Noehren Brian, Andersen Anders, Hardy Peter, Johnson Darren L, Ireland Mary Lloyd, Thompson Katherine L, Damon Bruce
Departments of Rehabilitation Sciences (B.N.), Anatomy and Neurobiology (A.A. and P.H.), Radiology (P.H.), Orthopaedic Surgery (A.A. and P.H.), Sports Medicine (D.L.J. and M.L.I.), and Statistics (K.L.T.), University of Kentucky, Lexington, Kentucky
Departments of Rehabilitation Sciences (B.N.), Anatomy and Neurobiology (A.A. and P.H.), Radiology (P.H.), Orthopaedic Surgery (A.A. and P.H.), Sports Medicine (D.L.J. and M.L.I.), and Statistics (K.L.T.), University of Kentucky, Lexington, Kentucky.
J Bone Joint Surg Am. 2016 Sep 21;98(18):1541-7. doi: 10.2106/JBJS.16.00035.
Individuals who have had an anterior cruciate ligament (ACL) tear and reconstruction continue to experience substantial knee extensor strength loss despite months of physical therapy. Identification of the alterations in muscle morphology and cellular composition are needed to understand potential mechanisms of muscle strength loss, initially as the result of the injury and subsequently from surgery and rehabilitation.
We performed diffusion tensor imaging-magnetic resonance imaging and analyzed muscle biopsies from the vastus lateralis of both the affected and unaffected limbs before surgery and again from the reconstructed limb following the completion of rehabilitation. Immunohistochemistry was done to determine fiber type and size, Pax-7-positive (satellite) cells, and extracellular matrix (via wheat germ agglutinin straining). Using the diffusion tensor imaging data, the fiber tract length, pennation angle, and muscle volume were determined, yielding the physiological cross-sectional area (PCSA). Paired t tests were used to compare the effects of the injury between injured and uninjured limbs and the effects of surgery and rehabilitation within the injured limb.
We found significant reductions before surgery in type-IIA muscle cross-sectional area (CSA; p = 0.03), extracellular matrix (p < 0.01), satellite cells per fiber (p < 0.01), pennation angle (p = 0.03), muscle volume (p = 0.02), and PCSA (p = 0.03) in the injured limb compared with the uninjured limb. Following surgery, these alterations in the injured limb persisted and the frequency of the IIA fiber type decreased significantly (p < 0.01) and that of the IIA/X hybrid fiber type increased significantly (p < 0.01).
Significant and prolonged differences in muscle quality and morphology occurred after ACL injury and persisted despite reconstruction and extensive physical therapy.
These results suggest the need to develop more effective early interventions following an ACL tear to prevent deleterious alterations within the quadriceps.
前交叉韧带（ACL）撕裂并重建的患者，即便经过数月的物理治疗，膝关节伸肌力量仍会大幅丧失。需要确定肌肉形态和细胞组成的变化，以了解肌肉力量丧失的潜在机制，最初是由于损伤，随后是手术和康复导致的。
我们进行了扩散张量成像 - 磁共振成像，并分析了手术前患侧和未患侧股外侧肌的肌肉活检样本，康复完成后再次分析重建肢体的样本。通过免疫组织化学确定纤维类型和大小、Pax - 7阳性（卫星）细胞以及细胞外基质（通过麦胚凝集素染色）。利用扩散张量成像数据，确定纤维束长度、羽状角和肌肉体积，得出生理横截面积（PCSA）。采用配对t检验比较受伤肢体与未受伤肢体之间损伤的影响，以及受伤肢体内部手术和康复的影响。
我们发现，与未受伤肢体相比，受伤肢体在手术前IIA型肌肉横截面积（CSA；p = 0.03）、细胞外基质（p < 0.01）、每根纤维的卫星细胞（p < 0.01）、羽状角（p = 0.03）、肌肉体积（p = 0.02）和PCSA（p = 0.03）均显著降低。手术后，受伤肢体的这些改变持续存在，IIA型纤维类型的频率显著降低（p < 0.01），IIA/X混合型纤维类型的频率显著增加（p < 0.01）。
ACL损伤后肌肉质量和形态出现显著且持久的差异，并持续存在，尽管进行了重建和广泛的物理治疗。
这些结果表明，ACL撕裂后需要制定更有效的早期干预措施，以防止股四头肌内出现有害改变。
