Hendricks Cale J, Polly David W, Abbott Ashley M, Yusuf Yaqoub Y, Garcia Rafael A, MacEwen Matthew R, Ellingson Arin M
Department of Orthopedic Surgery, University of Minnesota, Minneapolis, MN, United States.
Department of Family Medicine and Community Health, Divisions of Physical Therapy and Rehabilitation Science, University of Minnesota, Minneapolis, MN, United States.
N Am Spine Soc J. 2025 May 29;23:100623. doi: 10.1016/j.xnsj.2025.100623. eCollection 2025 Sep.
Sacroiliac joint (SIJ) fusion is a common procedure for SIJ pain and dysfunction. Traditional threaded screws offer limited bony integration, prompting the development of additively manufactured, porous implants aimed at enhancing osseointegration. However, data on their insertional mechanics and pullout strength, especially in revision scenarios, remain sparse. This study aimed to investigate the influence of bone density, tapping, and implant size on re-insertional torque and pullout strength.
Mechanical testing was conducted in accordance with ASTM F543, using 10 and 20 PCF polyurethane foam blocks to simulate low and normal-density bone, respectively. A 10 × 35 mm screw fusion device served as the control. For subsequent tests, the 10 × 35 mm screw was removed, and various diameters (10, 11.5, 13.5 mm) and lengths (35, 40, 45 mm) were reinserted under 2 conditions: direct and with tapping. The maximum and final insertional torque, as well as the maximum pullout force, were measured. ANOVA techniques with pairwise comparison and Pearson correlation tests were performed (α = 0.05).
Significant effects and interactions were observed for implant size, bone density, and tapping. Larger implant diameter and length were associated with significantly greater insertional torque and pullout strength compared to controls, though excessively large diameters yielded diminishing returns in normal-density bone. Independent of size and tapping, normal-density bone consistently demonstrated greater insertional torque (929.1 ± 6.5 vs. 235.0 ± 6.5N·cm) and pullout strength (1,331.2 ± 14.8 vs. 457.3 ± 14.6 N) than low-density bone (p < .001). Independent of size, tapping improved insertional torque (+33.9%; p < .001) and pullout strength (+108.4%; p < .001) in normal-density bone but reduced pullout strength in low-density bone (-22.4%; p < .001). Final insertional torque strongly correlated with pullout strength (r = 0.946, p < .001).
Our findings provide evidence-based insight for optimizing implant selection and surgical technique in revision SIJ fusion procedures using screw fusion devices. Particularly, it is emphasized that both implant dimensions and patient-specific bone quality must be considered to achieve stable and successful outcomes.
骶髂关节（SIJ）融合术是治疗SIJ疼痛和功能障碍的常见手术。传统的螺纹螺钉骨整合能力有限，促使人们开发增材制造的多孔植入物，旨在增强骨整合。然而，关于其插入力学和拔出强度的数据，尤其是在翻修情况下的数据仍然很少。本研究旨在探讨骨密度、攻丝和植入物尺寸对再次插入扭矩和拔出强度的影响。
根据ASTM F543进行力学测试，分别使用10和20磅每立方英尺（PCF）的聚氨酯泡沫块模拟低密度和正常密度的骨。一个10×35毫米的螺钉融合装置作为对照。在后续测试中，移除10×35毫米的螺钉，并在两种情况下重新插入不同直径（10、11.5、13.5毫米）和长度（35、40、45毫米）的螺钉：直接插入和攻丝后插入。测量最大和最终插入扭矩以及最大拔出力。进行了具有成对比较的方差分析技术和Pearson相关性测试（α = 0.05）。
观察到植入物尺寸、骨密度和攻丝有显著影响和相互作用。与对照相比，更大的植入物直径和长度与显著更大的插入扭矩和拔出强度相关，尽管在正常密度的骨中过大的直径收益递减。与低密度骨相比，无论尺寸和攻丝情况如何，正常密度的骨始终表现出更大的插入扭矩（929.1±6.5对235.0±6.5牛·厘米）和拔出强度（1331.2±14.8对457.3±14.6牛）（p <.001）。在正常密度的骨中，攻丝在不考虑尺寸的情况下提高了插入扭矩（+33.9%；p <.001）和拔出强度（+108.4%；p <.001），但在低密度骨中降低了拔出强度（-22.4%；p <.001）。最终插入扭矩与拔出强度密切相关（r = 0.946，p <.001）。
我们的研究结果为使用螺钉融合装置的翻修SIJ融合手术中优化植入物选择和手术技术提供了基于证据的见解。特别是，强调必须同时考虑植入物尺寸和患者特定的骨质量，以实现稳定和成功的结果。
