A fifty-six-year-old woman presented with progressive pain and
swelling in the dorsolateral region of the right foot. She had had
the symptoms for eight months. She could recall no history of trauma. Physical
examination showed a healthy patient with a tender mass on the dorsolateral
aspect of the right foot. The overlying skin was intact. She had
a normal white-blood-cell count, a normal C-reactive protein level,
and an erythrocyte sedimentation rate of 55 mm/hr.
A radiograph of the right foot showed an eccentric lytic lesion
of the cortex and the medullary space in the diaphysis of the fifth
metatarsal (Fig. 1).
A bone scan showed a threefold increase in uptake in the early blood-pool
phase and a fivefold increase in the late phase in this region of
the foot. Magnetic resonance images confirmed a destructive lesion
of the fifth metatarsal with a dorsomedial cortical defect (Figs. 2-A, 2-B, and 2-C.
Because of the suspicion of an osteolytic tumor, an open biopsy
was performed. The dorsomedial cortex was found to be destroyed
and replaced by granulation tissue. In the cavity, a 2-cm-long black thorn
was found and removed (Fig. 3). Before wound closure, the lesion
was curetted, irrigated, and filled with a collagen sponge containing
gentamicin sulfate. Pantoea agglomerans, an Enterobacter
species commonly found in the soil, grew on cultures of parts of
the thorn and the removed tissue. Histologically, chronic granulation tissue
was found.
A systemic antibiotic (ciprofloxacin) was administered for four
weeks. The wound healed without complications. Upon retrospective
review of the magnetic resonance imaging scans, we could identify
the thorn (Fig. 2-C).
Only thirty-one cases of thorn, wood, or plant-splinter-induced
lesions of bone have been reported in the English-language literature,
to our knowledge (Table ITable I). Because it is so exposed
to injury, the hand is the most common location for thorns or splinters,
with eight metacarpal lesions1,4-9 and
two phalangeal lesions10,11 having
been reported. The second most common location is the foot, with
five metatarsal lesions12-16 and
one cuneiform17, one
cuboid16, and one phalangeal
lesion9 having been reported.
The median time from the injury to the detection of the osseous
lesion was only four months, but the longest interval was twenty
years, and seven patients could not recall any antecedent injury.
The bone lesion that is induced by a thorn or a wood splinter usually appears
to be a consequence of infection resulting in osteolysis or periostitis.
Of the thirty-one reported cases, nineteen had osteolysis only;
five, a periosteal reaction without osteolysis; and seven, a combination
of the two (Table I).
In recent years, reports regarding the use of ultrasonography,
magnetic resonance imaging, and computed tomographic scanning to
facilitate the detection of foreign bodies have been published18-25. In general, splinters that have
been soaked for more than a few days can be visualized with either computed
tomography or magnetic resonance imaging, but the latter modality
is preferred. Splinters that have been soaked for less than three
days or those that are located near the bone are not detected reliably
with any imaging method24. In
the special situation of intraorbital wooden foreign bodies, computed
tomography has proved to be better than magnetic resonance imaging
because of its superior ability to discriminate between dry wood,
bone fragments, and air23. In
all three case reports in which magnetic resonance imaging was used22,26,27, and in the case of our patient,
the thorn or the wooden fragment was hypointense on T1-weighted images,
and a thin rim of enhanced tissue was seen after intravenous injection
of gadolinium (Fig. 2-B). In all of these cases, the most
important factor for identification of the splinter was a surrounding
rim of fluid-rich granulation tissue or a fluid-filled cyst. On
T2-weighted or opposed-phase gradient-recalled echo sequences, however,
the high signal intensity of the granulation tissue may outshine
the foreign body and make identification difficult.
In conclusion, the presence of a thorn or a wooden fragment in
or adjacent to bone may induce not only a foreign-body reaction
but also chronic osteolysis or, less commonly, a periosteal reaction of
the bone. As these lesions occur most commonly in the distal aspect
of the extremities, one should be aware of their characteristic
clinical and radiographic patterns in the differential diagnosis
of hand and foot tumors. Magnetic resonance imaging has proved to
be a sensitive diagnostic method, especially in cases where granulation
tissue surrounds the foreign body. Treatment should include operative
débridement and removal of the thorn, intraoperative culture,
and administration of organism-specific antibiotics postoperatively.