Abstract
There are many diagnostic clinical tests (e.g., apprehension patellar test or the moving patellar apprehension test), outcome measures (general health and knee scales [IKDC form, Kujala scale, Fulkerson scale, Lysholm knee scoring scale, Tegner activity level scale, short form-36]), and instrumented measurements of patellar mobility (static stability), to assess lateral patellar instability.7,10,15,16 However, according to Smith and colleagues,15 the sensitivity/specificity – reliability/validity of such tests and outcome tools remain unclear for this patient population. These authors conclude that further work is needed to assess the appropriateness of these tests and outcomes.15Moreover, there are many surgical techniques to treat patients with chronic lateral patellar instability, all of them based on level of evidence IV or V.4 This is due, in part, to the lackof prospective randomized trials, and also to the lack of an objective, suitable, reliable, valid, and reproducible noninvasive in vivo method to evaluatelateral patellar instability in the clinical setting. This makes it difficult to compare different surgical treatments in order to find the best surgical technique to treat patients with chronic lateral patellar instability.
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Notes
- 1.
A force is a vectorial magnitude that can be defined as an action that tends to produce a movement of a body, which acquires an acceleration in proportion to the magnitude of the applied force. The force is defined as the product between mass and acceleration. In order to compare curves of different subjects, with different anthropometric characteristics, the force’s signals are processed normalizing the subject’s weight values.
$$ \overrightarrow{\text{F}}\text{(N)}=\text{m}\text{\hspace{0.05em}}\text{(kg)}\text{.}\overrightarrow{\text{a}}\left(\frac{\text{m}}{{\text{s}}^{\text{2}}}\right)$$ - 2.
A moment or torque is a force couple that produces a rotatory effect (Fig. 22.1). The moments are normalized due to a characteristic of a rotating body, the moment of inertia. Any body that rotates around an axis has rotation inertia, which is a resistance to change the rotation speed and the direction of the spin axis. Normalization enables us to make comparisons between subjects with different anthropometric characteristics.
$$ \overrightarrow{M}(N.\text(m)\text=\overrightarrow{F}\text(N)\times \overrightarrow{d}(m)$$ - 3.
The axial moment exerted by the subject on the platform is the sum of the product of the forces measured by the four sensors and their distance to the COP.
$$ \begin{array}{l}{M}_{r}\text=\text{\text{F}}_{\text{c1}}\times \text{\text{d}}_{\text{c1-CDP}}\text+\text{\text{F}}_{\text{c2}}\times{\text{d}}_{\text{c2-CDP}}\text+\text{\text{F}}_{\text{c3}}\times {\text{d}}_{\text{c3-CDP}}\text+\text{\text{F}}_{\text{c4}}\times \text{\text{d}}_{\text{c4-CDP}}\end{array}$$ - 4.
The relative motion of the tibia with respect to the femur is considered as either an internal or external rotation of the knee.
- 5.
Normalized moment = moment/moment of inertia
- 6.
Angular impulse is the effect of a moment acting over a period of time. It is determined by the area under the moment–time curve. The change in the moment experienced by a body under the action of a field of forces is equal to the angular impulse of the resulting moment.
- 7.
We can compare the pivoting slope with a ski run slope (Fig. 22.4). The greater the slope inclination, the higher the skier’s speed will be; and, the longer the ski run, the higher the speed reached by the skier.
- 8.
Vertical force (Fz). The push produced when one object (foot) acts on another (force plate).
- 9.
The VMO is a dynamic medial stabilizer of the patella. The VMO’s line of pull most efficiently resists lateral patellar motion when the knee is in deep flexion.
- 10.
Kinetic data from the five trials for each subject were averaged (n = 15). Student t-test was performed to compare the results between two categories of the same variable, in this case one limb versus the contralateral limb. A p < 0.05 was considered statistically significant. With the sample sizes used in our study, we obtained a statistical high power, with a significance level of 95%
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Sanchis-Alfonso, V., Baydal-Bertomeu, J.M., Montesinos-Berry, E., Castelli, A., Garrido-Jaén, J.D. (2011). Kinetic Analysis: A Sensitive Outcome Objective Measurement Method in Evaluating Lateral Patellar Instability. In: Sanchis-Alfonso, V. (eds) Anterior Knee Pain and Patellar Instability. Springer, London. https://doi.org/10.1007/978-0-85729-507-1_22
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