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Neurosurgery. 2010 Feb;66(2):E404-6; discussion E406. doi: 10.1227/01.NEU.0000363701.76835.BF.

In vitro biomechanical analysis of a new lumbar low-profile locking screw-plate construct versus a standard top-loading cantilevered pedicle screw-rod construct: technical report.

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  • 1Spinal Biomechanics Laboratory, Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013, USA.

Abstract

OBJECTIVE:

A standard top-loading lumbar pedicle screw-rod system is compared with a pedicle screw-plate system with smaller-diameter screws, more medial entry, and lower profile to assess the relative stability, strength, and resistance to fatigue of the 2 systems.

METHODS:

Seven human cadaveric specimens were studied with each surgical construct. Nondestructive, nonconstraining pure moments were applied to specimens to induce flexion, extension, lateral bending, and axial rotation while recording L5-S1 motion optoelectronically. After initial tests, specimens were fatigued for 10,000 cycles and retested to assess early postoperative loosening. Specimens were then loaded to failure in hyperextension.

RESULTS:

The standard screw-rod construct reduced range of motion to a mean of 20% of normal, whereas the screw-plate construct reduced range of motion to 13% of normal. Differences between systems were not significant in any loading mode (P > 0.06). The 14% loosening of the screw-rod system with fatigue was not significantly different from the 10% loosening observed with the screw-plate system (P > 0.15). Mean failure loads of 30 Nm for screw-rod and 37 Nm for screw-plate were also not significantly different (P = 0.38).

CONCLUSION:

Posterior fixation at L5-S1 using the low-profile screw-plate system offers stability, resistance to fatigue, and resistance to failure equivalent to fixation using a standard cantilevered pedicle screw-rod system.

[PubMed - indexed for MEDLINE]
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