Can posterior stand-alone expandable cages safely restore lumbar lordosis? A minimum 5-year follow-up study
Abstract Background Lumbar lordosis (LL) can be restored and screw-related complications may be avoided with the stand-alone expandable cage method. However, the long-term spinopelvic profile changes and safety remain unknown. We aimed to elucidate the long-term radiologic outcomes and safety of this technique. Methods Data from a total of 69 patients who underwent multi-level stand-alone expandable cage fusion and 80 patients who underwent screw-assisted fusion between February 2007 and December 2012, with at least 5 years of follow-up, were retrospectively analyzed. Segmental angle and translation, short and whole LL, pelvic incidence, pelvic tilt, sacral slope (SS), sagittal vertical balance, thoracic kyphosis, and presence of subsidence, pseudoarthrosis, retropulsion, cage breakage, proximal junctional kyphosis (PJK), and screw malposition were assessed. The relationship between local and spinopelvic effects was investigated. The implant failure rate was considered a measure of procedure effectiveness and safety. Results The stand-alone expandable cage fusion group showed shorter operative times, a lower rate of PJK, and better improvements in segmental angles than the control group, and there was a positive correlation with LL. However, the whole LL was not restored; the SS significantly increased; and subsidence, pseudoarthrosis, and retropulsion rates were significantly higher than those in the control group. Conclusions Stand-alone expandable cage fusion can restore local lordosis, however, global sagittal balance was not restored. Furthermore, implant safety still has not been proven.