This study intends to investigate the changes in gait pattern in adult spinal deformity (ASD) patients with sagittal imbalance. It will investigate the gait kinematics in patients who have a mismatch of their spinopelvic parameters, and a positive sagittal balance. The investigators hypothesise that patients with abnormal spinopelvic parameters may demonstrate a pathological gait pattern.

With an ageing population, ASD presents as a significant health issue with increasing incidence. Most of the earlier literature concentrated on radiographic measurements of the deformity in the coronal plane, and its surgical correction. However, recent publications have demonstrated that sagittal spinopelvic alignment plays a critical role in pain and disability in patients with ASD, and is a primary determinant of health related quality of life measures. There is substantial evidence that restoration of these parameters after spinal reconstructive surgery is correlated with good clinical outcome.

Maintenance of the ideal sagittal alignment allows an individual to maintain an erect posture with minimal energy expenditure. When there is progressive loss of lumbar lordosis, compensatory mechanisms involving the pelvis, hips and knees occur to extend adjacent segments of the kyphotic spine to allow for compensation of anterior translation of the axis of gravity. However, this compensatory mechanism may potentially result in adverse effect. One of the main disabilities in ASD patients with sagittal imbalance is their decreased walking tolerance. The change in the spinal alignment along with these compensatory mechanisms may result in an inefficient gait worsening their walking tolerance.

Few studies in the literature have investigated the changes in gait pattern in patients with sagittal imbalance. Of those, the patient group was heterogeneous, and the only criterion of sagittal imbalance was a positive sagittal vertical axis (SVA), which the investigators now know is not a complete assessment of the sagittal alignment. The investigators propose to study the change in gait pattern in individuals with abnormal spinopelvic parameters, and how this may affect their quality of lives.

Inclusion Criteria:

All patients diagnosed with ASD, fulfilling the following radiographic criteria based on whole spine lateral film are eligible for recruitment:

• SVA bigger than 47mm
• Pelvic tilt (PT) bigger than 22deg
• Pelvic incidence (PI) - lumbar lordosis (LL) bigger than 11deg

Exclusion Criteria:

• If the aetiology of the ASD of the patient is neuromuscular origin
• other pathologies that may affect their gait such as previous trauma or surgeries to the pelvis or the lower limbs and joint replacements
• inability to walk without aids for short distances

Patients with diagnosis of ADS will be recruited in this study conducted by the Department of Orthopaedics and Traumatology.