Soft Tissue Injury and Immobilization Are Both Required for Persistent Elbow Contracture in a Rat Model

Post-traumatic joint contracture commonly occurs after elbow injury. Although known as a risk factor for poor outcomes, immobilization is necessary to prevent reinjury. The objective of this study was to isolate the contribution of immobilization to mechanical and functional disability using an animal model. Left elbows of Long-Evans rats were immobilized in the absence (IM) or presence of an elbow injury (INJ+IM). Animals were immobilized for 21 or 42 days or immobilized for 21 days followed by free mobilization (FM) for 21 days. Uninjured animals without immobilization (CTRL) were also evaluated. Forelimb strength and gait were measured during FM, and joints underwent post-mortem mechanical testing. Contracture in 21IM elbows was moderate compared to CTRL but not as severe as 21INJ+IM. 42IM elbows were severely contracted compared to CTRL and not different from 42INJ+IM. 21IM/21FM mechanics were no longer different from CTRL while 21INJ+IM/21FM were still contracted. Gait was less altered for IM compared to INJ+IM and nearly returned to CTRL levels over time. Forelimb strength was not different between IM and INJ+IM but both were decreased compared to CTRL. For immobilization without injury, contracture took longer to develop but eventually reached levels of INJ+IM. Following remobilization, IM groups recovered faster and to a greater extent than INJ+IM groups. Thus, immobilization alone is not sufficient to recapitulate characteristics of human elbow PTJC (e.g., long-term loss of motion) in an animal model. Clinically, immobilization may not contribute to irreversible contracture development if duration is limited and strategic, active mobilization is provided.