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Abstract

Introduction: Chondroblastoma (CBL) is a rare benign bone tumor with potentially local recurrence and metastases. At present, the local recurrence risk factors are controversial. The purpose of this study is to analysis local recurrence factors in our medical center. Methodology: A retrospective analysis was conducted on 18 male and 10 female patients who presented at our hospital between 2016 and 2023. The clinical data included radiological images, histological results, treatment modalities, functional outcomes, and local recurrence rates. Surgical interventions comprised curettage, followed by bone grafting and adjunctive techniques. Furthermore, all patients were stratified into two groups based on tumor volume, with a threshold of 25 cm³, to explore the relationship between tumor volume and recurrence. Results: Among the 28 patients, with an average age of 13 years (range: 9 to 16 years) and an average follow-up duration of 33 months (range: 8 to 91 months). The mean Musculoskeletal Tumor Society (MSTS) score was 27 points (range: 14 to 30). Notably, recurrence was observed in 3 pediatric patients. A statistically significant difference in recurrence rates was found between tumors with volumes less than 25 cm³ and those greater than 25 cm³ (p < .05). Conclusion: Curettage, combined with alcohol as an adjuvant, resulted in local control and good outcomes in most pediatric patients. It was noteworthy that a larger tumor size correlated with an increased likelihood of recurrence.

Keywords

chondroblastoma local recurrence treatment tumor

Introduction

Chondroblastoma (CBL) is defined as a benign bone tumor with potentially aggressive local growth and pulmonary metastases. Kolodny was the first person to recognized it¹ and Codman used the term “epiphyseal chondromatous giant cell tumour” to described it.² Jaffe and Lichtenstein found that it originated from chondroblasts.³ Thus, it was termed benign chondroblastic neoplasm. CBL often occurs in the second decade of male life, and the metaphysis of long bones is its common site.⁴

At present, the gold standard treatment for chondroblasts has not been put forward. Curettage, either alone or in combination with bone grafting or packing the cavity with polymethylmethacrylate, or coupled with cryosurgery,⁵ radiofrequency ablation^4,6,7 has been reported. However, the treatment of chondroblastoma is decided by the patient.

The prevailing viewpoint currently holds that the recurrence of CBL is associated with factors such as age at onset, gender, the presence of aneurysmal bone cyst (ABC), tumor location, status of the physeal plate at the lesion site, involvement of the physeal plate by the lesion, and the mode of treatment.^4,8,9 To date, no reports have been published regarding the correlation between CBL tumor volume and recurrence. The aim of this study is to investigate whether larger tumor volume increases the risk of recurrence in CBL and to validate the previously proposed recurrence factors.

Methodology

The retrospective study was conducted at a single center to identify all patients with histologically confirmed chondroblastoma who underwent treatment between 2012 and 2023. All patients initially underwent curettage as the primary surgical intervention. The surgical techniques employed were curettage, with or without subsequent bone grafting.

Patients who were not followed up regularly or lost to follow-up were excluded. Additionally, patients who did not receive their initial treatment at our center were not included. Furthermore, patients with incomplete clinical progress notes were not accepted. Lastly, patients with a history of other orthopedic diseases were also excluded.

By examining the hospital medical records, we successfully gathered information on patient characteristics including age at diagnosis, gender, affected side, tumor location, tumor volume, epiphyseal plate status, involvement of the epiphyseal plate, presence of aneurysmal bone cyst, surgical treatment details, and recurrence status. Tumor volume was measured based on preoperative CT scans by calculating the product of the maximum diameters in the coronal, sagittal, and axial planes and dividing by 2. The adjacent epiphyseal plate status was assessed via X-ray and classified into three categories: open, closing, and closed. Specifically, an open epiphyseal plate was characterized by a wide and clear appearance on X-ray, a closing plate exhibited a narrow and curved appearance, and a closed plate was identified by the presence of an epiphyseal scar, as described in previous studies.^8,10,11 Recurrence was defined as an increase in the low-density shadow observed on postoperative follow-up X-ray films compared to previous films, and this diagnosis was confirmed as CBL through reoperation biopsy. Postoperative function was evaluated using the Musculoskeletal Tumor Society (MSTS) score.12

Statistical analysis

Local recurrence-free survival (LRFS) was presented using Kaplan-Meier method. Differences of LRFS was determined using the log-rank test. Differences between means and proportions were tested with the Fisher’s exact test for categorical variables and the unpaired t-test for continuous variables. Intraclass Correlation Coefficient (ICC) and Kappa coefficients are utilized to assess inter-rater differences in continuous and categorical variables among various researchers. A probability value of p ≤ .05 was considered statistically significant.

Results

In our retrospective study, 28 patients (18 males and 10 females) were included. The male-to-female ratio was approximately 1.8:1. The most commonly affected sites were the distal femur (32.1%), followed by the proximal tibia and femoral head (25.0%), femoral neck (7.1%), proximal humerus (3.6%), ischium (3.6%), and distal fibula (3.6%). The mean follow-up time was 33 months (range: 8 to 91 months). The epiphyseal plate status was closing in 11 patients and closed in 17 (Table 1). The main symptom was pain (85.7%), accompanied by limping in 33.3% of patients. The median duration of symptoms was 6 months (range: 0.2 to 48 months). All patients underwent curettage procedures with adjunctive use of anhydrous alcohol. Specifically, 17 patients (60.7%) received artificial bone grafting, 5 (17.9%) received allograft bone grafts, 4 (14.3%) did not receive any bone grafting, 1 (3.6%) underwent mixed bone grafting, and 1 patient received autogenous bone grafting. Postoperatively, patients were encouraged to initiate movement on the second day and gradually commence partial weight-bearing 6 weeks postoperatively, followed by full weight-bearing 3 months after surgery. Three patients developed local recurrence (LR) with a mean time to recurrence of 9 months (range: 3 to 12 months). The LR rate was 10.3%, and all recurrences occurred within 2 years postsurgery. The mean volume of LR chondroblastoma was 42.00 cm³ (range: 24.76 to 65.38 cm³), significantly greater than that of non-recurrence patients (10.37 cm³; range: 0.69 to 88.19 cm³; p < .05). Only 3 non-recurrence patients had lesion volumes larger than 25 cm³. One patient presented with a pathological fracture in the femoral neck 3 months after surgery, and the lesion volume was 26.23 cm³. Two boys developed sinuses at six and 8 weeks postoperatively, respectively. The mean MSTS score was 27 (range: 14 to 30), indicating good postoperative outcomes. Only one patient had an MSTS score below 25 (14 points), with poor walking ability and development of limb-length discrepancy (LLD) and knee varus after proximal tibia chondroblastoma curettage and artificial bone grafting. The kappa coefficient for observer agreement on epiphyseal plate status was 0.85 (p < .05), indicating strong reliability. Similarly, the intraclass correlation coefficient (ICC) for focus volume was high at 0.92, suggesting good correlation between different observers.

Table 1.

Baseline characteristics of chondroblastoma patients.

	Chondroblastoma patients
Age at diagnosis
9 years	1
10 years	2
11 years	2
12 years	4
13 years	4
14 years	8
15 years	5
16 years	2
Gender
Male	18
Female	10
Side
Left	15
Right	13
Location
Proximal femur	1
Ischium	1
Femoral head	7
Femoral neck	2
Distal femur	9
Proximal tibia	7
Distal fibula	1
Lower than 25 mm³	22
Epiphyseal plate status
Closing	11
Closed	17
Affected the epiphyseal plate
Yes	23
No	5
With aneurysmal bone cyst
Yes	2
No	26
Total	28

In the updated analysis, patients were categorized into two distinct groups based on tumor volume: one group with volumes less than 25 cm³ and another with volumes greater than or equal to 25 cm³. Statistically significant differences were observed between recurrence and both tumor volume (categorized as <25 cm³ vs ≥25 cm³, p < .05). The Kaplan-Meier survival analysis indicated that all recurrences occurred within 2 years following surgery. (Figure 1). The Kaplan-Meier curves indicated that tumors larger than 25 cm³ were associated with a higher risk of local recurrence in chondroblastoma patients (log-rank p < .05).

Figure 1.

Kaplan-Meier survival curve showing the risk of local recurrence for chondroblastoma. All local recurrences arose within 48 months of initial treatment.

Discussion

Chondroblastoma, traditionally defined as a benign tumor, exhibits potential for local recurrence and metastasis. The local recurrence rate following lesion curettage ranges from 0% to 39%.^{4,8,9,13–19} Risk factors for tumor recurrence remain controversial, with age, gender, the presence of ABC, tumor aggressiveness, location, epiphyseal plate status, affected epiphyseal plate, and therapy method among those considered.^4,6,7

Age at diagnosis has been identified as a significant risk factor for local recurrence, with younger patients generally facing a higher risk. Cong Huang et al. observed that all recurrent cases occurred in patients younger than 12 years, with all patients in their study being under 14 years old, similar to our cohort.⁹ R. Suneja et al. also noted that six of seven local recurrence patients were under 14 years old, suggesting an association with younger age.⁵ Francesco Muratori et al. found that age less than 11 years was the only significant factor influencing local recurrence risk among patients aged 7 to 42 years.¹¹ Surgeons treating young patients with chondroblastoma often exercise particular caution to minimize bilateral lower limb asymmetry following surgery, potentially leading to incomplete removal of the tumor at the epiphyseal plate. The misdiagnosis of chondroblastoma is common, despite rapid diagnosis in cases with classical features. Confusion with giant cell bone tumor (GCT) or ABC may lead to overlapping clinical presentations.¹⁹ Local pain is the most common symptom, lasting over a year in some cases, while a minority of patients remain asymptomatic, delaying diagnosis.^4,17,19 Unexpectedly, all recurrent patients in our study were older than 11 years. This finding may be due to the small sample size of patients under 11 years old in our group and the difficulty in determining the asymptomatic incubation period prior to symptom onset. Only one previous study reported similar findings, suggesting that advanced age may be a risk factor for recurrence.¹⁷

In this study, we explored the relationship between tumor volume and local recurrence, finding that larger tumor volumes were associated with a greater risk of local recurrence (p < .05). In the updated analyses, volume over 25 cm³ was associated with a statistically significant increase in local recurrence. In the context of other tumors, a larger tumor volume was generally regarded as being associated with a higher likelihood of recurrence.^20,21 To our knowledge, Laitinen et al. have mentioned that CBL located in the greater trochanter tends to be larger compared to it in the femoral head; however, they did not explicitly point out any differences in recurrence rates between the two locations.¹⁷ On the one hand, when surgeons tackled large tumors, they were worried that, in comparison to smaller tumors, patients were at a heightened risk of developing limb-length discrepancy (LLD) following extensive curettage of the epiphyseal plate.^4,9,22 Notably, 82.1% of our patients’ epiphyseal plates were affected, with only a single case of a patient with a closing plate experiencing postoperative LLD and knee varus. It was postulated that with meticulous care, the epiphyseal plate could potentially undergo repair.^5,9 Lin et al. reported that an open growth plate in chondroblastoma surgery was not found to correlate with local recurrence. Furthermore, in most cases, they observed that the open epiphysis plate did not considerably impact bone growth.²³ Liu et al. similarly proposed a possible reason for this observation: the epiphyseal plates at the distal femur and proximal tibia are typically large. Consequently, only a small portion of these plates is involved with the tumor, exerting minimal influence on long bone growth.¹⁸ Additionally, some literatures have suggested that postoperative growth complications are generally attributed to tumor-induced damage to the growth plate, rather than being a direct consequence of the surgical procedure itself.^18,24 Prior investigation has established a correlation between the extent of the injured epiphyseal plate and the resistance of long bones to normal growth and development.²⁵ On the contrary, the damage to the epiphyseal plate was considered to be irreversible in a few studies.²⁶ We believe that there is potential for spontaneous repair of the epiphyseal plate, as most patients with tumor-injured epiphyseal plates did not develop LLD, with only one exception. Meanwhile, waiting until the growth plate closes before surgery may be appropriate, particularly in asymptomatic cases, where careful observation while awaiting surgery is indicated.

On the other hand, the tissue of chondroblastoma was soft and poorly interconnected, leading to the leakage of numerous granular-like tumor tissues during the scraping of larger tumor masses. This leakage prevented complete removal and subsequently resulted in recurrence. To address this issue, we employed alcohol immersion for 3–5 minutes to enhance the brittleness of the tumor tissue, facilitating both inactivation and scraping. Anhydrous ethanol can cause protein denaturation in tumor cells, cytoplasm denaturation in cells, and embolization of small blood vessels supplying the tumor. Additionally, anhydrous alcohol has been proven to have a few adverse effects on surrounding tissues.²⁷ Concurrently, the application of alcohol to the sclerosed zone surrounding the tumor was advantageous in facilitating the infiltration of progenitor cells into the cavity, thus contributing to the repair of the cavity.

CBL has been proved to be common in distal femur, proximal tibia and proximal humerus, although our results only partially concurred with this observation. In this study, CBL mainly occurred in proximal humerus, distal humerus and proximal tibia. There were few researches that reported that special anatomic site, such as pelvis.¹⁵ The reason why CBL in pelvis was easy to recur was believed that its anatomical position made it difficult to completely expose the tumor and incomplete curettage leaded to recurrence. In this study, there was a patient whose CBL was located in the pelvis. After adequate curettage, the patient has no signs of recurrence at present. Frédéric Sailhan et al. found that CBL far away from the active epiphysis (close to the elbow or far from the knee) has a higher recurrence rate among their patients,¹³ which was completely contrary to our results. The CBL of our recurrent patients were located in the proximal humerus, distal femur and proximal tibia respectively. Our study found no significant correlation between the location of CBL and local recurrence.

In our center, the main treatment methods of CBL were curettage, assisted by anhydrous alcohol as adjuvant and bone grafting. Alcohol as adjuvant was considered had a good effect of inhibiting tumor recurrence. Tumors located in the proximal femur and pelvis were reported to be susceptible to recurrence because they were difficult to achieve complete surgical resection.^4,5,23 Therefore, it is necessary to use adjuvants. High-speed burring and it has been proved that it could obviously reduce local recurrence in CBL curettage.^28,29 However, Cong Huang et al. expressed concerns that the epiphyseal plate might sustain damage from the heat generated by the burr during the procedure.⁹ Cement was also deemed potentially harmful to the epiphyseal plate due to the heat released during its solidification process.¹⁹ Furthermore, the use of other adjuvants, such as phenol or liquid nitrogen, could potentially lead to necrosis.¹⁵ Alcohol has been proved to have a good effect on inactivating tumor cells and has little effect on surrounding tissues.²⁷ But there were few researches using alcohol alone as the adjuvant to treat the CBL. The results of a study evaluating the effect of local adjuvants after curettage of benign tumors showed that curettage combined with burr could significantly reduce the risk of recurrence after CBL curettage compared to other adjuvants.³⁰ However, it must be noted that the number of cases excluding burr as an adjuvant in the treatment combination was extremely limited. Among the various complications observed, ethanol used alone as an adjuvant resulted in only one case of postoperative fracture and one case of superficial infection. In other situations, ethanol was mainly used as a wash for phenol.³⁰

Previous studies have suggested that ABC was a risk factor for CBL local recurrence.⁸ Whether ABC was the recurrence factor of CBL has always been controversial, and there were also a large number of documents showing that ABC was not related to the recurrence of CBL.^13,31 According to our results, there was no significant difference between ABC and local recurrence and only 2 patients CBL with ABC, which located in ischium and distal femur respectively and both of them were not developed local recurrence.

Among patients who underwent curettage and artificial bone grafting, three patients developed femoral neck fracture, gluteal sinus tract, and upper limb sinus tract respectively. The bone graft substitutes that were used included calcium phosphate (CaP) and calcium sulfate (CaS) compounds. Generally, the main benefit of CaP ceramics stemmed from their osteoconductive properties, and they could provide some structural support in the form of compression strength.³² However, they were brittle and their low tensile strength may have contributed to increased postoperative fracture risks.³² Additionally, CaS compounds were believed to be associated with persistent serous wound drainage, which resulted from the inflammatory response to their resorption.³³ In most cases, this was a sterile drainage that persisted until the calcium sulfate was radiologically absorbed.³³ With proper local wound care, the wounds of two patients with sinus tracts recovered smoothly.

The primary limitation of this study lies in the rarity of the tumor and the relatively small sample size. Additionally, the average follow-up duration was insufficient to adequately assess complications such as secondary osteoarthritis. Furthermore, the retrospective nature of this study may undermine the robustness of our findings. Moreover, this study did not incorporate comparisons with other surgical interventions, such as radiofrequency ablation, to evaluate their impact on recurrence rates.

Conclusions

In conclusion, although CBL is classified as a benign tumor, there is still a risk of local recurrence. Larger tumors might increase the possibility of local recurrence of CBL in patients. Complete curettage, combined with alcohol, has achieved good results in the treatment of this disease. It also has the potential to reduce the damage to surrounding normal tissues caused by the adjuvant.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical statement

ORCID iD

Zhongliang Wang

Data availability statement

The datasets generated and analysed during the current study are not publicly available due personal privacy but are available from the corresponding author on reasonable request.*

Appendix

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Chondroblastoma in 28 cases: The risk of local recurrence increases with larger tumor size

Abstract

Keywords

Introduction

Methodology

Statistical analysis

Results

Discussion

Conclusions

Footnotes

Declaration of conflicting interests

Funding

Ethical statement

ORCID iD

Data availability statement

Appendix

References