FACET GEOMETRY AND UNILATERAL LUMBAR DISC HERNIATION
Authors: Moon Myung-Sang , Kim Dong-Hyeon , Yoon Min-Geun , Kim Sung-Soo , Sihn Jang-Cheol 
Published: March 2017

Up to now there have been two contradictory opinions in regard to lumbar facet role in the development of disc degeneration and herniation. To reconfirm the clinical validity of facet arrangement in the development of early disc degeneration and herniation, this study was carried out. For this purpose, the relationship between lumbar unilateral disc protrusion and geometry of the facet joints in the transverse plane was investigated. Method: The facet geometry was measured at the L4 disc level in the 35 protruded disc patients and L5 disc level in the 19 protruded disc patients. The computed tomographic scan sections were made 2[Formula: see text]mm intervals. The discs of L4 and L5 levels in the patients without disc protrusion and patients with spine injury were used as control. Results: 1. The facet angle showed the different individual variance. Among the L[Formula: see text] disc herniation group, the mean facet angle in the protruded and opposite sides and control were [Formula: see text] (29–70[Formula: see text]), [Formula: see text] (29–65[Formula: see text]), and [Formula: see text] (30–65[Formula: see text]). Those values at L5-S1 level were [Formula: see text] (35–79[Formula: see text]), [Formula: see text] (36–79[Formula: see text]), and [Formula: see text] (36–79[Formula: see text]), respectively. 2. Transverse interfacet angle (TIFA) of the L[Formula: see text] protruded disc level and that of control were 97–14[Formula: see text] (59–125[Formula: see text]) and [Formula: see text] (66–127[Formula: see text]). Those of L5-S1 level were [Formula: see text] (70–132[Formula: see text]) and [Formula: see text] (76–151[Formula: see text]). 3. The angle difference between both sides in the case of the facet asymmetry at L[Formula: see text] disc level was [Formula: see text] (0–30[Formula: see text]), and that of the control was [Formula: see text] (0–15[Formula: see text]), and those of L5-S1 level were [Formula: see text] (0–24[Formula: see text]) and [Formula: see text] (0–24[Formula: see text]), respectively. Disc herniation developed toward the more obliquely aligned facet joint side in 19 (54.2%) out of the 35 patients at the L[Formula: see text] disc, while disc herniation at L5-S1 level developed toward the more obliquely aligned facet joint side in 11 (57.9%) out of the 19 patients. 4. Among the L[Formula: see text] disc level, the mean moment arm angles in the disc-protruded side, the opposite side and control were [Formula: see text] (16–40[Formula: see text]), [Formula: see text] (15–35[Formula: see text]), and [Formula: see text] (16–35[Formula: see text]). Those of L5-S1 level each were [Formula: see text] (21–36[Formula: see text]), [Formula: see text] (17–35[Formula: see text]), and [Formula: see text] (16–35[Formula: see text]), respectively. 5. At the L[Formula: see text] level, the mean non-dimensional facet depths in the disc-protruded side, the opposite side, and control were [Formula: see text] (0–0.36[Formula: see text]), [Formula: see text] (0–0.41[Formula: see text]), and [Formula: see text] (0.02–0.28[Formula: see text]). Those facet depths at L5-S1 level were [Formula: see text] (0.02–0.28[Formula: see text]), [Formula: see text] (0.02–0.2[Formula: see text]), and [Formula: see text] (0.02–0.28[Formula: see text]). Conclusion: The five parameters including facet angle showed clinically no significant correlation with the disc herniation.