Chondroblastoma is a rare benign bone tumor that typically arise during the teenage years with a very wide range of age[2, 8]. It usually affects the epiphyses or apophyses of long bones such as humerus, femur and tibia. Less common location affected by chondroblastoma including patella, calcaneus, acetabulum and even spine, also had been reported in literature[9–11].It seems that chondroblastoma occurs more frequently in males than in females, in a ratio of 2.3 to 1[2, 12]. In this group of patients, the mean age of onset was 13 years old with a male to female ratio of 1.5:1, and also the proximal humerus was the mostly involved location, which all coincided with most previous studies.
The clinical manifestation of chondroblastoma is not typical and it is difficult to make an accurate clinical diagnosis before the final pathological result[4, 13]. All these 15 patients had chief compliant of a mild to moderate pain. Seven patients had limited joint motion, among which 5 were caused by pain and 2 were caused by the local joint swelling. However, these two common symptoms were not specific for the diagnosis of the disease, because most bone tumors could present in the same way. The typical imaging findings included a round-like focus located in epiphysis with a clear boundary, and a significantly higher-intensity signal on T2-weighted MRI. These characteristic imaging features and lesion locations were very helpful for the preoperative diagnosis. However, there were still 8 patients undiagnosed or misdiagnosed, only 7 patients with a consideration of chondroblastoma preoperatively in this group of patients.
Surgical removal of the lesion and bone grafting in a large defect is the standard treatment for chondroblastoma[1, 15]. For completely curettage of tumor and avoid recurrence, most authors advised adjuvant physical or chemical inactivation methods, including high-speed burr, electrocauterization, phenol, cryotherapy and ethanol[5, 16]. High-speed burr, phenol and ethanol were more widely reported in the previous studies. However, there is still no study on the comparison of the different adjuvant options, and point out the optimal choice. Moreover, these adjuvant therapies may cause an extensive tissue damage while killing tumor cells, and should be used carefully, especially for tumors involving the epiphyseal plate.
Due to the typical chondroblastoma location in epiphyses, there was always a concern about the physeal plate injury of patients with persistent epiphysis, which might cause growth disturbance. While, it seems that a completely extended lesions curettage is more important than protection of the epiphyseal plate to avoid local recurrence. Mashhour and Abdel Rahman preferred aggressive surgical treatment at the time of the first surgery to prevent recurrence, because re-operation after recurrence might cause more damage on growth plate. In this group of patients, complications of upper limb shortening occurred on 2 patients, who both had persistent epiphysis with lesions extended through the epiphyseal plate. Because the shorting were within 2 cm and occurred on humerus, there were no obvious effect on function and appearance. However, varus or valgus deformity of knee joint and lower limb shorting deformity still had been reported in some previous studies, which might influence the functional outcome and need a further treatment.
Cortical defect and fracture had been reported before when chondroblastoma affected the articular surface,and there might be a complication of arthritis in long term follow up. In this study, focal articular surface destruction of the femoral head was involved in 1 patient who received an operation of intralesional curettage and electrocauterization through the hip joint approach, without bone grafting or cementing. This patient gained a normal hip function, with no tumour recurrence, no femoral head necrosis or arthritis observed during 10 years follow up(Fig. 3). Treatment of femoral head chondroblastoma can be extremely challenging. Surgical approaches include direct hip joint approach and indirect way from the lateral femur to femur head via a subtrochanteric drill hole. Laitinen MK also preferred the direct hip joint approach to treat femur head lesion without grafting. In their study, results of femoral head chondroblastoma treated in a direct hip joint approach were better with no local recurrence or femoral head collapse occurred, when compared to the indirect surgical approach.
The prognosis of chondroblastoma generally is good, while it is still an aggressive tumor, with risk of local recurrence and extremely rare metastasis. Location, age and persist epiphysis once were considered a possible risk factor for recurrence, while most authors thought inadequate curettage was the most significant risk factor associated with local recurrence. In our study, all patients gained good functional outcome with a mean postoperative MSTS score of 28.1 points at 10 years follow up. The overall recurrence rate was 6.7% (1/15), which was within the wide range of recurrence rate reported in the literature[4, 6, 7].
The limitations of our study were that it was a retrospective study in a single center, and it was in a small sample size with no control. There still need more further studies of large sample, muti-centre clinical trials, especially in the adjuvant treatment and risk factors of local recurrence.