Study Design. A descriptive morphologic anatomic study was performed.
Objective. The study aimed to investigate intra-articular meniscoids (folds) and cartilage quality in the thoracic zygapophysial joints (ZAJs), and to discuss them in the context of possible causes of thoracic back pain.
Summary of Background Data. The clinical relevance of the intra-articular meniscoid structures described in the cervical and lumbar spine is unclear, particularly in relation to ZAJ blockades. Corresponding data for the thoracic joints are not available.
Methods. A total of 297 ZAJs between C7 and L1, obtained from 12 human cadavers (7 female, 5 male; mean age 81 years), were studied. The intra-articular folds were described and classified morphologically. The characteristics of the folds and their association with zygapophysial cartilage quality were investigated. Thirteen example folds were studied histologically.
Results. In all, 268 intra-articular meniscoid folds were found in 183 joints. Three types were identified: type 1 (90%; mean length 3.1 mm) were thin, solid folds originating from a connective-tissue base, with multiple vessels at the joint capsule, extending between the joint surfaces. Type 2 folds (6%) were soft structures of fat and loose connective tissue including multiple vessels, located in the joint recess and not extending between the joint surfaces. The remaining folds (type 3, 4%) were circumscribed thickenings of the joint capsule. Three folds showed chronic hemorrhage, with dilated vessels at the base, and this was associated with severe cartilage lesions. In 16 folds, the base had direct tissue connection to the fat tissue of the epidural space.
Conclusion. This study for the first time systematically classifies intra-articular meniscoid folds in human thoracic ZAJs. These folds may represent an anatomic correlate for thoracic back pain. The chronic hemorrhage observed may be an important factor leading to arthritis.