Cervical Spondylosis
Cervical spondylosis involves a constellation of chronic degenerative changes that culminate in narrowing of the spinal canal and neural foramen. Due to natural loss of disc height, facet arthropathy, ligamentum flavum hypertrophy and buckling, osteophyte formation, and occasionally ossification of the posterior longitudinal ligament, there is a gradual reduction of available space for the spinal cord throughout the spinal canal including the cervical spine.
Due to the heterogeneity of degenerative processes causing spondylosis, it is not always clear whether decompressive surgery can be best and most safely accomplished from an anterior approach or a posterior approach. This dilemma has been studied and will be summarized here.
Discussion
The optimal method of surgical decompression for cervical spondylosis has been studied using several prospective cohorts and summarized via meta-analysis. In a small non-randomized prospective trial, Ghogawala et al. (2011a) compared ventral to dorsal decompression and found that both groups demonstrated improvements in disease-specific disability (modified Japanese Orthopedic Association scale and Neck Disability Index) and quality of life compared to baseline. Although improvements in each group were similar, ventral decompression resulted in better change in Neck Disability Index and quality of life measures compared to dorsal decompression. This result is difficult to interpret due to worse neurological status at baseline in the dorsal group as well as small sample size.
Among individuals receiving an anterior/ventral approach for multilevel spondylosis, there are several accepted options for reconstruction/stabilization of the spinal column following decompression. These include adjacent discectomies with fusion, multilevel corpectomy with fusion, or a hybrid combination. The outcomes of these, and their complication profiles, have recently been studied. Liu et al. (2009) report a case control study, again with small numbers, suggesting equivalent and satisfactory clinical outcomes between multilevel corpectomy and a hybrid approach. In an analysis of complication rates, Liu et al. (2012b) reported that each of the three anterior approaches showed no difference in neurological or quality of life outcome, despite the multilevel corpectomy group having a higher overall rate of complications, consisting mainly of graft migration, hoarseness, and dysphagia, most of which self-resolved. Among all comers, the approximate rate of surgical complication from anterior decompression was 22%. Also, of note, the more cranially-oriented the construct, the higher rate of postoperative complications, although no differences in neurologic or quality of life outcome were reported.
A similar syndrome to cervical spondylotic myelopathy is cervical spondylotic amytrophy, which describes a pure-motor syndrome thought to be secondary to spondylosis. In this population of individuals, anterior decompression has been described (Kong et al. 2015). In a small series of 40 surgically treated individuals, 75% of individuals experienced an improvement after surgery as defined by manual muscle testing, although it is unclear what threshold constitutes a clinically important difference (Kong et al. 2015).
Finally, Luo et al. (2015b) performed a meta-analysis comparing anterior-vs-posterior surgical decompressive approaches. Ten studies were included and consisted of a mix of non-randomized prospective and retrospective studies. Although the anterior approach shows modest evidence of better neurological function postoperatively, the modified Japanese Orthopedic Association score and overall clinical outcome generally was deemed clinically nonsignificant between the two groups. This may be due to the higher complication in the anterior approach, especially when treating multilevel disease. Otherwise, statistical equivalence was reported in terms of modified Japanese Orthopedic Association score, neurological recovery rate, operative blood loss, and length of hospital stay.
Conclusion
There is level 2 evidence (based on one prospective controlled trial: Ghogawala et al. 2011) that anterior decompression for cervical spondylosis myelopathy may have better neurological recovery, but is also associated with higher complication rates, when compared to posterior decompression. There is no difference in disease-specific disability or quality of life between these two groups.
There is level 3 evidence (based on one case control, one pre-post, and one case series (Liu et al. 2009; Kong et al. 2015; Liu et al. 2012) that many different reconstructive options for anterior decompression have been established; however, they are not discernible in terms of quality of life or clinical outcomes.
