John G DeVine, MD
Department of Orthopaedic Surgery
Eisenhower Army Medical Center
Ft Gordon, GA, USA
Melloh and Barz describe an interesting case of recurrent cervicobrachialgia after
a 2-year symptom-free period. The patient had undergone a two-level anterior cervical
discectomy with a fusion at the C5/6 level and an arthroplasty at the C6/7 level.
The initial work-up included cervical x-rays and magnetic resonance imaging (MRI)
including STIR sequences that revealed no obvious pathological findings. No further
imaging was obtained at that time. As his symptoms progressed over the next 6 months,
a repeated cervical MRI was obtained revealing metastatic lesions of the fourth and
fifth cervical vertebrae with extension of the tumor into the canal. Eventual diagnosis
was made after thoracic computed tomography (CT) revealed the origin of the metastasis
to be small cell bronchial carcinoma.
This case is unique in that the etiology of the recurrent cervicobrachialgia was metastasis.
The authors point out that there is only one other reported case in the literature
[1]. However, this is not an uncommon clinical scenario. In addition to a medical history
and physical examination, first-line imaging should include x-ray evaluation and MRI.
The clarity of MRI after cervical arthroplasty has been reported. Titanium devices
allow for satisfactory imaging of the adjacent and index levels, but non-titanium
devices (cobalt-chrome-molybdenum alloys) create significant image distortion, preventing
accurate imaging at the index and adjacent levels [2]. More recently, it has been demonstrated that magnet strength affects the artifact
from cobalt-chrome alloys. Using a lower strength magnet, such as the 0.2 Tesla magnet
found in many of the open scanners, the reduction in artifact allows for adjacent
segment imaging without a significant reduction in quality [3]. However, the index levels are still significantly distorted.
In cases when symptoms persist without an obvious explanation using MRI-myelography
followed by CT-myelogram is the imaging modality of choice. The image distortion can
be minimized, while allowing better visualization of the vertebral morphology, and
earlier detection of trabecular destruction in the case of metastasis. Additionally,
the presence of neural compression can be appreciated centrally and in the proximal
nerve roots at every level, including the index level after arthroplasty.
Last, other imaging modalities can be used to detect the presence of occult metastasis
in the setting of disc arthroplasty when the index of suspicion is high on the differential,
or if there is already a diagnosis of malignancy and staging is required. Technetium-99m
bone scan is useful to identify areas of amplified metabolic activity and has a high
sensitivity for detecting lesions. Positron emission tomography uses fluorodeoxyglucose
to define sites of increased metabolic activity and is more sensitive and specific
in detecting bone metastasis.
As Melloh and Barz make clear, in cases when no obvious pathology is identified in
the initial MRI in patients presenting with recurrent symptoms after disc arthroplasty,
interdisciplinary diagnostics may be required. In addition to basic diagnostic tests,
such as erythrocyte sedimentation rate and C-reactive protein, x-rays and electrocardiogram,
I would also recommend CT-myelogram in the setting of a preexisting disc arthroplasty.
