Development and Validation of the Satisfaction Survey for Inflatable Penile Implant (SSIPI)

Carolyn A. Salter MD; Philip Vu Bach MD; Lawrence Jenkins MD; Nelson Bennett MD; Faysal A. Yafi MD; Farouk el Khatib MD; Elizabeth Schofield MPH; Nicole Benfante MS; Stanley E. Althof PhD; Christian J. Nelson PhD; John P. Mulhall MD, MSc, FECSM, FACS

FIRST PUBLISHED: August 6, 2021 – The Journal of Sexual Medicine 

DOI: https://doi.org/10.1016/j.jsxm.2021.06.020 

Introduction

Before the development of the Satisfaction Survey for Inflatable Penile Implant (SSIPI), a validated English-language patient reported outcome tool assessing patient satisfaction with penile prostheses was not available. 

Satisfaction rates were previously determined with other tools, such as assessments for erectile function. However, those tools were not designed to evaluate inflatable penile implant (IPP) satisfaction. 

Another implant satisfaction questionnaire was validated in Italian, but deemed unsuitable for English speakers and did not include questions specific to inflatable prostheses. 

This study discusses the development and validation of the SSIPI. 

Methods

Questionnaire Development

Researchers completed a thorough literature review, and 6 penile implant experts identified 4 areas to be addressed in a penile implant satisfaction survey: 

• Pain (“discomfort following implant surgery”)
• Appearance (“concealability, naturalness of erection and length/girth”)
• Function (“ease of use and ability to utilize the scrotal pump”)
• Overall satisfaction (“patients’ confidence in their sexual ability, sexual and overall satisfaction, and whether they regret pursuing IPP insertion”)

The team developed 35 questions that focused on patient satisfaction and expectations. Each question was scored on a 1—5 point Likert scale. Higher scores indicated more positive responses. 

Patient Cognitive Interviews

Twelve patients were interviewed by phone to provide feedback on the questionnaire. Interviews took place 6 months to 5 years following the patients’ IPP surgery. 

Based on this feedback, the survey was expanded to 37 questions. The two added questions focused on penile sensation changes and the ability to conceal the implant when the penis was flaccid.

Questionnaire Validation

Patients from 4 centers completed the survey using RedCap. At this point, the survey included demographic questions, the 37-item SSIPI, and questionnaires for convergent and discriminant validity. 

The Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS), the Self-Esteem and Relationship (SEAR) questionnaire, and the erectile function domain of the International Index of Erectile Function (IIEF) were used to determine convergent validity. 

The International Prostate Symptom Score (IPSS) was used to determine discriminant validity. 

Item Winnowing

After further review, the number of survey questions was reduced to 16 items. 

Results

Patients

Data were collected from 118 men with an average age of 67 years. Their mean time between IPP implantation and survey completion was 25 months, and 95% were still using their implant. During the 6-month period before the survey, the men reported using their implant approximately once a week, on average. 

Winnowing 

Analysis of Cronbach’s alpha showed that there were redundant questions in the survey. Questions about expectations and satisfaction were among those removed. 

The final survey included 16 items covering 4 domains: overall satisfaction, appearance, pain, and function. 

Reliability and Validity 

Further results were reported as follows:

The 16-item SSIPI showed high internal consistency with an overall Cronbach's Alpha of 0.97 (domains 0.85–0.89). Item-total correlations for individual items to subscales ranged from 0.60 to 0.91. The overall test-retest reliability was 0.94 (domains 0.87–0.93). Erectile Dysfunction Inventory of Treatment Satisfaction and Self-Esteem and Relationship had correlations of 0.84 overall (domains 0.57–0.79) and 0.47 overall (domains 0.34–0.44), respectively. International Prostate Symptom Score (discriminant validity) had correlations of -0.29 overall (domains -0.17 to -0.31).

IPP Satisfaction 

The 16-item SSIPI indicated high patient satisfaction. The following scores (based on a range of 1 to 5) were reported: 

Discussion 

Because there is no other implant satisfaction questionnaire available in English, it is difficult to compare the results of this study to others. 

The SSIPI should allow clinicians to “objectively and consistently” evaluate patients’ satisfaction with their IPPs. This information can help clinicians better understand the roles of implant function, appearance, and pain in patients’ satisfaction. This knowledge may help them counsel patients more effectively. The SSIPI may also help researchers studying IPPs in men of different ethnicities and sexual orientations. 

The study’s “rigorous psychometric process” was deemed a strength. However, limitations were identified: 

• Small numbers of sub-populations, such as gay men or men with Peyronie’s disease.
• Pre-operative erectile function was not assessed.
• The questionnaire did not include items concerning reservoirs. 
• Partner satisfaction was not assessed. 
• The IIEF has not been validated for men with IPPs.

Conclusion

“The SSIPI has demonstrated robust internal consistency, test-retest reliability, and expected convergent and discriminant validities. Patients demonstrate a high satisfaction with IPPs. Thematic analysis results in exclusion of redundant questions, rendering a final survey of 16 items.”