Midterm Outcomes of a Novel Physician-Modified Inner-Branch Iliac Branch Device for Internal Iliac Artery Reconstruction

Abstract

The anatomical eligibility of the Iliac Branch Device (IBD) remains limited, primarily caused by the additional common iliac artery (CIA) space occupied by its outer branch. Given that East Asian populations typically have smaller CIA diameters and lengths than Western populations, the anatomical eligibility of IBD in East Asians is <30%. Thus, we developed a novel Physician-Modified Inner Iliac Branch Device (PM-IIBD) to reduce CIA spatial demands. The PM-IIBD was used for 10 patients’ internal iliac artery (IIA) reconstruction, achieving a 100% technical success with no perioperative complications. The 12-month postoperative CTA follow-up showed that no type I or III endoleaks and all EIA and IIA were patent. Seven cases showed sac shrinkage, and 3 showed sac stability. This study demonstrates the safety and efficacy of the PM-IIBD in CIA lesions. The PM-IIBD significantly reduces spatial demands on the CIA, expanding the anatomical eligibility for IBD.

Graphical abstract

Endovascular aneurysm repair (EVAR) offers a less-invasive alternative to open surgery for abdominal aortic aneurysms (AAA), reducing operative mortality and morbidity in anatomically suitable patients.¹ However, the presence of concomitant common iliac artery aneurysms (CIAAs), found in 15% to 45.5% of AAA cases, presents significant challenges to EVAR.² A critical factor for long-term success in EVAR is the establishment of a sufficient distal landing zone in a healthy segment of the common iliac artery (CIA), which helps to prevent complications such as type Ib endoleaks or stent migration.³ To achieve this, endografts are often extended to the external iliac artery (EIA), which may require either embolization or coverage of the internal iliac artery (IIA). However, sacrificing the IIA is associated with serious complications, including buttock claudication (28%-42%), erectile dysfunction (17%-24%), colonic ischemia (3.4%), and spinal cord ischemia (0.1%-0.3%).⁴ The 2024 Clinical Practice Guidelines of the European Society for Vascular Surgery emphasize the preservation of at least 1 IIA during EVAR whenever feasible.⁵ Although “bell-bottom,” “sandwich,” and “crossover” techniques exist, off-the-shelf iliac branch device (IBD) deliver superior early- to mid-term outcomes to maintain IIA.⁶ Nonetheless, anatomical eligibility for IBD remains limited. Only 26.9% to 52.9% of patients meet the instructions for use, with eligibility rates declining to 9% to 28.8% among East Asian patients because of their typically shorter and narrower CIAs.² This limitation is primarily attributable to the high spatial demands of the IBD’s outer branch. To address this challenge, we developed a novel Physician-Modified Inner-branch Iliac Branch Device (PM-IIBD) that minimizes spatial requirements. This study aimed to assess the midterm clinical safety and efficacy of PM-IIBD for IIA reconstruction.

Methods

Study design

This study adhered to the reporting guidelines of the Strengthening the Reporting of Observational Studies in Epidemiology Statement. From February 2023 to May 2024, 10 patients were enrolled from 2 centers after Institutional Review Board of the Chinese PLA General Hospital (S2023-597-01) and written informed consent. Inclusion criteria: 1) men with an AAA ≥55 mm or women with an AAA ≥50 mm combined with CIAA or isolated CIAA or IIAA with a maximum diameter ≥30 mm; 2) availability of computed tomography angiography (CTA) both preoperatively and at 12-month follow-up; and 3) patients with insufficient CIA diameter or CIA with mural thrombus who fail to meet the requirements of the Institutional Review Board’s Instructions for Use. Exclusion criteria: 1) age <18 years; and 2) pseudoaneurysms or infectious aneurysms.

Variables, data sources, bias, and definition

Patient demographic information and preoperative CTA scans were obtained from the hospital's electronic medical record system. All included patients had a triphasic thorax, abdominal, and pelvic CTA with 1-mm slices. Measurements were independently performed and repeated by 2 vascular surgeons (W.M.W. and Z.L.). If measurement discrepancies between the surgeons exceeded 30%, the chief vascular surgeon rendered the final decision (X.J.). At 12-month follow-up, a ≥5-mm reduction in aneurysm sac diameter is defined as sac shrinkage, an increase or reduction <5 mm as sac stability, and a ≥5mm increase as sac dilation.

Study outcomes

Primary safety endpoint: freedom from major adverse events (death, myocardial infarction, renal or hepatic failure, respiratory failure, spinal-cord ischemia or amputation within 30 days). Primary efficacy endpoint: immediate postoperative technical success, absence of type I and III endoleaks, patency of IIA branch stents, and no reintervention during follow-up.

PM-IIBD design and surgical procedure

The PM-IIBD design has been previously reported (Figure 1A).⁷ The IIBD was constructed using a limb stent (Medtronic) and an inner-branch—cut from a Viabahn covered-stent (W.L. Gore)—with a 15-mm length and diameter one-half that of the limb. First, the limb stent was on-table released, fenestrated with a cautery pen, and reinforced with a 0.018-inch coil ring (Cook Medical, Inc). The inner branch was sutured proximally and distally with 5.0 Prolene to ensure parallel alignment. Subsequently, a puncture needle was used to create an orifice in the proximal sheath of the delivery system, allowing passage of a preloaded 0.018-inch guidewire (Boston Scientific) through the inner branch and out of the proximal limb. Finally, the IIBD was compressed into a 20-F Medtronic delivery system. Under general anesthesia, both femoral arteries were cannulated. The preloaded 0.018-inch guidewire from the inner branch was established as a through-and-through guidewire between the bilateral femoral arteries. The PM-IIBD was delivered to the CIA bifurcation and partially released, with the fenestration aligned to the IIA origin. A 4-F catheter advanced via the through-and-through guidewire into the inner branch. Subsequently, a 0.035-inch guidewire was advanced through a 4-F catheter, traversed the inner branch, and entered the IIA, allowing deployment of the IIA branch stent. Finally, the PM-IIBD was fully deployed (Figure 1B).

Figure 1.

PM-IIBD Configuration and Clinical Application

(A) Comparison of the configuration between physician-modified inner iliac branch device and conventional IBDs in small-diameter common iliac artery (CIA). (B) Preoperative and 12-month follow-up of physician-modified inner iliac branch device implantation for CIA aneurysm with internal iliac artery (IIA) aneurysm, confirming external iliac artery (EIA) and IIA patency.

Statistical analysis

Continuous variables are expressed as medians along with IQRs, and categorical variables are reported as frequencies and percentages. The Intraclass Correlation Coefficient was used to assess interobserver variability. Sample size calculation was performed using a noninferiority design via PASS software (NCSS, LLC). All analyses were conducted using SPSS (version 26, IBM Corp) and MATLAB (MathWorks).

Results

Patient demographics and sample size calculation

This study included 10 patients, 80% of whom were men. The median age was 72.5 years (Q1-Q3: 68.8-78.5 years), and the median BMI was 23.22 kg/m² (Q1-Q3: 21.51-25.68 kg/m²). Among these patients, 40% (n = 4) had concurrent hypertension and 10% (n = 1) had concurrent diabetes mellitus. Additionally, 60% (n = 6) had a history of smoking, while 20% (n = 2) had a history of drinking history. Sample size calculation adopted a single-variable noninferiority test: literature review showed that the nonadverse event rate of the current IBD technique was 70% (P₀ = 0.70),⁶ while that of the clinical trial nonadverse event rate was 99% (P₁ = 0.99). Using the Binomial Enumeration method (maximum 10,000 experiments, Z-test [P₀] as the test type) with an α value set at 0.025 (Equation 1). For n = 10, the calculated power was 0.904 (achieved α = 0.0282), confirming the enrolled sample size was sufficient for the study. The Intraclass Correlation Coefficients for measurements by the 2 surgeons was 0.913, with its P value <0.001.

$$Z=\frac{P_1-P_0}{\sqrt{P_0\left(1-P_0\right)/n}},\text{reject}\text{if}Z>1.96\left[1\right]$$

PM-IIBD perioperative outcomes

The technical success rate for PM-IIBD implantation was 100% (10 of 10). The average procedure time was 161.25 ± 30.08 minutes. Postoperative digital subtraction angiography revealed that the IIBD was well-positioned, without type I or III endoleaks, stent migration, or kinking. The EIA and IIA remained patent. No major adverse events, including death, myocardial infarction, renal failure, hepatic failure, respiratory failure, spinal cord ischemia, limb amputation, infection, or puncture site complications, occurred during the perioperative period.

IIBD midterm follow-up outcomes

All patients completed the 12-month postoperative follow-up and CTA examination. The results showed no migration of the IIBD or IIA branch stents, no type I or III endoleaks, and no stenosis in the EIA or IIA. None of the patients experienced buttock claudication, erectile dysfunction, colonic ischemia, or spinal cord ischemia during the follow-up period. Additionally, there were no deaths or cardiovascular complications occurred. Seven sac shrank by ≥5 mm and 3 remained stable. The postoperative aneurysm max diameter was significantly reduced compared with the preoperative diameter (P = 0.005, t = 3.661) (Table 1).

Table 1.

PM-IIBD Size and Artery Diameter Changes Preimplantation and Postimplantation

Patient, #	Lesion	PM-IIBD (mm)	Inner branch (mm)	Pre-Max Diameter (mm)	Post-Max Diameter (mm)	Diameter Change (mm)
1	CIAA	16-16-120	8	32.6	27.4	−5.2
2	DAEAE	16-16-80	8	27.8	26.3	−1.5
3	CIAA	16-13-95	8	34.5	14.3	−20.2
4	IIAA	16-13-80	8	32.1	30.8	−1.3
5	AAA+CIAA	16-13-9	8	56.3	48.6	−7.7
6	CIAA	20-10-120	10	58.2	51.1	−7.1
7	AAA+CIAA	20-16-95	10	45.0	38.4	−6.6
8	AAA+CIAA	16-16-95	8	42.9	34	−8.9
9	AAA+CIAA	14-10-170	7	39.8	40.2	+0.4
10	CIAA	14-10-140	7	31.2	22.2	−9.0

AAA = abdominal aortic aneurysm; CIAA = common iliac artery aneurysm; DAEAE = distal aneurysmal expansion after EVAR; IIAA = internal iliac artery aneurysm; PM-IIBD = physician-modified inner branch iliac branch device.

Discussion

To address the clinical need for endovascular IIA reconstruction, a series of endovascular IIA-preserving strategies have been developed; yet, each has inherent limitations. Although the bell-bottom technique enables IIA preservation, it is only applicable to localized CIA lesions with a distal diameter <25 mm and carries risks of long-term CIA aneurysmal dilatation (35.3%) and endoleaks (17.6%), parallel stent techniques (sandwich and crossover techniques) are associated with a relatively high type I endoleak rate (6.5%) caused by gutter.⁶ IBD technique remains the most well-established off-the-shelf solution for IIA preservation during EVAR, with superior early- to midterm outcomes (97.35% technical success, 97.59% 30-day patency, and 94.32% follow-up patency).⁶ Despite these promising outcomes, the clinical utility of IBDs is constrained by strict anatomical requirements. Pearce et al⁸ noted that merely 35% of AAA cases complicated by CIAAs fulfill the anatomical criteria for current IBDs. This limitation is further accentuated in East Asian populations, attributed to their smaller and shorter CIAs.² A large-scale anatomical study by Wu et al² (1,144 East Asian AAA patients) showed that merely 18.9%, 21.8%, 11.9%, and 22.6% of cases met the anatomical criteria for the Cook ZBIS, Gore IBE, E-Liac IBD, and G-Iliac IBD, respectively. The primary anatomical constraint—insufficient CIA bifurcation diameter—affected 65.77% of patients. Reducing the CIA bifurcation diameter threshold to 16, 14, or 12 mm could improve IBD anatomical eligibility by 19.41%, 39.09%, and 54.45%, respectively.² These findings emphasize the necessity to adjust IBD designs for reduced CIA diameter requirements and broader anatomical applicability.

The inner-branch technique—with reduced intraluminal space occupation—has been successfully used for left subclavian artery and visceral artery preservation.⁹ However, no commercial inner-branch IBD systems currently dedicated to IIA preservation. To reduce CIA diameter requirements and improve anatomical eligibility in East Asian populations, we developed a novel PM-IIBD. Preliminary in vitro and computational fluid dynamics studies showed that an IIBD maintains IIA perfusion without inducing adverse CIA hemodynamic effects.¹⁰ We have also published the pioneering case report on promising midterm clinical outcomes of PM-IIBD application in patients with narrow-lumen CIAAs.⁷ In this study, we further assessed the midterm safety and efficacy of the PM-IIBD for diverse CIA lesions in a clinical investigation. The PM-IIBD was implanted in 10 CIA lesions, with a 100% technical success rate achieved. No adverse events, including type I or III endoleaks, stent migration, or stenosis, were observed during the perioperative period or 12-month follow-up. Seven patients exhibited aneurysm shrinkage, whereas 3 patient had stable aneurysm size. Importantly, no cases of buttock claudication, erectile dysfunction, colonic ischemia, or spinal cord ischemia occurred, demonstrating the clinical midterm efficacy and safety of the PM-IIBD. The advantages of the IIBD are as follows. First, it has reduced spatial requirements of CIA compared with existing IBDs. Second, it provides a longer proximal landing zone for the IIA branch stent (15 mm vs 10 mm in IBDs), lowering the risk of stent migration. Third, it facilitates the use of more flexible self-expanding stents in tortuous IIA anatomies, whereas existing IBDs often require balloon-expandable stents caused by limited landing zone length. However, the PM-IIBD still has issues to address for widespread clinical application. A primary concern is that, although the PM-IIBD can expand anatomical eligibility in East Asian populations, the inner-branch causes redistribution of blood flow in the EIA and IIA. Therefore, selecting an appropriate diameter for the inner branch to achieve optimal blood flow distribution will be a critical focus of future research. Additionally, the PM-IIBD still requires on-table physician modification, which significantly increases surgical time, complexity, and costs, limiting its applicability in resource-limited health care settings. Thus, we will explore the development and application of a commercial off-the-shelf IIBD to address these issues.

Study limitations

This study has 2 limitations: first, its small sample size may introduce selection bias, which future multicenter studies should address to enhance generalizability; and second, long-term follow-up is required to further validate the IIBD patency and complication rates.

Conclusions

This study demonstrates the midterm safety and efficacy of the novel PM-IIBD in CIA lesions. The PM-IIBD significantly reduces spatial demands on the CIA, expanding the anatomical eligibility for IBD technology. It shows promise as a viable solution for IIA preservation, particularly in East Asian populations.

Funding Support and Author Disclosures

This work was supported by the Natural Science Foundation of Beijing Municipality (7254314), National Natural Science Foundation of China (82170498), and the Beijing Science and Technology Planning Project (Z211100002921048). The authors have reported that they have no relationships relevant to the contents of this paper to disclose.