Develop reliable methods for functional assessment, for trunk strength, of Adult Spinal Deformity (ASD) patients and create a first clinical and normative database

1. Compare functionality of ASD and control subjects
2. Relate functionality of ASD patients to their pathology, in terms of spinal deformity and muscle condition

The overall aim of the project is to initiate the shift from 2D to 3D mechanically correct and dynamically informed decision-making in Adolescent Idiopathic Scoliosis (AIS), by identifying and integrating the key parameters that overcome the present limitations of 2D static AIS care. Within the timeframe of the project, we will not be able to identify and integrate the key parameters that will overcome all undesired surgical outcomes and therefore, in addition to the overall surgical outcome assessed by patient reported outcome measures (PROMs) we will specifically focus on post-surgery shoulder balance. Since an elevated shoulder after surgery is one of the most common undesired surgical outcomes (approximately 16% of the treated AIS patients) linked with treatment satisfaction and psychological well-being.

To achieve the overall aim, the project comprises two objectives that will allow us to advance towards 3D dynamically informed decision-making in AIS care:

1. To shift towards a 3D mechanically correct overview of the spinal deformity. The current state-of-the-art guidelines for the selection of fusion levels in AIS patients are based on 2D static radiographic parameters[26]. In order to improve the current state-of-the-art evaluation method, efforts should be made towards a 3D dynamic visualization of the deformity, especially considering that AIS is a 3D deformity of the spine. In addition, the treating surgeon has only limited information on the mechanical behavior of the spine of the AIS patient as the traction radiograph tests that show the displacement of the spine are typically only assessed qualitatively. To overcome this issue, the spine stiffness should be incorporated in order to thrive towards a biomechanically-informed state-of-the-art 3D model.
2. To identify the key 3D parameters that should be considered by the surgeon Once a biomechanically-informed subject specific 3D model that incorporates the mechanical behavior of the spine is developed within objective 1, the crucial next step will be to identify the key parameters that have the potential to improve the clinical decision-making in AIS. As highlighted before, we will focus on post-surgery shoulder balance and the PROMs.

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)