Approach Considerations
No evidence suggests that chondroblastoma resolves spontaneously; accordingly, surgical treatment is generally indicated.
Percutaneous radiofrequency ablation (RFA) may be an alternative to surgery for the treatment of certain chondroblastomas, [25] but according to Rybak et al, larger lesions that are under weightbearing surfaces should be approached with caution because of an increased risk of articular collapse and recurrence. [26]
Medical Therapy
Radiation therapy has been employed in the treatment of chondroblastoma but has essentially no current role in its treatment. [27, 25]
Chemotherapy has not been reported in the condition's treatment.
In search of a targeted therapy for patients with disseminated chondroblastoma or those in need of medical management, Yang et al reported positive effects of targeted inhibition of mTOR (mammalian target of rapamycin) and HIF (hypoxia-inducible factor) pathways in benchtop work with chondroblastoma. Combination treatment of low-dose rapamycin, FM19G11, and leucine deprivation were inhibitory on the chondroblastoma cell line examined. [28]
A study by Suster et al demonstrated that chondroblastomas, along with other giant cell–rich bone lesions, expressed receptor activator of nuclear factor-κB ligand (RANKL). [29] This finding suggested that chondroblastomas might potentially be treatable with RANKL inhibitors such as denosumab, which has previously shown success with giant cell tumors of bone.
Pain medications should be administered as needed.
Surgical Therapy
The most common surgical procedure used for chondroblastoma is curettage, with or without autograft or allograft bone grafting. [30, 31, 32] Other options, used less frequently, include the following:
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Substitution of polymethylmethacrylate (PMMA) or fat implantation for bone graft
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Chemical cauterization (with phenol) of the curetted lesion
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Liquid nitrogen cryotherapy
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Marginal resection
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Wide resection
Large or recurrent chondroblastomas should be managed by an orthopedic oncologist.
Surgical curettage vs radiofrequency ablation
Although open surgical curettage remains the most commonly used treatment, an emerging pool of literature continues to support the safety and efficacy of treatment with RFA.
Studies of longer-term follow-up after conventional curettage and grafting have generally reported excellent results with a low complication rate. At a mean 8-year follow-up of 24 patients treated by curettage and bone grafting, a recurrence rate of only 4% (1/24) was reported by Lehner et al, and 88% of patients achieved good or excellent results. [33] In a report of 14 patients using extended intralesional curettage with high-speed burring, intralesional cryotherapy, and autogenous bone grafting, Mashhour et al noted that the recurrence rate was low (1/14) after mean 4-year follow-up, but two patients experienced growth arrest. [34]
For balance, however, in a large series of 87 purely pediatric chondroblastoma cases, the recurrence rate after curettage and grafting was 32%. [35] Risk factors for recurrence included epiphyseal location (contrasted with metaphyseal, apophyseal, and combined metaphyseal-epiphyseal), proximal femoral lesions, and tarsal lesions. In 63% of the patients, treatment consisted of intralesional curettage with autogenous bone grafting; functional outcome was good for 68.5% of the patients; and 32% of the lesions recurred. [6]
The difficulty of treating femoral head lesions led two authors to publish papers examining that site in particular. In a series of 10 patients with femoral head lesions, a direct approach to the lesion through the femoral neck was favored over curettage through a drill hole within the femoral neck. [36] A trap-door technique was also reported as a successful salvage technique in that series. For a large femoral head defect, a vascularized fibular graft was successfully used to reconstruct the defect created by open surgical treatment. [37]
RFA for chondroblastoma has been described in several reports, but follow-up has been shorter than for surgery, and caution is recommended when the lesions are larger than 2.5 cm and when there is no subchondral bone support. Nevertheless, proponents favor RFA for smaller lesions with intact subchondral bone and difficult-to-access lesions. [38] However, many reports have included fewer than 10 patients, follow-up has been shorter than that for conventional curettage and grafting, and complications have been reported in as many as 20%. [39, 40] Complications of RFA for chondroblastoma have included subchondral fracture, chondrolysis, persistent pain, and need for repeat RFA.
In a study of RFA for chondroblastoma by Rybak et al, [26] 12 of 14 patients available for follow-up (median, 41 months) reported complete relief of symptoms without the need for medications, and all returned to previous activities. One patient, who had the largest lesion, required surgery because of articular collapse in the area of treatment; another required surgical treatment because of mechanical problems. The authors concluded that percutaneous RFA is an alternative to surgery for selected chondroblastomas but that larger lesions under weightbearing surfaces must be approached with caution because of an increased risk of articular collapse and recurrence.
Xie et al carried out a retrospective study of 25 consecutive patients treated with RFA over a period of approximately 7 years. [41] Patients were assessed after 1 month, then every 3-6 months, and then yearly for up to 3 years. Recovery was monitored with serial magnetic resonance imaging (MRI), and functional outcome was quantified with the Musculoskeletal Tumour Society Score (MSTS). The authors found RFA to an effective alternative to surgery in the management of chondroblastoma and suggested that it should be considered as a first-line treatment.
Complications
In addition to recurrence, many complications can occur after treatment of chondroblastomas, including the following:
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Infection
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Development of degenerative joint changes
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Fracture through the lesion
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Failure of osteoarticular allografts, if used
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Premature physeal closure and subsequent limb-length discrepancy or angular deformity of the limb
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Malignant transformation or development of a postradiation sarcoma as late as 18 years after diagnosis (in rare cases in which radiation therapy is used)
Activity
Unless the lesion is particularly large and creates a risk of pathologic fracture, patients may participate in activity as tolerated. If an en-bloc excision is performed, the patient's activity may be limited to protect the reconstruction.
Long-Term Monitoring
In view of the 10% risk of local recurrence, patients should be monitored for at least several years. Monitor patients with open physes at the time of treatment for premature physeal closure.
At follow-up, patients should be evaluated with a thorough history and physical examination and with appropriate radiographs.
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Radiograph of epiphyseal lesion (hip).
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Radiograph demonstrating tumor on both sides of physis (humerus).
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Bone scan.
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Magnetic resonance image of a hip showing lobular pattern of chondroblastoma.
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Histology of chondroblastoma.
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Chondroblastoma histology demonstrating chicken-wire calcifications.
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Axial computed tomography scan of the pelvis demonstrates a lesion of the femoral head without noticeable internal matrix production. The epiphyseal location of the lesion is a clue to the correct diagnosis.
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Plain film of the hip shows a femoral head with a lytic lesion with surrounding sclerosis in the epiphysis of the proximal femur. Internal matrix formation is not present, but that finding can be a feature of this tumor.
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Coronal T1-weighted sequence shows a lesion of the epiphysis with medium signal intensity. Small islands of matrix are noted.
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Low-power photomicrograph demonstrates islands of hyaline-type cartilage, which can often be seen in chondroblastomas.
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Medium-power photomicrograph with lobules of chondroid matrix. In these lesions, the cartilage can be eosinophilic, with superficial resemblance to osseous matrix. Correlation with the radiologic studies is often helpful when in doubt.
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Medium-power photomicrograph demonstrates secondary cystic changes, which can often accompany chondroblastomas. Careful sampling of the tumor will show the correct etiology for the changes noted here.
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Giant cells are a component of this tumor, and in areas that are rich in giant cells, sampling will show the chondroblastomatous portions of the tumor.
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Immunohistochemistry for S100 is positive in chondroblastomas and is often helpful, especially when the tissue sample is small.
