BCIS is a serious and potentially lethal perioperative complication of cemented hip replacement which is theoretically caused by cement monomer mediation, immune reaction or emboli during cement and prosthesis insertion. The aim of this study was to analyse the incidence and outcome of BCIS in OFNF patients undergoing cemented hip replacement, and to investigate the predictive factor for BCIS in these patients.
The incidence of overall BCIS in the present study was 26.1% (with BCIS grades 1, 2 and 3 as 19.7%, 3.6% and 2.8%, respectively), which is comparable with previous studies [2, 14]. The in-hospital and postoperative 1-year mortality rates in patients with BCIS-gr2/3 were higher than those in patients with BCIS-gr0/1 (11.1% vs. 0.8%, and 11.1% vs. 3.8%, respectively), but did not have statistical significance. Although these results were dissimilar to the previous study by Olsen et al.  that reported significantly higher 30-day and 1-year mortality in BCIS-gr2/3 compared with BCIS-gr0/1, this difference could be explained by the relatively small study population in the present study. Moreover, our results also showed that major postoperative complications in patients with BCIS-gr2/3 were also significantly higher than those in patients with BCIS-gr0/1 (44.4% vs. 8.3%, p < 0.01). These results highlight the significance problem of this complication and emphasise the need for meticulous attention to preoperative and intraoperative management.
This study also revealed the significant correlation between BCIS-gr2/3 and the patient and surgical factors. From the multivariate regression analysis, our study showed that the independent factors for BCIS-gr2/3 were preinjury wheelchair or bedridden ambulatory status (OR = 11.8, 95% CI 1.1–131.8, p = 0.04), underlying cardiac arrhythmia (OR = 5.7, 95% CI 1.1–28.9, p = 0.04) and use of shape-closed femoral stem (OR = 9.8, 95% CI 1.7–57.8, p = 0.01). The poor preinjury ambulatory status and cardiac arrhythmia are both directly related to the patients’ impaired cardio-pulmonary function and, therefore, result in significant physiological disturbance during surgery and cement implantation. This finding is also comparable to the previous studies that showed the significant association between BCIS-gr2/3 and patients’ physiological factors, such as ASA physical status grade 3 or 4, underlying chronic obstructive pulmonary disease  and pulmonary hypertension .
The significant correlation between shape-closed femoral stem and BCIS-gr2/3 could be explained by the pressure-model mechanism as an effect of stem geometry. Generally, the shape-closed stem has larger proximal geometry than a force-closed stem, which would result in higher intramedullary pressure during stem insertion and release a greater number of embolic particles into the vascular system. Consequently, the shape-closed stem insertion should pose a higher risk of BCIS-gr2/3 than the force-closed stem.
The strengths of the present study are related to the preoperative DVT screening to exclude preoperative DVT in all cases and the use of the same surgical approach and cementation protocol in the treatment of osteoporotic femoral neck fracture in the elderly, as previously described. Therefore, some confounding factors—such as the type of bone cement used, the time of cement insertion and the cementing technique—could be controlled. Moreover, to the best of our knowledge, the present study is the first study that demonstrates the impact of femoral geometry on the severity of BCIS. Hence, more studies on how the shape-closed femoral stem affects intramedullary pressure are required.
This study had the following limitations. First, regarding the retrospective nature of this study, some useful clinical information, such as smoking status and alcohol intake, was not available in all cases and, therefore, was absent from our analysis. Second, our sample size was relatively small and from only one centre. Thus, other possible risk factors—such as medications, anaesthetic technique and type of surgery—might remain undetected. Finally, the cementing technique used in our institution (use of high viscosity cement with manual mixing and finger-packed technique) did not comply with the previous recommendation (use of low viscosity cement with vacuum mixing and cement gun) , mainly due to the restriction of medical insurance in our country. This cementing technique protocol might affect the outcome of the present study. However, our results did not show a higher incidence of BCIS, perioperative complications or postoperative mortality compared with previous studies. Therefore, a well-designed multicentred prospective study with a larger sample size is recommended to explore the effect of other potential risk factors.