Rates of any adverse events in patients with metastatic pathological femoral fractures were greater than those with non-pathological femoral fractures after adjusting with other potential factors. The risk of adverse surgical and medical events in the pathological group was around twofold to threefold higher than the other group. Patients with pathological fractures were more likely to be readmitted, but less likely to be re-operated on.
Rates of overall adverse events, regardless of the fracture type, in our study were markedly high compared to findings in previous studies, which had different fracture locations and outcome measurements [3, 7, 27, 29]. Regarding outcome measurements, other studies did not define acute postoperative anemia as an adverse event, whereas this was the most common adverse event in our study, leading to higher overall adverse event rates [3, 27]. However, if anemia was dismissed, the overall adverse event rates were similar to the study of Ristevski et al. [29] As to fracture locations, Behnke et al. [7] also included fractures at the spine, upper, or lower extremities, not only femur fractures, as in our study. Due to the wide range of fracture locations, the rates of adverse events were probably attenuated.
Acute postoperative anemia was the most frequent adverse surgical event following intramedullary nailing, which was consistent with a previous study that assumed that performing intramedullary nailing was susceptible to bleeding during canal reaming. This resulted in postoperative anemia, which in turn required postoperative blood transfusions [30]. Significantly higher acute anemia rates in patients with pathological fractures have been found. A possible explanation was that the ongoing bleeding effects and coagulopathic state from multiple traumas in the non-pathological group might lower than the chance of excessive bleeding from passing the long intramedullary nail through the tumor and type of primary cancer; particularly in highly vascularized tumor; including thyroid, prostate, and renal cancer [31–33]. Although intraoperative total blood loss and blood transfusions in our study were not different between both groups, the blood loss measured by the volume of drainage was higher in the pathological group, which supported the results of postoperative anemia. We could not establish any significance of surgical site infection, hematoma, or nerve injuries, because these event rates were low in both groups.
In line with adverse surgical events, risks of adverse medical events were greater in the pathological group. Septic shock and urinary tract infection were common adverse medical events that were higher in the pathological group than that of the non-pathological group. There was inconsistency with the findings of a previous study that included impending fractures undergoing prophylactic stabilization as a control group [27], while our study selected non-pathological fractures. High infection rates in pathological fractures could be explained through old age, low immunity, and the poor baseline status of patients with metastatic bone disease [34]. In addition, patients with pathological fractures required more time for ambulation, which increased the risk of urinary tract infection [35]. Even with slowly progressed ambulation, the incidences of venous thromboembolism events were not significantly increased in patients with pathological fractures because of medical and mechanical prophylaxis given during admission.
In our study, the readmission risk within one year was more than twice and approached significance, which was different from a previous study measuring readmission at only 30 postoperative days [27]. Due to the longer period of data collection in our study, it tended to include more readmission events from adverse events, added with disease progression in the pathological group. Although the previous study did not report on reoperation rates, we attempted to explore this issue, and found similar reoperation rates between the pathological and non-pathological groups. These findings may result from the hypothesis that the pathological group had lower survival rates, particularly in patients experiencing postoperative complications [15, 27]. Additionally, the surgery goal for pathological fractures was only to improve quality of life; therefore, a second operation was rarely required, with the exception for postoperative complications [14, 16]. However, the goal of surgical fixation in both traumatic or non-pathological fractures is to provide stability and restore length, alignment, and rotation of the femur to achieve proper bony union. Some patients with this type of fracture were exposed to delayed union or nonunion risk factors; including, smoking history, open fractures, and severe enveloped soft tissue injury [36]. Consequently, they experienced a second surgery to assist in bone healing or to correct malalignment of the femur [37].
To our knowledge, no study has compared adverse events between patients with pathological and non-pathological femoral shaft fractures following surgical fixation. We followed the patients one year after discharge to observe the consequences of their surgical procedure. This study does have some limitations. First, this was a single-center study, which may limit the generalizability of its findings. Second, the sample size calculation considered the rates of any adverse events between the two groups that may have led to a small sample for specific adverse events. Third, we did not calculate the sample size based on multivariate analysis to identify other associated factors. Finally, this was a retrospective study in which some important data were not be recorded.
Recognizing the probability of postoperative adverse events in patients undergoing intramedullary nailing will assist clinicians in providing pertinent information to both patients and their families. Moreover, as a consequence of high adverse surgical and medical events rates, preoperative patient preparation should be heeded, especially reserved blood components. During the postoperative period, hematocrit and vital sign monitoring are suggested, due to the high risks of postoperative anemia and infection, along with promptly solving problems in case of any adverse events occurring. A further multi-center, prospective study with large sample size is suggested.