AI Article Synopsis

  • The study examines the effectiveness of upper and lower iliac screw placements in lumbo-pelvic reconstruction, assessing their anchoring strengths both with and without bone cement.
  • The experiment involved testing five pairs of cadaveric ilia, measuring the maximum pull-out strengths after subjecting them to cyclic loading, revealing that lower screws showed significantly better pull-out strength compared to upper screws.
  • The findings suggest that lower iliac screws are preferable for surgery, and that using cement can enhance screw stability, while also emphasizing the importance of evaluating bone quality before surgery.

Article Abstract

Background: Iliac screw loosening has been a clinical problem in the lumbo-pelvic reconstruction. Although iliac screws are commonly inserted into either upper or lower iliac column, the biomechanical effects of the two fixations and their revision techniques with bone cement remain undetermined. The purpose of this study was to compare the anchoring strengths of the upper and lower iliac screws with and without cement augmentation.

Methods: 5 pairs of formalin fixed cadaveric ilia with the bone mineral density values ranged from 0.82 to 0.97 g/cm(2) were adopted in this study. Using screws with 70-mm length and 7.5-mm diameter, 2 conventional iliac screw fixations and their revision techniques with cement augmentation were sequentially established and tested on the same ilium as follows: upper screw, upper cement screw, lower screw, and lower cement screw. Following 2000 cyclic compressive loading of -300 N to -100 N to the screw on a material testing machine, the maximum pull-out strengths were measured and analyzed.

Findings: The average pull-out strengths of upper, upper cement, lower, and lower cement screws were 964 N, 1462 N, 1537 N, and 1964 N, respectively. The lower screw showed significantly higher pull-out strength than the upper one (P=0.008). The cement augmentation notably increased the pull-out strengths of both upper and lower screws. The positive correlation between pull-out strength and bone mineral density value was obtained for the 4 fixations.

Interpretation: The lower iliac screw technique should be the preferred choice in lumbo-pelvic stabilization surgery; cement augmentation may serve as a useful salvage technique for iliac screw loosening; preoperative evaluation of bone quality is crucial for predicting fixation strength of iliac screw.

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Source
http://dx.doi.org/10.1016/j.clinbiomech.2011.01.008DOI Listing

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