Knee-attributable medical costs and risk of re-surgery among patients utilizing non-surgical treatment options for knee arthrofibrosis in a managed care population.

OBJECTIVE: To determine if differences in costs and risks of re-hospitalization and/or re-operation exist between arthrofibrosis patients treated with low intensity stretch (LIS) or high intensity stretch (HIS) mechanical therapies, or physical therapy alone (No Device). STUDY
DESIGN: This observational cohort study utilized administrative claims data to identify arthrofibrosis patients, age <65 years, with continuous enrollment for the 6 months prior to and following the index knee event date.
METHODS: The index knee event was defined as the knee injury/surgery preceding device use for the LIS and HIS groups and the knee injury/surgery prior to the diagnosis of arthrofibrosis for the No Device group. Knee-attributable medical costs (KAMC), accrued over 6-month pre- and post-index periods, as well as risks of re-operation, re-injury, and re-hospitalization were compared between groups. Multivariate models were used to evaluate group differences in utilization and costs when controlling for age, sex, and comorbidities.
RESULTS: A total of 60 359 patients (143 HIS; 607 LIS; 59 609 No Device) met the inclusion criteria. Unadjusted post-index KAMC were significantly less (p < 0.0001) among HIS patients ($8213 +/- 10 576) relative to LIS ($16 861 +/- 17 857) and No Device ($9345 +/- 14 120) patients. A significantly greater percentage of LIS Device patients had total knee replacements than HIS Device or No Device patients, and the LIS group had a significantly higher percentage of patients with musculoskeletal disease. When controlling for these group differences, the multivariate predictive model results were similar to the unadjusted results, with greater post-index KAMC for the LIS patients (24%, p = 0.025) and No Device (9%, p = 0.323) relative to HIS patients. No Device patients were 71% (p < 0.0001) more likely to have a subsequent knee event than HIS patients, and HIS patients had significantly lower rates of re-hospitalization than LIS and No Device patients (p < 0.0001).
CONCLUSIONS: Patients treated with HIS mechanical therapy demonstrated significantly reduced rates of re-hospitalization which corresponded to reduced knee-attributable medical costs. LIMITATIONS: Limitations of this study include those inherent in the use of retrospective claims data to identify the cohorts and for analytic purposes. The authors attempted to control for these as much as possible with the multivariate analyses, and inclusion of the model covariates specified above demonstrated a scaled deviance of 1.16 indicating a reasonable goodness-of-fit for the selected model covariates.