Alvarez‐Breckenridge, Christopher

OBJECTIVE Spinal stereotactic radiosurgery (SSRS) is an established treatment modality for spinal metastatic disease. A common complication of SSRS is postradiation pathologic fracture. The authors evaluated the risk of pathologic fracture in sacral SSRS. METHODS All patients receiving SSRS in 1 to 5 fractions to 1 or more sacral levels between 2011 and 2020 at participating institutions were included. Demographic, histological, anatomical, and outcome data were obtained from electronic medical records. Data were analyzed using SPSS version 28. RESULTS Of 67 total patients, 50 (74.6%) were men and 17 (25.4%) were women. The most common tumor histologies were prostate adenocarcinoma (n = 16 [23.9%]) and renal cell carcinoma (n = 12 [17.9%]). Median (range) age at treatment was 63 (8–87) years. The mean ± SD (range) number of levels treated was 1.5 ± 0.7 (1–4) levels. Mean ± SD (range) bone density at S1 was 208.0 ± 74.4 (−3.0 to 443.3) Hounsfield units (HUs). Median (range) follow-up was 16.6 (1.5–132) months, median ± SD (range) overall survival was 24 ± 21.0 (1.7–83.3) months, and the 1-year local control rate was 83.6%. Fourteen patients (20.9%) experienced fracture within the radiation field. There was no association between fracture and patient sex (p = 0.32), age (p = 0.40), S1 HU (p = 0.28), tumor location according to Denis classification (p = 0.87), presence of pain (p = 0.66), single versus multifraction radiation (p = 0.44), or number of levels treated (p = 0.52). Patients experiencing in-field progression were more likely to experience fracture (61.5% vs 10.2%, p < 0.001), and patients experiencing fracture had a higher average Spine Instability Neoplastic Score than patients without fracture (5.7 vs 4.3, p = 0.049). Only local control remained as a factor associated with sacral fracture in the multivariate analysis. Of the patients experiencing fracture, 10 (71.4%) were symptomatic and 3 of those (30.0%) underwent post-SSRS surgical intervention. CONCLUSIONS Pathologic fracture may occur after sacral SSRS in a significant number of patients and is significantly associated with failure of local control.

Study Design Narrative Review. Objective The management of spinal tumors requires a multi-disciplinary approach including surgery, radiation, and systemic therapy. Surgical approaches typically require posterior segmental instrumentation to maintain long-term spinal stability. Carbon fiber reinforced pedicle screws (CFRP) are increasingly used in the oncologic setting due to reductions in both imaging artifacts and radiotherapy perturbations compared to titanium implants. We performed a review of the literature and highlight advantages and future areas of study for CFRP. Methods We performed a systematic review of the literature using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and identified 10 articles including 573 patients. Across all studies we reviewed patient demographics, tumor types treated, hardware-related features, complication rates, recurrence, survival, and follow-up. Results Across 10 studies, a total of 1371 screws placed. Surgical and non-surgical complications were reported in 18.3% of patients. Disease progression at the surgical site was detected in 7.3% of patients. There was no significant difference in clinical or hardware complications between CFRP or titanium implants. The most frequent complication attributable to implanted CFRP hardware included screw breakage in 2.4% and loosening in 1.7% of patients, respectively. Conclusion CFRP provide a unique tool in the setting of spinal oncology. With a safety profile comparable to titanium, we review the documented advantages of CFRP posterior implants compared to titanium, while also addressing their current limitations. Additionally, we highlight several areas of future research to identify the optimal patients who will achieve the greatest benefit of CFRP.

Study Design Survey study. Objectives The purpose of this study was to characterize the utility of 3D printed patient specific anatomic models for the planning of complex primary spine tumor surgeries. Methods A survey of individual members of an international study group of spinal oncology surgeons was performed. Participants were provided a clinical vignette, pathologic diagnosis, and pre-operative imaging for three primary spinal oncology cases. Study participants provided a free text surgical plan for resection and were then presented an associated 3D printed model for each case and asked to re-evaluate their surgical plan. Results Ten spinal oncology surgeons participated in the study, representing nine institutions across five countries. Four of the surgeons (40%) made significant changes to their surgical plan after reviewing the 3D models, including sacrifice of an additional nerve root to obtain negative margins, sparing an SI joint that was originally planned for inclusion in the en bloc resection, adjusting the location of osteotomy cuts, changes to the number of surgical stages and/or staging order, and preservation of neurology that was originally planned for sacrifice. The overall impression of the 3D models was positive, with 90% of the participants stating they found the 3D model useful in developing a surgical plan. Conclusions Surgical planning for resection of primary spinal column tumors is challenging and time intensive. 3D printed patient specific surgical models may be an additional tool that can augment surgical planning and execution by improving the chance of accomplishing surgical resection goals and minimizing morbidity.

OBJECTIVE The purpose of this study was to analyze risk factors for sacral fracture following noninstrumented partial sacral amputation for en bloc chordoma resection. METHODS A multicenter retrospective chart review identified patients who underwent noninstrumented partial sacral amputation for en bloc chordoma resection with pre- and postoperative imaging. Hounsfield units (HU) were measured in the S1 level. Sacral amputation level nomenclature was based on the highest sacral level with bone removed (e.g., S1 foramen amputation at the S1–2 vestigial disc is an S2 sacral amputation). Variables collected included basic demographics, patient comorbidities, surgical approach, preoperative radiographic details, neoadjuvant and adjuvant radiation therapy, and postoperative sacral fracture data. RESULTS A total of 101 patients (60 men, 41 women) were included; they had an average age of 69 years, BMI of 29 kg/m2, and follow-up of 60 months. The sacral amputation level was S1 (2%), S2 (37%), S3 (44%), S4 (9%), and S5 (9%). Patients had a posterior-only approach (77%) or a combined anterior–posterior approach (23%), with 10 patients (10%) having partial sacroiliac (SI) joint resection. Twenty-seven patients (27%) suffered a postoperative sacral fracture, all occurring between 1 and 7 months after the index surgery. Multivariable logistic regression analysis demonstrated S1 or S2 sacral amputation level (p = 0.001), combined anterior–posterior approach (p = 0.0064), and low superior S1 HU (p = 0.027) to be independent predictors of sacral fracture. The fracture rate for patients with superior S1 HU < 225, 225–300, and > 300 was 38%, 15%, and 9%, respectively. An optimal superior S1 HU cutoff of 300 was found to maximize sensitivity (89%) and specificity (42%) in predicting postamputation sacral fracture. In addition, the fracture rate for patients who underwent partial SI joint resection was 100%. CONCLUSIONS Patients with S1 or S2 partial sacral amputations, a combined anterior–posterior surgical approach, low superior S1 HU, and partial SI joint resection are at higher risk for postoperative sacral fracture following en bloc chordoma resection and should be considered for spinopelvic instrumentation at the index procedure.