Background and oncological impact of intraoperative joint fluid leakage during extra-articular osteosarcoma resection.

In case of sarcomas with intra-articular extension, extra-articular resection (EAR) provides good local control. However, during EAR, the joint capsule may be injured by error, causing tumoral joint fluid leakage, but its impact on oncological outcomes is still unrevealed. We here call these procedures as 'inadequate EAR' and retrospectively investigated the impact in 36 osteosarcoma patients. The affected joints included the knee (27 cases), hip (5), shoulder (3), and wrist (1). Responses of preoperative chemotherapy as 'controlled' or 'progressive' and surgical margins were also assessed. Among the patients, nine (25%) had inadequate EAR. Responses of preoperative chemotherapy were controlled in 23 cases and progressive in 13 cases. Surgical margins were wide in 31 cases and marginal in 5. The 5-year local control rates were 95.5% and 75% for adequate and inadequate EAR, respectively (p = 0.0488). The inadequate EAR group showed a significantly worse response rate of chemotherapy (p = 0.0459) and a trend towards insufficient surgical margins (p = 0.0876). Cox regression analysis indicated that inadequate EAR was associated with a higher hazard ratio (HR) of 6.81 (p = 0.13), whereas the HR for surgical margins was 1.56 (p = 0.74). Poor response to preoperative chemotherapy increases the likelihood of inadequate EAR and may compromise local control.