Resection margins obtained with patient-specific instruments for resecting primary pelvic bone sarcomas: A case-control study.

BACKGROUND: Limb salvage surgery for pelvic bone sarcoma carries a very high risk of local recurrence. Patient-specific instruments (PSIs) have shown promise for obtaining tumour-free resection margins. However, no data are available on medium-term outcomes including local recurrence rates after PSI-guided resection. The objectives of this case-control study were to determine whether PSI-guided resection: 1) was associated with a lower local recurrence rate, 2) allowed a shorter operative time, 3) was associated with better-quality allograft reconstruction.

HYPOTHESIS: PSI-guided resection decreases the local recurrence rate by improving the resection margins in patients with primary pelvic bone sarcomas.

PATIENTS AND METHODS: PSI-guided resection was performed in 9 consecutive patients (cases) with primary pelvic sarcomas (chondrosarcoma, n=3; Ewing's sarcoma, n=3; osteosarcoma, n=1; fibrosarcoma, n=1; and radiation-induced sarcoma, n=1). Age ranged from 11 to 63 years. Outcomes were compared to those in a historical control group of 19 patients with primary bone sarcomas who underwent resection surgery in the same hospital without PSI guidance. The case and control groups were similar regarding age, sex distribution, and follow-up duration. The local recurrence rate and operative time were compared between the two groups. Resection margins were classified as R0, R1, or R2. The quality of allograft reconstruction, which was performed in 7 of the 9 cases, was assessed.

RESULTS: After a mean follow-up of 52 months (range, 30-90 months), none of the cases had experienced local bone or soft-tissue recurrences, compared to 7 of the 19 controls (p=0.03), in whom mean follow-up was 62 months (range, 24-134 months). Bone resection margins were R0 in 8 cases; in the remaining patient, R1 resection was performed deliberately to preserve an S1 root. All 9 cases had R0 soft-tissue resection margins. In the control group, bone resection margins were R0 in 13 patients, R1 in 5 patients, and R2 in 1 patient (p=0.47). Mean operative time was similar in the cases (612 minutes [range, 435-854 minutes]) and controls (633 minutes [range, 420-990 minutes]) (p=0.87). In the 7 patients who underwent pelvic allograft reconstruction, allograft contact in the defect and osteosynthesis stability were deemed satisfactory by the surgeon.

DISCUSSION: The lower local recurrence rate in the cases demonstrates that the improved resection accuracy provided by PSIs directly influences the risk of local recurrence. In addition, the R0 bone margins in 8 cases establishes that PSIs are effective in improving resection accuracy.

LEVEL OF EVIDENCE: III, case-control study.