Ultrasound-Guided Procedures

Introduction

The use of ultrasound guidance for knee procedures has become increasingly popular in recent years due to recognized increased accuracy compared with those performed blind, as well as an expansion in the range of both intra-articular and extra-articular knee therapies. * Indeed, in addition to aiding knee joint injections and aspirations, ultrasound guidance is widely considered the gold standard for localization in a range of procedures, including proximal tibifibular joint, patellar tendon, iliotibial band (ITB), popliteus tendon, pes anserinus bursa, Baker cyst, ganglia, and parameniscal cyst therapies, as well as biopsies.

* References .

This chapter will address the use of ultrasound in therapeutic and diagnostic procedures of the knee. The authors' technique for various procedures will also be described within the relevant sections.

Intra-Articular Procedures

Intra-articular procedures mainly include tibiofemoral joint aspiration and injection. Aspiration may be performed for therapeutic reasons (eg, to relieve the discomfort of a large effusion) or diagnostic reasons (eg, to sample fluid for potential infective, crystalline, or inflammatory etiologies). Injections may be performed for therapeutic intentions, such as with corticosteroid or viscosupplementation or for diagnostic purposes with arthrographic contrast. More recently there has been interest in the intra-articular injection of platelet-rich plasma (PRP) and mesenchymal stem cells.

Misplaced intra-articular injection (eg, during corticosteroid or hyaluronic acid injection) may produce reduced therapeutic effect if injected into periarticular tissue and even lead to increased post procedure pain. Inaccurate steroid injections can result in local fat atrophy and depigmentation, hematomas, steroid articular cartilage atrophy, or crystal synovitis. Misguided arthrographic contrast injection may result in a nondiagnostic study. There is also an increased susceptibility to tendon rupture by inadvertent intratendinous injection.

Numerous studies have demonstrated improved accuracy of intra-articular injections, with up to 96% accuracy with ultrasound guidance, increased responder rate to treatment, decreased pain scores, and even a reduction in overall cost per year, with ultrasound guidance. ^† Other studies have demonstrated the increased accuracy of ultrasound-guided extra-articular injections (eg, as much as 100% compared with 50% without guidance for the pes anserine bursa).

† References .

Multiple techniques for ultrasound-guided intra-articular injection of the knee joint have been described in the literature, with the lateral patellar and suprapatellar approaches being the most commonly used, ^‡ although a medial patellar approach was also described with the knee fully extended. The patient is usually placed in the supine position with a pillow or support under the knee so the joint is flexed to approximately 30 degrees. A high-frequency linear probe is used to scan the suprapatellar and lateral pouches for an effusion. If localized, this hypoechoic fluid collection becomes the target for the aspiration and injection ( Fig. 15.1 ). A subclinical effusion can usually be visualized under the quadriceps tendon proximal to the patella; therefore it is important not to overly compress with the transducer. Likewise, the trochlear cartilage can be targeted with a nondistended suprapatellar pouch. A needle pathway is predetermined; this area is then marked and prepped in a sterile fashion, lidocaine is administered subcutaneously, and subsequently a needle is then advanced into the joint recess or effusion. A test dose containing a small amount of local anesthetic can be used to confirm intra-articular needle tip placement. There should be minimal resistance encountered during injection, and hypoechoic fluid should be seen filling the suprapatellar and lateral pouches.

‡ References .

Corticosteroid Injections

Intra-articular injection of steroid is a well-established and common treatment for osteoarthritis of the knee. Improvement in symptoms of osteoarthritis of the knee after intra-articular corticosteroid injection varies in the literature, with effects generally lasting up to 16 to 24 weeks. Ultrasound also allows assessment response to intra-articular therapy in osteoarthritis of the knee.

Viscosupplementation

In 1997 exogenous high-molecular-weight hyaluronan viscosupplementation was approved to treat knee osteoarthritis in the United States by the US Food and Drug Administration (FDA). Viscosupplementation with intra-articular hyaluronic acid is an alternative to the treatment of symptomatic knee osteoarthritis in patients who have failed to respond adequately to conservative therapy and is frequently used due to ease of use and good tolerance. This has demonstrated moderate but significant efficacy (20%) versus placebo in terms of pain and function, with a high rate of responders (60% to 70%) in knee osteoarthritis. It may allow reduced administration of analgesics, with an improved risk to benefit ratio, and may delay joint replacement. A multitude of linear or reticulated hyaluronic acid derivatives are now commercially available, with varied characteristics and levels of evidence (eg, Gel-One Cross-linked Hyaluronate [Zimmer], Synvisc-One Hylan G-F 20 [Sanofi Biosurgery], Hyalgan [Fidia Pharma], Supartz [Bioventus], Orthovisc [DePuy], and Euflexxa [Ferring Pharmaceuticals]). Clinical efficacy shows onset 1 to 4 weeks later than with corticosteroids but is often maintained for 6 or even 12 months. The efficacy of viscosupplementation and optimal response profile is a matter of ongoing debate after discordant findings in some meta-analyses, and cartilage protection remains to be proven. The optimal indication seems to be moderate tibiofemoral osteoarthritis without swelling.

Contrast

Intra-articular injection of contrast agents may be used before computed tomography (CT) and magnetic resonance (MR) arthrography. The sensitivity in detecting recurrent or residual meniscal tears after surgery has been shown to be improved when intra-articular contrast material was used, compared with conventional magnetic resonance imaging (MRI). There has also been interest in the use of CT arthrography in the evaluation of the postoperative meniscus, as well as for assessment of cartilage and osteochondral allograft transplants.