[Biomechanical study of interspinous fixational effect on the stiffness of adjacent segments].
OBJECTIVE
To discuss the effect of interspinous fixation (Wallis) on the stiffness of adjacent segments by biomechanical measurements.


METHODS
The surgical segments of all 23 patients were L4/5 lumbar disc herniation with or without lumbar stenosis. Thirteen patients (experimental group) underwent interspinous (Wallis) fixation, and ten patients (control group) underwent PLIF. L3/4 and L5/S1 segmental stiffness and displacement were measured by a spine stiffness gauge (SSG) device during surgery when the vertebral plate was exposed or during spinal decompression or internal fixation.


RESULTS
Stiffness of adjacent segments L3/4 and L5/S1 showed no significant difference between the L4/5 segment decompression and the exposure of the vertebral plate. After interspinous (Wallis) fixation of L4/5, the stiffness of the cephalad adjacent segment L3/4 was (45.8 ± 10.7) N/mm, which was 20.5% more than that after exposure of the vertebral plate (P=0.025); After L4/5 PLIF, the stiffness of L3/4 was (35.3 ± 10.7) N/mm and was decreased by 12.4% less than that after exposure of the vertebral plate (P=0.033). The stiffness of the cephalad adjacent segment L3/4 after fixation in the Wallis group was significantly higher than that of the PLIF group (P=0.037).


CONCLUSIONS
After interspinous (Wallis) fixation, the stiffness and the stability of the cephalad adjacent segment increased. The interspinous fixation system (Wallis) has a protective effect on cephalad adjacent segments.
Department of Orthopedics, Peking University First Hospital, Beijing 100034, China. lichunde@medmail.com.cn
Chun-de
CD
Li
Hao-lin
HL
Sun
Zheng-rong
ZR
Yu
D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007403:Intervertebral Disc / Q000601:surgery; D007405:Intervertebral Disc Displacement / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology*; D013123:Spinal Fusion / Q000379:methods*; D013130:Spinal Stenosis / Q000150:complications / Q000601:surgery*