PENILE LENGTH IS PRESERVED AFTER IMPLANT SURGERY

Abstract

Introduction

A common cause of patient dissatisfaction after penile implant (PI) is caused by patients’ perception that surgery has shortened the penis.

It has been suggested that stretched penile length preoperatively is almost the same after surgery when the prosthesis is in erect status. However, no comprehensive data supports this theory. This prospective study aimed to investigate penile size measured preoperatively and erect postoperatively.

Methods

Standardised measurements of stretched penile length and girth were performed in theatre before penile prosthesis implantation then re-measured at the end of the procedure with the penis in the erect position. We recorded type of penile implant, cylinder lengths and malleable rod diameters. All patients had data on body mass index (BMI), hypertension (HTN), glycated haemoglobin (HbA1c) and Peyronie’s disease (PD).

Results

133 patients were assessed. 88 (66.2%) had malleable prosthesis (MPP), 45(33.8%) inflatable prostheses (IPP). Median age and BMI were 56 and 30 respectively. 40(30.1%) patients had hypertension and 37(27.8%) suffered from PD. 89 men (66.9%) were diabetic.

The mean pre-implant stretched length was 12.8cm (±1.8). Mean flaccid girth was 10.3cm (±1.2). Postoperatively mean erect length and girth were 13.1cm (±1.7) and 11.3cm (±1.3) respectively. Overall, there was a significant (p<<0.05) increase in both length +0.36 cm (±0.63) and girth +1.04 cm (±1.02). Patients who had IPP, had a more significant increase in both length (0.62cm ±0.72) and girth (1.7cm ±1.0) compared to MPP (0.22cm ±0.53) and (0.7cm ±0.87) (p<<0.05). We investigated correlations between pre and post-op outcomes related to BMI, HTN, Diabetes and PD. None of these variables affected outcome.

Conclusions

Penile implant surgery does not significantly decrease penile size compared to pre-operative assessment. The outcome was not affected by co-morbidities. The preoperative length and girth correlated well with the immediate postoperative erect penis, although girth was not necessarily comparable in this series of patients measured under anaesthesia. Recording penile dimensions in the clinic and agreeing these with patients pre-operatively may be a way of improving satisfaction levels with this surgery.

Introduction

Penile implants were first introduced in 1936 by the Russian surgeon Nikolaj A. Bogoraz¹ and have undergone many technical improvements since then. Modern penile implants are now the standard of care, especially for those patients refractory to medical management. In 2016 Welliver et al. analysed data provided by two of the main penile implant companies (AMS and Coloplast) showing that over 62,000 implants were used world-wide during the period 2005–2010². Device failure is rare, with low infection rates and a high overall patient satisfaction rate with figures ranging from 76–90%³. However subjective loss of penile length or volume remains a significant patient concern. 5–30%³ may complain of penile shrinkage following PI insertion. Deveci et al. found that there were no statistically significant differences in penile size after surgery compared to preoperative measurements even though 72% of the patients reported a decrease in penile length⁴. In contrast, Wang et al. reported decrease in the erect penile length of about 0.75cm⁵. Levine et al found that some patients complain of shortening after penile prosthesis implantation but may be comparing their current size with their memory of a fully functional erection. Unrealistic expectations and body changes such as weight gain and excess pubis fat may contribute. They recommended physicians to discuss these issues with the patient and take a preoperative stretched flaccid penis length measurement for postoperative comparison⁶. Thus, we conducted this prospective, multicentre observational study to investigate the correlation between preoperative and postoperative penile size. Our hypothesis was that penile prosthesis implantation should not shorten the penis.

Patients and Methods

Study Population:

The study population included patients undergoing primary inflatable or malleable penile implant surgery in 2 high volume centres. Exclusion criteria included: re-implant surgery and patients who had complex procedures such as grafting for Peyronie’s.

The type of penile implant, brand, cylinder length and the rod diameter were recorded, as well as comorbidities such as BMI, vascular risk factor profile, and HbA1c level.

Preoperative Counselling:

The preoperative discussion was focused on the goal of surgery of obtaining a ‘functional erection’, an erection permitting sexual intercourse. Choosing MPP versus IPP was based on patient’s preference including factors such as concerns regarding concealment, ease of use but often relied heavily on cost, as PI surgery is not covered by insurance in our geographic location. The consent form signed by all patients included all the potential complications and stated that penile implant surgery is for restoration of functional erection for penetrative sexual activity and not for other purposes like penile size enhancement. The study was approved by our institution ethical committee, and consent to measurement under anaesthesia was obtained by patients.

Penile Size Measurement:

Penile girth and stretched flaccid length were assessed by the operating surgeon using a standardised method. The first measurement was performed under spinal or general anaesthesia prior to surgery. Using a rigid plastic ruler, bone-to-tip measurement was conducted as follows: with the penis fully stretched, the base of the ruler was placed on the pubic bone and the tip of the ruler was placed at the level of the tip of the glans. Penile circumference was measured with a tape at the base of the penile shaft. After wound closure we repeated the same procedure. In those who had an IPP, the measurement was performed after full inflation of the device.

Surgical Technique:

All operations were carried out in standard fashion. Malleable implants were inserted via ventral midline incisions whereas inflatable implants were placed via peno-scrotal incisions.

Statistics:

Assuming an average penis length 13.2cm (from a recent 15 521 patient systematic review⁷,) we felt a penile length loss of 1.5cm (Δ11%) would be significant and relevant to most patients. Aiming for 80% Power and 95% Confidence Interval, by using the following formula n = (Z_α/2+Z_β)² *2*σ² / d, we calculated that the sample size needed was 130 patients.

Pre-operative and post-operative length and girth were compared using paired t-tests. The differential penis sizes of the different implants (inflatable vs malleable prosthesis) were compared by using one-way ANOVA. All data were presented as: mean± standard deviation (SD) with p≤0.05 considered as statistically significant.

Results

Patient Population:

133 patients were measured. 88 (66.2%) had a malleable prosthesis while 45 (33.8%) had an inflatable device. Among the inflatables, 11 (8.2%) were AMS and 34 (25.6%) Coloplast. Of the malleables 83 (62.4%) were Coloplast Genesis, the remaining 5 (3.8%) Silimed. (Figure 1). Median age and BMI were 56 and 30 respectively. 40 (30.1%) patients were hypertensive and 37 (27.8%) suffered from Peyronie’s disease. The majority of the patients,89 (66.9%) were diabetic.

Figure 1.

Illustrates the proportion, type and brand of the prosthesis implanted on our patients.

Penile Length Measurements:

The average pre-implant stretched length measured was (12.8±1.85cm) while after the operation it was (13.1±1.76 cm). The average pre-operative girth was (10.3±1.21) whereas the post-operative was (11.3±1.28) as shown in (Table 1).

Table 1:

The table below shows the average penile length and girth before and after the surgical implantation

	Before Surgery	(SD)	After Surgery	(SD)	Mean Difference	(SD)
Average length (cm)	12.8	1.85	13.1	1.76	+ 0.36	0.63
Measured girth (cm)	10.3	1.21	11.3	1.28	+ 1.04	1.02

After surgery, 98 patients (73.7%) had some objective increase in either length or girth. 56 (42.1%) had an increase in length, 48 patients (36.1%) increased both length and girth. Only four men (3.0%) had an objective decrease in both length and girth. Looking at length change by stratifying for type of prosthesis implanted, 26 (57.8%) and 30 patients (34.1%) had an increase in the IPP and MPP groups respectively compared to stretched length. 42.2% of the inflatables and 55.7% of the malleable implants resulted in no change. Only 9 patients (7%)) had a decrease in length, all among the MPP group. (Table 2).

TABLE 2:

The table below shows the post-operative dimensional changes, stratified by prosthesis type IPP (Inflatable) MMP (Malleable) and subdivided per cluster of change (increased, unchanged, reduced).

Δ Length		Increased n. (%)	Unchanged n. (%)	Reduced n. (%)
Total Prosthesis	133	56 (42.1%)	68 (51.1%)	9 (6.8%)
IPP	45	26 (57.8%)	19 (42.2%)	0 (0.0%)
MMP	88	30 (34.1%)	49 (55.7%)	9 (10.2%)
Δ Girth		Increased n. (%)	Unchanged n. (%)	Reduced n. (%)
Total Prosthesis	133	90 (67.7%)	37 (27.8%)	6 (4.5%)
IPP	45	40 (88.9%)	5 (11.1%)	0 (0.0%)
MMP	88	50 (56.8%)	32 (36.4%)	6 (6.8%)

Turning to girth change, over 80% of the patients who received an inflatable device witnessed an increase. Over 55% of the MMP patients saw an increase in girth (Table 2).

Statistical Analysis

Using a Paired T-test, we compared post to pre-surgical stretched length and girth. The test performed showed a statistically significant increment in both length (+0.36cm ±0.63) and girth (+1.04cm ±1.02) with a p-value <<0.05. (Table 3)

Table 3:

The table shows the results of the T-test performed to identify differences in penile length and girth after the surgical implant.

Paired T-test	Paired Differences
	Mean	Std. Deviation	95% Confidence Interval of the Difference		Sig. (2-tailed)
			Lower	Upper
Length Post vs Pre-surgery (cm)	0.3571	0.6294	0.2492	0.4651	<<0.05
Girth Post vs Pre-surgery (cm)	1.0414	1.0188	0.8666	1.2161	<<0.05

We also stratified patients by type of device implanted (Inflatable vs Malleable) by using an ANOVA Test. The differential lengths and girths (length/girth post-surgery vs length/girth pre-surgery) of the two groups were compared. (Table 4).

Table 4:

The table shows the results of the ANOVA test performed to show the difference in length and girth stratified by type of prosthesis implanted.

Anova Test Post vs Pre-surgery	N	Mean	Std. Deviation	95% Confidence Interval of the Difference		Sig.
				Lower	Upper
Δ Length (cm)
IPP	45	+ 0.622	0.724	0.405	0.840	<<0.05
MMP	88	+ 0.222	0.530	0.109	0.334
Total	133	+ 0.357	0.629	0.249	0.465
Δ Girth (cm)
IPP	45	+ 1.667	1	1.366	1.967	<<0.05
MMP	88	+ 0.722	0.874	0.536	0.907
Total	133	+ 1.041	1.019	0.867	1.216

Patients who had inflatable devices had a statistically significant greater increase in length (+0.62cm± 0.72) and in girth (+1.67cm±1.0) compared to those who had malleable implants (+0.22cm ±0.53) and (+0.72cm ±0.87) with a p-value <<0.05.

Comorbidities and Size

Univariate analysis was carried out for comorbidities such as Obesity, Hypertension, Diabetes and Peyronie’s disease: none were of any significance.

Discussion

Penile implants have been developed over the past 40 years resulting in a more and more effective and reliable treatment for advanced erectile dysfunction⁶. Early implants had failure rates ranging from 21–45% in the first few years after surgery ^8–10 whereas modern devices show mechanical survival ranging from 75–94% depending on the year of implantation and model¹⁰. Overall satisfaction rates have also seen a steady increase over the years, from 76% in 1994 ³ to well over 90% in more recent studies ^{11, 12}.

Scant literature exists on penile length loss after penile implant surgery, despite its relevant role in patient’s quality of life. Most authors do not focus on this issue and when they do, the problem is described together with other causes of dissatisfaction. Montorsi et al. reported their results in 200 patients had AMS three pieces inflatable implants in 5 centres, with a mean follow-up of 59 months (range 6–130) and they were extensively questioned about function of the device and its impact on their sexual life. A high percentage of patients were satisfied. Reasons for patients’ complaints included postoperative penile shortening in 60 (30%) cases and poor glandular engorgement in 40 (20%) cases. They concluded that IPP provide an overall patient and partner satisfaction rate of 92 and 96%, respectively. However, postoperative penile shortening and poor glandular engorgement were the causes of some complaints among the patient population as well as the unnaturalness of prosthetic erection among female partners¹¹. On the other hand, Bettocchi et al reported their results with AMS CX 700 prostheses implant in a single centre, by the same surgeon, in the period of 5 years. All the patients included in the study were contacted by phone by a single operator who asked for their consent to collect information regarding their operation, the use of the prostheses, and the couple satisfaction. They used a nine-point questionnaire. They mentioned that 8% of the patients were dissatisfied; among the reasons included insufficient rigidity and penile length for normal intercourse¹³. In a recent retrospective multicentric study, Gentile et al. reported their results in an analysis concerns a group of 42 patients undergone 2-pieces IPP implantation from November 2005 to November 2013, in four Centres of proven experience. Every patient was asked to fill the Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) specifically modified, in order to assess their own satisfaction after surgery and, its impact on their quality of sexual life. 42 patients were evaluated (AMS-Ambicor: 28; Coloplast-Excell: 14). The mean age at the time of operation was 60,7 years, the mean follow up 27,6 months. 5% of patients reported of being dissatisfied with length or girth postoperatively ¹⁴.

Despite being a recognised problem, there are only two papers concentrating on penile length after implant surgery. Deveci et al. ⁴ published in 2006 a paper in which they analysed length alterations after surgery. 56 patients received either three-piece (Coloplast Alpha-1) or two-piece Inflatable (AMS Ambicor) prosthesis. Stretched flaccid penile measurements were performed immediately before the surgery under anaesthesia and then at 1 and 6 months after the implant operation. Their results showed no difference in length before and after surgery. Despite the absence of statistically significant length changes, 71% of patients had subjective penile length shortening although only 43% had an objective reduction.

In the second study, Wang et al. only 11 patients, who had inflatable penile implant surgery (AMS-700CX, Coloplast Titan), were assessed ⁵. Before surgery, erect penile length was measured after the induction of a full erection by using Intracavernosal injections. At 6 weeks, 6 months and 1-year postoperatively, erect penis lengths were measured from the pubic bone to the tip of the penis glans after full inflation of the IPP in outpatient clinic. A decrease of 0.83±0.25cm, 0.75 ±0.20cm and 0.74±0.15cm in erect penile length was respectively reported at the three time points.

The main drawbacks of the above-mentioned study rely on the fact that preoperative measurements were performed only in patients who had full erection after intracavernosal injection with Trimix, and then compared to the postoperative size after penile implantation. Our data and that of Deveci et al. ⁴ used stretched flaccid length. That may explain why Wang et al. found a reduction in size while we did not. However, the majority of our patients were unable to get a full erection even using high doses of Quadrimix, so we could not have carried out the test in such a way.

In our study, the aim was to find a valid(reference) for penile size before surgery to compare postoperatively when counselling the patient about the expected outcome. We used the immediate preoperative stretched flaccid penile size, as the patient in that case suffering ED ( non-functioning) as a valid reference to compare with the immediate postoperative functional penis, which is more logic and practical.

We think that counselling patients before penile implant surgery should focus on the patient status (including stretched penile size) before surgery as they usually suffering sever erectile dysfunction, making this as a reference when comparing outcome postoperatively. Patients should also informed that its unlikely, after having an implant, to retain their original glans engorgement which adds usually few millimetres and more pleasure during intercourse. Good counselling before surgery is critical for improved patient satisfaction, and the best candidate for PI surgery is a patient failed non-surgical treatments and still motivated to have surgery to improve his sexuality¹⁵

In our study, patients having IPP had a statistically significantly longer (+0.62cm ± 0.72) and thicker penis (+1.67cm ±1.0) compared to those who had malleable implants (+0.22cm ±0.53) and (+0.72cm ±0.87) respectively. However, the groups compared are unbalanced; 33.8% vs 66.2% respectively and not randomised therefore, we do not know how the numerosity and heterogeneity of the sample might have impacted on our results. It is also impossible to compare girth in men with severe ED to what the “normal” would have been for the man before his ED struck. While we measured girth, this may have limited reproducibility and relevance to the post-operative state after healing.

Measuring immediately after surgery should have meant minimal or no oedema, but there might be minor swelling due to tissue trauma occurring during surgery as well as due to instillation of irrigation fluid which might cause extra-tunical engorgement of the penis, which might be a potential limitation of our study.On the other hand,It is hard to imagine a process by which malleable prosthetic penis could be smaller weeks after the operation, although poor inflation of inflatables could cause this. What data do exist on inflatables suggested the reverse and that an inflatable prosthesis often has tissue expander properties in the longer term.

Of course, if a surgeon is happy with penis size but the patient is not the operation is hardly an unqualified success. While our data confirms that PI insertion does not cause penile shrinking, it may be that men’s perception of “normal” is skewed either to begin with or after years of erectile dysfunction. We know that a perception of the surgery as an agent of penile shrinking occurs in Peyronie’s disease, and that many men perceive their penis to be shorter than reality. A much more complex study would be needed to address these points. Clearly the perfect study would involve measuring men in full erection before they had ED, but this would be virtually impossible as it would mean predicting men who would need penile implants years in the future.

An assessment of how men perceive penile size and function prior to surgery and afterwards would be very useful and would address many of the simplistic issues raised by our study and others to date. However, the nomogram developed by the King’s College group has not been validated in men with severe ED so the correct instrument to assess these men may not exist.

Finally, the stretch may falsely elongate the penis as compared to the erect penis, and we also did not perform an intra-observer error measurement, which could be considered as potential flaw.

Conclusion

Penile implant surgery does not decrease penile size compared to pre-operative stretched measure but preserves increases it for the great majority of patients. Men having an inflatable prosthesis are likely to witness a more significant length increase than those who with a malleable implant. The outcome was not affected by co-morbidities such as diabetes, hypertension or Peyronie’s.

Preoperative length and girth correlate well with the immediate postoperative erect penis. Recording penile dimensions in the clinic and agreeing these with patients pre-operatively may be a way of improving satisfaction levels with penile size postoperatively.

It is interesting to wonder if some men who are concerned about penile size preoperatively would be better managed by either psychosexual counselling, and if the inflatable implant may give greater satisfaction.

In any event, patients can be reassured that no immediate direct size loss is expected in the great majority of cases.