Yerby S A, Toh E, McLain R F
Veterans Affairs Rehabilitation and Research Design Center, Palo Alto, California, USA.
Spine (Phila Pa 1976). 1998 Aug 1;23(15):1657-61. doi: 10.1097/00007632-199808010-00008.
The biomechanical influence of in situ setting hydroxyapatite cement was examined for use in pedicle screw revision surgery. Pull-out testing of control and pedicle screws augmented with hydroxyapatite cement was performed in human cadaver vertebrae.
To determine the immediate effect of using hydroxyapatite cement to augment revision pedicle screws after failure of the primary pedicle screw fixation.
The potential problems associated with using polymethylmethacrylate to augment revision pedicular instrumentation have prompted the search for other solutions. The introduction of resorbable hydroxyapatite pastes may have provided new biocompatible solutions for pedicle screw revision.
Ten human cadaver vertebrae were instrumented with 6.0-mm pedicle screws in each pedicle. The screws were loaded to failure in axial tension (pull-out). The failed pedicles then were instrumented with 7.0-mm pedicle screws, either augmented with hydroxyapatite cement or nonaugmented, which also were loaded to failure. Finally, the nonaugmented 7.0-mm screw hole was reinstrumented with a hydroxyapatite cement-augmented, 7.0-mm pedicle screw and loaded to failure.
The pull-out strength of the 7.0-mm, hydroxyapatite cement-augmented screws was 325% (P = 2.9 x 10(-5)) of that of the 6.0-mm control screws, whereas the strength of the 7.0-mm nonaugmented screws was only 73% (P = 2.0 x 10(-2)) of that of the 6.0-mm control screws. The 7.0-mm screws augmented with hydroxyapatite cement also were able to salvage 7.0-mm pull-out sites to 384% (P = 6.9E-5) of the pull-out strength of the 7.0-mm nonaugmented screws.
Hydroxyapatite cement may be a mechanically viable alternative to polymethyl methacrylate for augmenting revision pedicular instrumentation and should be considered for future experimental, animal, and clinical testing.
研究原位植入羟基磷灰石骨水泥在椎弓根螺钉翻修手术中的生物力学影响。在人类尸体椎骨上对未增强的对照椎弓根螺钉和增强了羟基磷灰石骨水泥的椎弓根螺钉进行拔出试验。
确定在初次椎弓根螺钉固定失败后，使用羟基磷灰石骨水泥增强翻修椎弓根螺钉的即时效果。
使用聚甲基丙烯酸甲酯增强翻修椎弓根器械相关的潜在问题促使人们寻找其他解决方案。可吸收羟基磷灰石糊剂的引入可能为椎弓根螺钉翻修提供了新的生物相容性解决方案。
在10具人类尸体椎骨的每个椎弓根中植入6.0毫米的椎弓根螺钉。将螺钉在轴向张力（拔出）下加载至失效。然后在失败的椎弓根中植入7.0毫米的椎弓根螺钉，一种增强了羟基磷灰石骨水泥，另一种未增强，同样将它们加载至失效。最后，在未增强的7.0毫米螺钉孔中重新植入增强了羟基磷灰石骨水泥的7.0毫米椎弓根螺钉并加载至失效。
7.0毫米增强了羟基磷灰石骨水泥的螺钉的拔出强度是6.0毫米对照螺钉拔出强度的325%（P = 2.9×10⁻⁵），而7.0毫米未增强螺钉的强度仅是6.0毫米对照螺钉强度的73%（P = 2.0×10⁻²）。增强了羟基磷灰石骨水泥的7.0毫米螺钉还能够将7.0毫米拔出部位的强度恢复到7.0毫米未增强螺钉拔出强度的384%（P = 6.9E - 5）。
对于增强翻修椎弓根器械，羟基磷灰石骨水泥在力学上可能是聚甲基丙烯酸甲酯的可行替代物，应考虑在未来进行实验、动物和临床试验。
