Martinelli L, Hurschler C, Rosenbaum D
Motion Analysis Laboratory, University Hospital Muenster, Muenster, Germany.
Clin Orthop Relat Res. 2006 Jun;447:214-20. doi: 10.1097/01.blo.0000218730.59838.6a.
Cartilage contact stress elevations might be associated with pain or other symptoms after malunited, incongruous intraarticular fractures. Studies identifying fractures with patterns of elevated contact stresses would help to ensure more appropriate choices of treatment. However, appropriate instrumentation for such studies is crucial. We tested two such systems, one capacitive and one resistive, under identical loading conditions presumed to occur in the ankle. We used a materials testing machine and customized-loading fixtures to measure force detection error, contact area error, repeatability, homogeneity, creep, and one-axis and two-axis bending artifacts. The loading regimen caused pressures up to 2.5 MPa. An error in force detection between -3% and +5% was observed with the capacitive sensor whereas an error between -12% and +20% was observed with the resistive sensor. Repeatability and homogeneity were greater for the capacitive sensor. Errors in contact area measurement were less than 2% for the resistive sensor and less than 6% for the capacitive sensor. The resistive sensor could not conform to spherical surfaces without crinkling. Creep artifact was observed with both sensors. We concluded that the capacitive sensor had superior performance even though its thickness and high compliance may be disadvantageous in intraarticular measurements. The resistive sensor is required for use where higher pressures are expected despite its inferior accuracy.
关节内骨折畸形愈合且不匹配后，软骨接触应力升高可能与疼痛或其他症状相关。识别具有接触应力升高模式的骨折的研究将有助于确保更合适的治疗选择。然而，用于此类研究的合适仪器至关重要。我们在假定发生于踝关节的相同加载条件下测试了两种这样的系统，一种是电容式的，一种是电阻式的。我们使用材料试验机和定制加载夹具来测量力检测误差、接触面积误差、重复性、均匀性、蠕变以及单轴和双轴弯曲伪影。加载方案产生的压力高达2.5兆帕。电容式传感器的力检测误差在-3%至+5%之间，而电阻式传感器的误差在-12%至+20%之间。电容式传感器的重复性和均匀性更好。电阻式传感器的接触面积测量误差小于2%，电容式传感器的误差小于6%。电阻式传感器在不产生褶皱的情况下无法贴合球形表面。两种传感器均观察到蠕变伪影。我们得出结论，电容式传感器具有卓越的性能，尽管其厚度和高柔顺性在关节内测量中可能不利。尽管电阻式传感器精度较差，但在预期压力较高的情况下仍需要使用。
