Intramedullary osteosclerosis: An incidental sclerotic lesion in a trauma patient.

Intramedullary osteosclerosis, a rare entity, is usually diagnosed after the exclusion of more sinister etiologies. It typically affects the lower extremity and is more common in females. While the lesion may be discovered incidentally during imaging, presenting symptoms may include pain in the affected bone that is exacerbated with physical activity. Laboratory values are normal, and the lesion is not associated with familial skeletal dysplasias. Common imaging findings include a mono-ostotic or polyostotic sclerotic lesion that lacks a periosteal reaction, soft-tissue component, and nidus. We present a case of intramedullary osteosclerosis that was incidentally discovered in a trauma patient.

Case report

A 22-year-old female patient presented to the Emergency Department following a motor vehicle crash in which she was a restrained driver. Her vital signs were normal, and she remained hemodynamically stable during her assessment in the Emergency Department. No laboratory abnormalities were reported. She reported no past medical history and denied knowledge of any familial diseases. On review of systems, she described mild, intermittent pain in her left hip during periods of extended activity. The patient’s chief presenting complaints consisted of pain in the right shoulder and the right side of the pelvis.

Physical examination revealed tenderness in the right shoulder and hip, but was otherwise normal. Radiographs of the chest, right arm/shoulder, and pelvis (Fig. 1) were also obtained. The patient underwent contrast-enhanced CT examinations of the chest, abdomen, and pelvis (Fig. 2). No acute abnormalities were identified on any imaging examinations. However, a solitary sclerotic lesion was identified in the left femur involving the head, neck, and proximal shaft. The sclerosis involved the medullary space and did not result in any cortical sclerosis or thickening. No periosteal reaction or soft-tissue abnormality was identified.

Figure 1

22-year-old woman with intramedullary osteosclerosis. Supine pelvic radiograph shows a sclerotic lesion in the left femoral head and neck (arrows). There is artifact from the underlying trauma board.

Figure 2

22-year-old woman with intramedullary osteosclerosis. Axial CT of the pelvis demonstrates the sclerotic lesion (arrows) affecting the left femoral (a) head, (b) neck, and (c) proximal shaft. Note the lack of periosteal reaction, fracture line, and soft-tissue abnormality.

The diagnostic considerations for the sclerotic femoral lesion were broad and included sclerosing bone dysplasias, overlap syndromes simulating bone dysplasias (osteoblastic neoplasms, Paget’s disease, myelofibrosis, Erdheim-Chester disease, sickle cell disease), severe stress response/healed fracture, and osteoid osteoma. Due to the patient’s demographics and lack of past medical and familial history, a diagnosis of intramedullary osteosclerosis was made. The patient was discharged without any specific followup instructions. Followup radiography performed approximately one year later showed that the lesion has remained stable.

Discussion

Intramedullary osteosclerosis is associated with abnormal bone formation in the medullary cavity of long bones and was first described as a distinct entity in 1988 (1). It typically affects the lower extremities and is most commonly found in the tibia; it occurs in adults and shows a female predilection. Intramedullary osteosclerosis is not associated with skeletal syndromes or familial diseases. While some cases may be discovered incidentally, most patients endorse a history of chronic, intermittent leg pain that is exacerbated by periods of increased physical activity (1). Imaging plays a key role in diagnosis, while correlation to the patient’s demographics, medical history, and family history facilitates differentiation from other osseous lesions.

The imaging findings of intramedullary osteosclerosis consist of homogeneous sclerosis that primarily affects the medullary cavity. In most cases, the cortex remains normal or is only minimally thickened. There is no associated bone deformity, and the periosteum is also unaffected. While there may be mild soft-tissue swelling adjacent to the affected bone, there is no discreet soft-tissue lesion. Intramedullary osteosclerosis may be bilateral and polyostotic; in these cases, the lesions are asymmetric.

Intramedullary sclerotic lesions often have nonspecific imaging findings and may be due to hereditary skeletal dysplasia, acquired skeletal dysplasia, malignancy, benign neoplasm, infection, or injury (2, 3, 4, 5). However, specific imaging and clinical findings may allow differentiation of intramedullary osteosclerosis from several other conditions. Intramedullary osteosclerosis lacks the periosteal reaction that is commonly caused by malignancies such as osteosarcoma, lymphoma, and osteoblastic metastases (6). Osetoid osteoma is associated with a radiolucent nidus, whereas intramedullary osteosclerosis results in homogeneous sclerosis (7). Chronic osteomyelitis should be considered only when the patient’s medical history, clinical, and laboratory parameters are appropriate (8). A healing stress fracture is often a consideration, since the presentation and imaging findings are often similar to intramedullary osteosclerosis; however, the absence of a discreet cortical fracture line usually allows differentiation (9). Several metabolic and endocrine disorders, such as renal osteodystrophy and pseudohypoparathyroidism, can usually be differentiated from intramedullary osteosclerosis by laboratory abnormalities and more diffuse osteosclerosis. Of the numerous sclerosing bone dysplasias, only Camurati-Engelmann disease and Ribbing disease have imaging findings that closely parallel those of intramedullary osteosclerosis; however, since both of these dysplasias are genetic diseases, do not preferentially affect women, and manifest earlier, they can typically be differentiated from intramedullary osteosclerosis (10, 11).