Nègre J, Henry F
Rev Chir Orthop Reparatrice Appar Mot. 1995;81(2):106-13.
The failures of cemented hip prosthesis have prompted research into a new process of fixation and a new design of the system. Stability is achieved by adherence the bone onto a blasted titanium surface. The shell is implanted without screws. The stem has an anatomical shape to improve metaphyseal fixation of the femur.
The rugosity of the blasted titanium surface which has an average depth of 50 millimicrons allows new bone-growth without any fibrous interposition. Bone ingrowth starts from the third week onward and within two years a homogenous bone sheath is produced. Several experiments on animals have shown the quality of the bone-growth onto this blasted surface. The bone reaction has the same qualities as a hydroxy-apatite coating. It is of better quality than other titanium surfaces. The press-fit obtained by the shape allows this bone-growth. The reliability of this biological fixation is enabled for the shell by the perfect distribution of loads due to the hemispherical shape and the greatest possible thickness of the polyethylene. For the stem, the purely metaphyseal fixation appears to be a very important factor to enable painless long term stability. Another advantage of this method of fixation is that the prosthesis can be removed without any damage to the bone and can be reimplanted without any artificial fixtures with excellent results.
Histological results. Within a few weeks a new strip of bone will settle onto the porous metal without any fibrous interposition. This strip is connected to the cortical bone by small brackets of bone which gradually thicken over the months and guarantee anchorage. Radiological results. In 1 per cent of all cases a border or a gap has formed around the shell; there is no migration. Around the proximal part of the stem thin ribs in tension appeared at the beginning and over the months the width of these increased. Within two years they had filled the space between the metal and the cortical bone. Around the distal part of the stem, which is smooth, there is no bone-growth. Clinical results. In nearly 94 per cent of cases a perfect result was obtained which could only be achieved if the prosthesis was perfectly stable. There was mild pain in only 4 per cent of cases. Revision and observation. Two revisions for ceramic head fracture confirmed that it was possible to remove the prosthesis without damage to the bone.
A correct pressure distribution on bone would appear desirable for the two components. For the acetabulum a thick layer of polyethylene and for the stem a metaphyseal anchorage are desirable.
It is perhaps too early at this stage to speculate on the long term results. Nevertheless as of now we observe that the principle of a metaphyseal fixation significantly decreases the incidence of mild pain. On the other hand, the follow-up of nearly seven years of bone fixation on a blasted titanium surface would seem sufficient to show us that this method has proven to be a significant improvement.
骨水泥型髋关节假体的失败促使人们对一种新的固定方法和系统新设计展开研究。通过将骨附着在喷砂处理的钛表面来实现稳定性。髋臼杯无需螺钉植入。股骨柄具有解剖形状以改善股骨干骺端的固定。
喷砂处理的钛表面粗糙度平均深度为50毫微米，可实现新骨生长且无任何纤维组织介入。骨长入从第三周开始，两年内会形成均匀的骨鞘。多项动物实验已证明在该喷砂表面的骨生长质量。骨反应与羟基磷灰石涂层具有相同特性，质量优于其他钛表面。形状所产生的压配可促进这种骨生长。由于半球形形状和聚乙烯尽可能大的厚度，髋臼杯通过载荷的完美分布实现了这种生物固定的可靠性。对于股骨柄，单纯的干骺端固定似乎是实现无痛长期稳定性的一个非常重要的因素。这种固定方法的另一个优点是假体可以在不损伤骨的情况下取出，并且可以在无需任何人工固定装置的情况下重新植入，效果良好。
组织学结果。几周内，一条新的骨带会沉积在多孔金属上，无任何纤维组织介入。这条骨带通过细小的骨支架与皮质骨相连，这些支架在数月内逐渐增厚并确保锚固。放射学结果。在所有病例的1%中，髋臼杯周围形成了边界或间隙；但无移位。在股骨柄近端周围，起初出现了张力性细骨嵴，数月内其宽度增加。两年内它们填充了金属与皮质骨之间的间隙。在股骨柄光滑的远端周围，无骨生长。临床结果。在近94% 的病例中获得了完美结果，只有假体完全稳定才能实现这一结果。仅4% 的病例有轻微疼痛。翻修与观察。两次因陶瓷头骨折进行的翻修证实，可以在不损伤骨的情况下取出假体。
对于这两个部件，在骨上实现正确的压力分布似乎是可取的。对于髋臼，需要一层厚的聚乙烯；对于股骨柄，需要干骺端锚固。
现阶段推测长期结果可能为时过早。然而，截至目前我们观察到，干骺端固定原则显著降低了轻微疼痛的发生率。另一方面，对喷砂钛表面骨固定近七年的随访似乎足以表明，这种方法已被证明有显著改进。
