Anatomical study of the medial gastrocnemius muscle flap: a quantitative assessment of the arc of rotation.

BACKGROUND: The authors compared the arc of rotation of medial gastrocnemius flaps according to three methods: standard harvesting, dissection of the "pes anserinus" muscle, and dissection of the medial condyle.

METHODS: This study was performed using 20 fresh cadavers in two anatomy laboratories in Lyon, France; and Dallas, Texas. The area covered by each flap was calculated. The arc of rotation was calculated using distance from a fixed point, the anterior tibial tuberosity, to the distal flap (segment 1), to the lateral knee (segment 2), to the upper knee (segment 3), and to the medial thigh (segment 4). All measurements were done with leg stretched, applying a tensile strength of 1 daN on the muscle.

RESULTS: The average surface of the flaps (32.5 ± 8.55 cm) did not vary with the technique used; neither did the length of segment 1 (19.6 ± 3.53 cm). Segment 2 (9.6 ± 3.1 cm) and segment 3 (13.6 ± 2.76 cm) were increased by 7.3 ± 11.1 percent and 21.3 ± 13.9 percent, respectively, when using pes anserinus dissection; and by 30.2 ± 23 percent and 49.3 ± 34 percent when combining with medial condyle dissection. Segment 4 (22.9 ± 2.21 cm) increased by 15.3 ± 12.8 percent with pes anserinus dissection alone and 36.2 ± 13 percent when combining with medial condyle dissection.

CONCLUSIONS: This study allowed precise measurement of the flaps and arcs of rotation according to the type of harvest. A marked length gain was achieved by pes anserinus dissection alone or the combination with medial condyle dissection. The authors' results support the importance of assessing the benefit/risk balance between different techniques according to the type and extent of soft-tissue loss requiring reconstruction.