Cervical Pseudoarthrosis and Adjacent Level Disease
This 70 year-old female presented reporting increasing neck and periscapular pain over several years. The patient underwent a C5-C7 ACDF 11 years earlier. Her pain intensified and radiated into the deltoid area following a minor motor vehicle accident 6 months earlier.
On exam, there was some pain with ROM, but otherwise no focal deficits.
Lateral C-spine film shows a broken plate and probable pseudoarthrosis at C5-C6. MRI demonstrates C4-C5 spondylosis with bilateral neural foraminal stenosis (Fig 1). Solid fusion is evident at C6-C7 (Fig. 1).
The whole body bone scan shows high signal in the mid cervical spine (Fig 2).
SPEC imaging showed an area of high metabolic activity at C5-C6 (Figs 3,4).
Pseudoarthrosis C5-C6, progressive spondylosis C4-C5, and bilateral neural foraminal stenosis.
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The patient underwent an ACDF C4-C5 and redo at C5-C6, with explantation of the previous hardware (Fig. 5).
On follow-up, the patient reported significant improvement in neck pain at 3-months, 6-months, and 1-year post-op.
The decision whether to revise a cervical interbody pseudoarthrosis can be difficult. To objectively confirm the diagnosis, a variety of diagnostic tests, in combination, are helpful. We use plain radiography including dynamic films. Broken hardware, gross instability, progressive (even fixed) sagittal imbalance, or translation, are obvious signs of an underlying pseudoarthrosis. CT scans with axial, sagittal, and coronal reconstructions are very helpful to assess the presence of absence of trabecular bone formation across a disc space. Nuclear medicine studies (Bone SPEC scans) can identify areas of markedly increased metabolic activity in contrast to quiescent homeostatic bone.
Perhaps the most difficult part is analyzing the degree of a patient’s pain and its relationship to these potential radiographic findings. Often these patients with pseudoarthrosis lack objective findings on neurological examination. However, in this patient, these studies have confirmed the likely presence of a pseudoarthrosis at C5-C6 and clinically relevant spondylosis at C4-C5.
A posterior approach is reasonable and would avoid the morbidity of anterior re-operation such as swallowing difficulties, risk of esophageal injury, recurrent laryngeal nerve palsy, soft tissue scar formation, and increased neck fullness (as commonly described by patients). The downside of the posterior approach is it is biomechanically inferior to anterior interbody fusion, may involve muscle trauma and atrophy, is more painful than the anterior approach, and may not provide for optimal nerve decompression compared to the anterior approach. The posterior approach may indeed be the best option in patients who already have vocal cord dysfunction on otolaryngological examination, or have swallowing difficulties, or extensive soft tissue scarring.
The advantages of the anterior approach include the ability to remove a broken, and therefore potentially harmful implant; the ability to revise and achieve an interbody fusion at the pseudoarthrotic level while also treating de novo the C4-C5 level; less pain and discomfort compared to a midline posterior cervical approach; and higher success rates for arthrodesis compared to on-lay posterior techniques. Patients should be counseled that re-operation in the anterior cervical region carries higher risk of the aforementioned potential problems (swallowing difficulties, soft tissue scarring, etcetera).
Whether there is adjacent level symptomatic degeneration or not, our treatment of cervical pseudoathrosis has been most successful using the technique described by Dr. Highsmith. In our practice, we have found and reported in the peer-reviewed literature that use of BMP in either allograft bone or synthetic spacers results in very high rates of successful arthrodesis. Removal of indwelling instrumentation is usually technically possible, though challenging, in cases of dense prevertebral scarring. In placing a new plate at the previously operated level, we try to use a new screw entry point and trajectory in order to achieve maximal screw purchase. This may require the use of a slightly longer, or shorter plate.
Lastly, it will be interesting in the years to come to see if cervical arthroplasty will become a useful treatment of adjacent level degeneration. It is unlikely that arthroplasty will be a suitable technology for the treatment of a pseudoarthrosis, as there is likely to be significant stiffness, facet arthropathy, and other pathology for which successful arthrodesis would provide the best clinical result.