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Quantitative Relationship Between Vascular Kinking and Twisting
Quantitative Relationship Between Vascular Kinking and Twisting Shyue-Yih Horng,1 Chen-Kun Chen,2 Chao-Hsiang Lee,2 and Shyue-Li Horng,3 Taiwan, Republic of China; Rochester, New York
A wide variety of factors causing vascular thrombosis in the microvascular free flap reconstruction have been encountered. The most frequent situation in our experiences has been vascular kinking because of improper positioning. It has been reported that the best way to avoid kinking is to place the vessels at a neutral axis. However, curving the pedicles to match the recipient vessels cannot be avoided, especially in head and neck reconstruction with a large flap and long pedicle. According to our clinical experiences, the curved vascular pedicle needs rotation in its axis from the neutral position to avoid kinking. Furthermore, we noted that the number of loops equals the number of axial rotations of 360 . We propose that these experiences and ideas can have wide applications in various fields of vascular surgery.
INTRODUCTION A wide variety of factors causing vascular thrombosis in the microvascular free flap reconstruction have been encountered. The most frequent situation in our experiences has been vascular kinking, especially in drainage veins with thin walls. Vascular redundancy after recanalization and flap inset position also increases the risk. It has been reported that the best way to determine the appropriate position for the pedicle is to place the vessels at a neutral axis. Demirseren et al. used island rat groin flaps to study the twisting pedicle effect on flap survival. They reported that twisting more than 360 might be associated with some edema and congestive change and even result in flap 1
Division of Plastic Surgery, Department of Surgery, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan, Republic of China. 2 Division of Plastic Surgery, Department of Surgery, Shuang-Ho Hospital, Taipei Medical University, Taipei, Taiwan, Republic of China. 3 Department of Chemical Engineering, Hajim School of Engineering & Applied Sciences, University of Rochester, Rochester, NY.
Correspondence to: Shyue-Yih Horng, MD, Division of Plastic Surgery, Department of Surgery, National Taiwan University Hospital, National Taiwan University, No. 7 Chung San South Road, Taipei, Taiwan, Republic of China, E-mail: [email protected] Ann Vasc Surg 2010; 24: 1154-1155 DOI: 10.1016/j.avsg.2010.07.023 Ó Annals of Vascular Surgery Inc.
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necrosis on twisting further.1 Other authors studied the microanastomotic patency in rat’s model and reported that rotational effects at the anastomotic site impaired the patency both in veins (when the rotation is more than 90 -270 in different studies) and arteries (when the rotation is more than 270 ).2-4 These studies deliver the clinical information that it is important to place the whole length of the pedicle in the neutral and straight position according to the recipient anastomosis. However, curving the pedicles to match the recipient vessels occasionally cannot be avoided, especially in head and neck reconstructions with a large flap and long pedicle. In these situations, kinking can easily be observed under flow pressure or positional change. Furthermore, congested veins with higher pressure will worsen the vicious cycle as well. After consequent 100s of free flap reconstruction and microvascular reanastomoses, we observed that vascular kinking can be prevented by studying the physics of vascular curving. The relationship between vascular torsion and curving cannot be detected very easily in the normal situation because of the minimal difference between the two. In contrast, it can be made more obvious by magnifying the length. By using house hose as an example, we can increase the hose length to several meters and the curving to several loops. The most comprehensible way to realize the relationship is
Vol. 24, No. 8, November 2010
Fig. 1. If a vessel is in a straight position as presented by the 3D color picture, the upper surface of the vessel is occupied by straight blue and white color line (the left). When it is curved by 90 , the axis needs to be rotated counter-clockwisely to correct the twisting effect. Therefore, in the neutral position, the twisted end of the vessel is occupied by white and green color line (the right). Other curved degrees (180 or 360 ) will follow the same pattern.
to store the house hose by curving and looping it. A smoothly looped hose can be obtained by rotating the axis gradually while looping it. We then noted that the number of loops equals the number of axial rotations of 360 . In contrast, when we are straightening an already stored hose, its quick rotation of axis can be seen vice versa. Therefore, we can assume that the number of loop equals number of 360 axial rotations (Fig. 1). On the basis of this assumption, the relationship between vascular curving and axial torsion can be understood clinically. Then, what will happen if we just curve the vessels without doing a little bit of axial rotation? Turbulent flow and kinking occurs especially in the thinnest part of the vessel wall or in the situation of excess pedicle length because the unrelieved bending and torsion effect can cause a gradual change of the inner lumen. Therefore, we learn from clinical practice that a little axial rotation needs to be made when the vessels are curved
Relationship vascular kinking and twisting 1155
especially in a sharp angle, instead of directly bending it. It thus fits our assumption that more curving needs more rotation. Another coming question is whether there is a clinical quantitative relationship. We observed that unlike house hose, the flexibility of biological vessels is different and may need a lesser degree of rotation compared with the rubber material. Under our clinical experiences, the quantitative adjustment of curving vessels by 180 may be between 90 and 180 of axial rotation. Other varieties that need to be considered include the mutually restricting effect of pedicle artery and vein and surrounding soft-tissue, the length of the pedicle and the flow pressure of the pedicle, and so forth. Therefore, more animal studies may be needed for the exact quantitative measurement. The same concept can be applied to the vein graft of A-V shunting for lower extremity microscopic reconstruction. Intending to bypass the trauma zone, the looping segment of A-V shunting graft is usually quite long. It therefore magnifies the twisting effect on vessels and makes the axial rotation adjustment essential. Cardiovascular surgeons also presented the same concept while performing arterial switch operations to minimize the risks of torsion or kinking.5 Therefore, we assume that this rule can be used not only for microvascular reconstruction but also for a wide variety of vascular fields, such as pedicles of liver, kidney and lung transplantation, peripheral vascular surgery, coronary and congenital heart surgery, and so forth.
REFERENCES 1. Demirseren ME, Yenidunya O, Yenidunya S. Island rat groin flap with twisted pedicles. Plast Reconstr Surg 2004;114: 1190-1194. 2. Topalan M, Bilgin S. Effect of torsion on microarterial anastomosis patency. Microsurgery 2003;23:56-59. 3. Salgarello M, Lahoud P, Selvaggi G, et al. The effect of twisting on microanastomotic patency of arteries and veins in a rat model. Ann Plast Surg 2001;47:643-646. 4. Iaguerdo R, Dobrin PB, Fu K, et al. The effect of twist on microvascular anastomotic patency and angiographic luminal dimensions. J Surg Res 1998;78:60-63. 5. Chiu IS, Chou TF, Lin SF, et al. Utilization of the aortic flap above the facing commissure in arterial switch operations. J Card Surg 1996;11:187-191.
A wide variety of factors causing vascular thrombosis in the microvascular free flap reconstruction have been encountered. The most frequent situation in our experiences has been vascular kinking because of improper positioning. It has been reported that the best way to avoid kinking is to place the vessels at a neutral axis. However, curving the pedicles to match the recipient vessels cannot be avoided, especially in head and neck reconstruction with a large flap and long pedicle. According to our clinical experiences, the curved vascular pedicle needs rotation in its axis from the neutral position to avoid kinking. Furthermore, we noted that the number of loops equals the number of axial rotations of 360 . We propose that these experiences and ideas can have wide applications in various fields of vascular surgery.
INTRODUCTION A wide variety of factors causing vascular thrombosis in the microvascular free flap reconstruction have been encountered. The most frequent situation in our experiences has been vascular kinking, especially in drainage veins with thin walls. Vascular redundancy after recanalization and flap inset position also increases the risk. It has been reported that the best way to determine the appropriate position for the pedicle is to place the vessels at a neutral axis. Demirseren et al. used island rat groin flaps to study the twisting pedicle effect on flap survival. They reported that twisting more than 360 might be associated with some edema and congestive change and even result in flap 1
Division of Plastic Surgery, Department of Surgery, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan, Republic of China. 2 Division of Plastic Surgery, Department of Surgery, Shuang-Ho Hospital, Taipei Medical University, Taipei, Taiwan, Republic of China. 3 Department of Chemical Engineering, Hajim School of Engineering & Applied Sciences, University of Rochester, Rochester, NY.
Correspondence to: Shyue-Yih Horng, MD, Division of Plastic Surgery, Department of Surgery, National Taiwan University Hospital, National Taiwan University, No. 7 Chung San South Road, Taipei, Taiwan, Republic of China, E-mail: [email protected] Ann Vasc Surg 2010; 24: 1154-1155 DOI: 10.1016/j.avsg.2010.07.023 Ó Annals of Vascular Surgery Inc.
1154
necrosis on twisting further.1 Other authors studied the microanastomotic patency in rat’s model and reported that rotational effects at the anastomotic site impaired the patency both in veins (when the rotation is more than 90 -270 in different studies) and arteries (when the rotation is more than 270 ).2-4 These studies deliver the clinical information that it is important to place the whole length of the pedicle in the neutral and straight position according to the recipient anastomosis. However, curving the pedicles to match the recipient vessels occasionally cannot be avoided, especially in head and neck reconstructions with a large flap and long pedicle. In these situations, kinking can easily be observed under flow pressure or positional change. Furthermore, congested veins with higher pressure will worsen the vicious cycle as well. After consequent 100s of free flap reconstruction and microvascular reanastomoses, we observed that vascular kinking can be prevented by studying the physics of vascular curving. The relationship between vascular torsion and curving cannot be detected very easily in the normal situation because of the minimal difference between the two. In contrast, it can be made more obvious by magnifying the length. By using house hose as an example, we can increase the hose length to several meters and the curving to several loops. The most comprehensible way to realize the relationship is
Vol. 24, No. 8, November 2010
Fig. 1. If a vessel is in a straight position as presented by the 3D color picture, the upper surface of the vessel is occupied by straight blue and white color line (the left). When it is curved by 90 , the axis needs to be rotated counter-clockwisely to correct the twisting effect. Therefore, in the neutral position, the twisted end of the vessel is occupied by white and green color line (the right). Other curved degrees (180 or 360 ) will follow the same pattern.
to store the house hose by curving and looping it. A smoothly looped hose can be obtained by rotating the axis gradually while looping it. We then noted that the number of loops equals the number of axial rotations of 360 . In contrast, when we are straightening an already stored hose, its quick rotation of axis can be seen vice versa. Therefore, we can assume that the number of loop equals number of 360 axial rotations (Fig. 1). On the basis of this assumption, the relationship between vascular curving and axial torsion can be understood clinically. Then, what will happen if we just curve the vessels without doing a little bit of axial rotation? Turbulent flow and kinking occurs especially in the thinnest part of the vessel wall or in the situation of excess pedicle length because the unrelieved bending and torsion effect can cause a gradual change of the inner lumen. Therefore, we learn from clinical practice that a little axial rotation needs to be made when the vessels are curved
Relationship vascular kinking and twisting 1155
especially in a sharp angle, instead of directly bending it. It thus fits our assumption that more curving needs more rotation. Another coming question is whether there is a clinical quantitative relationship. We observed that unlike house hose, the flexibility of biological vessels is different and may need a lesser degree of rotation compared with the rubber material. Under our clinical experiences, the quantitative adjustment of curving vessels by 180 may be between 90 and 180 of axial rotation. Other varieties that need to be considered include the mutually restricting effect of pedicle artery and vein and surrounding soft-tissue, the length of the pedicle and the flow pressure of the pedicle, and so forth. Therefore, more animal studies may be needed for the exact quantitative measurement. The same concept can be applied to the vein graft of A-V shunting for lower extremity microscopic reconstruction. Intending to bypass the trauma zone, the looping segment of A-V shunting graft is usually quite long. It therefore magnifies the twisting effect on vessels and makes the axial rotation adjustment essential. Cardiovascular surgeons also presented the same concept while performing arterial switch operations to minimize the risks of torsion or kinking.5 Therefore, we assume that this rule can be used not only for microvascular reconstruction but also for a wide variety of vascular fields, such as pedicles of liver, kidney and lung transplantation, peripheral vascular surgery, coronary and congenital heart surgery, and so forth.
REFERENCES 1. Demirseren ME, Yenidunya O, Yenidunya S. Island rat groin flap with twisted pedicles. Plast Reconstr Surg 2004;114: 1190-1194. 2. Topalan M, Bilgin S. Effect of torsion on microarterial anastomosis patency. Microsurgery 2003;23:56-59. 3. Salgarello M, Lahoud P, Selvaggi G, et al. The effect of twisting on microanastomotic patency of arteries and veins in a rat model. Ann Plast Surg 2001;47:643-646. 4. Iaguerdo R, Dobrin PB, Fu K, et al. The effect of twist on microvascular anastomotic patency and angiographic luminal dimensions. J Surg Res 1998;78:60-63. 5. Chiu IS, Chou TF, Lin SF, et al. Utilization of the aortic flap above the facing commissure in arterial switch operations. J Card Surg 1996;11:187-191.