# Presentation: 694256

## Session 3 – Device Integrity, Fatigue and Durability 

## Compiled Work Assignment Clinical and Explant Summary Regarding Implant Integrity, Fatigue and Durability

## Table 3.1: Clinical follow-up observations regarding loss of graft or suture integrity

|  | Number reported | Number of patients enrolled | Number of respondents |
| --- | --- | --- | --- |
| With observations | Number: 74 (10%)
Range: 1.0-27.9% | 741 | 3 |
| Without observations | Number: 0 | 235 | 1 |

**Table 3.1: Clinical follow-up observations regarding loss of graft or suture integrity**

## Table 3.2: Identified fractures

|  | Patients with fractures | Duration of Implantation  (# of months post-implant)* |  |  |  |  |  |  |  | Total |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  | 0-3 | 3-6 | 6-12 | 12-24 | 24-36 | 36-48 | 48-60 | 60+ |  |
| Connecting bar only | 2** |  |  |  |  |  |  |  |  | 2 |
| Stent only | 34 | 3 | 14 | 19 | 2 | 1 | 4 | 2 | 0 | 45 |
| Hook or barb | 6 | 0 | 0 | 2 | 4 | 0 | 0 | 0 | 0 | 6 |
| Total  | 42 | 3 | 14 | 21 | 6 | 1 | 4 | 2 | 0 | 53 |

- * pivotal study cohort from both radiographic and explant observations
- ** Respondent did not indicate how many months post-implant fractures occurred.

**(n****r**** with observations = 6, n****r**** without observations = 3)**

## Table 3.3: Sources of explanted devices  

| Source | Number from surgical conversion | Number from post-mortem autopsy | Total |
| --- | --- | --- | --- |
| From IDE clinical study | 122 | 41 | 163 |
| From US commercial sales | 55 | 17 | 72 |
| From OUS clinical studies | 1 | 0 | 1 |
| From OUS commercial sales | 75 | 18 | 93 |
| Total  | 253 | 76 | 329 |

- (nr = 9)

## Table 3.4: Explant fracture observations

| Observation |  | Duration of Implantation  (# of months post-implant) |  |  |  |  |  |  |  |  |  |  |  | Total |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  | 0-1 | 1-6 | 6-12 | 12-18 | 18-24 | 24-30 | 30-36 | 36-42 | 42-48 | 48-54 | 54-60 | 60+ |  |
| Connecting bar only |  | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Stent only |  | 0 | 5 | 3 | 22 | 17 | 17 | 6 | 9 | 5 | 4 | 1 | 1 | 90 |
| B
O
T
H | Connect-ing bar | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 |
|  | Stent | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 |
| Hook or barb |  | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Total  |  | 0 | 5 | 3 | 23 | 18 | 17 | 8 | 9 | 5 | 4 | 1 | 1 | 94 |

**(n****r**** with observations = 5, n****r**** without observations = 2)**

## Table 3.5: Additional explant observations

| Observation | Duration of Implantation  (# of months post-implant) |  |  |  |  |  |  |  |  |  |  |  | Total |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | 0-1 | 1-6 | 6-12 | 12-18 | 18-24 | 24-30 | 30-36 | 36-42 | 42-48 | 48-54 | 54-60 | 60+ |  |
| Graft material wear | 5 | 6 | 4 | 14 | 14 | 14 | 6 | 8 | 7 | 5 | 1 | 0 | 84 |
| Suture breaks | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Split seams | 2 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 |
| Wire wear | 0 | 1 | 0 | 2 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 7 |
| Total  | 7 | 8 | 5 | 16 | 17 | 15 | 6 | 8 | 7 | 5 | 1 | 0 | 95 |

**(n****r**** with observations = 5, n****r**** without observations = 2)**

## Fatigue and Durability

## Fatigue and Durability

- Failure modes to be evaluated
- Stent graft fatigue
- Material wear and abrasion
- Wear or abrasion between devices
- Stent fracture
- Migration
- Suture attachment

## Fatigue and Durability

- Sizes and configurations varied
- Worst case size based on FEA
- Maximum and minimum sizes
- Majority used straight mock arteries
- Two used angulated mock arteries
- Variations in test article
- Stent components vs. complete devices
- Test conditions
- Most did not include flow
- Pressures varied

## Fatigue and Durability

- Acceptance criteria
- Comparison to controls
- Lack of fractures
- No defects under specified magnification
- Statistically based fracture related criteria
- Characteristics not addressed
- Changes in morphology
- Tortuosity
- Atherosclerotic/diseased vessels
- Neck angulation

## Stress/Strain Analysis

## Stress/Strain Analysis

- All used FEA techniques
- Wide variety of methods used to determine boundary conditions
- Examination of clinical environment/manufacturing
- Worst case conditions per IFU
- Nonlinear model
- Physical and thermal stresses
- Compliant tube
- Porcine aorta

## Stress/Strain Analysis

- Conform to ISO Standard
- Failure modes seen clinically but not predicted
- Fatigue fractures
- Separation of the stent from the graft
- Characteristics not addressed
- Changes in morphology
- Tortuosity
- Atherosclerotic/diseased vessels

## Corrosion

## Corrosion

- All evaluated pitting, half evaluated crevice and half evaluated galvanic
- Acceptance criteria varied widely and depended upon the method used
- Characteristics not addressed
- Blood versus test solution differences

## Strength of Stent/Attachment System to Graft Bond

## Strength of Stent/Attachment System to Graft Bond

- All methods involve tensile test
- Graft material
- Sutures
- Both
- Conform to ISO Standard
- Variations in test article
- Stent components vs. complete devices
- Acceptance criteria varied
- Forces greater than suture strength
- Absolute force minimum (e.g., 2.0 lbs.)

## Strength of Stent/Attachment System to Graft Bond

- Characteristics not addressed
- Changes in morphology
- Tortuosity
- Atherosclerotic/diseased vessels
- Neck angulation