Walker P S, Mai S F, Cobb A G, Bentley G, Hua J
Division of Biomedical Engineering, Royal National Orthopaedic Hospital Trust, Stanmore, UK.
J Bone Joint Surg Br. 1995 Sep;77(5):705-14.
We report the theoretical basis of a method to measure axial migration of femoral components of total hip replacements (THR). The use of the top of the greater trochanter and a lateral point on the collar of the stem, allowing for variations of up to 10 degrees rotation of the femur in any direction between successive radiographs, gave a maximum error of 0.37 mm. At a more realistic 5 degrees rotational variation, the error was only 0.13 mm. These data were confirmed in an experimental study using digitisation of points and special software. We also showed that the centre of the femoral head, the stem tip, and the lesser trochanter provided less accurate landmarks. In a second study we digitised a series of radiographs of 51 Charnley and 57 Stanmore THRs; the mean migration rates were found to be identical. We then studied 46 successful stems with a minimum follow-up of eight years and 46 stems which had failed by aseptic loosening at different times. At two years, the successful stems had migrated by a mean of 1.45 +/- 0.68 mm, but the failed cases had a mean migration of 4.32 +/- 2.58 mm (p < 0.0001). Of the successful cases 76% had migrated less than 2 mm, while in the failed group 84% had migrated more than 2 mm. For any particular case migration of more than 2.6 mm at two years had only a 5% chance of continuing success and would therefore merit special follow-up. Only 24% of the eventually successful stems showed migration at the stem-cement interface, but this had happened in every failed stem. We conclude that it would be possible to evaluate a new cemented design of femoral stem over a two-year period by the use of our method and to compare its performance against the reported known standard of the Charnley and Stanmore designs.
我们报告了一种测量全髋关节置换术（THR）中股骨组件轴向移位方法的理论基础。使用大转子顶部和柄部颈圈上的一个外侧点，在连续的X线片之间允许股骨在任何方向上有高达10度的旋转变化，最大误差为0.37毫米。在更实际的5度旋转变化情况下，误差仅为0.13毫米。这些数据在一项使用点数字化和特殊软件的实验研究中得到了证实。我们还表明，股骨头中心、柄尖和小转子提供的标志点准确性较低。在第二项研究中，我们对51例Charnley型和57例Stanmore型THR的一系列X线片进行了数字化处理；发现平均移位率相同。然后我们研究了46例成功的柄，其最短随访时间为八年，以及46例在不同时间因无菌性松动而失败的柄。在两年时，成功的柄平均移位了1.45 +/- 0.68毫米，但失败的病例平均移位了4.32 +/- 2.58毫米（p < 0.0001）。在成功的病例中，76%的移位小于2毫米，而在失败组中，84%的移位超过2毫米。对于任何特定病例，两年时移位超过2.6毫米的继续成功的可能性仅为5%，因此值得特别随访。最终成功的柄中只有24%在柄 - 骨水泥界面出现移位，但每个失败的柄都出现了这种情况。我们得出结论，使用我们的方法有可能在两年时间内评估一种新的骨水泥固定股骨柄设计，并将其性能与报道的Charnley型和Stanmore型设计的已知标准进行比较。
