Use of ultrasonography to evaluate muscle thickness and blood flow in free flaps

Abstract

The purpose of this study was to investigate the common belief that a microvascular transfer of a non-innervated free muscle flap loses muscle bulk over time. Sixteen patients (latissimus dorsi = 8, rectus abdominis = 7, and gracilis muscle = 1) were evaluated an average of 41 months after free flap transfer. Latissimus dorsi and lower extremity flaps displayed significantly more swelling than the other flaps. Flap bulk was measured by ultrasound. The mean thickness of upper extremity flaps was 10.3 +/- 1.8 mm (control muscles 11.8 +/- 2.8), lower-extremity 14.5 +/- 3.7 mm (control muscles 10.9 +/- 0.7), latissimus dorsi 14.3 +/- 2.2 mm (control muscles 10.3 +/- 0.8, P = 0.018), and rectus abdominis 11.2 +/- 1.2 mm (control muscles 12.4 +/- 1.9). Color Doppler ultrasonography was used to detect the pedicles of the free flaps and also to measure the peak velocity of blood flow intramuscularly and in the pedicles. In the upper extremities (n = 5) the pedicles could be found in only 20% of cases whereas in the lower extremities (n = 11) 91% of pedicles were located. (P = 0.013). Peak flow within the free flaps was significantly higher in the lower extremity (50% of the peak flow of the common femoral artery) than in the upper extremity (5% of the peak flow of the common femoral artery, P = 0.013). This study demonstrated that non-innervated free muscle flaps in the extremities maintain the original muscle thickness, although lower extremity and latissimus dorsi flaps have a trend to be thicker. Most pedicles of free muscle flaps in the upper extremities could not be located by ultrasound. However, flaps in the lower extremities most often have patent pedicles and also more vigorous intramuscular blood flow.

Blood flow in free micro-vascular flaps

“…They also showed that, in the lower extremity, free muscle flaps maintain their vascular pe-dicle and seem to have more muscle bulk, probably because of vigorous blood flow through their pedicles and in the muscle tissue itself (132). On the other hand most pedicles could not be found by ultrasound examination in free muscle flaps transplanted to the upper extremity (132). Machens et al found persistence of pedicle blood flow for up to 10 years after uncomplicated free LD transfer (93) whereas loss of autonomous blood supply through the vascular pedicle, with thrombosis of the venous anastomosis, seems to occur in free tissue transfers even after successful surgical revision (92).…”

“…Using magnetic resonance imaging (MRI), computer assisted tomography (CT) and colour Doppler ultrasound, Salmi et al showed in clinical studies that the extensive postoperative swelling of a free muscle flap subsides over time and that the flap regains its original thickness in 6-9 months (133,134) although lower extremity and LD muscle flaps tend to be thicker (132). They also showed that, in the lower extremity, free muscle flaps maintain their vascular pe-dicle and seem to have more muscle bulk, probably because of vigorous blood flow through their pedicles and in the muscle tissue itself (132).…”

“…They also showed that, in the lower extremity, free muscle flaps maintain their vascular pe-dicle and seem to have more muscle bulk, probably because of vigorous blood flow through their pedicles and in the muscle tissue itself (132). On the other hand most pedicles could not be found by ultrasound examination in free muscle flaps transplanted to the upper extremity (132).…”

“…In a clinical haemodynamic study of free muscle flaps transplanted to the lower extremity, with colour Doppler ultrasound used both before and after the operation, it was found that blood flow increased in the flaps at 2 weeks to 3 months after the operation because of reduced vascular resistance of the muscle (132). Sasmor et al have previously documented that flap vascular resistance regulates the blood supply to the flap (138).…”

“…In free flap surgery Doppler ultrasound has been used to monitor blood flow in a LD free muscle flap (46), to detect vessels (132) and to measure blood flow velocities after free flap surgery (135), indicating that blood flow increases in clinical free muscle flaps from 2 weeks to 3 months postoperatively mainly because of an increase in minimum velocity and a decrease in vascular resistance due to denervation.…”