Introduction

The availability of sildenafil,¹ an effective oral phosphodiesterase type 5 inhibitor approved for the treatment of erectile dysfunction (ED), has tremendously increased both the number of patients seeking treatment and the number of physicians rendering such treatment. When oral therapy fails, is contraindicated, or results in side effects, alternate therapies are available. Approved second-line therapies include vacuum-constriction devices,² along with intracavernous and intraurethral administration of alprostadil.^3,4 Transcutaneous medi-cations⁵ and new oral medications^6,7,8 are under active investigation. Arterial^9,10 and/or venous^11,12 procedures are available for highly selected individuals. However, despite widespread enthusiasm for minimally invasive approaches, there are many men whose ED is refractory to such therapy. These men, not infrequently, elect penile prosthesis insertion.

Multiple-component inflatable penile prostheses (IPPs) provide adequate penile girth, length, and rigidity, while allowing flaccidity when not needed for sexual activity. A penile implant is the only ED treatment that allows a man to obtain and maintain a rigid erection at any time and for any length of time. They are not cumbersome like vacuum-constriction devices, and they avoid the penile/urethral discomfort and unpredictable response that often occurs with injectable or transurethral medications. Despite these advantages, many patients are reluctant to choose an implant because of the surgical procedure and its attendant risks, including subsequent device malfunction.

Currently available IPPs have greatly improved mechanical reliability compared to earlier models.¹³ Many series have reported overall mechanical reliability rates for these devices.^{14,15,16,17,18,19,20,21} The present series was compiled to document the exact site of malfunction of a large series of Mentor Alpha I devices, and to document any differences in the malfunction patterns of the scrotal and infrapubic versions.

Patients and methods

During a 12-year period, 463 men with organic impotence underwent implantation of a Mentor Alpha I IPP to correct organic erectile dysfunction. Patients undergoing primary or secondary implantation were included in this analysis. Preoperative evaluation for primary implant candidates typically included a detailed urologic and sexual history and physical examination. Laboratory evaluation included the measurement of serum testosterone, prolactin, glucose, creatinine, urinalysis, urine culture, and prostate-specific antigen levels. Most underwent duplex Doppler evaluation of penile hemodynamics before and after intracavernous injection of prostaglandin El, and/or nocturnal penile tumescence and rigidity testing. Written informed consent was obtained prior to IPP insertion. All men had tried and failed less invasive ED treatment modalities. All had sterile urine cultures preoperatively, and all received one intravenous dose of vancomycin and gentamicin prior to the skin incision. The operative techniques have been described previously.^22,23

Follow-up data were obtained from a review of medical records and operative reports. Only those patients who developed a device malfunction and returned for re-evaluation by the author were included. In all, 21 patients were excluded from the present analysis, including two intraoperative cylinder aneurysms caused by maximal cylinder inflation with an open corporotomy, two post-operative cylinder aneurysms related to device abuse,²⁴ and 17 (3.7%) who developed periprosthetic infection and were explanted.

Results

Of the 442 patients remaining for analysis, a total of 22 (5.0%) developed a device malfunction and returned to the author for evaluation. This included six (3.9%) of the 154 patients with infrapubic devices, and 16 (5.6%) of the 288 patients with scrotal devices. The length of time from implantation to device failure for these 22 patients is illustrated in Table 1. Nineteen of the 22 consented to reoperation, and form the basis of this report.

Table 1 - Time to implant failure.

Full table

The exact sites of malfunction of the scrotal and infrapubic devices are illustrated in Figure 1 and Figure 2, respectively. Of the six infrapubic implants that malfunctioned, two involved the junction of the silicone tubing with the reservoir strain relief, two involved the junction of the cylinder strain relief with the proximal cylinder, one involved the junction of the silicone tubing with the cylinder strain relief, and one declined revision (Figure 2). Of the 16 scrotal implants that malfunctioned, eight involved the junction of the silicone tubing from the reservoir with the pump strain relief, four involved the junction of the silicone tubing from a cylinder with the pump strain relief, one involved a direct leak from the pump bulb, one involved a leak from the body of the reservoir, and two declined revision (Figure 1). The reservoir leak occurred immediately after a laparotomy and colon resection, and it is strongly suspected that there was an operative injury to the reservoir. The most common type of malfunction seen in this series is illustrated in Figure 3.

Figure 1.

Exact malfunction sites of Mentor Alpha I scrotal implants.

Full figure and legend (31K)

Figure 2.

Exact malfunction sites of Mentor Alpha I infrapubic implants.

Full figure and legend (30K)

Figure 3.

22-gauge needle placed into site of leakage at junction of reservoir tubing with pump strain relief.

Full figure and legend (29K)

Discussion

The Mentor Alpha I prosthesis consists of two polyurethane cylinders preconnected to a pump via silicone tubing, and a separate reservoir. This prosthetic configuration requires only one connection, but necessitates an infrapubic and a scrotal version. The infrapubic cylinder/pump combinations have longer segments of silicone tubing between the cylinders and the pump, to allow for pump placement in the most dependent portion of the scrotum. In addition, in December 1992 the pump was enhanced so that the tubing and strain reliefs were reinforced and lengthened.²¹

In Randrup et al's¹⁴ 1993 series of 333 devices, nine (2.7%) developed a split in the exit tubing from the pump. However, this series predates the enhanced pump, and the malfunctions were not stratified by surgical approach.

Goldstein et al's¹⁷ 1993 multi-institutional series of 434 Alpha I's detected five cases (1.2%) of tubing leakage where the tubing entered/exited the pump, four of which occurred in scrotal devices. They found a statistically significant (P<0.001) greater chance for a tubing leak with a scrotal approach. The percentage of patients with an enhanced pump was not specified in their series.

Wilson et al's²¹ series of 1381 scrotal devices documented that the enhanced pump improved the mechanical reliability of the Alpha I scrotal device. However, the present series reveals that the most frequent sites of malfunction of the scrotal version continue to be the junctions of the silicone tubing with the pump strain reliefs. Interestingly, no patient in the present series had a malfunction of an unenhanced Alpha I pump.

The sites of malfunction found in the present series differed depending on whether a scrotal or infrapubic device/surgical approach was used. The scrotal device/surgical approach seems to increase the chance that a leak will develop at the tubing–strain relief junctions on the pump. The exact cause(s) of these findings are unclear. These findings may be due to chance alone. It should be noted that site-specific malfunction analysis could only be carried out on those patients who developed a malfunction and returned for reoperation by the author. This leaves open the possibility that some patients developed a malfunction and did not return to the author, or went elsewhere for treatment. However, prior investigators have documented a statistically significant greater risk for a tubing leak with the scrotal device/approach.¹⁷ It is conceivable that there are manufacturing differences between the scrotal and the infrapubic models, which may contribute to this malfunction pattern. It is also possible and even likely that the pump tubing is subject to different stresses depending on whether the infrapubic or scrotal model/approach is employed. Further investigation will be required to determine whether one or more of these factors is etiologic.

Conclusions

The Mentor Alpha I inflatable penile prosthesis is available in infrapubic and scrotal versions to accommodate either surgical approach. The present series suggests, but does not prove, that the exact site of device malfunction is typically different in the infrapubic vs scrotal versions. Analysis and knowledge of these malfunction patterns may assist the manufacturer in further improving the reliability of this implant, and can assist implanting surgeons in planning primary or secondary operative procedures.

References

1. Goldstein I et al. Oral sildenafil in the treatment of erectile dysfunction. N Engl J Med 1998; 338: 1397–1404. | Article | PubMed | ISI | ChemPort |
2. Levine LA, Dimitriou RJ. Vacuum constriction and external erection devices in erectile dysfunction. Urol Clin North Am 2001; 28: 335–341. | Article | PubMed | ChemPort |
3. Porst H. The rationale for prostaglandin E1 in erectile failure: a survey of worldwide experience. J Urol 1996; 155: 802–815. | Article | PubMed | ISI | ChemPort |
4. Leungwattanakij S, Flynn V, Hellstrom WJG. Intracavernosal injection and intraurethral therapy for erectile dysfunction. Urol Clin North Am 2001; 28: 343–354.
5. McVary KT et al. Topical prostaglandin El SEPA gel for the treatment of erectile dysfunction. J Urol 1999; 162: 726–731. | Article | PubMed | ISI | ChemPort |
6. Wagner G. Apomorphine SL (Uprima^R): a new treatment for the management of erectile dysfunction. Int J Imp Res 2001; 13 (Suppl 3): S1–S2.
7. Padma-Nathan H et al. On-demand IC351 (Cialis™) enhances erectile function in patients with erectile dysfunction. Int J Imp Res 2001; 13: 2–9. | Article |
8. Porst H et al. The efficacy and tolerability of vardenafil, a new, oral, selective phosphodiesterase type 5 inhibitor, in patients with erectile dysfunction: the first at-home clinical trial. Int J Imp Res 2001; 13: 192–199. | Article |
9. Lizza EF, Zorgniotti AW. Experience with the long-term effect of microsurgical penile revascularization. Int J Impot Res 1994; 6: 145–152.
10. Goldstein I, Hatzichristou DG, Pescatori ES. Pelvic, perineal, and penile trauma-associated arteriogenic impotence: pathophysiologic mechanisms and the role of microvascular arterial bypass surgery. In: Bennett AH, ed. Impotence. Diagnosis and management of erectile dysfunction. WB Saunders: Philadelphia, 1994, pp 213–228.
11. Wespes E, Moreire de Goes P, Sattar AA, Schulman C. Objective criteria in the long-term evaluation of penile venous surgery. J Urol 1994; 152: 888–890.
12. Lue TF, Donatucci CF. Dysfunction of the venoocclusive mechanism. In: Bennett AH, ed. Impotence. Diagnosis and management of erectile dysfunction. WB Saunders: Philadelphia, 1994, pp 197–204.
13. Montague DK, Angermeier KW. Penile prosthesis implantation. Urol Clin North Am 2001; 28: 355–361.
14. Randrup E et al. Clinical experience with Mentor Alpha I inflatable penile prosthesis. Report on 333 cases. Urology 1993; 42: 305–308. | PubMed |
15. Wilson SK, Wahman GE, Lange JL. Eleven years of experience with the inflatable penile prosthesis. J Urol 1988; 139: 951–952.
16. Garber BB. Mentor Alpha 1 inflatable penile prosthesis: patient satisfaction and device reliability. Urology 1994; 43: 214–217. | Article | PubMed | ISI | ChemPort |
17. Goldstein I et al. Safety and efficacy outcome of Mentor Alpha-1 inflatable penile prosthesis implantation for impotence treatment. J Urol 1997; 157: 833–839. | Article | PubMed | ISI | ChemPort |
18. Garber BB. Inflatable penile prosthesis: results of 150 cases. Br J Urol 1996; 78: 933–935.
19. Dubocq F et al. Long-term mechanical reliability of multicomponent inflatable penile prosthesis: comparison of device survival. Urology 1998; 52: 277–281. | Article | PubMed |
20. Govier FE et al. Mechanical reliability, surgical complications, and patient and partner satisfaction of the modern three-piece inflatable penile prosthesis. Urology 1998; 52: 282–286. | Article |
21. Wilson SK, Cleves MA, Delk JR. Comparison of mechanical reliability of original and enhanced Mentor Alpha I penile prosthesis. J Urol 1999; 162: 715–718. | Article | PubMed |
22. Garber BB, Marcus SM. Does surgical approach affect the incidence of inflatable penile prosthesis infection? Urology 1998; 52: 291–293. | Article | PubMed |
23. Garber BB. Outpatient inflatable penile prosthesis insertion. Urology 1997; 49: 600–603. | Article | PubMed |
24. Garber BB. Mentor Alpha-1 inflatable penile prosthesis cylinder aneurysm: an unusual complication. Int J Impot Res 1995; 7: 13–16.