Markolf K L, Willems M J, Jackson S R, Finerman G A
Department of Orthopaedic Surgery, University of California at Los Angeles, USA.
J Orthop Res. 1998 Jul;16(4):455-63. doi: 10.1002/jor.1100160410.
The goals of this study were to (a) evaluate the differential variable reluctance transducer as an instrument for measuring tissue strain in the anteromedial band of the anterior cruciate ligament, (b) develop a series of calibration curves (for simple states of knee loading) from which resultant force in the ligament could be estimated from measured strain levels in the anteromedial band of the ligament, and (c) study the effects of knee flexion angle and mode of applied loading on output from the transducer. Thirteen fresh-frozen cadaveric knee specimens underwent mechanical isolation of a bone cap containing the tibial insertion of the anterior cruciate ligament and attachment of a load cell to measure resultant force in the ligament. The transducer (with barbed prongs) was inserted into the anteromedial band of the anterior cruciate ligament to record local elongation of the instrumented fibers as resultant force was generated in the ligament. A series of calibration curves (anteromedial bundle strain versus resultant force in the anterior cruciate ligament) were determined at selected knee flexion angles as external loads were applied to the knee. During passive knee extension, strain readings did not always follow the pattern of resultant force in the ligament; erratic strain readings were often measured beyond 20 degrees of flexion, where the anteromedial band was slack. For anterior tibial loading, the anteromedial band was a more active contributor to resultant ligament force beyond 45 degrees of flexion and was less active near full extension; mean resultant forces in the range of 150-200 N produced strain levels on the order of 3-4%. The anteromedial band was also active during application of internal tibial torque; mean resultant forces on the order of 180-220 N produced strains on the order of 2%. Resultant forces generated by varus moment were relatively low, and the anteromedial band was not always strained. Mean coefficients of variation for resultant force in the ligament (five repeated measurements) ranged between 0.038 and 0.111. Mean coefficients of variation for five repeated placements of the strain transducer in the same site ranged from 0.209 to 0.342. Insertion and removal of this transducer at the anteromedial band produced observable damage to the ligament. In our study, repeatable measurements were possible only if both prongs of the transducer were sutured to the ligament fibers.
(a) 评估差动可变磁阻传感器作为测量前交叉韧带前内侧束组织应变的仪器；(b) 绘制一系列校准曲线（针对膝关节简单加载状态），以便根据韧带前内侧束测量的应变水平估算韧带中的合力；(c) 研究膝关节屈曲角度和加载方式对传感器输出的影响。13个新鲜冷冻的尸体膝关节标本进行了手术，分离出包含前交叉韧带胫骨附着点的骨块，并连接一个测力传感器以测量韧带中的合力。将带倒刺叉的传感器插入前交叉韧带的前内侧束，在韧带产生合力时记录被测纤维的局部伸长情况。在选定的膝关节屈曲角度施加外部负荷时，测定了一系列校准曲线（前内侧束应变与前交叉韧带合力的关系）。在被动膝关节伸展过程中，应变读数并不总是与韧带中的合力模式一致；在屈曲超过20度时，常常会测得不稳定的应变读数，此时前内侧束松弛。对于胫骨前向加载，在屈曲超过45度时，前内侧束对韧带合力的贡献更大，而在接近完全伸展时则作用较小；150 - 200 N范围内的平均合力产生的应变水平约为3 - 4%。在内侧胫骨扭矩施加过程中，前内侧束也有活动；180 - 220 N左右的平均合力产生的应变约为2%。内翻力矩产生的合力相对较低，前内侧束并不总是处于应变状态。韧带合力（五次重复测量）的平均变异系数在0.038至0.111之间。应变传感器在同一部位五次重复放置的平均变异系数在0.209至0.342之间。在前内侧束插入和取出该传感器会对韧带造成明显损伤。在我们的研究中，只有将传感器的两个叉都缝合到韧带纤维上，才有可能进行可重复的测量。
