Highlights
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Intraosseous Lipoma.
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Osteomyelitis.
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Pathologic Fracture.
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Post-Operative Complications.
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Case Study.
Abstract
Intraosseous lipoma is a very rare finding, which can occur in the calcaneus with unknown etiology. Up to 33% of these lesions are asymptomatic, with between 25–40% of lesions found incidentally. Patients often present with pain, tenderness and swelling, and in severe cases pathological fracture at initial presentation. The aim is to review a multi-faceted case involving evaluation and surgical management of a pathologic fracture of a large intraosseous lipoma of the calcaneus, and subsequent management of complications over a course of 9 months. An overview of the literature detailing intraosseous lipoma is also presented. 49-year-old male presents after a fall from four feet, immediate onset of pain to the right rearfoot, unable to ambulate. Physical exam revealed ecchymosis to medial instep, edema. Radiographs and CT initially obtained, and MRI later revealed intraosseous lipoma involving 80% of the body of the calcaneus with pathological intraarticular fracture. The patient underwent excision via curettage, void fill with bone cement, and plate and screw fixation. Patient later developed osteomyelitis of the calcaneus, requiring removal of hardware and bone cement, and later replacement with an antibiotic spacer. Patient has since required no further surgical intervention. This case presentation seeks to further the literature in understanding of intraosseous lipoma, in addition to the complicating pathologic fracture to the calcaneus.
Introduction
Intraosseous Lipoma (IL) is a very rare condition which develops as a proliferation of mature adipose cells or lipocytes that are larger than non-tumorous fat cells within cancellous bone. , The bone lesion may undergo degenerative changes such as fat necrosis, cyst formation, and calcification. , It is theorized that ILs are primary bone tumors, but the pathogenesis is largely unknown. , The first case description and literature review dates to 19,76, however IL was first described in 18,80. In some case series there is a slight predominance in men, and patients are typically diagnosed at around age 40, but range from 5 to 70. , The total incidence is between 0.02 and 0.1 % of all primary benign bone tumors. ,,, Occurrence in the lower limb is most common with some authors reporting up to 71 % of cases and between 15–30 % isolated to the calcaneus. ,,, The femur has been shown to be the most common location. IL is also reported in the tibia and fibula but can occur in any bone of the body including the spine, pelvis, skull, and rib bones. ,, Multiple case reports have been presented on management of IL within the mandible. ILs may be discovered incidentally on radiographs as patients are asymptomatic around 30 % of the time. ,, Approximately 70 % of patients will present with symptoms; most often heel pain and soft tissue swelling. ,,,, Diagnosis can be delayed as ILs may mimic common conditions like plantar fasciitis, Haglund’s deformity, or stress fractures. Conservative management includes rest, ice, and non-steroidal anti-inflammatory drug (NSAID) therapies. Surgical treatment in the setting of suspicion or evidence of malignancy, or risk/presence of pathological fracture consists of resection or curettage of the lesion followed by autograft, artificial bone substitute, or bone cement filling. ,,,,, Some authors report that pathologic fracture of the calcaneus in the setting of IL is very uncommon, and there are very few cases in the literature involving pathologic fracture. ,
Osteomyelitis (OM) is defined as inflammation of bone or bone marrow. The inflammation is typically caused by a microbial infection which can lead to deterioration and cell death of the bony structures and osteoblasts. Posttraumatic and postoperative osteomyelitis (PPOM) is becoming more common, accounting for up to 80 % of all cases of osteomyelitis. ,, The development of PPOM can be divided into three categories based on time of appearance. Acute occurs within two weeks, subacute from two to six weeks, and chronic greater than six weeks after initial trauma or procedure. Chronic osteomyelitis can lead to long hospital stays and increased morbidity and mortality, especially in elderly patients and those with comorbidities such as diabetes. Risk factors like infected hardware, open fractures, severe or comminuted fracture types, male sex, advanced age, diabetes and incisions longer than 10 cm can all increase the risk of developing osteomyelitis after surgical correction. Osteomyelitis of the calcaneus leads to specific challenges in management. 3–10 % of all osteomyelitis occurs in the calcaneus and is commonly associated with the previously mentioned risk factors, in addition to heel ulceration. , Management of calcaneal osteomyelitis should involve the following objectives: excision of all necrotic bone and soft tissue, appropriate dead space management, preservation of weight bearing capacity, and adequate soft tissue coverage for a well vascularized environment.
The purpose of this study is to present a patient with long-standing asymptomatic intraosseous lipoma of the calcaneus that sustained a traumatic, pathologic, closed fracture after a fall from a height. Additionally, this patient went on to develop soft tissue and hardware infection as well as biopsy-confirmed postoperative osteomyelitis. The subsequent management and follow up of his pathology and postoperative complications are also presented, along with a brief review of the body of literature.
Case report
Written permission was obtained from the patient to utilize their case information, removing all patient identifiers. A 49-year-old male patient with a past medical history of diabetes mellitus type two, 43 pack years of tobacco use, and high cholesterol presented to the emergency department in January of 2022. He reported falling from a height of four feet onto his right foot with subsequent pain and inability to bear weight to the heel. Physical exam revealed ecchymosis to medial instep and edema. Radiographs of the right ankle revealed a lucent lesion within the calcaneus with adjacent bone fragments concerning for a pathologic fracture. A recommended computed tomography (CT) scan revealed a comminuted pathologic fracture involving the thin cortex of the lytic lesion of the calcaneus. (See Fig. 1 ) The fracture extended to the posterior subtalar joint and the calcaneocuboid joint, as well as the plantar surface of the calcaneus. Moderate height loss was noted. The patient was provided pain medication, a long controlled-ankle-motion (CAM) boot, was advised to remain non-weightbearing and referred to podiatry.
A. Lateral ankle radiograph. B. CT ankle axial proximal calcaneus. C. CT axial mid calcaneus. D. CT axial distal calcaneus. E. CT coronal through posterior facet of subtalar joint. F. CT sagittal showing extent of lytic lesion.
At follow up two days later, podiatry recommended Magnetic Resonance Imaging (MRI) of the ankle for further evaluation of the lytic lesion. Patient returned to clinic early in February after obtaining the MRI, at which time he was diagnosed with an IL involving 80 % of the body of the calcaneus with a closed, displaced intra-articular fracture. (See Fig. 2 ) After education and discussion with the patient, it was determined that he would undergo surgical correction.
A. MRI ankle sagittal T1. B. MRI ankle sagittal T2.
The procedure was performed approximately 6 weeks after the initial injury in March of 2022. The patient had delayed the procedure for personal reasons. Through a lateral extensile incisional approach, curettage and evacuation of the IL was completed with placement of a calcium sulfate-based bone cement product within the remaining bone defect. A calcaneal fracture plate and 3.5 mm locking and non-locking screw fixation construction was applied to the reduced fracture and hardened bone cement. Anatomic alignment was restored to the calcaneus and hindfoot. Closure was performed in layers and an incisional wound vac was applied. (See Fig. 3 )
A. Post-curettage and evacuation of IL. B. After placement of bone cement. C. Lateral radiograph at postop.
The surgical plan was then to return to the OR after the bone cement had incorporated for a subtalar joint fusion in the setting of intra-articular involvement of the pathologic fracture. In the follow up period 2.5 months from index procedure the patient began to note new onset of pain, increased lateral ankle swelling, and waxing and waning dehiscence with drainage from incision site. Two separate swab and tissue cultures revealed infection with Enterobacter cloacae and Enterococcus faecalis, therefore he was treated with multiple courses of antibiotics including Bactrim and Ciprofloxacin along with local wound care. In July of 2022, the patient was brought back to the OR for incision and drainage of previous surgical site, during which both tissue and bone biopsies were obtained. All hardware was removed due to concern for deep extension of infection. Tissue cultures revealed the same species of bacteria, while bone biopsy was negative for osteomyelitis. Post-operative care and Bactrim antibiotic continued through September of 2022, including negative pressure wound therapy. The skin was unable to close over three sites along the incision, with drainage noted. (See Fig. 4 )
Photograph of lateral ankle obtained in September of 2022.
An MRI of the ankle was obtained with concerns for osteomyelitis with a sinus tract. (See Fig. 5 )
