Lightning Podiums: Spinal Potpourri - 803B

Presented by: R. Haddas

Author(s):

R. Haddas(1), I. Lieberman(2)

(1) Texas Back Institute, Research Foundation, Plano, TX, United States
(2) Texas Back Institute, Plano, TX, United States

Abstract

Study Design: A prospective cohort study.

Introduction: Maintenance of balance requires coordination between the sensorineural and musculoskeletal systems. Balance is defined as the ability of the human body to maintain its center of mass (COM) within the base of support with minimal postural sway. Adult degenerative scoliosis (ADS) patients exhibit a variety of postural changes involving the spine, pelvis and lower extremities, in their effort to compensate for the altered posture. ADS patients comprise a variety of conditions that affect the normal spinopelvic alignment in the coronal and or sagittal planes. The way those patient compensates for truncal imbalance may be variable and may depend on other constitutional factors such as age, neuromuscular condition, and BMI. In general though, the brain, through the righting reflex, will sacrifice focal alignment to optimize global balance within Dubousset's "Cone of Economy". To our best knowledge, no one has attempted to quantify the energy expenditure associated with sway during a functional balance test in ADS patients test before and after spinal re-alignment surgery.

Objective: To compare spine and lower extremity neuromuscular activity in a group of ADS patients before and after surgical intervention.

Methods: Fourteen ADS patients performed a series of functional balance tests a week before (Pre) and 3 months after (Post) surgery. The functional balance test was similar to a Romberg´s test in which the patients are required to stand erect with feet together and eyes opened in their self-perceived balanced and natural position for a full minute. Surface EMG electrodes were placed on the skin overlying the External Oblique (EO), Multifidus (Mf) at the level of L5, Erector Spinae (ES) at the level of L1, Gluteus Maximus (GM), Rectus Femoris (RF), Semitendinosus (ST), Tibialis Anterior (TA), and Medial Gastrocnemius (MG). Spine and lower extremity integrated electromyography (iEMG) were measured. iEMG activity is a graphic representation of the sum total EMG activity over a defined period of time. Repeated measurement ANOVA was.

Results: Our results show that surgical intervention in ADS patients reduced spine and lower extremity energy expenditure when they attempt to maintain static standing. Post-surgery ADS patients expended a statistically significantly decrease in muscle activity in their ES (Pre: 30.70 mV vs. Post: 8.67 mV; p=0.020), Mf (Pre: 25.87 mV vs. Post: 17.01 mV; p=0.048), and RF (Pre: 27.82 mV vs. Post: 17.50 mV; p=0.050) muscles during one minute standing in comparison to the pre surgery condition. With higher values in integrated EMG, ADS patients seem to expend less energy during a simple standing task after a spinal alignment surgery. Although they were not statistically significant, there was a trend toward smaller muscle activity in the rest of the tested muscles in ADS patients after surgical intervention.

Conclusions: We observed that surgical intervention in ADS patients reduced muscle activity particularly in the ES, Mf and RF muscles, and thus they expend less energy to maintain static standing or balance in comparison to their pre surgical condition. This may be due to the correction of the spine curve structure compounded by the biomechanical forces associated with sagittal balance. This study provides the first effort to evaluate neuromuscular energy expenditure as a dynamic test.