The principal findings of this study were as follows: 1) There was no difference in clinical outcome between the no follow-up loss group and the follow-up loss group, and 2) age, sex, height, weight, unilateral or bilateral, national health insurance status, distance from hospital, and number of families had no effect on follow-up.
Currently, there is a difference in opinion regarding the period and duration of follow-up after TKA. Some studies have reported that continuous outpatient follow-up after TKA is not necessary from an economic perspective [2, 3, 11, 12]. Another study reported the appropriate follow-up timing by calculating the complication probability [4]. Alternatively, follow-up was recommended only if the age at the time of surgery was under 70 years of age or if there were symptoms [5]. However, many orthopedic surgeons recommend annual or biennial follow-up for clinical or radiologic signs of failure [6]. Through this follow-up process, patients can feel relieved by checking their condition, and patients can receive quick additional treatment if necessary. In addition, the surgeon could get their surgical outcome feedback by checking the patient’s condition. If follow-up was not performed after surgery, the operator could only check the outcomes of the patients who do follow-up, and thus, overestimation or underestimation of the surgical outcomes is possible.
The one-year follow-up rate in this study was 67%. This was similar to the 60–70% of other studies that reported 1 year follow-up rates in TKA [10, 13]. However, direct comparison was difficult because the rate of outpatient follow-up after surgery may vary according to each country’s medical insurance system. In a previous study, it was reported that patients who did not follow up were associated with worse clinical outcomes in arthroplasty [14]. It was also reported that the clinical outcome of patients who did not follow up was poor even in other surgeries such as ophthalmology or bariatric surgery [8, 15, 16].
However, in this study, there was no statistically significant difference in clinical outcome and satisfaction between the two groups, but the average value showed a low trend in the follow-up loss group. This seems to be the effect of the relatively small sample size, and there was only KSS clinical as a directly comparable clinical score, and satisfaction was also subjective, so it was difficult to compare it with other studies.
Factors that could affect outpatient follow-up, such as age, sex, unilateral or bilateral surgery, presence or absence of family, and distance from hospital did not affect outpatient follow-up. It has been reported that the follow-up loss rate was high in younger age groups in arthroplasty, and there was no relationship between age and follow-up rate [13]. It is thought that this is not a problem of age itself, but rather the presence of absence of a job according to age, and age acted as a compounding factor. The existence of a job according to age may differ in each country, and this difference is thought to have occurred.
In South Korea, where this study was conducted, a national health insurance system was implemented. All nations are classified as targets for Medicare, and only approximately 3% of the economically weak are classified as eligible for Medicaid [17]. This study showed that postoperative outpatient follow-up was performed at a similar rate between Medicare and Medicaid patients, so there was a relationship between economic level and outpatient follow-up rate. This was different from the result of another study in which approximately 45% of patients did not follow-up on an outpatient clinic due to cost concerns [18]. This difference is thought to be due to the relatively low cost, which is approximately $10 per outpatient follow-up in South Korea due to the national health insurance system. In this study, the distance to the hospital and the presence or absence of a family living together did not affect outpatient follow-up. Five patients (11.1%) mentioned that they could not visit the hospital because of the distance, but two of five patients lived within 30 km of the hospital. Therefore, it is thought that the follow-up rate will be affected more by the existence of various public transportation means, the convenience of transportation, and the manpower that can accompany outpatient follow-up rather than the absolute distance and family.
This study has several limitations. First, there may be differences in surgical outcomes due to the nature of the phone interview. However, this was minimized by matching the doctor who measured the clinical score before TKA with the doctor who was interviewed over the phone. However, clinical KSS could not be measured. Second, whether or not to visit a hospital can be affected in various ways, but private insurance other than national health insurance was not considered. However, since the cost of outpatient treatment itself is not high, it was thought that the impact would be small. Third, the absolute distance it takes to get to the hospital is important, but it can also be affected by the convenience of a helper and transportation that can come to the hospital. Therefore, it cannot simply be mentioned that the time it takes to get to the hospital represents the distance. Fourth, the hospital fee reduction system of the hospital where this study was conducted may also have an effect on the outpatient follow-up rate. Although this may affect the overall follow-up rate, since the reduction itself is applied to all patients visiting this hospital, it was thought that the effect on follow-up would be small.