Analysis of factors impacting inter-body fusion cage subsidence following an oblique lateral interbody fusion (OLIF) stand-alone procedure

BackgroundLumbar oblique lateral interbody fusion (OLIF stand-alone) procedures have become a common treatment for various spinal conditions, including spinal stenosis and spondylolisthesis. However, cage subsidence following OLIF stand-alone procedures is a significant concern that can compromise the surgical outcomes.ObjectiveTo investigate the occurrence of cage subsidence following OLIF procedures and identify the relevant factors influencing cage subsidence.MethodA retrospective analysis was conducted on 86 patients who underwent elective OLIF stand-alone procedures at the Affiliated People's Hospital of Qingdao University between 2019 and 2023. Patients were categorized into two groups based on disc height (DH) subsidence: cage non-subsidence group (< 2 mm) and cage subsidence group (> 2 mm). General and imaging data were collected pre-surgery, post-surgery, and at six months follow-up. Single-factor analysis identified factors influencing cage subsidence, followed by multi-factor regression analysis on these variables to determine their impact.ResultsWhen the degree of DH subsidence in the last follow-up (M6) was evaluated, among the 86 patients (102 segments), 26 patients (25.49%) fulfilled the criteria for cage subsidence. Factors with clinical and statistical significance in the single-factor analysis were incorporated into the multi-factor analysis, and it was found that the mean CT value of the concerned segment, multifidus area, and severe multifidus atrophy were relevant risk factors for cage subsidence; the protective factors for cage subsidence were degree III zygapophyseal joint degeneration, posterior cage position, and end-plate inflammation sclerosis (P < 0.05).ConclusionSurgeons should be cautious in preoperatively identifying patients at risk of cage subsidence, particularly those with a low mean CT value of the concerned segment or severe multifidus atrophy. During surgery, selecting a cage of adequate length to span the epiphyseal ring and align with the original DH can help protect paravertebral muscles from iatrogenic injury and reduce the risk of cage subsidence.