While penile prosthesis (PP) implantation is the surgical gold standard for patients with medication-refractory erectile dysfunction, patients with diabetes mellitus (DM) present a unique set of risk factors in this setting. Not only are vasculopathy, neuropathy, and metabolic syndrome inherent to the disease process of both erectile dysfunction and DM, but poor vascular circulation and improper wound healing may also contribute to higher rates of infection in this patient population. Several reports have cited up to 10 times increased risk of infection in patients with DM, with rates ranging from 1% to 3% on average but as high as 10.6% in patients with DM.¹

Since 1992, preoperative hemoglobin A1c (HbA1c) and serum glucose levels have been proposed as risk stratification tools to define controlled versus uncontrolled DM, and thus to predict infection risk in DM patients. Bishop et al first proposed a cutoff of 11.5% HbA1c to increase likelihood of infection following PP implantation;² however, this was contradicted by Wilson and colleagues in 1998 with a larger, prospective cohort of 289 patients.³ Across multiple cut points, repeated analysis with HbA1c as a continuous variable, and in subgroup analysis, Wilson et al did not find HbA1c to be a significant predictor of infection rates.

To consider infection rates in contemporary studies, however, we must also be aware of the changing landscape of PP implantation. Since the publication of these 2 initial studies, there have been several significant improvements in device manufacturing and surgical technique: the introduction of antibiotic-impregnated devices, hydrophilic coatings reducing bacterial adherence, and the “no-touch” surgical technique, to name a few. Mechanistically, these new innovations have altered infection risk profiles for the average patient undergoing PP implantation. Even further, however, concerns of immune dysfunction, a suitable environment for bacterial growth, and a decrease in antibacterial activity in patients with DM have been made moot by decreased inoculation via the “no-touch” surgical technique and via antibiotic-impregnated devices. A review by Christodoulidou and Pearce in 2016 found infection rates among diabetic men to be as low as 0.46% when these techniques and devices were employed.⁴

Within this new era of PP implantation, several groups have investigated HbA1c’s role. First was a study by Habous et al in 2017, finding patients with a HbA1c >8.5% to be approximately 4 times more likely to have an infected prosthesis.⁵ Important to consider with this conclusion, however, was a high infection rate (8.9% overall), the inclusion of low volume surgeons, a high percentage of semi-rigid devices, and the inclusion of nondiabetic patients. In such a cohort, it is unclear whether the correlation between HbA1c and infection rates was due to DM and its related comorbidities, rather than whether HbA1c itself was a true measure of diabetic control and its impact of infection. Similar considerations persisted in a retrospective review by Madbouly and colleagues in 2017.⁶

In 2018, Canguven and colleagues published the first study restricted to only diabetic patients.⁷ With a low infection rate of 0.67% in this “high risk” group of patients, the authors found no significant differences in average HbA1c levels of those with and without infection. These findings were then replicated by Osman et al in 2020, with 875 diabetic patients undergoing PP implantation at 18 institutions.⁸ With an infection rate of 3.8%, there were again no significant differences in HbA1c levels in those with and without infection. Rather, patients with a history of DM-related complications were found to be at nearly 2 times increased risk of infection and 2.4 times more likely to require device explantation. As opposed to use of HbA1c as the predictor of infection, this higher risk metric discriminated well among patients who did versus did not have an infection.⁸

Overall, current medical advances and surgical innovations have likely driven a drop in PP infection rates. However, this does not negate the role of patient-related factors in preventing PP infection. Of the aforementioned studies, several have pointed to other higher risk metrics predicting infection rate: a history of DM-related complications, an immunocompromised status or previous antibiotic resistance, for instance, discriminates well between those who may or may not have a successful outcome. Rather than utilizing HbA1c or preoperative blood glucose levels, these more generalized metrics may be more apt considerations for future trials.