Portfindr: A Novel and More Accurate Device for Locating Tissue Expander Ports

Introduction

Two-stage tissue expander (TE)/ implant breast reconstruction is the most common method following mastectomy.  TE reconstruction can be associated with complications such as infection, seroma, and rupture [1].  Traditional TE port localization utilizes a small dangle magnet to help determine the needle entry point for expansion. Tissue thickness, fluid accumulation, or displacement of the TE can make precise port localization more difficult. More accurate localization of the magnetic fill port minimizes the risk of inadvertent puncture during access. We have developed a novel device, called PortFindr, to more accurately localize the subcutaneous expander fill port.

Methods

A single-blinded experiment was conducted to determine the accuracy of a traditional dangle magnet in comparison PortFindr.  A Sientra single port DermaspanTM tissue expander filled to 300ml was placed beneath three different foam skin equivalents (A 11mm, B 21mm, and C 32mm) by the non-blinded researcher.  The blinded researcher then used either the PortFindr or standard dangle magnet to determine the location of the port and insert a needle into the expander port. The distance of the needle to the center of the port was measured (mm) using an electronic caliper and the quadrant the of needle insertion was noted.  Thirty trials were completed for each parameter tested.  Additionally, the effect of distance on the force of magnetic attraction between the dangle magnet and the TE port was conducted using a tension force gauge.

Results

At each tissue thickness, the mean distance from center was significantly less in trials using the Portfindr compared to trials using the magnet (p<0.05). The mean distance from center using the Portfinder at thickness A, B, and C was 1.84mm, 2.39mm, and 5.48mm, respectively. The dangle magnet average distance from center was 3.03mm, 3.71mm, and 6.33mm. Standard deviation values were lower in trials using the Portfindr compared to the magnet in all tested thicknesses. Examination of the magnet’s mean force of attraction at thickness A, B, and C was 0.55N, 0.16N, and 0.04N, respectively, representing a statistically significant difference between attraction at A versus C (p<0.001).

Conclusion

Industry standard magnets lose significant magnetic attraction with increased distance from TE ports. Accurate port localization is important to prevent iatrogenic injury to the tissue expander during the expansion process. This benchtop study demonstrates that the PortFindr is significantly more accurate at locating the center of the port, than a dangle magnet, through all simulated thicknesses tested. Furthermore, precision, represented by standard deviation, was better in tests using the PortFindr. More accurate and precise localization of subcutaneous ports may help reduce complications.

References:

1. Adkinson JM, Miller NF, Eid SM, Miles MG, Murphy RX. Tissue Expander Complications Predict Permanent Implant Complications and Failure of Breast Reconstruction. Ann Plast Surg. 2015;75(1):24-28.