Since their original conception, inflatable penile prostheses have undergone many modifications and technological improvements resulting in decreased infection and revision rates as well as improved patient satisfaction (12). While significant research has been aimed at delineating patient risk factors, surgical techniques, and their optimization, many questions remain as to whether specific innovations have rendered a particular device superior (13).
Overall, the need for revision in the study was low (1.3%). This high rate of success in both devices speaks to the frequent innovation each prosthesis has undergone since their inception (12). These modifications, such as alterations in the tubing to prevent kinking, changes in more durable and infection-resistant coatings to the cylinders, rear tip extenders enabling better device fit, valves that prevent auto-inflation, and as shown in this series, fixing pump malfunctions which led to a product recall, have helped optimize both brands of devices for long-term success (14). Although, we obtained encouraging outcomes, a short period of follow-up may have limited the potential for uncovering a particular device's advantage as they undergo expected mechanical wear and tear over time (15).
Regarding the revision rate of the cohorts, we found no statistically significant difference among the two device groups. Again, this mirrors the current literature. Chung et al., in a retrospective evaluation of patients who underwent IPP placement for Peyronie’s disease, demonstrated no difference (p > 0.05) in the revision rate in AMS series versus Coloplast devices over five years (16). However, in contrast to our findings, they did note a small trend favoring AMS series.
Concerning the infection rate between AMS 700™ CX and Titan®, our study indicates device choice was not a significant prognostic factor. This outcome is similar to prior studies published in the literature. Dhabuwala et al., in their retrospective analysis, investigated IPP infection rates in groups with different anti-microbial coatings/washings specific to each device (17). This study also showed no significant difference in infection rate with 4.4% and 1.3% among Coloplast and AMS devices, respectively.
Our overall and virgin IPP infection rates were low in this study (0.18% and 0%, respectively) relative to the established literature (18). First-time placements have previously been shown to exhibit a typical infection rate ranging from 0.5–3% (18–21), with a higher risk in patients undergoing revision (22). As presented in this series, the only infectious episode was in a non-virgin IPP placement. Longer operative times have also been connected with higher rates of infection (10, 23). Although case time was not a significant factor for revision or infection in our analysis, our operative times were lower on average than previously published work (23). Surgeon expertise in a high-volume center and strict adherence to an infection prevention protocol also may have contributed to the low infection rate as well (24).
A unique aspect of this study was the exclusive placement of an intra-operative drain in all cases. This did not appear to increase infection or revision rate as previously discussed; since both were low as compared to published work. Drain placement has been a controversial point in the literature, with some authors more concerned about the risk of seeding an infection than the benefit of hematoma prevention (25). A large retrospective study focused on infection complications after drain placement previously showed no increase in infection rate (26). Our data corroborate this finding and show an even lower infection rate. Unfortunately, both ours and this previous study lack a direct comparison with a control group.
Diabetes mellitus was not found to be a risk factor for infection or revision in our analysis. As previously mentioned, evidence for diabetes as a true risk factor for complications has been inconsistent, with some studies supporting (27) and some contradicting the association (24, 28). Our findings align with Pineda et al. who, in a comprehensive review of IPP literature, could not conclusively name diabetes a risk factor for IPP infection or revision (10).
Moreover, our results did not show any significant association between reservoir location or shape and rates of revision. Although all seven reimplantation procedures occurred in patients with ectopic reservoir placements, none of the complications leading to revision were related to reservoir palpability, auto-inflation, erosion, or mechanical failure. Previous series have established the safety of ectopic reservoir placement within the abdominal wall as an alternative to the Space of Retzius (29, 30), and it has been successful in our center as the primary method of reservoir placement.
In summary, the strengths of our study are based on the prospective data collection, decreasing the potential sources of bias and confounding compared with the many retrospective series published. Concerning limitations, our series examines a single-surgeon, high-volume center cohort. As mentioned before, this may have led to lower-than-average infection and revision rates, which may mask some unseen patient or device risk factors and limit its reproducibility. This focused scope and prospective design, however, does help prevent the potential for confounding factors between the groups, such as surgeon expertise and/or technique.
Future directions could include longer-term follow-up to capture some potential differences in device durability over time. Additionally, a direct focus on patient satisfaction and ease of use would be an interesting area of study in a similar cohort of patients. We would also encourage multi-centered prospective randomized studies to verify and support our findings.