Biomechanical characteristics of hybrid hook-screw constructs in short-segment thoracic fixation.
METHODS
Ex vivo biomechanical testing of human cadaveric thoracic spine segments.


OBJECTIVE
To determine whether a hybrid construct, using a combination of pedicle screws (PSs) and lamina hooks, was equivalent to a PS construct, in a short-segment thoracic spine fixation model.


BACKGROUND
Comparisons have been made among PS, lamina hook, and hybrid screw-hook constructs, but these have generally been in long-segment scoliosis correction. In this study, we compared the hybrid and screw-only constructs in a short-segment thoracic fixation.


METHODS
For pullout testing, matched specimens were used for PS (n = 8) and hybrid (n = 8) constructs. Construct stiffness, and the force required for construct failure, were measured. Dynamic testing was carried out on specimens in the PS (n = 7) and hybrid (n = 7) groups in compression, flexion, extension, and left and right lateral bending. Each group was tested intact, after instrumentation, and after corpectomy.


RESULTS
When compared with the hybrid group, a significantly greater force was required for construct failure in the PS group, and these PS constructs were significantly stiffer. No differences were found between groups in dynamic testing.


CONCLUSIONS
A construct employing PSs is significantly stiffer and more resistant to pullout failure than a hook-screw hybrid construct.
Jones
G Alexander
GA
Spine Research Laboratory, Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA. jonesg@ccf.org
Kayanja
Mark
M
Milks
Ryan
R
Lieberman
Isador
I
D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D004548:Elasticity; D019544:Equipment Failure Analysis; D006801:Humans; D016268:Internal Fixators; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016474:Weight-Bearing