Posterior stabilization at the cervicothoracic junction: a biomechanical study.
METHODS
This study biomechanically evaluated three fixation devices for stability with posterior two- and three-column injuries.


OBJECTIVE
To find an effective means of posteriorly stabilizing injuries at the cervicothoracic junction.


BACKGROUND
The cervicothoracic spine is complex anatomically and has been a difficult challenge in approach and stabilization of traumatic and degenerative disorders.


METHODS
Twenty-one human cadaveric spines (C3-T3) were loaded in flexion, extension, lateral bending, and axial torsion. A posterior two-column injury was created at C7-T1. One of three posterior fixation systems was applied (two rod-screw systems, one plate-screw system, all with screws at C5, C6 and T1, T2). The spines were tested again. A three-column injury was created by transecting the remaining anterior structures; the spines were tested a final time.


RESULTS
In flexion-extension, there were no significant differences in stiffness between intact and instrumented two-column injury specimens for all systems; the instrumented three-column injury was significantly (P < 0.05) less stiff than intact specimens in extension. Ranges of motion and neutral zones decreased from intact to instrumented two-column injuries and increased from intact to three-column constructs. In lateral bending and axial rotation, all systems were stiffer than intact spines for both injuries; ranges of motion and neutral zones were reduced for both injuries compared with intact specimens.


CONCLUSIONS
All three systems stabilize the cervicothoracic junction with a posterior two-column injury in flexion-extension, lateral bending, and axial rotation; none was adequate for a three-column injury, particularly in extension. A three-column injury at this level would warrant supplemental anterior fixation.
Kreshak
Jennifer L
JL
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut 06520-8071, USA.
Kim
Daniel H
DH
Lindsey
Derek P
DP
Kam
Andrew C
AC
Panjabi
Manohar M
MM
Yerby
Scott A
SA
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries* / Q000503:physiopathology; D005260:Female; D005592:Fracture Fixation / Q000295:instrumentation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices / Q000592:standards; D012399:Rotation