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Flexion radiographs have been used to identify cases of spinal instability. However, current methods are not standardized and are not sufficiently sensitive or specific to identify instability.This study aimed to introduce a new slump sitting method for performing lumbar spine flexion radiographs and comparison of the angular range of motions (ROMs) and displacements between the conventional method and this new method.This study used is a prospective study on radiological evaluation of the lumbar spine flexion ROMs and displacements using dynamic radiographs.Sixty patients were recruited from a single spine tertiary center.Angular and displacement measurements of lumbar spine flexion were carried out.Participants were randomly allocated into two groups: those who did the new method first, followed by the conventional method versus those who did the conventional method first, followed by the new method. A comparison of the angular and displacement measurements of lumbar spine flexion between the conventional method and the new method was performed and tested for superiority and non-inferiority.The measurements of global lumbar angular ROM were, on average, 17.3° larger (p.0001) using the new slump sitting method compared with the conventional method. They were most significant at the levels of L3-L4, L4-L5, and L5-S1 (p.0001, p.0001 and p=.001, respectively). There was no significant difference between both methods when measuring lumbar displacements (p=.814).The new method of slump sitting dynamic radiograph was shown to be superior to the conventional method in measuring the angular ROM and non-inferior to the conventional method in the measurement of displacement.

Sitting spinal alignment is increasingly recognized as a factor influencing strategy for deformity correction. Considering that most individuals sit for longer hours in a "slumped" rather than in an erect posture, greater understanding of the natural sitting posture is warranted.This study aimed to investigate the differences in sagittal spinal alignment between two common sitting postures: a natural, patient-preferred posture; and an erect, investigator-controlled posture that is commonly used in alignment studies.This is a randomized, prospective study of 28 young, healthy patients seen in a tertiary hospital over a 6-month period.Twenty-eight patients (24 men, 4 women), with a mean age of 24 years (range 19-38), were recruited for this study. All patients with first episode of lower back pain of less than 3 months' duration were included. The exclusion criteria consisted of previous spinal surgery, radicular symptoms, red flag symptoms, previous spinal trauma, obvious spinal deformity on forward bending test, significant personal or family history of malignancy, and current pregnancy.Radiographic measurements included sagittal vertical axis (SVA), lumbar lordosis (LL), thoracolumbar angle (TL), thoracic kyphosis (TK), and cervical lordosis (CL). Standard spinopelvic parameters (pelvic incidence, pelvic tilt [PT], and sacral slope) and sagittal apex and end vertebrae were also measured.Basic patient demographics (age, gender, ethnicity) were recorded. Lateral sitting whole spine radiographs were obtained using a slot scanner in the imposed erect and the natural sitting posture. Statistical analyses of the radiographical parameters were performed comparing the two sitting postures using chi-squared tests for categorical variables and paired t tests for continuous variables.There was forward SVA shift between the two sitting postures by a mean of 2.9 cm (p.001). There was a significant increase in CL by a mean of 11.62° (p.001), and TL kyphosis by a mean of 11.48° (p.001), as well as a loss of LL by a mean of 21.26° (p.001). The mean PT increased by 17.68° (p.001). The entire thoracic and lumbar spine has the tendency to form a single C-shaped curve with the apex moving to L1 (p=.002) vertebra in the majority of patients.In a natural sitting posture, the lumbar spine becomes kyphotic and contributes to a single C-shaped sagittal profile comprising the thoracic and the lumbar spine. This is associated with an increase in CL and PT, as well as a constant SVA. These findings lend insight into the body's natural way of energy conservation using the posterior ligamentous tension band while achieving sitting spinal sagittal balance. It also provides information on one of the possible causes of proximal junctional kyphosis or proximal junctional failure.