Sway and Neuromuscular Activity Changes in Adult Degenerative Scoliosis Patients Pre and Post Surgery Compared to Controls

Presented at SMISS Annual Forum 2018
By R. Haddas
With Isador Lieberman MD, MBA, FRCSC,

Disclosures: R. Haddas A; Medtronic Inc., Alphatec Spine Inc., The Cervical Spine Research Society, Aspen Medical Products Isador Lieberman MD, MBA, FRCSC A; Mazor Robotics. B; Mazor Robotics, Stryker Spine, Globus, Misonix, Safe Orthopaedics, Medtronic, SI Bone. D; Mazor Robotics. F; Mazor Robotics,


Adult degenerative scoliosis (ADS) patients exhibit an increased sway within their cone of economy (COE). Greater sway expends more energy while standing when compared to healthy controls. Spinal alignment surgery has been shown to improve SVA and balance.


The purpose of this study is to quantify the extent of change in sway associated with maintaining a balanced posture within the COE, in a group of ADS patients’ pre and post-surgery and compare them to matched non-scoliotic controls.


Thirty-three ADS patients performed a series of functional balance tests a week before and 3 months after surgery. Twenty controls performed the same test on one occasion. Outcome measures were center of mass (COM) and head sway in the sagittal and coronal planes, total sway amount and spine and lower extremity neuromuscular energy expenditure.


ADS patients demonstrated more initial COM (p=0.001) and head (p=0.011) displacements. Post-operatively ADS patients exhibited less COM (p=0.043) and head sway (p=0.050), in comparison to their pre-surgery measures. Post-surgical ADS patients still demonstrated more COM (p=0.002) and head (p=0.012) displacements and increased muscle activity in comparison to non-scoliotic controls. Furthermore, ADS patients increased muscle activity in their Erector Spinae (p=0.008), Gluteus Maximus (p=0.034), and Tibialis Anterior (p=0.018) muscles during one minute standing in comparison to non-scoliotic controls.


This study objectively quantified the patients’ energy expenditure, COE boundaries, COM displacement and amount of sway within the COE during a dynamic balance test before and after surgical intervention in a population of ADS patients. Surgical alignment reduced the amount of sway, reduced the center of mass displacement, and reduced spine and lower extremity energy expenditure in ADS’ patients. In symptomatic pre-operative ADS patients, sagittal sway increased along with greater lumbar spine and lower extremity neuromuscular activity in comparison to a non-scoliotic control. Although surgical alignment improved ADS functional parameters during a dynamic balance test, these parameters approached but did not fully achieve non-scoliotic control parameters when measured 3 months after surgery.