TKA has become an effective measure for the treatment of end-stage knee diseases, which can effectively improve joint function and relieve pain [1–3, 4–7, 19, 23, 26]. Previous studies focused on the analysis of postoperative efficacy and perioperative complications in patients of different ages after TKA[19, 20]. Regardless of age, the satisfaction rate of knee surgery is more than 85%, and advanced age does not affect the efficacy of TKA[19].Other scholars have found that 70 years old is the best age for TKA [20]. There was no difference in the incidence of complications among patients younger than 75 years of age who received unilateral TKA or staged bilateral TKA [14].Different from previous studies, this study divided all patients undergoing SBTKA into age groups to study the incidence of complications in each group. It was found that patients aged between 60 and 64 had the lowest postoperative complication rate and blood transfusion rate.
The incidence of complications in patients younger than 60 years of age has not been reduced by younger age. Previous studies have only found that patients younger than 50 years of age have a significantly increased risk of revision due to periprosthetic infection or aseptic mechanical failure within 1 year after TKA[22].Based on the above studies, we can find that there is a significant increase in complications in elderly patients, which is also an indisput fact, especially for patients after SBTKA. Therefore, it is of great guiding significance for clinical orthopedic surgeons to select patients of the best age for surgery to reduce the incidence of postoperative complications.
In recent years, the nomogram is a widely used prediction tool in the field of clinical medicine, which has the ability to predict the occurrence risk of adverse events individually.This study developed a comprehensive postoperative complication prediction tool based on preoperative and intraoperative variables that accurately assessed the risk of complications within 30 days after surgery, as well as internal validation and evaluation of the model. Although some predictive models have been established in previous studies, we believe that our study improves on previous work.In the field of knee replacement, the nomogram has been used to predict the survival rate of prosthesis after knee tumor prosthesis replacement [23] and the periprosthesis infection rate [24].In addition, nomogram is used to predict the occurrence of major complications afterTKA [25] and blood transfusion [26].In the above prediction tools, only patients who received unilateral TKA were included, and such studies could not be fully applicable to patients with SBTKA. On the contrary, in our study, all the subjects were patients with SBTKA.
We collected a large number of candidate predictors, and for the screening of predictive indicators, this study comprehensively considered the statistical significance and professional significance. In the risk factor analysis, older age, lower preoperative hemoglobin levels, higher preoperative BUN levels, longer operation time, and ASA grade ≥ III were significantly associated with the incidence of complications within 30 days after surgery. These indicators were included in the prediction model of the nomogram.More importantly, four of these indicators were identifiable preoperatively, and their association with post-TKA complications has been widely reported in previous studies. Therefore, clinicians can accurately predict the risk of complications within 30 days after SBTKA preoperatively, which is crucial for early management.
The effect of advanced age on post-TKA complications has also been confirmed in previous studies [11–15]. The complication rate after TKA increases with age [27–29]. According to the survey, the hospital stay of elderly patients after TKA increased by 0.6 to 3.1 days, and the perioperative mortality rate ranged from 1.09–1.54% [27].Recently, however, different findings have been reported that in studies evaluating the effect of comorbidities and age on the incidence of postoperative complications after TKA, comorbidities themselves, rather than age, are the cause of increased postoperative morbidity [30].In addition, we found that preoperative lower hemoglobin was an independent risk factor for complications in patients with SBTKA within 30 days after surgery. Interestingly, a recent study found that lower preoperative hemoglobin levels were identified as an independent predictor of blood transfusion in patients after TKA [26].In this study, severe postoperative anemia was the most common complication, which well explained the influence of preoperative hemoglobin level on postoperative complications.
The results of this study suggest that longer operative time is an independent risk factor for complications within 30 days after SBTKA. Prolonged operative time can lead to increased intraoperative bleeding. In addition, prolonged exposure to the air in the operative area increases the risk of infection.At the same time, prolonged use of tourniquets increases the risk of vascular and nerve damage.It has been proved that prolonged operation time increases the incidence of postoperative complications in patients with TKA [31, 32]. It has been reported in the literature that the risk of requiring blood transfusion and hospital readmission increased by 9% and 5% for each 15 min increase in the duration of TKA [33].In percutaneous kyphoplasty, operative time is an independent risk factor for hidden blood loss [34], and the findings of the above studies are consistent with the results of this study.It has been reported that the American Society of Anesthesiologists (ASA) classification has a good correlation with the incidence of complications after TKA surgery [35–38]. This study also found that ASA grade ≥ III was an independent risk factor for complications within 30 days after SBTKA. The findings were consistent with previous literature that increased risk of complications after surgery was associated with an ASA score of 3 or 4 [39, 40].Interestingly, in a rigorous statistical analysis, the results showed that higher preoperative BUN levels were a risk factor for complications within 30 days after SBTKA, a finding that has rarely been reported in previous studies.The underlying mechanism between BUN levels and complications remains unclear. A possible explanation for this phenomenon is that kidney is an important organ for maintaining water, electrolytes and acid-base balance in the body, and renal insufficiency and dialysis are risk factors for infection and revision after artificial joint replacement [41, 42].
The prediction model established in this study has certain potential in clinical application, because the model has good discriminative ability and calibration degree, and the indicators included in the prediction model can be easily obtained through clinical examination at the early stage of admission, and the acquisition cost is relatively low.In this study, for the convenience of clinical application, a nomogram was developed based on the constructed prediction model, through which clinicians could quickly predict the occurrence of complications within 30 days of SBTKA and provide reference for identifying high-risk patients.
There are some limitations in this study. First of all, all the cases included in this study were from the same hospital, and it was a single-center study, so there might be case selection bias.Secondly, the model lacks external validation of independent queues, which requires strict validation of the model by queues in different centers. Therefore, more external evidence is needed to promote the clinical application of the model.