Evaluation of Appropriateness of the Reimbursement Criteria of Korean Health Insurance Review and Assessment Service for Total Knee Arthroplasty

The study was approved by the Institutional Review Board of Hanyang University Medical Center (No. HYUH 2020-12-004) and patient informed consent was waived.

We used prospective, longitudinally maintained database obtained from our institution to retrospectively identify patients who underwent primary TKA according to one surgeon’s (CHC) consistent decision from December 2017 to April 2020. Inclusion criteria were patients who had (1) primary TKA, (2) completed preoperative patient-reported outcome surveys, and (3) had knee radiographic imaging preoperatively. Revision TKA cases were excluded from the study. The patients were classified as an appropriate or an inappropriate group by the reimbursement criteria set by HIRA and compared with the classification results based on Riddle et al.’s1) and Hawker et al.’s5) criteria. We did detailed analysis on the inappropriate group patients and re-evaluated them using other appropriateness criteria suggested by Riddle et al.1) and Hawker et al.5) to reveal issues of the reimbursement criteria for primary TKA used in South Korea.

A range of objective validated questionnaires are available for assessing joint-specific parameters and general health outcome before TKA, including Knee Society Knee score (KSKS), Knee Society Function score, Knee Injury and Osteoarthritis Outcome score (KOOS), and WOMAC, all of which were surveyed and calculated one day before surgery by an attending orthopedic surgeon (CHC). In addition, Korean Knee score (KKS), High-Flexion Knee Scoring system, Feller patella score, Kujala score, and Samsung Medical Center patellofemoral (SMC PF) scoring system were surveyed to consider the floor-sitting culture where high-knee flexion position is common9) and to assess PF-specific symptoms.10) Excluding the WOMAC score, SMC PF score, and pain and function scores, higher scores indicate less severe symptoms. Preoperative radiographs were rated by an orthopedic surgeon (CHC) according to the Kellgren-Lawrence (KL) classification system of osteoarthritis.11)

These scores were evaluated in each appropriate, inappropriate, and inconclusive group classified by the three appropriateness criteria compared in this study, and the inappropriate group classified by HIRA’s reimbursement criteria was re-evaluated. For statistical analysis, the analysis of variance was used to compare scores between groups and the threshold for statistical significance was set at p < 0.05.

The most important finding of this study is that we confirmed the inappropriate cases classified by HIRA’s reimbursement criteria had radiologically severe arthritis (all with more than bi-compartmental osteoarthritis involvement and KL grade 3 or 4) and several clinical scores with worse symptoms compared to the appropriate cases. So, objective clinical scores could better represent patient symptoms and lowering the age limit could enable those judged inappropriate by the current reimbursement criteria to get access to healthcare.

This is the first study on HIRA’s reimbursement criteria for TKA. All citizens in South Korea are compulsorily subscribed to the National Health Insurance Service and HIRA evaluates the medical service fee, quality of healthcare, and adequacy of medical service of the healthcare provider to determine reimbursement. This ultimately causes physicians to make medical decisions according to the reimbursement criteria and be often hesitant to make exceptions, thus biased decisions are inevitable. It is ideal for the reimbursement criteria to be equivalent to clinically based treatment indications, but patients with an unmet need for surgical intervention such as TKA still exist.8) In this regard, finding new criterion to facilitate access to TKA for those in need is critical.

The reimbursement criteria set by HIRA is a validated tool that uses age and KL grade as the two main factors, in addition to the underlying condition after 3 months of conservative treatment before deciding on TKA, which may be devastating for people with far advanced knee osteoarthritis. Therefore, clinical scores could be used as markers for timely TKA, as well as better representation of patient symptoms, in terms of knee pain, deformity, and functional deterioration.9, 12, 13) There were 14 cases (3.1%) of the 448 cases that did not fit HIRA’s reimbursement criteria, which were far fewer than the cases considered inappropriate for TKA according to Riddle et al.’s1) or Hawker et al.’s5) criteria.

When using Riddle et al.’s appropriateness criteria,1) of the 14 cases classified as inappropriate, 9 cases (64.3%) were classified as appropriate, 5 cases (35.7%) were classified as inconclusive, and no cases were classified as inappropriate. When using Hawker et al.’s appropriateness criteria,5) 12 cases (85.7%) were appropriate and 2 cases (14.3%) were categorized as inappropriate. The 2 inappropriate cases had radiologic findings of KL grade 3 and above with several clinical symptoms (KOOS symptoms, p = 0.97; KOOS sport and recreation, p = 0.23; KSKS, p = 0.50) and worse symptoms than those in the appropriate cases categorized by HIRA’s reimbursement criteria. If radiologic arthritis severity and other clinical factors not included in the WOMAC criteria (pain, function, and stiffness) are taken into account, these 2 cases would be considered suitable for TKA.

Using Riddle et al.’s TKA appropriateness criteria,1) 20 cases (4.5%) were classified as inappropriate. Patient symptoms and KL grade were the two strongest predictors of appropriateness judgement in the regression models tested by Escobar et al.2) and are weight heaviest in the criteria. The inappropriate cases had on average moderate symptoms: 17 cases with KL grade 3 or below and 3 cases with KL grade 4, which do not meet the age, symptom, and disease status profile of a typical TKA patient.14, 15)

However, all 20 cases satisfied HIRA’s reimbursement criteria for TKA, so there may be room for improvement in the Riddle et al.’s appropriateness criteria.1) These results show that Riddle et al.’s appropriateness criteria1) do not work well on cases with rheumatoid arthritis, avascular necrosis, or secondary osteoarthritis, a disadvantage over HIRA’s reimbursement criteria where disease profile is taken into account regardless of age.

The small number of inappropriate cases categorized by HIRA may reflect the surgeon’s personal decision to meet the requirements of the reimbursement criteria but make a few exceptions based on patient’s severe knee pain and functional deterioration; the KOOS pain (p = 0.15) and symptoms score (p = 0.08), WOMAC score (p = 0.20), and KKS score (p = 0.36) showed worse symptoms in the inappropriate cases than those in the appropriate cases (Table 2). Six cases (42.9%) with KL grade 4 were also in the inappropriate group for being below 60 years of age and this age limit of 60 years is higher than 55 years of age in Escobar et al.’s2) or Riddle et al.’s1) appropriateness criteria. This arbitrary age criterion16) could be lowered because TKA utilization is increasing in younger patients in the United States and Europe.17)

There are some limitations of this study. First, our study was done in a single institution, and thus the patient population may not fully represent the rest of the country. Second, Riddle et al.’s1) and Hawker et al.’s5) appropriateness criteria are focused on selecting patients with the most improvement in knee symptoms through TKA and avoiding improper interventions, while HIRA’s reimbursement criteria are a medical insurance-based policy that prioritizes distribution of medical fees. Thus, comparing these criteria may not be suitable since they have different goals. Third, comorbidities of patients are factors that are not taken into account in all three criteria, and recent studies have shown they have effects on complication rates and outcome of TKA.18, 19, 20)

As regulations change to increase insured individuals, an impact on utilization of TKA will follow. This may represent an unmet need for TKA among newly enrolled beneficiaries,8) revealing potential patients that do not undergo surgical procedures due to insurance-based reasons. HIRA’s reimbursement criteria are an insurance-based policy, which must consider the medical fee aspect of TKA unlike other appropriateness criteria that mainly aim to relieve patient symptoms. An improvement in the criteria will benefit a large group of potential patients that require TKA.

The decision on TKA candidacy should be dependent on the clinical status21, 22) of the patient and the current reimbursement criteria are excellent in taking into account age, radiological findings, and disease profile. However, patients younger than the age limit with advanced knee arthritis or those with severe knee pain and functional deterioration with limited treatment options should be able to undergo TKA. The activity level and life expectancy of the patients, as well as the longevity of TKA implants, are also the factors to consider when optimizing decision-making; elderly patients without severe knee symptoms or advanced radiologic findings could benefit from an efficient procedure such as TKA. Nonetheless, the HIRA’s reimbursement criteria are insurance-based and may differ from clinical indications. Although there is no universally accepted criteria for determining the appropriateness of arthroplasty, efforts in lowering the age limit and using clinical evaluation results such as KOOS pain and symptoms, WOMAC scores, and KKS score should be considered to optimize patient selection for primary TKA.

In terms of healthcare provision, HIRA’s reimbursement criteria are more effective than other TKA appropriateness criteria in providing access to patients who have the most pressing need for TKA. However, we found that the lower age limit and patient-reported outcome measures according to Riddle et al.’s1) or Hawker et al.’s5) criteria are useful in improving appropriateness of the current reimbursement criteria.