The inflatable penile prosthesis (IPP) is the most commonly inserted penile prosthesis (PP) in the United States, with an estimated 20,000 cases per year.¹ The start of the modern era of the semirigid penile prosthesis (SRPP) began at the same time as the inflatable prosthesis. Both founding groups presented their initial series at the Annual AUA meeting in 1974. Despite this historical commonality, the SRPP now comprises only a minority of penile cases today in the United States of America with an estimate of approximately 10%-20% of all penile implant cases.^2,3 Our objective herein is to review and highlight some of the newest models on the market, as well as some surgical and clinical pearls from our current practice.

Contemporary SRPPs in the U.S. market only include malleable options, which are the Genesis (Coloplast) and the Tactra (Boston Scientific). The only mechanical model, the Spectra (Boston Scientific), is no longer being produced and currently has a very limited inventory in the market. Rigicon recently introduced its malleable SRPP to the U.S. market, the Rigi10. The Genesis is currently the only malleable implant with a hydrophilic coating available in the U.S.\

When IPPs and SRPPs are directly compared, the latter have the advantage of ease of use, superior mechanical reliability with reduced need for revision surgery, and a lower reported rate of mechanical failure. Inherent properties to consider in the use of SRPP include safety, ease of implantation, and ease of functionality, while concealability (flexibility/malleability) may be difficult.

Whilst there are no formal guidelines to favor the use of SRPP, there are a number of generally accepted indications. These are typically recommended in patients with limited manual dexterity³ and in the obese male population, as this obviates the potential difficulty of operating a scrotal pump secondary to body habitus. Additionally, certain patients with a history of multiple complex abdominal surgery, in which an alternate safe location for the reservoir is not present, may also benefit from these. SRPPs are also typically used in salvage implant cases.⁴ We have also had institutional success with SRPP placement at time of suprapubic fat pad excision and buried penis repair, in an effort to prevent retraction of the phallus. This is especially useful if a skin graft is used during the buried penis repair. Furthermore, the use of a malleable implant in patients suffering from erectile dysfunction with a buried penis (without any repair) and preexisting urinary difficulties has shown improvement in their peak urinary flow rate and International Prostate Symptom Score,⁵ especially as the SRPP provides tonicity and exposure to the penis, thus avoiding the difficulties of trying to hold a retracted phallus. Finally, SRPP can be an option for the patient who desires simplicity of function.

When appropriately selected, patient satisfaction rates can achieve levels similar to those of their inflatable counterparts.⁶ Among the SRPPs that have been on the market the longest (Genesis and Spectra), no superiority in terms of satisfaction rates have been demonstrated between them.⁷ Familiarity of the available product lines is an important educational aspect for providers who intend on utilizing this treatment modality. Important details such as sufficient axial rigidity for “thin” implants and sufficient flexibility for “thick” SRPPs, helps optimize satisfaction postoperatively.

Proper patient selection and appropriate counseling is of the utmost importance when considering implantation of a semirigid penile prosthesis, particularly in high-risk patients. Notable high-risk comorbidities that increase perioperative complication rates are poorly controlled diabetes mellitus, end-stage atherosclerotic cardiovascular disease, and end-stage renal disease (especially those on hemodialysis). In this high-risk population, the dreaded complication of perioperative glans necrosis (Fig. 1), can be especially increased, when high-risk adjunctive surgical maneuvers such as a subcoronal incision or a degloving circumcising incision, and perioperative use of occlusive elastic penile wrap is implemented.⁸ In addition, avoiding oversizing of the rods is critical to prevent distal ischemia from overcompression of the tissues distally.

Superficial skin necrosis can also occur in these high-risk populations (Fig. 2). This can arise even when “less invasive techniques” for implantation are employed, such as lateral distal corporal windows, given the tenuous blood supply. In our institutional experience, immediate explanation of the prosthesis, as opposed to conservative management alone, has been an effective means of addressing this clinical entity.

Clinical entities such as bothersome lower urinary tract symptoms or uncontrolled bladder outlet obstruction are prevalent among older patients and those with erectile dysfunction. It is not unreasonable to assess and address these prior to PP placement, especially preceding an SRPP implantation. Any transurethral procedure could potentially place the implant at risk and these procedures could be more challenging with an SRPP in place. The use of a long or extra-long resectoscope can be of some assistance, however these are not necessarily available in many institutions.⁹ In these cases, creation of a temporary perineal urethrostomy bypassing the implant and safely accommodating the resectoscope may be the best option.¹⁰

Given their different materials and components, the various SRPPs can support different axial loads.¹¹ As such, they can vary in flexibility, thereby directly playing a role in their concealability, which is one of the major concerns that patients have when considering this type of implant (Fig. 3). In our institutional experience, we have noted that regardless of the model, the materials, and the internal mechanism the malleable implant is composed of, those with larger girth will be more difficult to conceal. We have not noticed those issues with the mechanical implants, for which in our clinical practice we tend to favor the use of Boston Scientific’s Spectra. Unfortunately, this model is no longer being produced and only very limited quantities remain in circulation.

The semi-rigid penile prosthesis, while less commonly implanted in the U.S., is an excellent surgical option traditionally selected for patients with poor hand dexterity or multiple other comorbidities in which a quick and less invasive procedure is favored. Among those high-risk patients with multiple medical comorbidities, if an SRPP is to be placed, a thorough discussion with the patient about the potential devastating complications must be undertaken.

While many may consider semi-rigid implants to be less desirable than an inflatable device, in reality these implants can provide a safe and highly satisfying result. In our clinical and surgical opinion SRPPs should not be seen as an inferior implant when compared to the inflatable models. Currently with the 4 available models in the U.S., their great satisfaction rate, and mechanical durability, SRPPs could potentially be an option for any patient interested in a PP placement.