Zipper entrapment of the penis is an uncommon injury in prepubertal boys. These injuries typically involve the foreskin or redundant penile skin and may occur during the zipping or unzipping process . Localized edema, superficial tissue abrasions, bruising, and pain are the most common complications of zipper injuries; skin loss or necrosis, is unusual.
Zipper entrapment injuries occur infrequently. In one case series from a pediatric emergency department, one zipper entrapment injury occurred per 4000 new emergency department attendees . In this series of 30 boys between the ages of 2 and 12 years of age, 60 percent of the affected boys were wearing underwear at the time of the injury. Most of the injuries were self-inflicted (84 percent) and occurred as the zipper was being zipped up as opposed to down (92 percent).
In most instances, the uncircumcised foreskin is entrapped in the zipper (figure 1) . Occasionally redundant tissue on the ventral side of the circumcised penis is involved.
A zipper is composed of interlocking dentitions that are aligned by a fastener consisting of an inner faceplate, outer faceplate and median bar (picture 1) . The fastener and cloth hold the zipped dentitions together. If either the cloth or fastener is disrupted, the zipped dentitions fall apart.
The clinician should attempt removal of entrapped penile tissue as soon as possible after the zipper injury. With time, swelling and edema of the entrapped tissue makes successful management more difficult. Penile entrapment that involves the urethra or falls attempts using the procedures described below warrants prompt referral to or consultation with an urologist.