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BACKGROUND AND AIM: Currently, the primary treatment modality for patients with colorectal adenocarcinoma (CRA) is radical surgery combined with postoperative adjuvant chemotherapy (PAC). However, many elderly patients decline PAC due to concerns about their underlying physiological condition, and the impact of PAC on the prognosis of elderly patients remains uncertain. METHODS: We extracted data from the SEER database for CRA patients aged 75 and above between 2010 and 2019. Utilizing propensity score matching (PSM), we stratified the patients into a PAC group and a non-PAC group, enabling us to compare the differences in Kaplan-Meier survival curves between these two groups. Furthermore, through univariate and multivariate Cox regression analyses, we identified the clinical factors that influence the survival of elderly CRA patients and compared the prognostic disparities between the two patient groups within specific subgroups of these clinical factors. RESULTS: Following PSM, a total of 3668 patients were included and divided into the PAC group and the non-PAC group, with no statistically significant differences observed in crucial clinical characteristics between the two groups. Kaplan-Meier analysis revealed a significantly better prognosis for patients in the PAC group compared with those in the non-PAC group. In addition, age, chemotherapy, TNM staging, gender, and preoperative CEA levels were all identified as important factors affecting patient prognosis. Moreover, PAC provided survival benefits across the majority of levels within the aforementioned subgroups. However, in specific subgroups (age > 90, Grade IV stage, median household income < $40 000), PAC did not confer any survival benefits. CONCLUSION: PAC can significantly improve the prognosis of elderly CRA patients. Nonetheless, in certain population subsets characterized by specific clinical features, PAC does not provide any survival benefits.
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OBJECTIVE: Screw loosening is a common complication of pedicle screw internal fixation surgery. This study aimed to investigate whether the application of a porous scaffold structure can increase the contact area between screws and bone tissue by comparing the bone ingrowth and screw-bone interface of porous scaffold core pedicle screws (PSCPSs) and hollow lateral hole pedicle screws (HLHPSs) in the lumbar spine of Bama pigs. METHODS: Sixteen pedicle screws of both types were implanted into the bilateral pedicles of the L1-4 vertebrae of two Bama pigs. All Bama pigs were sacrificed and the lumbar spine was freed into individual vertebrae at 16 weeks postoperatively. After the vertebrae were made into screw-centered specimens, micro-computed tomography (micro-CT) analysis and histological observation were performed to assess the screw-bone interface and bone growth around and within the screws. RESULTS: We found that the bone condition around PSCPSs and HLHPSs did not show significant differences on micro-CT three-dimensional reconstruction images. CT transverse views showed different bone growth inside the two screws. In PSCPSs, bone tissue was seen to fill the internal pores and was evenly distributed around each strut. Inside HLHPSs, bone growth was confined to one side of the screw and did not fill the entire cavity. Osteometric analysis showed that bone volume fraction (BVF) and trabecular number (Tb.N), the parameters representing bone mass, were higher in PSCPSs than in HLHPSs. These differences were not statistically significant (P>0.05). Histological observations visualized that the osseointegration within PSCPSs was superior to that of HLHPSs, and the tight integration of bone tissue with the porous scaffold resulted in a larger screw-bone integration area in PSCPSs than in HLHPSs. CONCLUSIONS: Compared with HLHPSs, PSCPSs possessing a porous scaffold core could promote bone ingrowth and osseointegration, resulting in an effective enhancement of the combined area of the screw-bone interface.
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OBJECTIVE: Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine. METHODS: Thirty-two pedicle screws of both types were implanted bilaterally into the L1-4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull-out tests, as well as cyclic bending and pull-out tests, while the mechanical properties were assessed using three-point bending tests. The data generated were statistically analyzed using paired-sample t-tests and two independent sample t-tests. RESULTS: We found that the maximal pull-out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p < 0.05, p < 0.05). In 800 cycles of the bending tests, neither PSCPS nor HLHPS showed loosening or visible detachment, but their maximal pull-out forces after cyclic bending tests decreased compared to those in cycles without cyclic bending tests (7.43% and 14.89%, respectively), with no statistical significance (p > 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three-point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively). CONCLUSIONS: Compared with the HLHPSs, the PSCPSs have greater pull-out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation.