Lumbar Facet Tropism on Different Facet Portions and Asymmetry Between Ipsilateral Cephalad and Caudad Portions: Their Correlations With L4/5 and L5/S1 Lumbar Disc Herniation.

STUDY DESIGN:A retrospective case-control study. OBJECTIVE:To investigate the correlation between lumbar disc herniation (LDH) and lumbar facet tropism (FT) on cephalad and caudad facet portions, respectively; to investigate the asymmetry between ipsilateral cephalad and caudad facet portions and its correlation with LDH. SUMMARY OF BACKGROUND DATA:There are still heavy debates on the exact correlation between lumbar FT and LDH. However, no study ever focused on the FT on different facet portions and asymmetry between ipsilateral cephalad and caudad portions in patients with LDH. METHODS:One hundred patients with L4/5 LDH, 100 patients with L5/S1 LDH, and 100 participants without LDH (control group) were age and sex matched and included in this study. Participants in each group were further divided into two subgroups based on age (≥ or < 50 yr old). Bilateral facet joint angles on both cephalad and caudad portions were measured. FT and asymmetry between ipsilateral cephalad and caudad portions in each LDH group were compared with those in corresponding control group. RESULTS:Comparing with control participants, the mean difference of bilateral facet angles in older patients with L4/5 LDH was significantly greater either on cephalad portion and caudad portion, whereas significantly higher frequency of FT was only exhibited on cephalad portion. In older patients with L4/5 LDH, the mean difference of facet angle between ipsilateral cephalad and caudad portions was significantly greater than that of control participants, the frequency of ipsilateral cephalad, and caudad facet asymmetry was also significantly higher. CONCLUSIONS:Only the FT on cephalad portion but not caudad portion of facet joint is associated with L4/5 LDH of older patients. The measurement on different portions of facet joint may result in discrepancy on FT identification. Asymmetry between ipsilateral cephalad and caudad facet portions is also associated with L4/5 LDH in older patients. LEVEL OF EVIDENCE:3.