Guidance During Needle Injection of Hip Joint RequiredThere are many instances when surgeons find it necessary to place a needle into the hip joint. Sometimes it's to diagnose a problem. In other cases, it's to treat the problem. For example, hip injections have been used to treat a painful hip after surgery, to deliver steroids to reduce inflammation, or antibiotics to fight infection.
In all cases, a needle is used to withdraw fluid from or deliver agents to the joint. How accurate is this technique? Can a surgeon really point and shoot -- that is to say, can the surgeon use anatomical landmarks to accurately place the needle in the joint? The authors of this study say, not without some imaging assistance. Let's take a look at how they came to this conclusion.
A small number of adults (16 men and women) with hip osteoarthritis participated in the study. They each received three separate hip injections, one week apart. The injection was hyaluronic acid used to coat the joint and aid smooth movement. Three methods were used to confirm needle placement in the joint: the backflow method, fluoroscopy, and arthrography.
The backflow method introduces the needle into the joint and a small amount of saline (salt) solution is first injected into the area and then withdrawn to confirm correct needle placement. If the surgeon is unable to aspirate (pull back out) the injected saline, the needle is not in the joint.
Fluoroscopy is real-time X-ray. The surgeon can see on a screen exactly where the needle is in relation to the joint as it moves through the skin and down through the soft tissues to the joint. Arthrography (arthrogram) relies on a dye injected into the joint to show that the injected agent actually made it inside the joint. Arthrography requires the use of fluoroscopy to see the contrast medium.
The study was set up so that first, the surgeon used anatomical landmarks to guide the needle into the joint. This is called a blind injection. A lateral approach (from the side) was used. Then, fluoroscopy was done to double-check the needle placement. And finally, an arthrogram was carried out to see if the injected hyaluronic acid made it.
Each injection was performed this way each time on each patient. The authors provide step-by-step details of how the injections, fluoroscopies, and arthrograms were done. Data was collected on the accuracy of each injection at each step.
Here's what they found. Blind injection was accurate in placing the needle two-thirds of the time. But interestingly, only half the time did the hyaluronic agent show up inside the joint on arthrogram. The chances of getting the agent inside the joint were definitely better when using fluoroscopy to guide the process.
Backflow was not reliable. In about 18 per cent of all cases, backflow was positive (suggesting that the needle was in the right place to deliver the agent) but the arthrogram was negative: no hyaluronic acid was actually in the joint. In these cases, the backflow method showed a false-positive response. And there were many other times (almost 80 per cent of all injections) when the arthrogram showed a correct needle placement but the backflow response was negative (not present). This is an example of a false negative.
The authors concluded that even though it is possible to perform a blind injection accurately, it is not a reliable technique. Backflow cannot be relied upon either. The expense saved and protection of the patient from X-rays may not be worth it if the procedure is a failure. Using fluoroscopy isn't enough either. It may show that the needle is correctly placed but doesn't definitely prove it as this study demonstrated.
The next step in further examining this problem is to repeat this same study with a larger number of patients to confirm the findings. The authors suggest using other means of confirming needle placement (e.g., ultrasound, MRI, CT scan) and comparing one technique to another to find the best one. More studies like this one using live humans (rather than cadavers) are also important.
Demirhan Diracoglu, MD, et al. Evaluation of Needle Positioning During Blind Intra-Articular Hip Injections for Osteoarthritis: Fluoroscopy Versus Arthrography. In Archives of Physical Medicine and Rehabilitation. December 2009. Vol. 90. No. 12. Pp. 2112-2115.
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