Musculoskeletal injections: technique



Musculoskeletal injections: technique

Mr. Harish Kurup

Consultant in Orthopaedics

Pilgrim Hospital, Boston

Steroids: mechanism of action

The mechanism of corticosteroid action includes a reduction of the inflammatory reaction by limiting 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. They also inhibit the release of arachdonic acid from phospholipids, thereby reducing the formation of prostaglandins, which contribute to the inflammatory process.

Sterile technique is recommended when performing injections. Use povidone iodine solution or chlorhexidine spray before injection. Use a mixture of local anaesthetic and steroid. Local anaesthetic may be short acting lignocaine or long acting bupivacaine. Steroid preparations in common use are Kenalog (Triamcinolone) or Depo-medrone (methyl prednisolone). Following the injection procedure, it is often helpful to ice the area. The increased tenderness often lasts 2 days and should be treated at home with ice. Tendon and joint injections generally are limited to no more than 3 per joint per calendar year because of the potential for altering cartilage metabolism. The risk of infection is small (estimated to be around 1 in 20,000).

Common injections given by family physicians are shoulder, tennis elbow, carpal tunnel, trigger finger, trochanteric bursa, knee and plantar fascitis.

Injection techniques

Shoulder

Injection of subacromial space for treatment of rotator cuff tendonitis and shoulder impingement syndrome is a common and useful procedure. This can also be used diagnostically. The posterolateral approach is as follows

• Palpate the posterior tip (angle) of the acromion, and insert the needle into the space between the acromion and the head of the humerus angling the needle anteriorly towards the coracoid process.

• Once in the space, draw back on the syringe to ensure that the needle is not in a blood vessel before injecting.

Tennis elbow

The injection technique for tennis elbow is as follows

• Palpate the lateral epicondyle.

• With the arm faced palm down and elbow flexed to about 45°, identify into the point of maximum tenderness around lateral epicondyle.

Inject the medication repeatedly withdrawing and redirecting the needle to infiltrate the area.

Carpal tunnel syndrome

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 and then a feeling of give way.

• Withdraw the needle slightly, and inject the medication. The patient may feel mild paresthesias in the distribution of the median nerve. Inject minimal amounts to prevent discomfort.

Trigger finger

First feel and locate the nodule in the triggering finger which is on the palmar aspect of metacarpo- phalangeal joint. The needle is inserted distal to this nodule in line with the flexor tendon and directed proximally at an angle of 30 0 towards the nodule. Make sure you are not injecting inside the tendon by asking the patient to actively flex the finger.

Trochanteric bursitis

The injection technique for trochanteric bursitis is as follows:

• With patient lying on the unaffected side, identify the point of maximal tenderness over the greater trochanter.

• Advance the needle until it gently contacts bone.

• Withdraw the needle minimally and infiltrate into the surrounding area in a fan-shaped pattern.

Knee

There are many different techniques for aspirating or injecting the knee. These include medial, lateral, and anterior approaches. Each has its own merit, but choice of approach is dependent on physician preference.

The lateral approach is most commonly used. For this approach, lines are drawn along the lateral and proximal borders of the patella with the patient lying supine. The needle is inserted into the soft tissue between the patella and femur near the intersection point of the lines, and directed at a 45 0 angle toward the middle of the medial side of the joint.

Some find anterior approach easier. With the patient sitting by the side of the bed with knee flexed 90 0 and feet hanging free, feel for the soft spot just lateral to patellar tendon. Angle the needle at 30 0 medially in relation to sagittal plane. (This is the entry point for knee arthroscopy and also less likely to hit the bone or cartilage)

Plantar fascitis

Even though the point of maximum tenderness in plantar fascitis is under the heel, do not inject from this side. Inject it from the medial side. Aim for the spur on Calcaneum which is usually deep to this tender spot. Inject only minimal amount of steroid and take care not to inject superficially into the fat pad (steroid injection into fat can cause fat atrophy).

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