**12. Conclusion**

with the current understanding of the potential negative effects of inflammatory mediators on

Currently, it remains unclear what the impact PRP, with or without the presence of WBC, may have on the inflammatory cascade following muscle injury [37] In addition, each muscle has distinct anatomical and physiological characteristics, and as demonstrated in rabbit studies, also has distinct GF response profiles to injury. Thus, each location of injury may theoretically

Another dilemma is the method of PRP subministration. The physiological impact on an acute muscle injury of a bolus infiltration of an unknown concentration of platelets, and thus of GF, and other factors that are found in any PRP preparation is still a mystery. Animal studies suggest that a bolus dose of recombinant GF is not as effective as sustained release. However, with the current utilized technique, all GFs are released within 1 hour from their application

The timing of application is also a source of discussion. Apparently, the first ten days (inflam‐ matory and regenerative phases) after the lesion may constitute the ideal moment for PRP injection. An application two to three weeks after an injury, with an environment preferentially

Finally, although the physiological milieu should be sufficient to activate platelets, it is

In conclusion, the use of PRP is actually based on anecdotal reports and expert opinion (Level IV evidence). Further research is necessary in order to confirm or deny the effectiveness of PRP in muscle strain. However, the apparent safety and facility of application suggests that sport medicine practitioners should consider PRP when treating elite athletes, for whom such

Stem cells are biological cells found in all multi-cellular organisms that can divide (through mitosis) and differentiate into diverse, specialized cell types and can self-renew to produce more stem cells. There are three accessible sources of autologous adult stem cells in humans: bone marrow, adipose tissue (lipid cells) and blood. Scientists believe that stem cell therapy has the potential to significantly revolutionize medicine. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia. There is also the potential for a wider variety of diseases to be treated with stem cells (cancer, Parkin‐ son's disease, spinal cord injuries, Amyotrophic Lateral Sclerosis, Multiple sclerosis, and some forms of myopathies). Successful trials on the implantation of stem cells directly on detrusor muscle to treat urinary incontinence have opened the way to their use in muscle pathology. Clinical trials have commenced, but the clinical use of stem cells for the treatment of muscle strains is still for the future. One concern of stem cell treatment is the risk that transplanted

upregulated by platelet TGF-b a, may actually favor fibrosis over regeneration.

muscle healing.

164 Muscle Injuries in Sport Medicine

**11. Stem cells**

require different PRP preparations.

and this may potentially reduce their effectiveness.

unknown if a preinfiltration activation is necessary [38].

stem cells could potentially form tumors [39].

innovative approaches may be fundamental in terms of success.

Medical treatments of muscle injuries have limited scientific evidence. Their use is often based on level four studies and on personal clinical experience. While /immobilization/mobilization and RICE seem to be established protocols and "classic" treatment (NSAIDs, painkillers) appears to have a limited impact, the effectiveness of any new options for treatment has yet to be demonstrated in sport medicine. While further research is warranted, the sharing of clinical experience amongst sport medicine practitioners seems fundamental in order to perform the best "clinically-based" choices. Our personal experience is that patient reactions to medical treatments are often unpredictable. The same treatment applied to the same kind of lesion in different subjects may have a completely different outcome. However, in our personal clinical experience, oftenthe same patient reacts well to the same treatment when proven successful with a previous injury. The placebo effect component of treatment is undeniable, however there could also be benefits which are highlighted more in some patients and less in others. Our conclusion is that different techniques must be considered when approaching management of a muscle lesion, due to the fact that no one technique has a strong scientific evidence base to its effectiveness. The physician should try to tailor the therapeutic choice on the bases of the lesion's characteristics, the patient needs and expectations, and the subjective reaction to different treatments in the past. Of course, the basic Hippocratic principle of the treatment safety ("Primum, non nocere"), should be always respected, in particular when approaching these kind of lesions which have been proven to heal very well without any therapeutic intervention.
