physical examination was performed accordingly and parameters such as clinical range of motion of the lumbar spine, neurological signs and provocative tests were recorded for later analysis.

For the flexion radiographs, both the new and conventional methods were performed on each patient. These pictures were made into charts and visually displayed. They serve as instructional manuals for patients during the radioimaging process, which are again reinforced with verbal instructions from the on-duty radiographers.

Both images were done with the X-ray beam projected from the patients's left and at a distance of 100cm from the patient. The central beam was directed at the estimated centre of L3, with T11 vertebral body and mid-body of the sacrum serving as superior and inferior limits respectively. A single extension view of the lumbar spine was also performed after these flexion views. All radiographs were stored on Digital Imaging and Communications in Medicine (DICOM) format and viewed with Centricity Enterprise Web V3.0 (8.0.1400.128) for assessment.

Measurements were done by 2 independent reviewers and an average of their readings was recorded. Both reviewers were blinded to the method in which flexion X-rays was taken.

Interim data analysis is planned at 30th patient and the 60th patient. During this time point, the primary objective which look at mean global lumbar spine flexion between sitting and standing postures is assessed.

All collected data and measurements were tabulated using Microsoft Excel 2011(Version 14.0 (32-bit)) and analyzed using International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS Version 23.0).

For the main analysis of both global and segmental lumbar flexion, as well as the measured displacements obtained between the two flexion methods, paired t-test was employed.

There is no requirement to follow up the patients in this study. The whole study is to be completed within 1 year of recruitment

Inclusion Criteria:

• Patients above 45 years of age;
• With mechanical low back pain,
• With spondylolisthesis
• Physically able to position themselves correctly for both methods of X-rays

Exclusion Criteria:

• Previous spinal interventions
• Suspected findings for spinal malignancies, spinal trauma, and inflammatory spinal diseases
• Pregnant women