Research shows IPP tips are too sharp

[Doggedly_positive]

This research paper appears to demonstrate that the cylinder tips are sharper than the actual corpora cavernosa tips, leading one to wonder why they have been designed to be so sharp.

Would there be fewer instances of erosion if the IPP or malleable tips conformed more closely to those in the corpora?

https://pubmed.ncbi.nlm.nih.gov/23542138/

As an engineer, I've always doubted the design of the tips, believing that the point load at the tip is much higher than it needs to be and that a blunter tip would not be as likely to penetrate into the glans so easily.

The same thought applies to the RTEs, which appear even sharper.

Anyone have any more information?

[edjohn]

Would there be fewer instances of erosion if the IPP or malleable tips conformed more closely to those in the corpora?

Did you read it? "Our findings suggest that anatomically accurate corporal tips appear to be relatively blunt and that the new Titan silicone tip penile prosthesis more closely resembles the human corporal tip."

Also it's more than 13 years old. I am pretty sure the implants we are getting now have all been improved since then.

[Doggedly_positive]

Yes, of course I read it. That's why I posted it.

I don't know about the Titan, but the Rigicon and the AMS both exhibit sharper tips and RTE tips than the corpora that were measured. Did you see them?

My comment stands and I can see no reason for them to be the shape that they are.

[JohnnyBorg]

This is something Dr Hakky has commented on a bit - especially regarding malleables. He’s not super fond of the Coloplast Genesis tips since they aren’t as rounded out. Rigicon Rigi10 he’s more of a fan of since they more closely resemble the corporal bodies.

Now - from a standpoint of impact to the patient - I’m not sure how huge of a deal this is. I’ll ask him next time I talk to him in my pre-surgery consult. I think it’s really just one factor of many influencing things like comfort, for example. For erosion - I don’t think it has as big an impact as sizing in general does. Correct sizing is likely the most important factor. That’s why surgeons - ESPECIALLY with malleables - need to size realistically and at times conservatively depending on the patient. I think the main theory though is that the rounded tip is probably more comfortable for the patient since it’s shaped like the corporal body.

[edjohn]

I don't know about the Titan, but the Rigicon and the AMS both exhibit sharper tips and RTE tips than the corpora that were measured. Did you see them?

Like I said, the study is 13 years old and even at that time, the manufacturers were updating their designs as is the point of the study (as they said the “new at that time” Titan was already much better). For any of this to be truly relevant today you need to know for certain that whatever AMS spec they were using at that time has not been changed in 13 years, and I don’t think we can do that without some really detailed factory info that I have not seen around here.

May still be an issue, may not be.

Also, the study scanned n=2 penises (and not live erections, from cadavers at that). It would be insane to assume it is an accurate representation of all penises. I do agree that rounder and softer is probably better than what we have, but I seriously doubt the issue is as serious as it sounds. It is definitely not as bad as it was with older models, and even back then you were not seeing massive rates of erosion.

[lasthope2.0]

Fascinating study by Dr. Hakky and colleagues. Thank you for sharing!

I see this anatomical study was done on 4 corporas from 2 cadaveric phalluses.

I’m attaching an outline generated using the image from the paper showing the polyurethane mold of the cadaveric corporas.

The newer generation malleable distal tips (attached) like those of the Tactra/Rigi10, appear to be more forgiving.

A reduced taper may also impart higher lateral pressure, even if axial tip pressure can be less in theory.

It would be valuable if manufacturers could fund studies on real-world outcomes with larger sample sizes to account for anatomic variations, potential SST deformities from suboptimal glans support offered by blunter tips on narrower distal anatomy, extrusion rates and patient satisfaction.

A study on the varying tip designs of these FDA approved malleables can offer some real-world hypothesis for future IPP designs.

[edjohn]

The newer generation malleable distal tips (attached) like those of the Tactra/Rigi10, appear to be more forgiving.

You have to remember, though, the malleables are all pretty narrow compared to the inflatables, so the curve of the tips is not much different in practice and of course the fact that they never retract to a “flaccid” state means they are worse in the context of forward pressure already.

[lasthope2.0]

The newer generation malleable distal tips (attached) like those of the Tactra/Rigi10, appear to be more forgiving.

You have to remember, though, the malleables are all pretty narrow compared to the inflatables, so the curve of the tips is not much different in practice and of course the fact that they never retract to a “flaccid” state means they are worse in the context of forward pressure already.

Many surgeons have adopted the practice of implanting rods that are 1 cm shorter than the measured length. While this may not be ideal from the patient's perspective, it theoretically reduces the risk of distal pressure necrosis which is the most feared complication of malleables. However, the real-world + statistically robust impact of this proactive technique on extrusion outcomes has yet to be determined. It would be valuable to see more studies validating such biologically plausible theories.