In order to save money and reduce my exposure to X-rays, I’m going to have an injection into my arthritic hip without the use of X-rays. My surgeon has done this procedure many times, so I feel confident it will go well. But just in case, I thought I’d check in and see what you think about this plan.

There 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. Doing the procedure without the benefit of imaging to guide needle placement is called blind injection. 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 a recent study say, not without some imaging assistance.

In their study, blind injection was accurate in placing the needle two-thirds of the time. But interestingly, only half the time did the injected agent show up inside the joint on arthrogram (dye injected into joint to show uptake of the injected agent). The chances of getting the agent inside the joint were definitely better when using fluoroscopy to guide the process.

Blind injection relies on something called backflow. The backflow method used with blind injection to confirm needle placement introduces the needle into the joint. A small amount of saline (salt) solution is injected into the area and then withdrawn to confirm correct needle placement.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.

According to this same study, 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 agent 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 most accurate technique may be using both fluoroscopy and arthrography.