Allergan Medical - Comment

Dear Sir/Madam: Allergan’s comments on the Tissue Expander Guidance document published as a notice in Federal Register (Vol. 73, No. 246, 78372-3) on Monday, December 22, 2008 [Docket No. FDA–2008–D–0603], are provided below: 1. Page 2 Section §878.3600 Tissue Expander Device: Recommend changing 2nd sentence to: “It is made using an inflatable shell and filled over time with normal physiological saline (injection grade).” Reason: Should not limit TE design to silicone. Also to define that the filling with saline is not at one time but typically a series of fillings. 2. Page 3 Device Description: Recommend that the table not include shell thickness range because the expander includes patches, backings, areas of intended thickness gradients as well as injection port sites in the device all which may vary greatly in thickness. 3. Page 4 Section 6A: Material Property Testing of the Shell Recommend changing title from “Shell” to “Device” so all materials and components are accounted for. 4. Page 4 Section 6B: Injection Site Testing (2nd Paragraph) We recommend to using the criteria in ASTM Standard F1441 for Tissue Expander injection site performance. The total number of punctures would depend greatly on the size of the injection site and may not be relevant to its intended use. Since all injection sites, ports, self-sealing patches, valves, etc. within a tissue expander must perform similarly, a separate Section 6D is not necessary. However the phrase from 6D: “maintain the self-seal for the entire duration of use” should be included here in Section 6B. Therefore we recommend the 2nd paragraph of 6B would read: "In addition, we recommend you provide preclinical testing to show that the injection site will perform as intended for number, location, and size of punctures it is designed for. ASTM F1441 provides a typical test method: Apply 120mm Hg intraluminal pressure to the injection site using water or test media. Using the prescribed gauge needle, puncture a representative area of the injection site 5 consecutive times within a 1mm2 area. The injection site is considered leaking and fails the test if beads of fluid on the injection site surface are not static after 30 seconds. Testing should also demonstrate that the injection site will maintain the self-seal for the entire duration of use." 5. Page 4 Section 6C: Valve Competency Testing Change the term "postoperative filling" in 1st sentence to "intraoperative filling" because only the injection site is designed for postoperative filling. Also the pressure acceptance criteria for the Injection Site and the Intraoperative Valve should be the same. The ASTM F1441 for Tissue Expanders recommends 120mm Hg (equivalent to 163cm H2O) for injection sites. We recommend that this higher pressure be applicable to both the Injection Site and Intraoperative Valve. 6. Page 5 Section 6C: Valve Competency Testing We agree that loads and pressures used to test tissue expanders should exceed expected in vivo conditions, but we do not believe that filling expanders until they burst is practical or clinically relevant. Expanders are designed and labeled to be filled to a prescribed nominal fill volume with a small expected percent (%) overfill. Some elastomeric expanders can be expanded in vitro to many times (1000% +/-) their nominal size without failing. This capability is interesting but not clinically useful and may subject lab personnel to unnecessary risk. Like with saline filled breast implants, clinical failures of tissue expanders do not occur from bursting of the device from overfilling. We recommend that non-destructive testing be done as described in previous sections using internal pressures as the relevant parameter based on the expected fill amounts and applied loads with an appropriate margin of safety, e.g. 2 times. Destructive testing and potential failures modes might better be obtained from static rupture testing whereby an external load is applied in a compression mode until failure. 7. Page 5 Section 6D: Self-Sealing Patch Design Recommend deletion of this section as the proposed requirements are incorporated in Section 6B for Injection Site testing. 8. Page 7 Section 10: Directions for Use Recommend removing the “expiration date” requirement as this is a Class II device and expiration dating is not generally required.