Do skip-N2 metastases significantly impact overall survival and disease-free interval in N2 non-small-cell lung cancer patients? A multicentre analysis.

OBJECTIVES: Skip-N2 metastasis (N0N2), thus N2 metastasis in the absence of N1 metastasis, occurs in ∼20-30% of non-small-cell lung cancer patients. N0N2 patients have a better prognosis than continuous-N2 metastasis (N1N2) patients following surgery. However, this effect remains controversial. Therefore, we conducted a multicentre study to compare the long-term survival and disease-free interval (DFI) of N1N2- and N0N2 patients. METHODS: One- and 3-year survival rates were measured. Kaplan-Meier curves and a Cox proportional hazards model assessed survival and were used to identify prognostic factors for overall survival. In addition, we performed propensity score matching (PSM) to rule out confounding factors. All patients received adjuvant chemoradiation therapy according to European guidelines. RESULTS: Between January 2010 and December 2020, 218 stage IIIA/B N2 patients were included in our analysis. The Cox regression analysis revealed that N1N2 significantly influenced the overall survival rate. Before PSM, N1N2 patients showed significantly more metastatic lymph nodes (P < 0.001) and significantly larger tumours (P = 0.05). After PSM, baseline characteristics did not differ between groups. Before and after PSM, N0N2 patients showed significantly better 1- (P = 0.01; P = 0.009) and 3-year (P < 0.001) survival rates than N1N2 patients. Furthermore, N0N2 patients showed significantly longer DFI than N1N2 patients before and after PSM (P < 000.1). CONCLUSIONS: Prior and after PSM analysis, N0N2 patients were confirmed to have better survival and DFI than N1N2 patients. Our results demonstrate that stage IIIA/B N2 patients are heterogeneous and would benefit from a more precise subdivision and differential treatment.

Revision of cannulated and perforated cement-augmented pedicle screws: a biomechanical study in human cadavers.

STUDY DESIGN: Biomechanical investigation of primary and revised cement-augmented pedicle screws in comparison with unaugmented screws. OBJECTIVE: To evaluate revision of cannulated pedicle screws and investigate cement-augmented and nonaugmented screws biomechanically, testing the torque of primary screws and axial pullout force of revised screws in cadaver vertebrae. SUMMARY OF BACKGROUND DATA: Cement augmentation increases the pullout force and stability of pedicle screws in vertebrae with low bone mineral density, but surgeons are concerned about complications during revision. METHODS: Bone mineral density was measured using quantitative computed tomography (CT) in 23 osteoporotic thoracolumbar junction vertebrae from human cadavers. Cannulated pedicle screws, augmented with bone cement (on right) or unaugmented (left), were inserted into each vertebra. After CT control, extraction torque was measured and the pedicles were reinstrumented with larger-diameter screws. The right screws were augmented again, with another CT control, before pullout testing. RESULTS: Mean vertebral bone density was 52.6 mg/cm. No major screw malpositioning was observed on primary CTs. Cement leakage was observed anterolaterally and into the spinal canal. Mean maximal torque in augmented screws (1.2 Nm, SD: 0.6) differed significantly from nonaugmented screws (0.8 Nm, SD: 0.6). Screw removal did not lead to vertebral destruction. No relevant changes due to positioning or leakage were observed on CT after revision procedures compared with primary findings. Maximal pullout force in revised augmented screws (713.2 N, SD: 254.6) differed significantly compared with nonaugmented screws (554.0 N, SD: 296.5). Bone damage was observed in several vertebrae during pullout force testing in augmented screws. CONCLUSION: Revision of cement-augmented pedicle screws was feasible without bone destruction, and larger-diameter screws can be used in revision procedures. The pullout force after revision was significantly better in cement-augmented screws. During pullout testing, the cement-bone interface broke before the screw-cement interface in several vertebrae, fracturing the pedicles.