Injection therapy is used in musculoskeletal medicine to reduce pain and improve function. Substances injected include cortisone, hyaluronic acid and platelet-rich plasma. Traditionally, these injections have been performed by "landmark-guidance" ie by guiding the needle to the target of a joint or soft tissue structure based on surface anatomy landmarks. Increasingly, doctors and other practitioners are using image-guidance to help direct injections to the target to improve accuracy and effectiveness. But how more accurate and effective are image-guided injections compared to landmark-guided?
Image-guided injections can be performed by ultrasound or X-ray. There are many advantages to ultrasound-guidance including less cost and absence of exposure to radiation. In addition, ultrasound also has the advantage of being able to be performed in an office setting rather than a hospital or day surgical setting.
Evidence suggests that ultrasound-guidance is more accurate than landmark-guidance for the majority of joint and soft tissue injections including large and small joints. Those studies supporting accuracy have been performed on cadaver and live patients using a specific dye to confirm the correct placement of the injectate.
There is also evolving evidence for increasing efficacy of ultrasound-guidance compared to landmark-guidance. There is evidence that ultrasound-guided injections are more efficacious than landmark-guided in large joints, inflamed joints, SA-SD bursa, carpal tunnel, and first dorsal wrist compartment tendon sheath. There is limited evidence in a few studies that the systemic effects of corticosteroids provide similar therapeutic benefits to localised injections, but these studies need to be interpreted with caution due to significant limitations in the study methodology. Certainly, when one discusses injectable therapeutic agents that do not have demonstrable systemic therapeutic benefits (eg, viscosupplements, platelet-rich plasma), these injections would be ineffective if placed in the wrong region. Therefore, therapeutic benefit would be dependent upon correct injectate placement for these compounds. However, further research is required to determine if this hypothesis is correct.
Finally, there is some evidence that ultrasound-guidance is more cost-effective than landmark-guided injections. The preliminary findings of these studies suggest that USGIs are more cost-effective for large joints, inflamed joints, and carpal tunnel syndrome since more people responded to the USGIs, their improvement was greater and lasted longer than those who received LMGIs, and they utilized health care services less often following USGIs than LMGIs
So in summary, ultrasound-guided is significantly more accurate than landmark-guided injections. There is evolving evidence that ultrasound-guidance is more efficacious than landmark-guided. And there is preliminary evidence of cost-effectiveness of ultrasound-guided injections due to the improved efficacy and lowered requirement for health care services. In my opinion, while further higher-level studies need to be performed on efficacy and cost-effectiveness, there is enough evidence to justify the use of ultrasound to guide injections. Certainly, when combining the diagnostic advantages of point-of-care ultrasound with the evolving evidence of ultrasound-guided injections, there is a illuminating case for using ultrasound in day-to-day practice of musculoskeletal medicine.