scholarly journals Global Post-Market Clinical Follow-up of the Treovance Stent-Graft for Endovascular Aneurysm Repair: One-Year Results From the RATIONALE Registry

2018 ◽  
Vol 25 (6) ◽  
pp. 726-734 ◽  
Author(s):  
Raman Uberoi ◽  
Carlo Setacci ◽  
Mario Lescan ◽  
Antonio Lorido ◽  
David Murray ◽  
...  
Keyword(s):  
Stent Graft ◽  
Clinical Performance ◽  
Clinical Success ◽  
Endovascular Aneurysm Repair ◽  
Aortic Aneurysms ◽  
Type I ◽  
Technical Success ◽  
Major Morbidity ◽  
Aneurysm Repair

Purpose: To evaluate the safety and performance of the Treovance stent-graft. Methods: The global, multicenter RATIONALE registry ( ClinicalTrials.gov; identifier NCT03449875) prospectively enrolled 202 patients (mean age 73.0±7.8 years; 187 men) with abdominal aortic aneurysms (AAA) suitable for endovascular aneurysm repair (EVAR) using the Treovance. The composite primary safety endpoint was site-reported all-cause mortality and major morbidity. The primary efficacy outcome was clinical success. Further outcomes evaluated included technical success; stent-graft migration, patency, and integrity; endoleak; and aneurysm size changes. Results: Technical success was 96% (194/202); 8 patients had unresolved type I endoleaks at the end of the procedure. There was no 30-day mortality and 1% major morbidity (1 myocardial infarction and 1 bowel ischemia). Clinical success at 1 year was confirmed in 194 (96%) patients; 6 of 8 patients had new/persistent endoleaks and 2 had aneurysm expansion without identified endoleak. A total of 8 (4%) reinterventions were required during the mean 13.7±3.1 months of follow-up (median 12.8). At 1 year, the Kaplan-Meier estimate for freedom from reintervention was 95.6% (95% CI 91.4% to 97.8%). Other estimates were 95.5% (95% CI 91.7% to 97.6%) for freedom from endoleak type I/III and 97.4% (95% CI 94.2% to 98.9%) for freedom from aneurysm expansion. Thirteen (6.4%) patients died; no death was aneurysm related. Conclusion: The RATIONALE registry showed favorable safety and clinical performance of the Treovance stent-graft for the treatment of infrarenal AAAs in a real-world setting.

Outcomes of Endovascular Aneurysm Repair Using the Anaconda Stent-Graft

2020 ◽  
Vol 27 (3) ◽  
pp. 462-467
Author(s):  
Konstantinos Tigkiropoulos ◽  
Kyriakos Stavridis ◽  
Ioannis Lazaridis ◽  
Evangelos Bontinis ◽  
Ioulia Zournatzi ◽  
...  
Keyword(s):  
Stent Graft ◽  
Perioperative Complications ◽  
Endovascular Aneurysm Repair ◽  
Type I ◽  
Graft Occlusion ◽  
Technical Success ◽  
Significant Difference ◽  
Aneurysm Repair ◽  
Related Mortality

Purpose: To report outcomes of elective endovascular aneurysm repair (EVAR) using the Anaconda stent-graft in a tertiary vascular center. Materials and Methods: A retrospective study was conducted of 271 patients (mean age 71.5 years; 260 men) who underwent elective EVAR for abdominal aortic aneurysm using the Anaconda stent-graft from January 2006 to January 2017. Median aneurysm diameter was 58 mm (range 50–90). All patients were anatomically suitable for EVAR according to the 2003 version of the instructions for use. Follow-up included computed tomography angiography at 1, 6, and 12 months and yearly thereafter for the first 4 years and then every 2 years. Primary outcomes included technical success and 30-day aneurysm-related mortality and complications; secondary outcomes were overall and aneurysm-related mortality and aneurysm-related morbidity in follow-up. Results: The Anaconda stent-graft was implanted successfully in all patients. Primary and secondary technical success rates were 99.6% and 100%, respectively. Three patients (1.1%) died within 30 days of causes unrelated to the aneurysm, while 15 patients (5.5%) suffered perioperative complications. Median follow-up was 72 months (range 14–141). The overall type I endoleak rate was 4.7% (11 proximal, 2 distal). Late aneurysm-related complications were observed in 48 patients (17.3%); aneurysm-related mortality was 1.4% (n=4). Non-aneurysm-related mortality was 21.0% (n=57). Freedom from reintervention was 95.2% at 1 year, 98% at 2 years, and 90% at 6 years. There was no significant difference in the overall limb graft occlusion rate between the second- and third-generation devices. Conclusion: Results in our cohort study demonstrate that the Anaconda stent-graft has satisfactory early and late results with low aneurysm-related mortality.

Endovascular Aneurysm Sealing (EVAS) and Chimney EVAS in the Treatment of Failed Endovascular Aneurysm Repairs

2016 ◽  
Vol 24 (1) ◽  
pp. 115-120 ◽  
Author(s):  
Marwan Youssef ◽  
Sebastian Zerwes ◽  
Rudolf Jakob ◽  
Oroa Salem ◽  
Fritz Dünschede ◽  
...  
Keyword(s):  
Endovascular Aneurysm Repair ◽  
Multiple Organ ◽  
Aortic Aneurysms ◽  
Technical Success ◽  
Graft Thrombosis ◽  
Type Ia ◽  
Aneurysm Repair ◽  
Chimney Graft ◽  
Bifurcated Graft

Purpose: To assess the technical success and clinical outcome of reinterventions using the Nellix Endovascular Aneurysm Sealing (EVAS) System to treat complications after endovascular aneurysm repair (EVAR). Methods: Fifteen consecutive patients (mean age 79 years; 14 men) with prior EVAR were treated with EVAS between March 2014 and December 2015 at 2 institutions. The failed prior EVARs included 13 bifurcated endografts, 1 bifurcated graft plus fenestrated cuff, and 1 tube endograft. Endoleaks were the predominant indications: type Ia in 10 and type III in 5 (3 type IIIa and 2 type IIIb). All patients presented with progressive aortic aneurysms (median 7.85-cm diameter; range 6.5–11). Eight patients were treated on an urgent or emergency basis (6 symptomatic aneurysms and 2 contained ruptures). All patients underwent Nellix relining of the failed stent-graft; 10 had chimney (Ch) procedures in combination with EVAS (chEVAS) because the proximal landing zones were inadequate. Results: Technical success was 100%. All endoleaks were successfully sealed, and no additional intervention was required. No further endoleak after EVAS or chEVAS was recorded. Endobag protrusion occurred in 1 case without sequelae. One elderly patient with ruptured aneurysm died from multiple organ failure 2 months postoperatively. One renal artery guidewire injury led to nephrectomy because of active bleeding. No reinterventions, aneurysm-related mortalities, graft thrombosis, endoleaks, or chimney graft occlusions were observed during a median follow-up of 8 months (range 3–24). Conclusion: The present preliminary experience demonstrates that the use of EVAS/chEVAS is feasible for treatment of failed EVAR. This technique may be used as bailout or an alternative treatment when other established methods are infeasible or not available.

Type IIIb Endoleak After Endovascular Aneurysm Repair Using the Zenith Stent Graft

2019 ◽  
Vol 53 (6) ◽  
pp. 515-519
Author(s):  
Toshiya Nishibe ◽  
Toru Iwahashi ◽  
Kentaro Kamiya ◽  
Masaki Kano ◽  
Keita Maruno ◽  
...  
Keyword(s):  
Stent Graft ◽  
Endovascular Aneurysm Repair ◽  
Aneurysm Rupture ◽  
Type I ◽  
Stent Grafts ◽  
System Type ◽  
Type Iiib ◽  
Type I Endoleak ◽  
Aneurysm Repair

We present 3 cases of type IIIb endoleak after endovascular aneurysm repair (EVAR) using the Zenith stent graft system. Type III endoleak, like type I endoleak, is a high-pressure, high-risk leak that increases sac pressure up to or even above arterial pressure, and is associated with an increased frequency of open conversions or risk of aneurysm rupture. Type IIIb endoleak is rare but there is much concern that the incidence of type IIIb endoleak is likely to increase hereafter; the mechanism of type IIIb endoleak is deterioration of graft fabric in conjunction with stent sutures. Type IIIb endoleak is difficult to diagnose before rupture. The possibility of type IIIb endoleak should be highly suspected when the continued growth of an excluded aneurysm sac without direct radiologic evidence is observed during follow-up. Type IIIb endoleak can be repaired by relining of the stent graft with additional stent grafts.

Endovascular abdominal aortic aneurysm repair in patients with Marfan syndrome

Vascular ◽  
2019 ◽  
Vol 28 (1) ◽  
pp. 48-52
Author(s):  
Allan Marc Conway ◽  
Khalil Qato ◽  
Gautam Anand ◽  
Laurie Mondry ◽  
Gary Giangola ◽  
...  
Keyword(s):  
Marfan Syndrome ◽  
Open Repair ◽  
Aortic Surgery ◽  
Endovascular Aneurysm Repair ◽  
Aortic Aneurysms ◽  
Type I ◽  
Femoral Access ◽  
Abdominal Aortic ◽  
Aneurysm Repair

Objectives Marfan syndrome patients are at risk for aortic degeneration. Repair is traditionally performed with open surgery as this is deemed more durable. Endovascular aneurysm repair remains controversial. We report on the outcomes of Marfan syndrome patients with abdominal aortic aneurysms undergoing endovascular aneurysm repair. Methods The Vascular Quality Initiative registry identified 35,889 patients, including 29 with Marfan syndrome, treated with endovascular aneurysm repair from January 2003 to December 2017. Outcomes were analyzed per the Society for Vascular Surgery reporting standards. Results Median age was 70.0 years (IQR, 57.0–75.0), and 22 (75.9%) were male. Median aneurysm diameter was 5.3 cm (IQR, 4.9–6.3 cm), with an aortic neck length and diameter of 2.0 cm (IQR, 1.6–2.8 cm) and 2.5 cm (IQR, 2.2–2.8 cm), respectively. Twenty-one (72.4%) patients were asymptomatic, seven (24.1%) symptomatic, and one (3.4%) presented with rupture. Ten (34.5%) patients had prior aortic surgery. Six (20.7%) were unfit for open surgical repair. Length of stay was 2.0 days (IQR, 1.0–3.0 days). Percutaneous femoral access was performed in 15 (51.7%) patients with no complications. A type IA endoleak was present in one (3.4%), type IB in one (3.4%), and type II endoleak in two (6.9%) patients. There were no postoperative pulmonary, cardiac, or neurological complications. In-hospital mortality occurred in one (3.4%) patient who presented with a rupture and had been deemed unfit for open repair. A conversion to open repair was required. The patient expired on post-operative day 0. Early clinical success was achieved in 26 (89.7%) patients. Follow-up was available for 15 (51.7%) patients at a median time of 766 days (IQR, 653–937). There were no reinterventions or mortalities. Change in sac diameter was −0.6 cm (IQR, −1.1 to −0.2 cm), with no type I or III endoleaks. Discussion Endovascular aneurysm repair for patients with Marfan syndrome is feasible, and can be performed safely. Mid-term outcomes suggest this technique is durable. More robust long-term follow-up is needed.

Outcomes of endosutured aneurysm repair with the Heli-FX EndoAnchor implants

Vascular ◽  
2020 ◽  
Vol 28 (5) ◽  
pp. 568-576
Author(s):  
Georgios Karaolanis ◽  
Constantine N Antonopoulos ◽  
Stylianos Koutsias ◽  
George A Antoniou ◽  
Efthymios Beropoulis ◽  
...  
Keyword(s):  
Therapeutic Option ◽  
Meta Analysis ◽  
Endovascular Aneurysm Repair ◽  
Pooled Analysis ◽  
Aortic Aneurysms ◽  
Technical Success ◽  
Hostile Neck ◽  
Type Ia ◽  
Aneurysm Repair

Objective Endovascular aneurysm repair has gained field over open surgery for the treatment of abdominal aortic aneurysm. However, type Ia endoleak represents a common complication especially in hostile neck anatomy that is recently faced using endoanchors. We conducted a systematic review and meta-analysis to collect and analyse all the available comparative evidence on the outcomes of the endosuture aneurysm repair in patients with or without hostile neck in standard endovascular aneurysm repair. Methods The current meta-analysis was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All the prospective and retrospective studies reporting primary use of the Heli-FX EndoAnchor implants were considered eligible for inclusion in this study. The main study outcomes (technical success of endoanchor implantation, incidence of type Ia endoleak, aortic stent graft migration and the percentage of patients who presented regression or expansion of aneurysm sac throughout the follow-up) were subsequently expressed as proportions and 95% confidence intervals. Results Eight studies with a total of 968 patients were included in a pooled analysis. The technical success of the primary endoanchor fixation was 97.12% (95%CI: 92.98–99.67). During a mean six months follow-up period, a pooled rate of 6.23% (95%CI: 0.83–15.25) of the patients developed a persistent type Ia endoleak despite the primary implantation. Migration of the main graft was reported in five studies, in which a 0.26% (95%CI = 0.00–1.54) of the patients required an additional proximal aortic cuff. Regression of the aneurysm sac was observed at 68.82% (95%CI: 51.02–84.21). An expansion of the aneurysm sac was found in 1.93% (95%CI: 0.91–3.24) of the participants. The overall survival rate was 93.43% (95%CI: 89.97–96.29) at a mean six months follow-up period. Conclusions Endosuture aneurysm repair with the Heli-FX EndoAnchor implants seems to be technically feasible and safe either for prevention or for repair of intraoperative type Ia endoleak. Despite the primary implants of endoanchors, few cases of persistent type Ia endoleak and migration are still conspicuous. Long-term follow up is needed to determinate the role of this therapeutic option in the treatment of aortic aneurysms.

Early Computed Tomographic Angiography after Endovascular Aneurysm Repair: Worthwhile or Worthless?

Vascular ◽  
2008 ◽  
Vol 16 (5) ◽  
pp. 253-257 ◽  
Author(s):  
Evert J. Waasdorp ◽  
Joost A. van Herwaarden ◽  
Rob H.W. van de Mortel ◽  
Frans L. Moll ◽  
Jean-Paul P.M. de Vries
Keyword(s):  
Stent Graft ◽  
Endovascular Aneurysm Repair ◽  
Computed Tomographic Angiography ◽  
Type I ◽  
Type Ii ◽  
Graft Thrombosis ◽  
Computed Tomographic ◽  
Tomographic Angiography ◽  
Aneurysm Repair

This study evaluated the value of computed tomographic angiography (CTA) early after an endovascular aneurysm repair (EVAR) in relation to CTA 3 months after EVAR. We retrospectively reviewed all elective EVAR patients with available postprocedural and 3-month follow-up CTAs who were treated between 1996 and 2006. CTAs were analyzed for EVAR-related complications in terms of endoleaks, migration, and stent graft thrombosis. Secondary procedures and other complications within a 4-month time interval after EVAR were noted and analyzed for any association with the postprocedural CTA. During the study period, 291 patients (275 men), with a mean age of 71 years, underwent elective EVAR. All had postprocedural and 3-month follow-up CTAs, which detected 93 (32%) endoleaks (8 type I, 84 type II, 1 type III) and 1 stent graft thrombosis. These findings resulted in four secondary interventions (one interposition cuff, two extension cuffs, one conversion). All reinterventions were successfully done in an elective setting. During the first 3 postoperative months, five other reinterventions were required for acute ischemia in four patients (three Fogarty procedures, one femorofemoral crossover bypass) or groin infection in one patient. Eight patients died, but none of the deaths were related to abdominal aortic aneurysm or EVAR (four cardiac, two pulmonary, one gastric bleeding, one carcinoma). At 3 months, 43 endoleaks (3 type I, 40 type II), 3 stent graft thromboses, and 1 stent graft migration were seen. In two patients (0.7%), a new endoleak was diagnosed compared with the postprocedural CTAs. In 287 (99%) of 291 patients, the postprocedural CTA did not influence our treatment policy in the first 3 months after EVAR. More than half of the early endoleaks were self-limiting, and new endoleaks were seen in only two patients (< 1%) at the 3-month follow-up CTA. After an uneventful EVAR procedure, it is safe to leave out the early postprocedural CTA.

The use of thoracic stent grafts for endovascular repair of abdominal aortic aneurysms

Vascular ◽  
2017 ◽  
Vol 26 (3) ◽  
pp. 278-284 ◽  
Author(s):  
VP Bastiaenen ◽  
MGJ Snoeijs ◽  
JGAM Blomjous ◽  
J Bosma ◽  
VJ Leijdekkers ◽  
...  
Keyword(s):  
Endovascular Repair ◽  
Endovascular Aneurysm Repair ◽  
Aortic Aneurysms ◽  
Type I ◽  
Stent Grafts ◽  
Aortic Neck ◽  
Abdominal Aortic ◽  
Median Diameter ◽  
Aneurysm Repair

Objectives Stent grafts for endovascular repair of infrarenal aneurysms are commercially available for aortic necks up to 32 mm in diameter. The aim of this study was to evaluate the feasibility of endovascular repair with large thoracic stent grafts in the infrarenal position to obtain adequate proximal seal in wider necks. Methods All patients who underwent endovascular aneurysm repair using thoracic stent grafts with diameters greater than 36 mm between 2012 and 2016 were included. Follow-up consisted of CT angiography after six weeks and annual duplex thereafter. Results Eleven patients with wide infrarenal aortic necks received endovascular repair with thoracic stent grafts. The median diameter of the aneurysms was 60 mm (range 52–78 mm) and the median aortic neck diameter was 37 mm (range 28–43 mm). Thoracic stent grafts were oversized by a median of 14% (range 2–43%). On completion angiography, one type I and two type II endoleaks were observed but did not require reintervention. One patient experienced graft migration with aneurysm sac expansion and needed conversion to open repair. Median follow-up time was 14 months (range 2–53 months), during which three patients died, including one aneurysm-related death. Conclusions Endovascular repair using thoracic stent grafts for patients with wide aortic necks is feasible. In these patients, the technique may be a reasonable alternative to complex endovascular repair with fenestrated, branched, or chimney grafts. However, more experience and longer follow-up are required to determine its position within the endovascular armamentarium.

Preliminary Dual-Center Experience with the Bolton Treovance Endograft

2017 ◽  
Vol 51 (8) ◽  
pp. 533-537 ◽  
Author(s):  
Arron Thind ◽  
Dhruv Sarma ◽  
Abdel Kader Allouni ◽  
Feras Abdallah ◽  
David Murray ◽  
...  
Keyword(s):  
Aortic Aneurysm ◽  
Success Rate ◽  
Stent Graft ◽  
Type I ◽  
Complication Rates ◽  
Technical Success ◽  
Technical Success Rate ◽  
Average Maximum ◽  
Aneurysm Repair

Purpose: To present the performance and safety of the Treovance stent graft for endovascular aortic aneurysm repair in a “real-world” patient cohort. Methods: Patients from 2 centers, deemed unfit for open repair, were electively treated with the Treovance endograft. Clinical preoperative, operative, and up to 1-year postoperative follow-up data of patients were retrospectively analyzed. Results: This study included 46 patients with abdominal aortic aneurysm (44 male), mean age of 78 years ± 8 standard deviation (SD; range: 58-93 years). All met the manufacturer’s recommended anatomical requirements: average maximum sac diameter 63 mm ± 10 SD (range: 52-86 mm), proximal neck length 29 mm ± 12 SD (range: 11-60 mm), and neck angulation 30° ± 21 SD (range: 0°-70°). Fourteen had moderate to severe iliac tortuosity. A primary technical success rate of 80% was achieved (100% assisted primary technical success rate): 7 patients required adjunctive procedures intraoperatively and 2 successful treatments for type I endoleaks, which occurred within 24 hours postoperatively. There was 100% survival at 1-year follow-up; however, 4 (8.7%) patients required reintervention: 1 for a type I endoleak, 2 for limb stenosis, and 1 for a type II endoleak with an enlarging sac. No other device-related complications were identified. Reintervention and complication rates in hostile versus nonhostile anatomies were not statistically significant ( P = .28 and P = .42, respectively). Conclusion: The Treovance stent graft has a comparable safety profile to other next-generation stent grafts during the first year after endovascular aneurysm repair, which provides a rationale for further interrogation of its outcomes through clinical trials.

Parallel stent grafts for the treatment of complex aortic aneurysms: A single center study

Vascular ◽  
2018 ◽  
Vol 26 (5) ◽  
pp. 490-497 ◽  
Author(s):  
Daniel Silverberg ◽  
Uri Rimon ◽  
Daniel Raskin ◽  
Avner BarDayan ◽  
Moshe Halak
Keyword(s):  
Endovascular Aneurysm Repair ◽  
Primary Patency ◽  
Aortic Aneurysms ◽  
Single Center ◽  
Technical Success ◽  
Perioperative Morbidity ◽  
Single Center Experience ◽  
Invasive Techniques ◽  
Aneurysm Repair

Background “Chimney” techniques with parallel grafts used in order to extend the landing zones in endovascular aneurysm repair (ch-EVAR) are increasingly being reported. Conflicting data has been reported regarding the success and durability of the repair. We report a single center experience using ch-EVAR in treating complex aortic pathologies. Methods We performed a retrospective review of all patients treated with ch-EVAR in our institution between 2013 and 2017. Data collected included patients demographics, indications for surgery, configuration of parallel grafts, technical success, and perioperative morbidity and mortality. Follow-up data included aortic sac size, reintervention rate, and overall mortality. Results Thirty-five patients underwent treatment of their aneurysms with parallel grafts. Sixty parallel grafts were placed. Mean age was 75 years (range 59–93) and 30 (85%) were male. Technical success was achieved in 32 (91%) patients. Mean follow up was 12 months. Sac size decreased in diameter or remained unchanged in 26 of the 30 (86.6%) patients. Four patients were found to have enlarging aneurysms due to gutter endoleaks. All were treated successfully with endovascular methods. The estimated primary patency was 95% at 12 months. Probability of freedom from intervention was 75% at 12 months. No late aneurysm related mortality occurred. Conclusion The use of ch-EVAR in treating complex aortic aneurysms is technically feasible and safe. Gutter endoleaks are encountered only in a minority of the cases, and can be treated with minimally invasive techniques. Longer term follow up is required to evaluate the patency of these parallel grafts and the durability of the aneurysm exclusion.

scholarly journals Evolution of the Proximal Sealing Rings of the Anaconda Stent-Graft After Endovascular Aneurysm Repair

2018 ◽  
Vol 25 (4) ◽  
pp. 480-491 ◽  
Author(s):  
Maaike A. Koenrades ◽  
Almar Klein ◽  
Anne M. Leferink ◽  
Cornelis H. Slump ◽  
Robert H. Geelkerken
Keyword(s):  
Stent Graft ◽  
Endovascular Aneurysm Repair ◽  
Type I ◽  
Abdominal Aortic ◽  
Nominal Size ◽  
Computed Tomography Scans ◽  
Observational Cohort ◽  
The Difference ◽  
Aneurysm Repair

Purpose: To provide insight into the evolution of the saddle-shaped proximal sealing rings of the Anaconda stent-graft after endovascular aneurysm repair (EVAR). Methods: Eighteen abdominal aortic aneurysm patients were consecutively enrolled in a single-center, prospective, observational cohort study (LSPEAS; Trialregister.nl identifier NTR4276). The patients were treated electively using an Anaconda stent-graft with a mean 31% oversizing (range 17–47). According to protocol, participants were to be followed for 2 years, during which 5 noncontrast electrocardiogram-gated computed tomography scans would be conducted. Three patients were eliminated within 30 days (1 withdrew, 1 died, and a third was converted before stent-graft deployment), leaving 15 patients (mean age 72.8±3.7 years; 14 men) for this analysis. Evolution in size and shape (symmetry) of both proximal infrarenal sealing rings were assessed from discharge to 24 months using dedicated postprocessing algorithms. Results: At 24 months, the mean diameters of the first and second ring stents had increased significantly (first ring: 2.2±1.0 mm, p<0.001; second ring: 2.7±1.1 mm, p<0.001). At 6 months, the first and second rings had expanded to a mean 96.6%±2.1% and 94.8%±2.7%, respectively, of their nominal diameter, after which the rings expanded slowly; ring diameters stabilized to near nominal size (first ring, 98.3%±1.1%; second ring, 97.2%±1.4%) at 24 months irrespective of initial oversizing. No type I or III endoleaks or aneurysm-, device-, or procedure-related adverse events were noted in follow-up. The difference in the diametric distances between the peaks and valleys of the saddle-shaped rings was marked at discharge but became smaller after 24 months for both rings (first ring: median 2.0 vs 1.2 mm, p=0.191; second ring: median 2.8 vs 0.8 mm; p=0.013). Conclusion: Irrespective of initial oversizing, the Anaconda proximal sealing rings radially expanded to near nominal size within 6 months after EVAR. Initial oval-shaped rings conformed symmetrically and became nearly circular through 24 months. These findings should be taken into account in planning and follow-up.

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