Institute of Biotechnology, National Taiwan University, Taipei, Taiwan.
Bone and Joint Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Sci Rep. 2020 Jun 26;10(1):10441. doi: 10.1038/s41598-020-67489-2.
Screw loosening due to broken pedicles is a common complication resulting from the insertion of screws either with inadequate diameters or into an osteoporotic pedicle. In this novel in vitro study, we tried to clarify the contribution of the pedicle to screw fixation and subsequent salvage strategies using longer or larger-diameter screws in broken pedicles. Sixty L4 fresh-frozen lumbar vertebrae harvested from mature pigs were designed as the normal-density group (n = 30) and decalcified as the osteoporosis group (n = 30). Three modalities were randomly assigned as intact pedicle (n = 30), semi-pedicle (n = 15), and non-pedicle (n = 15) in each group. Three sizes of polyaxial screws (diameter × length of 6.0 mm × 45 mm, 6.0 mm × 50 mm, and 6.5 mm × 45 mm) over five trials were used in each modality. The associations between bone density, pedicle modality and screw pullout strength were analyzed. After decalcification for 4 weeks, the area bone mineral density decreased to approximately 56% (p < 0.05) of the normal-density group, which was assigned as the osteoporosis group. An appropriate screw trajectory and insertional depth were confirmed using X-ray imaging prior to pullout testing in both groups. The pullout forces of larger-diameter screws (6.5 mm × 45 mm) and longer screws (6.0 mm × 50 mm) were significantly higher (p < 0.05) in the semi- and non-pedicle modalities in the normal-density group, whereas only longer screws (6.0 mm × 50 mm) had a significantly higher (p < 0.05) pullout force in the non-pedicle modalities in the osteoporosis group. The pedicle plays an important role in both the normal bone density group and the osteoporosis group, as revealed by analyzing the pullout force percentage contributed by the pedicle. Use of a longer screw would be a way to salvage a broken pedicle of osteoporotic vertebra.
螺钉松动导致的椎弓根断裂是一种常见的并发症，通常是由于螺钉插入的直径不足或进入骨质疏松的椎弓根所致。在这项新颖的体外研究中，我们试图通过在椎弓根断裂的情况下使用更长或更大直径的螺钉来阐明椎弓根对螺钉固定的贡献和后续的补救策略。从成熟猪身上采集了 60 个 L4 新鲜冷冻腰椎作为正常密度组（n=30），并将其脱钙作为骨质疏松组（n=30）。每组随机分为完整椎弓根（n=30）、半椎弓根（n=15）和无椎弓根（n=15）三种模式。在每种模式下，使用三种大小的多轴螺钉（直径×长度 6.0mm×45mm、6.0mm×50mm 和 6.5mm×45mm）进行了五次试验。分析了骨密度、椎弓根模式和螺钉拔出强度之间的关系。脱钙 4 周后，骨密度面积降至正常密度组的约 56%（p<0.05），将其归为骨质疏松组。在两组的拔出试验之前，使用 X 射线成像确认了合适的螺钉轨迹和插入深度。在正常密度组中，较大直径螺钉（6.5mm×45mm）和较长螺钉（6.0mm×50mm）的拔出力明显更高（p<0.05），而在骨质疏松组中，仅较长螺钉（6.0mm×50mm）在无椎弓根模式下的拔出力明显更高（p<0.05）。通过分析椎弓根对拔出力的贡献率，发现椎弓根在正常骨密度组和骨质疏松组中都起着重要作用。使用较长的螺钉将是修复骨质疏松椎弓根断裂的一种方法。
