A dynamic study of the circulation in the gracilis muscle in humans

The aim of the present study was an evaluation of the relative importance of the proximal and distal pedicles for the perfusion of the gracilis muscle flap, as well as to evaluate the importance of the functional connections between the proximal and distal vascular territories. Ten gracilis muscles were investigated in nine patients. They were all operated on in the supine position under general anesthesia. Microcirculatory blood flow (MBF) in the muscle was measured by a dual-channel laser Doppler flowmeter. Two angled probes were sutured opposite to the entry of the proximal and distal pedicles into the muscle, and were kept in place throughout the measurements. Data were acquired on line via a multichannel interface with acquisition/analysis software to a portable computer. The following measurements were done: during baseline with both pedicles intact; during occlusion of the proximal pedicle; after clamp release; during occlusion of the distal pedicle; after clamp release; after motor-nerve transection; and after disinsertion of the muscle from bone attachments. After clamping the proximal pedicle, MBF decreased proximally to 57 +/- 5 percent (p < 0.01), but remained unchanged distally. After occlusion of the distal pedicle, MBF remained virtually unchanged proximally (92 +/- 4 percent, NS), but decreased to 72 +/- 6 percent (p < 0.05) distally. There was a significantly greater decrease in MBF when the proximal pedicle was clamped, than after clamping the distal pedicle (p < 0.01). There was a strong linear correlation (r = 0.85) between the proximal and distal MBF after occlusion of the corresponding pedicle. Transection of the motor nerve resulted in a moderate increase in MBF values proximally (130 +/- 10 percent, p < 0.05), but not distally (108 +/- 18 percent, NS). Detachment of the muscle led to a distinct increase of MBF in both vascular territories (proximally 175 +/- 28, percent p < 0.05; distally 157 +/- 20 percent, p < 0.05). These measurements demonstrated the dominant role of the proximal pedicle in the gracilis muscle in humans. Furthermore, it was shown that each of the two pedicles (proximal and distal) has its own vascular territory, and that both territories are partially connected by intramuscular vascular anastomoses. The predictable extent of blood flow varies in individual cases and should be measured intraoperatively. In cases of marginal perfusion to the distal part of the muscle, a delay procedure should be considered.