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Injections in the Athlete


General Principles

  • Knowledge of anatomy is essential in administering injections safely and effectively.

  • Use of local anesthetic injections in athletes may reduce the number of games missed because of injury but carries a theoretical risk of worsening the injury.

  • Corticosteroid injections are widely used in the treatment of athletic injuries because of their potent anti-inflammatory properties, but these are not without undesirable side effects.

  • Corticosteroid injections may not offer a clear therapeutic advantage over anti-inflammatory medications alone.

  • Both physicians and athletes should be aware of any restriction regarding the use of corticosteroids during a competition.

    • The World Anti-Doping Agency requires the completion of therapeutic use exemption before administration of corticosteroids.

    • The International Olympic Committee Medical Code requires that any team doctor wishing to administer corticosteroids to an athlete by local or intra-articular injection must give written notification to the relevant medical authority before the competition. A therapeutic use exemption is also required.

    • National Collegiate Athletic Association (NCAA) statement on corticosteroid injections: Corticosteroid injections should only be administered if a therapeutic effect is medically warranted and the student-athlete is not subject to any significant short- or long-term risks.

    • After careful consideration, the physician and athlete must determine that the benefits outweigh the risks before proceeding with an injection.

Sterile Technique For Injections

  • Mark the injection site by pressing the tip of a capped needle against the skin.

  • Prep the injection site with Betadine or another appropriate antiseptic solution.

  • Use prepacked sterile needles and syringes.

  • Use single-dose vials of an injectable agent whenever possible.

  • Change needles after drawing up the solution.

  • Wear sterile gloves.

Comfort Measures

  • Ethyl chloride is a topical spray that rapidly cools the skin, providing topical anesthesia.

  • Benefit of a subcutaneous local anesthetic may be limited by subcutaneous injection pain.

  • EMLA cream must be applied at least 1 hour before injection but has been shown to be highly effective.

Accuracy of Injection

  • Knowledge of surface landmarks and tactile feedback are essential for accurate needle placement.

  • Clinician experience alone does not necessarily improve the accuracy of an injection.

  • Joint aspiration in the presence of an effusion may assist in intra-articular needle placement but is not a guarantee.

  • Injecting 1–2 mL of air with the injection may help verify intra-articular injection of the knee or shoulder. The presence of an audible “squishing” with range of motion indicates a successful intra-articular injection.

  • Ultrasound guidance has been shown to improve the accuracy and clinical effects of certain injections in the hands of a skilled ultrasonographer.

  • Image guidance has not shown a definitive advantage over traditional techniques for most injections, although it may be useful in certain situations, such as in obese patients or in patients who have failed to respond to previous injections.

Common Agents

Local Anesthetics

  • Lidocaine (Xylocaine) is the most widely used anesthetic. Rapid onset of action with limited duration, approximately 30 minutes; maximum dose: 300 mg (30 mL of 1% lidocaine)

  • Bupivacaine (Marcaine) has a slow onset of action with prolonged duration of effect, up to 8 hours; maximum dose: 175 mg (70 mL of 0.25% bupivacaine)

  • A combination of lidocaine and bupivacaine allows the rapid onset of action with a prolonged duration of effect.

Corticosteroids

  • Less soluble

    • Methylprednisolone acetate (Depo-Medrol)

    • Triamcinolone acetonide (Kenalog)

    • Triamcinolone hexacetonide (Aristospan)

  • More soluble

    • Betamethasone sodium phosphate (Celestone)

    • Dexamethasone sodium phosphate (Decadron)

    • Prednisolone sodium phosphate (Hydeltrasol)

  • Dosage

    • Dosage requirements vary and should be individualized on the basis of the condition being treated and the response of the patient ( Table 62.1 ).

      Table 62.1
      Suggested Doses for Corticosteroid Preparations
      Corticosteroid Agent Large Joint Medium Joint Small Joint Soft Tissue
      Methylprednisolone acetate (Depo-Medrol) 20–80 mg 10–40 mg 4–10 mg 4–30 mg
      Betamethasone sodium phosphate (Celestone) 1.0 mg 0.5–1.0 mg 0.25–0.5 mg 0.5–1.0 mg

    • In chronic cases, injections may be repeated at intervals ranging from 1 week to ≥5 weeks depending on the degree of relief obtained from the initial injection.

    • No clear safety guidelines exist regarding the frequency and maximum number of injections. Judicious use of injections is recommended.

Mechanism of Action

Local Anesthetics

  • Membrane-stabilizing agents cause a reversible conduction block along nerve fibers.

  • Smaller nerve fibers are more sensitive, allowing inhibition of pain signals while sparing pressure and proprioceptive fibers.

  • Maximum plasma concentrations of local anesthetic are achieved within 10–25 minutes.

  • Avoid preparations containing epinephrine for intra-articular or soft tissue injections; epinephrine causes vasoconstriction, which prolongs the anesthetic effect when used in the skin.

Corticosteroids

  • Interfere with inflammatory cell-to-cell adhesion and migration through the vascular endothelium.

  • Inhibit the synthesis of cyclooxygenase-2 (COX-2) and various proinflammatory cytokines.

  • Stimulate gluconeogenesis and catabolic activity in muscle, skin, lymphoid, adipose, and connective tissue

  • Solubility determines duration of action and extent of systemic effects.

    • Insoluble: Average duration of action is longer for less soluble agents; primarily display local effects

    • Soluble: Diffuse more readily from the injected region and may exert greater systemic effects; may be more useful in extra-articular or soft tissue injections

  • Average duration of action is 1–3 weeks and is longer for less soluble agents.

Side Effects

Local Anesthetics

  • Anaphylaxis: Occurs from acute mast cell degranulation and is characterized by laryngeal edema, bronchospasm, and hypotension; the cause of local toxicity is allergic reaction to paraaminobenzoic acid (PABA). PABA is a metabolic product of the degradation of the ester class of local anesthetics, such as procaine (Novocain), and to a lesser extent, amide-class anesthetics such as lidocaine; it is also a metabolic by-product of methylparaben, a preservative in multidose vials of lidocaine.

  • Toxicity: Usually the result of inadvertent intravenous injection; primary target organ is central nervous system, resulting in altered speech, muscle twitching, and seizures. Cardiovascular toxicity (e.g., ventricular arrhythmias) may also occur. Aspirate before injection to avoid inadvertent intravenous injection. Compared with other local anesthetics, bupivacaine is markedly cardiotoxic.

  • Chondrotoxicity: Emerging evidence suggests that both lidocaine and bupivacaine may have negative effects on articular cartilage health and chondrocyte viability.

Corticosteroids

  • Postinjection flare: Most common side effect; related to steroid crystal synovitis; self-limiting; typically lasts for <12 hours; analgesic therapy and ice packs offer effective relief.

  • Facial flushing: Subjective sensation of warmth in the face and upper trunk

  • Poor diabetic control: May increase hepatic glucose production and antagonize insulin effects; close monitoring is suggested after a corticosteroid injection

  • Subcutaneous fat atrophy and skin depigmentation: May occur after a single injection; avoid repeated subcutaneous or superficial injections. Subcutaneous fat atrophy is particularly problematic in the plantar surface of the foot. Skin depigmentation occurs more commonly in dark-skinned individuals.

  • Tendon rupture: Dose-dependent decrease in tenocyte proliferation and reduced collagen production by tenocytes. Care should be taken to avoid direct intratendinous injection, which can result in this complication.

  • Steroid-induced arthropathy and cartilage damage: Destruction of articular cartilage and a decrease in cartilage matrix production has been shown in animal studies. Although not reported in humans, a theoretical risk remains.

  • Infection: Incidence of joint sepsis varies from 1 in 3000 to 1 in 50,000 for corticosteroid injections. Informed consent should be obtained before any invasive procedure. Use of good sterile technique minimizes this risk.

  • Anaphylaxis: May occur even after previous uneventful injections

  • Hypothalamic–pituitary–adrenal axis suppression: Suppression is mild and transient. Avoid simultaneously injecting multiple large joints. Prolonged suppression has been reported.

  • Drug interaction: Corticosteroids should be avoided in patients taking concurrent medications with significant liver enzyme CYP450 interaction, as this will affect corticosteroid clearance and may result in significant adrenal suppression.

Other

  • Syncope: Patients who feel lightheaded or overly apprehensive should lie down. Protect the airway in the event of loss of consciousness. Reassure the patient.

Contraindications

  • Infection: Overlying cellulitis, bacteremia, or septic arthritis

  • Fracture or unstable joint: Risk of worsening injury

  • Tendinopathy: Risk of tendon rupture if injected directly into tendon (e.g., Achilles tendon)

  • History of medication allergy or anaphylaxis after injection: Previous uneventful injection does not eliminate possibility of future reactions

  • Coagulopathy or anticoagulation therapy: Risk of bleeding at the injection site

  • Poorly controlled diabetes: Corticosteroids may result in temporary exacerbation of diabetes. Blood glucose levels typically peak 48 hours postinjection.

  • Medication use: Corticosteroids should be avoided in patients taking certain medications including the antidepressant nefazodone, antifungals (itraconazole, ketoconazole), protease inhibitors (ritonavir, cobicistat), and some macrolide antibiotics (clarithromycin, telithromycin) to prevent significant adrenal suppression and potential adrenal crisis.

  • Prosthetic joint: Risk of infection

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