The goal of this study is to evaluate children and adolescents with idiopathic scoliosis who are undergoing spinal fusion using motion analysis, balance, and outcome questionnaires. Little research has been done to evaluate how different fusion levels impact walking patterns, range of motion, posture and balance following spine instrumentation in children with idiopathic scoliosis. Debate still continues whether posterior spinal instrumentation with the last instrumented vertebra at or above Lumbar 3 (L3) will provide sufficient spine correction, greater motion, and better posture and balance when compared to a child with instrumentation at Lumbar 4 (L4). Furthermore, how does the spine fusion endpoint (last instrumented vertebra) impact quality of life, participation, and impairment in children and adolescents with idiopathic scoliosis and how do they compare to healthy age-matched peers. The goal of this study is to compare these two end points using gait analysis, postural stability, and outcome tools with the hopes of providing better clinical care to children with idiopathic scoliosis.

The study population will include sixty (60) children with idiopathic scoliosis who will undergo spine surgery and sixty (60) developing children "Control Group". Scoliosis patients will undergo a period of testing which requires three visits: pre-operative evaluation, one-year post-operative evaluation, and two-year post-operative evaluation. The Control Group will require one initial assessment. A total of 240 evaluations will be performed over a three-year period. We will evaluate the correlation among outcome tools and quantitative measures in order to determine how these instruments can be used more effectively for better treatment. Subjects and their parents will be fully informed of the nature of the study as well as the potential risk involved and sign the appropriate consent form. The study will be reviewed by the IRB and include HIPAA compliance. This will be accomplished during testing at the Shriners Hospital for Children- Chicago Motion Analysis Lab. All possible steps will be taken to assure the safety and convenience of the study participants. All subjects will be evaluated using clinical outcome tools (PODCI, SF-36) and will undergo quantitative 3-D motion analysis and postural stability assessment. Quantitative 3-D gait analysis will be done with our 14-camera Motion Capture system and passive reflective markers (Figure 3). Motion analysis will be performed with each subject walking at a comfortable and natural speed on the laboratory walkway. Passive markers will be attached to anatomic landmarks in standardized locations using double-backed tape. Marker coordinate data will be used to determine range of motion and joint angles.

Four forceplates will be used to measure kinetic data and static balance. Postural stability testing will be performed on all subjects (Figure 4). We will evaluate responses to dynamic stability challenges that investigates motor and sensory control and adaptation to perturbations. Static (quiet standing) postural stability tests will be done on all subjects. A licensed physical therapist (PT) will perform the exam following the protocol of the Shriners Hospital for Children's motion lab.

Inclusion Criteria:

• idiopathic scoliosis
• between the ages of 10 - 20
• need a spine fusion at L4 or above
• can walk on your own
• have not had surgery on spine before

Exclusion Criteria:

• pregnant

Adolescents with idiopathic scoliosis that have a Cobb angle greater than 50 degrees.