INTRODUCTION: Subchondral cyst is appeared at the osteoarthritic (OA) joint, and some associations between pain and the cyst at the OA joints were reported. In the lumbar spine, facet OA can induce the low back pain as the facet pain. Furthermore, facet disorder is one of the great issues following the artificial disc replacement. In this report, we clarified the epidemiology of the subchondral cyst of the facet joints.
METHODS: Total 160 patients with degenerative disorders were evaluated by CT. Herniated nucleus pulposus (HNP) in 43, lumbar spinal canal stenosis (LCS) in 42 and degenerative spondylolisthesis (SLIP) in 32 were included. These disorders were all found at L4/5. Therefore, subchondral cysts were evaluated at L4/5. For control, 43 patients having disorder at the other level were evaluated. We evaluated the cyst number with reference to age, gender, and BMI as the genetic factor, and with disc height, facet angle, facet osteophyte and joint effusion as the local factor. Relationship between diseases and cyst number was also evaluated.
RESULTS AND DISCUSSION: Total cyst mean number in the control, HNP, LCS and SLIP group was 2.5, 3.3, 11.2 and 17.1. The larger cyst (diameter > 2mm) mean number was 0, 0, 0.7 and 2.0. When the osteophyte developed, the cyst number increased. These data indicated that in the degenerated spinal condition, more facet subchondral cysts could be appeared. Also, larger size cysts were also common in the more degenerated condition. The cyst did not show any relationship with genetic factors. Interestingly, the joint having many subchondral cysts showed less joint effusion. Joint inflammation may not be related to the subchondral cysts.
CONCLUSION: In the more degenerative condition, the more subchondral cysts were observed. Larger size cysts were also common in the degenerated condition such as degenerative spondylolisthesis.