Objectives:

To identify cage and endplate factors of cage subsidence in patients who underwent oblique lateral interbody fusion (OLIF) and their association with patient-reported outcomes.

Methods:

Sixty-one patients (43 women and 18 men), with a total of 69 segments (138 endplates) which underwent OLIF at a single academic institution between November 2018 and November 2020 were included. All the endplates were separated into cage subsidence (CS) and non-subsidence (NS) groups. Cage-related parameters (cage height, cage width, cage insertion level, and cage position) and endplate-related parameters (position of endplate, HU value of the vertebra, endplate concave angle [ECA], endplate injury, and angular mismatch measured with cage/endplate angle [C/EA]) were compared and analyzed using logistic regression to predict cage subsidence. Receiver operating characteristic (ROC) curve analysis was used to determine the cutoff points of the parameters.

Results:

Postoperative cage subsidence was identified in 50 of the 138 endplates (36.2%). The CS group had a significantly lower mean HU values of the vertebra, higher rate of endplate injury, lower ECA, and higher C/EA than the NS group. ECA and C/EA were identified as independent risk factors for developing cage subsidence. The optimal cutoff points for ECA and C/EA were 176.9° and 5.4°, respectively.

Conclusions:

An endplate concave angle greater than 176.9° and a cage/endplate angular mismatch greater than 5.4° were found to be independent risk factors of postoperative cage subsidence after the OLIF procedure. These findings aid in preoperative decision-making and intraoperative technical guidance.