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Improving Results with Joint Injection

According to the results of this systematic review, studies show that accuracy of joint injections can be improved. In the shoulder, coming in from behind (posterior approach) is more accurate than from the front (anterior approach).

Additionally, the surgeon who uses ultrasound, fluoroscopy, or magnetic resonance imaging to guide the needle to the right spot will also be more accurate. And that was true for all joints (elbow, knee, or shoulder).

What's the purpose of these injections? Usually to reduce joint pain but also to improve function. The injection can be used to remove fluid from inside the joint (called aspiration) or to inject a numbing agent/steroid medication into the joint.

For this review, injection accuracy rates were the main focus. A secondary question was whether or not different joints can be accessed with greater accuracy than others. For example, is it easier to be more accurate injecting the knee or elbow compared with the more complex shoulder joint?

Turns out that needle placement accuracy is an issue only for the glenohumeral (shoulder) joint. Placement of the needle through portals (openings or channels through the skin down to the joint) for the knee, elbow, acromioclavicular (AC) joint, and subacromial space had the same accuracy rate.

The strength of the results of this review comes from the fact that when all other studies smaller in size but equal in measurement and design are combined, data can be compared and analyzed statistically. So for example, when comparing accuracy of needle placement for the shoulder, the results showed that accuracy improved from 45 per cent using the anterior approach to 85 per cent with the posterior injection.

Likewise, taking a look at a larger (combined) sample for accuracy with and without imaging to guide the surgeon showed differences of 79 per cent (without imaging) and 99 per cent (with imaging) for the knee. For the acromioclavicular joint, accuracy improved from 45 per cent (without imaging) to 100 per cent (with imaging). And for the subacromial space, accuracy improved from 63 per cent (no imaging) to 100 per cent with imaging.

But does improved accuracy mean better results? Accuracy and benefit in terms of patient outcomes are two separate things. Many studies have already shown evidence to support this idea.

People who receive joint injections often improve regardless of the accuracy of the needle placement. The placebo effect (patient expects to get better and does) may have as much of a role in results as accurate placement.

This particular systematic review did not include studies that reported patient results with location and/or accuracy of injection. Accuracy of results based on the type of imaging used was not evaluated either. The authors suggest future studies are needed to make such comparisons.

References: Erika L. Daley, BS, et al. Improving Injection Accuracy of the Elbow, Knee, and Shoulder. In The American Journal of Sports Medicine. March 2011. Vol. 39. No. 3. Pp. 656-662.

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