The effects of an interspinous implant on the kinematics of the instrumented and adjacent levels in the lumbar spine.
METHODS
Measurement of the kinematics of the lumbar spine after insertion of an interspinous spacer in vitro.


OBJECTIVE
To understand the kinematics of the instrumented and adjacent levels due to the insertion of this interspinous implant.


BACKGROUND
An interspinous spacer (X Stop, SFMT, Concord, California) has been developed to treat neurogenic intermittent claudication by placing the stenotic segment in slight flexion and preventing extension. This restriction of motion by the interspinous implant may affect the kinematics of levels adjacent to the instrumented level.


METHODS
Seven lumbar spines (L2-L5) were tested in flexion-extension, lateral bending, and axial rotation. Images were taken during each test to determine the kinematics of each motion segment. The interspinous implant was placed at the L3-L4 level, and the test protocol was repeated.


RESULTS
The flexion-extension range of motion was significantly reduced at the instrumented level. Axial rotation and lateral bending ranges of motion were not affected at the instrumented level. The range of motion in flexion-extension, axial rotation, and lateral bending at the adjacent segments was not significantly affected by the implant.


CONCLUSIONS
The implant does not significantly alter the kinematics of the motion segments adjacent to the instrumented level.
Lindsey
Derek P
DP
VA Rehab R & D Center, Palo Alto, CA, USA. lindsey@rrdmail.Stanford.edu
Swanson
Kyle E
KE
Fuchs
Paul
P
Hsu
Ken Y
KY
Zucherman
James F
JF
Yerby
Scott A
SA
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D006801:Humans; D007383:Intermittent Claudication / Q000601:surgery; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery*; D008875:Middle Aged; D009068:Movement; D019736:Prostheses and Implants; D015203:Reproducibility of Results; D012399:Rotation