Radiographic parameter-driven decision tree reliably predicts aseptic mechanical failure of compressive osseointegration fixation.

Background and purpose - Compressive osseointegration fixation is an alternative to intramedullary fixation for endoprosthetic reconstruction. Mechanical failure of compressive osseointegration presents differently on radiographs than stemmed implants, therefore we aimed to develop a reliable radiographic method to determine stable integration.Patients and methods - 8 reviewers evaluated 11 radiographic parameters from 29 patients twice, 2 months apart. Interclass correlation coefficients (ICCs) were used to assess test-retest and inter-rater reliability. We constructed a fast and frugal decision tree using radiographic parameters with substantial test-retest agreement, and then tested using radiographs from a new cohort of 49 patients. The model's predictions were compared with clinical outcomes and a confusion matrix was generated.Results - 6 of 8 reviewers had non-significant intra-rater ICCs for ≥ one parameter; all inter-rater ICCs were highly reliable (p < 0.001). Change in length between the top of the spindle sleeve and bottom of the anchor plug (ICC 0.98), bone cortex hypertrophy (ICC 0.86), and bone pin hypertrophy (ICC 0.81) were used to create the decision tree. The sensitivity and specificity of the training cohort were 100% (95% CI 52-100) and 87% (CI 74-94) respectively. The decision tree demonstrated 100% (CI 40-100) sensitivity and 89% (CI 75-96) specificity with the test cohort.Interpretation - A stable spindle length and at least 3 cortices with bone hypertrophy at the implant interface predicts stable osseointegration; failure is predicted in the absence of bone hypertrophy at the implant interface if the pin sites show hypertrophy. Thus, our decision tree can guide clinicians as they follow patients with compressive osseo-integration implants.

Oncology Patients Are High Cost Outliers in Total Joint Replacement Bundled Payment Systems.

BACKGROUND: In 2016, the Centers for Medicare and Medicaid Services began its first mandatory bundled payment program, the Comprehensive Care for Joint Replacement (CJR) model, which covers a 90-day episode of care. This study determined whether oncology patients enrolled in the CJR bundle incur higher hospital costs than patients with osteoarthritis (OA). METHODS: A retrospective review of all patients enrolled in the CJR bundled payments system from April 1, 2016 to June 31, 2018 at a single academic medical center was conducted. To determine whether tumor patients had higher total episode costs, this group was compared to patients diagnosed with OA using a 2-tailed t-test. To adjust for moderators of total hospital costs, we used generalized linear regression with a log-link, including multiple variables abstracted from chart review. RESULTS: Three hundred fourteen patients met inclusion criteria (12 primary or metastatic tumors, 302 OA). Fifty-eight percent of tumor patients were over the target price vs 16% of OA patients. The mean tumor patient had $40,862 for total internal hospital costs compared to $16,356 in the OA group (P < .001). Length of stay was greater in the tumor group (6.75 vs 2.0 days, P < .001). A greater percentage of tumor patients were discharged to a skilled nursing facility (67% vs 27%, P = .006) with significantly higher skilled nursing facility episode costs ($18,852 vs $7731, P = .04). With adjustment for fracture status, tumor patients were 5.36 times more likely to exceed the CJR target price than OA patients (risk ratio 5.36, confidence interval 3.44-8.35, P < .001) and 50 times more likely to be outliers over the regional threshold than OA patients (risk ratio 50.33, confidence interval 16.33-155.19, P < .001). CONCLUSION: Oncology patients enrolled in the CJR bundled payment model incur significantly higher costs and have higher cost variability than patients with OA. We recommend that oncology patients be excluded from the CJR bundle.