Study design: A prospective cohort study.
Objective: The aim of this study was to quantify the amount of sway associated with maintaining a balanced posture in a group of untreated cervical spondylotic myelopathy (CSM) patients.
Summary of background data: 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. Sway is the movement of the COM in the horizontal plane when a person is standing in a static position. CSM patients have impaired body balance and proprioceptive loss.
Methods: Thirty-two CSM patients performed a series of functional balance tests a week before surgery. Sixteen healthy controls (HCs) performed a similar balance test. Patients are instructed to stand erect with feet together and eyes opened in their self-perceived balanced and natural position for a full minute. All test subjects were fitted to a full-body reflective markers set and surface electromyography (EMG).
Results: CSM patients had more COM sway in the anterior-posterior (CSM: 2.87 cm vs. C: 0.74 cm; P = 0.023), right-left (CSM: 5.16 cm vs. C: 2.51 cm; P = 0.003) directions as well as head sway (anterior-posterior - CSM: 2.17 cm vs. C: 0.82 cm; P = 0.010 and right-left - CSM: 3.66 cm vs. C: 1.69 cm; P = 0.044), more COM (CSM: 44.72 cm vs. HC: 19.26 cm, p = 0.001), and head (Pre: 37.87 cm vs. C: 19.93 cm, P = 0.001) total sway in comparison to controls. CSM patients utilized significantly more muscle activity to maintain static standing, evidenced by the increased trunk and lower extremity muscle activity (multifidus, erector spinae, rectus femoris, and tibialis anterior, P < 0.050) during 1-minute standing.
Conclusion: In symptomatic CSM patients, COM and head total sway were significantly greater than controls. Individuals with CSM exhibit more trunk and lower extremity muscle activity, and thus expend more neuromuscular energy to maintain a balanced, static standing posture. This study is the first effort to evaluate global balance as a dynamic process in this patient population.
Level of evidence: 3.