Screw omission and the stability of posterior pedicle screw constructs for short-segment stabilization.
J Spinal Disord
; 10(3): 240-5, 1997 Jun.
Article
in En
| MEDLINE
| ID: mdl-9213281
ABSTRACT
To determine the net contribution of a spinal construct to stability, and whether extending the construct to another level in situations in which a defective pedicle cannot have a screw inserted, we performed biomechanical tests in which we evaluated three-, four-, and five-level synthetic spinal constructs in which the location and number of pedicle screws were varied above and below a vertebrectomy defect. We subjected all constructs to axial, compression, lateral bending, flexion, extension, and torsional forces with the use of an Instron biaxial machine. Left-right symmetrical constructs were more stable than asymmetrical ones. Three-level constructs were statistically stiffer than the longer ones in compression, left bending, and flexion. Torsional stability, however, was greater in the longer constructs. Five-level constructs with both end screws in place had greater torsional stiffness than when they were missing a screw. In vertebrectomy defects, if four screws cannot be placed across it, then the engagement of two screws is indicated. The stability provided by a single screw at a spinal level is minimal. Additional screws augment the purchase of the construct in the bone; however, they do not afford further protection to the defect.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Bone Screws
Type of study:
Diagnostic_studies
/
Evaluation_studies
Language:
En
Journal:
J Spinal Disord
Journal subject:
ORTOPEDIA
Year:
1997
Document type:
Article
Affiliation country:
Estados Unidos