Background
Muscle strains are one of the most common injuries treated by physicians. Standard conservative therapy for acute muscle strains usually involves short-term rest, ice, and non-steroidal anti-inflammatory medications, but there is no clear consensus on how to accelerate recovery.
Hypothesis
Local delivery of platelet-rich plasma (PRP) to injured muscles hastens recovery of function.
Study Design
Controlled laboratory study. We used an established animal model of injury to test the effects of autologous platelet-rich plasma PRP on recovery of contractile function.
Methods
In vivo, the tibialis anterior muscles (TA) of anesthetized Sprague-Dawley rats were injured by a single (large strain) lengthening contraction or multiple (small strain) lengthening contractions, both of which result in a significant injury. The TA was injected with either PRP, PPP (platelet-poor plasma, as a sham treatment), or received no treatment.
Results
Both injury protocols yield a similar loss of force. The PRP only had a beneficial effect at one time point after the single contraction injury protocol. However, PRP had a beneficial effect at several time points after the multiple contraction injury protocol, and resulted in a faster recovery time to full contractile function. The sham injections had no effect compared to no treatment.
Conclusion
Local delivery of PRP can shorten recovery time after a muscle strain injury. Recovery of muscle from the high repetition protocol has already been shown to require myogenesis, whereas recovery from a single strain does not. This difference in mechanism of recovery may explain why PRP was more effective in the high repetition protocol, as PRP is rich in growth factors that can stimulate myogenesis. Since autologous blood products are safe, PRP may be a useful product to use in clinical treatment of muscle injuries.
Our results indicate that there is a significant correlation between estradiol, estriol, and progesterone and ACL stiffness suggesting that fluctuating levels of sex hormones may influence the stiffness of the ACL near ovulation. Future studies that examine the relationship between sex hormones and the physical properties of the ACL should be focused near the ovulation phase of the menstrual cycle.
An understanding of the anatomy and biomechanical features of the glenohumeral joint is necessary when understanding the concept of shoulder laxity. Glenohumeral laxity is a normal feature of shoulder motion, but only when that laxity becomes excessive does instability occur. The clinician must use the history and physical examination to distinguish normal from pathological laxity. Several examination techniques are commonly used to evaluate anterior, posterior, inferior, and multidirectional shoulder laxity. It has become appreciated the subluxation of the shoulder is clinically or symptomatically unstable. This paper reviews the current techniques to evaluate shoulder laxity and discusses the interpretation of these examinations as they relate to normal and pathological laxities.
Muscle strains, frequently the result of a lengthening contraction, sometimes are treated with corticosteroids. We tested whether an injection of dexamethasone administered soon after muscle injury would minimize inflammation and facilitate the recovery of contractile tension. We applied one eccentric contraction on the tibialis anterior of 76 rats, which were randomly assigned to one of three groups: sham-injured plus dexamethasone, injured plus vehicle, and injured plus dexamethasone. Electrophysiology, histology, and reverse transcription-polymerase chain reaction were used to study the relation between contractile tension, inflammation, and the expression of inflammatory molecules. The single eccentric contraction led to a reversible muscle injury characterized initially by reduced contractile tension and inflammation. The dexamethasone injection reduced the expression of interleukin-1beta and transforming growth factor-beta1 compared with injured vehicle-injected controls and led to a transient improvement of contractile tension 3 days after the injury. No adverse effects were seen for as much as 3 weeks after the dexamethasone injection. The data indicate that one dose of dexamethasone administered soon after muscle strain may facilitate recovery of contractile tension without causing major adverse consequences in this experimental model.
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