Functional Balance Testing in Cervical Spondylotic Myelopathy Patients

Ram Haddas, PhD; Isador Lieberman, MD; Akwasi Boah, MD; Raj Arakal, MD; Theodore Belanger, MD; Kevin L. Ju, MD


Spine. 2019;44(2):103-109. 

In This Article

Abstract and Introduction


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


Cervical spondylotic myelopathy (CSM) is a neurologic condition resulting from spinal cord compression caused by degenerative narrowing of the cervical spinal canal.[1–3] CSM commonly presents after the age of 50 years, but the age of onset can vary depending on the degree of congenital spinal canal narrowing and extent of spondylotic changes.[1] Although CSM can follow various courses, patients commonly exhibit a slow, progressive stepwise decline in their neurological function. Difficulty with balance is one of the most common manifestations of CSM.

Numerous musculoskeletal and neurological disorders, including CSM, result in altered balance.[4,5] Clinicians and rehabilitation experts depend on a firm understanding of the basic mechanics of normal locomotion to determine the relationship between the patient's altered balance and function and the impairments of discrete segments of the musculoskeletal system. Likewise, spine practitioners should also be familiar with these same principles.[6] When one's balance and function are detrimentally altered, it can have a profound effect on their quality of life and activities of daily living.[4,5] Quantifying and analyzing the specific balance alterations of patients with CSM not only provides a richer biomechanical understanding of normal and pathological balance but also provides specific parameters that can be used in evaluating the severity of balance disturbance and postoperative recovery and rehabilitation. By recognizing these individual components and overall goals, clinicians can examine the specific sequence of muscle activity and precise movement of limb segments to gain an appreciation for how specific musculoskeletal pathology affects a patent's mobility and balance.

Upright stance and body stability depends on the vestibular, visual, and somatosensory systems.[7] These systems contribute to the maintenance of postural control. The spinal cord, particularly the dorsal column, is an integral part of the somatosensory system.[8] The dorsal columns relay the position and vibration sensations as well as play an important role in maintaining postural stability and conveying sensory information such as deep sensations to the lower limbs.[9] When the dorsal column of the spinal cord is compressed, the functions of vibration sense, deep sensibility, and joint position sense are lost.[9] CSM patients were found to have impaired knee proprioception when using electrogoniometer.[10] A damaged spinal cord causes impaired body balance because of proprioceptive loss, and patients develop ataxia in the lower limbs.[10–13]

Jean Dubousset[14] first introduced the concept of the cone of economy and balance (COE) in 1994. The COE refers to a stable region of standing posture. The fundamental assumption is that swaying outside one's individual cone challenges the balance mechanisms and expends critical energy (Figure 1).[14] Balance is defined as the ability of the human body to maintain its center of mass 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.[15] Balance efficiency is defined as the ability of the patients to maintain their COM within the COE with minimal sway and neuromuscular energy expenditure.[15,16] Maintenance of balance requires coordination between the sensorineural and musculoskeletal systems. Very few studies have looked at functional balance in CSM patients. These studies used a stabilometer to measure center of gravity.[17,18] During a 30 seconds balance test with closed eyes, CSM patients swayed significantly more and had greater postural instability than healthy controls (HCs).[17,18] Neither of those studies reported on neuromuscular activity during a functional balance test. Haddas and Lieberman[15] were the first to introduce a method to objectively quantify the COE and neuromuscular energy expenditure during a dynamic balance test.

Figure 1.

Cone of economy as described by Dubousset.12,14

Although there are only a few papers investigating balance in CSM patients using limited tools, to our best knowledge, no one has attempted to quantify COE and neuromuscular activity during a dynamic balance test in untreated CSM patients. Therefore, the purpose of this study is to quantify the difference in sway associated with maintaining a balanced posture within the COE in a group of CSM patients, and also compare them to matched HCs.