NEUROCENTRAL SYNCHONDROSIS FRACTURE IN IMMATURE SPINES ASSOCIATED WITH PEDICLE SCREW TYPE FIXATION DEVICES

Citation
K. Sairyo et al., NEUROCENTRAL SYNCHONDROSIS FRACTURE IN IMMATURE SPINES ASSOCIATED WITH PEDICLE SCREW TYPE FIXATION DEVICES, Journal of spinal disorders, 11(2), 1998, pp. 142-145
Citations number
20
Categorie Soggetti
Clinical Neurology",Orthopedics
Journal title
ISSN journal
08950385
Volume
11
Issue
2
Year of publication
1998
Pages
142 - 145
Database
ISI
SICI code
0895-0385(1998)11:2<142:NSFIIS>2.0.ZU;2-W
Abstract
The purpose of this study is to clarify the weak point in immature lum bar vertebrae associated with pedicle screw instrumentation, Ten immat ure thoracic and lumbar vertebrae were collected from calf spines, Aft er installation of 6- and 7-mm-diameter pedicle screws into the pedicl es of each specimen, pullout force was applied to the screw using the uniaxial MTS system until failure. Tightening torque during installati on was measured. From the load-displacement curve, failure load was ca lculated and failure site was confirmed by radiographs. Inner pedicle diameters were measured after the pullout test, and percent fills of t he pedicle screw were calculated. Mean tightening torque was 1.4 or 2. 1 (Nm), mean failure load was 852.5 or 1.015.0 (N), and mean percent f ill was 81.4 or 93.5% for 6- or 7-mm screws, respectively. Tightening torque and percent fill in 7-mm screws were significantly (p < 0.01) g reater than that in 6-mm screws; however, failure load showed no signi ficant difference (p = 0.10) between the two screw groups. Failure by screw pullout occurred at the screw-bone interface or through the neur ocentral synchondrosis (NS). NS fractures were observed in 20% of 6-mm screws, 60% of 7-mm screws, and 40% overall, whereas interface failur es occurred in 80% of 6-mm screws, 40% of 7-mm screws, and 60% overall . In NS fracture group, tightening torque (p < 0.05) and percent fill (p < 0.01) were significantly greater than in the interface failure gr oup. The results led us to conclude that the mechanism of the NS fract ure is unclear. However, NS fracture could be one of the conceivable c omplications associated with pedicle screw fixation in the immature sp ine.