Platelet Rich Plasma in Sports Injuries

Courtesy: Vijay Shetty, Hiranandani Hospital, Mumbai, India

Introduction

• PRP is widely used in sports medicine and orthopaedics.
• Many patients are already familiar with PRP because it is commonly used in:
  • Cosmetic medicine
  • Hair restoration
  • Sports injury treatment.
• The lecture aims to explain:
  • What PRP is
  • Biological mechanism
  • Evidence in literature
  • Practical use in clinical practice.

Platelet Biology

Platelet Characteristics

• Approximately 250 million platelets per mL of blood.
• Platelets contain intracellular granules with:
  • Growth factors
  • Cytokines
  • Bioactive proteins.

Biological Roles of Platelets

Platelets participate in:

• Hemostasis (clot formation)
• Immune modulation
• Tissue repair
• Regulation of inflammation
• Maintenance of physiological homeostasis.

Platelet research has been ongoing since the 19th century, but their application in orthopaedics is relatively recent.

Historical Development of PRP

1940s

• Discovery of growth factors and cytokines involved in tissue healing.

1980s

• PRP used for wound healing.

1990s

• Maxillofacial surgeons used PRP for mandibular fracture healing.

Early 2000s

• PRP adopted in orthopaedics and sports medicine.

Early Clinical Pioneers

• Surgeons previously used autologous clots in meniscal repair to enhance healing.

Definition of PRP

PRP is defined as:

• Autologous plasma containing platelet concentrations higher than baseline blood levels.

Earlier definitions required:

• Platelet concentration 3–5 times baseline.

Current definition:

• Any platelet concentration above baseline.

PRP Preparation

PRP preparation generally involves:

1. Blood collection
2. Centrifugation
3. Plasma separation
4. Platelet concentration
5. Injection into the target tissue

Preparation techniques vary between commercial systems.

Variability in PRP Systems

Multiple PRP systems exist with differences in:

• Centrifugation protocols
• Platelet concentration
• Leukocyte concentration
• Volume of final product

Because of these differences:

• PRP preparations are not standardized
• Clinical studies are difficult to compare.

Platelet Growth Factors

Key growth factors contained in PRP include:

• Platelet-derived growth factor (PDGF)
• Transforming growth factor-? (TGF-?)
• Vascular endothelial growth factor (VEGF)
• Epidermal growth factor (EGF)
• Insulin-like growth factor (IGF)

These factors contribute to:

• Cell proliferation
• Angiogenesis
• Tissue healing
• Inflammatory regulation.

Biological Variability

Platelet levels vary between individuals and within the same individual.

Factors affecting platelet concentration include:

• Time of day
• Physiological variation
• Health status.

This variability contributes to difficulty interpreting PRP studies.

Leukocyte Content in PRP

Two main types of PRP are recognized:

Leukocyte-Rich PRP

• Higher white blood cell content
• Produces stronger inflammatory response
• Previously considered beneficial for tendon healing.

Leukocyte-Poor PRP

• Lower leukocyte content
• Less inflammatory
• Currently preferred for most clinical indications, particularly intra-articular injections.

PRP Activation

Platelets contain intracellular vesicles with growth factors.

Activation releases these growth factors.

Methods of activation:

• Chemical activation
• Mechanical activation
• Natural activation after injection into tissues.

Current practice often relies on natural activation after injection.

PRP Preparation Systems

Regen System

Characteristics:

• Simple preparation
• Requires 8–9 mL blood
• Single centrifugation
• Uses a gel separator to remove RBCs and leukocytes
• Produces approximately 5 mL PRP

Advantages:

• Quick
• Office-based
• Less blood required.

EmCyte M-Site System

Characteristics:

• Double-spin centrifugation technique
• Requires ~60 mL blood
• Higher platelet concentration.

Procedure:

1. Blood mixed with sodium citrate anticoagulant
2. First centrifugation separates plasma
3. Plasma transferred to second container
4. Second centrifugation concentrates platelets
5. Final PRP volume ? 7 mL

Procedure time:

• Approximately 40–45 minutes including injection.

PRP Injection Technique

Injection Principles

• Knee injections may be performed without imaging guidance.
• Tendon and small joint injections are preferably done with:
  • Ultrasound guidance
  • Fluoroscopy
  • CT guidance.

Pre-Injection Steps

• Effusions should be aspirated before injection.
• Local anesthetics should generally not be mixed with PRP because they may reduce platelet activity.

Platelet Dose and Clinical Outcomes

Recent systematic reviews suggest:

• Higher platelet concentrations correlate with better clinical outcomes.

Reported findings:

• Positive outcome studies: ~ 5.5 billion platelets
• Negative outcome studies: ~ 2.3 billion platelets

However:

• Evidence remains heterogeneous due to variation in preparation methods.

Evidence in Clinical Conditions

Lateral Epicondylitis (Tennis Elbow)

• One of the most common indications for PRP.
• Systematic reviews show:
  • Small but statistically significant improvement in pain and function.

Rotator Cuff Tears

• PRP alone shows limited benefit.
• Better results when used adjunctively during surgical repair.

Knee Osteoarthritis

One of the most studied indications.

Comparative outcomes:

Treatment	Duration of effect
Corticosteroid injection	6–12 weeks
Hyaluronic acid	6–8 months
PRP	Up to 12 months

Evidence suggests PRP often:

• Outperforms corticosteroids
• Provides slightly better outcomes than hyaluronic acid.

PRP in Early Cartilage Degeneration

Potential benefits include:

• Reduction of inflammation
• Improvement in cartilage metabolism
• Symptom relief.

However:

• PRP is considered reparative rather than regenerative.
• True cartilage regeneration is not consistently demonstrated.

PRP in Muscle Injuries

Example: Hamstring injury

Systematic reviews show:

• No clear advantage over standard rehabilitation protocols.

Safety Profile

PRP is considered very safe because it is autologous.

Advantages:

• Minimal infection risk
• No systemic side effects
• No cartilage toxicity
• No metabolic complications compared with corticosteroids.

Post-Injection Protocol

NSAID Restrictions

NSAIDs inhibit platelet function.

Recommendations:

• Avoid NSAIDs 1 week before PRP
• Avoid for 3–7 days after injection

Paracetamol (acetaminophen) can be used for pain control.

Activity Modification

Evidence for activity restriction is limited.

Common recommendations include:

• Relative rest for several days
• Gradual return to activity
• Immobilization for tendon injuries.

Examples:

• Boot for Achilles tendinopathy
• Brace for patellar tendon injuries.

Clinical Outcomes

Typical clinical results:

• Approximately 70–80% of patients experience improvement.
• Improvement usually begins within:
  • 2–6 weeks after injection

If no improvement occurs by 6 weeks, further benefit is unlikely.

Emerging Research

Research areas include:

• Proteomic analysis of PRP components
• Identification of active proteins such as platelet factor-4
• Role of PRP in anti-aging and neurodegeneration research.

Animal studies suggest:

• PRP components may influence cellular aging and tissue repair pathways.

Future Directions

Potential developments include:

• Freeze-dried platelet preparations
• Standardized PRP formulations
• Targeted growth factor therapies.

Future research aims to determine:

• Which PRP components are responsible for clinical benefits.

Key Take-Home Messages

• PRP is a widely used orthobiologic therapy in orthopaedics.
• It involves injection of concentrated autologous platelets into injured tissues.
• Evidence supports its use mainly in:
  • Knee osteoarthritis
  • Lateral epicondylitis
  • Some tendon disorders.

Limitations include:

• Lack of standardization
• Variable platelet concentrations
• Heterogeneous clinical studies.

Overall:

• PRP is considered a safe and promising treatment, but further high-quality research is required.