The Effect of Platelet-Rich Plasma (PRP) on Muscle Contusion Healing in a Rat Model.

Background: Current therapy for muscle contusions is usually limited to nonsteroidal anti-inflammatory drugs and/or use of the RICE principle (rest, ice, compression, elevation); thus, other forms of treatment that can potentially accelerate the rate of healing are desirable. Hypotheses: A local injection of platelet-rich plasma (PRP) would lead to accelerated healing rates compared with controls; also, delayed administration of PRP would lead to a blunted response compared with immediate treatment. Study Design: Controlled laboratory study. Methods: Forty-six male Lewis rats each underwent a single blunt, nonpenetrating impact to the gastrocnemius muscle via a drop-mass technique and subsequently received either a single injection of saline into the area of injury immediately after injury (controls, n = 11) or rat PRP (either immediately after injury [PRP day 0, n = 12], the first day after injury [PRP day 1, n = 12], or the third day after injury [PRP day 3, n = 11]). The primary outcome was maximal isometric torque strength of the injured muscle, which was assessed before injury as well as on postinjury days 1, 4, 7, 10, and 14. All animals were sacrificed on postinjury day 15. Histological and immunohistochemical analyses were performed on 6 specimens from each group after sacrifice. Results: The mean platelet concentration in the PRP was 2.19 × 106 (±2.69 × 105)/μL. The mean white blood cell count in the PRP was 22.54 × 103/μL. Each group demonstrated statistically significant decreases in maximal isometric torque strength after injury when compared with preinjury levels, followed by significant increases back toward baseline values by postinjury day 14 (controls, 90.6% ± 7.90%; PRP day 0, 105.0% ± 7.60%; PRP day 1, 92.4% ± 7.60%; PRP day 3, 77.8% ± 7.90%) (P = .121). There were no statistically significant differences between the treatment and control groups at any of the time points. There were also no statistically significant differences between any of the groups in the percentage of centronucleated fibers (controls, 3.31% ± 5.10%; PRP day 0, 0.62% ± 1.59%; PRP day 1, 3.24% ± 5.77%; PRP day 3, 2.13% ± 3.26%) (P = .211) or the presence of inflammatory cells and macrophages. Conclusion: In this rat contusion model, a local injection of PRP into the injured gastrocnemius muscle resulted in no significant differences in functional or histological outcomes, indicating no likely benefit to healing. Additionally, there was no significant difference between immediate or delayed administration of PRP. Clinical Relevance: Before PRP can be recommended for the treatment of muscle contusion injuries, further translational and clinical investigations need to be performed

Mark E A Novel Device to Apply Controlled Flexion and Extension to the Rat Knee Following Anterior Cruciate Ligament Reconstruction

We designed and validated a novel device for applying flexion-extension cycles to a rat knee in an in vivo model of anterior cruciate ligament reconstruction (ACL-R). Our device is intended to simulate rehabilitation motion and exercise post ACL-R to optimize physical rehabilitation treatments for the improved healing of tendon graft ligament reconstructions. The device was validated for repeatability of the knee kinematic motion by measuring the force versus angular rotation response from repeated trials using cadaver rats. The average maximum force required for rotating an ACL reconstructed rat knee through 100 degrees of flexion-extension was 0.4 N with 95% variability for all trials within 60.1 N