Syringes

All needles and syringes must be of single-use disposable type and must be checked to ensure they are in date. Have available 1 ml, 2 ml, 5 ml, 10 ml and 20 ml sterile syringes; occasionally a 50 ml syringe might be necessary for aspiration (Table 2.2).

Use a small-bore, 1 ml tuberculin syringe for small tendons and ligaments because the resistance of the structure can require a certain amount of pressure. Considerable back pressure can cause a syringe to blow off the needle, and thus the clinician and patient to be sprayed with the solution – an embarrassing situation. Always ensure the needle is tightly attached to the syringe.

Needles

Use a large bore, such as 21G, sterile in-date needle for drawing up the drug/s. The size of the infiltrating needle depends on the size of the individual patient – select the finest needle of the appropriate length to reach the lesion. Even on a slim person, it is often necessary to use a 3.5 inch (90 mm) or longer needle to successfully infiltrate deep structures such as the hip joint or psoas bursa. It is better to use a longer needle than might appear necessary than one that is too short, which could necessitate withdrawing and starting again. When injecting with a long, fine, spinal needle it may be useful to keep the trochar in place to help control the needle as it passes through tissue planes, and then attach the syringe when the needle is in place.

Corticosteroid

We suggest the use of Kenalog® (triamcinolone acetonide 40 mg/ml) throughout. This is a remarkably safe drug but any appropriate corticosteroid can be used. In our experience, Kenalog gives less post-injection flare than Depo-Medrone, particularly in soft tissues, and is equally effective. Another advantage is that Kenalog can be used in both small and large areas. Adcortyl (triamcinolone acetonide 10 mg/ml) is useful where the total volume to be injected is over 5 ml; this allows greater volume for the same dose and avoids the need to dilute the local anaesthetic further with normal saline – useful when injecting hip or knee joints. Depo-Medrone pre-mixed with lidocaine is commonly used but we find it more difficult to adjust for the individual lesion.

The effect of the corticosteroid does not usually kick in until about 48 hours after the injection, so the patient should be warned that they may not see any relief of pain until then. There is great variation in this time lag, some experiencing almost immediate improvement, others taking several days. The drug action continues for about 3 to 6 weeks.

In thin, dark skinned patients hydrocortisone may be used, especially when injecting superficial soft tissue lesions in order to avoid the potential risk of fat atrophy or depigmentation.

Local anaesthetic

We suggest the use of lidocaine hydrochloride throughout, but any suitable local anaesthetic can be used. Because of the risk of severe allergic reaction, the patient should be checked carefully for possible allergy to the drug before using any anaesthetic, for example previous dental work or skin stitches. Where any doubt exists do not use it. Normal saline can be used to dilute the corticosteroid if necessary.

Lidocaine with epinephrine, which comes in ampoules or vials clearly marked in red, should not be used because of risk of ischaemic necrosis in appendages (page 16). Because of its potential half life of 8 hours or more, we do not recommend the routine use of Marcain but occasionally it can be used when a longer anaesthetic effect is needed. Some practitioners like to mix short- and long-acting anaesthetics to gain both the immediate diagnostic effect and the longer therapeutic effect.

Dosages

The corticosteroid doses suggested are what we use for the average-sized adult and are governed by the individual patient’s age, size, general health and clinical history. These are guidelines only and none are ‘cast in stone’; it is up to the clinician to decide on variants depending on individual preference and patient presentation. At all times, the minimum effective dose should be given; this will help prevent the appearance of adverse side effects such as facial flushing, intermenstrual bleeding, hyperglycaemia, skin atrophy and depigmentation.

It is important to keep within the recommended maximum doses of local anaesthetic in order to avoid toxicity. The safe maximum doses we suggest are given in Table 2.3. These doses are half the maximum published in pharmacological texts, so are well within safety limits (BNF).