Pritchett James W
Seattle, WA, USA.
Ann Jt. 2022 Jul 15;7:23. doi: 10.21037/aoj-21-7. eCollection 2022.
An unconstrained tripolar hip replacement matches a large capacity two-piece metal/polyethylene acetabular component with a bipolar prosthesis. This combination of accepted technology is different than the relatively new dual mobility prosthesis. The goal is to protect against dislocation and allow close to a normal range of motion (ROM). So far there has not been enough information about wear and performance of tripolar hip replacement to support its wide use.
Twenty-four tripolar prostheses were retrieved from 23 patients after a mean of 14 years (range, 5-21 years). All implants had been placed in high-demand patients who participated in adventure sports, had occupations where a dislocation would be dangerous, or in patients undergoing revision. The tripolar prosthesis has three important design features: (I) the acetabular component uses highly cross-linked polyethylene with an internal diameter of 41-54 mm, (II) the bipolar is titanium nitride-coated, and (III) the bipolar prosthesis has positive eccentricity. The retrievals were evaluated for wear, performance, and mechanical function.
The total volumetric wear was 24 mm/yr. compared to 54 mm/yr. For a dual mobility prosthesis and 38 mm/yr. for a 40 mm conventional hip replacement. The jump distance was 16 mm compared to 12 mm for a 36 mm hip replacement. There was no osteolysis. The combined flexion/extension was 145 compared to 119 for a conventional prosthesis. The mean UCLA score was 7.9. Radiographs showed continued shared movement between the inner and outer articulations. The prosthetic bipolar separation force was 2,180 N. High-demand activities generate approximately 340 N.
The wear of this tripolar hip prosthesis is low below the osteolytic threshold. The increased ROM and increased jump distance provide the most stable unconstrained hip replacement available. The wear and mechanical performance seen in this study suggest a lifetime of use is possible in even the highest demand patients. The absence of intraprosthetic dislocation, metal wear reaction, and limited acetabular stress shielding make this a safer technology compared to a dual mobility prosthesis.
无约束三极髋关节置换术将大容量两件式金属/聚乙烯髋臼组件与双极假体相匹配。这种公认技术的组合与相对较新的双动假体不同。其目标是防止脱位并允许接近正常的活动范围（ROM）。到目前为止，关于三极髋关节置换术的磨损和性能的信息还不足以支持其广泛应用。
从23例患者中取出24个三极假体，平均使用时间为14年（范围为5 - 21年）。所有植入物均放置于高需求患者体内，这些患者参与冒险运动、从事脱位会很危险的职业或接受翻修手术。三极假体有三个重要设计特点：（I）髋臼组件使用内径为41 - 54毫米的高度交联聚乙烯；（II）双极假体涂有氮化钛；（III）双极假体有正偏心率。对取出的假体进行磨损、性能和机械功能评估。
总体积磨损为每年24毫米，相比之下，双动假体为每年54毫米，40毫米传统髋关节置换术为每年38毫米。跳跃距离为16毫米，相比之下，36毫米髋关节置换术为12毫米。未出现骨溶解。屈伸联合角度为145度，相比之下，传统假体为119度。加州大学洛杉矶分校（UCLA）平均评分为7.9分。X线片显示内外关节之间持续存在共同运动。假体双极分离力为2180牛。高需求活动产生的力约为340牛。
这种三极髋关节假体的磨损低于骨溶解阈值。活动范围增加和跳跃距离增加使其成为现有最稳定的无约束髋关节置换术。本研究中观察到的磨损和机械性能表明，即使是需求最高的患者也可能终身使用。与双动假体相比，无假体脱位、金属磨损反应且髋臼应力屏蔽有限，使得该技术更安全。
