“Trick” or “Treat”? - magnetic (aided) removal of impaled fragments (MR(A)I)

Use of MRI with metallic objects or fragments in situ is contra-indicated due to its strong magnetic pull.¹ Magnetic fields are therefore avoided when non-palpable metallic fragments are trapped in the body.² We demonstrate that a low magnitude, magnetic field application can provide a useful adjunct in localisation and surgical removal of metallic fragments.

A 38-year-old right hand dominant metal tool-worker presented with multiple non-palpable subcutaneous metallic foreign body fragments with poorly identifiable entry points. The foreign bodies were visible on radiographic imaging but were not readily palpable as they were embedded in the subcutaneous tissues. The patient suffered discomfort around the foreign bodies especially when performing routine tasks or whilst resting the forearm on a flat surface (Figure 1). The patient ingeniously demonstrated the presence of these foreign bodies on the ulnar border of the middle and proximal third of his forearm using a small play magnet in the shape of a pin tumbler key. Whilst playing with his 4-year-old daughter, she suddenly drew his attention to her trick that involved moving the magnet up and down his forearm and she was able to persuade it to latch onto his skin in particular locations. He particularly observed that the magnet adhered to his forearm skin and dangled in partial suspension with the round top (bow) adherent to skin and the extending limb (blade) suspended in mid air (see Figure 2). The patient realised that the points of attachment of the magnet coincided with the non-palpable foreign body fragments causing him discomfort. Following his “magnetic skin sign” demonstration characterised by (i) a tactile adherence of the magnet to the skin and (ii) skin pouting pull on the metallic object creating a convincing clinical sign and (iii) ability to reproduce the test, the case for presenting this chance finding as a technical aid was compelling. The patient subsequently underwent successful removal of the foreign bodies that were embedded in the subcutaneous tissue of his forearm using the magnet intra-operatively under local anaesthetic. The magnet was wrapped in a transparent sterile cover and provided an efficient accessory tool to accurately locate the foreign object without unnecessary soft tissue dissection. The innovative use of the magnet considerably reduced operative time, minimised length of scar access and avoided prolonged use of the inflated arm tourniquet. The mini-c arm use and exposure to irradiation was therefore minimised, as 3D localisation was not essential.

Figure 1.

Radiograph illustrating metallic foreign bodies circled in red.

Figure 2.

Showing a low grade magnet with illustration of “magnetic skin sign” including (1) tactile adherence (2) skin pouting pull on metallic foreign body (3) reproducibility.

The patient had successful removal of the metallic foreign bodies and was reviewed in clinic several weeks later when he reported he was symptom free.

The clinical application of this low-grade magnet has the potential to open up its use in other areas of clinical practice as an adjunctive tool in the localisation and removal of multiple foreign bodies or loose fragments in the body especially those in the subcutaneous plain. In areas of acupuncture, magnets with Gauss of 800 are regularly used to manage children aged 1–5 years.³ Integral magnetic ports are currently used in inflatable breast implants.¹

Conflict of interest

There are no conflicts of interest relating to this short correspondence submission.