Experimental study of lumbar facet degeneration in monkeys.

Experiments were carried out in young adult monkeys to determine the influence of mechanical stress on degeneration of the lumbar facet joints. Eleven monkeys were used and divided into four groups, the control, upper lumbar laminectomy, discectomy and discectomy + rotation. The monkeys were given fluorochrome agents once a week. After sacrifice, undemineralised sections were studied under fluorescence microscopy. Contact microradiographs were also made. After laminectomy, subperiosteal bony proliferation was seen on the external surface of the superior and inferior articular processes. After discectomy there was localised bony proliferation on the anterior aspect of the superior articular processes. In the group with discectomy + rotation there was evidence of additional proliferation of the calcified cartilage zone at the insertion of the ligamentum flavum which had remodelled to bony tissue. We conclude that rotational stresses are mostly responsible for the development of spinal stenosis.