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The deep venous system and reverse flow flaps
Letters to the Editor
The deep venous system and reverse flow flaps. Sir, In the 1980s plastic surgeons developed island flaps on limbs, with reverse flow through the venae comitantes in the flap pedicles. There is a greater frequency of valves in these deep veins than in superficial veins.’ Two hypotheses were proposed to explain how reverse flow in the deep veins was possible. One was that the valves were by-passed.2 However at some point in radial forearm flap pedicles there are valves with no apparent by-pass. 1.3 The second hypothesis proposed that a combination of three factors (blood in the vein proximal and distal to a valve, venous blood pressure higher proximal to the valve than distal to it, and denervation) would allow reverse flow through a valve. even though each factor alone was insufficient.4 With this second hypothesis, it was also stated by-passes around valves in other parts of the flap pedicles could not be ruled out.’ My original hypothesis of reverse flow was very primitive, more Stone Age than New Age. It assumed the veins were kept filled by blood from the wrist and hand.l My old (but still young!) colleague Julian Wee refined the hypothesis by
suggesting the veins were kept filled on each side of the valves by fine venules in the adventitia around the flap pedicles.5 He noted that such fine vessels had been shown by Emerson et al.,6 and he emphasised that the adventitia should be preserved, the flap pedicle should not be skeletonised. All this hypothesising desperately needed to be tested by direct observations and I am delighted that, following on from studies such as those of Torii et al.,? de1 Pinal and Taylor have reported their detailed, beautifully illustrated work.8 Denervation alone as a cause of reverse tlow through valves was ruled out early on by several of us, because of the well known action of valves in vein grafts, as illustrated4 and stated’ elsewhere. Del Pinal and Taylor reinforce my own criticisms. Similarly, they note high venous pressure alone will not explain the rapid reversal of flow as a flap is raised. They confirm there is a fine plexus of adventitial vessels, noting veno-venous connections as opposed to the arteriovenous connections suggested by Wee,5 and found no valves in the fine veins, unlike Emerson et aL3 They observed numerous valves in the deep veins with, for example, intervalvular distances of 0.91 and 1.43 cm in radial artery venae comitantes, in keeping with the l-3 cm and 3 cm, average, reported before.‘, ’ Their neat experiments on distally based canine island
Aggregatrng
SIreIch Hvwxta
platelets
I Vascular
smwth
Endothelium-derived vasoactive factors. Endothelium-derived relaxing factor (EDRF), prostacyclin (PGlr) and endothelium-derived hyperpolariring factor (EDHF) are smooth muscle relaxants. Endothelin-I, thromboxane As (TKAs) and other endothelium-derived contracting factors (EDCFs) are constrictors. Neurohumoral mediators may induce release of the above factors, as well as having direct vascular actions (usually constrictor). Note that prostacyclin and EDRF can be released by common stimuli. AA=arachidonic acid; 5-HT= 5hydroxytryptamine (SerOt0t-k); PI=membrane phosphatidylinositof; NO=nitric oxide; ACh=acetylcholine; BK=bradykinin; All=angiotensin II cGMP=cyclic guanosine monophosphate; cAMP=cyclic adenosine monophosphate. Fig. 1
Figure-Reproduced
by the kind permission
of the British Journnl qf Hospital
3-90
Mdicine
from Shah AM.‘”
Letters
391
to the Editor
saphenous flaps show these flaps have a delicate circulation, which is inadequate in most cases where the main pedicle vessels are skeletonised. Similar flaps in rabbits are equally delicate: if their distally based vein is divided (thereby also dividing the fine vessels around it) and then anastomosed to a local vein. most of the flaps necrose.g The plexus of fine veins is clearly important to ensure adequate venous drainage. The retrograde phlebography showed the main venae comitantes of the experimental flap pedicles were patent and had incompetent valves. It is fascinating that the valves of the venae comitantes distal to the pedicle pivot points were also incompetent. How? These veins had a high (56 cm of water) venous pressure, they had blood entering from the foot, and although the adjacent tibia1 nerve was intact, the vasomotor sympathetic nerves to the distal veins had been divided proximally when the flap was elevated. Dare I suggest that the combination of the three factors of the second hypothesis was in place?! Wee proposed the veins should be dissected distal to the pedicle pivot point to denervate them; the canine experiments show this is probably not necessary. In 1955, Rodbard reported that increasing outlet resistance can maintain or “paradoxically” increase fluid flow through collapsible rubber tubes for a given input pressure.l.l” Del Pinal and Taylor’s experiments on isolated valved veins nicely add to this work. The high blood flow, the raised venous pressure, the canine phlebograms and the clinical appearance of the veins in the pedicles of reverse radial forearm flaps all suggest the main venous return is down the venae comitantes in reverse flow flaps: the macrovenous cross connections and the fine venous plexus make this possible in most cases. Overall, de1 Pinal and Taylor’s findings support the framework of Wee’s refined hypothesis and the conclusions of Torii et al. Their results also explain the unreliability of experimental and clinical reverse flow free flaps, although in some modified cases these have been successful.” A key factor is the smooth muscle, known to be in the walls and valve bases of veins,l” including deep veins.’ Sympathetic nerves, circulating hormones and local factors influence the smooth muscle tone.13 Del Pinal and Taylor are right; denervation is not the only cause of vein di!atation. Cold blood in deep venae comitantes makes them dilate (in contrast to the superficial veins which constrict),13 phlebotomists daily confirm that superficial veins dilate (temporarily) in response to simple tapping,14 and others have shown that insertion of a needle alongside a vein, or local infiltration of lignocaine or saline can result in reversed venous flow.15 Nevertheless, smooth muscle dilatation by denervation still seems relevant to the original question of reverse flow in the pedicles of distally based radial forearm flaps. In the 1990s we should now consider the vascular endothelium.‘“, Ii This has many regulatory functions, including the release of vasodilators such as endotheliumderived relaxing factor (EDRF) and vasoconstrictors such as endothelin-1 (see Figure); these may be the final pathway for some of the vascular changes in reverse flow flaps. Skin flap ischaemia raises plasma endothelin-1 levels.18 There is now an orally active endothelin receptor antagonist.lg Understanding and controlling the vascular endothelium could open one of the doors to the next stage of vascular engineering for reconstructive surgery. Yours faithfully.
M. J. Timmons, MA, MChir, FRCS, Consultant Plastic Surgeon, St. Luke’s Hospital. Bradford BD5 ONA
References 1. rimmons
MJ. The vascular basis of the radial forearm Plast Reconstr Surg 1986; 77: 80-92.
flap.
L. Chiu C-C. Venous drainage in the 2. Lin S-D. Chung-Sheng reverse forearm flau. Plast Reconstr Surg 1984: 74: 508-12. on the 3. Emerson DJM. Sprigg A. Page RE. Some observations radial artery island flap. Br J Plast Surg 1985; 38 : 107-12. 4. Timmons MJ. William Harvey revisited: reverse flow through the valves of forearm veins. Lancet 1984: ii: 3945. of the lower leg and foot with the 5. Wee JTK. Reconstruction reverse-pedicled anterior tibia1 flap: preliminary report of a new fasciocutaneous Ran. Br J Plast Sure 1986; 39: 327-37. 6. Wee JTK. Venous flow in’the distally pedt%ed radial forearm flap: anatomical, physiological and surgical considerations. In: Gilbert A, Masquelet AC, Hentz VR. eds. Pedicle flaps of the upper limb. London: Martin Dunitz, 1992: 101-9. 7. Torii S. Namiki Y. Mori R. Reverse-flow island flaps: clinical report and venous drainage. Plast Reconstr Surg 1987: 79: 600-9. 8. Del Pinal F. Taylor GI. The deep venous system and reverse flow flaps. Br J Plast Surg 1993; 46: 652.--64. 9. Stewart DH. Puckett CL. Is reversed venous flow safe in free flap transfer? A dilemma with the radial forearm flap. Plast Reconstr Surg 1992; 89: 23742. S. Flow through collapsible tubes: augmented flow 10. Rodbard produced by resistance at the outlet. Circulation 1955: 11: 280-7. D. Free forearm flap for reII. Partecke B-D, Buck-Gramcko construction of soft tissue defects concurrent with improved peripheral circulation. J Reconstr Microsurg 1984: I : l-6. 12. Kampmeier OF, La Fleur Birch C. The origin and development of the venous valves, with particular reference to the saphenous district. Am J Anat 1927; 38: 45 I-99. 13. Vanhoutte PM, Janssens WJ. Local control of venous function. Microvasc Res 1978: 16: 196-214. 14. Franklin KJ. McLachlin AD. Dilatation ofveinsin response to tapping in man and other mammals. J Physiol (Land) 1936; 88 : 257-60. DA. The superficial venous system: 15. Sassoon E. McGrouther when is a valve not a valve? Winter Meeting of the British Association of Plastic Surgeons. London; December, 1992. Br J Hosp Med 1992; 48: 16. Shah AM. Vascular endothelium. 540-9. a new 17. Davies MC, Hagen P-O. The vascular endothelium: horizon. Ann Surg 1993; 218: 593-609. K. EfTect of skin flap ischemia on plasma endo18. Matsuzaki thelin-1 levels. Ann Plast Surg 1993 ; 3 I : 499-503. 19. Webb DJ, Haynes WC. Endothelins come of age. Lancet 1993; 342: 1439-40. Letter received
15 February
1994
Flaps based on posterior tibia1 vessels Sir, We have read with great interest the paper “The anatomic basis and clinical applications of flaps based on the posterior tibia1 vessels” by W. C. Wu et al.’ This publication has the merit of reviewing the use of flaps based on the posterior tibia1 vessels. Since 1986, we have studied this vascular axis and published the distally based fasciocutaneous flap.” This first report of a fasciocutaneous flap based on the distal direct fasciocutaneous branches has not been mentioned in the article by Wu et al. and we hope it may be kept in mind for future publications about this interesting subject. Recently, as we have presented in a communication, we have used this fasciocutaneous flap in 38 clinical cases,” in seven of them to reconstruct the heel, in three to reconstruct the lateral malleolus and in two to reconstruct the medial malleolus.
The deep venous system and reverse flow flaps. Sir, In the 1980s plastic surgeons developed island flaps on limbs, with reverse flow through the venae comitantes in the flap pedicles. There is a greater frequency of valves in these deep veins than in superficial veins.’ Two hypotheses were proposed to explain how reverse flow in the deep veins was possible. One was that the valves were by-passed.2 However at some point in radial forearm flap pedicles there are valves with no apparent by-pass. 1.3 The second hypothesis proposed that a combination of three factors (blood in the vein proximal and distal to a valve, venous blood pressure higher proximal to the valve than distal to it, and denervation) would allow reverse flow through a valve. even though each factor alone was insufficient.4 With this second hypothesis, it was also stated by-passes around valves in other parts of the flap pedicles could not be ruled out.’ My original hypothesis of reverse flow was very primitive, more Stone Age than New Age. It assumed the veins were kept filled by blood from the wrist and hand.l My old (but still young!) colleague Julian Wee refined the hypothesis by
suggesting the veins were kept filled on each side of the valves by fine venules in the adventitia around the flap pedicles.5 He noted that such fine vessels had been shown by Emerson et al.,6 and he emphasised that the adventitia should be preserved, the flap pedicle should not be skeletonised. All this hypothesising desperately needed to be tested by direct observations and I am delighted that, following on from studies such as those of Torii et al.,? de1 Pinal and Taylor have reported their detailed, beautifully illustrated work.8 Denervation alone as a cause of reverse tlow through valves was ruled out early on by several of us, because of the well known action of valves in vein grafts, as illustrated4 and stated’ elsewhere. Del Pinal and Taylor reinforce my own criticisms. Similarly, they note high venous pressure alone will not explain the rapid reversal of flow as a flap is raised. They confirm there is a fine plexus of adventitial vessels, noting veno-venous connections as opposed to the arteriovenous connections suggested by Wee,5 and found no valves in the fine veins, unlike Emerson et aL3 They observed numerous valves in the deep veins with, for example, intervalvular distances of 0.91 and 1.43 cm in radial artery venae comitantes, in keeping with the l-3 cm and 3 cm, average, reported before.‘, ’ Their neat experiments on distally based canine island
Aggregatrng
SIreIch Hvwxta
platelets
I Vascular
smwth
Endothelium-derived vasoactive factors. Endothelium-derived relaxing factor (EDRF), prostacyclin (PGlr) and endothelium-derived hyperpolariring factor (EDHF) are smooth muscle relaxants. Endothelin-I, thromboxane As (TKAs) and other endothelium-derived contracting factors (EDCFs) are constrictors. Neurohumoral mediators may induce release of the above factors, as well as having direct vascular actions (usually constrictor). Note that prostacyclin and EDRF can be released by common stimuli. AA=arachidonic acid; 5-HT= 5hydroxytryptamine (SerOt0t-k); PI=membrane phosphatidylinositof; NO=nitric oxide; ACh=acetylcholine; BK=bradykinin; All=angiotensin II cGMP=cyclic guanosine monophosphate; cAMP=cyclic adenosine monophosphate. Fig. 1
Figure-Reproduced
by the kind permission
of the British Journnl qf Hospital
3-90
Mdicine
from Shah AM.‘”
Letters
391
to the Editor
saphenous flaps show these flaps have a delicate circulation, which is inadequate in most cases where the main pedicle vessels are skeletonised. Similar flaps in rabbits are equally delicate: if their distally based vein is divided (thereby also dividing the fine vessels around it) and then anastomosed to a local vein. most of the flaps necrose.g The plexus of fine veins is clearly important to ensure adequate venous drainage. The retrograde phlebography showed the main venae comitantes of the experimental flap pedicles were patent and had incompetent valves. It is fascinating that the valves of the venae comitantes distal to the pedicle pivot points were also incompetent. How? These veins had a high (56 cm of water) venous pressure, they had blood entering from the foot, and although the adjacent tibia1 nerve was intact, the vasomotor sympathetic nerves to the distal veins had been divided proximally when the flap was elevated. Dare I suggest that the combination of the three factors of the second hypothesis was in place?! Wee proposed the veins should be dissected distal to the pedicle pivot point to denervate them; the canine experiments show this is probably not necessary. In 1955, Rodbard reported that increasing outlet resistance can maintain or “paradoxically” increase fluid flow through collapsible rubber tubes for a given input pressure.l.l” Del Pinal and Taylor’s experiments on isolated valved veins nicely add to this work. The high blood flow, the raised venous pressure, the canine phlebograms and the clinical appearance of the veins in the pedicles of reverse radial forearm flaps all suggest the main venous return is down the venae comitantes in reverse flow flaps: the macrovenous cross connections and the fine venous plexus make this possible in most cases. Overall, de1 Pinal and Taylor’s findings support the framework of Wee’s refined hypothesis and the conclusions of Torii et al. Their results also explain the unreliability of experimental and clinical reverse flow free flaps, although in some modified cases these have been successful.” A key factor is the smooth muscle, known to be in the walls and valve bases of veins,l” including deep veins.’ Sympathetic nerves, circulating hormones and local factors influence the smooth muscle tone.13 Del Pinal and Taylor are right; denervation is not the only cause of vein di!atation. Cold blood in deep venae comitantes makes them dilate (in contrast to the superficial veins which constrict),13 phlebotomists daily confirm that superficial veins dilate (temporarily) in response to simple tapping,14 and others have shown that insertion of a needle alongside a vein, or local infiltration of lignocaine or saline can result in reversed venous flow.15 Nevertheless, smooth muscle dilatation by denervation still seems relevant to the original question of reverse flow in the pedicles of distally based radial forearm flaps. In the 1990s we should now consider the vascular endothelium.‘“, Ii This has many regulatory functions, including the release of vasodilators such as endotheliumderived relaxing factor (EDRF) and vasoconstrictors such as endothelin-1 (see Figure); these may be the final pathway for some of the vascular changes in reverse flow flaps. Skin flap ischaemia raises plasma endothelin-1 levels.18 There is now an orally active endothelin receptor antagonist.lg Understanding and controlling the vascular endothelium could open one of the doors to the next stage of vascular engineering for reconstructive surgery. Yours faithfully.
M. J. Timmons, MA, MChir, FRCS, Consultant Plastic Surgeon, St. Luke’s Hospital. Bradford BD5 ONA
References 1. rimmons
MJ. The vascular basis of the radial forearm Plast Reconstr Surg 1986; 77: 80-92.
flap.
L. Chiu C-C. Venous drainage in the 2. Lin S-D. Chung-Sheng reverse forearm flau. Plast Reconstr Surg 1984: 74: 508-12. on the 3. Emerson DJM. Sprigg A. Page RE. Some observations radial artery island flap. Br J Plast Surg 1985; 38 : 107-12. 4. Timmons MJ. William Harvey revisited: reverse flow through the valves of forearm veins. Lancet 1984: ii: 3945. of the lower leg and foot with the 5. Wee JTK. Reconstruction reverse-pedicled anterior tibia1 flap: preliminary report of a new fasciocutaneous Ran. Br J Plast Sure 1986; 39: 327-37. 6. Wee JTK. Venous flow in’the distally pedt%ed radial forearm flap: anatomical, physiological and surgical considerations. In: Gilbert A, Masquelet AC, Hentz VR. eds. Pedicle flaps of the upper limb. London: Martin Dunitz, 1992: 101-9. 7. Torii S. Namiki Y. Mori R. Reverse-flow island flaps: clinical report and venous drainage. Plast Reconstr Surg 1987: 79: 600-9. 8. Del Pinal F. Taylor GI. The deep venous system and reverse flow flaps. Br J Plast Surg 1993; 46: 652.--64. 9. Stewart DH. Puckett CL. Is reversed venous flow safe in free flap transfer? A dilemma with the radial forearm flap. Plast Reconstr Surg 1992; 89: 23742. S. Flow through collapsible tubes: augmented flow 10. Rodbard produced by resistance at the outlet. Circulation 1955: 11: 280-7. D. Free forearm flap for reII. Partecke B-D, Buck-Gramcko construction of soft tissue defects concurrent with improved peripheral circulation. J Reconstr Microsurg 1984: I : l-6. 12. Kampmeier OF, La Fleur Birch C. The origin and development of the venous valves, with particular reference to the saphenous district. Am J Anat 1927; 38: 45 I-99. 13. Vanhoutte PM, Janssens WJ. Local control of venous function. Microvasc Res 1978: 16: 196-214. 14. Franklin KJ. McLachlin AD. Dilatation ofveinsin response to tapping in man and other mammals. J Physiol (Land) 1936; 88 : 257-60. DA. The superficial venous system: 15. Sassoon E. McGrouther when is a valve not a valve? Winter Meeting of the British Association of Plastic Surgeons. London; December, 1992. Br J Hosp Med 1992; 48: 16. Shah AM. Vascular endothelium. 540-9. a new 17. Davies MC, Hagen P-O. The vascular endothelium: horizon. Ann Surg 1993; 218: 593-609. K. EfTect of skin flap ischemia on plasma endo18. Matsuzaki thelin-1 levels. Ann Plast Surg 1993 ; 3 I : 499-503. 19. Webb DJ, Haynes WC. Endothelins come of age. Lancet 1993; 342: 1439-40. Letter received
15 February
1994
Flaps based on posterior tibia1 vessels Sir, We have read with great interest the paper “The anatomic basis and clinical applications of flaps based on the posterior tibia1 vessels” by W. C. Wu et al.’ This publication has the merit of reviewing the use of flaps based on the posterior tibia1 vessels. Since 1986, we have studied this vascular axis and published the distally based fasciocutaneous flap.” This first report of a fasciocutaneous flap based on the distal direct fasciocutaneous branches has not been mentioned in the article by Wu et al. and we hope it may be kept in mind for future publications about this interesting subject. Recently, as we have presented in a communication, we have used this fasciocutaneous flap in 38 clinical cases,” in seven of them to reconstruct the heel, in three to reconstruct the lateral malleolus and in two to reconstruct the medial malleolus.