Edidin A A, Merritt P O, Hack B H, Manley M T
St Vincent's Medical Centre, Los Angeles, USA.
J Bone Joint Surg Br. 1998 Sep;80(5):869-75. doi: 10.1302/0301-620x.80b5.8670.
We describe the development and early clinical application of a ported, proximally-cemented titanium stem for cemented total hip arthroplasty. PMMA bone cement is delivered to the proximal femur under pressure after the stem has been positioned within the femoral canal. A mid-stem cement occluder contains the cement to the proximal stem only. A tapered body is incorporated in the design of the stem to reduce the structural stiffness and hence the degree of stress shielding within the reconstructed joint. We performed preclinical studies to measure the reduction in porosity and the pressurisation achieved. The porosity, as measured by the void percentage within the cured cement mantle, was reduced by more than 50% and there was an almost threefold increase in the mean pressure. Mechanical testing of the stem, using a three-point bend test, showed that the addition of cement injection ports on the anterior and posterior sides of the body of the proximal stem did not reduce its strength. Finite-element analysis indicated that, compared with a fully-cemented conventional stem, there was no change in the stresses within the cement mantle. In a series of 40 proximally-cemented stems followed for up to six years (mean 51 months) the mean Harris hip score was 91, and 85% of patients had good or excellent results. There was excellent pain relief, an increased level of activity and good patient satisfaction. One mechanical failure of the stem required revision at three years after implantation. The early results indicate that the clinical performance was equal to that achieved with other modern cemented stems. Radiological evaluation showed excellent results with no evidence of stress shielding. Further follow-up will determine if long-term stress shielding is reduced and if revision is made easier by the absence of a distal cement mantle.
我们描述了一种用于骨水泥型全髋关节置换术的带端口、近端骨水泥固定的钛柄的研发及早期临床应用。在柄置于股骨髓腔内后，聚甲基丙烯酸甲酯（PMMA）骨水泥在压力作用下被输送至股骨近端。柄中部的骨水泥封堵器仅将骨水泥限制在近端柄部。柄的设计中采用了锥形主体以降低结构刚度，从而减少重建关节内的应力遮挡程度。我们进行了临床前研究以测量孔隙率的降低情况及所实现的加压效果。通过固化骨水泥套中的孔隙百分比测量的孔隙率降低了50%以上，平均压力几乎增加了两倍。使用三点弯曲试验对柄进行力学测试表明，在近端柄体的前后侧添加骨水泥注入端口并未降低其强度。有限元分析表明，与完全骨水泥固定的传统柄相比，骨水泥套内的应力没有变化。在一组40个近端骨水泥固定柄的病例系列中，随访长达六年（平均51个月），Harris髋关节平均评分为91分，85%的患者结果良好或优秀。疼痛得到了极好的缓解，活动水平提高，患者满意度良好。有1个柄在植入三年后出现机械故障需要翻修。早期结果表明，其临床性能与其他现代骨水泥固定柄相当。影像学评估结果优异，无应力遮挡迹象。进一步的随访将确定长期应力遮挡是否减少，以及由于没有远端骨水泥套是否使翻修更容易。
