Association Between Cutaneous Functional Units and Impairment Ratings After Burn Injury

Burn injuries can cause lasting functional impairment, often requiring formal impairment ratings for workers' compensation cases. Cutaneous functional units (CFUs), which represent skin areas involved in single-joint motion, may better capture functional impact than total body surface area (TBSA), yet they are not included in current impairment rating guidelines. This study evaluated relationships between initial TBSA, initial CFUs, final scar CFUs, and impairment ratings, hypothesizing that scar burden measured by CFUs would be strongly associated with impairment. A retrospective review was conducted of 78 burn patients with photographically documented TBSA and whole-body impairment ratings at maximum medical improvement at The South Carolina Burn Center at the Medical University of South Carolina. Initial CFUs were calculated from injury photographs using a previously established CFU map, and scar CFUs were calculated from scar photographs obtained at the time of impairment rating. Associations between TBSA, CFUs, and impairment ratings were assessed using Spearman's rho. Initial TBSA was significantly correlated with initial CFUs (rho = 0.471, p < 0.001) and more strongly correlated with scar CFUs (rho = 0.541, p < 0.001). Initial TBSA was also significantly correlated with impairment ratings (rho = 0.418, p = 0.002). Both initial CFUs (rho = 0.307, p = 0.006) and scar CFUs (rho = 0.569, p < 0.001) were significantly associated with impairment, with scar CFUs demonstrating the strongest relationship. These findings suggest that scar CFUs may represent a clinically relevant correlate of impairment ratings and warrant further prospective evaluation.