Can Prophylactic Foraminotomy Prevent C5 Palsy

Introduction:

C5 palsy (C5P) is a well-known, although rare complication of cervical spine decompression
surgery.1,2 In severe forms, C5P causes debilitating upper extremity weakness involving the
deltoids and/or biceps brachii muscles, ultimately diminishing these patients' quality of
life.3 Furthermore, about half of patients with C5P present with sensory deficits and/or
intractable pain in addition to the muscle weakness.5 Fortunately, almost all cases of C5P
present unilaterally. The deficit is typically quantified and diagnosed using each patient's
manual muscle test (MMT) score (rating 0-5). The American Medical Association impairment
rating guide grades the MMT as follows: Grade 0 = no perceptible muscle contraction; Grade 1
= muscle contraction palpable, but no motion; Grade 2 = motion of the part only with gravity
reduced; Grade 3 = muscle can hold the part in the test position against gravity alone; Grade
4 = patient can move the part through the full range of active motion against "some"
resistance; Grade 5 = patient can move the part through the full active range of motion
against "full" resistance. C5P is defined as: a reduction of at least 1 in deltoid and/or
biceps brachii scores compared to preoperative scores, without any deterioration of
myelopathic symptoms.5

Although a uniform understanding of the etiology and mechanism of C5P is not yet established,
certain hypotheses have gained recognition. One prominent hypothesis, called the tethering
phenomenon, suggests that following decompression, posterior shift of the cord produces
traction on the nerve root resulting in a nerve root lesion. Other, less agreed upon
hypotheses include: inadvertent injury to the nerve root during surgery, spinal cord
ischemia, segmental spinal cord disorder, and reperfusion injury of the spinal cord. As the
pathogenesis of C5P is uncovered, concerted efforts to minimize the incidence of this
unfortunate complication have been undertaken.5

Prophylactic bilateral foraminotomy at the C5 level during cervical decompression surgery has
been studied recently with the hope that it will minimize the risk of developing a C5 nerve
root palsy postoperatively.6,7,8 Although the current literature provides some support for
this claim, there are insufficient data establishing this technique as a proven measure to
reduce the incidence of C5P. In the present study, we seek to evaluate the effect of
bilateral foraminotomy on postoperative C5P incidence rates.

Background:

Komagata et al.7 performed a retrospective study to investigate preoperative risk factors
that may cause postoperative C5P. The study included 305 cases of cervical expansive
laminoplasty performed for spondylotic myelopathy or ossification of the posterior
longitudinal ligament. No specific risk factors were found to be associated with higher
incidence of C5P. However, bilateral partial foraminotomy was found to be effective in
preventing C5P, with C5P occurring in 1 gutter (0.6%) in the foraminotomy group and in 12
gutters (4.0%) in the non-foraminotomy group (p<0.05).

Interestingly, preoperative anatomical measurements have been suggested to correlate with
risk of developing C5P. Lubelski et al.9 performed a retrospective study to determine whether
postoperative C5P can be predicted from preoperative antero-posterior diameter (APD),
foraminal diameter (FD), and/or cord-lamina angle (CLA). 98 consecutive patients who
underwent either anterior or posterior decompression surgery at C4-C5 for spondylotic
myelopathy were analyzed. It was found that for every 1-mm increase in APD and FD, the odds
of developing palsy decrease 69% (p<0.01) and decrease 98% (p<0.01), respectively. In
contrast, for every 1-degree increase in CLA, the odds of developing palsy increase by 43%
(p<0.01). Furthermore, Lubelski et al. used these three preoperative parameters - APD, FD,
and CLA - to create a nomogram that predicts the probability that a patient will develop C5
palsy. This nomogram will be investigated for validity in the current study.

Preliminary Studies:

In addition to the study mentioned above, several authors have demonstrated the efficacy of
prophylactic C5 foraminotomy during laminoplasty to prevent postoperative C5P. Sasai et al.7
performed the first prospective study using microcervical foraminotomy (MCF) during cervical
laminoplasty as a prophylactic measure to prevent C5P. MCF was used selectively in patients
with EMG abnormalities (Group A), and decreased the incidence of postoperative C5P compared
to a group that did not have EMG studies or MCF performed (Group B). No patients in Group A
and three patients in Group B experienced postoperative C5P (0% vs. 8.1%; p=0.035). No
adverse outcomes were reported in this study. Based on these results, the authors suggested
preexisting subclinical C5 root compression as a cause of C5P after posterior cervical
decompression for myelopathy.

In 2012, Katsumi et al.5 performed a prospective, non-randomized study analyzing whether
bilateral C5 foraminotomy can prevent C5P after open-door laminoplasty. Prophylactic
bilateral foraminotomy done on 141 consecutive patients was seen to significantly decrease
the incidence of postoperative C5P compared to a control group (1.4% and 6.4%, respectively;
p<0.05). These results support the hypothesis that preoperative C5 foraminal stenosis is
associated with a higher risk of C5P. Furthermore, these findings are consistent with the
tethering phenomenon hypothesis regarding the pathomechanism of C5P. The only two patients in
this study who developed C5P after undergoing prophylactic foraminotomy did not receive
meticulous decompression of the C5 nerve root, leaving residual superior articular process.
No patients in either group experienced postoperative infection or durotomy. Although the
average operative time was longer in the foraminotomy group (102 minutes and 129 minutes,
p<0.01), there was no significant difference in intraoperative blood loss between the two
groups. In order to better elucidate the true effect of bilateral C5 foraminotomy, the
procedure must be performed uniformly and randomized to all patients included.

With the current literature providing some evidence to suggest the efficacy of prophylactic
bilateral C5 foraminotomies to reduce the incidence of postoperative C5P, there remains a
need for a randomized, prospective study to investigate foraminotomy as a potentially
beneficial procedure to all patients undergoing cervical decompression.

Significance of Proposed Study Bilateral foraminotomy has been correlated with a reduced risk
of developing C5P following cervical decompression surgery, but an identical foraminotomy
procedure has never been applied in a randomized manner to all qualifying patients in a
study.5,6,7 Additionally, prophylactic foraminotomy has only been prospectively studied
during laminoplasty. In the proposed study, bilateral foraminotomy will be randomized to
patients receiving cervical decompression surgery (laminoplasty, laminectomy, fusion).
Subsequently, incidence of C5P as well as other surgical complications will be monitored to
determine efficacy of prophylactic C5 bilateral foraminotomy during cervical decompression.

Research Procedures:

This is a multicenter randomized trial, including the following sites: Cleveland Clinic,
Columbia University Medical Center, and University of Southern California Spine Center.
Patients undergoing cervical decompression surgery will be consented and enrolled if they
meet the inclusion and exclusion criteria detailed above. The EPIC Electronic Medical Record
database will be queried to retrieve medical records consistent with the study sample and to
determine all cervical decompression surgeries. Patients' sex, race, date of birth, BMI,
medical comorbidities, medications, history of spinal trauma or surgical intervention,
smoking status/ history, spinal levels involved, type of surgery, operating surgeon, length
of hospital stay, operative time, blood loss, in-hospital complications noted and patient
complications following surgery will be obtained. Additionally, preoperative anteroposterior
diameter of the spinal canal at C4-C5, ipsilateral foraminal diameter at C4-C5, and the
morphological relationship between the spinal cord and the ipsilateral lamina (cord-lamina
angle) will be obtained. Clinical outcome measures will be analyzed using standard
statistical methods.

Intervention:

In addition to the decompression technique indicated directly for treatment of cervical
myelopathy, bilateral keyhole foraminotomies will be done prophylactically in an attempt to
minimize postoperative complications, specifically C5 Palsy. Under microscopic or loop
magnification, a high-speed burr is used to perform the foraminotomy. The keyhole
foraminotomy begins at the lamina-facet junction, with careful consideration of the amount of
facet resection. Typically, only the medial one third is drilled. Then a 1- or 2-mm Kerrison
punch can be carefully placed over the nerve root and then used to undercut the facet,
ensuring that the spine is not destabilized by the foraminotomy. The amount of facet
resection must not exceed 50% in order to preserve spine stability.

Consent:

All patients will be enrolled after completion of the attached informed consent form. All
patients' information in this prospective study will be treated as confidential. This study
involves no risk to the physician, or OR staff. A cervical foraminotomy is a common, short
procedure (e.g. 5 minutes) that involves making more room for a cervical nerve root as it
exits the spinal column. It is a procedure that all surgeons perform routinely, and in no way
put the patient at risk for spine structural problems. Similarly, it does not impart
additional measurable risk to the patient of neurological injury or infection over that risk
already being incurred by the patient for the index procedure. Patients who are under the age
of 18 will be excluded for previously mentioned scientific reasons. Women and minorities are
expected to participate proportionally to their numbers diagnosed with cervical myelopathy.

Inclusion Criteria:

- Cleveland Clinic patients who have been diagnosed with cervical myelopathy, without
radiculopathy, and will undergo posterior cervical decompression involving the C4-C5
interspace between 2016 and 2018. This includes patients undergoing cervical
laminoplasty and cervical laminectomy and fusion.

Exclusion Criteria:

- Any patient younger than 18 years of age will not be included on the basis of skeletal
immaturity. Patients with C5 radiculopathy - defined in our study as the existence of
preoperative deltoid muscle weakness in grade 3 or less by MMT - will be excluded. Any
patients who have undergone previous cervical spine surgery, or who have any spinal
malignancy, trauma or infection will be excluded in order to eliminate the confounding
effect of multiple surgical interventions.