Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
J Shoulder Elbow Surg. 2013 May;22(5):709-15. doi: 10.1016/j.jse.2012.07.001. Epub 2012 Sep 21.
Porous-tantalum (PT)-backed glenoid components have recently been developed to improve fixation and minimize the incidence of glenoid component loosening, which remains a key limiting factor in long-term survival in total shoulder arthroplasty. PT-backed glenoids promote bony ingrowth as a method of preventing glenoid loosening at the prosthesis-glenoid interface. The use of polymethyl-methacrylate (PMMA) cement for initial fixation may prevent osteointegration due to mechanical occlusion of the porous surface and the nonosteoconductive properties of PMMA. This study aims to investigate alternative fixation methods of PT-backed glenoids in a biomechanical investigation.
Nine PT-backed monoblock glenoid components were implanted in a polyurethane bone substitute using either press-fit, PMMA cement, or calcium phosphate cement techniques. A control group of 3 all-polyethylene pegged glenoid components was implanted with PMMA. Glenoid and humeral head components were fixed to a biomechanical testing machine for testing according to ASTM Standard F-2028. The humeral head was translated ±1.5 mm along the superior-inferior axis for 50,000 cycles for characterization of glenoid rocking and inferior-superior translation.
Glenoid compression and glenoid distraction followed similar patterns for PT-backed glenoids. Overall, the all-polyethylene cemented glenoid demonstrated superior fixation compared to all PT-backed groups throughout the test. Glenoids fixed with PMMA cement displayed more favorable initial fixation and resistance to glenoid motion throughout cyclic testing.
This study showed that among PT-backed glenoids, PMMA fixation provided an increase in stability during initial and final cycles compared to press-fit and calcium-phosphate fixation techniques. This improved stability may enhance the osteointegration of the implant.
多孔钽（PT）背衬肩胛盂假体最近已被开发出来，以改善固定并降低肩胛盂假体松动的发生率，这仍然是全肩关节置换术长期生存的关键限制因素。PT 背衬肩胛盂通过促进骨长入来防止假体-肩胛盂界面处的肩胛盂假体松动。由于多孔表面的机械阻塞和 PMMA 的非骨传导特性，最初使用聚甲基丙烯酸甲酯（PMMA）水泥进行固定可能会阻止骨整合。本研究旨在通过生物力学研究调查 PT 背衬肩胛盂的替代固定方法。
使用压配、PMMA 水泥或磷酸钙水泥技术将 9 个 PT 背衬整体式肩胛盂假体植入聚氨酯骨替代物中。将 3 个全聚乙烯钉状肩胛盂假体植入 PMMA 作为对照组。根据 ASTM 标准 F-2028，将肩胛盂和肱骨头组件固定在生物力学试验机上进行测试。为了描述肩胛盂摇摆和下上平移，使肱骨头沿上下轴 ±1.5mm 平移 50000 次。
PT 背衬肩胛盂的肩胛盂压缩和肩胛盂分离呈现出相似的模式。总体而言，在整个测试过程中，全聚乙烯水泥固定的肩胛盂比所有 PT 背衬组都具有更好的固定效果。在整个循环测试过程中，用 PMMA 水泥固定的肩胛盂表现出更好的初始固定和对肩胛盂运动的抵抗力。
本研究表明，在 PT 背衬肩胛盂中，与压配和磷酸钙固定技术相比，PMMA 固定在初始和最终循环中提供了更高的稳定性。这种稳定性的提高可能会增强植入物的骨整合。
