Superior Facet Joint Violations in Single Level Minimally Invasive and Open Transforaminal Lumbar Interbody Fusion: A Comparative Study

STUDY DESIGN: Prospective comparative study. PURPOSE: To compare the incidence of iatrogenic superior facet joint violation (SFV) in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and open TLIF (OPEN-TLIF) at a single lower lumbar fusion level and to evaluate the patient and surgical factors influencing the outcome. OVERVIEW OF LITERATURE: Iatrogenic SFV is a significant risk factor for adjacent segment disease (ASD). Blind screw placement technique in MIS-TLIF contributes to the increasing incidence of iatrogenic SFV which can be influenced by several other potential factors. There are only limited studies comparing the incidence of iatrogenic SFV in MIS-TLIF and OPEN-TLIF. METHODS: In total, 225 cases (450 top screws; MIS-TIFL, 120; OPEN-TILF, 105) undergoing single-level lower lumbar fusion were included in the study. Postoperative computed tomography grading system was used to evaluate iatrogenic SFV. Patient and surgical factors such as age, body mass index, top-screw level, side of the top screw, depth of the spine, and superior facet joint angle (SFA) were analyzed in iatrogenic SFV and non-violation groups to determine their influence on iatrogenic SFV. The clinical outcomes in both groups were assessed preoperatively and postoperatively. RESULTS: The overall incidence of iatrogenic SFV and high-grade violations was higher in MIS-TLIF (41.25%) than in OPEN-TLIF (30.4%). In both groups, bivariate analysis showed a significantly greater incidence of the iatrogenic SFV in patients aged <60 years and those with obesity, top pedicle screws at L4, right-sided top screws, SFA >35°, and depth of the spine >50 mm. CONCLUSIONS: This study demonstrated that the incidence of iatrogenic SFV is greater in MIS-TLIF than in OPEN-TLIF at a single lower lumbar level. MIS-TLIF is effective for lumbar degenerative disease; however, the incidence of iatrogenic SFV was higher. Patient and surgical factors must be considered to protect the facet joints in both TLIF methods to avoid ASD.