Cervical spondylotic myelopathy: the relevance of the spinal cord back shift after posterior multilevel decompression. A systematic review

Vincenzo Denaro, Umile Giuseppe Longo, Alessandra Berton, Giuseppe Salvatore, Luca Denaro

Spinal cord back shift has been considered the desired end point of posterior decompression procedures for cervical spondylotic myelopathy (CSM). However, the association with postoperative outcomes has not been definitively demonstrated. The aim of this review is to obtain an overview of the current knowledge on the spinal back shift after posterior decompression to clarify the main controversial aspects and provide recommendations for further studies on the subject. A comprehensive quantitative review of the literature was performed. Bibliographic databases were searched using the following keywords: spinal cord drift, spinal cord shift, CSM, ossification of posterior longitudinal ligament, posterior decompression, laminoplasty, laminectomy and fusion. Twelve eligible studies were included. The authors measured the spinal cord back shift in different ways, using the posterior edge, the center or the anterior margin of the spinal cord as reference points. Six studies analyzed the correlation between the spinal cord back shift and the recovery rate, but their results were discordant. The correlation between the posterior cord migration and cervical alignment was not confirmed in all studies. There is a need for a consensus on the best way to measure the spinal cord back shift. The action of multiple factors on spinal cord back shift can explain the difference in the results collected from the studies. We recommend further studies to clarify the behavior of the spinal cord after posterior decompression and its clinical meaning.