The Effect of Aging on Deformations of the Superficial Femoral Artery Resulting from Hip and Knee Flexion: Potential Clinical Implications

doi:10.1016/j.jvir.2009.08.027

Journal of Vascular and Interventional Radiology

Volume 21, Issue 2, February 2010, Pages 195-202

https://doi.org/10.1016/j.jvir.2009.08.027 Get rights and content

Purpose

Vessel deformations have been implicated in endoluminal device fractures, and therefore better understanding of these deformations could be valuable for device regulation, evaluation, and design. The purpose of this study is to describe geometric changes of the superficial femoral artery (SFA) resulting from hip and knee flexion in older subjects.

Materials and Methods

The SFAs of seven healthy subjects aged 50–70 years were imaged with magnetic resonance angiography with the legs straight and with hip and knee flexion. From geometric models constructed from these images, axial, twisting, and bending deformations were quantified.

Results

There was greater shortening in the bottom third of the SFA than in the top two thirds (top, 5.9% ± 3.0%; middle, 6.7% ± 2.1%; bottom, 8.1% ± 2.0% [mean ± SD]; P < .05), significant twist in all sections (top, 1.3°/cm ± 0.8; middle, 1.8°/cm ± 1.1; bottom, 2.1°/cm ± 1.3), and greater curvature increase in the bottom third than in the top two thirds (top, 0.15 cm⁻¹ ± 0.06; middle, 0.09 cm⁻¹ ± 0.07; bottom, 0.41 cm⁻¹ ± 0.22; P < .001).

Conclusions

The SFA tends to deform more in the bottom third than in the other sections, likely because of less musculoskeletal constraint distal to the adductor canal and vicinity of knee flexion. The SFAs of these older subjects curve off axis with normal joint flexion, probably resulting from known loss of arterial elasticity with age. This slackening of the vessel enables a method for noninvasive quantification of in vivo SFA strain, which may be valuable for treatment planning and device design. In addition, the spatially resolved arterial deformations quantified in this study may be useful for commercial and regulatory device evaluation.

Section snippets

Subjects and Imaging Protocol

Seven male adults, aged 50–70 years, were imaged with a General Electric 1.5-T Signa MR scanner (GE Medical Systems, Milwaukee, Wisconsin). Six of the seven volunteers had age-expected hypertension and hypercholesterolemia, but all were physically active and controlled their risk factors with medication. One subject had undergone coronary stent implantation after infarction, and another had smoked for 30 years; however, neither exhibited symptoms of cardiovascular disease. The subjects were

Results

Mean age among the seven male subjects was 56 years ± 5 (SD; range, 51–65 y); height was 178 cm ± 9 (range, 168–193 cm), and weight was 87 kg ± 9 (range, 73–98 kg). Their hip and knee flexion angles were 39° ± 6° (range, 32°–50°) and 86° ± 6° (range, 75°–93°), respectively. Quantitative deformation metrics of arc length change, axial twist rate, and maximum curvature change from supine to flexed positions for the subject population are shown in the Table, as are maximum curvatures for the

Discussion

For the population in this study, the observation that shortening of the SFA resulting from leg flexion was greater in the bottom third than in the top two thirds (P < .005) is likely because knee flexion was significantly greater than hip flexion (P < .001). In addition, the greater variability of arc length shortening in the top third of the SFA is likely because of the lesser musculoskeletal constraints around the hip versus the knee. The nonsignificant trend toward greater twisting in the

Acknowledgment

The authors thank Nathan M. Wilson, PhD, for assistance with the imaging processing software.

References (37)

C.P. Cheng et al.
Abdominal aortic hemodynamic conditions in healthy subjects aged 50-70 at rest and during lower limb exercise: in vivo quantification using MRI
Atherosclerosis
(2003)
M. Lazarus et al.
Evaluation of age, gender, heart rate and blood pressure changes and exercise conditioning on doppler measured aortic blood flow acceleration and velocity during upright treadmill testing
Am J of Cardiol
(1988)
R.T. Lyon et al.
Protection from atherosclerotic lesion formation by reduction of artery wall motion
J Vasc Surg
(1987)
A. Benetos et al.
Influence of age, risk factors, and cardiovascular and renal disease on arterial stiffness: clinical applications
Am J Hypertens
(2002)
B.H. Gray et al.
High incidence of restenosis/reocclusion of stents in the percutaneous treatment of long-segment superficial femoral artery disease after suboptimal angioplasty
J Vasc Surg
(1997)
M. Joner et al.
Pathology of drug-eluting stents in humans: delayed healing and late thrombotic risk
J Am Coll Cardiol
(2006)
M.H. Friedman et al.
Correlation between intimal thickness and fluid shear in human arteries
Atherosclerosis
(1981)
C.P. Cheng et al.
In vivo MR angiographic quantification of axial and twisting deformations of the superficial femoral artery resulting from maximum hip and knee flexion
J Vasc Interv Radiol
(2006)
A. Nikanorov et al.
Fracture of self-expanding nitinol stents stressed in vitro under simulated intravascular conditions
J Vasc Surg
(2008)
D. Scheinert et al.
Prevalence and clinical impact of stent fractures after femoropopliteal stenting
J Am Coll Cardiol
(2005)

O. Iida et al.

Effect of exercise on frequency of stent fracture in the superficial femoral artery

Am J Cardiol

(2006)

R.M. Berne et al.

Cardiovascular physiology

R.E. Zierler et al.

Hemodynamics for the vascular surgeon

T. Imura et al.

Non-invasive ultrasonic measurement of the elastic properties of the human abdominal aorta

Cardiovasc Res

(1986)

H. Yu et al.

Quantification of the pulse wave velocity of the descending aorta using axial velocity profiles from phase-contrast magnetic resonance imaging

Magn Reson Med

(2006)

A.P. Avolio et al.

Effects of aging on changing arterial compliance and left ventricular load in a northern Chinese urban community

Circulation

(1983)

S.E. Greenwald

Ageing of the conduit arteries

J Pathol

(2007)

C. Zarins et al.

Pathophysiology of human atherosclerosis

Cited by (64)

A method of assessing peripheral stent abrasiveness under cyclic deformations experienced during limb movement
2022, Acta Biomaterialia
Poor outcomes of peripheral arterial disease stenting are often attributed to the inability of stents to accommodate the complex biomechanics of the flexed lower limb. Abrasion damage caused by rubbing of the stent against the artery wall during limb movement plays a significant role in reconstruction failure but has not been characterized. Our goals were to develop a method of assessing the abrasiveness of peripheral nitinol stents and apply it to several commercial devices. Misago, AbsolutePro, Innova, Zilver, SmartControl, SmartFlex, and Supera stents were deployed inside electrospun nanofibrillar tubes with femoropopliteal artery-mimicking mechanical properties and subjected to cyclic axial compression (25%), bending (90°), and torsion (26°/cm) equivalent to five life-years of severe limb flexions. Abrasion was assessed using an abrasion damage score (ADS, range 1–7) for each deformation mode. Misago produced the least abrasion and no stent fractures (ADS 3). Innova caused small abrasion under compression and torsion but large damage under bending (ADS 7). Supera performed well under bending and compression but caused damage under torsion (ADS 8). AbsolutePro produced significant abrasion under bending and compression but less damage under torsion (ADS 12). Zilver fractured under all three deformations and severely abraded the tube under bending and compression (ADS 15). SmartControl and SmartFlex fractured under all three deformations and produced significant abrasion due to strut penetration (ADS 20 and 21). ADS strongly correlated with clinical 12-month primary patency and target lesion revascularization rates, and the described method of assessing peripheral stent abrasiveness can guide device selection and development.
Poor outcomes of peripheral arterial disease stenting are related to the inability of stents to accommodate the complex biomechanics of the flexed lower limb. Abrasion damage caused by rubbing of the stent against the artery wall during limb movement plays a significant role in reconstruction failure but has not been characterized. Our study presents the first attempt at assessing peripheral stent abrasiveness, and the proposed method is applied to compare the abrasion damage caused by Misago, AbsolutePro, Innova, Zilver, SmartControl, SmartFlex, and Supera peripheral stents using artery-mimicking synthetic tubes and cyclic deformations equivalent to five life-years of severe limb flexions. The abrasion damage caused by stents strongly correlates with their clinical 12-month primary patency and target lesion revascularization rates, and the described methodology can be used as a cost-effective and controlled way of assessing stent performance, which can guide device selection and development.
A computational study of fatigue resistance of nitinol stents subjected to walk‐induced femoropopliteal artery motion
2021, Journal of Biomechanics
Fatigue resistance of nitinol stents implanted in femoropopliteal arteries is a critical issue because of their harsh biomechanical environment. Limb flexions due to daily walk expose the femoropopliteal arteries and, subsequently, the implanted stents to large cyclic deformations, which may lead to fatigue failure of the smart self-expandable stents. For the first time, this paper utilised the up-to-date measurements of walk-induced motion of a human femoropopliteal artery to investigate the fatigue behaviour of nitinol stent after implantation. The study was carried out by modelling the processes of angioplasty, stent crimping, self-expansion and deformation under diastolic-systolic blood pressure, repetitive bending, torsion and axial compression as well as their combination. The highest risk of fatigue failure of the nitinol stent occurs under a combined loading condition, with the bending contributing the most, followed by compression and torsion. The pulsatile blood pressure alone hardly causes any fatigue failure of the stent. The work is significant for understanding and improving the fatigue performance of nitinol stents through innovative design and procedural optimisation.
Comparison of morphometric, structural, mechanical, and physiologic characteristics of human superficial femoral and popliteal arteries
2021, Acta Biomaterialia
Citation Excerpt :
The FPA is a long artery that smoothly tapers from the larger and more proximal SFA in the upper thigh to the smaller PA behind the knee without major branches or bifurcations [32,61]. Though both segments function in the same biological environment, the PA experiences more severe mechanical deformations during limb flexion [34,36,37,62], and is known to develop more vascular disease compared with the SFA [41]. The goal of our study was to compare the structural, morphometric, mechanical, and physiologic characteristics in these two FPA segments, and our results demonstrated that they indeed were significantly different; however, most of these differences were due to greater vascular disease in the PA.
Peripheral arterial disease differentially affects the superficial femoral (SFA) and the popliteal (PA) arteries, but their morphometric, structural, mechanical, and physiologic differences are poorly understood. SFAs and PAs from 125 human subjects (age 13-92, average 52±17 years) were compared in terms of radii, wall thickness, and opening angles. Structure and vascular disease were quantified using histology, mechanical properties were determined with planar biaxial extension, and constitutive modeling was used to calculate the physiologic stress-stretch state, elastic energy, and the circumferential physiologic stiffness. SFAs had larger radii than PAs, and both segments widened with age. Young SFAs were 5% thicker, but in old subjects the PAs were thicker. Circumferential (SFA: 96→193°, PA: 105→139°) and longitudinal (SFA: 139→306°, PA: 133→320°) opening angles increased with age in both segments. PAs were more diseased than SFAs and had 11% thicker intima. With age, intimal thickness increased 8.5-fold, but medial thickness remained unchanged (620μm) in both arteries. SFAs had 30% more elastin than the PAs, and its density decreased ~50% with age. SFAs were more compliant than PAs circumferentially, but there was no difference longitudinally. Physiologic circumferential stress and stiffness were 21% and 11% higher in the SFA than in the PA across all ages. The stored elastic energy decreased with age (SFA: 1.4→0.4kPa, PA: 2.5→0.3kPa). While the SFA and PA demonstrate appreciable differences, most of them are due to vascular disease. When pathology is the same, so are the mechanical properties, but not the physiologic characteristics that remain distinct due to geometrical differences.
The biomechanical impact of hip movement on iliofemoral venous anatomy and stenting for deep venous thrombosis
2020, Journal of Vascular Surgery: Venous and Lymphatic Disorders
Stenting of the iliofemoral vein may be an effective treatment to improve post-thrombotic symptoms. Iliofemoral vein stents have requirements different from those of lower extremity artery stents, and there is a paucity of literature regarding the biomechanical motion of the iliofemoral vein.
In a novel cadaveric model, stents were bilaterally inserted into the veins in the iliofemoral region. The veins were pressurized and underwent computed tomography angiography at various hip angle positions. In addition, 21 patients with iliofemoral vein disease had supine computed tomography angiography before and after stenting. The stents and vasculature were reconstructed into three-dimensional geometric models to quantify stent deformations and the interaction between the iliofemoral vein, inguinal ligament, and pubis bone due to hip flexion-extension.
In the cadavers, from supine to 30 to 45 degrees and 50 to 75 degrees of hip flexion, iliofemoral vein stents became less compressed (4.5% minor diameter expansion), and the inguinal ligament was separated from the iliofemoral veins by 1 to 3 cm in all hip positions. In the patients, the pubis compressed 47% of femoral veins; 78% were within 3 mm of the pubis. There was also evidence of contrast-enhanced flow disruption at the superior ramus.
The cadaver and clinical evidence shows that contrary to widely accepted dogma, the common femoral vein is not compressed by the inguinal ligament during hip flexion but rather by the superior ramus of the pubis during hip extension, which may have an impact on future stent design and influence deep venous thrombosis treatment strategies.
Length Redundancy and Twist Improve the Biomechanical Properties of Polytetrafluoroethylene Bypass Grafts
2019, Annals of Vascular Surgery
The iliofemoropopliteal artery significantly changes path length during normal hip and knee flexion. Prosthetic bypass grafts, such as polytetrafluoroethylene (PTFE) grafts, are relatively stiff and thus can subject graft anastomoses to high tension when the path length increases. The aim of this study was to examine the influence of length redundancy and twist on the biomechanical properties of PTFE bypass grafts.
Unreinforced and ring-reinforced PTFE grafts were loaded in an axial mechanical testing machine to measure the tensile and compressive axial forces with varying levels of length redundancy and axial twist.
Adding 5-15% length redundancy to a graft decreases the force to cause 5% extension by > 90% without substantially increasing shortening forces. Adding 4.5°/cm of axial twist imparts a corkscrew shape to the graft without increasing extension or shortening forces in the presence of length redundancy. Ring-reinforced PTFE grafts require more length redundancy to experience these reductions in forces especially in the presence of axial twist.
A modest amount of length redundancy and twist (i.e., a cork-screw condition) confers improved biomechanical properties in a PTFE graft, especially in ring-reinforced grafts. This should be taken into consideration when fashioning an arterial bypass graft in the iliofemoropopliteal segment.
An Animal Model of Human Peripheral Arterial Bending and Deformation
2019, Journal of Surgical Research
Designing peripheral arterial stents has proved challenging, as implanted devices will repetitively and unpredictably deform and fatigue during movement. Preclinical testing is often inadequate, given the lack of relevant animal models. The purpose of this study was to test the hypothesis that deformation of the human peripheral vasculature could be qualitatively and quantitatively modeled using an experimental animal.
Anteroposterior contrast angiography was performed in domestic Landrace-Yorkshire farm pigs. Images were obtained with the hind limbs naturally extended then repeated, (1) flexed approximately 90° at the hip and knee, (2) overflexed in a nonphysiological fashion. Quantitative vascular angiographic analysis was utilized to measure arterial diameter, length, and deformation. Percent axial arterial compression and bending were assessed.
Eight iliofemoral arteries in four animals were imaged. Mean luminal diameters of the iliac and femoral segments in the neutral position were 5.4 ± 0.5 mm and 4.6 ± 0.5 mm. Hind limb physiologic flexion induced profound arterial compression, 17 ± 8% and 29 ± 6% and bending, 36°±10° and 76° ± 13° within the iliac and femoral segments, respectively. With extreme flexion, the femoral artery could be reliably bent >90°. The observed findings exceeded the deformation observed historically within the human superficial femoral (∼5% compression and 10° bending) and popliteal artery (∼10% compression and 70° bending).
Significant nonradial deformation of the porcine iliofemoral arteries was observed during manual hind limb flexion and exceeded that typically observed in humans. This model constitutes a “worst case” scenario for testing deformation and fatigue of intravascular devices indicated for the human peripheral vasculature.

View all citing articles on Scopus

: This work was supported by members of the RESIStent SRI/Stanford Consortium on Stent Fracture in the Superficial Femoral Artery (phase II): Cordis/Nitinol Devices & Components, Boston Scientific, W.L. Gore & Associates, Medtronic Vascular, Abbott Vascular, and Bard/Angiomed. This work was also supported by National Institutes of Health grant P41RR09784, the Lucas Center for Magnetic Resonance Imaging at Stanford University, and General Electric Medical Systems.

: None of the authors have identified a conflict of interest.

: From the SIR 2009 Annual Meeting.

View full text

Clinical studyThe Effect of Aging on Deformations of the Superficial Femoral Artery Resulting from Hip and Knee Flexion: Potential Clinical Implications

Purpose

Materials and Methods

Results

Conclusions

Section snippets

Subjects and Imaging Protocol

Results

Discussion

Acknowledgment

Atherosclerosis

Am J of Cardiol

J Vasc Surg

Am J Hypertens

J Vasc Surg

J Am Coll Cardiol

Atherosclerosis

J Vasc Interv Radiol

J Vasc Surg

J Am Coll Cardiol

Am J Cardiol

Cardiovascular physiology

Hemodynamics for the vascular surgeon

Non-invasive ultrasonic measurement of the elastic properties of the human abdominal aorta

Cardiovasc Res

Quantification of the pulse wave velocity of the descending aorta using axial velocity profiles from phase-contrast magnetic resonance imaging

Magn Reson Med

Effects of aging on changing arterial compliance and left ventricular load in a northern Chinese urban community

Circulation

Ageing of the conduit arteries

J Pathol

Pathophysiology of human atherosclerosis

Clinical study
The Effect of Aging on Deformations of the Superficial Femoral Artery Resulting from Hip and Knee Flexion: Potential Clinical Implications