Apoptosis of endplate chondrocytes in post-laminectomy cervical kyphotic deformity. An in vivo animal model in sheep.

PURPOSE: The present study was performed to establish an animal model of cervical kyphosis after laminectomy (C2-C5), and to determine the role of endplate chondrocytes apoptosis in cervical kyphosis after laminectomy.

METHODS

Twenty-four 3-month-old sheep were randomly divided into two groups: the laminectomy group (n = 12), and the control group (n = 12). The cervical spine alignment was evaluated on a lateral cervical spine X-ray using Harrison's posterior tangent method before surgery and at follow-up. Cartilaginous endplate chondrocyte apoptosis was confirmed using transmission electron microscopy and terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labelling.

RESULTS

The mean preoperative cervical curvature (C2-5) in the surgery group was -15.8°. The cervical curvature was 19.1° at 3 months post-operation and decreased to 20.2° at the final follow-up postoperatively. The cervical curvature was significantly decreased in the laminectomy group compared with the control group at the last follow-up (P < 0.001), which was a direct indication of kyphotic change. The incidence of apoptotic cells in the surgery group was significantly higher at the 3- and 6-month follow-up than the incidence in the control group.

CONCLUSIONS

The frequency of endplate chondrocyte apoptosis in the laminectomy group was significantly higher than in the control group, indicating that chondrocyte apoptosis may play a pivotal role in the progress of post-laminectomy cervical kyphosis.