The Center for Medicare and Medicaid Services is faced with a challenge of decreasing the cost of care for total knee arthroplasty (TKA) but must make efforts to prevent patient selection bias in the process. Currently, no appropriate modifier codes exist for primary TKA based on case complexity. We sought to determine differences in perioperative parameters for patients with complex primary TKA with the hypothesis that they would require increased cost of care, prolonged care times, and have worse postoperative outcome metrics.
We performed a single-center retrospective review from 2015 to 2018 of all primary TKAs. Patient demographics, medial proximal tibial angle (mPTA), lateral distal femoral angle (lDFA), flexion contracture, cost of care, and early postoperative outcomes were collected. Complex patients were defined as those requiring stems or augments, and multivariable logistic regression analysis and propensity score matching were performed to evaluate perioperative outcomes.
About 1043 primary TKAs were studied, and 84 patients (8.3%) were deemed complex. For this cohort, surgery duration was greater (P < .001), cost of care higher (P < .001), and patients had a greater likelihood for 90-day hospital return. Deviation of mPTA and lDFA was significantly greater preoperatively before and after propensity score matching. Cut point analysis demonstrated that preoperative mPTA <83o or >91o, lDFA <84o or >90o, flexion contracture >10o, and body mass index >35.7 were associated with complex procedures.
Complex primary TKA may be identifiable preoperatively and those cases associated with prolonged operative time, excess hospital cost of care, and increased 90-day hospital returns. This should be considered in future reimbursement models to prevent patient selection bias, and a complexity modifier is warranted.

Patients with the β0/β0 type of β-thalassemia (β-thal) usually present as β-thal major (β-TM), and are transfusion-dependent. However, the clinical and hematological features of β-thal can be modulated by different modifiers, resulting in a wide range of clinical severity even in patients with the same genotypes. We report a Chinese family with twin brothers, both of whom had the same genotype of β0/β0. One twin was diagnosed as β-TM at 4 months of age and had regularly been transfused; conversely the other twin with a KLF1 (Krüppel-like factor 1) gene mutation, behaved as β-thal intermedia (β-TI), and had never been transfused. Our findings indicate that KLF1 mutations have a role in modulating the phenotypic severity of β-thal. The exact investigation of KLF1 modifiers is necessary in areas where globin gene disorders are most prevalent. This will be helpful in genetic counseling and optimizing the guidelines for prenatal diagnosis (PND) programs.