骨水泥外套开裂对股骨假体柄微动和松动的影响：附18例骨水泥型假体尸体标本观察(英文)

Role of mantle cracks in the loosening and micromotion of cemented femoral stems——Analysis of autopsy material of 18 cemented femoral stems

背景:无菌性松动是骨水泥型人工髋关节置换后失败的主要原因,从骨水泥型假体患者尸体标本研究中探讨其发病机制对于预防松动具有重要意义。目的:通过对骨水泥型假体患者尸体标本研究,旨在验证作者的推测:骨水泥的开脱和假体柄的微动与骨水泥固定失败相关,骨水泥外套的开裂预示着骨水泥型假体无菌性松动。设计、时间及地点:观察性实验,于2003-05/11在美国贝勒医学院骨科研究所完成。对象:18例带有骨水泥假体柄股骨标本是从18例原先行髋关节置换的遗体捐献者体内获得。这些遗体来源于美国贝勒医学院解剖系。包括男7例,女11例。方法:18例带有骨水泥假体柄的股骨标本在假体柄下3cm处切断股骨,将标本浸泡在含有茜蓝素染色剂的溶液中,用真空泵抽吸股骨24h染色。电锯将每个股骨标本沿矢状面两侧对称剖开,首先在显微镜下测量假体柄与骨水泥间隙,取出假体柄后,显微镜下观测骨水泥内面的开裂和磨损情况。用立体光学显微镜在3个等距离位置测量骨水泥开裂的宽度。同时记录假体柄磨损情况,按Gruen分区记录。主要观察指标:假体柄与骨水泥间隙的宽度,骨水泥外套内面开裂的位置和宽度,骨水泥外套内面磨损的区域和假体柄磨损的区域。结果:几乎所有假体柄都从骨水泥外套中开脱,16例标本骨水泥内面都有轻微磨损,15例标本骨水泥内面有开裂,而开裂的位置大多在假体柄与骨水泥的转角处(87%,P=0.002)。无假体柄下沉超过0.5mm,假体柄与骨水泥外套间裂隙平均宽度(0.33±0.06)mm,每一标本的骨水泥外套纵向开裂的平均宽度和假体柄与骨水泥外套间的裂隙平均宽度呈正相关(r2=0.691,P=0.001)。结论:在临床成功的骨水泥型人工关节置换患者中,骨水泥开裂是较常见的一种现象。骨水泥开裂一旦发生,假体柄就会出现微动。通常骨水泥开裂并不一定会导致假体无菌性松动,但随着微动产生的磨损微粒泵入骨床中而产生骨溶解最终会导致假体的松动。

BACKGROUND： Aseptic loosening has been identified a main failure mechanism of cemented total hip arthroplasty. It is very important to prevent loose by exploring its pathogenesis in studies of corpse specimens with bone cement prosthesis. OBJECTIVE： In this cadaveric retrieval study, we examined the hypotheses that debonding and stem migration were associated with mechanical failure of the cement mantle, and that cracking of the mantle was indicative of aseptic loosening of cemented femoral stems. DESIGN, TIME AND SETTING： Observation experiment. The study was performed at Baylor college of Medicine and the Institute of Orthopedic Reseamh, Houston, TX, USA between May and November 2003 PARTICIPANTS： A total of 18 femurs with cemented femoral stems were obtained from cadaveric donors in Department of Anatomy, Baylor College of Medicine at Houston, including 7 males, 11 females. METHODS： Eighteen cadaveric femurs with cemented femoral stems were cut from suitable area and immersed in a bath of Alcaim Blue pigment under vacuum for 24 hours to staining. Each femur was bilateral along the sagittal mid-plane and examined with stereomicroscopy to identify cracks within the cement mantle and recorded by Gruen zone. The widths of cracks present on the inner surface of the mantle were measured at three equidistant locations with an instrumented microscope system. The widths of gaps along the stem/cement interface were measured by reassembling its corresponding cement mantle. Any regions of burnishing of the inner surface of the cement mantle and the stem surface were recorded too. MAIN OUTCOME MEASURES： The following parameters were measured： location, width of cracks inner surface of the mantle; widths of gaps along the stern/cement interface; regions of burnishing of the inner surface of the cement mantle and the stem surface. RESULTS： Almost all components were debonded from the surrounding cement mantle. Slight burnishing of the inner surface of the cement mantle was evident in sixteen （89%） specimens. Cracks were present in fifteen （83%） of mantles, frequently corresponding to areas where the comers of the stem had come into contact with bone during implantation, （87%, P = 0.002）. None of the stems had subsided by more than 0.5mm. The average width of gaps between the stem and the cement mantle was （0.33±0.06） ram. There was a strong correlation between the minimum width of longitudinal cracks and the average stem/cement gap for each specimen （r^2=0.691, P= 0.001）. CONCLUSION： Cement cracks are frequently observed in clinically successful cemented hip replacements. Stern migration occurs once cement fractures open. Cement cracks do not necessarily result in clinical failure of cemented stems. But, with the development of micromotion, the debris cause osteolysis and might affect implant stability and lead to harmful effects on the bone bed and subsequent loosing of the implant.