(P 273) 3D-PRINTED PATIENT-SPECIFIC CUTTING GUIDES VERSUS FREEHAND RESECTION FOR INTERNAL HEMIPELVECTOMY: CLINICAL AND ONCOLOGIC OUTCOMES

Objective: Wide margin resection via internal hemipelvectomy remains the gold standard of limb-salvage curative-intent treatment for pelvic sarcomas. Due to the complex three-dimensional (3D) anatomy around the posterior pelvis and sacroiliac (SI) joint and the proximity to critical neurovascular structures, internal hemipelvectomy is among the most difficult and technical procedures in musculoskeletal oncology. Advancements in 3D technology have led to patient-specific cutting guides that may better achieve negative margins through more accurate and precise cuts, reduce overall surgical times, minimize complications, and prove more cost-effective than other modalities. However, despite its promise, there is no consensus supporting their routine use for internal hemipelvectomy.

This study sought to control-match a cohort of patients undergoing pelvic and sacral resection for osseous sarcoma with the freehand method to those in whom a 3D-printed cutting guide was used. It evaluated and assessed functional and oncologic outcomes of patients in either group, while also comparing the perioperative complication profiles between each of the two groups in an attempt to determine the efficacy of 3D-printed patient-specific cutting guides for use in orthopedic oncology.

Methods: Institutional Review Board approval was obtained to retrospectively review a prospectively maintained surgical database over a consecutive 20-year period. Inclusion criteria were patients with primary or secondary bone sarcoma of the pelvis (with or without sacral invasion) who underwent resection using a 3D-printed, patient-specific cutting guide or freehand technique (Figure 1). A cohort of patients who underwent internal hemipelvectomy using the freehand technique were then control-matched using the hemipelvectomy resection type. Secondary matching criteria included the primary histopathological diagnosis, tumor size, and individual surgeon’s experience with internal hemipelvectomy. A two-sample independent t-test was utilized for comparison of continuous variables between the freehand and 3D-printed cutting guide groups. A Pearson Chi square test or Fisher's Exact test was used for comparison of categorical variables between each group.

Results: Twenty-two patients treated with freehand resection were matched to five using a 3D-printed cutting guide. Negative margins were recorded in 50% (n = 11/22) of freehand patients and in 100% (n = 5/5) of the 3D-printed group (p = .040). Local recurrence was more frequent in the freehand group (55.0% vs 0%; p = .027), as was distant metastasis (68.4% vs 0%; P = .006). The reoperation rate was significantly higher among freehand patients (P = .040), with 50% (n = 11/22) undergoing at least one procedure compared to no 3D-printed cutting guide patients. There was a significantly greater rate of massive blood loss (>2L) in patients treated with freehand technique (76.2% vs 20%, respectively, P = .018) (Table 1). Reconstruction was performed at even rates across cohorts (P = .925), with no differences in the construct used.

Conclusion: In this study, despite the small sample size, we found that 3D-printed guides facilitate more accurate resections. Given the shorter follow-up in the cutting guide group, it is difficult to draw conclusions regarding longer-term oncologic outcomes. Nevertheless, we believe this technique offers worthwhile advantages over a freehand surgical technique.