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    • Rationale Anterior cervical discectomy and fusion ACDF has

    2018-10-29

    Rationale Anterior cervical discectomy and fusion (ACDF) has been accepted as the gold standard of surgical management for cervical spondylosis and disc disease causing radiculopathy or myelopathy. High patient-satisfaction scores and high arthrodesis rates associated with ACDF have been reported in the literature. However, there is always the concern of loss of segmental motion at the index level of the intervertebral disc after ACDF. Furthermore, adjacent segment disease (ASD) has been reported after cervical fusion at a rate of 2.9% per year. This development of ASD may also cause symptoms that require re-operations. A study from Taiwan, covering 19,385 patients who underwent ACDF over a period of 11 years, estimated the incidence of ASD that required a repeat ACDF operation to be 0.8% annually. Although the actual etiology of re-operation for ASD after ACDF is still uncertain, it can be attributed to the natural course of spondylosis or a consequence of increased load after neighboring arthrodesis. Wu et al reported that, in Taiwan, after ACDF, a considerable portion (i.e., 5.6%) of patients had a second ACDF during the following 10 years. In recent years, there has been an emerging option of cervical total disc replacement (CTDR) for surgical management of disc disease in the cervical spine. The development of CTDR intends to preserve motion and reduce ASD. By elastase inhibitor of an artificial disc instead of a bone graft after cervical discectomy, the technology of CTDR allows preservation of spinal motion at the indexed intervertebral disc (Fig. 1). In theory, maintaining the segmental motion at the indexed disc level translates little workload to the neighboring discs and might thus reduce the incidence of ASD. From reports of short- to mid-term (i.e., 2–5 years) follow-up, the average range of motion at the index level was successfully preserved at approximately 8° after CTDR. However, the reduction in ASD or avoidance of a second surgical procedure for ASD was uncertain in these reports. Whether ASD could be ameliorated still needs data from long-term follow-up to validate.
    Clinical trials There are several prospective, randomized, controlled, multicenter clinical trials, approved by the U.S. Food and Drug Administration (FDA) investigational device exemption (IDE), comparing CTDR with ACDF for single-level cervical disc disease with more than 2–5 years of follow-up. These trials have analyzed outcomes of a number of artificial disc devices (e.g., BRYAN, Prestige ST, ProDisc-C, and Kineflex C) with a comparison to instrumented ACDF in the management of one-level cervical disc disease. All these trials have applied similar inclusion and exclusion criteria, used similar radiological and clinical outcome measurements, and had their data published in major journals.
    Indications The inclusion criteria of the aforementioned FDA-IDE trials for CTDR were adult patients with single-level symptomatic cervical spondylosis and disc herniation at C3–C7 levels chromatin presented with intractable radiculopathy, myelopathy, or neck pain. The best candidates for CTDR should be young patients who have radiculopathy caused by herniated disc with competent facet joints. In current practice, the generally accepted indications for CTDR are one- or two-level cervical disc herniation, degenerative disc disease, and spondylosis (Table 1). The relative contraindications for CTDR are kyphotic deformity, severe spondylosis with incompetent facet joints, trauma-related ligamentous or facet injury, osteoporosis, and cervical ankylosis. In addition, there are reports analyzing the outcomes of patients undergoing CTDR for slightly different indications, failing to demonstrate significant differences. Although the inclusion criteria in the published FDA-IDE trials included patients with myelopathy, the actual effect of CTDR on cervical spondylotic myelopathy remains uncertain. Furthermore, several clinical series revealed the efficacy of CTDR in multilevel cervical spondylosis or disc disease. However, only scarce reports have compared multilevel CTDR with ACDF.