Ninety-day readmission and early complications after coding-defined cementless-category versus cemented-category...

Use of cementless total knee arthroplasty (TKA) has increased in recent years, but contemporary short-term administrative comparisons with cemented fixation remain limited. This study compared 90-day readmission and early postoperative complications after ICD-10-PCS coding-defined cementless-category versus cemented-category primary TKA using a large U.S. administrative readmission database.

The 2020-2022 Healthcare Cost and Utilization Project Nationwide Readmissions Database (NRD) was queried for adults undergoing elective unilateral primary TKA for osteoarthritis. Only cases performed on hospital day 0 using common cemented and cementless ICD-10-PCS procedure codes were included. Fixation category was defined using ICD-10-PCS administrative procedure coding and was analyzed as coding-defined cementless-category versus cemented-category primary TKA. Non-elective admissions, bilateral procedures, revision or reoperation cases, fracture-, malignancy-, infection-, and COVID-19-related admissions, and index discharges after September were excluded. Readmissions involving contralateral knee arthroplasty were also excluded. Propensity-score matching was performed on the unweighted analytic sample, and DISCWT was applied after matching to generate weighted national estimates and proportions. The primary outcome was 90-day all-cause readmission. Secondary outcomes included intraoperative fracture, blood loss anemia, blood transfusion, stratified in-hospital complications, readmission burden, grouped primary causes of readmission, and grouped principal procedures performed during readmission.

The 1:1 matched analytic cohort included 23,140 unweighted admissions in each coding-defined fixation category. After applying DISCWT, these corresponded to weighted national estimates of 40,490 cemented-category and 40,501 cementless-category primary TKA admissions. Coding-defined cementless-category TKA was associated with a lower weighted 90-day readmission proportion compared with cemented-category TKA (5.17% vs 5.76%; OR 0.89, 95% CI 0.84-0.95; p < 0.001), as well as lower weighted proportions of blood loss anemia (11.28% vs 13.13%; OR 0.84, 95% CI 0.81-0.88; p < 0.001) and any in-hospital complication (13.55% vs 15.36%; OR 0.86, 95% CI 0.83-0.90; p < 0.001). Intraoperative fracture was more frequent in the cementless-category group (0.30% vs 0.18%; OR 1.67, 95% CI 1.25-2.23; p = 0.001). Blood transfusion rates were comparable between cohorts. Among readmitted patients, grouped primary readmission diagnoses and grouped principal procedures were heterogeneous and included infectious, wound-related, thromboembolic, cardiopulmonary, gastrointestinal, renal/urinary, mechanical/fracture-related, and other medical categories. Knee revision-related procedures represented only a minority of readmission procedures. In the revised age-centered interaction analysis, the fixation-category association at age 70 years was not statistically significant, while the fixation-category by age interaction remained significant.

In this U.S. nationwide propensity-matched administrative analysis of elective unilateral primary TKA, coding-defined cementless-category and cemented-category admissions demonstrated modest differences in selected early complications and 90-day readmission patterns. These findings characterize short-term administrative outcomes and should be interpreted in the context of coding-based fixation classification and the absence of implant-level, radiographic, functional, and long-term survivorship data.