A biomechanical comparison between anterior and transverse interbody fusion cages.
METHODS
Human cadaveric lumbar spines underwent placement of threaded fusion cages (TFCs) in either an anterior or transverse orientation. Spines underwent load testing and angular rotation measurement in the intact state, after diskectomy, after cage placement, and after fatiguing. Angular rotations were compared between cage orientations and interventions.


OBJECTIVE
To determine which cage orientation resulted in greater immediate stability.


BACKGROUND
There has been extensive biomechanical study of interbody fusion cages. The lateral orientation has been increasingly used for intervertebral fusion, but a direct biomechanical comparison between cages implanted either anteriorly or transversely in human cadaveric spines has not been performed.


METHODS
Fourteen spines were randomized into the anterior group (anterior diskectomy and dual anterior cage placement) and the lateral group (lateral diskectomy and single transverse cage placement). Pure bending moments of 1.5, 3.0, 4.5, and 6.0 Nm were applied in flexion, extension, lateral bending, and axial rotation. Load testing was performed while intact, after diskectomy, after cage placement, and after fatiguing. Angular rotation was compared between anterior and lateral groups and, within each group, among the different interventions.


RESULTS
Segmental ranges of motion were similar between spines undergoing either anterior or lateral cage implantation.


CONCLUSIONS
These results demonstrate few differences between angular rotation after either anterior or lateral TFC implantation. These findings add to data that find few differences between orientation of implanted TFCs. Combined with a decreased risk of adjacent structure injury through a lateral approach, these data support a lateral approach for lumbar interbody fusion.
Heth
J A
JA
Division of Neurosurgery, University of Iowa, Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA.
Hitchon
P W
PW
Goel
V K
VK
Rogge
T N
TN
Drake
J S
JS
Torner
J C
JC
D002102:Cadaver; D017586:Diskectomy; D005221:Fatigue; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D009984:Orthopedic Fixation Devices; D018583:Pliability; D019736:Prostheses and Implants; D011859:Radiography; D011897:Random Allocation; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D012447:Sacrum / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology