Intradiscal pressure and kinematic behavior of lumbar spine after bilateral laminotomy and laminectomy.
BACKGROUND
Bilateral laminotomy has been proposed as an alternative to laminectomy for decompression of lumbar spinal stenosis. Preservation of the posterior midline ligaments with laminotomy is presumed to maintain spinal segment stability. There have been no previous studies that directly compare the amount of destabilization and increase in disc pressures between the two procedures.


OBJECTIVE
To quantify spinal segmental instability caused by bilateral laminotomy and laminectomy, and to compare the central and peripheral intradiscal pressures after the two procedures.


METHODS
Mechanical testing of the lumbar motion segments of calf spines.


METHODS
Nine fresh calf spines were tested under flexion, extension, lateral bending and axial rotation, intact first, then after laminotomy and laminectomy at the level of L4-L5. Four miniature pressure transducers were implanted in the central and peripheral disc at L4-L5 to measure intradiscal pressures. Three-dimensional motion was measured with motion analysis system.


RESULTS
Comparing with bilateral laminotomy, laminectomy showed significant increase in segmental motion at the surgical level in flexion (16%, p<.05), extension (14%, p<.04) and right axial rotation (23%, p<.03). In flexion, the stress at the anterior annulus increased a nonsignificant 20% after laminotomy, but significant 130% after laminectomy (p<.02). In the intact spine, the posterolateral annulus experienced the highest stress with lateral bending to the same side when compared with other loading directions. This stress remained unchanged after laminotomy but increased 9% after laminectomy (p<.06). In rotation, axial intradiscal stresses were evenly distributed and unchanged after each procedure.


CONCLUSIONS
Laminectomy causes more destabilization of a spinal motion segment than laminotomy and significantly increases disc stress in the anterior annulus.
Department of Orthopaedic Surgery, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA. rrao@mcw.edu
Raj D
RD
Rao
Mei
M
Wang
Peeush
P
Singhal
Linda M
LM
McGrady
Santi
S
Rao
D000818:Animals; D001696:Biomechanical Phenomena; D002102:Cadaver; D002417:Cattle; D019299:Decompression, Surgical / Q000379:methods*; D007403:Intervertebral Disc / Q000502:physiology*; D007796:Laminectomy / Q000379:methods*; D008159:Lumbar Vertebrae / Q000601:surgery*; D011312:Pressure; D011336:Probability; D016059:Range of Motion, Articular / Q000502:physiology; D012016:Reference Values; D012680:Sensitivity and Specificity; D013130:Spinal Stenosis / Q000601:surgery; D013131:Spine / Q000601:surgery*; D013314:Stress, Mechanical