2. What is the lesion’s size and extent? Aggressive lesions tend to be larger and grow faster. Exceptions include fibrous dysplasia (FD) that may involve not only the entire bone but also several bones at the same time and nonetheless is a benign condition. Multiple lesions or generalized bone weakness may pose another challenge in the prevention and management of pathologic fractures.
3. What is the lesion doing to the bone? The pattern of bone involvement and/or destruction plays an important role in the bone strength. For example, lytic lesions (e.g., unicameral bone cyst [UBC]) put the bone at a much higher risk of pathologic fracture than blastic lesions (e.g., osteoblastoma).
4. What is the bone’s response? If the bone has time to “compensate” for its destruction caused by a lesional process, new bone formation and cortical thickening may be observed and will to some point prevent or delay apathologic fracture.
One of the challenges dealing with a “weakened” bone is to predict the likelihood of fracture. The combination of bending and torsional rigidity measured noninvasively with quantitative CT was found to be more accurate for predicting pathologic fracture through benign bone lesions in children than the standard radiographic criteria (42% to 61% accuracy).129,253
An important consideration in the management of pathologic fracture is that the underlying cause often needs to be addressed to achieve fracture healing; therefore, the treatment plan must consider both the treatment of the fracture and its underlying cause, at times deviating from the classic principles of pediatric fractures.
This chapter describes the clinical and radiographic features of the most common causes of pediatric pathologic fractures, including specific patterns of injury and special concerns of treatment. The goals are to warn and prepare the orthopedic surgeon for the correct diagnostic approach and management of these lesions.
TUMORS OR TUMOR-LIKE PROCESSES
Benign tumors can be classified according to their aggressiveness (Table 8-2). Stage 1, or latent benign lesions, are usually asymptomatic, discovered incidentally, and seldom associated with pathologic fracture. Stage 2 lesions are intermediate in behavior, and stage 3, or aggressive benign lesions, are usually symptomatic, grow rapidly, and may be associated with pathologic fracture.
TABLE 8-2 Classification of Benign Lesions According to Their Aggressiveness
Unicameral Bone Cyst
Unicameral bone cyst (UBC), also known as simple bone cyst, is a benign, active or latent, solitary cystic lesion that usually involves the metaphysis or metadiaphysis of long bones. In the order of decreasing frequency, UBCs are most commonly seen in the proximal humerus, proximal femur, proximal tibia, distal tibia, distal femur, calcaneous, distal humerus, radius, fibula, ilium, ulna, and rib.201,202 Although the etiology is unknown, one of the most accepted theories is that UBC is caused by obstruction of the drainage of interstitial fluid.54,57
UBCs are classified based on their proximity to the adjacent growth plate. Active cysts are close to the physeal line, and inactive or latent cysts have “migrated” away from the growth plate as longitudinal growth occurs and therefore are far from the epiphysis2202,202
The vast majority of patients are younger than 20 years old.54,275 The male-to-female ratio is about 2:1.46,202 UBCs are often asymptomatic and, in approximately 80% of cases, the initial presentation is with a pathologic fracture following minor trauma.49,76,77,275 The fractures are usually incomplete or minimally displaced, and tend to heal uneventfully. In approximately 10% of the cases the cyst heals following the fracture.5,73,75 Lower extremity fractures, particularly around the hip, often need surgical intervention.
Plain radiographs are usually diagnostic; UBC is a well-defined, centrally located, radiolucent/lytic cystic lesion with narrow zone of transition. Cortical thinning and mild expansion are common. When a pathologic fracture occurs, there is periosteal reaction and occasionally the typical “fallen fragment” sign is visualized (fragment of bone “floating” inside the fluid-filled cystic cavity). CT is useful for lesions located in areas that are of difficult visualization on plain films (e.g., spine, pelvis) and to rule out minimally displaced fractures. Magnetic resonance imaging (MRI) is sometimes used for differential diagnosis of atypical UBCs. Although the characteristics are nonspecific, UBCs usually present as low-to-intermediate signals on T1-weighted images and a bright and homogeneous signals on T2-weighted images (Fig. 8-3).184
The differential diagnosis includes aneurysmal bone cyst (ABC), nonossifying fibroma, FD (especially for diaphyseal tumors), brown tumor of hyperparathyroidism, and osteomyelitis.
With time, UBCs tend to stabilize in size and “migrate” away from the growth plate. Although some lesions heal or disappear spontaneously at puberty,201,202 the majority will persist into adulthood (Table 8-3).
TABLE 8-3 Staging of Unicameral Bone Cysts
Lesions that have the typical radiographic appearance and therefore do not warrant biopsy for diagnostic confirmation, particularly those lesions in non–weight-bearing bones, can be followed with serial radiographs.
Large lesions that involve more than 50% to 80% of the bone diameter and lesions that are associated with marked cortical thinning are at high risk of fractures and may warrant prophylactic treatment.126,254 Lesions of weight-bearing bones, especially around the hip, are best addressed before a fracture (Fig. 8-4). Although several attempts have been made to predict the true risk of pathologic fracture associated with bone cysts, most of the data are related to other lesions, particularly among adults (Fig. 8-5). CT has been shown to be useful for predicting the likelihood of fracture. This method uses a computerized regression system and may help deciding which cysts warrant intervention.254
Although spontaneous resolution of UBCs following fracture may occur in up to 15% of the cases (Fig. 8-6), pathologic fractures associated with UBCs do not always heal uneventfully; malunion, growth arrest, and avascular necrosis are some of the reported complications.142,182
AUTHOR’S PREFERRED METHOD
We recommend treating the fracture conservatively prior to definitive treatment of the cyst. The main reasons are to allow possible spontaneous healing of the cyst and to make it easier to treat a stable bone, rather than two moving parts. The exception is select proximal femur fractures that may need rigid internal fixation.
Our preferred technique is a minimally invasive approach that combines aspiration, cystogram, biopsy, curettage, intramedullary decompression, and grafting with medical-grade calcium’.73,76 Complete cyst healing is achieved in over 80% of the cases.
• Under fluoroscopic guidance, a Jamshidi trocared needle (CardinalHalth, Dublin, OH) is percutaneously inserted into the cyst cavity, preferably in the middle of the cyst.
• The cyst is aspirated to confirm the presence of straw-colored fluid.
• Three to 10 mL of Renografin dye (E.R. Squibb, Princeton, NJ) is injected to perform a cystogram and confirm the single fluid-filled cavity.
• A 0.5-cm longitudinal incision is then made over the site of the aspiration and a 6-mm arthroscopy trocar is advanced into the cyst cavity through the same cortical hole. The cortical entry is then enlarged manually.
• Under fluroscopic guidance, percutaneous removal of the cyst lining is done with curved curettes and a pituitary rongeur.
• An angled curette and/or flexible intramedullary nail is used to perform the intramedullary decompression in one direction (toward diaphysis) or in both directions (if the growth plate is far enough to avoid injury).
• Bone grafting is done with medical-grade calcium sulfate pellets (Osteoset, Wright Medical Technology, Arlington, TN) inserted through the same cortical hole and deployed to completely fill the cavity. The pellets do not offer structural support but act as scaffolding for new bone formation and cyst healing. Angled curettes can be used to advance pellets into the medullary canal, which also confirms adequate decompression. Tight packing of the cyst is preferred.
• The wound is closed in a layered fashion.
Aneurysmal Bone Cyst
ABCs are benign, locally aggressive bone tumors.257 They are well-defined, eccentric, expansile, osteolytic, blood-filled lesions usually seen in the metaphyseal region of long bones (65% of cases) or in the posterior elements of the spine. ABCs have a tendency to expand beyond the width of the epiphyseal plate. Approximately 75% of ABCs are seen in patients younger than 20 years old, and 50% are seen in individuals between 10 and 20 years of age.46,62 The estimated incidence is of approximately 1.4 cases per 100,000, representing 1.5% of all primary bone tumors.62
In the order of decreasing frequency, the most commonly involved bones in the appendicular skeleton are the femur (∼20%), tibia (∼17%), spine (∼15%), humerus (∼13%), pelvis (∼8%), and fibula (∼7%).62 The spine is involved in up to 27% of the cases,46,62 with the posterior elements being the most common site with frequent extension into the vertebral body.39,98 The lumbar vertebrae are the most commonly affected.39
The etiology of ABCs is still unknown. The neoplastic basis of primary ABCs has been in part demonstrated by the chromosomal translocation t(16; 17)(q22; p13) that places the ubiquitin protease USP6 gene under the regulatory influence of the highly active osteoblast cadherin 11 gene, which is strongly expressed in bones.210 There is a fairly high incidence of ABCs associated with other benign and malignant tumors such as UBCs, nonossifying fibromas, FD, and osteogenic sarcoma.65,174,186 The most common presenting symptom is localized pain and/or swelling of less than 6 months duration; spinal lesions may present with radicular pain.46,69,98,104,159
On plain radiographs, ABCs present as an eccentric lytic lesion. Although usually the overlying cortex is intact, sometimes cortical disruption is identified. When that occurs, periosteal reaction is seen.37,159 Cystic septation is common, giving rise to the so-called soap bubble or honeycomb appearance. Lesions in the short tubular bones, such as the metacarpals and metatarsals, are commonly more central. Lesions near the growth plate tend to expand beyond the width of the adjacent epiphysis (Fig. 8-7), which can be a useful way to differentiate ABCs from UBCs which do not commonly expand as much beyond the width of the epiphysis. MRI is often helpful in obtaining better definition of axial lesions and in demonstrating the characteristic double density fluid level, septation, low signal on T1 images, and high intensity on T2 images; however, these findings are not pathognomonic for ABC.262
Campanacci et al.46 have classified ABCs into three groups. An aggressive cyst has signs of reparative osteogenesis with ill-defined margins and no periosteal shell. An active cyst has an incomplete periosteal shell and a defined margin between the lesion and the host bone. An inactive cyst has a complete periosteal shell and a sclerotic margin between the cyst and the long bone (Fig. 8-8).
Pathologic fractures occur in 11% to 35% of long bone lesions.98,159 The humerus and femur are the most common sites of pathologic fracture.98,158 The incidence of pathologic fracture associated with spinal lesions is approximately 20%.39,69,104 Conservative treatment with immobilization is usually inappropriate as a definitive treatment for pathologic fractures of ABCs. Although the pathologic fracture will heal, ABCs do not spontaneously heal and may enlarge; furthermore, tissue sampling is often needed for diagnosis confirmation.
Recurrence rates following intralesional curettage and bone grafting are as high as 30%.74,109,269 Several authors have shown that the recurrence is higher among younger children.24,60,74,98 Freiberg et al.98 treated ABCs with curettage and bone grafting in seven patients younger than 10 years of age and noted recurrence in five of the seven patients at an average of 8 months after the first procedure. Because of this high recurrence rate, several authors attempted the use of adjuvant, such as cryosurgery and cementation.183,239
AUTHOR’S PREFERRED METHOD
Four-Step Approach Resection
This technique has been previously described with reported recurrence rate for appendicular lesions around 8%.74,104 We recommend the use of headlamps for enhanced illumination and loupes for magnification. An image intensifier is available for intraoperative confirmation of complete tumor excision and appropriate bone grafting. Diagnostic tissue confirmation is an essential part of this technique. For large spinal tumors, preoperative embolization is recommended (Fig. 8-9). If instrumentation is needed after spine tumors resection, we recommend titanium or cobalt chrome instrumentation that gives a much better visualization of the spine on future MRIs (less artifact) than stainless steel (Fig. 8-10).
• Under fluoroscopic guidance, a small longitudinal incision is made over the cyst. No flaps are created, and the dissection is carried down to the lesion level. The cyst wall is usually easily penetrated with curettes. Care should be taken to control eventual significant bleeding at the time of cyst penetration.
• Lesional tissue is than retrieved and sent for frozen section for diagnostic confirmation.
• Upon diagnostic confirmation, the cortical window is enlarged using roungers or a high-speed burr to allow appropriate visualization and excision. Using angled and straight curettes of different sizes, the intralesional resection/curettage is performed (Step 1).
• After the first step, the high-speed burr is used to extend the intralesional margins as well to excise any residual tumoral cells (Step 2).
• Step 3 entails the use of electrocautery. This has two goals: First, it helps identify residual tumor pockets and second, has the theoretical capability of killing residual tumor cells.
• Adjuvant in the form of phenol solution 5% is used for appendicular lesions (Step 4).
• The lesion is now completely excised and bone grafting is performed, usually using a combination of allograft cancellous cubes and demineralized bone matrix paste. Tight packing of the cyst is preferred. Alternatively a bone substitute, such as tricalcium phosphate, may be used for immediate structural support.
• Internal fixation is done on case-by-case basis. Lesions of weight-bearing bones, particularly of the proximal femur, and some large vertebral lesions may warrant internal fixation/instrumentation following the four-step approach.
• The wound is closed in a layered fashion. Drain is used as needed and should exit the skin in line with the excision.
Fibrous Cortical Defects and Nonossifying Fibromas
Fibrous cortical defects (FCDs) are the most common bone tumor or tumor-like condition seen in the growing child. Both FCDs and the larger variant known as nonossifying fibroma (NOF) may be associated with pathologic fractures in children. Pathologic fractures through these lesions occur more commonly in boys between 6 and 14 years old.64
FCDs are small, well-defined, intracortical, metaphyseal lesions surrounded by a sclerotic rim with localized cortical thinning, ranging from 1 to 2 cm in diameter and most commonly found in the distal femur, proximal tibia, and fibula. FCDs can be incidentally found on radiographic studies of the lower extremity in approximately 25% of pediatric patients.64 In view of their usually asymptomatic nature, it is difficult to estimate the true incidence. They usually require no treatment other than observation.
NOFs present at a similar age as FCDs and follow a similar distribution of bone involvement; however, multiple lesions are present in approximately one-third of patients.79 Radiographically, they present as a well-defined, eccentric radiolucent cyst-like lesion of the metaphysis that may be mostly intracortical or intramedullary and are usually larger than 4 cm,15 sometimes extending across a substantial portion of the width of the long bone.64 NOFs are also usually asymptomatic unless a pathologic fracture is present.15,64
Several authors have suggested that FCDs and NOFs may regress spontaneously with time.79,83 Typically, this tumor remains asymptomatic and is commonly an incidental radiographic finding. However, lesions with extensive cortical involvement can cause pain because of pathologic fractures. Fractures through NOFs heal uneventfully but the lesion persists, and refracture may occur, but the incidence is low (Fig. 8-11).15,64,79,83
The size of the lesion seems to correlate directly to the risk of pathologic fracture.15 Arata et al.15 noted that all pathologic fractures associated with NOFs in the lower extremity occurred through lesions involving more than 50% of the transverse cortical diameter. These large lesions were defined as exhibiting more than 50% cortical involvement on anteroposterior (AP) and lateral radiographic studies and a height measurement of more than 33 mm.15 In their series, 43% of the pathologic fractures through NOFs were in the distal tibia. Although the authors recommended careful observation of these large NOFs, they suggested that “prophylactic curettage and bone grafting be considered if there is a reasonable chance of fracture.”15 Their series does not include any large lesion meeting their size criteria that did not fracture, and their hypothesis has never been tested in any published series. Drennan et al.79 suggested that large NOFs causing pain might predispose to fracture and recommended prophylactic curettage and bone grafting for select larger lesions.
Easley and Kneisel83 reported that although absolute size parameters were helpful in predicting pathologic fracture, they did not imply a requirement for prophylactic curettage and bone grafting. In their series, 13 (59%) large NOFs had not had pathologic fracture despite exceeding the previously established size threshold. In the nine (41%) patients in whom pathologic fracture occurred, healing was uneventful after closed reduction and cast immobilization, and no refractures occurred. They suggested that most patients with large NOFs can be monitored without intervention, because previous studies support spontaneous resolution of most of these lesions.15,64,79 All fractured NOFs in their series healed with closed reduction and immobilization.
Fractures are usually treated with immobilization until healing is obtained. Surgery is necessary only if the residual lesion of significant size to predispose the patient to further pathologic fractures, if there is chronic pain suggesting a stress fracture, or if there is doubt about the nature of the lesion.15,83
AUTHOR’S PREFERRED METHOD
Treatment is based on the size and location of the lesion and the type of pathologic fracture. Small lesions without fracture can be observed and may require 1 to 3 years to spontaneously resolve. Large lesions of the lower extremity in active children, even if they are assymptomatic, should either be followed carefully with serial radiographic studies or should undergo curettage and bone grafting to avoid pathologic fracture. Although absolute size parameters may be useful in predicting pathologic fracture, they do not imply a requirement for prophylactic curettage and bone grafting. Most patients with large NOFs can be monitored without surgical intervention, and fractures can be successfully managed with nonoperative treatment. Our experience is that a considerable number of incidentally discovered large NOFs do not fracture. Although we cannot readily identify an accurate denominator, we infer that many large NOFs remain unindentified and nonproblematic. Patient and family wishes and the individual’s activity demands also influence the decision. Given the historic evidence for spontaneous resolution and favorable healing characteristics of NOFs, patients with lesions larger than 50% of the width of the bone should be approached individually, especially in the presence of clinical symptoms (Fig. 8-12).
Enchondromas are latent or active benign cartilaginous tumors. These lesions are often incidentally found, but the most common presenting symptom is pain associated at times with swelling. The most common sites of involvement in decreasing order of frequency are the phalanges, metacarpals, metatarsals, humerus, and femur. Pathologic fracture is commonly the presenting symptom for enchondromas located in the phalanges of the hands or feet, but is rare for enchondromas in other locations.105
On plain radiographs, enchondromas are usually central intramedullary lesions with stippled calcification of the cartilage tumor matrix. Larger lesions may cause cortical thinning and scalloping and predisposal to pathologic fractures (Fig. 8-13).
Children may present with multiple enchondromas or enchondromatosis (Ollier disease), which is commonly seen between 2 and 10 years of age. Although the lesion itself is similar to a solitary enchondroma, deformity and shortening of the extremity because of growth disturbance may occur (Fig. 8-14).273 A typical radiographic finding of enchondromatosis is the presence of linear radiolucencies extending from the metaphysis down the shaft of the long bone, frequently seen in the hands.
When enchondromatosis is associated with multiple hemangiomas, it is known as Maffucci syndrome.175 In this syndrome, 30% of patients have one or more pathologic fractures.175 Approximately half of these fractures go on to delayed union or nonunion. Skeletal deformities tend to stabilize at maturity (Fig. 8-15). Sarcomatous degeneration has been reported in approximately 15% of patients.175
Asymptomatic lesions can be observed. Biopsy may be necessary when the identity of the lesion is uncertain. Symptomatic lesions respond well to curettage and bone grafting.105,273 Treatment should be individualized for displaced fractures.
AUTHOR’S PREFERRED METHOD
For asymptomatic patients with small lesions with classic radiographic findings, biopsy is not necessary. Curettage and bone grafting are necessary for those lesions with acute or impending pathologic fracture, or in cases of continued pain. Fixation is not necessary for lesions of the short tubular bones but may be necessary for lesions of the proximal femur or long bone of the lower extremity. Standard fracture care is adequate to treat most pathologic fractures, but the bone quality may be compromised by the tumor and it may be difficult fixation.
Osteochondromas are one of the most common tumors of bone in children, and clinical symptoms are usually related to irritation of the surrounding soft-tissue structures. The radiographic appearance is pathognomonic, with a continuity of the host bone cortex with the outer cortex of the lesion and intramedullary cavities, in the same fashion. Although fractures associated with osteochondromas are rare, they may occur through the base or stalk of a pedunculated tumor (Fig. 8-16).51 Fractures through osteochondromas should be treated conservatively; however, excision in the acute phase may be considered because the fragment is “floating free” in the soft tissues. The cartilage cap surrounding the lesion should always be removed to avoid the risk of recurrence.
Langerhans Cell Histiocytosis
Langerhans cell histiocytosis (LCH) is a rare group of disorders with a wide spectrum of clinical presentation, where the constant pathologic finding is the “Langerhans cell.” The present nomenclature defines solitary osseous lesion as eosinophilic granuloma (EG). The annual incidence of LCH is at 6 per million children per year.31 Males are affected to a slightly higher degree than females.43,133 It is predominantly a disease of childhood, with more than 50% of cases diagnosed between the ages of 1 and 15, and peak in incidence between the ages of 1 and 4.31,43 The clinical course of the disease is quite variable, with some forms undergoing seemingly spontaneous remission. The disease can be localized to a bone or single system, or multifocal involving multiple bones and/or systems.
Bone pain is the initial symptom in 50% to 90% of the patients with osseous lesion.72 Other reported symptoms in osseous LCH include swelling, tenderness, pathologic fractures, diminished hearing, and otitis media (mastoid lesions) or loose teeth (mandible lesions). Vertebral collapse may produce pain and spasm, torticollis may be seen with cervical spine lesions, and kyphosis might develop with thoracic lesions but neurologic symptoms are uncommon.97,174,224
The radiographic appearance is highly variable, but often lesions are radiolucent with well-defined margins, with or without surrounding sclerosis. Skeletal lesions may be solitary or multiple. Most long bone lesions involve the diaphysis or metaphysis, with destructive osteolysis and overlying expansion by periosteal layering.43 Epiphyseal involvement is rare but may occur.
Vertebral destruction with complete collapse of the vertebral body is classically referred to as “vertebra plana.” Adjacent intervertebral disc height is usually maintained (Fig. 8-17). Spinal lesions can be classified based on the amount and pattern of maximal vertebral collapse103: Grade I (0% to 50% of collapse), grade II (51% to 100%), or grade III (limited to the posterior elements); and A (symmetric collapse) or B (asymmetric collapse).
Biopsy is usually necessary to confirm the diagnosis and also to differentiate LCH from malignancies that may present with similar radiographic appearance. Biopsy can usually be done minimally invasively through the pedicle. One should not violate posterior ligaments or progressive kyphosis will result. If nonspine sites are biopsy-proven LCH, and the spine involvement is classic for vertebra plana, a biopsy of the spine may not be needed. Once the diagnosis is established, treatment options include observation or curettage and bone grafting.43,108,133 Surgical intervention is uncommon. Localized kyphosis is present, but can usually be treated with a brace (TLSO) for approximately 3 months. Chemotherapy with prednisone and vinblastine is indicated for cases of multiple bone involvement or visceral disease.16 Pathologic fracture is uncommon in patients with LCH. Standard fracture care is usually sufficient for pathologic fractures.
Malignant Bone Tumors and Metastasis
Pathologic fractures can sometimes be the presenting symptom of a malignant bone tumor (Fig. 8-18). The two most common primary bone malignancies in children are osteosarcoma and Ewing sarcoma. Destructive bone lesions can also be caused by metastasis, being more common than primary tumors in certain age groups. Careful staging and biopsy20,250 are critical in the approach to children with bone tumors. However, biopsy is not done without risks. One of the main complications following biopsies is pathologic fracture caused by a decrease in the torsional strength of the bone following cortical drilling. To prevent a pathologic fracture, an oval hole with smooth edges should be used, preferably in areas of less stress for weight-bearing bones. Sometimes, the biopsy hole can be filled with bone cement or other grafting material. Because most bone sarcomas are associated to a large soft-tissue mass that can be sampled, drilling of the bone may be avoided.
One of the major advances in the care of children with extremity sarcoma has been the development of limb-sparing surgical techniques for local control of the tumor. Pathologic fracture has previously been cited as a contraindication to limb salvage because of concerns about tumor dissemination by fracture hematoma, and inability in obtaining free margins following resection. Several studies, however, have shown that pathologic fractures eventually heal during neoadjuvant chemotherapy and may not preclude limb salvage, or affect survival rates (Fig. 8-19).89,278 Abudu et al.1 reviewed the surgical treatment and outcome of pathologic fractures in 40 patients with localized osteosarcoma and found that limb-sparing surgery with adequate margins could be achieved in many patients but that there was a 19% recurrence rate, without compromising overall survival. Scully et al.241 reviewed the surgical treatment of 18 patients with osteosarcoma and pathologic fractures. Of the 10 patients who had limb-sparing surgery, three had local recurrences and six had distant recurrences. Although the distant recurrence rate for patients undergoing amputation was no different from the rate for those undergoing limb salvage, the difference in local tumor control approached statistical significance. All patients who developed local recurrence died. The authors stated that surgical treatment should be individualized. Bacci et al.21 compared the disease-free survival and overall survival of 46 patients with nonmetastatic osteogenic sarcoma of the extremity and pathologic fracture to a cohort of 689 patients without pathologic fracture and found no significant difference. Limb-sparing surgery was possible and appropriate in carefully selected patients as long as wide margins could be safely achieved.
Pathologic fracture after limb-sparing surgery is another major complication, occurring most commonly after allograft reconstruction but also after limb salvage with endoprosthetic reconstruction.30,272 Berrey et al.30 reviewed 43 patients with fractures through a massive allograft used for limb reconstruction after resection of tumors. Four fractures healed with immobilization alone, and the remainder of patients attained satisfactory results with open reduction and grafting, replacement of the internal fixation device, or total joint replacement. San-Julian and Canadell238 reported on 12 patients with 14 fractures (10.2% of 137 patients with allograft for limb-sparing surgery in their series). They recommended intramedullary fixation whenever possible to reduce the incidence of allograft fracture.
Pathologic fractures can also occur in children with metastatic disease but are less common than in adults. Furthermore, most are microfractures and can be successfully managed conservatively.
AUTHOR’S PREFERRED METHOD
For all suspicious lesions, careful staging and biopsy are the appropriate initial approach. Experience in the management of children with musculoskeletal sarcomas, and access to special diagnostic modalities, such as immunohistochemistry and cytogenetics, will decrease the chances of mismanagement and misdiagnosis. The decision for or against limb-sparing surgery in patients with pathologic fracture associated with a bone sarcoma should be individualized based on factors such as the fracture displacement, fracture stability, histologic and radiographic response to chemotherapy, and, most important, the ability to achieve wide margins for local tumor control. Pathologic fractures that occur after reconstruction through allograft or endoprosthetic reconstruction often can be successfully treated with bone grafting or exchange of allograft or endoprosthesis.
FD is a benign bone abnormality characterized by replacement of normal bone and marrow by fibrous–osseous tissue (woven bone formed by metaplasia with poorly oriented bone trabeculae) resulting in decrease of strength, deformity, and pathologic fracture. The disease may involve a single bone (monostotic FD) or several (poliostotic FD). When bone disease is associated with café-au-lait skin hyperpigmentation and endocrine dysfunction, it is referred as McCune–Albright syndrome.209
The diagnosis of FD is usually made between 5 and 15 years of age. Often, the lesions are asymptomatic and a pathologic fracture may be the presenting symptom. Fractures of long bones are generally minimally displaced or incomplete, many being microfractures and presenting with pain and swelling.171 The bones most commonly affected are the femur, tibia, humerus, radius, facial bones, pelvis, ribs, and phalanges. The sites of fracture in decreasing order of frequency are the proximal femur, tibia, ribs, and bones of the face. The age of first fracture, number of fractures, and fracture rate are related to the severity of the metabolic derangement. The endocrinopathies are often associated with phosphaturia that causes a rickets-type effect on the normal skeleton and is related to increased incidence of fractures.171 Although the fractures heal rapidly, endosteal callus is poorly formed and periosteal callus is normal. With mild deformity, the cortex thickens on the concave side of the long bone. Nonunion is rare in monostotic FD, but can occur in polyostotic disease. Spine involvement occurs with polyostotic FD, and limb-length discrepancy is common.121 In one series of 37 patients with polyostotic FD, nearly 85% had at least one fracture and 40% had an average of three fractures.121
On plain radiographs, FD is seen as well-defined, mostly lytic and central lesion, located in the metaphysis or diaphysis of long bones. The borders are commonly sclerotic and the metaplastic woven bone comprising the lesion creates the classic “ground-glass” appearance (Fig. 8-20). Bowing and/or angular deformity of tibia and femur are often seen. In distinguishing polyostotic from monostotic FD, skeletal surveys and sometimes technetium bone scans are recommended.
Conservative treatment with immobilization is indicated for most fractures that occur in conjunction with monostotic FD. Surgery is indicated for fractures through severely deformed long bones (especially in the lower extremities), and those through large cystic areas. Fractures in polyostotic disease often require more aggressive treatment.
Fractures of the femur can be treated conservatively in young patients, but after adolescence, recurrent deformity after surgery is less common, and curettage and grafting with internal fixation should be considered, especially for large lesions through deformed bones.121 Stephenson et al.258 found that in patients younger than 18 years of age, closed treatment or curettage and bone grafting alone of lower extremity fractures gave unsatisfactory results, but internal fixation produced more satisfactory outcomes.
Proximal femoral pathologic fractures are especially troublesome because of the propensity for malunion with coxa vara resembling a shepherd’s crook.71 For fractures through small lesions, either cast immobilization or curettage with grafting can be used100; for larger lesions, internal fixation is necessary. For severe shepherd’s crook deformity, medial displacement valgus osteotomies with internal fixation may be needed to restore the biomechanical stability of the hip. Both painful lesions without fracture and impending pathologic fractures can be treated with internal fixation. Spine fractures are rare but can be treated with bed rest followed by immobilization with an orthosis.114
The main challenge in bone grafting FD is the potential for resorption and transformation into FD. Autogenous cancellous graft has the higher likelihood to become FD, and cortical allograft is the least likely to be transformed.71 The use of bisphosphonates, primarily pamidronate, may offer hope for a medical treatment for patients with severe FD. Pamidronate is a second-generation bisphosphonate that has had documented success in selected patients with the disease. It is a potent inhibitor of bone resorption and has a lasting effect on bone turnover. The major effect is decreased bone pain. Improved bone density with pamidronate therapy has also been demonstrated.209
AUTHOR’S PREFERRED METHOD OF TREATMENT
Conservative treatment with immobilization is indicated for most fractures in children with monostotic FD, especially in the upper extremities. Because fractures in patients with polyostotic FD usually occur through very abnormal bone and can result in marked deformity, internal fixation is often needed.
Curettage and grafting are indicated for fractures through severely deformed long bones and those through large cystic areas, with appropriate internal fixation for the location and age. Bone graft is often reabsorbed and transformed into FD, allograft has a lower likelihood to be reabsorbed than autograft. Recently, the use of coral as bone substitute has been shown to be an alternative.71
For proximal femur pathologic fractures one must be vigilant and ready to intervene at any sign of varus deformity. Femoral neck fractures can be stabilized in situ with a cannulated screw or compression screw and side plate. Varus deformity is best treated with valgus osteotomy of the subtrochanteric region and internal fixation early in the course of the disease to restore the normal neck shaft angle and mechanical axis. Intramedullary load-sharing fixation is preferred for juvenile patients with femoral shaft fractures, total bone fixation is the ideal and second-generation intramedullary nails should be used when possible.
Osteofibrous dysplasia (OD) is a rare developmental tumor-like fibro-osseous condition. Most patients present before the age of 5 years, ranging from 0 to 15 years of age.47,216 Clinically, there is usually a painless enlargement of the tibia with slight to moderate anterior or anterolateral bowing. The disease process is almost always confined to one tibia, but the ipsilateral fibula can also be involved. Although distal and proximal lesions can occur, midshaft involvement is the most frequent. Pathologic fractures occur in approximately one-third of patients; but are usually incomplete (e.g., stress fractures, microfractures) or minimally displaced and heal well with conservative treatment.47 Pseudarthrosis is rare but sometimes delayed union may be a problem.
OD presents as a well-defined, eccentric, intracortical, lytic lesion usually located in the middle third of the tibia, extending proximally or distally.216 The cortex overlying the lesion is expanded and thinned, and in the medullary canal, a dense band of sclerosis borders the lesion with narrowing of the medullary canal. Single areas of radiolucency may be present and have a ground-glass appearance, but often there are several areas of involvement with a bubble-like appearance (Fig. 8-21). Intralesional curettage and grafting lead to local recurrence in over 60% of the cases.47 Wide extraperiosteal resection can be performed for aggressive lesions and present with lower rate of recurrence.168 Some authors6,155 recommend bracing until skeletal maturity.