Loss of quadriceps strength after total knee arthroplasty (TKA) is most pronounced acutely but persists long-term, negatively impacting physical function in daily activities. Neuromuscular electrical stimulation (NMES) early after surgery is an effective adjuvant to standard of care rehabilitation (SOC) for attenuating strength loss following TKA, but the mechanisms whereby NMES maintains strength are unclear. This work aimed to determine the effects of early NMES on quadriceps strength and skeletal muscle fiber size 2 weeks after TKA compared to SOC. Patients scheduled for primary, unilateral TKA were enrolled and randomized into SOC (n = 9) or NMES plus SOC (n = 10) groups. NMES was started within 48 h of TKA, with 45-min sessions twice a day for 2 weeks. Isometric quadriceps strength was assessed preoperatively and 2 weeks following TKA. Vastus lateralis muscle biopsies of the involved leg were performed at the same time points and immunohistochemistry conducted to assess muscle fiber cross-sectional area and distinguish fiber types. Groups did not differ in age, body mass index, sex distribution, or preoperative strength. Both groups got weaker postoperatively, but the NMES group had higher normalized strength. After 2 weeks, the group receiving NMES and SOC had significantly greater MHC IIA and MHC IIA/IIX fiber size compared to SOC alone, with no group differences in MHC I fiber size. These results suggest that NMES mitigates early muscle weakness following TKA, in part, via effects on fast-twitch, type II muscle fiber size. This investigation advances our understanding of how adjuvant, early postoperative NMES aids muscle strength recovery.

中文翻译：

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神经肌肉电刺激可在全膝关节置换术后早期保持肌肉力量：对肌纤维大小的影响

全膝关节置换术 (TKA) 后股四头肌力量的丧失最为明显，但会长期持续，对日常活动中的身体机能产生负面影响。手术后早期神经肌肉电刺激 (NMES) 是标准护理康复 (SOC) 的有效辅助手段，可减轻 TKA 后的力量损失，但 NMES 维持力量的机制尚不清楚。这项工作旨在确定与 SOC 相比，早期 NMES 对 TKA 后 2 周股四头肌力量和骨骼肌纤维尺寸的影响。计划接受初次单侧 TKA 的患者被纳入并随机分配到 SOC ( n  = 9) 或 NMES 加 SOC ( n = 10) 组。NMES 在 TKA 后 48 小时内开始，每次 45 分钟，每天两次，持续 2 周。在术前和 TKA 后 2 周评估股四头肌的等距强度。在同一时间点对受累腿进行股外侧肌活检，并进行免疫组化以评估肌纤维横截面积并区分纤维类型。各组在年龄、体重指数、性别分布或术前力量方面没有差异。两组术后均较弱，但 NMES 组的标准化强度更高。2 周后，与单独使用 SOC 相比，接受 NMES 和 SOC 的组的 MHC IIA 和 MHC IIA/IIX 纤维尺寸明显更大，MHC I 纤维尺寸没有组间差异。这些结果表明，NMES 部分地通过对快肌的影响来减轻 TKA 后的早期肌肉无力，II 型肌纤维大小。这项调查促进了我们对术后早期辅助 NMES 如何帮助肌肉力量恢复的理解。