Yap's study concluded that the prevalence of penile implants in prison was a cause for concern. "As most of these penile implants are inserted in prison,
these men are at risk of blood borne viruses and wound infection. Harm reduction and infection control strategies need to be developed to address this
The study did not ask the prisoners why they would choose to participate in this painful and potentially dangerous practice, but it cited previous
literature on the topic which suggests that these types of penile implants are intended to make the bearer more memorable to their sexual partner, to
pledge allegiance to a gang or--more disturbingly--to inflict pain during sex. Some of the objects that have been inserted under the penile skin include
beads made from melted toothpaste caps, buttons, dice, and deodorant roller balls. And the implants themselves have a variety of names, such as pearls,
Yakuza beads, penile inserts, penile marbles, and speed bumps.
Like most exotic sexual practices, penile implants date back to the Kama Sutra of Vatsyayana. According to the Journal of Sexual Medicine, the first written evidence
that stimulating objects were inserted by "perforating" the penis or the glans, was found in the ancient sex manual. In Thailand, a bronze dog statue with
a penile bearing could be proof that the procedure existed in the fourth century. In modern times, a study from Genitourinary Medicine
suggests that penile implants were reintroduced into Thailand after World War II. The implants were sometimes called tancho nodules. Tancho was a hair
pomade, and glass from the container was either polished or melted to produce a sphere appropriate for insertion. The Journal of Sexual Medicine
documents that Asian penile nodules were also made from bullets, pearls, gems, ivory, jade and precious metals. Throughout the '70s, Asians also fashioned
penile beads from glass found on World War II planes. In one particularly ambitious case, a 28-year-old man in India placed a sealed penicillin vial, with
iodine tincture in it, under his foreskin, to gain pleasure during masturbation. Unfortunately the vial, which was 5.5 cm long and 8 cm in circumference,
could not be removed without surgery. Authors of the case study, which was published in 1992, found that the patient had no psychiatric abnormalities.
Piercing studios in the West also carry out these types of implants, referring to the practice as genital beading or speed bumps. And urologists perform penile implants, which are a different thing altogether, for erectile dysfunction rather than for appearance. However, unlike the conditions in prison, these aforementioned procedures
are sterile and surgical equipment is used.
Although the Plos One study did not find out why
this particular population of men had made these insertions, the survey revealed that those who performed the procedure were likely to be younger than 35,
of Asian origin and to have been imprisoned more than once.