BRINGING SCIENCE TO TREATMENT

Injection therapy: considering the finer points

Corticosteroid injections are widely used to aid injury rehabilitation but we still understand very little about their mechanism. Tracy Ward looks at the current thinking and discusses how this potentially impacts treatment options.

Corticosteroids are used for their anti-inflammatory and pain reducing effects. They can also reduce muscle spasms and influence local tissue metabolism for faster healing. Injection therapy is now widely available from specially trained general practitioners, physiotherapists and consultants, and can be offered for a wide range of clinical conditions. Because of this wide availability and the growing desire for injury “quick fixes”, it is important that they are used correctly and the full consequences are understood prior to injection.

The main indications for corticosteroid injection use are1:

  • Acute and chronic bursitis
  • Acute capsulitis (tight joint capsule)
  • Chronic tendinopathy
  • Inflammatory arthritis
  • Chronic ligament sprains

Steroid injections of hydrocortisone are a synthetic form of a naturally produced hormone within the body called cortisol. Cortisol is important for regulating carbohydrate, protein and fat metabolism. It is also involved in metabolic responses in times of stress such as emotional problems, trauma, and infection, where levels of inflammation are elevated. Steroid injections work on the immune system by blocking the production of chemicals that activate the inflammatory reactions, therefore reducing inflammation and pain within injury locations. Steroid injections can be directed into a joint, muscle, tendon, bursa, or a space around these structures (see figure 1). The location will depend on what tissue is causing the symptoms. When injected locally to the specific structure, the effects are primarily only produced there and widespread detrimental effects are minimal2.

Figure 1: Diagram showing the internal anatomy at the shoulder joint with an inflamed bursa. Injections aim to treat the bursa within the shoulder joint.

Figure 1: Diagram showing the internal anatomy at the shoulder joint


When to use

Identifying the correct time to issue a steroid injection following injury requires careful consideration. The mechanical status of the tissue is important because this will vary depending on the stage of healing and therefore the effectiveness of the injection will also vary (see figure 2). This is equally applicable to muscles, fascia, and other tissues too. Are active tendinopathy (tendon degeneration/damage) will present shortly after injury/trauma/stress/ excessive loading, and will display acute swelling and inflammation. The initial care should be 2-3 weeks of rest, analgesia, ice application and gentle physiotherapy. If symptoms have not significantly improved after this period, then the introduction of a corticosteroid injection is appropriate for providing symptomatic relief by reducing inflammation and eliminating the occurrence of further damage because mechanical normality will be quickly restored3.

Figure 2: Diagram showing the stages of injury to a tendon following excessive loading

Figure 2: Diagram showing the stages of injury to a tendon following excessive loading


If the tendon continues to be placed under excessive load, swelling and inflammation will remain or escalate, and continuous loading will eventually cause micro trauma and further tendon degeneration. If this is prolonged for long enough then the tendon will fail structurally4.

The use of corticosteroids here is questionable because there is unlikely to be inflammation present to combat, and the injection alone will not repair this physical damage. Injection treatment at this stage may only be indicated if the athlete is in too much pain to participate in any significant rehabilitation. The symptomatic relief the injection may bring at this point could allow exercises to be performed, which can help accelerate the repair of physical damage. Ultimately, physical exercise is a key component in recovery following corticosteroid injections.

Impact on treatment and performance

For the best outcome, post-injection care – particularly with respect to timing – is important. Relative rest is recommended for the first two weeks post-injection. During this first two weeks the tissues are weakened and their failing strengths are reduced by up to 35%; this means the strength at which they would fail (tear) is much lower and more susceptible to rupturing5.

By six weeks the biomechanical integrity is reestablished and the tissues are deemed ‘normal’ again, with increased strength and function6. Benefits are optimal within this 6-week period and often short-lived; therefore the athlete must comply strictly to a rehabilitation programme to gradually load the tissues and ensure the correct load is applied during this period7. Research has also shown that at twelve weeks post-injection there is little significance in the difference between those who received a steroid injection and those who focused on exercise therapy alone, suggesting this early symptom relief should be used to enhance rehabilitation8. If loading is accelerated in the early stages the athlete risks re-aggravation of the injury, delayed healing, further weakening and thus rupture.

If this rehabilitation protocol is followed, the athlete will likely maximise their outcome. They can return to training, and with the severity of their symptoms reduced, this can allow progression to the next stage of training. If the injury is severe enough that surgery may be considered within three months, a steroid injection should not be performed as this can affect the success of the surgery.

Side effects and risks
All invasive procedures carry side effects and risks. However if the athlete is screened correctly and appropriately selected for the injection then the risks are low. Below is a summary of the main issues to consider:
Side effects:

-Bleeding/bruising/pain at the injection site and surrounding area;

-Sepsis – figures report a 1 in 17 to 1 in 162,000 chance of developing local infection(5);

-Anaphylaxis – severe allergic reactions are very rare but caution should still be exercised(6);

-Skin depigmentation – skin colour changes and atrophy can occur in approximately 4% of cases but are rarely significant(7).
Risks:

-Corticosteroids are toxic to the cells that form cartilage and collagen, and their injection will inhibit collagen formation and cause death of these cells. This process can occur for the first 7 days post-injection(8). During this time the tissue rupture risk is increased. Healthy cartilage should never be injected as it may be detrimental to the healing process; therefore an accurate diagnosis is required promptly;

-If an injection fails to improve symptoms a second injection may be performed, but usually a maximum limit of three injections within one year is recommended. This may be because of these risks and on-going disturbance to the tissues, but also because it may suggest the injection is not the answer to recovery and additional rehabilitation methods should be explored to identify the root of the problem.

Evidence for sports injuries

Here we will consider some of the more common sports injuries and summarise what the current evidence regarding steroid injection suggests.

Shoulders

Injection therapy is indicated in subacromial impingement or bursitis  to allow the inflammation reduction and restoration of normal movement (see figure 3). It is also indicated in rotator cuff pathology where the tendons are again inflamed, but also damaged and unable to undergo exercise therapy. Shoulder injections are shown to produce early improvements in pain and function with a high level of patient satisfaction9. Symptoms are similar to those without injection at 12 weeks however, suggesting physical therapy is also important10. Injection is not appropriate for shoulder instability as it can make the joint more unstable. Exercise therapy alone is recommended for this condition.

Figure 3: Injection piercing the subacromial bursa within the subacromial space

Figure 3: Injection piercing the subacromial bursa within the subacromial space


Hip pain

Two soft tissue conditions that benefit the most from injection are piriformis syndrome (muscle tightness running deep to the buttock muscles), and greater trochanter pain syndrome (affecting the bursa surrounding the hip joint, or the gluteal tendons that are all in close proximity to the lateral hip)11. Injection success is reported to be approximately 60-100% if the diagnosis is accurate and the correct protocols are adhered to12. Other regions such as the adductor and hamstring tendons can also be treated for tendinitis or groin pains. However, injections into these regions are deep and painful, and require extensive rest afterwards.

Knee pain

Knee joint injections for arthritic conditions are most commonly used, with injection to the soft tissues much less common due to the complex diagnosis, and risk of detrimental side effects. The various bursa around the knee, the iliotibial band, and quadriceps and patellar tendons have all been shown to significantly benefit in the short-term; however accurate location is essential to ensure the tendon itself is not penetrated – only the surrounding regions13.

Plantar fasciitis

This is a painful injection to receive, and pain can last for well over one week post-injection (see figure 4). There is an approximate 2-4% risk that the fascia can rupture. In addition, there’s a risk of local nerve damage and wasting of the fat pad within the heel. Studies have demonstrated that at 4 weeks post-injection pain and thickness of the injured plantar fascia are reduced and these benefits remain three months later, suggesting a good outcome if the risks are avoided14.

Figure 4: Plantar fasciitis injection

Figure 4: Plantar fasciitis injection

Steroid injections – key facts
-Action primarily by reducing inflammation and alleviating pain at the injury site.
-Are shown to work best either during acute injury when rehabilitation is prevented because of pain, or when other treatment methods have failed and the condition has become chronic.
-Following injection, relative rest is required for the first 7-10 days, with minimal stress or load to the area.
-A structured exercise rehabilitation programme is needed for maximum benefits.
  1. Injection Techniques in Musculoskeletal Medicine, Stephanie Saunders. 2012; 4th Ed.pg 82
  2. BMJ. 2009;338:a3112 doi:10.1136/bmj.a3112
  3. J Musculoskel Med. 2008; 25: 78-98
  4. BJSM. 43: 409-416
  5. Am J Sports Med. 1976; 4(1):11-21
  6. Am J Sports Med. 1976; 4(1):11-21
  7. B J Gen Pract; 2002; Feb:145-152
  8. BMJ. 2010;340:c3037doi:10.1136/bmj.c3037
  9. BMJ. 2010;340:c3037doi:10.1136/bmj.c3037
  10. BMJ. 2010;340:c3037doi:10.1136/bmj.c3037
  11. J Muscuoloskel Med. 2009; 26:25-27
  12. Anesth Analg. 2009; 108: 1662-1670
  13. Oper Tech Sports Med. 2012; 20:172-184
  14. BMJ. 2012;344:e3260
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