ABSTRACT

Purpose/Aim: Skeletal muscle architecture is a primary determinant of function. Volumetric muscle loss (VML) injury is destructive; however, the impact on muscle architecture is uncharacterized.

Methods: Architectural and functional effects of VML were assessed in rat tibialis anterior (TA) muscle model 4 weeks post-injury.

Results: VML caused a 31% and 33% reduction in muscle weight (p < 0.001) and fiber length (p = 0.002), respectively, culminating a 34% reduction of fiber to muscle length ratio (FL:ML; p < 0.001). Fiber pennation angle (+14%; p = 0.150) and physiological cross-sectional area (PCSA; −12%; p = 0.220) were unchanged. VML injury reduced peak isometric force (P_o) by 36% (p < 0.001), specific force (sP_o = P_o/PCSA) by 41% (vs. P_o, p > 0.999), and force per gram muscle weight (P_o/mw) by 18% (vs. P_o, p < 0.001). VML injury increased the length at which P_o was produced (L_o) by 8% (p = 0.009), and reduced functional excursion by 35% (p = 0.035).

Conclusion: The architectural changes after VML injury preserved PCSA, and therefore preserved “potential” maximal force-producing capacity. At most, only half the P_o deficit was due directly to the cumulative effect of horizontal and longitudinal tissue loss. Highlighting the impact of longitudinal muscle loss, VML injury reduced fiber length, and FL:ML and grossly disrupted length-dependent functional properties. These findings raise the importance of augmenting length-dependent muscle properties to optimize functional recovery after VML injury.

摘要

目的/目的：骨骼肌结构是功能的主要决定因素。体积性肌肉损失 (VML) 损伤是破坏性的；然而，对肌肉结构的影响是无特征的。

方法：在损伤后 4 周的大鼠胫骨前肌 (TA) 肌肉模型中评估 VML 的结构和功能影响。

结果：VML 分别导致肌肉重量 ( p < 0.001) 和纤维长度 ( p = 0.002) 分别减少 31% 和 33% ，最终使纤维与肌肉长度的比率减少 34% (FL:ML; p < 0.001) . 纤维羽化角 (+14%; p = 0.150) 和生理横截面积 (PCSA; -12%; p = 0.220) 没有变化。VML 损伤使峰值等长力 (P _o ) 降低了 36% ( p < 0.001)，比力 (sP _o  = P _o /PCSA) 降低了 41%（与 P _o，p > 0.999）以及每克肌肉重量的力(P _o /mw) 增加 18%（相对于 P _o, p < 0.001)。VML 损伤使产生P _o的长度(L _o ) 增加了 8% ( p = 0.009)，并减少了 35% ( p = 0.035) 的功能性偏移。

结论：VML 损伤后的结构变化保留了 PCSA，因此保留了“潜在”的最大力量产生能力。最多只有一半的 P _o赤字直接归因于水平和纵向组织损失的累积效应。突出纵向肌肉损失的影响，VML 损伤减少了纤维长度，FL:ML 和严重破坏了长度依赖的功能特性。这些发现提高了增加长度依赖性肌肉特性以优化 VML 损伤后功能恢复的重要性。