Flex pivot

Several of the early low-resolution FT-IR spectrometers sold by Nicolet incorporated flex-pivot drives, and the interferometer made by Midac has a porch-swing drive by which a resolution of up to 0.5 cm can be achieved [7]. The major... 

Figure 5.4. Principle of operation of a flex-pivot bearing. The curved arrows indicate rotation of one section relative to the other. (Reproduced from [5], by permission of John Wiley Sons, Ltd. copyright 2002.)...

The pivot-shift phenomenon [9, 31], which consists of a tibial anterior dislocation and a subsequent reduction of lateral compartment of the knee joint, is a dynamic instability [3, 9]. Losee reported the pivot-shift test in which the hip was abducted and the knee was passively flexed from full extension with internal tibial torque, axial load, and valgus stress applied manually to induce the pivot-shift phenomenon (Eig. 11.3) [3]. The pivot-shift test is usually positive in ACL-deficient knees but sometimes positive in ACL-reconstructed knees in which anterior stability has been successfully restored. The pivot-shift test has been reported to be associated with subjective symptoms and knee functions [32] therefore, this test has been considered as an important test to assess knee stability. The grade of the pivot-shift phenomenon can be graded by the examiner subjectively as none (—), glide (+), clunk (++), or gross (+++) according to the International Knee Documentatimi Committee (IKDC) form (Table 11.2) [33]. 

Fig. 11.3 The pivot-shift test the hip was abducted and the knee was passively flexed fi-om full extension with internal tibial toque, axial load, and valgus stress applied manually to induce the pivot-shift phenomenon...

Posterior tibia reduction (PTR) is suddenly observed as the knee is passively flexed during the pivot shift test. This sudden reduction of the tibia plateau is the pivot shift phenomenon, and the PTR can be calculated using the navigation system... 

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