Thứ hai, 13 Tháng 9 2010 16:44

Corticosteroid Injections of Joints and Soft Tissues

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Introduction

Use of cortisone injections in the treatment of muscle and joint inflammatory reactions is becoming increasingly popular. First popularized by Janet Travell, MD, muscle injections are a remarkably effective adjunct to pharmacologic and physical therapies and are safe and easy to perform. Joint injections, while technically more difficult to perform, also can be of great benefit in the patient's recovery. The purpose of this article is to introduce the basic principles of muscle and joint injections.

Mechanism of Inflammation 

Inflammation is one of the body's first reactions to injury. Release of damaged cells and tissue debris occurs upon injury. These expelled particles act as antigens to stimulate a nonspecific immune response and to cause the proliferation of leukocytes. Local blood flow increases to transport the polymorphonuclear leukocytes, macrophages, and plasma proteins to the injured area. A redistribution of arteriolar flow produces stasis and hypoxia at the injury site. The resulting infiltration of tissues by the leukocytes, plasma proteins, and fluid causes the redness, swelling, and pain that are characteristic of inflammation.

Inflammatory muscle and joint injuries are associated with many causes, including the following:

  • Muscle strains
  • Trauma
  • Polyarthritis
  • Connective tissue disease
  • Degenerative joint disease (DJD)
  • Tendinitis
  • Bursitis
  • Arthritis
  • Neoplasm
  • Inherited congenital disorders
  • Miscellaneous systemic diseases

Initially, the inflammatory reaction serves several important purposes. The influx of leukocytes facilitates the process of phagocytosis and the removal of damaged cells and other particulate matter. Pain and tenderness remind the patient to protect the injured area; however, the inflammatory reaction eventually becomes counterproductive. The extravascular pressure exerted by the edema may retard blood flow into the area and delay healing. Sometimes, the debris coagulates and forms hard masses, scarring, and/or trigger points in the muscle or joint, preventing normal function from returning

Actions of Corticosteroids

The mechanism of corticosteroid action includes a reduction of the inflammatory reaction by limiting the capillary dilatation and permeability of the vascular structures. These compounds restrict the accumulation of polymorphonuclear leukocytes and macrophages and reduce the release of vasoactive kinins. They also inhibit the release of destructive enzymes that attack the injury debris and destroy normal tissue indiscriminately.

Additionally, new research suggests that corticosteroids may inhibit the release of arachidonic acid from phospholipids, thereby reducing the formation of prostaglandins, which contribute to the inflammatory process. Finally, the clinician should appreciate the importance of introducing a needle into the injured area. The needle itself may provide drainage and a release of pressure, and it may also mechanically disrupt the scar tissue in the muscle.

Evaluation of the Patient

As with the treatment of any disorder, a carefully taken patient history and a carefully made physical examination are of paramount importance. Sharp, severe, intense pain suggests the presence of a more acute, traumatic reaction with marked inflammation. Dull, low-grade, chronic pain indicates the existence of a mild inflammatory reaction, a chronic overuse injury, or arthritis. Radiation of pain or additional neurologic symptoms (eg, tingling, burning, numbness) imply additional neurologic involvement. Medication history is important because discontinuation of anti-inflammatory medications often precipitates a reaction. Dietary changes also may precipitate reactions, such as an attack of gout.

The physical examination is performed to assess the location and severity of the reaction. Determination of whether the inflammation is in the muscle, tendon, or joint is of paramount importance. Trigger points in muscles can be easily identified if the clinician uses the appropriate palpation skills. Many clinicians ask their patients to identify the site of greatest discomfort. Patients often know exactly where the source of their pain is, having spent hours localizing it.

Radiographic studies may or may not be beneficial, because it takes a significant amount of effusion for the injury to appear on a routine radiograph. Usually, clinical symptoms are present and treatable long before a radiographic abnormality may be identified. On the other hand, radiographs are important in evaluating for fracture or determining acuity.

If joint and cartilage damage exists, the clinician knows that a long-standing process is involved. Electromyograms (EMGs) are extremely beneficial in determining whether there is a significant neurologic component to the patient's symptoms. This determination is important in targeting injection sites. Blood work can include blood counts and chemistry series. An elevated leukocyte or white blood cell count may indicate infection. An elevated erythrocyte sedimentation rate suggests that a significant myopathic or arthritic process has developed. Elevated rheumatoid factor implies chronic arthritic conditions, such as rheumatoid arthritis. Elevated uric acid levels are sometimes observed in patients with gout.

Treatment of the Patient

Treatment of the patient with an inflammatory condition involves a multidisciplinary approach. Anti-inflammatory medications (eg, aspirins, nonsteroidal anti-inflammatory drugs [NSAIDs], oral prednisone) are indicated in patients with acute and chronic inflammation. It should be remembered that a full therapeutic dose should initially be used. Many patients discontinue their medication after they have begun to feel better, leaving a low-lying inflammatory reaction. This author recommends first prescribing the NSAID for a 10- to 14-day period, with instructions to use up the medication as long as side effects do not develop. This should be followed up with an as-needed (prn) prescription.

Nonnarcotic pain medications, such as Elavil, may be beneficial in reducing the pain associated with inflammatory reactions. Although this is an area of some controversy, the use of narcotic medications is dependent on the severity of the pain, and these drugs should be used only for a limited duration.

In acute situations, rest, ice, heat, splinting, and bracing are important elements of care. With time, physical therapy, massage therapy, and general rehabilitation management become increasingly effective. While injection therapy is relatively safe, there are inherent dangers in any procedure where the skin is pierced, including infection, bleeding, joint ruptures, and perforation of vital structures. 

Indications for injection therapy may include any of the following inflammatory conditions:

  • Synovitis
  • Osteoarthritis
  • Bursitis
  • Gouty arthritis
  • Posttraumatic osteoarthritis (frozen shoulder syndrome)
  • Tendinitis
  • Rheumatoid arthritis
  • Muscle trigger points
  • Carpal tunnel and other entrapment syndromes                               
  • Fasciitis
  • Ganglion Cysts
  • Neuromas

Precautions for injection therapy include the following:

  • Charcot joint (neuropathic sensory loss)
  • Infection
  • Tumor
  • Neurogenic disease
  • Active infections (eg, tuberculosis)
  • Immune-suppressed hosts
  • Hypothyroidism
  • Bleeding dyscrasias
  • Uncontrolled diabetes
  • Joint prosthesis
  • Surrounding joint osteoporosis
  • Patellar or Achilles tendinopathies (possible tendon rupture)

The packing insert for corticosteroids lists additional significant precautions and contraindications. The physician should be familiar with all of these restrictions before considering injection therapy.

Potential local side effects of corticosteroid injections include infection, subcutaneous atrophy, skin depigmentation, and tendon rupture. These complications often result from poor technique, too large a dose, too frequent a dose, or a failure to mix and dissolve the medications properly.

Regarding injections for myofascial pain, some clinicians prefer to perform trigger point injections of corticosteroid, while others prefer to perform trigger point injections containing only local anesthetics or no medication at all ("dry needling").


Procedure

The procedure for injection therapy is uncomplicated and well established. The object is to inject the corticosteroid preparation with as little pain and as few complications as possible. The technique is similar for muscle, periarticular, or articular injections. Selection of the site and careful attention to surface and deep anatomy are of paramount importance. Injections in the vicinity of known nerve or arterial landmarks should not be attempted. For example, a lateral epicondyle injection is relatively easy. An injection into at the medial epicondyle (near the ulnar nerve) carries greater risk, and extra care must be taken to identify the nerve, outline its course, and avoid it.

Sterile technique is recommended when performing injections. This added care is needed to minimize the risk of iatrogenic infection and is especially important for intra-articular injections.

Opinions abound regarding whether to give a separate injection with just a local anesthetic (eg, lidocaine) prior to the corticosteroid injection. Some physicians prefer to give 1 injection (the corticosteroid preparation, perhaps mixed with a local anesthetic). Their rationale is that 1 needle is less painful than 2; however, the cortisone injection involves a thicker material, and therefore, a larger-gauge needle is used. Thus, this author prefers a 2-needle technique, feeling that this method is better tolerated by patients. The 2-needle technique starts with the physician anesthetizing the area with a small, 25-gauge needle and waiting 3-5 minutes for the anesthesia to take full effect; a larger-bore needle (21-22 gauge) is then used for the corticosteroid injection.

It should be remembered that the povidone-iodine solution should dry on the skin to have its full antibacterial effect. Just swabbing on the disinfectant and injecting increases the risk of infection. Another important tip is to consider changing the needle used to aspirate the medication into the syringe with the one used to do the injection, especially when using multidose vials. Finally, gentle distraction of the joint being injected may improve accessibility.

The material used for the injection is left to the discretion of the physician. Numerous philosophies and theories exist regarding the use of the different materials that are available. Many physicians prefer a simple, long-acting methylprednisolone preparation. This author prefers a cocktail consisting of equal parts of the following:

  • Lidocaine
  • Triamcinolone, which is intermediate acting (40 mg/mL)
  • Dexamethasone, which is long acting (4 mg/mL)

For muscle trigger point injections, the needle is inserted directly into the trigger point. The plunger should always be withdrawn to confirm that a blood vessel has not been penetrated before injecting the cortisone. The needle may remain in place but can be moved up and down and turned without withdrawing it from the skin. The needle should be angled into 3-4 areas of the trigger point.

It should be remembered that some of the benefit of the injection is the mechanical disruption of scar tissue. For periarticular injections, the injection should not be made directly into the tendon, lest the patient develop mechanical disruption or weakening of the tendon. Injection of the cortisone is accomplished in small droplets around the area of inflammation. Multiple injections may be required to infiltrate several centimeters of the tendon and muscle. Joint injections are accomplished by inserting the needle directly into the joint. Identification of joint injection sites is beyond the scope of this article, but information can easily be found in several guides to injection. This author's personal favorite reference for muscle trigger points is Myofascial Pain and Dysfunction:The Trigger Point Manual, by J Travell and D Simons.

Following the injection procedure, it is often helpful to ice the area. The injection itself is traumatic and results in swelling and edema, the very problems requiring treatment. Immediate icing of the area reduces this inflammatory response. The patient should be told what to expect. For the first 2 hours, the patient may feel quite comfortable because the area is numb from the local anesthetic. However, this lack of discomfort lasts only 2 hours and is replaced by increased pain that is often worse than the pain experienced before the injection.

The patient should be reminded that a needle has been stuck into a sore spot. This increased tenderness often lasts 2 days and should be treated at home with ice. By warning the patient up front of the level of pain to expect, the clinician can avoid many emergency calls. Obviously, the patient should also be cautioned that any unexpected symptoms (eg, excessive bleeding, allergic reactions, chest tightness, wheezing) should be evaluated immediately in an emergency department.

Frequently, multiple injections are required for comprehensive treatment of the patient. Typically, patients have multiple trigger points, and 3 sets of injections are required; however, it has been this author's observation that administration of up to 10 rounds of trigger point injections may be necessary. Each week, the patient may return with a new "worst spot." This phenomenon tends to be more common in patients with a chronic muscle disorder, such as fibromyalgia or a chronic pain syndrome. Tendon and joint injections generally are limited to no more than 3 in 1 joint per calendar year because of the potential for mechanical disruption of the joint space and structures.

Sibbitt et al found that in patients receiving intra-articular joint injections for pain, the use of ultrasonographic needle guidance appears to significantly improve performance and outcome. Their randomized study of triamcinolone acetonide injection into 148 painful joints showed that in patients who underwent ultrasonographically guided injections, when compared with those who underwent conventional, palpation-guided injections, procedural pain was reduced 43% (p <0.001), absolute pain scores at 2 weeks were reduced 58.5% (p <0.001), significant pain was reduced 75% (p <0.001), and the responder rate increased 25.6% (p <0.01).

Selected Joint Injection Techniques

Shoulder

Injection of the subacromial space for the treatment of rotator cuff tendinitis and shoulder impingement syndrome is a common and useful procedure. This can also be used diagnostically to differentiate between local and referred pain. The posterolateral approach, as follows, is safe and easy to execute:

  • Palpate the posterior tip of the acromion, and insert the needle into the space between the acromion and the head of the humerus.
  • Angle the needle anteriorly toward the coracoid process.
  • Once in the space, draw back on the syringe to ensure that the needle is not in a vascular structure. Resistance during delivery of the medication should be minimal.

Knee

  • Palpate the inferior medial aspect of the patella, and insert the needle into the space between the patella and femur, parallel to the inferior border of the patella.
  • Angle the needle to the center of the patella.
  • Aspirate any fluid before performing the injection.
  • Deliver the medication, and withdraw the needle.

Hand and wrist

After exhausting conservative treatment, injection is indicated for the treatment of carpal tunnel syndrome, as follows:

  • With the palmar surface of the hand facing upward, inject just proximal to the flexor crease and between the palmaris longus tendon and the flexor carpi radialis tendon. The needle should enter the skin at a 45° angle and be aimed toward the tip of the middle finger.
  • Advance the needle 1 to 2 cm until resistance is felt.
  • Withdraw the needle slightly, and inject the medication. The patient should have mild paresthesias elicited in the distribution of the median nerve. Volume should be minimized to prevent discomfort.

Elbow

The injection technique for lateral epicondylitis is as follows:

  • Palpate the lateral epicondyle.
  • With the arm faced palm down and elbow flexed to about 45°, identify a point about 1 cm superior and 1 cm distal to the lateral epicondyle.
  • Inject the medication into the point of maximum tenderness.
  • Repeatedly withdraw and redirect the needle to infiltrate the area.

Hip

The injection technique for bursitis of the greater trochanter is as follows:

  • The patient should lie on the unaffected side.
  • Identify the point of maximal tenderness, which typically is over the posteroinferior edge of the greater trochanter.
  • Advance the needle until it gently contacts bone.
  • Withdraw the needle about 0.25-0.5 cm, and administer a partial injection.
  • The remaining medication should be infiltrated into the surrounding area in a fan-shaped pattern.

Conclusion

The use of corticosteroid injections can be a useful addition to the treatments employed in treating musculoskeletal and joint injuries and pain. An injection regimen is most effective when combined with other pharmacologic and rehabilitation measures, such as the administration of NSAIDs, the use of stretching, and the employment of treatment modalities (eg, ice, heat). The injection of corticosteroids is a relatively safe procedure that can be managed by specialists and general practitioners alike. Treatment with corticosteroids has been a vital part of the practice of medicine for this author and can be used to benefit many other physicians and their patients.

Source emedicine.medscape.com

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