الفهرس 
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Abstract
Platelet-rich plasma (PRP) is an autologous biomaterial obtained by centrifuging whole blood. Studies have shown that ideal concentration is at least a fourfold increase in initial concentration, or around 1,000,000/ mm3 .
Platelets are responsible for hemostasis promotion, new connective tissue formation and revascularization. A sample of whole blood usually contains 93 % red blood cells, 6 % platelets and 1 % white cells (leukocytes). Justification for the benefits of PRP rests on inverting the proportion of these cells in the blood, reducing the red layer to 5 %, since red blood cells are less useful in the healing process, and increasing platelets to 94 % to stimulate tissue regeneration.
Tendinopathies and cartilage disorders are difficult to manage. Their treatments are often only palliative, aiming to reduce pain. Traditional interventions include non-steroidal anti-inflammatory medications, corticosteroid injections, ice, rest, and bracing or immobilization. Unfortunately, most of these therapeutic options are limited in scope and target symptoms rather than the underlying disease. Along with new insights regarding tendon, cartilage, and intervertebral disc pathophysiology, a promising new era of biologically based cellular therapy has emerged. Orthobiologics involves the inclusion of biology and biochemistry in the development of bone and soft tissue replacement materials for skeletal and tissue healing.
The number of knee cartilage lesions (Osteoarthritis) is growing due to increased emphasis on physical activity in all age groups, and patient’s expectation with regards to recovery is also rising.
Unfortunately, the management of chondral disease is challenging because of its inherent low healing potential. In fact, the regeneration ability of cartilage is limited due to its isolation from systemic regulation and its lack of vessels and nerves. Biomechanical, metabolic and biological changes may lead to the loss of tissue homoeostasis, resulting in an accelerated loss of the articular surface and followed by end-stage arthritis .
Recently, platelet-rich plasma (PRP) injections have become an an option for treatment of osteoarthritis, particularly for the knee.
This treatment is appealing to patients because it involves the use of their own blood product and is not an exogenous substance like steroids or hyaluronic acid . Several evidence level 1 studies have shown good success with use of PRP.
Patellar tendinopathy is a common condition, often presenting with anterior knee pain. A thorough history and physical examination are necessary, but imaging can also aid in the diagnosis. The majority of cases resolve with nonoperative treatment. Once patients pass the initial inflammatory phase and remain symptomatic, treatment becomes more difficult.
PRP promote tendon cell proliferation and also tendon healing. It has been demonstrated that the healing tendon is responsive to the local application of growth factors and the fact that platelets secrete growth factors and active metabolites means that their applied use can have a
positive influence on damaged tissues with low healing potential. PRP is a method which provides many growth factors in a simple, low cost and minimally invasive way.
The third topic is anterior cruciate ligament (ACL) injury. ACL injury is one of the most common knee injuries.
Many studies were done to demonstrate the effect of use PRP during ACL reconstruction and the results were variable.
There are several studies that support the use of PRP products to augment ACL reconstruction in animal models, particularly when PRP is used in combination with a collagen-based carrier.
Still other studies show these combined PRP products to be ineffective. The difference in results may be explained, at least in part, by the different methods of preparation of PRP derivatives used in these studies. Still, the resultant controversy leads to a lack of consensus.