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?