Stocking-glove sign | Radiology Signs

Answer:

The stocking-glove sign is diffusely increased tracer activity throughout the hand or foot distal to the injection site, distributed in the pattern of a glove or a stocking, on a technetium-99m diphosphonate bone scan. It is an artefact of inadvertent intra-arterial injection: tracer delivered directly into an artery, most often the radial or ulnar artery during an attempted antecubital or wrist venous injection, floods the distal arterial territory in high concentration on first pass and is retained by the soft tissues and bone of that limb segment. Recognising it prevents misinterpretation as complex regional pain syndrome, cellulitis, osteomyelitis or arthritis, all of which increase uptake in a limb but do so with a different distribution and with matching findings on the flow and blood pool phases and on radiographs. The clues to the artefact are that the increased uptake stops abruptly at a level corresponding to an arterial territory, that it is present from the earliest phase, that the contralateral limb is normal, and that the injection was known to be difficult or painful. The finding is benign and requires no action other than documentation, though a repeat study on another day may be needed if quantification is important. Other injection-related artefacts to recognise are dose extravasation at the injection site with drainage to regional lymph nodes, which can mimic nodal metastasis.

Why is it called so?

The uptake covers the hand or the foot like a glove or a stocking, ending sharply at the wrist or ankle.

Pathophysiology

After a normal intravenous injection the tracer mixes in the systemic circulation before reaching any capillary bed, so distribution is uniform. When the injection enters an artery, the entire bolus passes on first circulation through the capillary bed supplied by that vessel at very high concentration. Diphosphonates bind avidly to hydroxyapatite and, in high local concentration, also to soft tissue, so the distal limb retains a disproportionate amount of activity that persists into the delayed phase. The sharply defined proximal border of the abnormality corresponds to the boundary of the arterial territory injected, which is the anatomical clue that distinguishes it from a disease process, since inflammatory and neuropathic causes follow anatomical structures rather than arterial supply.

Alternative names: Glove phenomenon; intra-arterial injection artefact

Other associated named signs: Six-point star sign of septal penetration and the hot spot at the injection site of dose extravasation

References

1. García Garzón JR, Minoves Font M, Bassa Massana P, Soler Peter M. [Artifactual image by intra-arterial injection of 99mTC-MDP simulating an osteoarticular condition]. Rev Esp Med Nucl. 2003;22(5):340. PMID: 14534010.