OBJECTIVETo explore efficacy and safety of using denervation of dorsal medial branch to treat the low back pain due to lumbar joint origin.

METHODSFrom March 2009 to October 2010,10 patients with the low back pain due to lumbar joint origin were enrolled in this study including 6 males and 4 females with an average age of 56.4 years old (41 to 68). The average disease duration was 1.2 years (0.5 to 3). All patients were operated by blocking the dorsal medial branch. Single branch (dorsal medial branch of the involved level), dual branches (dorsal medial branches of the involved and the upper or lower level, 5 with the upper level, 5 with the lower level), three branches (dorsal medial branches of the involved and the upper and lower levels), four branches (dorsal medial branches of the involved and the upper two and lower levels) were blocked by 0.5% lidocaine 15 ml compounded with betamethasone injection 1 ml (10 mg/ml) and a cobalt ammonium injection 500 microg at the junction of the superior articular process and the transverse process. Low back pain VAS, average EMG of multifidus of the involved level and low back muscle strength were assessed and statistically compared. Low back muscle strength was measured by the back power meter.

RESULTSThe mean low back pain VAS of the 10 patients in the preoperation was 6.85 +/- 1.55, in single branch blocked group was 5.80 +/- 1.05, in dual branches blocked group was 3.65 +/- 1.20, in three branches blocked group was 2.80 +/- 1.10 and in four branches blocked group was 2.75 +/- 1.15. Average EMG of multifidus was 69.25 +/- 2.13 in the preoperation,in single branch blocked group was 62.15 +/- 1.85, in dual branches blocked group was 51.25 +/- 1.28, in three branches blocked group was 47.30 +/- 1.85 and in four branches blocked group was 45.96 +/- 1.98. The mean low back muscle strength was 60 kg in the preoperation, in single branch blocked group was 55 kg,in dual branches blocked group was 48 kg, in three branches blocked group was 44 kg and in four branches blocked group was 43 kg. Among the dual branches blocked group,low back pain VAS and low back muscle strength in the dorsal medial branches of the involved and the upper level blocked showed great decline compared with those in the dorsal medial branches of the involved and the lower level blocked.

CONCLUSIONIt is effective by denervation of dorsal medial branch to treat the low back pain due to lumbar joint origin. There are significant difference in low back pain VAS between every two among the preoperation,single branch blocked group,dual branches blocked group and three branches blocked group. There is no significant difference between four branches blocked group and three branches blocked group. In low back muscle strength and average EMG of multifidus, compared with the preoperation group,there is no significant decline in single branch blocked and dual branches blocked group,and there is significant decline in three branches blocked and four branches blocked group. Therefore, single or dual dorsal medial branch blocked is safety. Among the dual branches blocked group, dorsal medial branches of the involved and the upper level blocked should be given priority to. There is a certain risk in three or four dorsal medial branches blocked which should be used with caution.