Lumbar facet joint angle and its importance on joint violation in lumbar microdiscectomy.

OBJECTIVE: We investigated facet joint angle at the level of the nucleus pulposus in herniated disks and documented the importance of this angle in preserving articulation and surgical view in patients undergoing lumbar microdiscectomy.

METHODS: In this prospective study using pre- and postoperative magnetic resonance imaging scans, two blinded radiologists measured and inspected the facet joint angles in 168 patients. Patients were treated with single-level, unilateral, lumbar microdiscectomy. Postoperatively, patients were divided into two groups according to whether or not any portion of the facet joint had been violated during surgery. Using the magnetic resonance imaging scans, the angles of the facet joints were measured and then correlated with whether or not the facet joint was preserved.

RESULTS: The follow-up period for this study was 6 months. Postoperative radicular and back pain during the follow-up period and the need for opioids in the early postsurgery period (48 h) were higher in the nonpreserved group, but these differences were not statistically significant (P > 0.05). If the facet joint angle at the disc was lower than 35 degrees in the horizontal plane, articulation cannot be preserved. However, if this angle is greater than 35 degrees, articulation may be preserved and the surgical view is satisfactory for lumbar microdiscectomy.

CONCLUSION: The angle of the lumbar facet joint is important to protect articulation during lumbar microdiscectomy, and violating the facet joint may affect early postoperative pain. A facet angle of less than 35 degrees does not allow for a safe surgical corridor in which to use instruments, nor does it provide a satisfactory view for the surgeon.