[Effect of prosthetic nucleus pulposus replacement on stress distributions of lumbar disc endplate].
OBJECTIVE
To determine the stress distribution on endplate after lumbar prosthetic disc nucleus (PDN) replacement.


METHODS
Six fresh lumbar vertebrae with normal Modic classification were harvested. The specimens were used to establish L4-5 intact, nucleotomy, prosthetic nucleus pulposus replacement models. Vertical compression tests were performed with MTS machine at the rate 50 N per second to maximum load of 1300 N. The stress under the endplate were measured directly with accurate pressure sensors.


RESULTS
For intact specimens, the stress on the endplate maintained higher in the central zone of the endplate, and decreased gradually to the periphery, and was well-distributed. After nucleotomy, the stress on the central zone of endplate was significantly decreased, and increased stress occurred in the periphery of endplate. After PDN replacement, the stress on the central zone of endplate was found more 15.1% higher than that in intact disc (P < 0.05), and the neighboring zone also showed higher stress measurements.


CONCLUSIONS
After lumbar prosthetic disc nucleus replacement, the stress concentration on endplate may occur in the central zone of prosthetic disc nucleus insertion. Therefore, the prosthetic nucleus pulposus with suitable shape, proper biomechanical functions and updated materials need further study.
Qu
Dong-bin
DB
Department of Orthopaedic and Spinal Surgery, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China. nfyy_qu@yahoo.com.cn
Zhao
Liang
L
Jin
Da-di
DD
D000328:Adult; D019643:Arthroplasty, Replacement; D002358:Cartilage, Articular / Q000502:physiology*; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000601:surgery*; D008875:Middle Aged; D013314:Stress, Mechanical