Keywords
carpal bones - osteoblastoma - bone neoplasms - hand
Introduction
Carpal bone tumors are suspected in clinical presentations of chronic wrist pain with
no history of previous trauma. Injuries with osteolytic features are often intraosseous
ganglia, enchondroma, osteoid osteoma, and, less commonly, osteoblastoma.
Osteoblastomas are benign neoplasms that form bone cells. They represent 1% of tumors,
and their most common locations are the posterior elements of the spine, pelvis, and
long bones. The carpal bones are rarely affected, and involvement of the capitate
bone is even less common.[1]
[2]
[3] The present study describes a case of osteoblastoma of the capitate bone and reviews
the current literature on the subject.
Case Report
A 40-year-old, female, right-handed patient with a history of progressive pain on
the dorsal face of the right hand for 2 years. The patient denied previous traumas,
infections or other symptoms associated with the condition.
The patient presented a swelling at the affected area and functional impairment to
perform basic activities of daily living.
An examination revealed a slight reduction in flexion in the right wrist, decreased
grip strength, and pain on palpation of the capitate bone. The ectoscopy showed no
changes.
Initial radiographs showed a well-defined osteolytic lesion with a sclerotic margin
and a lobulated aspect at the capitate bone ([Fig. 1]).
Fig. 1 Initial radiograph of the right wrist, revealing a well-defined osteolytic lesion
at the capitate bone.
There were no calcifications or extensions to soft parts or other bones. Due to the
non-specific aspect on radiography, a computed tomography was requested, revealing
a lesion with a central hypodense component and well-defined hyperdense margins restricted
to the distal portion of the capitate bone ([Fig. 2]).
Fig. 2 Computed tomography of the right hand. Coronal (A) and axial (B) sections. There is a well-defined hypodense lesion at the right capitate bone, with
hyperdense margins, and no involvement of other hand bones.
Surgical treatment with intralesional resection and an ipsilateral olecranon bone
graft was indicated because of the significant pain and functional impairment. The
resected specimen was sent for an anatomopathological study ([Fig. 3]).
Fig. 3 Perioperative period. (A) Perioperative aspect of the lesion at the right capitate bone. (B) Bone cavity after lesion curettage. (C) Resected specimen sent for an anatomopathological examination. (D) Bone-graft donor area at the right olecranon. (E) Bone defect filled with an olecranon graft.
The histopathological analysis of the bone-tissue fragments revealed a benign lesion
consisting of young and mature bone tissue, with no atypia, permeated by fibrous tissue,
diagnosed as an osteoblastoma ([Fig. 4]).
Fig. 4 Histopathological aspect of the resected specimen, revealing young bone tissue and
some trabeculae of mature bone tissue, with no atypia, permeated by fibrous tissue.
One week after the procedure, the patient presented a significant improvement in pain,
which was sustained at subsequent evaluations at 3, 6 and 12 weeks after the procedure
([Fig. 5]).
Fig. 5 Radiographs of the right wrist eight weeks after surgery. Good integration of the
bone graft into the right capitate bone, with no signs of lesion recurrence. Posteroanterior
view with clenched fist (A), posteroanterior view (B), and lateral view (C) of the right wrist.
The patient showed good functional recovery according to the Disability of the Arm
Shoulder and Hand (DASH) questionnaire, and gradually resumed her activities.
Discussion
Reports of carpal bone osteoblastoma are infrequent, and the involvement of the capitate
bone is even rarer. Kaptan and Atmaka[2] and Afshar[3] reported this tumor location in their respective studies, while Murray et al.,[4] in their series with 26,800 primary bone tumors, cite a single case of osteoblastoma
of the capitate bone.
Osteoblastomas are benign neoplasms arising from bone tissue. Microscopically, they
are characterized by trabecular bone and fibrovascular stroma with the production
of primitive osteoid tissue.[1]
[5]
These tumors affect mainly patients in their second and third decades of life, preferably
males, in a 2-3:1 ratio.[1]
[2]
[3] Our patient, a 40-year-old woman, was did not fit the most common epidemiological
profile.
Although they can affect any bone, 40% to 50% of the lesions are at the spine, preferably
its posterior elements.[1] They rarely affect hand bones.[2]
[3] As such, the diagnosis of osteoblastoma is often not considered in cases of primary
carpal bone tumors.
Radiographically, osteoblastoma presents as a centralized, mineralized nidus with
a surrounding radiolucent halo and reactive sclerosis, or as a well-defined, mixed
(both lytic and blastic) mass with sclerotic margins.[1]
[5] Computed tomography and magnetic resonance imaging reveal a heterogeneous, circumscribed
mass, with cystic components, edema, and reactive bone.[5] Progressive, constant pain unresponsive to salicylates is the most common symptom,[6] as in our case.
Osteolytic lesions are not a frequent cause of chronic wrist pain,[6] but they must be considered, especially when there is no history of local trauma.
Some examples are intraosseous ganglion, osteoid osteoma, enchondroma and osteoblastoma.[6]
[7] Knowledge of the clinical characteristics of each of these lesions is essential
to differentiate them.
The differentiation of osteoblastomas and osteoid osteomas is a frequent challenge.
Osteoid osteomas are more frequent in the hand.[8] It typically presents as a lesion < 1.5 cm, with a central nidus surrounded by a
sclerotic zone. The pain is severe, worse at night, and relieved by salicylates.[5]
Microscopically, both lesions are very similar; bone trabeculae lined by a single
layer of osteoblasts, a tapered circumscription, and a loose arrangement of tissue
are the characteristics that favor the diagnosis of osteoblastoma.[1]
In bone tumors of the hand, enchondromas are an important differential diagnosis,
since they are the most common primary bone tumor of the hand.[6]
[8] Their classic radiographic appearance is that of a a well-defined osteolytic lesion
with dotted calcifications.[6]
Another differential diagnosis, the intraosseous ganglion is an asymptomatic, benign
cystic lesion, and an incidental finding on imaging studies in approximately 80% of
the cases.[9]
Radiographically, it presents as a cystic, unilocular, non-expansive, well-defined
lesion with sclerotic borders. Magnetic resonance imaging shows a hyposignal lesion
in T1-weighted images with hypersignal in fat-suppressed sequences. Microscopically,
it is characterized by mucoid tissue, myxomatous degeneration of connective tissue,
and fibrous walls.[7]
The treatment of osteoblastomas is still a matter of debate. Studies suggest that
the tumor may undergo malignant transformation,[7] and recurrence rates between 10% and 20% are reported.[3]
[5] Therefore, some authors indicate a range of procedures, from complete lesion resection
to curettage with or without bone grafting.[3]
[10] Castelló et al.[10] described good outcomes after curettage and defect filling with a bone graft.
In the case herein reported, the clinical presentation and radiographic appearance
initially did not enable a specific diagnosis of an osteolytic lesion. However, due
to the non-aggressive behavior of the lesion, its benign characteristics, and the
lack of extension to soft parts or other bones on imaging tests, we decided for curettage
and defect filling with a bone graft. The resected specimen was sent for an anatomopathological
examination, which later suggested the diagnosis of an osteoblastoma.
We presented a rare case of osteoblastoma of the capitate bone as a cause of chronic
wrist pain, in addition to a review on the subject. Thus, osteoblastomas can be considered
a diagnosis of exclusion for an osteolytic lesion at the level of the carpal bone.
