- Email: [email protected]
An Intraosseous Lipoma of the Calcaneus: A Case Report
The Journal of Foot & Ankle Surgery xxx (2014) 1–5
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Case Reports and Series
An Intraosseous Lipoma of the Calcaneus: A Case Report Alexander J. Pappas, DPM 1, Kyle E. Haffner, DPM, AACFAS 2, Samuel S. Mendicino, DPM, FACFAS 3 1
Third-Year Resident, West Houston Medical Center Houston, Houston, TX Podiatric Surgeon, Mountain View Orthopedics, Brighton, CO 3 Residency Director, West Houston Medical Center, Houston, TX 2
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 4
Intraosseous lipomas are one of the rarest bone tumors found in the body. The incidence has been reported to be <0.1% of all primary bone tumors. The differential diagnoses of an intraosseous lipoma in the calcaneus include plantar fasciitis, retrocalcaneal bursitis, gout, stress fracture, unicameral bone cyst, aneurysmal bone cyst, osteoblastoma, enchondroma, chondromyxoid fibroma, nonossifying fibroma, giant cell tumor, chondroblastoma, fibrous dysplasia, and chondrosarcoma. It has been reported that 60% to 70% of patients with an intraosseous lipoma present with symptoms. This article describes a case of a pathologic fracture secondary to a large intraosseous lipoma, the surgical treatments, and the subsequent resolution of symptoms. The purpose of our report was 3-fold: (1) to increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus; (2) to suggest a possible treatment protocol for intraosseous lipomas in the calcaneus; and (3) to describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle. Ó 2014 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: bone graft substitute calcaneal fracture heel pathologic fracture tumor
Intraosseous lipomas are one of the rarest bone tumors found in the body. The incidence has been reported to be less than 0.1% of all primary bone tumors (1,2). This low incidence may have been because some are asymptomatic and, therefore, are underreported (2–4). The differential diagnosis of an intraosseous lipoma in the calcaneus includes plantar fasciitis, retrocalcaneal bursitis, gout, stress fracture, unicameral bone cyst, aneurysmal bone cyst, osteoblastoma, enchondroma, chondromyxoid fibroma, nonossifying fibroma, giant cell tumor, chondroblastoma, fibrous dysplasia, and chondrosarcoma. Intraosseous lipomas are most commonly found in the lower extremity. It has been reported that 60% to 70% of patients with intraosseous lipoma will present with symptoms. The source of pain, expressed by some patients, has been theorized to be secondary to microfractures from minor trauma (5). When symptoms are present, a mild, dull pain is most common (1). Edema surrounding the calcaneus has also been found (2). On plain films, an intraosseous lipoma will typically present as a radiolucent lesion with a thin, well-defined margin. Magnetic resonance imaging will show the tumor in high signal on T1- and T2-weighted sequences. A higher grade intraosseous lipoma that Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Alexander John Pappas, DPM, Podiatric Medical Surgery Resident Program, West Houston Medical Center, 12121 Richmond Avenue, Suite 417, Houston, TX 77062. E-mail address: [email protected] (A.J. Pappas).
expresses trabeculation and calcification will be seen on both magnetic resonance imaging and computed tomography. Pathologic fracture of the calcaneus secondary to intraosseous lipoma has been reported, and precautions are therefore warranted to prevent this problem (1,3). The present report describes the case of a pathologic fracture secondary to a large intraosseous lipoma, the surgical treatments, and the subsequent resolution of symptoms. The purpose of this article was 3-fold: 1. To increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus 2. To suggest a treatment protocol for intraosseous lipomas in the calcaneus
Fig. 1. Lateral radiograph of the calcaneal fracture at the initial presentation.
1067-2516/$ - see front matter Ó 2014 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2014.03.007
2
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
Fig. 4. Lateral radiograph of the 12-week postoperative right bone block arthrodesis.
Fig. 2. Calcaneal axial radiographs of the calcaneal fracture at the initial presentation.
3. To describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle.
Case Report A 38-year-old male presented to the podiatry service with a right calcaneal fracture after referral through the emergency department on July 22, 2008. The patient stated that the injury had occurred 2 days earlier while running. He stated that he had fallen off a 2-ft curb,
Fig. 3. Intraoperative image of the initial subtalar joint fusion.
felt a pop, and experienced intense pain. The patient then proceeded to the emergency department. He had a medical history significant for insulin-dependent diabetes and hypertension. On physical examination, the patient had unremarkable blood flow with sensation grossly intact. He had marked edema in his right foot and ankle, with ecchymosis engulfing the lateral foot and medial arch. No fracture blisters were present. He related pain on palpation to the medial and lateral aspects of the right heel. He had no pain to his fibula or tibia, and there were no signs of compartment syndrome. On x-ray, a displaced calcaneal fracture was seen (Figs. 1 and 2). The patient was given a common peroneal nerve block for pain and placed in a Jones compression dressing to be non-weightbearing with crutches. He was given conservative and surgical options. The patient opted for conservative treatment. The patient was then monitored throughout 9 weeks of non-weightbearing. At week 6, physical therapy exercises were initiated. At 10 weeks after the injury, the patient had reported decreasing pain. On examination, no pain was found with subtalar joint range of motion. The patient was then transitioned to full weightbearing. He returned to the clinic 6 months after his original injury, with pain in his subtalar joint and in his anterior ankle. The patient was then scheduled for a right distraction arthrodesis of the subtalar joint with an autogenous iliac crest graft (Fig. 3). Postoperatively, he was kept non-weightbearing in a cast for 6 weeks, partial weightbearing in a fracture boot for 4 weeks, and then transitioned to full weightbearing at 12 weeks (Fig. 4). The patient continued to have pain for 10 months after surgery. Complex regional pain syndrome was ruled out, and he was referred to a pain management specialist. Serial computed tomography scans and magnetic resonance imaging revealed an intraosseous
Fig. 5. Mid-sagittal computed tomography slice of the calcaneus showing the increased lucency and areas of the lipoma in the anterior and posterior aspects of the calcaneus (arrows).
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
3
Fig. 6. Mid-sagittal T1-weighted magnetic resonance imaging image showing the posterior region of the intraosseous calcaneal lipoma (arrow).
Fig. 8. Intraoperative images of the locations of the lipoma before and after implantation of the Pro-DenseÒ matrix (Wright Medical Technology) with Trinity (OrthofixÒ).
lipoma with subtalar joint nonunion and graft resorption (Figs. 5 and 6). The origin of his pain was also localized to the sural nerve through a diagnostic block during this period. The patient then underwent a revisional arthrodesis with excision of the intraosseous bone tumor. The second surgery, to excise the lipoma, was performed through a lateral extensile incision, typically used for calcaneal fractures. Two cortical bone windows were created in the calcaneus to gain access to the lipoma (Figs. 7 and 8). The bone tumor was removed and sent for pathologic examination, and a bone graft (PRO-DENSEÒ Bone Graft Substitute, Wright Medical Technology, Memphis, TN) was
implanted in the deficits (Figs. 9 and 10). A revisional subtalar joint arthrodesis was also executed using a headless partial threaded screw (TrinityÒ EvolutionÔ, OrthofixÒ, Curac¸ao, Netherlands Antilles) with mesenchymal augmentation (Fig. 11). The patient was followed through 6 weeks of non-weightbearing, 4 weeks of partial weightbearing in fracture boot, then full weightbearing at 10 weeks. The last visit was 14 months after his last surgery, and he related no complaints. The patient was seen approximately 13 months after his last surgery and had evidence of union and adequate alignment of the subtalar joint (Figs. 12 and 13). As of May 1, 2014, the patient was back at work without sequelae.
Fig. 7. Intraoperative images of the locations of the lipoma before and after implantation of the Pro-Dense matrix (Wright Medical Technology) with Trinity (OrthofixÒ).
Fig. 9. Intraoperative photograph of posterior and anterior calcaneal cortical windows.
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A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
Fig. 12. Lateral radiograph approximately trabeculation across the subtalar joint.
Fig. 10. Intraoperative photograph of calcaneus after cortical windows were placed back to their original positions.
Discussion The intraosseous lipoma was first described in 1880 (3). The incidence has been low, reported to be less than 0.1% of all primary bone tumors (1,2). The true etiology is unknown and controversial. Some authors believe that they arise as benign primary bone tumors consisting of mature adipose tissue (1,4). Approximately 300 cases have been reported (1). Male gender is a predilection at 59% (2). The latest review by Kapukaya et al (2) stated that patients with intraosseous will be symptomatic 60% of the time. The most common presenting symptoms have been pain and swelling (2). The most common locations have been the femur and calcaneus (2,4–7). In all reported cases of intraosseous lipomas of the calcaneus, the lipoma appears in the neutral or critical angle of the calcaneus (3,5,8) (Fig. 14). One of the primary concerns of an intraosseous lipoma is its size and the potential for pathologic fracture. After a review of the
Fig. 11. Immediate postoperative radiograph of the revision subtalar joint arthrodesis with excision of the lipoma.
13
months
postoperatively
showing
published data, we found only 2 reported cases of pathologic fracture in the calcaneus and 5 total in a review study (1,2,8). Narang et al (3) developed a theory termed a critical size cyst. They surmised that if an intraosseous lipoma extends the full breadth of the calcaneus laterally to medially in the coronal plane and occupies at least 30% of the length anteroposteriorly, surgery would be advised (3). This analysis would require magnetic resonance imaging. Malignant transformation of intraosseous lipoma is rare but has been reported. Milgram (9) described 4 cases, 2 of which were fatal. Milgram (4) also developed a staging system for intraosseous lipoma. A stage 1 lesion is tissue grossly resembling normal fat. The cells will be interspersed with fine bony trabeculae. Histolologically, the lesion cells will be indistinguishable from normal lipocytes (4). A stage 2 lesion is similar to stage 1 grossly; however, when viewed microscopically, areas of necrotic fat that have undergone focal secondary calcification will be present (4). Reactive ossification can develop adjacent to areas of necrotic fat and will resemble primitive woven bone. A stage 3 lesion is a complete infarction, with necrotic fat,
Fig. 13. Calcaneal axial radiograph taken the same day as the lateral radiograph showing adequate alignment of fusion in the transverse and frontal planes.
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
5
Fig. 16. The specimen after staining with hematoxylin and eosin stain at 10 power magnification.
Fig. 14. Radiograph demonstrating the neutral triangle (yellow) of the calcaneus.
calcified fat, cyst formation and reactive peripheral bone formation (4,5). Radiographically, intraosseous lipoma appears as a osteolytic, well-circumscribed lesion with a thin sclerotic rim (3). It has classically been defined as a central nidus of calcification, resembling a “cockade image” (10). Our case was classified as Milgram stage 1 because no evidence of necrotic fat was found on histologic examination or magnetic resonance imaging (Figs. 6, 15, and 16). The most unique feature of the present case is that the lipoma was not exclusively found in the neutral triangle of the calcaneus. The majority of the lipoma was anterior and posterior to the neutral triangle. It appears that the neutral triangle was largely spared by this lesion.
We believe that when a patient with an intraosseous lipoma is symptomatic and does not respond to standard conservative treatment, surgical intervention is warranted and advised. This will be true unless the lipoma has been characterized as a “critical size cyst.” If the lipoma is “a critical size cyst,” surgery is advised, regardless of symptom presence, to prevent pathologic fracture. In our case, the original injury was a pathologic fracture. This diagnosis was missed because the patient did not want to pursue surgery and advanced imaging was denied by patient, primarily for financial reasons. During surgery, the lipoma should be excised using curettage and the defect replaced with a bone substitute of choice. The lesion should be sent for a histologic analysis and a definitive diagnosis. When a patient has a nonsymptomatic lesion, serial radiographs should be taken every 6 months to monitor the lipoma’s size. The purpose of our report was threefold. First, we wished to increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus. Second, we have suggested a possible treatment protocol for intraosseous lipomas in the calcaneus. Finally, we sought to describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle. References
Fig. 15. The specimen after staining with hematoxylin and eosin stain at 4 power magnification.
1. Bagatur AE, Yalcinkaya M, Dogan A, Gur S, Mumcuoglu E, Albayrak M. Surgery is not always necessary in intraosseous lipoma. Orthopedics 33, 2010. 2. Kapukaya A, Subasi M, Dabak N, Ozkul E. Osseous lipoma: eleven new cases and review of the literature. Acta Orthop Belg 72:603–614, 2006. 3. Narang S, Gangopadhyay M. Calcaneal intraosseous lipoma: a case report and review of the literature. J Foot Ankle Surg 50:216–220, 2011. 4. Milgram JW. Intraosseous lipomas: radiologic and pathologic manifestations. Radiology 167:155–160, 1988. 5. Campbell RS, Grainger AJ, Mangham DC, Beggs I, Teh J, Davies AM. Intraosseous lipoma: report of 35 new cases and a review of the literature. Skeletal Radiol 32:209–222, 2003. 6. Futani H, Fukunaga S, Nishio S, Yagi M, Yoshiya S. Successful treatment of bilateral calcaneal intraosseous lipomas using endoscopically assisted tumor resection. Anticancer Res 27:4311–4314, 2007. 7. Gonzolez JV, Stuck RM, Streit N. Intraosseous lipoma of the calcaneus: a clinicopathologic study of three cases. J Foot Ankle Surg 36:306–310, 1997. 8. Weinfeld GD, Yu GV, Good JJ. Intraosseous lipoma of the calcaneus: a review and report of four cases. J Foot Ankle Surg 41:398–411, 2002. 9. Milgram JW. Malignant transformation in bone lipomas. Skeletal Radiol 19:347–352, 1990. 10. Bruni L. The “cockade” image: a diagnostic sign of calcaneum intraosseous lipoma. Rays 11:51–54, 1986.
Contents lists available at ScienceDirect
The Journal of Foot & Ankle Surgery journal homepage: www.jfas.org
Case Reports and Series
An Intraosseous Lipoma of the Calcaneus: A Case Report Alexander J. Pappas, DPM 1, Kyle E. Haffner, DPM, AACFAS 2, Samuel S. Mendicino, DPM, FACFAS 3 1
Third-Year Resident, West Houston Medical Center Houston, Houston, TX Podiatric Surgeon, Mountain View Orthopedics, Brighton, CO 3 Residency Director, West Houston Medical Center, Houston, TX 2
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 4
Intraosseous lipomas are one of the rarest bone tumors found in the body. The incidence has been reported to be <0.1% of all primary bone tumors. The differential diagnoses of an intraosseous lipoma in the calcaneus include plantar fasciitis, retrocalcaneal bursitis, gout, stress fracture, unicameral bone cyst, aneurysmal bone cyst, osteoblastoma, enchondroma, chondromyxoid fibroma, nonossifying fibroma, giant cell tumor, chondroblastoma, fibrous dysplasia, and chondrosarcoma. It has been reported that 60% to 70% of patients with an intraosseous lipoma present with symptoms. This article describes a case of a pathologic fracture secondary to a large intraosseous lipoma, the surgical treatments, and the subsequent resolution of symptoms. The purpose of our report was 3-fold: (1) to increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus; (2) to suggest a possible treatment protocol for intraosseous lipomas in the calcaneus; and (3) to describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle. Ó 2014 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: bone graft substitute calcaneal fracture heel pathologic fracture tumor
Intraosseous lipomas are one of the rarest bone tumors found in the body. The incidence has been reported to be less than 0.1% of all primary bone tumors (1,2). This low incidence may have been because some are asymptomatic and, therefore, are underreported (2–4). The differential diagnosis of an intraosseous lipoma in the calcaneus includes plantar fasciitis, retrocalcaneal bursitis, gout, stress fracture, unicameral bone cyst, aneurysmal bone cyst, osteoblastoma, enchondroma, chondromyxoid fibroma, nonossifying fibroma, giant cell tumor, chondroblastoma, fibrous dysplasia, and chondrosarcoma. Intraosseous lipomas are most commonly found in the lower extremity. It has been reported that 60% to 70% of patients with intraosseous lipoma will present with symptoms. The source of pain, expressed by some patients, has been theorized to be secondary to microfractures from minor trauma (5). When symptoms are present, a mild, dull pain is most common (1). Edema surrounding the calcaneus has also been found (2). On plain films, an intraosseous lipoma will typically present as a radiolucent lesion with a thin, well-defined margin. Magnetic resonance imaging will show the tumor in high signal on T1- and T2-weighted sequences. A higher grade intraosseous lipoma that Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Alexander John Pappas, DPM, Podiatric Medical Surgery Resident Program, West Houston Medical Center, 12121 Richmond Avenue, Suite 417, Houston, TX 77062. E-mail address: [email protected] (A.J. Pappas).
expresses trabeculation and calcification will be seen on both magnetic resonance imaging and computed tomography. Pathologic fracture of the calcaneus secondary to intraosseous lipoma has been reported, and precautions are therefore warranted to prevent this problem (1,3). The present report describes the case of a pathologic fracture secondary to a large intraosseous lipoma, the surgical treatments, and the subsequent resolution of symptoms. The purpose of this article was 3-fold: 1. To increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus 2. To suggest a treatment protocol for intraosseous lipomas in the calcaneus
Fig. 1. Lateral radiograph of the calcaneal fracture at the initial presentation.
1067-2516/$ - see front matter Ó 2014 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2014.03.007
2
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
Fig. 4. Lateral radiograph of the 12-week postoperative right bone block arthrodesis.
Fig. 2. Calcaneal axial radiographs of the calcaneal fracture at the initial presentation.
3. To describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle.
Case Report A 38-year-old male presented to the podiatry service with a right calcaneal fracture after referral through the emergency department on July 22, 2008. The patient stated that the injury had occurred 2 days earlier while running. He stated that he had fallen off a 2-ft curb,
Fig. 3. Intraoperative image of the initial subtalar joint fusion.
felt a pop, and experienced intense pain. The patient then proceeded to the emergency department. He had a medical history significant for insulin-dependent diabetes and hypertension. On physical examination, the patient had unremarkable blood flow with sensation grossly intact. He had marked edema in his right foot and ankle, with ecchymosis engulfing the lateral foot and medial arch. No fracture blisters were present. He related pain on palpation to the medial and lateral aspects of the right heel. He had no pain to his fibula or tibia, and there were no signs of compartment syndrome. On x-ray, a displaced calcaneal fracture was seen (Figs. 1 and 2). The patient was given a common peroneal nerve block for pain and placed in a Jones compression dressing to be non-weightbearing with crutches. He was given conservative and surgical options. The patient opted for conservative treatment. The patient was then monitored throughout 9 weeks of non-weightbearing. At week 6, physical therapy exercises were initiated. At 10 weeks after the injury, the patient had reported decreasing pain. On examination, no pain was found with subtalar joint range of motion. The patient was then transitioned to full weightbearing. He returned to the clinic 6 months after his original injury, with pain in his subtalar joint and in his anterior ankle. The patient was then scheduled for a right distraction arthrodesis of the subtalar joint with an autogenous iliac crest graft (Fig. 3). Postoperatively, he was kept non-weightbearing in a cast for 6 weeks, partial weightbearing in a fracture boot for 4 weeks, and then transitioned to full weightbearing at 12 weeks (Fig. 4). The patient continued to have pain for 10 months after surgery. Complex regional pain syndrome was ruled out, and he was referred to a pain management specialist. Serial computed tomography scans and magnetic resonance imaging revealed an intraosseous
Fig. 5. Mid-sagittal computed tomography slice of the calcaneus showing the increased lucency and areas of the lipoma in the anterior and posterior aspects of the calcaneus (arrows).
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
3
Fig. 6. Mid-sagittal T1-weighted magnetic resonance imaging image showing the posterior region of the intraosseous calcaneal lipoma (arrow).
Fig. 8. Intraoperative images of the locations of the lipoma before and after implantation of the Pro-DenseÒ matrix (Wright Medical Technology) with Trinity (OrthofixÒ).
lipoma with subtalar joint nonunion and graft resorption (Figs. 5 and 6). The origin of his pain was also localized to the sural nerve through a diagnostic block during this period. The patient then underwent a revisional arthrodesis with excision of the intraosseous bone tumor. The second surgery, to excise the lipoma, was performed through a lateral extensile incision, typically used for calcaneal fractures. Two cortical bone windows were created in the calcaneus to gain access to the lipoma (Figs. 7 and 8). The bone tumor was removed and sent for pathologic examination, and a bone graft (PRO-DENSEÒ Bone Graft Substitute, Wright Medical Technology, Memphis, TN) was
implanted in the deficits (Figs. 9 and 10). A revisional subtalar joint arthrodesis was also executed using a headless partial threaded screw (TrinityÒ EvolutionÔ, OrthofixÒ, Curac¸ao, Netherlands Antilles) with mesenchymal augmentation (Fig. 11). The patient was followed through 6 weeks of non-weightbearing, 4 weeks of partial weightbearing in fracture boot, then full weightbearing at 10 weeks. The last visit was 14 months after his last surgery, and he related no complaints. The patient was seen approximately 13 months after his last surgery and had evidence of union and adequate alignment of the subtalar joint (Figs. 12 and 13). As of May 1, 2014, the patient was back at work without sequelae.
Fig. 7. Intraoperative images of the locations of the lipoma before and after implantation of the Pro-Dense matrix (Wright Medical Technology) with Trinity (OrthofixÒ).
Fig. 9. Intraoperative photograph of posterior and anterior calcaneal cortical windows.
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A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
Fig. 12. Lateral radiograph approximately trabeculation across the subtalar joint.
Fig. 10. Intraoperative photograph of calcaneus after cortical windows were placed back to their original positions.
Discussion The intraosseous lipoma was first described in 1880 (3). The incidence has been low, reported to be less than 0.1% of all primary bone tumors (1,2). The true etiology is unknown and controversial. Some authors believe that they arise as benign primary bone tumors consisting of mature adipose tissue (1,4). Approximately 300 cases have been reported (1). Male gender is a predilection at 59% (2). The latest review by Kapukaya et al (2) stated that patients with intraosseous will be symptomatic 60% of the time. The most common presenting symptoms have been pain and swelling (2). The most common locations have been the femur and calcaneus (2,4–7). In all reported cases of intraosseous lipomas of the calcaneus, the lipoma appears in the neutral or critical angle of the calcaneus (3,5,8) (Fig. 14). One of the primary concerns of an intraosseous lipoma is its size and the potential for pathologic fracture. After a review of the
Fig. 11. Immediate postoperative radiograph of the revision subtalar joint arthrodesis with excision of the lipoma.
13
months
postoperatively
showing
published data, we found only 2 reported cases of pathologic fracture in the calcaneus and 5 total in a review study (1,2,8). Narang et al (3) developed a theory termed a critical size cyst. They surmised that if an intraosseous lipoma extends the full breadth of the calcaneus laterally to medially in the coronal plane and occupies at least 30% of the length anteroposteriorly, surgery would be advised (3). This analysis would require magnetic resonance imaging. Malignant transformation of intraosseous lipoma is rare but has been reported. Milgram (9) described 4 cases, 2 of which were fatal. Milgram (4) also developed a staging system for intraosseous lipoma. A stage 1 lesion is tissue grossly resembling normal fat. The cells will be interspersed with fine bony trabeculae. Histolologically, the lesion cells will be indistinguishable from normal lipocytes (4). A stage 2 lesion is similar to stage 1 grossly; however, when viewed microscopically, areas of necrotic fat that have undergone focal secondary calcification will be present (4). Reactive ossification can develop adjacent to areas of necrotic fat and will resemble primitive woven bone. A stage 3 lesion is a complete infarction, with necrotic fat,
Fig. 13. Calcaneal axial radiograph taken the same day as the lateral radiograph showing adequate alignment of fusion in the transverse and frontal planes.
A.J. Pappas et al. / The Journal of Foot & Ankle Surgery xxx (2014) 1–5
5
Fig. 16. The specimen after staining with hematoxylin and eosin stain at 10 power magnification.
Fig. 14. Radiograph demonstrating the neutral triangle (yellow) of the calcaneus.
calcified fat, cyst formation and reactive peripheral bone formation (4,5). Radiographically, intraosseous lipoma appears as a osteolytic, well-circumscribed lesion with a thin sclerotic rim (3). It has classically been defined as a central nidus of calcification, resembling a “cockade image” (10). Our case was classified as Milgram stage 1 because no evidence of necrotic fat was found on histologic examination or magnetic resonance imaging (Figs. 6, 15, and 16). The most unique feature of the present case is that the lipoma was not exclusively found in the neutral triangle of the calcaneus. The majority of the lipoma was anterior and posterior to the neutral triangle. It appears that the neutral triangle was largely spared by this lesion.
We believe that when a patient with an intraosseous lipoma is symptomatic and does not respond to standard conservative treatment, surgical intervention is warranted and advised. This will be true unless the lipoma has been characterized as a “critical size cyst.” If the lipoma is “a critical size cyst,” surgery is advised, regardless of symptom presence, to prevent pathologic fracture. In our case, the original injury was a pathologic fracture. This diagnosis was missed because the patient did not want to pursue surgery and advanced imaging was denied by patient, primarily for financial reasons. During surgery, the lipoma should be excised using curettage and the defect replaced with a bone substitute of choice. The lesion should be sent for a histologic analysis and a definitive diagnosis. When a patient has a nonsymptomatic lesion, serial radiographs should be taken every 6 months to monitor the lipoma’s size. The purpose of our report was threefold. First, we wished to increase awareness of intraosseous lipomas and their potential to cause pathologic fractures in the calcaneus. Second, we have suggested a possible treatment protocol for intraosseous lipomas in the calcaneus. Finally, we sought to describe a rare case of an intraosseous lipoma of the calcaneus not located exclusively in the neutral triangle. References
Fig. 15. The specimen after staining with hematoxylin and eosin stain at 4 power magnification.
1. Bagatur AE, Yalcinkaya M, Dogan A, Gur S, Mumcuoglu E, Albayrak M. Surgery is not always necessary in intraosseous lipoma. Orthopedics 33, 2010. 2. Kapukaya A, Subasi M, Dabak N, Ozkul E. Osseous lipoma: eleven new cases and review of the literature. Acta Orthop Belg 72:603–614, 2006. 3. Narang S, Gangopadhyay M. Calcaneal intraosseous lipoma: a case report and review of the literature. J Foot Ankle Surg 50:216–220, 2011. 4. Milgram JW. Intraosseous lipomas: radiologic and pathologic manifestations. Radiology 167:155–160, 1988. 5. Campbell RS, Grainger AJ, Mangham DC, Beggs I, Teh J, Davies AM. Intraosseous lipoma: report of 35 new cases and a review of the literature. Skeletal Radiol 32:209–222, 2003. 6. Futani H, Fukunaga S, Nishio S, Yagi M, Yoshiya S. Successful treatment of bilateral calcaneal intraosseous lipomas using endoscopically assisted tumor resection. Anticancer Res 27:4311–4314, 2007. 7. Gonzolez JV, Stuck RM, Streit N. Intraosseous lipoma of the calcaneus: a clinicopathologic study of three cases. J Foot Ankle Surg 36:306–310, 1997. 8. Weinfeld GD, Yu GV, Good JJ. Intraosseous lipoma of the calcaneus: a review and report of four cases. J Foot Ankle Surg 41:398–411, 2002. 9. Milgram JW. Malignant transformation in bone lipomas. Skeletal Radiol 19:347–352, 1990. 10. Bruni L. The “cockade” image: a diagnostic sign of calcaneum intraosseous lipoma. Rays 11:51–54, 1986.