Introduction

This section delves into the nuanced aspects of image-guided interventions in musculoskeletal medicine. Emphasizing the superiority of ultrasound-guided intra-articular joint injections, this approach significantly diminishes complication rates and bolsters accuracy, compared to blind injection techniques.

Intra-articular Joint Injections

• Ultrasound Guidance: This technology significantly improves accuracy, reducing potential complications. It’s particularly effective for joint injections, offering real-time visualization of the needle’s position.
• Diagnostic and Therapeutic Aspiration: These procedures are pivotal in managing conditions like septic arthritis or crystal deposition disease. Extracted fluid samples provide valuable diagnostic information.
• Diagnostic Nerve Block: A minimal amount of air and a localized anesthetic are injected to ascertain if the joint is the pain’s origin. The patient is observed for 24 hours, with a focus on the VAS score for pain assessment. The use of minimal local anesthetic is crucial to avoid potential chondrotoxic effects of drugs like Lignocaine and Bupivacaine.
• Therapeutic Injection: Involves an injectate containing a local anesthetic and corticosteroid. The precise composition and volume are carefully selected to manage pain and inflammation effectively while minimizing potential side effects.

Extra-articular Joint Injections

• Applications:
  1. Calcific and Non-calcific Tendinopathy: Techniques include percutaneous medial tenotomy/dry needling, PRP injections, prolotherapy, and barbotage. These are used for aspirating calcific deposits and treating various tendinopathies.
  2. Nerve Interventions: Peripheral nerve blocks under ultrasound guidance for surgical anesthesia. For example, a saphenous nerve block for lower leg surgeries.
  3. Bursitis/Tendon Sheath Injections: Ultrasound guidance enhances precision in injecting into the bursa or tendon sheath. This approach is especially advantageous for obese patients, where accurate needle positioning is crucial.
  4. Musculoskeletal Oncology Interventions: Tissue sampling under image guidance (ultrasound, CT/MRI, PET-CT) from suspicious soft tissue or bony lesions. Biopsy track planning is aligned with the surgical approach to facilitate future lesion removal.

Contraindications to Musculoskeletal Intervention

• General Safety Considerations: The non-vascular nature of most musculoskeletal interventions contributes to their safety profile. However, it’s critical to avoid neurovascular bundles and prevent tendon injuries.
• Relative Contraindications: Conditions like coagulation disorders, sepsis, and pregnancy (particularly for CT/MRI guided interventions) are considered relative contraindications.

Workup and Precautions

• Anatomical Knowledge: Profound understanding of ultrasound, CT, and MRI anatomy is essential for safe and effective intervention. Practitioners must be adept at interpreting these images for precise guidance.
• Pre-Procedure Preparations: Emphasizing asepsis is paramount. Routine blood tests are recommended, and PT INR may be necessary for patients with specific health conditions like cardiovascular or liver diseases. Antiplatelet medicines should be carefully managed, especially for patients undergoing treatments like PRP.

Types of Injections/Medications

1. Corticosteroids: Corticosteroid injections, like Triamcinolone Acetonide (Kenalog) and Methylprednisolone Acetate (depo-Medrol), are favored for their long-lasting effects. A typical corticosteroid injectate includes a suspension of Lignocaine 2% (9ml) and 1ml of a corticosteroid (40mg). Bupivacaine 0.25% is also utilized for its prolonged action. Some patients may experience of post-injection flare due to the increase in local inflammation in the acute phase.
   Despite their effectiveness, corticosteroids may have adverse biomechanical effects on tendons, especially in patients with chronic tendinopathy. Care must be taken to avoid inadvertent intratendinous injection, which could lead to tendon rupture. Additionally, corticosteroids might negatively impact articular cartilage, particularly in weight-bearing joints. Possible side effects also include skin depigmentation, fat necrosis, or skin atrophy following intradermal, topical, or subcutaneous injections.
   Triamcinolone is more effective than Methylprednisolone for intra-articular use. Some patients may also developed hyperglycemia in the insulin dependent diabetes mellitus from 2-4 days after injection. Facial flushing may also occur in few patients due to the Histamine induced response related to steroid injection which is mostly self-limited however in case of refractory symptoms antihistaminic medicines can be administered. Methylprednisolone should be referred for superficial joints or lesions.

   Absolute contraindications to steroids include systemic or local sepsis, joint instability, or fractures. Relative contraindications encompass coagulopathy or severe osteopenia. Post-injection follow-up is advised after 4-6 weeks, with a recommendation to avoid vigorous activity for 6 weeks and rest for 1-2 weeks.

2. Local Anesthetics: (such as Lignocaine, Lidocaine, and Bupivacaine) are water-soluble amides used for immediate pain relief and diagnostic feedback (also known as marcainization). Commonly employed in musculoskeletal interventions, these anesthetics are relatively safe with low chances of allergy. They can be used as a mixture of slow and fast-acting agents for more effective results. However, intra-articular use of local anesthetics should be avoided as they may cause chondrolysis and joint destruction.
3. Prolotherapy: This method involves injecting irritants to provoke an inflammatory response, using agents like phenol glycerine, hyperosmolar dextrose, and sodium morrhuate.
4. Hyaluronic Acid: Polysaccharide with high molecular weight and abundantly found in the extracellular Tissue Matrix; it is also a major component of cartilage as well as the synovial fluid in the joints. Hyaluronic acid injectate can be used in treatment of osteoarthritis which is refractory to medicines and can reduce pain significantly increasing the quality of life. Hyaluronic Acid injection can be given as a single injection per week in the joint for 4-5 weeks. A minimum period of 5 weeks is required for the patient to have good results with Hyaluronic Acid which can last up to 3-4 months. Hyaluronic Acid injected may also be combined with a long and short acting corticosteroid to produce better pain control.

Equipment for Injections

• Syringes: It is prudent to use only luer lock syringes as most of the musculoskeletal interventions involve injecting into the closed compartment and they provide and secure attachment with low risk of leak or contamination. Leur lock sizes which include 2.5, 5 mL. 5-10 mL lobe and ascitic syringes. 22 Gauge 90 mm spinal needle. Extension set having 3 cocks with connection of the needle as well as pharynges
• Needles: Needle size selection is critical. Smaller needles (22-27 gauge) are utilized for most intra- and extra-articular injections. Larger needles (18-20G) are reserved for aspirations of denser substances like abscesses or hematomas. Biopsy needles, including semi-automatic coaxial guns, facilitate multiple core samples with a single puncture.

Post-Injection Follow-Up

• Post-injection care involves avoiding strenuous activities for 6 weeks and resting for 1-2 weeks. A follow-up is typically scheduled after 4-6 weeks to evaluate outcomes and plan further management if necessary.
• Uncover the nuances of maximum dosage and effective delivery methods tailored to diverse patient needs. Grasp the significance of pH levels in the efficacy of anesthesia in inflamed tissues and learn about the differential sensitivity among nerve fibers that underscores the order of sensation loss.