Effects of strain distribution in the intervertebral discs on the progression of ossification of the posterior longitudinal ligaments.
METHODS
Strain distribution in the intervertebral discs was evaluated biomechanically using an engineering true strain calculation formula.


OBJECTIVE
This study was performed to clarify the involvement of dynamic factors in the progression of ossification of the posterior longitudinal ligament.


BACKGROUND
In patients with ossification of the posterior longitudinal ligament of the cervical spine, ossification frequently progresses after laminectomy. This suggests the involvement of dynamic factors in the progression of ossification. However, these factors have not yet been clarified.


METHODS
The analysis was performed on 101 patients with ossification of the posterior longitudinal ligament by employing dynamic lateral x-ray films of the cervical spine. The x-ray films were digitized and used as computer data for calculating the strain distribution. X-ray films were obtained again 5 years later, and the strain distribution and the presence or absence of progression of ossification were evaluated.


RESULTS
The progression of ossification of the posterior longitudinal ligament was highly correlated with abnormal strain distribution in the intervertebral discs. Progression of ossification was frequently observed in areas having disc distortion in tension and extension on the posterior longitudinal ligament.


CONCLUSIONS
In this study, the area of progression of ossification corresponded to the area showing uneven strain distribution and resultant concentration of dynamic stress. These results suggest an important role for dynamic factors in the progression of ossification of the posterior longitudinal ligament.
Matsunaga
S
S
Department of Orthopaedic Surgery, Faculty of Medicine, Kagoshima University, Japan.
Sakou
T
T
Taketomi
E
E
Nakanisi
K
K
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007403:Intervertebral Disc; D017846:Longitudinal Ligaments; D008297:Male; D008875:Middle Aged; D009790:Occupations; D009999:Ossification, Heterotopic / Q000000981:diagnostic imaging / Q000209:etiology*; D011859:Radiography; D013314:Stress, Mechanical