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The use of laser Doppler in determining timing for division of cross leg free flaps
The British Association of Plastic Surgeons (2005) 58, 120–125
Short reports and correspondence The use of laser Doppler in determining timing for division of cross leg free flaps The use of cross leg free flaps has been well documented as a procedure for the preservation of a limb following severe trauma. We report a cross leg free flap as a salvage procedure following a grade III B injury to the leg and the use of laser Doppler fluximetry as a method of monitoring the blood flow through the flap and to enable the correct timing for the division of the pedicle. A 19-year-old patient previously healthy girl, was admitted following a road traffic accident where she sustained a very severe grade IIIB injury to her right leg. Following intramedullary nailing a free latissimus dorsi flap was used to cover a defect measuring 18 £ 14 cm. This unfortunately failed and during the redo free latissimus dorsi transfer it was evident that there were both inflow and outflow problems in the limb. For flap salvage the contra lateral posterior tibial artery and saphenous vein were used to revascularise the muscle flap as a cross leg procedure. This proved successful and the legs were then externally fixed together for a minimum period of 3 weeks (Fig. 1). Given the very large size of the flap the problem then arose as how to monitor the blood flow in the flap in order to decide the correct time to divide the pedicle, and yet ensure neovascularisation of
Figure 1
Cross leg free flap and external fixation.
the muscle. Previous work on this has not indicated how to decide when the pedicle should be divided and the process involved in gradually ‘training’ the flap to survive without its pedicle.1 Most reports also describe either small flaps or cross leg free flaps with skin bridges across the two limbs to enable adequate monitoring of the vascularity.2,3 With this in mind we felt that the use of laser Doppler fluximetry may help us to decide the correct time of division. The laser Doppler provides a measure of red cell motion in the dermal capillaries with an effective measuring depth of 0.6 mm. No direct information on O2 exchange, nutrients and waste metabolites in the samples are given and the units of measurement are arbitrary, given as ‘perfusion units’ (PU). Sensitivity to movement artefacts and a non-linear relationship to flux at high volume fractions of red cells are disadvantages that require detailed attention when signal interpretation is made by the clinician. As no previous data were available as to the clamping regime the pedicle was initially clamped for 10 min three times a day and then increasing by 10 min per day until 60 min was achieved. It was clamped for 3 h three times a day for four days before division of the pedicle. The laser Doppler was used to measure the red cell flux pre, peri and for 20 min post clamping. This enabled us to monitor the dependability of the flap on the pedicle, and its response to ischaemia. As can be seen from graphs 1 and 2 the flap initially had a very low red cell flux and took time to recover after the clamp was released. The red cell flux improved, however, the longer the flap was clamped, and its post clamping recovery was quicker. This suggests that the flap is being ‘trained’ to accept its blood supply from its bed and to become less dependant on the pedicle. After achieving a total of 9 h clamping per day the pedicle was divided and the flap survived. This method has shown that cross leg free flaps are a good salvage procedure for lower leg trauma and that very large flaps can be successfully monitored, and with the correct method and a careful clamping regime, a flap will survive on its new vascular bed.
S0007-1226/$ - see front matter Q 2004 The British Association of Plastic Surgeons. Published by Elsevier Ltd. All rights reserved.
Short reports and correspondence
121
Graph 1
Red cell flux during clamping of free flap.
Graph 2 Red cell flux post clamping.
References 1. Topalan M, Ermis I. Cross leg free flap for emergency extremity salvage: a case report. J Reconstr Microsurg 2001;17(3):157—61. 2. Jones ME, Withey S, Grover R, Smith PJ. The use of photoplethysmograph to monitor the training of a cross leg free flap prior to division. Br J Plast Surg 2000;53(6):532—4. 3. Chen H, El-Gammel TA, Wei F, Noordhoff MS, Tang Y. Cross leg
free flaps for difficult cases of leg defects: indications, pitfalls and long term results. J Trauma 1997;43(3):486—91.
Mansoor S. Khan, Nick Kairinos, Michael Cadier Department of Plastic Surgery, Salisbury, UK doi:10.1016/j.bjps.2004.06.027
Short reports and correspondence The use of laser Doppler in determining timing for division of cross leg free flaps The use of cross leg free flaps has been well documented as a procedure for the preservation of a limb following severe trauma. We report a cross leg free flap as a salvage procedure following a grade III B injury to the leg and the use of laser Doppler fluximetry as a method of monitoring the blood flow through the flap and to enable the correct timing for the division of the pedicle. A 19-year-old patient previously healthy girl, was admitted following a road traffic accident where she sustained a very severe grade IIIB injury to her right leg. Following intramedullary nailing a free latissimus dorsi flap was used to cover a defect measuring 18 £ 14 cm. This unfortunately failed and during the redo free latissimus dorsi transfer it was evident that there were both inflow and outflow problems in the limb. For flap salvage the contra lateral posterior tibial artery and saphenous vein were used to revascularise the muscle flap as a cross leg procedure. This proved successful and the legs were then externally fixed together for a minimum period of 3 weeks (Fig. 1). Given the very large size of the flap the problem then arose as how to monitor the blood flow in the flap in order to decide the correct time to divide the pedicle, and yet ensure neovascularisation of
Figure 1
Cross leg free flap and external fixation.
the muscle. Previous work on this has not indicated how to decide when the pedicle should be divided and the process involved in gradually ‘training’ the flap to survive without its pedicle.1 Most reports also describe either small flaps or cross leg free flaps with skin bridges across the two limbs to enable adequate monitoring of the vascularity.2,3 With this in mind we felt that the use of laser Doppler fluximetry may help us to decide the correct time of division. The laser Doppler provides a measure of red cell motion in the dermal capillaries with an effective measuring depth of 0.6 mm. No direct information on O2 exchange, nutrients and waste metabolites in the samples are given and the units of measurement are arbitrary, given as ‘perfusion units’ (PU). Sensitivity to movement artefacts and a non-linear relationship to flux at high volume fractions of red cells are disadvantages that require detailed attention when signal interpretation is made by the clinician. As no previous data were available as to the clamping regime the pedicle was initially clamped for 10 min three times a day and then increasing by 10 min per day until 60 min was achieved. It was clamped for 3 h three times a day for four days before division of the pedicle. The laser Doppler was used to measure the red cell flux pre, peri and for 20 min post clamping. This enabled us to monitor the dependability of the flap on the pedicle, and its response to ischaemia. As can be seen from graphs 1 and 2 the flap initially had a very low red cell flux and took time to recover after the clamp was released. The red cell flux improved, however, the longer the flap was clamped, and its post clamping recovery was quicker. This suggests that the flap is being ‘trained’ to accept its blood supply from its bed and to become less dependant on the pedicle. After achieving a total of 9 h clamping per day the pedicle was divided and the flap survived. This method has shown that cross leg free flaps are a good salvage procedure for lower leg trauma and that very large flaps can be successfully monitored, and with the correct method and a careful clamping regime, a flap will survive on its new vascular bed.
S0007-1226/$ - see front matter Q 2004 The British Association of Plastic Surgeons. Published by Elsevier Ltd. All rights reserved.
Short reports and correspondence
121
Graph 1
Red cell flux during clamping of free flap.
Graph 2 Red cell flux post clamping.
References 1. Topalan M, Ermis I. Cross leg free flap for emergency extremity salvage: a case report. J Reconstr Microsurg 2001;17(3):157—61. 2. Jones ME, Withey S, Grover R, Smith PJ. The use of photoplethysmograph to monitor the training of a cross leg free flap prior to division. Br J Plast Surg 2000;53(6):532—4. 3. Chen H, El-Gammel TA, Wei F, Noordhoff MS, Tang Y. Cross leg
free flaps for difficult cases of leg defects: indications, pitfalls and long term results. J Trauma 1997;43(3):486—91.
Mansoor S. Khan, Nick Kairinos, Michael Cadier Department of Plastic Surgery, Salisbury, UK doi:10.1016/j.bjps.2004.06.027