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Behavior of arterial grafts at the hip and knee joints
VSONIC
IMAGING
4,
83-91
(1982)
BEHAVIOR OF ARTERIAL P. C. Clifford,1
GRAFTS AT THE HIP AND KNEE JOINTS
R. Skidmore,
Departments
J.
P. Woodcock,
of Surgery and Medical Bristol Royal Infirmary Bristol, U.K.
and R. N. Baird Physics
Real time ultrasonic scanning with a Duplex scanner (A.T.L.) was used to study Dacron arterial grafts crossing the hip and knee joints in 27 patients (25 males, 2 females), mean age 61 years. Ultrasonic imaging of the grafts was rapid and demonstrated kinking during knee flexion in 83 percent of grafts anastomosed to the distal popliteal artery. Only 7 percent of grafts crossing the inguinal ligament kinked during 60" of hip flexion. Graft associated
kinking during knee flexion may be a factor in acute thrombosis with long periods of immobility, such as during air travel.
Key words:
Arterial graft kinking; real time ultrasound.
Doppler
flowmeter;
inguinal
ligament;
INTRODUCTION Angulation of arterial grafts has long been suspected as a cause of premature graft occlusion. Collins, Field, and Castleden [l] reported four cases of thrombosis of leg arteries after prolonged travel, one of which occurred in a previously disobliterated iliac artery during a five-day coach trip. Kempczinski [2] studied femoropopliteal PTFE grafts and showed angiographically that graft kinking could occur on knee flexion. If significant kinking occurs it may predispose to graft occlusion. Prolonged travel might be a precipitating factor, with dehydration, stasis and sleep contributing to reduced arterial perfusion of the exPrevious ultrasound studies of arterial grafts have shown tremities. graft morphology [3,4,17] and associated complications [5,6]. In these studies grafts have been observed dynamically during joint flexion using real time B-mode ultrasound scanning (A.T.L. Duplex scanner).
PATIENTS
AND METHODS
A 5 MHz Duplex real time scanner with attached Doppler flowmeter was used to image grafts at the hip and knee joint'?.. This systan is a mechanical scanner which produces 30 B-mode images a second. Imaging can be interrupted with a foot switch which engages the Doppler flowmeter. This is a single gated 5 MHz pulsed Doppler blood velocity flowmeter and the position of the gate is displayed on the screen. The location of the sample volume can be adjusted by a control on the scanning head, so that Doppler signals can be obtained from any site in the vessel. Imaging is rapid and can be ICurrent 2Advanced
address: Technology
Royal
Hampshire
Laboratories,
County Seattle,
Hospital,
Winchester,
Washington,
U.K.
U.S.A.
0161-7346/82/010083-09$02.00/O
83
Copyright 0 I982 by Academic Press, Inc. All rights of reproduction in any form reserved.
CLIFFORD ET AL.
Fig.
1.
Real time B-mode ultrasound scanning and arteriography showing a patent right iliopopliteal Dacron graft. Blood velocity sampling by Doppler flowmeter shows adequate flow velocity.
maintained during active and passive joint movements. Hard copies from a photocopier are kept for subsequent measurement. Figure 1 shows a typical graft. Its distal anastomosis is visible for comparison with an arteriogram performed for assessment of left iliofemoral disease. Imaging of some varieties of synthetic graft may be difficult due to the high acoustic attentuation of the material. Ultrasound may not penetrate the anterior wall sufficiently to obtain a clear image of the posterior wall. In our studies with Dacron grafts this was easily overcome by adjusting the swept gain. Twenty-seven patients (25 male and 2 female) of mean age 61 years were selected from the followup vascular clinic. All had functioning Dacron arterial grafts of an original diameter range 8 to 12.5 mm. Eleven had had proximal aortoilio-femoral reconstructions between 2 and
84
BEHAVIOR OF ARTERIAL
Table
I.
Patient
Dacron
graft
GRAFTS
stenosis and kinking during by ultrasonic imaging.
Graft age (months)
Ultrasonic during O0
knee
diameter flexion 90"
flexion
demonstrated
Percent stenosis
1
7
7.5
5.0
33.3
2
40
6.1
5.0
18.0
3
32
8.0
4.0
50.0
4
30
9.0
4.1
54.4
5
10
9.0
4.1
54.4
6
3
8.0
7.6
6
20.3
7.8
5.4
curving
only
35.6
47 months (mean 26 months) previously and 16 had had iliopopliteal grafts between 3 and 49 months (mean 24 months) before assessment [12]. Patients were studied in a temperature controlled, electrically screened vascular laboratory following an equilibration period of 15 minutes. Patients were rested supine and then scanned anteriorly over the inguinal region, at the level of the inguinal ligament, at mid thigh level and also at the Three longitudinal and cross-sectional scans were knee if appropriate. copied at each level for a permanent record. Grafts were observed in real time during hip flexion from 0" to 80'; a permanent copy being made at 60" of flexion. The blood velocity/time waveform was observed proximally and distally to the inguinal ligament using the Doppler flowmeter at several stages during joint flexion. Studies at the knee during the range of flexion used during normal daily activity (0' to 120°) were made with the probe positioned posteriorly. Measurements were recorded at 0' and 90'. After 120' of flexion there was inadequate space behind the knee to accommodate the probe. RESULTS It immediately became apparent that kinking at the knee joint was intimately related to the proximity of the anastomosis to the joint line. Three groups were defined: those with grafts beyond the joint, those with anastomeses at or within 2 cm of the joint and those with more proximal grafts. Table I shows the degree of kinking in six grafts which crossed the joint to be anastomosed to the distal popliteal artery. Figure 2 depicts one of these six graphs and shows serious kinking at 90" knee flexion. Only one graft (3 months after implantation) did not kink. Five grafts displayed up to 54 percent stenosis, caused by graft kinking, when the knee flexed to 90'. In four, damping of the blood velocity/time waveform was not seen (probably due to the technical difficulties of imaging behind a flexed knee). In two cases the waveform was seriously damped due to graft lumen narrowing and further damping was noted on flexion. Table II gives the results of five cases where the anastomosis
85
CLIFFORD ET AL.
GRAFT KNEE
Fig. 2.
KINKING
300
FLEXED
9o”
Real time scan of iliopopliteal Dacron graft (anastomosis to distal popliteal artery) during knee flexion. At 90" of flexion there is graft kinking causing 54 percent lumen stenosis.
was completed at or within 2 cm of the knee joint line. These cases either kinked at the anastomosis or the artery was supple enough to accommodate the flexion. No blood velocity waveform damping was seen in these cases. Figure 3 shows a wide graft lumen during knee flexion to 9o". The remaining five patients in this group had grafts anastomosedto the proximal artery and were not affected by knee flexion. Studies demonstrated the normal curving of the popliteal artery.
Table II.
Patient
Kinking causing stenosis in grafts with anastomoses adjacent to the knee joint line. Graft age (months)
Ultrasonic diameter during flexion O0 90"
Percent stenosis
Comments
1
12
6.5
3.2
51.0
kink at anastomosis
2
9
9.1
4.0
56.7
kink at anastomosis
22.2
kink at anastomosis
3
49
9.3
7.2
4
24
9.5
9.0
6.0
5
4
9.0
9.0
Nil
86
artery
curving
BEHAVIOR OF ARTERIAL GRAFTS
Fig.
3.
Posterolateral scan of an iliopopliteal graft anastomosed at the knee jotnt line, No kinking occurred as the poziteal artery curved to accomodate 90' knee flexion.
fffteen woven or knitted Dacron grafts implanted to the profunda femoris artery of further distally were imaged during hip flexion. Graft age ranged from 2 to 29 months (mean 22.7 months). Studies between 0" and SO' of hip flexion failed to demonstrate graft kinking in the majority. Grafts curved up to 45" at 60' of hip flexion in 94 percent of cases as seen in figure 4. In only one case, was kinking noted at 60" of flexion and waveform damping was severe (Fig. 5). DISCUSSION [2,7-g]
Previous reports have mentioned and some have concluded that
graft there
87
kinking at the knee joint is a loss of longitudinal
CLIFFORD ET AL.
LlACRON
Fig.
4.
Anterior ligament
GRAFT
scan of a 10 mm Dacron graft at the ingu inal during hip flexion. No kinking is demon strated.
elasticity and a fall in flexibility which causes angulation and kinking with knee and hip flexion. Some authors have alluded to this as the cause of loss of graft patency and early occlusion 17.9) but few patients have been studied. Various surgical maneuvers have been suggested to avoid kinking, including the use of arterial autograft [8] composite Dacron and autogeneous vein grafts [lo] but these have not been taken up universally. Despite initial reports [7,13], graft kinking has now been reported in PTFE grafts [Z], which suggests that all prosthetic grafts may be subject to this phenomenon. Nearly 50 percent of the grafts we studied were patent at two or more years after implantation and most demonstrated
88
BEHAVIOR OF ARTERIAL GRAFTS
DACRON
HIP 0
GRAFT
KINKING
DURING
HIP
FLEXION
B SCAN
BLOOD
HIP
VELOCIT
60
60 '1,
Fig.
5.
STENOSIS
Scan at the hip showing unusual 60' hip flexion wfth associated
kinking of the graft at blood velocity damping.
kinking in one form or another, which suggests that kinking may not be an important factor in determining the long term patency of these grafts. However, kinking may well be a factor in acute graft occlusion following a long period of sustained knee flexion, such as during air travel. Acute arterial occlusion has been reported due to immobility associated with prolonged journeys and this may play a part in graft occlusion. Patients should be advised of this danger. It has been suggested that grafts, with surrounding fibrosis, crossing the inguinal ligament have a high rate of thrombosis, induced by kinking during hip flexion [8]. However, others have reported high late patency rates of grafts to the common femoral or profunda arteries (141. Division of the inguinal ligament for proximal and distal reconstruction has been advocated to reduce its potential unfavorable effect during hip flexion. Some groups routinely divide it during aortofemoral bypass, and others during distal reconstruction [11,15,16]. This division, it is claimed, leads to better postoperative results. Our hip studies indicate that this procedure is seldom justified and should be employed only when there is inadequate space under the ligament for the prosthesis. We were unable to demonstrate kinking in more than 90 percent of the Dacron grafts passing across the hip joint. CONCLUSION It alters
seems unlikely that kinking during joint graft long term patency as grafts studied
89
flexion significantly had been --in situ for an
CLIFFORD ET AL.
average of 20 months; acute graft occlusion Future more extensive further.
but it may be an important factor associated with following periods of sustained knee flexion. studies will help to define graft natural history
REFERENCES
[II
Collins, arteries
R. E., Field, S., and Castleden, W. M., Thrombosis of leg after prolonged travel, --Brit. Med. J. 2, 1478 (1979).
[21
Kempczinski, R. F., Physical characteristics of implanted polytetrafluoroethylene grafts, Arch. m. 114, 917-919 (1979).
[31
Clifford, P. C., Skidmore, R., Bird, D. R., Lusby, R. J., Baird, R. N., Woodcock, J. P., and Wells, P. N. T., Pulsed Doppler and realtime duplex imaging of Dacron arterial grafts, Ultrasonic Imaging, 2, 381-390 (1980).
[41
Bird, D. R., Giddings, A. E. B., Skidmore, R., Woodcock, J. P., and Baird, R. N., Doppler imaging of arterial grafts, Applied Radiology, Nov./Dee. 152-156 (1979).
[51
Gretchen, A. W., Gooding, M. D., Herzoz, K. A., Hedgcock, M. W., and Elsenberg, R. L., B mode ultrasonography of prosthetic vascular grafts, Radiology 127, 763-766 (1978).
161 Wolson, A. H., Kaupp, H. A., and McDonald, K., Ultrasound of arterial graft surgery complications, --Am. J. Radiology=, 869-875 (1979). [71
Burnham, S. J., Flanigan, D. P., Goodreau, J. S., Yao, J. S. T., and Bergan, J. J., Non-vein bypass in below-knee reoperation for lower limb ischaemia, Surgery 84, 417-424 (1978).
[81
Wylie, E. J., Vascular replacement with arterial 51, 14-21 (1965).
[91
Edwards, W. S., Late occlusion of femoral and popliteal fabric arterial grafts, m. Gynae. Obstet. 110, 214-718 (1960).
[lOI
Linton, R. R. and Wirthlin, L. S., Femoropopliteal composite Dacron and autogeneous vein bypass grafts, Arch. m. 107, 748-753 (1973).
[Ill
Cranley, J. J., in Vascular Surgery, Vol. 1, Peripheral Arterial Diseases, pp. 40-51, (Harper and Row, Hagerstown, 1972).
autografts,
Surgery
1121 Horton, R. E., Giddings, A. E. B., and Parkes, A. C., Iliopopliteal grafts as an alternative to amputation, Ann. &. Coil. M. a. 61, 217-218 (1979). experience with the polytetra[I31 Fry, P. D. and Robertson, M. E., Initial fluoroethylene graft for limb salvage, -Am. J. Surgery 136, 193-197 (1978). 1141 Moore, W. S.,
Cafferata, H. T., Hall, A. D., and Blaisdell, F. W., In defence of grafts across the inguinal ligament: an evaluation of early and late results of aorto-femoral bypass grafts, -Annals of Surg. 168, 207-214 (1968).
90
BEHAVIOR OF ARTERIAL GRAFTS
[15] Lord, J. W., Jr., Rossie, G., and Padula, G., The inguinal ligament. Its relation to post-stenotic dilatation of the common femoral artery, Bulletin-of em-- the New York Academy of Medicine, 55, 453-462 (1979). of arterial reconstruction below [16] Martin, P., A reconsideration inguinal ligament, J. Cardiovasc. m. 13, 24-29 ( 1972). [17]
the
Clifford, P. C., Woodcock, J. P., and Baird, R. N., The fate of the valves of autogenous vein grafts, 54, 348-350 --Br. J. Radiology, (1981).
91
IMAGING
4,
83-91
(1982)
BEHAVIOR OF ARTERIAL P. C. Clifford,1
GRAFTS AT THE HIP AND KNEE JOINTS
R. Skidmore,
Departments
J.
P. Woodcock,
of Surgery and Medical Bristol Royal Infirmary Bristol, U.K.
and R. N. Baird Physics
Real time ultrasonic scanning with a Duplex scanner (A.T.L.) was used to study Dacron arterial grafts crossing the hip and knee joints in 27 patients (25 males, 2 females), mean age 61 years. Ultrasonic imaging of the grafts was rapid and demonstrated kinking during knee flexion in 83 percent of grafts anastomosed to the distal popliteal artery. Only 7 percent of grafts crossing the inguinal ligament kinked during 60" of hip flexion. Graft associated
kinking during knee flexion may be a factor in acute thrombosis with long periods of immobility, such as during air travel.
Key words:
Arterial graft kinking; real time ultrasound.
Doppler
flowmeter;
inguinal
ligament;
INTRODUCTION Angulation of arterial grafts has long been suspected as a cause of premature graft occlusion. Collins, Field, and Castleden [l] reported four cases of thrombosis of leg arteries after prolonged travel, one of which occurred in a previously disobliterated iliac artery during a five-day coach trip. Kempczinski [2] studied femoropopliteal PTFE grafts and showed angiographically that graft kinking could occur on knee flexion. If significant kinking occurs it may predispose to graft occlusion. Prolonged travel might be a precipitating factor, with dehydration, stasis and sleep contributing to reduced arterial perfusion of the exPrevious ultrasound studies of arterial grafts have shown tremities. graft morphology [3,4,17] and associated complications [5,6]. In these studies grafts have been observed dynamically during joint flexion using real time B-mode ultrasound scanning (A.T.L. Duplex scanner).
PATIENTS
AND METHODS
A 5 MHz Duplex real time scanner with attached Doppler flowmeter was used to image grafts at the hip and knee joint'?.. This systan is a mechanical scanner which produces 30 B-mode images a second. Imaging can be interrupted with a foot switch which engages the Doppler flowmeter. This is a single gated 5 MHz pulsed Doppler blood velocity flowmeter and the position of the gate is displayed on the screen. The location of the sample volume can be adjusted by a control on the scanning head, so that Doppler signals can be obtained from any site in the vessel. Imaging is rapid and can be ICurrent 2Advanced
address: Technology
Royal
Hampshire
Laboratories,
County Seattle,
Hospital,
Winchester,
Washington,
U.K.
U.S.A.
0161-7346/82/010083-09$02.00/O
83
Copyright 0 I982 by Academic Press, Inc. All rights of reproduction in any form reserved.
CLIFFORD ET AL.
Fig.
1.
Real time B-mode ultrasound scanning and arteriography showing a patent right iliopopliteal Dacron graft. Blood velocity sampling by Doppler flowmeter shows adequate flow velocity.
maintained during active and passive joint movements. Hard copies from a photocopier are kept for subsequent measurement. Figure 1 shows a typical graft. Its distal anastomosis is visible for comparison with an arteriogram performed for assessment of left iliofemoral disease. Imaging of some varieties of synthetic graft may be difficult due to the high acoustic attentuation of the material. Ultrasound may not penetrate the anterior wall sufficiently to obtain a clear image of the posterior wall. In our studies with Dacron grafts this was easily overcome by adjusting the swept gain. Twenty-seven patients (25 male and 2 female) of mean age 61 years were selected from the followup vascular clinic. All had functioning Dacron arterial grafts of an original diameter range 8 to 12.5 mm. Eleven had had proximal aortoilio-femoral reconstructions between 2 and
84
BEHAVIOR OF ARTERIAL
Table
I.
Patient
Dacron
graft
GRAFTS
stenosis and kinking during by ultrasonic imaging.
Graft age (months)
Ultrasonic during O0
knee
diameter flexion 90"
flexion
demonstrated
Percent stenosis
1
7
7.5
5.0
33.3
2
40
6.1
5.0
18.0
3
32
8.0
4.0
50.0
4
30
9.0
4.1
54.4
5
10
9.0
4.1
54.4
6
3
8.0
7.6
6
20.3
7.8
5.4
curving
only
35.6
47 months (mean 26 months) previously and 16 had had iliopopliteal grafts between 3 and 49 months (mean 24 months) before assessment [12]. Patients were studied in a temperature controlled, electrically screened vascular laboratory following an equilibration period of 15 minutes. Patients were rested supine and then scanned anteriorly over the inguinal region, at the level of the inguinal ligament, at mid thigh level and also at the Three longitudinal and cross-sectional scans were knee if appropriate. copied at each level for a permanent record. Grafts were observed in real time during hip flexion from 0" to 80'; a permanent copy being made at 60" of flexion. The blood velocity/time waveform was observed proximally and distally to the inguinal ligament using the Doppler flowmeter at several stages during joint flexion. Studies at the knee during the range of flexion used during normal daily activity (0' to 120°) were made with the probe positioned posteriorly. Measurements were recorded at 0' and 90'. After 120' of flexion there was inadequate space behind the knee to accommodate the probe. RESULTS It immediately became apparent that kinking at the knee joint was intimately related to the proximity of the anastomosis to the joint line. Three groups were defined: those with grafts beyond the joint, those with anastomeses at or within 2 cm of the joint and those with more proximal grafts. Table I shows the degree of kinking in six grafts which crossed the joint to be anastomosed to the distal popliteal artery. Figure 2 depicts one of these six graphs and shows serious kinking at 90" knee flexion. Only one graft (3 months after implantation) did not kink. Five grafts displayed up to 54 percent stenosis, caused by graft kinking, when the knee flexed to 90'. In four, damping of the blood velocity/time waveform was not seen (probably due to the technical difficulties of imaging behind a flexed knee). In two cases the waveform was seriously damped due to graft lumen narrowing and further damping was noted on flexion. Table II gives the results of five cases where the anastomosis
85
CLIFFORD ET AL.
GRAFT KNEE
Fig. 2.
KINKING
300
FLEXED
9o”
Real time scan of iliopopliteal Dacron graft (anastomosis to distal popliteal artery) during knee flexion. At 90" of flexion there is graft kinking causing 54 percent lumen stenosis.
was completed at or within 2 cm of the knee joint line. These cases either kinked at the anastomosis or the artery was supple enough to accommodate the flexion. No blood velocity waveform damping was seen in these cases. Figure 3 shows a wide graft lumen during knee flexion to 9o". The remaining five patients in this group had grafts anastomosedto the proximal artery and were not affected by knee flexion. Studies demonstrated the normal curving of the popliteal artery.
Table II.
Patient
Kinking causing stenosis in grafts with anastomoses adjacent to the knee joint line. Graft age (months)
Ultrasonic diameter during flexion O0 90"
Percent stenosis
Comments
1
12
6.5
3.2
51.0
kink at anastomosis
2
9
9.1
4.0
56.7
kink at anastomosis
22.2
kink at anastomosis
3
49
9.3
7.2
4
24
9.5
9.0
6.0
5
4
9.0
9.0
Nil
86
artery
curving
BEHAVIOR OF ARTERIAL GRAFTS
Fig.
3.
Posterolateral scan of an iliopopliteal graft anastomosed at the knee jotnt line, No kinking occurred as the poziteal artery curved to accomodate 90' knee flexion.
fffteen woven or knitted Dacron grafts implanted to the profunda femoris artery of further distally were imaged during hip flexion. Graft age ranged from 2 to 29 months (mean 22.7 months). Studies between 0" and SO' of hip flexion failed to demonstrate graft kinking in the majority. Grafts curved up to 45" at 60' of hip flexion in 94 percent of cases as seen in figure 4. In only one case, was kinking noted at 60" of flexion and waveform damping was severe (Fig. 5). DISCUSSION [2,7-g]
Previous reports have mentioned and some have concluded that
graft there
87
kinking at the knee joint is a loss of longitudinal
CLIFFORD ET AL.
LlACRON
Fig.
4.
Anterior ligament
GRAFT
scan of a 10 mm Dacron graft at the ingu inal during hip flexion. No kinking is demon strated.
elasticity and a fall in flexibility which causes angulation and kinking with knee and hip flexion. Some authors have alluded to this as the cause of loss of graft patency and early occlusion 17.9) but few patients have been studied. Various surgical maneuvers have been suggested to avoid kinking, including the use of arterial autograft [8] composite Dacron and autogeneous vein grafts [lo] but these have not been taken up universally. Despite initial reports [7,13], graft kinking has now been reported in PTFE grafts [Z], which suggests that all prosthetic grafts may be subject to this phenomenon. Nearly 50 percent of the grafts we studied were patent at two or more years after implantation and most demonstrated
88
BEHAVIOR OF ARTERIAL GRAFTS
DACRON
HIP 0
GRAFT
KINKING
DURING
HIP
FLEXION
B SCAN
BLOOD
HIP
VELOCIT
60
60 '1,
Fig.
5.
STENOSIS
Scan at the hip showing unusual 60' hip flexion wfth associated
kinking of the graft at blood velocity damping.
kinking in one form or another, which suggests that kinking may not be an important factor in determining the long term patency of these grafts. However, kinking may well be a factor in acute graft occlusion following a long period of sustained knee flexion, such as during air travel. Acute arterial occlusion has been reported due to immobility associated with prolonged journeys and this may play a part in graft occlusion. Patients should be advised of this danger. It has been suggested that grafts, with surrounding fibrosis, crossing the inguinal ligament have a high rate of thrombosis, induced by kinking during hip flexion [8]. However, others have reported high late patency rates of grafts to the common femoral or profunda arteries (141. Division of the inguinal ligament for proximal and distal reconstruction has been advocated to reduce its potential unfavorable effect during hip flexion. Some groups routinely divide it during aortofemoral bypass, and others during distal reconstruction [11,15,16]. This division, it is claimed, leads to better postoperative results. Our hip studies indicate that this procedure is seldom justified and should be employed only when there is inadequate space under the ligament for the prosthesis. We were unable to demonstrate kinking in more than 90 percent of the Dacron grafts passing across the hip joint. CONCLUSION It alters
seems unlikely that kinking during joint graft long term patency as grafts studied
89
flexion significantly had been --in situ for an
CLIFFORD ET AL.
average of 20 months; acute graft occlusion Future more extensive further.
but it may be an important factor associated with following periods of sustained knee flexion. studies will help to define graft natural history
REFERENCES
[II
Collins, arteries
R. E., Field, S., and Castleden, W. M., Thrombosis of leg after prolonged travel, --Brit. Med. J. 2, 1478 (1979).
[21
Kempczinski, R. F., Physical characteristics of implanted polytetrafluoroethylene grafts, Arch. m. 114, 917-919 (1979).
[31
Clifford, P. C., Skidmore, R., Bird, D. R., Lusby, R. J., Baird, R. N., Woodcock, J. P., and Wells, P. N. T., Pulsed Doppler and realtime duplex imaging of Dacron arterial grafts, Ultrasonic Imaging, 2, 381-390 (1980).
[41
Bird, D. R., Giddings, A. E. B., Skidmore, R., Woodcock, J. P., and Baird, R. N., Doppler imaging of arterial grafts, Applied Radiology, Nov./Dee. 152-156 (1979).
[51
Gretchen, A. W., Gooding, M. D., Herzoz, K. A., Hedgcock, M. W., and Elsenberg, R. L., B mode ultrasonography of prosthetic vascular grafts, Radiology 127, 763-766 (1978).
161 Wolson, A. H., Kaupp, H. A., and McDonald, K., Ultrasound of arterial graft surgery complications, --Am. J. Radiology=, 869-875 (1979). [71
Burnham, S. J., Flanigan, D. P., Goodreau, J. S., Yao, J. S. T., and Bergan, J. J., Non-vein bypass in below-knee reoperation for lower limb ischaemia, Surgery 84, 417-424 (1978).
[81
Wylie, E. J., Vascular replacement with arterial 51, 14-21 (1965).
[91
Edwards, W. S., Late occlusion of femoral and popliteal fabric arterial grafts, m. Gynae. Obstet. 110, 214-718 (1960).
[lOI
Linton, R. R. and Wirthlin, L. S., Femoropopliteal composite Dacron and autogeneous vein bypass grafts, Arch. m. 107, 748-753 (1973).
[Ill
Cranley, J. J., in Vascular Surgery, Vol. 1, Peripheral Arterial Diseases, pp. 40-51, (Harper and Row, Hagerstown, 1972).
autografts,
Surgery
1121 Horton, R. E., Giddings, A. E. B., and Parkes, A. C., Iliopopliteal grafts as an alternative to amputation, Ann. &. Coil. M. a. 61, 217-218 (1979). experience with the polytetra[I31 Fry, P. D. and Robertson, M. E., Initial fluoroethylene graft for limb salvage, -Am. J. Surgery 136, 193-197 (1978). 1141 Moore, W. S.,
Cafferata, H. T., Hall, A. D., and Blaisdell, F. W., In defence of grafts across the inguinal ligament: an evaluation of early and late results of aorto-femoral bypass grafts, -Annals of Surg. 168, 207-214 (1968).
90
BEHAVIOR OF ARTERIAL GRAFTS
[15] Lord, J. W., Jr., Rossie, G., and Padula, G., The inguinal ligament. Its relation to post-stenotic dilatation of the common femoral artery, Bulletin-of em-- the New York Academy of Medicine, 55, 453-462 (1979). of arterial reconstruction below [16] Martin, P., A reconsideration inguinal ligament, J. Cardiovasc. m. 13, 24-29 ( 1972). [17]
the
Clifford, P. C., Woodcock, J. P., and Baird, R. N., The fate of the valves of autogenous vein grafts, 54, 348-350 --Br. J. Radiology, (1981).
91