Biomechanics of stabilization after cervicothoracic compression-flexion injury.
METHODS
Biomechanical laboratory research.


OBJECTIVE
To determine whether anterior, posterior, or combined instrumentation provides the best stability for treating a cervicothoracic compression-flexion injury.


BACKGROUND
As the junction between the mobile cervical spine and rigid thoracic spine, the cervicothoracic junction poses unique challenges to the success of any fixation system spanning this region. Although posterior instrumentation is the preferred method of fixation in the unstable cervical spine, it is unknown whether this is the case across the unstable cervicothoracic junction.


METHODS
Flexion, extension, lateral bending, and axial rotation of cadaveric specimens were studied during application of nondestructive pure moments in a sequence of conditions: (1) intact, (2) after destabilization, (3) with posterior instrumentation from C6-T1 or T2, and (4) with corpectomy/graft and anterior alone or combined anterior/posterior instrumentation.


RESULTS
Compared to anterior instrumentation, posterior instrumentation allowed an 89% smaller range of motion (ROM) during lateral bending (P = 0.01) and 64% smaller ROM during axial rotation (P = 0.04). In most loading modes, combined instrumentation outperformed either anterior or posterior instrumentation alone. Most biomechanical measurements of stability improved when posterior instrumentation was extended from T1 to T2. Small and usually insignificant reductions in ROM averaging 15% were observed with C7 included in the posterior construct versus C7 excluded.


CONCLUSIONS
Combined instrumentation provides a significant improvement in stability over either anterior or posterior instrumentation alone. Extension of the posterior instrumentation to include T2 improves stability at T1-T2 as well as rostral levels. Inclusion of C7 in the construct is largely inconsequential biomechanically.
Department of Neurological Surgery, University of California, San Francisco, CA 94143-0112, USA. amesc@neurosurg.ucsf.edu
Christopher P
CP
Ames
M Hakan
MH
Bozkus
Robert H
RH
Chamberlain
Frank L
FL
Acosta
Stephen M
SM
Papadopoulos
Volker K H
VK
Sonntag
Neil R
NR
Crawford
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000293:injuries / Q000502:physiology / Q000601:surgery; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009068:Movement; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000293:injuries / Q000502:physiology / Q000601:surgery; D014102:Torsion Abnormality