Gait in Adult Patients With Cervical Spondylotic Myelopathy

Cervical spondylotic myelopathy (CSM) is a neurologic condition resulting from spinal cord
compression caused by degenerative narrowing of the cervical spinal canal. CSM is most common
after the age of 50 years, but the age of onset is variable depending on the degree of
congenital spinal canal narrowing. Progressive degenerative changes in the cervical spine,
such as disc bulges or herniations, facet hypertrophy, ligamentum flavum thickening, and
degenerative vertebral spondylolisthesis, can all contribute to progressive spinal cord
compression. The end result is chronic compression of the spinal cord and/or nerve roots
leading to impaired blood flow, which can result in frank damage within the spinal cord
itself. CSM is characterized by a wide variety of clinical presentations, which can include
neck pain, numbness or weakness in the extremities, hand clumsiness, and, classically, gait
disturbances. This typically manifests as difficulty with balance, but patients with more
advanced myelopathy can also develop a stiff, spastic gait.

Surgical treatment of CSM revolves around decompressing the spinal cord, either with or
without concurrent fusion. Many surgical strategies have been proposed. Anterior surgical
approaches include anterior cervical discectomy and fusion or anterior corpectomy and fusion.
Posterior surgical approaches include laminectomy with or without fusion, or laminoplasty.
The choice of surgical approach is specific to each patient based upon the extent and
location of the pathology, the presence or absence of deformity or spinal instability, the
sagittal alignment of the spine, the presence or absence of ossification of the posterior
longitudinal ligament (OPLL), as well as other patient co-morbidity factors and surgeon
preference. While there may be some debate as to when patients with radiographic cervical
stenosis should undergo decompressive surgery, most surgeons would agree on surgery for
patients with moderate or severe clinical myelopathy.

Altered gait is frequently seen with CSM, and has been reported to be improved by surgical
intervention. A stiff or spastic gait is also characteristic of CSM in its later stages. Many
clinical studies have determined that patients with CSM have a slower gait speed, prolonged
double support duration, and reduced cadence compared to healthy controls.Previous studies
also identified reduced knee flexion during swing in the early stages of the disease, and, in
more severe cases, decreased ankle plantar flexion at the terminal stance and reduced knee
flexion during loading response.

Upright stance and body stability depends on the vestibular, visual, and somatosensory
systems.These systems contribute to the maintenance of postural control. The spinal cord,
particularly the dorsal column, is an integral part of the somatosensory system.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.When the dorsal column of the spinal cord is compressed, the functions of
vibration sense, deep sensibility, and joint position sense are lost. CSM patients were found
to have impaired knee proprioception when using electrogoniometer.22 A damaged spinal cord
causes impaired body balance because of proprioceptive loss, and patients develop ataxia in
the lower limbs.

Jean Dubousset, 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. 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. Balance
efficiency is defined as the ability of the patients to maintain their COM within the COE
with minimal sway and energy expenditure.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.
During a 30 seconds balance test with closed eyes, CSM patients swayed significantly more and
had greater postural instability compared to healthy controls. Neither of those studies
reported on neuromuscular activity during a functional balance test. Haddas et al.was first
to introduce a method to objectively quantify the COE and neuromuscular energy expenditure
during a dynamic balance test.

There is very little literature investigating the effect of surgical intervention on a CSM
patient's balance and gait using human motion analysis both before and after surgery. In
fact, there have not been any studies examining how surgical intervention for CSM can improve
patients' balance and gait utilizing objective neuromuscular data as well as full body
kinematic analysis. Additionally, none of the previous studies have been able to validate
self-reported pain and functional outcome measures utilizing a human motion capture system
and EMG.

This study explores the effect of CSM on human balance and gait and will utilize kinematic
balance and gait analyses to examine the dynamic range of motion of the spine and lower
extremities, along with neuromuscular data from surface EMG to precisely define the timing
and degree of spine and lower extremity muscle activation and peak activity, as well as
measurements of ground reaction forces throughout the gait cycle. All of this will be
compared pre- and post-operatively and also with a healthy control group in order to
determine the extent to which CSM affects the biomechanics of and neuromuscular control
during balance and gait and how this changes after surgical intervention. We will also be
able to correlate these objective measures with patient self-reported pain and function based
on commonly used outcome instruments.

In summary, the purpose of this study is to explore the level of functional compromise, both
objectively and with patient-reported outcome measures, in patients with CSM and to quantify
the possible benefit of surgical intervention on the biomechanics and neuromuscular control
of the spine and lower extremities as evaluated by balance and gait analyses using dynamic
EMG, video motion capture, force plate analysis, and validated patient-reported outcome
metrics.

Inclusion Criteria:

1. Age 30 years and older

2. Diagnosis of CSM with correlative imaging studies (MRI or CT-myelogram)

3. Able to ambulate without assistance and stand without assistance with participant eyes
open for a minimum of 10 seconds

4. Able and willing to attend and perform the activities described in the informed
consent within the boundaries of the timelines set forth for pre-, and post-operative
follow-up

Exclusion Criteria:

1. History of prior attempt at fusion (successful or not) at the indicated levels,
(history of one level fusion is not an exclusion)

2. Major lower extremity surgery or previous injury that may affect gait (a successful
total joint replacement is not an exclusion)

3. BMI higher than 35

4. Neurological disorder (beside cervical spondylotic myelopathy), diabetic neuropathy or
other disease that impairs the patient's ability to ambulate or stand without
assistance

5. Usage of blood thinners

6. Pregnant or wishing to become pregnant during the study