Objective To discuss the ultrasonic anatomy of gastrocnemius and its substructures in normal population. Methods Eighty gastrocnemius in 40 volunteers were scanned by real time high frequency ultrasound. Sonograms of medial and lateral heads of gastrocnemius were acquired. Plume angles between medial and lateral heads of gastrocnemius were measured at condition of rest, 5 kg and 10 kg isometric contraction. Both dominant and non-dominant legs were evaluated. Differences of plume angles were compared by ANOVA in different conditions and by t test in different legs. Results At the upper part of the muscle, both medial and lateral heads of gastrocnemius could be divided into muscular compartment, shallow compartment and deep compartment by hyperechoic intra-muscular septa with clear margin. The septa of lateral heads presented as hyperechoic side-lying′T′, while the septa of medial heads presented as hyperechoic side-lying-′T′. Vascular signals could be detected in these hyperechoic septa. The plume angle at the distal part of the lateral head of gastrocnemius was composed of shallow compartment attaching to the Achilles tendon, and that of the medial head was composed of medial muscular compartment attaching to the tendon. At rest, 5 kg and 10 kg isometric contraction, plume angles of lateral heads were (13.36±3.20)°, (13.32±3.30)° and (12.75±3.20)°, and plume angles of medial heads were (8.69±3.30)°, (8.59±2.99)° and (8.65±3.20)°. Under the same condition, plume angles of medial heads were larger than those of lateral heads and the difference was statistically signiifcant (t=9.09, 9.50 and 8.10, all P<0.01). Changes of plume angles between rest and different weight bearing conditions were small, and differences were not statistically signiifcant (F=0.89 and 0.02, P=0.41 and 0.98). Plume angles of medial heads in dominant legs and non-dominant legs were (13.66±3.60)° and (13.30±2.84)°, and those of lateral heads were (8.71±3.48)° and (8.80±3.35)°. The plume angles of medial heads were larger in dominant legs than those in non-dominant legs, while the plume angles of lateral heads were smaller in dominant legs than those in non-dominant legs. However, both differences were not statistically signiifcant (t=0.70 and 0.87, P=0.48 and 0.17). Conclusions The anatomical characteristics of medial and lateral heads and compartments of gastrocnemius can be clearly depicted by high frequency ultrasound. Plume angles can also be accurately measured.%目的：探讨正常人群腓肠肌及其亚部构筑的超声解剖学特点。方法应用高频超声对40名健康志愿者共80条腓肠肌肌腹及其远端肌肉腱膜处进行在体实时扫查，获得腓肠肌内、外侧头及其亚部超声图像；并在静息（分惯用脚和非惯用脚）及用力5 kg、10 kg等长收缩状态下获取腓肠肌内侧头和外侧头羽状角超声测值。采用单因素方差分析比较不同状态下腓肠肌羽状角测值的差异，采用成组t检验比较惯用脚与非惯用脚腓肠肌羽状角测值的差异。结果腓肠肌上部横断面扫查时，内、外侧头肌肉依据肌肉内强回声分隔，均可分为肌质亚部、浅亚部和深亚部3个部分，各部分边界清晰。外侧头3个亚部分隔呈侧卧姿的“T”形条状强回声，内侧头分隔则呈卧姿的“Y”形条状强回声，在“T”和“Y”字形强回声分隔上均可探及血流信号。腓肠肌外侧头远端羽状角为外侧浅亚部连接于跟腱构成，内侧头远端羽状角则为内侧肌质亚部续于跟腱构成。静息及用力5 kg、10 kg状态下，腓肠肌内侧头羽状角测值分别为（13.36±3.20）°、（13.32°±3.30）°、（12.75±3.20）°，外侧头羽状角测值分别为（8.69±3.30）°、（8.59±2.99）°、（8.65±3.20）°，同一状态下内侧头羽状角测值均大于外侧头羽状角测值，且差异有统计学意义（t值分别为9.09、9.50和8.10，P均＜0.01）。腓肠肌内、外侧头在静息及承受不同外力的状态下，羽状角变化均无统计学意义（F=0.89、0.02，P=0.41、0.98）。惯用脚与非惯用脚腓肠肌内侧头羽状角测值分别为（13.66±3.60）°、（13.30±2.84）°，腓肠肌外侧头羽状角测值分别为（8.71±3.48）°、（8.80±3.35）°。惯用脚肠肌内侧头羽状角测值大于非惯用脚，而腓肠肌外侧头羽状角测值小于非惯用脚，但差异均无统计学意义（t=0.70、0.87，P=0.48、0.17）。结论在体高频超声可清晰显示腓肠肌内、外侧头及其亚部构筑的超声解剖特点，并可获取羽状角的准确测值。
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