Physical Therapy Use, Costs, and Value for Latent Classes of Good vs Poor Outcome in Patients Who Catastrophize About Their Pain Prior to Knee Arthroplasty

Abstract

ObjectiveTo examine use, costs, and value of physical therapy (PT) among subgroups. DesignWe conducted an observational study of data from a randomized trial of a pain coping skills intervention. Good and poor outcome subgroups were determined based on Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) Pain and Physical Function scores. The use and costs of PT care as well as changes in WOMAC Pain and Physical Function scores over 4 time periods during a 1-year follow-up were reported. We compared the number of PT visits, total PT costs, and cost per 1-unit improvement in WOMAC scores for the 2 latent subgroups. SettingFive academic medical centers. ParticipantsPatients who catastrophized about their pain prior to knee arthroplasty (N=384). InterventionsPain coping skills training, arthritis education, and usual care. Main Outcome MeasuresThe WOMAC Pain Scale was the primary outcome. ResultsThe value of PT was lower and the cost of PT was higher for poor vs good outcome subgroups beginning 2 months after knee arthroplasty. For example, during the 2- to 6-month period, participants in the poor outcome subgroup incurred a PT cost of $5181.22 per 1-unit improvement in WOMAC Pain compared with $437.87 per 1-unit improvement in WOMAC Pain for the good outcome subgroup (P<.001). From the 6- to 12-month period, WOMAC scores worsened for the poor outcome subgroup, indicating no benefit from PT. ConclusionsPatients in 2 latent classes demonstrated clinically important differences in value of PT. Future research should identify rehabilitation-based interventions that reduce utilization and enhance effectiveness for patients at high risk for poor outcome.