背景：
過度使用引起肱骨外上髁炎，其表現為疼痛、無力和難以操作物品。儘管病患的最大握力可能受損，但目前對於慢性側肱骨外上髁炎（CLE）患者的動態力量調節與神經肌肉控制機制，仍然所知有限。常用的輔助增生治療方法包括：血小板富血漿（PRP）和葡萄糖注射，雖然對患者潛在有益，也缺乏相關神經肌肉生理的證據直接支持。本研究探討CLE患者在增加、釋放力量的神經肌肉控制與健康對照組的差異，並評估CLE患者後續接受PRP和葡萄糖注射12週之後的療效差異。
方法：
本研究第一部分，共有15名CLE患者（男性10名，女性5名，年齡46.5 ± 6.3歲）和15名健康受試者（男性9名，女性6名，年齡45.3 ± 2.5歲）參與了該研究。本研究的目的是比較CLE患者和健康對照組之間在力量精確控制和相應神經肌肉機制方面的差異。實驗測量握力強度、腕伸屈最大自願收縮用力程度（MVC），並在受試者執行帶有梯形目標的指定力量跟蹤任務(trapezoidal force-tracking)時，記錄橈骨短肌（ECRB）和橈骨長肌（ECRL）表面肌電圖後解離獲得運動單元（MUs）的激發間隔（inter-spike interval, ISI）以及力量變異性動力學(force fluctuation dynamics)。本研究第二部分，共有64名符合慢性肘部外側骨炎患者參與（18名接受葡萄糖注射，19名接受PRP注射，25名健康對照組；由於表面肌電圖後解離肌肉單位效果不佳，葡萄糖和PRP組中各有1名參與者被移除）。研究第二部份的目標是比較PRP和葡萄糖注射在治療CLE方面的效果，特別關注對肘伸直的力量調節和ECRB運動單位活化的治療效果；研究假設在治療12週後，PRP將比葡萄糖更有效，能更好地改善失利調控與恢復運動單元調節能力。
結果：
本研究第一部分結果顯示：相較於健康受試者，CLE患者展現較小的腕部伸展的最大自願收縮（MVC）。在梯形施力跟蹤任務中，相較於對照組，患者在力量增加過程中表現出顯著較高的任務錯誤（p = 0.007）和力量變異性（p = 0.001）。然而，在力量釋放過程中未觀察到顯著的組別相關差異（p > 0.05）。在力量增加過程中，ECRB和ECRL肌肉的運動單位動作電位振幅在患者中較健康對照組小（p < .001）。此外，患者表現出較低的運動單元激發間隔變異性（p < .001），而患者ECRB肌肉的運動單元的平均激發間隔較正常人更大（p < .001）。
本研究第二部分結果顯示：PRP組和葡萄糖組在注射後12週之後，對超音波分級、DASH、PRTEE和VAS分數的成效相似。僅有PRP組在後測中表現出MVC顯著增加以及在腕部伸展力量增加過程出現更好的力量波動控制。力量釋放控制在兩組中都未顯著改善。進行治療後，PRP組在ECRB肌肉中激活更多具較高徵召閾值的運動單元（MUs）並提升較低徵召閾值運動單元的激發頻率，此有助於更有效地增加力量，而葡萄糖組更傾向於僅增加具有較高徵召閾值運動單元的激發頻率。
結論：
肱骨慢性外髁炎患者在力量增加方面的受損比力量釋放更為顯著。這些力量調節缺失與無法良好融合肌肉抽動力量、殘餘較小運動單元的激發頻率減緩、橈骨短肌（ECRB）較大運動單元的退化有關，肱骨慢性外髁炎患者的運動單元行為與動物實驗建構的疼痛模型預測不一致。此外，PRP可能比葡萄糖在改善ECRB肌肉的神經肌肉控制方面更為有效，特別是在改善腕部伸展期間的力量調節，此與不同增生治療引發的運動單元激活策略復原的差異有關。本研究顯示: PRP注射可能在改善力量控制和CLE患者組織結構更快恢復方面具有卓越的效果。肱骨慢性外髁炎的康復訓練計劃中，強調不僅恢復最大力量，還要在廣泛的力量範圍內，進行精確施力調節的重要性。

Background: Chronic lateral epicondylitis (CLE), often caused by overuse, manifests with symptoms including pain, weakness, and difficulty in handling objects. While it's well-known that patients with CLE experience a reduction in peak grip strength, there's limited understanding of their dynamic strength scaling and the underlying neuromuscular mechanisms. Prolotherapy treatments, such as PRP and dextrose injections, are commonly used to benefit CLE patients. However, there's a lack of sufficient neuromuscular evidence to support these treatments. This study aimed to investigate neuromuscular control and the clinical implications of force increase and release in CLE patients. Additionally, it sought to evaluate the effects of PRP and dextrose injections before and after a three-month injection period.
Methods: Methods: In the first part of this study, we aimed to compare the differences in force precision control and the corresponding neuromuscular mechanisms between patients with chronic lateral epicondylitis (CLE) and healthy individuals. Fifteen CLE patients (10 men, 5 women, average age 46.5 ± 6.3 years) and fifteen healthy subjects (9 men, 6 women, average age 45.3 ± 2.5 years) participated. We measured power grip strength, maximal voluntary contraction (MVC) of wrist extension, inter-spike intervals (ISI) of motor units (MUs) in the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) muscles, and force fluctuation dynamics while participants performed a designated force tracking task with a trapezoidal target.
In the second part of the study, we enrolled a total of 64 participants with chronic lateral epicondylitis (CLE). Of these, 18 received dextrose injections, 19 received PRP injections, and 25 were healthy controls. One participant from each of the dextrose and PRP groups was excluded due to poor decomposition results of motor units with surface EMG. The objective was to compare the efficacy of PRP and dextrose injections in treating CLE, with a specific focus on assessing the treatment's effect on force scaling and motor unit activity in the ECRB muscle. We hypothesized that PRP would be more effective than dextrose, leading to superior force scaling and recovery of motor unit regulation after 12 weeks of treatment.
Results: In the first part of this study, when comparing CLE patients to healthy participants, the patients exhibited a smaller MVC of wrist extension. During the trapezoidal force tracking task, the patient group exhibited significantly higher task errors (p = 0.007) and force fluctuations (p = 0.001) compared to the h group during force increase. However, there were no significant group-related differences in tracking performance during force release (p > 0.05). During force increase, the amplitude of the motor unit action potential in the ECRB and ECRL muscles was smaller in patients than in healthy controls (p < .001). Additionally, patients showed lower ISI variability (p < .001), and the mean ISI of MUs in the ECRB was also greater in patients (p < .001).
In the second part of this study, the PRP and dextrose groups after 12 weeks post-injection had similar outcomes on sonographic grading, DASH, PRTEE, and VAS scores. However, only the PRP group demonstrated a significant increase in MVC and better control of force fluctuations during the increasing force of wrist extension in the post-test. Force releasing control did not significantly improve in either group. After treatment, the PRP group activated more motor units (MUs) with higher recruitment thresholds and a higher discharge rate of MUs with lower recruitment thresholds in the ECRB muscle, which contribute to more effective force increase, in contrast to the dextrose group who simply favored increase in discharge rate of MUs with higher recruitment thresholds.
Conclusion: Individuals with CLE displayed more pronounced impairments in force increase compared to force release. These deficits in force regulation are associated with challenges in fusing twitch forces, slower firing rates of remaining smaller motor units (MUs), and degenerative changes in larger MUs of the extensor carpi radialis brevis (ECRB) muscle. These findings contrast with the predictions of the experimental pain model, which might be more suitable for explaining acute pain. Platelet-rich plasma (PRP) treatment is more effective than dextrose in enhancing neuromuscular control of the ECRB muscle, particularly in improving force scaling during wrist extension, likely due to distinct motor unit activation strategies. These results underscore the importance of a comprehensive rehabilitation plan for tennis elbow, focusing not only on the recovery of maximal force but also on precise regulation across a wide range of force increments. PRP injections may offer superior benefits in terms of force control and expedited tissue structure recovery in CLE patients.

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