Peripheral injections are among the most common procedures performed in an outpatient musculoskeletal medicine practice. Such injections serve a valuable role in the diagnosis and treatment of peripheral joint–mediated pain. Proper training, preparation, and technique is paramount to the performance of safe and effective peripheral joint and musculoskeletal injections.
Peripheral soft tissue or intraarticular injections commonly involve the injection of a local anesthetic in conjunction with corticosteroid. The local anesthetic is used to minimize the post-traumatic pain associated with joint or tissue needle penetration. In addition, the use of local anesthetic can serve a valuable diagnostic role during the immediate postinjection period by evaluating the injected structure as a pain generator. The use of a pain diary in conjunction with an injection can be particularly valuable in evaluating the degree and duration of pain relief obtained from the injected anesthetic. Steroids act as potent antiinflammatories; they can serve a therapeutic role in diminishing joint or tissue inflammation and can provide pain relief of longer duration. While local anesthetics generally take effect on the order of seconds to minutes, steroid injections often take several days to reach maximum efficacy.
For many injections it has become increasingly evident that surface anatomy landmarks alone are often not reliable enough for accurate needle placement, particularly in patients with suboptimal anatomy or body habitus. The use of image guidance in the form of fluoroscopy or ultrasound has become essential for the safe and accurate performance of many injection procedures, and the discussion that follows includes recommendations and technical considerations.
The first part of this chapter reviews basic principles of peripheral joint injection procedures. The second half describes individual joint and soft tissue injection techniques. Techniques for nerve blocks, neurolysis, trigger point injections, and spinal injections, as well as the diagnosis and pathogenesis of musculoskeletal conditions, are reviewed and discussed elsewhere in this text. The reader is referred to the index for these topics. In addition, a separate chapter is dedicated to the emerging role of ultrasound in musculoskeletal medicine (see Chapter 39).
PRINCIPLES OF PERIPHERAL JOINT INJECTION
Musculoskeletal injections most often involve the injection of two classes of medications: corticosteroids and local anesthetics. The local anesthetic results in immediate post-procedure pain relief, which may be useful for diagnostic purposes, and the steroid reduces inflammatory-mediated pain with longer duration of effect. Other commonly injected substances for musculoskeletal disorders include hyaluronic acid and, more recently, autologous platelet-rich plasma (PRP) or conditioned serum (ACS).
Local anesthetics act by reversibly blocking the axon sodium channels, preventing sodium ion influx and action potential generation. The degree and duration of neural blockade is dependent on the volume, concentration, and proximity to the targeted nerve. The addition of a sympathomimetic such as epinephrine reverses the inherent vasodilatory effect ...