JAAOS - 2026-06-15 - Journal Article
Association of Cartilage Cap Thickness With Tumor Grade and Outcomes in Secondary Chondrosarcoma.
Hirase T, Lavery JA, Gertzulin M, Viola DCM, Hwang S, Rizzo A, Morris CD
Topics
Key Takeaway
In secondary chondrosarcoma arising from osteochondroma, mean cartilage cap thickness was 35 mm in grade 1 versus 76 mm in grade 2/3 disease (p<0.001), but CCT did not predict overall survival, local recurrence, or distant recurrence.
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Summary
This study asked whether cartilage cap thickness (CCT), measured on T2-weighted MRI or gross specimen, correlates with histologic grade and oncologic outcomes in biopsy-proven secondary chondrosarcoma. CCT was significantly greater in grade 2/3 tumors (mean 76 mm) versus grade 1 (mean 35 mm), with an OR of 1.11 per mm increase for high-grade disease (95% CI 1.05–1.21, p<0.001). Despite this grade association, CCT showed no statistically significant relationship with overall survival, local recurrence, distant recurrence, or margin positivity.
Key Limitation
The small sample size (n=45, only 15 high-grade cases) at a single institution over 23 years severely limits power to detect true associations between CCT and oncologic outcomes, risking type II error for the survival and recurrence analyses.
Original Abstract
INTRODUCTION
Although increased cartilage cap thickness (CCT) is associated with secondary chondrosarcoma in patients with osteochondroma, no studies have assessed its relationship with histologic grade or outcomes after primary resection. Thus, the objectives of this study were to determine whether CCT is associated with (1) histologic grade in secondary chondrosarcoma and (2) oncologic outcomes after primary resection of secondary chondrosarcoma.
METHODS
Patients who had a history of osteochondroma and were diagnosed with a biopsy-proven secondary chondrosarcoma at a single institution between January 2000 and December 2023 were included. CCT was measured on T2-weighted imaging or through direct measurement of the resected gross specimen. The primary outcome measure was of histologic grade. Secondary outcome measures were overall survival, local recurrence, distant recurrence, and margin positivity. Grade and margin positivity were evaluated using logistic regression models; time-to-event outcomes were assessed using Kaplan-Meier and cumulative incidence methods and Cox models.
RESULTS
Forty-five patients (30 male; median age, 39 years) were included. Thirty (67%) had grade 1 secondary chondrosarcoma, 12 (27%) had grade 2, and 3 (6.7%) had grade 3. Mean CCT was smaller in grade 1 chondrosarcoma (35 mm; SD, 18 mm) than in grade 2 or 3 disease (76 mm; SD, 30 mm; P < 0.001). Thicker cartilage cap was associated with increased odds of high (grade 2 or 3) versus low histologic grade (odds ratio, 1.11; 95% confidence interval, 1.05 to 1.21; P < 0.001). No statistically significant associations were observed between CCT and overall survival, local recurrence, distant recurrence, or margin positivity.
CONCLUSIONS
Although CCT may be a useful diagnostic marker for secondary chondrosarcoma, thickness itself is not a reliable prognostic marker for predicting long-term patient outcomes. However, its positive association with tumor grade may have implications for surgical planning.
TYPE OF STUDY
Diagnostic Study.
LEVEL OF EVIDENCE
III.