The Mechanical properties of Vastus Medialis and Vastus Lateralis in Subjects with Patellofemoral Pain Syndrome
|Keywords:||電-力學延遲;黏彈特性;肌腱結構;超音波影像;負載-卸載迴圈;髕股關節疼痛症候群;electromechanical delay;viscoelasticity;tendon structures;ultrasonography;load-unload loop;patellofemoral pain syndrome||Issue Date:||2008||Abstract:||
本研究是探討髕股關節疼痛症候群患者的股內側肌與股外側肌之機械特性，所研究的機械特性包括電-力學延遲及黏彈特性。並且在回顧文獻時，發現過去的實驗在量測電-力學延遲及黏彈特性所使用的方法並不完善，而可能導致誤解。因此本研究分成三階段的實驗來逐步探討股內側肌與股外側肌之電-力學延遲及黏彈特性。第一階段的實驗中，電-力學延遲的測量是由肌電訊號的起始到力學反應的起始。然而，過去的測量方法皆是以膝伸直力量的起始當作股內側肌和股外側肌的力學反應，如此並無法獲得這兩股肌肉個別的電-力學延遲。因此本階段實驗的目的便是發展一個新的方法，可以量測股內側肌與股外側肌個別的電-力學延遲。十二位健康受試者參與本實驗，以電刺激器刺激受試者的動作點而引發肌肉抽動，同時，電刺激的訊號並聯至一定製的電路做去電流和降電壓的處理後，經由心電圖的輸入端導入超音波掃瞄儀，以做為同步之用。超音波掃瞄儀是用來擷取股內側肌或股外側肌抽動所引起的髕骨動作，測量電刺激訊號的起始到髕骨動作的起始之時間差即為電-力學延遲。實驗結果顯示以此新方法所測得的股內側肌與股外側肌電-力學延遲的重製率良好，其級內相關係數都超過0.8。股內側肌與股外側肌的電-力學延遲分別為18.3 ± 2.2 ms和24.8 ± 5.8 ms。此新的量測方法因為是以髕骨活動的起始當作股內側肌和股外側肌的力學反應，而可以比較準確的量測電-力學延遲。第二階段的實驗中，12位髕股關節疼痛症候群患者以及12位性別、年齡、身高和體重與病人受試者相當的健康者參與本實驗。將第一階段所發展的新方法應用在這些受試者上，測量他們的股內側肌與股外側肌之電-力學延遲，並加以比較兩組受試者之間的差異。實驗的結果顯示病人組的股內側肌之電-力學延遲比股外側肌大的人數比例顯著的比健康組多。根據這個結果，作者推論髕股關節疼痛症候群患者的股內側肌與股外側肌之電-力學延遲可能有適應性改變的情況。第三階段的實驗中，作者進一步探討電-力學延遲的長短與肌肉黏彈特性的關聯性。過去的學者認為電-力學延遲主要是耗費在肌肉的收縮性部分牽拉彈性串列部分。因此，電-力學延遲的長短便與肌肉的彈性串列部分之黏彈特性有關。而負載-卸載迴圈的面積大小可代表遲滯現象的大小，並與肌腱結構的黏彈特性有關。因此在此階段的實驗目的，便是測量股內側肌與股外側肌肌腱結構之負載-卸載迴圈面積大小，並加以比較兩組受試者之間的差異。此外，肌腱結構的延長是形成負載-卸載迴圈的一部分。然而在過去的實驗中，將股外側肌肌腱結構在肌肉收縮時的移動量當作延長量，如此可能造成數據上的誤差。因此作者修正過去的實驗方法，而可以比較準確的測量股內側肌與股外側肌之肌腱結構在肌肉收縮時的延長量。以等速肌力測量儀提供阻力，讓受試者施行漸進式的等長膝伸直運動，同時，記錄股內側肌與股外側肌的肌電訊號。並且以B模式的超音波影像擷取股內側肌與股外側肌之肌腱結構在用力時的延長狀況，然後以30Hz的頻率錄在磁帶中。以一定製的開關將肌電訊號和超音波影像作同步處理。實驗的結果顯示，病人組的股內側肌肌腱結構的遲滯迴圈面積大於股外側肌的人數明顯多於健康組受試者。根據這個結果，作者推論髕股關節疼痛症候群患者的股內側肌與股外側肌之黏彈特性有適應性改變的現象。患者的股內側肌在日常活動中收縮所三師的能量可能較股外側肌多，而使肌力的傳遞速率降低。因此造成股內側肌的電-力學延遲大於股外側肌，如此可能使不正常的髕骨滑行軌道更加惡化。
This dissertation was designed to investigate the mechanical properties of the vastus medialis and the vastus lateralis in patients with patellofemoral pain syndrome. In this dissertation, the mechanical properties indicated the electromechanical delay and the viscoelasticity of the tendon structures of the vastus medialis and the vastus lateralis. From the literature review, the measurements for the electromechanical delay and viscoelasticity of the vastus medialis and the vastus lateralis were questionable. Hence the study was divided into three stages for three purposes. n the first stage, the electromechanical delay of the vastus medialis and vastus lateralis is determined by measuring the interval between the time of onset of muscle activities and the time of onset of mechanical output. However, individual mechanical output of the vastus medialis and vastus lateralis cannot be obtained with the conventional method because of regarding the knee extension force as the mechanical output. Therefore, the objective of this stage study was to develop a new method for measuring the electromechanical delay of the vastus medialis and vastus lateralis individually. Twelve healthy volunteers participated in the experiment. The motor point of the target muscle was electrically stimulated to evoke a muscle twitch. Simultaneously, the electrical stimulation signal was transmitted to ultrasound apparatus via the electrocardiography input channel. The ultrasound apparatus was used to capture the patellar movement elicited by the muscle twitch. The electromechanical delay was measured from the onset of the electrical stimulation to the onset of patellar movement. The results showed that the intra-class correlation coefficients for the reproducibility of the electromechanical delay measurements of the vastus medialis and vastus lateralis were greater than 0.8. The electromechanical delay of the vastus medialis and vastus lateralis were 18.3 ± 2.2 ms and 24.8 ± 5.8 ms, respectively. This new method provides a more precise measurement of the electromechanical delay in the vastus medialis and vastus lateralis than does the conventional method because of the use of patellar movement as the mechanical output. n the second stage, twelve patellofemoral pain syndrome patients and twelve healthy subjects with gender, age, height and weight matched were recruited to participate to the study. The new method was applied to all the subjects and the resultant electromechanical delay of the vastus medialis and vastus lateralis were compared between these two groups. The result of this stage study was demonstrated that the percentage of people whose the electromechanical delay of vastus medialis being larger than that of vastus lateralis in subjects with patellofemoral pain syndrome are significantly greater than those in healthy individuals. According to the result, we speculated that the mechanical properties of vastus medialis and vastus lateralis might have adaptive changes in patients with patellofemoral pain syndrome. n the third stage, we further investigated the relationships of the length of electromechanical delay and the viscoelasticity of musculature. Previous scholars believed that the time taken for the stretching of the series elastic component by the contractile element is considered a major portion of electromechanical delay. Therefore, the viscoelasticity of the series elastic component is related to the length of electromechanical delay. The area of load-unload loop is an index of hysteresis and related to the viscoelasticity of tendon structures. Therefore, the area of load-unload loop of the vastus medialis and vastus lateralis was measured and compared between healthy individuals and patellofemoral pain syndrome patients. The elongation of the tendon structures is one part to form the load-unload loop. In previous studies, however, the measurement of the elongation of tendon structures is questionable due to the displacement of the tendon structures of vastus lateralis being measured. We would like to modify the previous method to measure the more precise elongation of the tendon structures of vastus medialis and vastus lateralis. The isokinetic dynamometer was used to provide the resistance during subject performing ramped isometric knee extension exercise; simultaneously, the muscle activities of the vastus medialis and vastus lateralis were detected by the electromyography recording system. Besides, the elongations of the tendon structures of the vastus medialis and vastus lateralis during ramped isometric contraction were captured by the B mode ultrasonography. A customized switch was used to synchronize the signals of muscle activity and the ultrasonography. The results of this stage study were showed that the percentage of people whose the area ratio of hysteresis loop of vastus medialis being larger than that of vastus lateralis in subjects with patellofemoral pain syndrome are significantly greater than those in healthy individuals. According to the result, we speculated that the viscoelasticity of vastus medialis and vastus lateralis might have a change in patellofemoral pain syndrome patients. The greater energy loss of vastus medialis contraction in daily activity and the decreased speed of muscle force transmission in patellofemoral pain syndrome patients. Consequently, the electromechanical delay of vastus medialis is smaller than that of vastus lateralis and that might deteriorate the abnormal patellar tracking.
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