Spine ultrasound imaging during different upright body positions to determine the most accurate representation of the neutral sagittal balance.

The sagittal spinal alignment is an important aspect for the clinician to
consider in the evaluation and treatment of patients with spinal pathologies
and is becoming more important for the outcomes of surgical treatment. To
capture the sagittal morphology, standing radiographs are the preferred
standard. These radiographs are ideally performed, in a comfortable,
functional, and naturally assumed posture, with the arms at the sides: the
neutral position. However, in this position the arms inhibit adequate
visualization of the spine on a lateral radiograph and therefore numerous
positions have been developed in order to visualise the spine on the lateral
radiograph, such as a standing position with the fingers on the cheeks. In
these adjusted standing positions the position of the arms effects the
alignment of the spine, as well as the reproducibility of measurements between
subsequent radiographs. Previous authors compared the sagittal alignment in the
different adjusted positions. Due to radiation exposure, these studies included
only a restricted number of positions, or used external markers to compare the
different positions. Ultrasound imaging enables us to compare the sagittal
alignment of the neutral position with the adjusted positions, without
radiation exposure. Therefore, in this study, 5 different standing positions
will be compared by ultrasound imaging, to determine which position provides
the most *functional representation* of the neutral standing posture (with the
arms on the side) and to determine which position is the most reliable across
repeated measurements.

To compare the effects of various upper extremity positions on the sagittal
spinal alignment, to determine which position corresponds the most with the
neutral position and to determine which position is the most reliable across
repeated measurements.

Cross-sectional study

Ultrasound imaging is a widely used imaging technique in the regular care of
patients and has proven to be a safe, non-radiating, fast and cheap method. The
Scolioscan® (CE-marked) meets these characteristics too; the most important
benefit of the Scolioscan® is the radiation-free examination in standing
position. For this study, the volunteers will be examined by the ultrasound
device, which takes approximately two minutes of scanning time per scan. If the
most *functional representation* of the sagittal plane on a standing
examination is known, this position could be used for all the imaging
procedure, to make sure the different images are made in the same positions to
avoid alignment differences due to the positioning. There are no noteworthy
risks associated with participating in this study, and no invasive procedures
or contrast administration will be performed.