ABSTRACT
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.