Biomechanical testing of a novel four-rod technique for lumbo-pelvic reconstruction.
METHODS
A biomechanical testing protocol was used to study different lumbo-pelvic fixation techniques in a human cadaveric lumbar spine model.


OBJECTIVE
To compare the in vitro biomechanics of a novel four-rod lumbo-pelvic reconstruction technique with and with out cross-links, to that of a conventional cross-linked two-rod technique.


BACKGROUND
Numerous lumbo-pelvic reconstruction methods based on the Galveston two-rod technique have been proposed for cases involving total sacrectomy. Recently a technique that proposes novel use of 4 supporting longitudinal rods across the lumbo-pelvic junction has been reported. No comparative in vitro biomechanical testing has been previously done to evaluate these different reconstruction methods.


METHODS
Five spines were evaluated in flexion, extension, left-right lateral bending and left-right axial rotation in a human total sacrectomy model. The model was comprised of cadaveric lumbar spines (L1-L5) with custom fabricated polyethylene blocks used to simulate pelvic fixation. Three conditions were evaluated: Linked Four-Rod, Linked Two-Rod, and Four-Rod (no cross-links). Flexibility and motion data were compared using a one-way repeated measures analysis of variance and SNK tests.


RESULTS
The Linked Four-Rod and Four-Rod conditions significantly decreased flexibility and reduced L5-Pelvic motion over the Linked Two-Rod construct in flexion and extension. The Linked Four-Rod condition significantly decreased flexibility in left-right axial rotation compared with the Four-Rod and Linked Two-Rod conditions. No significant differences occurred in relative lateral movement between left and right pelvic polyethylene blocks.


CONCLUSIONS
The four-rod technique improved fixation stability over the conventional linked two-rod technique in flexion and extension, and when cross-linked, in left-right axial rotation. The four-rod technique also significantly reduced L5-Pelvic junction movement in flexionand extension, which may have implications for bony fusion. The use of cross-links is recommended.
Department of Biomedical Engineering and Imaging, University of Tennessee Health Science Center, Memphis, TN 38163, USA. bkelly@utmem.edu
Brian P
BP
Kelly
Francis H
FH
Shen
John S
JS
Schwab
Vincent
V
Arlet
Denis J
DJ
Diangelo
D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008422:Materials Testing; D009984:Orthopedic Fixation Devices; D010027:Osteotomy; D010384:Pelvic Bones / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular; D012399:Rotation; D012447:Sacrum / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*