# Association Between Rehabilitation Frequency and Functional Outcomes After Burn Injury: A Single-Center Retrospective Analysis of Confounding by Indication

## TL;DR

This study finds that mixed-depth burns are a major predictor of poor recovery outcomes in burn patients and highlights the need to account for confounding factors in rehabilitation research.

## Contribution

The study identifies mixed-depth burns as a high-risk clinical phenotype and demonstrates the importance of addressing confounding by indication in observational burn research.

## Key findings

- Mixed-depth burns strongly predict worse scar outcomes and failure to achieve full ROM.
- An apparent benefit of inpatient care for scar outcomes was due to confounding by indication.
- Longer therapy duration was the only significant predictor of achieving ADL goals.

## Abstract

Objective: To identify key predictors of clinical outcomes in burn survivors and clarify the role of mixed-depth burns and confounding by indication in observational rehabilitation research. Design: Retrospective cohort study using data from a burn rehabilitation registry (January 2024 to July 2025). Setting: Burn rehabilitation center. Participants: 120 adult patients (age ≥ 18 years) with burns affecting ≥1% total body surface area (TBSA) and complete baseline data. Interventions: Not applicable. Main Outcome Measures: Primary outcome was functional improvement (ΔFIM). Secondary outcomes included pain reduction (ΔPain), scar severity (Vancouver Scar Scale; VSS), Activities of Daily Living (ADL) improvement, and Range of Motion (ROM) recovery. Multivariable linear and logistic regression models were used to identify predictors. Results: Patients achieved significant improvements in function (mean ΔFIM = 11.3 ± 8.9 points) and pain (mean ΔPain = 1.28 ± 0.81). Having a mixed-depth burn was the strongest predictor of worse scar outcomes (β = 2.52, 95% CI: 0.93 to 4.12, p = 0.002) and failure to achieve full ROM (OR = 0.089, 95% CI: 0.008 to 0.930, p = 0.043). An apparent association between inpatient ward care and better scar outcomes (β = −1.30, p = 0.020) was determined to be an artifact of confounding by indication, as the outpatient group had a higher proportion of high-risk mixed-depth burns (6.2% vs. 3.5%). Longer therapy duration was the only significant predictor of achieving ADL goals (OR = 1.014, 95% CI: 1.002 to 1.026, p = 0.025). Conclusions: Injury characteristics, particularly the presence of a mixed-depth burn, emerged as the dominant predictors of long-term scar and functional outcomes. This study identifies mixed-depth burns as a potentially high-risk clinical phenotype requiring targeted therapeutic strategies and demonstrates the critical importance of accounting for confounding by indication when evaluating rehabilitation outcomes in observational burn research.