After posterior cervical arthrodesis, many problems can arise, including adjacent segment degeneration and the related adjacent segment disease (ASD). As indicated by studies on the causes of ASD, posterior cervical arthrodesis can produce biomechanical and kinematic changes in adjacent unfused segments due to inappropriate forces. Several studies have been conducted to determine the appropriate lowest instrumented vertebra, specifically regarding whether to cross the cervicothoracic junction via extension of long-segment posterior cervical fusion. We searched for relevant articles in electronic databases including PubMed, the Cochrane Registry, Embase, and Ovid. Five meta-analyses were reviewed on this topic. Among these, Goyal et al. (2019), Rajjoub et al. (2022), and Chang et al. (2022) argued that ending instrumentation at the cervical level was associated with higher rates of ASD and reoperation. However, Truumees et al. (2022) and Coban et al. (2022) found no statistically significant differences between cases of instrumentation ending at the cervical and thoracic levels in the rates of ASD and requirement of revision surgery. Cervicothoracic junction breakage is a known possibility after cervical spine surgery because of the anatomical fragility of the junction. Terminating at the thoracic level reduces the stress on the cervicothoracic junction, thereby decreasing complications such as cervicothoracic junction breakage and lowering the frequency of reoperation. Based on the findings published to date, instrumentation across the cervicothoracic junction can be reasonably recommended in cases of multilevel posterior cervical fusion based on the lower reoperation and higher fusion rate.
