Despite bilateral knee and hip arthroplasty being frequently performed, most studies paid attention to clinic outcomes, and only a few studies have been published recently on this topic. However, previous studies have not compared costs about THA, to say nothing of comparing costs when pooled both THA and TKA patients[2, 7, 12]. In this study, we compared the cost of simultaneous and staged procedures among TKA, THA, and their combination groups, found a significant difference between the two procedures in three groups. Viewing the general conclusions as a whole, the results showed that almost all kinds of costs were higher in staged TKA, THA and combination simultaneous group.
Our results are consistent with previous studies, which have estimated the economy of simultaneous TKA or THA, compared with staged TKA or THA [2, 16–19]. A study from Taiwan demonstrated that all categories of medical costs, except for therapeutic procedure fees, were lower in the simultaneous TKA group[2]. However, a recent single-center study concluded that there was no significant difference in total hospital costs between two groups of TKA, and it might be explained that the majority of their patients who received simultaneous TKA underwent patient rehabilitation(IPR) unit admission, and IPR costs were added for all patients discharged to IPR[7].
At the same time, many studies including our study have found a shorter LOS in simultaneous TKA or THA. Compared with simultaneous surgery, staged surgery will increase the number of anesthetics and hospital admissions, which usually means a longer LOS which has been regarded as a pivotal indicator of hospital efficiency and quality of health care[20]. Prolonged LOS will not only have a negative impact on health outcomes, causing iatrogenic illness easily, but also high hospital occupancy resulted in a resultant loss of efficiency and access, all of which would bring a marked increase in health expenses[21, 22]. And this might be explained the relationship between exceeding LOS with high cost, for long LOS unusually followed high costs[21–23].
This study found no significant difference in in-hospital complications, whether it was TKA, THA or pooled together. Previous studies about complications differ from each other. Kamath et al[1] did not find significant differences for complications between the simultaneous THA group and the staged THA group either. Seung-Chan Kim et al[12] found a lower incidence of postoperative prosthetic-related complications in the simultaneous THA group. When it turns to TKA, several studies reported a lower rate of complications in the simultaneous TKA group[14, 16, 19, 24, 25]. Whereas some studies have reported a higher rate of specific complications, such as venous thromboembolism (VTE)[7] and myocardial infarction (MI)[26] for the patients older than 65 years in the simultaneous TKA group. However, Sheth et al[27] considered that the differences in the baseline characteristics of the patients, surgeon’s preference, and hospital characteristics may hamper the prior comparisons of complications between simultaneous TKA and staged TKA. They compared these two sub-groups by adjusting for these differences, founding no significant difference in complication rates between two sub-groups. Since the data of our study came from a singer center, and the patient who underwent two procedures separated by the same surgeon was considered to have undergone staged bilateral TKA or THA, the inconsistency in-hospital characteristics, patient selection, surgeon skill, and surgeon preferences might be avoided. A meat-analysis[28] also proved no significant differences in complication rates. Moreover, studies that reported a higher rate of complication usually concentrated on certain complications, while our studies emphasized on the total number of in-hospital complications.
However, we also found a higher incidence of blood transfusion in the simultaneous groups compared with staged groups in all three groups. Sobh et al.[7], in a singer institution of 562 patients, reported a significantly increased rate of blood transfusion with simultaneous TKA and the same result was found in using a large Canadian data set[13]. In a series of bilateral total knee or hip arthroplasty, performed at a staged interval, would have more time for hematopoiesis to replenish blood loss because of the first surgery[29]. Most of the staged patients in our study waited more than 6 months between procedures. Kamath et al.[1] found no blood transfusion in either group, but a higher blood loss in the staged group for THA. Because of the limitation of data, we could not analyze the volume of blood transfused. Further study needs to clarify the relationship between blood loss volume and different ways of procedures. And different blood transfusion practices and standards of reporting in different hospitals and surgeons would influence the final result, the interpretation of these results should be cautious.
Owing to the limitation of data and the aim of our study, other clinical outcomes were not included. Most clinical outcomes were better for simultaneous TKA and THA, and they indeed have some advantages, compared with staged TKA and THA, such as less length of stay in the hospital, lower costs, and no difference in complications which have been proved by this study. Accounting for a better surgical outcome, and relieving economic burden both for patients, families, and societies, we suggest that bilateral TKA and THA patients could be treated with a simultaneous TKA and THA rather than a staged TKA and THA. However, this procedure must be conducted very carefully, especially for elderly and high-risk patients.
Patients were older in the staged TKA and THA group than in the simultaneous TKA and THA group (Table 2), which is consistent with previous studies[1, 13]. Considering the operative risk, surgeons may prefer simultaneous procedures in younger and healthier patients, which might cause a selection bias and possibly result in better outcomes for simultaneous TKA and THA than staged TKA and THA. A recent study about the geriatric population reported that there was no association with any additional or significantly increased risk of morbidity or mortality compared to staged bilateral TKA[32]. Therefore, simultaneous TKA might be a safe and efficient choice for elderly people. While there needs more researches to remove this age bias and prove the suitability for older people, particularly in THA patients. An adequately powered randomized trial, which could overcome the selection bias inherent in this retrospective study design, would be a good choice for further clarification of outcomes.
These results may have important implications for the insurance department in the current health care environment. The cost of different surgeries for TKA and THA was different enough to warrant a separate classification for different procedures. Our results showed that staged bilateral TKA and THA have a greater financial cost than simultaneous bilateral TKA and THA, combined with the different clinical results of previous studies, suggesting that the two procedures should be classified separately for more accurate reimbursement. However, simultaneous bilateral TKA and THA and staged bilateral TKA and THA (calculate two surgical operations and reimbursed twice) are currently classified under the same Diagnosis Related Groups (DRGs), which means that they are reimbursed at the same level. Since medical insurance is the primary payer for patients in China[33], there needs reclassification of medical insurance items about these two procedures.
Limitations should be listed. Firstly, we investigated data from a single institution that performed a relatively high rate of TKA and THA, the universality of this study may be limited. However, this provided consistency in factors that might potentially affect clinical and financial outcomes, such as hospital characteristics, patient selection, surgeon skill, and surgeon preferences. Secondly, we did not analyze too many clinical outcomes because of the limitation of data, but our study aims to compare the medical expenditures and a fair number of previous studies have compared direct clinical outcomes. Thirdly, there might be a selection bias about the distribution of age, simultaneous procedures tending to be younger patients due to the surgeons' selection bias. But previous research has proved that simultaneous TKA might be a safe and efficient choice for elderly people. And despite being younger, the simultaneous groups experienced a higher rate of blood transfusion. Further researches should include an adequately powered multi-center randomized trial, which could overcome the selection bias of this retrospective study design.
In spite of these limitations, the strengths of our study including all kinds of hospitalization costs and many patients in both TKA and THA patients, and pooled patients together to prove the results. To our knowledge, this is the first study to evaluate the direct costs between two procedures both for TKA and THA and the whole patients in the same cohort. Further study needs to evaluate both the direct hospital costs and more clinical outcomes in the same cohort and an adequately powered randomized trial would be better.