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Small magnets can exert strong forces.
A boy of 11 arrived in accident and emergency with the proximal end of his penis firmly clamped between two 20 mm diameter disc magnets. He had been referred from his local district general hospital after attempts to remove the magnets had been unsuccessful. A penile block was performed but the magnets proved impossible to remove either by hand or with surgical clamps. There was difficulty in getting a purchase on the discs and the strong magnetic field hindered precise manoeuvring of the instruments. Even the assistance of the local fire brigade and the distracting force of two large steel mallets failed. We were surprised that such a small pair of magnets (Figure 1) could exert so strong an attractive force; however, as discs with a thin layer of tissue between, their poles were in extremely close proximity.
There are three methods commonly described to demagnetize ferrite materials—namely, application of a stronger magnetic field of opposite polarity, of a magnitude dependent on the coercivity of the material; heating of the magnet to a temperature above the Curie or Neel point; or repeated heavy hammering. We employed a more delicate technique by shearing the magnets away from each other, moving them perpendicular to the force of attraction. This was surprisingly easy and the patient was left with bruising only, no skin injury. There was no evidence of pressure necrosis or injury to the corpora or urethra, and he made a complete recovery.
Paediatric misadventures with magnetic objects are well described. Ingestion can result in obstruction, perforation, adhesion and fistulation,1 especially when multiple objects interact across loops of bowel.2 Application of magnets across body parts such as the ears, nose, or penis, in an attempt to emulate adult body piercings, can result in tissue necrosis.3,4 The strength of a magnet depends on its chemical composition, and neodymium iron boron5 composites exert forces many times those of pure ferrite materials. These 'rare earth' magnets are brittle and can be recognized by their tenacious anticorrosive coating.