Inclusion criteria pathological subjects:

1. Adult (>18 years old) subjects suffering from a adult spinal deformity with sagittal or coronal plane misalignment diagnosed on EOS imaging.
2. Ability to walk at least 50 meters distance independently without a walking aid.
3. No documented neurological disease or vestibular lesion affecting balance nor a current history of musculoskeletal disorders of the lower extremities affecting motor performance.

Inclusion criteria control group:

1. Adults (> 18 year old)
2. No current history of back pain and spinal deformity.
3. Ability to walk at least 1000 meters distance independently without a walking aid.
4. No documented neurological disease or vestibular lesion affecting balance nor a current history of musculoskeletal disorders of the lower extremities affecting motor performance.

Exclusion criteria ASD patients:

1. Age < 18 years old and > 79 years old
2. Absence of adult spinal deformity
3. Non-ability to walk at least 50 meters distance independently, with or without a walking aid.
4. Missing patient informed consent
5. Patients presenting with a neurological disease affecting balance other than Parkinson's disease such as stroke and/or Vestibular lesion
6. Patients with a history of spinal fusion surgery.
7. Patients with a current history of diagnosed musculoskeletal disorders of the trunk and/or lower extremities affecting the motor performance such as severe hip arthrosis with or without flexion contracture, severe knee arthrosis, severe ankle arthrosis, severe leg length discrepancy (> 3 cm)

Exclusion criteria control group:

1. Age < 18 years old and > 79 years old
2. Backpain and/or Sciatica at time of the study
3. Presence of adult spinal deformity leading to a pathological sagittal alignment
4. Non-ability to walk at least 1000 meters distance independently without a walking aid
5. Missing patient informed consent
6. Patients presenting with a neurological disease affecting balance such as Stroke, Parkinson's disease and/or Vestibular lesion
7. Patients with a current history of diagnosed musculoskeletal disorders of the trunk and/or lower extremities affecting the motor performance such as severe hip arthrosis with or without flexion contracture, severe knee arthrosis, severe ankle arthrosis, severe leg length discrepancy (> 3 cm)