Tolerability and Efficacy of Newly Developed Penile Injection of Cross-linked Dextran and Polymethylmethacrylate Mixture on Penile Enhancement

6 Months Follow-Up

D Y Yang; W K Lee; S C Kim

Disclosures

Int J Impot Res. 2013;25(3):99-103. 

In This Article

Materials and Methods

Subjects

Adult male subjects aged 20–70 (mean age; 44.4 years), who wanted penile enhancement, were recruited in this study. Before procedure, all subjects were evaluated on history and physical examination, especially on anatomical features of the genitalia and on psychological details. The subjects signed an informed consent form, after the study design and possible complications of the penile injection were explained. Men with the following conditions were excluded from the study: psychological/psychiatric history, including major depression; congenital or acquired malformation of the penis; previous penile plastic surgery; phimosis; and any chronic major systemic disease, such as cancer or diabetes.

Finally, 20 subjects were recruited to this study in two medical institutions, each of them having 10 subjects. Approvals for the study were obtained from the respective Institutional Review Boards of the two institutions (No. 09-113).

Injection Material

The filler (Lipen-10) is newly developed dermal filler for soft-tissue augmentation, and is a commercially available product approved by the Korean Food and Drug Administration in 2010.

Lipen-10 consisted of cross-linked dextran in 75% and PMMA in 15%. Cross-linked dextran and PMMA are microspheres with diameters of 45–120 μm and 32–120 μm, respectively. These microspheres (90% by volume) are suspended in hypromellose solution (10% by volume), therefore, there is no physical or chemical interaction between them. Once injected, the smooth, electrically uncharged PMMA microspheres become encapsulated by endogenously derived connective tissue, which prevents migration of the microspheres. The PMMA microspheres resist phagocytosis and are not degraded by enzymatic digestion.[6] Cross-linked dextran, another component of the mixture, is derived from dextran used as volume expander. The positive surface charges of dextran apparently attract macrophages. In turn, the macrophages release TGF-β and interleukins, which stimulate fibroblasts to produce collagen fibers. After extensive resorption, dextran is replaced by the body's own tissue.[7]

Injection Method

A single surgeon performed the procedure at each institute. The procedures were carried out in an office setting with the patient in the supine position. The penile skin was cleansed with povidone-iodine topical antiseptics, and a penile block was induced by injecting 2 ml 0.2% lidocaine into the penis root.

After the anesthesia had taken effect, the filler was injected into the subcutaneous tissue of the penile shaft, between dartos fascia and Buck's fascia by the fanning technique using a syringe with 20-gauge needle. The needle was directed posteriorly and laterally, parallel or tangential to the corpus cavernosum, distributing the material as uniformly as possible from the penile root to the distal shaft, by a continuous back and forth movement, while constantly pressing the syringe plunger. Injected material did not cover ventral part of the penis, to avoid urethral injury or compression. During the procedure, the penis was maintained in the stretched state. Mean injected volume was 23.73 ml (range 17–30 ml), and 4–6 needle punctures were performed during the procedure. The injected surface was thoroughly massaged in order to redistribute the filler as uniformly as possible, without leaving palpable nodules.

After injection, an elastic penile support bandage was applied, to support uniform fixation of the injected material and to avoid penile edema. The patients were instructed to construct bandage by himself not to compress too tightly, to avoid squeezing the injected material out of the injected place or voiding difficulty.

Evaluation

Before injection of the filler, penile girth and length were measured for all subjects. With the penis in the flaccid state, the penile girth was measured without tension, with a caliper at the base, mid-shaft and distal shaft. The penile length was measured from the pubic-penile skin junction to the coronal sulcus of the penis, and did not include the penile glans, while penis was perpendicular to the body without stretching. The prepubic fat pad was pushed to the bone at the maximum. All measurements were performed in supine position at stable environment. These measurements were repeated at 1, 3 and 6 months after penile injection.

The primary end-point of this study was increase in penile girth by 2 cm or more in the flaccid state at 6 months post-treatment. Another end point was increase in flaccid penile length by 1 cm or more. Mathematically, if we consider that the penis as a cylinder and that injected materials are not absorbed or migrated, the increase in girth is 1.97 cm after injection of 18 ml of filling materials. The lengthening effect of penile injection is difficult to calculate mathematically, owing to physiologic contraction and relaxation of penis. Therefore, on the basis of previous results from methods using the same principle, such as autologous fat transplantation, the cutoff point for increase of penile length was decided.[2]

Changes in the penile girth and length were analyzed at 1, 3 and 6 months post-treatment. The adverse events, defined as an undesirable medical condition that was not observed before penile injection, were evaluated. Differences in the results between institutes were also analyzed for all parameters.

Statistics

The changes in the penile girth and length were analyzed at 1, 3 and 6 months post-treatment, using the Student's t-test and paired t-test. Adverse events were analyzed with McNemar test. Statistical Package for the Social Science version 19.0 (SPSS, Chicago, IL, USA) was used for all statistical assessments. The P-values for changes of penile girth and length before and 6 months after penile injection were one-sided, whereas the other P-values were two-sided. A P<0.005 was considered as statistically significant for all analyses.

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