Titan vs. AMS CX: Tunica Dependence vs. Tunica Independence & Natural Erections

[sambalamba]

When selecting a penile implant, one major factor that is brought up by some docs (Dr. Eid for example) is whether the device is "tunica-dependent" or "tunica-independent" in how it expands and provides rigidity. From reading through many articles my understanding is that this distinction plays a critical role in how an implant behaves over time, especially considering variations in the tunica albuginea, the fibrous tissue surrounding the erectile chambers.

Coloplast Titan: A Tunica-Dependent Implant

The Coloplast Titan is described as "tunica-dependent", meaning that its cylinders will expand in girth until they reach the resistance of the tunica albuginea. Unlike the AMS CX, which has an internal mesh restricting girth expansion to 18mm ± 2mm, the Titan does not have a built-in limit on expansion.

• If the tunica is strong and thick, the Titan cylinders expand against it, achieving optimal rigidity and girth.

• If the tunica is weak or thinned, the Titan may continue expanding beyond its nominal diameter, leading to potential over-expansion over time. This could result in a wider but less rigid penis, as excessive stretching could reduce axial support.

• For the maximum possible girth expansion I've heard that the 21+mm Titan may expand to ~23-24mm, depending on the tunica’s condition.

AMS CX: A Tunica-Independent Implant

The AMS 700 CX is considered "tunica-independent" because its girth is limited by an internal mesh. Unlike the Titan, the CX does not rely on the tunica albuginea to define its final expansion—it expands only up to 20mm at most, regardless of tunica strength.

• If the tunica is strong, the CX still expands to its preset diameter, potentially leading to a slightly flatter appearance in wide penises.

• If the tunica is weak, the implant will maintain its designed girth without over-expanding, preserving better rigidity over time.

• This controlled expansion makes the CX a preferred choice for men with Peyronie’s disease, fibrosis, or thinner tunicas, as it prevents over-expansion and maintains consistent rigidity.

How This Relates to a Natural Erection

Interestingly, a natural erection is also "tunica-dependent", much like the Coloplast Titan.

• During a natural erection, blood fills the corpora cavernosa, expanding them until the tunica albuginea reaches its limit.

• If the tunica is strong, a natural erection achieves full girth and rigidity.

• If the tunica is weak, venous leakage can occur, resulting in difficulty maintaining an erection—similar to how an over-expanded Titan might lose some rigidity over time.

The AMS CX differs from a natural erection because its internal mesh limits expansion, meaning it doesn’t rely on the tunica to determine its final size.

Which Implant Works Best in Different Scenarios?

• For men with a strong, wide tunica → Titan is better because it expands fully and maximizes girth and rigidity.

• For men with a weak or thinned tunica → AMS CX is better because it prevents over-expansion and maintains rigidity.

• For men with Peyronie’s disease or fibrosis → CX is preferred because its controlled expansion ensures predictable sizing.

• For men who want maximum rigidity and width → Titan is better, but only if their tunica can support the expansion without long-term atrophy.

Seeking Further Input
Given these differences, I would love to hear from those who have experience with either the Coloplast Titan or AMS CX implants. How has tunica strength affected your implant’s performance over time? Have you noticed any loss of rigidity or girth expansion beyond what was expected?

Would you also say that a natural erection and a Titan behave similarly in terms of tunica dependence, or do you see key differences in how the two function?

[horemheb]

Hi Sambalamba,
Compared to my life before getting the penile prosthesis, my penile girth has increased. I now have a penile circumference that I had never achieved during natural erections in my entire life. Every time I inflate my implant, I reach the same width and rigidity, almost identical to the previous inflation at millimetrically level. Regarding rigidity, my wife also says she experiences a level of firmness she has never felt before. I understand now, what is tunica dependent. I think AMS CX was right option for me...

[ElbowRoom]

Interesting. It seems like it might be a theoretical issue...I have never heard of a Titan losing firmness over time, unless the device fails.

Has anyone actually experienced this?

[ElbowRoom]

FWIW, I asked Grok:

Being tunica-dependent, do Titan IPPs lose firmness of erections over time?
Understanding the Coloplast Titan Inflatable Penile Prosthesis (IPP)

The Coloplast Titan is a three-piece inflatable penile prosthesis (IPP) designed to treat erectile dysfunction (ED) by providing on-demand erections through manual inflation of fluid-filled cylinders placed within the corpora cavernosa (the erectile tissue of the penis). These cylinders are made from Bioflex®, a durable biopolymer that expands to mimic natural rigidity. The device is "tunica-dependent" because the tunica albuginea—the fibrous outer sheath of the corpora cavernosa—encases and supports the inflated cylinders, helping to maintain axial rigidity (straightness and firmness during penetration) and prevent buckling or kinking.

This tunica dependence is a key design feature of narrow-based IPPs like the Titan, distinguishing them from wide-based alternatives (e.g., certain AMS models) that may provide more intrinsic support. While the tunica's structural integrity is crucial for optimal performance, it does not inherently lead to progressive loss of erection firmness over time in the Titan IPP, based on available clinical data and biomechanical studies.
Does Firmness Degrade Over Time?

No, Titan IPPs do not typically lose erection firmness due to tunica dependence alone. Here's a breakdown of the evidence:

Biomechanical Durability and Rigidity: The Titan's cylinders demonstrate superior resistance to forces simulating penetration (longitudinal load) and gravity (horizontal load) compared to competitors like the AMS 700 LGX. In ex vivo testing, the Titan maintained rigidity across various fill pressures, with less dependence on over-inflation for stability—meaning the tunica's role enhances rather than hinders performance. Rigidity scores remain high even in longer cylinders (≥24 cm), which are common for maximizing length without compromising firmness.
Long-Term Mechanical Survival Rates: Clinical studies report excellent durability:
5-year mechanical survival: 87–90% for Titan IPPs.
15-year overall survival for IPPs (including Titan): ~60%, with most failures due to pump issues rather than cylinder/tunica-related firmness loss. These rates indicate that the device holds up well, with no evidence of tunica-dependent degradation causing widespread firmness reduction.
Tunica-Related Factors: While long-standing ED (pre-implant) can cause tunica fibrosis or elasticity loss, leading to potential penile shortening or reduced girth, this is mitigated post-implant through:
Aggressive cylinder sizing: Using narrow-length measurement techniques (NLMT) and longer cylinders to stretch the tunica during surgery.
Postoperative rehabilitation: Daily inflation (1–2 hours for 6–12 months) prevents capsular contracture (fibrous tissue buildup around the cylinders), preserving length, girth, and firmness. In a prospective study of 40 Titan patients, 93% maintained or improved dimensions at 1 year, with high satisfaction.
Potential Complications Affecting Perceived Firmness: Firmness issues are rare and usually not progressive:
Pump malfunctions: ~5–8% experience temporary "stuck valve" (pseudo-malfunction), resolved by firm pumping—no surgery needed.
Tissue contracture: Can cause scrotal firmness or auto-inflation (~1–2% risk), but this doesn't affect penile erection rigidity.
Overall revision rate: ~10% at 5 years, mostly for infection or mechanical failure, not tunica degradation.

Recommendations

If you're considering or have a Titan IPP, follow your surgeon's rehab protocol to optimize tunica health and firmness. Complications like firmness loss are uncommon and often reversible without revision. Consult a urologist for personalized assessment, as individual factors (e.g., Peyronie's disease, diabetes) can influence outcomes. Coloplast offers a lifetime replacement warranty for mechanical failures.

[lasthope2.0]

Attached are case report images of uncontrolled girth expansion.

From a video by Dr. Brian Christine:
https://youtu.be/miwdYjYSW54?si=277_3Knm0QW2SW2u

[Thisworld]

When selecting a penile implant, one major factor that is brought up by some docs (Dr. Eid for example) is whether the device is "tunica-dependent" or "tunica-independent" in how it expands and provides rigidity. From reading through many articles my understanding is that this distinction plays a critical role in how an implant behaves over time, especially considering variations in the tunica albuginea, the fibrous tissue surrounding the erectile chambers.

Coloplast Titan: A Tunica-Dependent Implant

The Coloplast Titan is described as "tunica-dependent", meaning that its cylinders will expand in girth until they reach the resistance of the tunica albuginea. Unlike the AMS CX, which has an internal mesh restricting girth expansion to 18mm ± 2mm, the Titan does not have a built-in limit on expansion.

• If the tunica is strong and thick, the Titan cylinders expand against it, achieving optimal rigidity and girth.

• If the tunica is weak or thinned, the Titan may continue expanding beyond its nominal diameter, leading to potential over-expansion over time. This could result in a wider but less rigid penis, as excessive stretching could reduce axial support.

• For the maximum possible girth expansion I've heard that the 21+mm Titan may expand to ~23-24mm, depending on the tunica’s condition.

AMS CX: A Tunica-Independent Implant

The AMS 700 CX is considered "tunica-independent" because its girth is limited by an internal mesh. Unlike the Titan, the CX does not rely on the tunica albuginea to define its final expansion—it expands only up to 20mm at most, regardless of tunica strength.

• If the tunica is strong, the CX still expands to its preset diameter, potentially leading to a slightly flatter appearance in wide penises.

• If the tunica is weak, the implant will maintain its designed girth without over-expanding, preserving better rigidity over time.

• This controlled expansion makes the CX a preferred choice for men with Peyronie’s disease, fibrosis, or thinner tunicas, as it prevents over-expansion and maintains consistent rigidity.

How This Relates to a Natural Erection

Interestingly, a natural erection is also "tunica-dependent", much like the Coloplast Titan.

• During a natural erection, blood fills the corpora cavernosa, expanding them until the tunica albuginea reaches its limit.

• If the tunica is strong, a natural erection achieves full girth and rigidity.

• If the tunica is weak, venous leakage can occur, resulting in difficulty maintaining an erection—similar to how an over-expanded Titan might lose some rigidity over time.

The AMS CX differs from a natural erection because its internal mesh limits expansion, meaning it doesn’t rely on the tunica to determine its final size.

Which Implant Works Best in Different Scenarios?

• For men with a strong, wide tunica → Titan is better because it expands fully and maximizes girth and rigidity.

• For men with a weak or thinned tunica → AMS CX is better because it prevents over-expansion and maintains rigidity.

• For men with Peyronie’s disease or fibrosis → CX is preferred because its controlled expansion ensures predictable sizing.

• For men who want maximum rigidity and width → Titan is better, but only if their tunica can support the expansion without long-term atrophy.

Seeking Further Input
Given these differences, I would love to hear from those who have experience with either the Coloplast Titan or AMS CX implants. How has tunica strength affected your implant’s performance over time? Have you noticed any loss of rigidity or girth expansion beyond what was expected?

Would you also say that a natural erection and a Titan behave similarly in terms of tunica dependence, or do you see key differences in how the two function?

Excuse my lack of understanding, but from what i know even the titan has a maximum diameter expansion (21mm), so what does it mean that it keeps expanding against the tunica? Can it go over 21mm?

[Kodixx]

sambalamba, thanks for the post -- apparently I missed this back in Feb. It may explain why at 9mo post-op, I only feel a trace of pain when pumped to max inflation. I have a CX and am 7" L and almost 6" G when engorged. I'm now wondering if the CX cylinders have reached the maximum girth of their internal mesh, as described in your post. That would mean they're no longer pushing against the tissue, hence only a trace of pain and continuing to decrease.

- Chuck

AMS CX: A Tunica-Independent Implant its girth is limited by an internal mesh. the implant will maintain its designed girth without over-expanding, preserving better rigidity over time. I would love to hear from those who have experience with either the Coloplast Titan or AMS CX implants.

[sambalamba]

Excuse my lack of understanding, but from what i know even the titan has a maximum diameter expansion (21mm), so what does it mean that it keeps expanding against the tunica? Can it go over 21mm?

The Titan's 21mm diameter is measured at 15psi pressure as per Coloplast. I have cut the tube that goes to the reservoir, dipped it into a bottle of water and inflated it on a table to about 22.7mm in diameter for the regular Titan and for the 17mm NB Titan I have done the same and achieved about 20 mm.

Based on this my assumption is that if there is extra fluid in the reservoir a Titan can be inflated beyond 21mm. Clavell has a video showing the same.

But I would also point out the diameter increase is not infinite. At some point the inward pressure of the implant material would be so much that it will be impossible for the pump to overcome that pressure.

Hope that helps

[sambalamba]

sambalamba, thanks for the post -- apparently I missed this back in Feb. It may explain why at 9mo post-op, I only feel a trace of pain when pumped to max inflation. I have a CX and am 7" L and almost 6" G when engorged. I'm now wondering if the CX cylinders have reached the maximum girth of their internal mesh, as described in your post. That would mean they're no longer pushing against the tissue, hence only a trace of pain and continuing to decrease.

- Chuck

AMS CX: A Tunica-Independent Implant its girth is limited by an internal mesh. the implant will maintain its designed girth without over-expanding, preserving better rigidity over time. I would love to hear from those who have experience with either the Coloplast Titan or AMS CX implants.

Hey Chuck, I think it is quite possible. My analysis tells me first you have the implant material then pseudo capsule then leftover corporal tissue and then you hit the tunica. When you fully inflate the cylinder it will try to go to its max achievable diameter. It will in the process compress the leftover corporal tissue. Then the compressed tissue and the cylinder will hit the tunica which will prevent further expansion in girth. For a CX it will max acheive 18mm+/-2mm diameter. Once that's achieved no more additional pressure on the leftover corporal tissue or the tunica. This is my understanding of the whole mechanism.

One other thing when I have tried to inflate the CX after some point it becomes ultra ultra difficult to press the pump and get it to inflate anymore, much more difficult than the Titan. Although after some point the Titan also become harder to inflate but not as hard as the CX.

[Thisworld]

Excuse my lack of understanding, but from what i know even the titan has a maximum diameter expansion (21mm), so what does it mean that it keeps expanding against the tunica? Can it go over 21mm?

The Titan's 21mm diameter is measured at 15psi pressure as per Coloplast. I have cut the tube that goes to the reservoir, dipped it into a bottle of water and inflated it on a table to about 22.7mm in diameter for the regular Titan and for the 17mm NB Titan I have done the same and achieved about 20 mm.

Based on this my assumption is that if there is extra fluid in the reservoir a Titan can be inflated beyond 21mm. Clavell has a video showing the same.

But I would also point out the diameter increase is not infinite. At some point the inward pressure of the implant material would be so much that it will be impossible for the pump to overcome that pressure.

Hope that helps

Thanks man