Maxwell L C, Enwemeka C S
Department of Physiology, University of Texas Health Science Center, San Antonio 78284-7756.
Anat Rec. 1992 Sep;234(1):55-61. doi: 10.1002/ar.1092340107.
In clinical practice, repaired tendocalcaneus (Achilles tendon) ruptures are often protected in immobilization casts for 4 weeks in the fully plantar flexed position and for up to another 4 weeks after returning the ankle to joint neutral. Moderate to severe muscle atrophy occurs within 4 weeks of immobilization in plantar flexion, but it is not known if this atrophy is minimized or reversed following restoration of joint neutral position. We tested the hypothesis that the extent of atrophy could be reduced by returning the ankle to joint neutral after 4 weeks of immobilization. Eighteen rabbits were anesthetized, and their right hind-limbs were casted with the knee flexed 90 degrees and the ankle fully plantar flexed. Three animals each were studied after 3, 4, 6, or 8 weeks of immobilization. After 4 weeks of immobilization, the immobilization casts of the remaining six rabbits were modified to return the ankle to joint neutral for another 2 or 4 weeks. For muscle studies, the animals were anesthetized, and the soleus (SOL), plantaris (PLN), and gastrocnemius (GST) muscles were removed and weighed; the SOL and PLN were quick frozen and processed for histochemical fiber typing and fiber cross-sectional area measurement. All three muscles showed significantly reduced muscle weight to body weight ratios after 3 weeks of immobilization. SOL was the most affected, and GST was least affected. There was no significant further atrophy through 8 weeks of immobilization. The atrophy correlated with a significant reduction of mean fiber area (MFA) for Types I, IIo, and IIc fibers in SOL and PLN. In PLN, Type IIg fiber area was not significantly reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
在临床实践中,修复后的跟腱(阿基里斯腱)断裂通常在完全跖屈位用固定石膏固定4周,在踝关节恢复到关节中立位后再固定长达4周。在跖屈位固定4周内会出现中度至重度肌肉萎缩,但尚不清楚在恢复关节中立位后这种萎缩是否会最小化或逆转。我们检验了这样一个假设,即固定4周后将踝关节恢复到关节中立位可以减少萎缩程度。18只兔子被麻醉,其右后肢在膝关节屈曲90度且踝关节完全跖屈的情况下用石膏固定。分别在固定3、4、6或8周后对3只动物进行研究。在固定4周后,将其余6只兔子的固定石膏进行修改,使踝关节恢复到关节中立位并再固定2周或4周。为进行肌肉研究,将动物麻醉,切除比目鱼肌(SOL)、跖肌(PLN)和腓肠肌(GST)并称重;将SOL和PLN快速冷冻并进行组织化学纤维分型和纤维横截面积测量。固定3周后,所有三块肌肉的肌肉重量与体重之比均显著降低。SOL受影响最大,GST受影响最小。在长达8周的固定过程中,没有出现明显的进一步萎缩。萎缩与SOL和PLN中I型、IIo型和IIc型纤维的平均纤维面积(MFA)显著减少相关。在PLN中,IIg型纤维面积没有显著减少。(摘要截短于250字)