Maxwell L C, Moody M R, Enwemeka C S
Department of Physiology, University of Texas Health Science Center, San Antonio 78284-7756.
Anat Rec. 1992 Jul;233(3):376-86. doi: 10.1002/ar.1092330305.
We studied soleus (SOL), plantaris (PLN), and gastrocnemius (GST) muscles to determine whether early cast removal minimizes muscle atrophy or permits recovery from atrophy after tendon repair. After right tendocalcaneus (Achilles tendon) was transected and repaired, rabbit right hindlimbs were immobilized with the ankle plantar flexed and the knee flexed to 90 degrees. Rabbits were maintained in the cast and sacrificed at 5, 15, or 21 days postoperatively or the cast was removed on day 5 and the animals sacrificed at day 15 or 21. SOL, PLN, and GST muscles of both limbs were removed and weighed, and then histochemical analyses were performed on SOL and PLN muscles. Immobilization decreased SOL muscle wet weights, mean fiber cross-sectional area, and percentage of Type I fibers and increased the percentage of Type IIc fibers. Ten days after cast removal (i.e., postoperative day 15), SOL muscle atrophy and fiber composition did not differ significantly from continuously immobilized controls. However, 16 days after cast removal (i.e., postoperative day 21), SOL muscle fiber cross-sectional area and fiber composition were near normal, differing significantly from continuously casted controls. At each of the time intervals studied, PLN (containing many glycolytic fibers) did not atrophy as much as SOL (containing mainly oxidative fibers). Our results indicate that 1) early cast removal prevents atrophy of PLN glycolytic fibers, but not oxidative fibers in either PLN or SOL, and 2) early cast removal promotes recovery from atrophy of both oxidative and glycolytic fibers. In spite of the many differences between rabbits and humans, these findings suggest that, although early cast removal may not prevent oxidative muscle fiber atrophy after postoperative immobilization, it may facilitate recovery from atrophy.
我们研究了比目鱼肌（SOL）、跖肌（PLN）和腓肠肌（GST），以确定早期去除石膏是否能使肌肉萎缩最小化，或在肌腱修复后使肌肉从萎缩中恢复。在右侧跟腱切断并修复后，将兔右后肢固定，踝关节跖屈，膝关节屈曲至90度。将兔子固定在石膏中，在术后5天、15天或21天处死，或者在第5天去除石膏，在第15天或21天处死动物。取出双下肢的SOL、PLN和GST肌肉并称重，然后对SOL和PLN肌肉进行组织化学分析。固定导致SOL肌肉湿重、平均纤维横截面积和I型纤维百分比降低，IIc型纤维百分比增加。去除石膏10天后（即术后第15天），SOL肌肉萎缩和纤维组成与持续固定的对照组相比无显著差异。然而，去除石膏16天后（即术后第21天），SOL肌肉纤维横截面积和纤维组成接近正常，与持续石膏固定的对照组有显著差异。在研究的每个时间间隔，PLN（含有许多糖酵解纤维）萎缩程度不如SOL（主要含有氧化纤维）。我们的结果表明：1）早期去除石膏可防止PLN糖酵解纤维萎缩，但不能防止PLN或SOL中的氧化纤维萎缩；2）早期去除石膏可促进氧化纤维和糖酵解纤维从萎缩中恢复。尽管兔子和人类之间存在许多差异，但这些发现表明，虽然早期去除石膏可能无法防止术后固定后氧化肌纤维萎缩，但可能有助于从萎缩中恢复。
