The EOS® imaging system, a new imaging modality which offers low dose, weight bearing and full body X-ray imaging, requires a new standing position where patients put their hands and forearms on the wall vertically for stability. Although this method provides enough support for the patients during the extended X-ray acquisition time, its impact on the postural balance and sagittal profile of the spine and sacro-pelvic parameters has not been evaluated. The goal of this study is to identify the impact of patients' arm positioning on the sagittal profile and postural balance of the patient and subsequently propose a standardized method for full spine X-ray acquisition in the EOS® imaging system.

Spino-pelvic sagittal analysis and postural assessment are important parameters in adolescent idiopathic scoliosis (AIS) treatment and surgical planning.The three-dimensional (3D) shape of the spine is impacted by the patients' posture particularly in adolescents with flexible spinal curves. The latter highlights the importance of the patients' positioning during X-ray acquisition in order to avoid any misleading measurements that may adversely impact monitoring and surgical curve correction in AIS.

Participating subjects will undergo two bi-planar X-rays in different positions. The positions will be instructed by the means of graphical presentation and verbal explanation by the radiology technician. The first standing position in the EOS® imaging system for full spinal X-ray acquisition will consist of putting both hands and forearms in front of the subject on the wall vertically. In the second position, knuckles are loosely placed on ipsi-lateral clavicles. Bi-planar X-rays will be taken in the EOS® imaging system for both positions.

Moreover to compare the postural balance of the patient in the two described positions, a pressure mat will be placed in the EOS® system. The pressure mat will be calibrated with the EOS® system and permits to identify the position of the center of pressure (COP) with respect to the anatomical landmarks. The magnitude of pressure under the patients' feet will be measured during each X-ray and compared.

Inclusion Criteria:

• Subjects age 10-18
• Diagnosis of adolescent idiopathic scoliosis
• Prescribed bi-planar full spine X-ray images
• Must be able to stand still for 10 seconds without any support
• Must be able to follow verbal and visual instruction

Exclusion Criteria:

• Previous surgical treatment
• Diagnosis of a neuro-muscular disorder
• Have supernumerary vertebrae, congenital deformities, spondylolisthesis, or spina bifida
• Have any other musculoskeletal disorder that impacts standing balance such as hip, knee, ankle pain and instability or lower back pain
• BMI higher than 30
• Pregnant or lactating females
• Parents/guardians or subjects who, in the opinion of the Investigator, may be non-compliant with study schedules or procedures

Outpatient adolescent idiopathic scoliosis patients visiting the orthopedic clinic at Children's Hospital of Philadelphia who require bi-plannar full spine x-ray imaging for clinical purposes.

Identifiable pressure mat data from select subjects that is recorded during this study will be shared with investigators at this institution working on another approved study which requires pre-surgical pressure mat data. Many subjects in the companion study will have already undergone surgery, yet none in the current study will have at the time pressure mat data is recorded. Thus this data will be shared. Data will be stored in a password protected file on a secure shared drive and is only accessible by IRB-approved members of the current and companion study teams.

40 subjects consented to participate; however 3 were subsequently deemed ineligible. The analysis population only includes the 37 eligible subjects.

30 Minutes