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Aspiration and Injection Techniques of the Lower Extremity
Christopher P. Chiodo, MD; Catherine Logan, MD, MBA, MSPT; Cheri A. Blauwet, MD
J Am Acad Orthop Surg. 2018;26(15):e313-e320.
Abstract and Introduction
Orthopaedic surgeons frequently use aspirations and injections to both diagnose and treat disorders of the lower extremity. Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques are essential. Clinicians must be well versed in a range of musculoskeletal aspiration and injection techniques, including patient positioning, equipment needs, injectable solutions, aspirate analysis, and potential complications. Safe and effective aspiration and injection techniques for the lower extremity, including the hip, knee, foot, and ankle, are reviewed. Image guidance modalities include fluoroscopy, ultrasonography, CT, and MRI.
Intra-articular and soft-tissue aspirations and injections are common procedures used by orthopaedic surgeons and other providers to assist in the diagnosis and management of lower extremity injuries and disorders. Successful outcomes rely on the clinician’s knowledge of pertinent local anatomy, appropriate indications, and awareness of evidence-based techniques that optimize accuracy and outcomes.
Arthrocentesis, or aspiration of synovial joint fluid, is indicated primarily for diagnostic purposes in the setting of acute synovitis, suspected infection, and chronic arthropathy. Repeated aspiration may be used in certain settings, such as with chronic, noninfectious effusions. Aspiration should always be performed before injection when clinical suspicion for septic arthritis exists. Aspirated synovial fluid should be analyzed for cell count with differential, Gram stain, microbiologic culture, and the presence of crystals.A preexisting diagnosis of rheumatoid arthritis, gout, or pseudogout does not exclude the possibility of concomitant infection. Therapeutic aspiration may be indicated in the setting of noninfectious effusions that limit range of motion or cause substantial pain. Such aspiration also may be indicated to drain a hemarthrosis or to drain a septic joint in patients with medical comorbidities that preclude surgical irrigation and drainage.
Joint or soft-tissue injections may be helpful for both the diagnosis and treatment of several musculoskeletal conditions. Injections are frequently used for targeted delivery of medication into joints, bursa, and tendon sheaths. Important contraindications exist. Injection and aspiration through cellulitic-appearing skin should be avoided when possible to minimize bacterial dissemination into the adjacent soft tissues or joint space. In addition, corticosteroids should not be injected into a joint until infection has been excluded. Injections in patients on anticoagulation or with a known coagulation disorder (ie, a relative contraindication) may be considered; however, a small-gauge needle should be used along with the application of appropriate manual pressure after the procedure. Furthermore, safe aspiration or injection can be performed on fully anticoagulated patients by using lidocaine with epinephrine as a local anesthetic. Complications are rare, and when they occur, they are often minor in severity (Table 1).
Sterile technique is critical to avoid infection and ensure accurate fluid analysis. At minimum, the injection site should be prepared with an alcohol- or iodine-based skin preparation solution. A sterile drape may also be used at the discretion of the clinician. If ultrasonography (US) guidance is performed, a sterile probe cover should be used, followed by cleaning the probe with antiseptic wipes after each injection and before use on subsequent patients. Sterile gloves should be worn by the clinician for all injections, including both palpation and image guided. The patient position varies by the intended target (Table 2). The needle gauge depends on the joint; large joints such as the knee may necessitate use of an 18- to 21-gauge needle, particularly if aspiration is planned, whereas smaller joints may be entered with a 20- to 25-gauge needle (Table 2). A spinal needle is often used with hips and deep shoulders. The syringe size varies based on the joint and effusion size, if present (range, 5 to 50 mL).
For certain injections, a growing body of evidence has demonstrated that image guidance may enhance accuracy and outcomes.[4–11] Multiple modalities are available, including fluoroscopy, US, CT, and MRI. Fluoroscopy with the use of intra-articular contrast has traditionally been used for therapeutic injections and aspirations of deep joints, such as the hip. With this technique, a small amount of iodinated contrast may be administered to confirm an intra-articular position of the needle. For the purposes of this review, the use of US will be emphasized, given its growing utility to provide image guidance in an office setting. US uses high-frequency sound waves to image soft tissues and bony structures and, because of advances in resolution capabilities, can, in most circumstances, detail tendons, nerves, ligaments, joint capsules, and muscles. Practitioners may perform both static and dynamic US imaging, depending on the clinical indication. Static US involves precise localization of structures, with the underlying tissue in a relaxed position, whereas dynamic US is performed during provocative testing and/or with the assistance of the patient moving a joint or contracting a muscle (eg, to evaluate tendon subluxation). The advantages of US over other imaging modalities include the absence of radiation and the ability to provide real-time guidance for interventional procedures in the office setting.
In patients with obesity, the soft-tissue envelope may be larger, especially with more central joints such as the hip. Targeted structures may, therefore, be deeper and anatomic landmarks less distinct, posing a challenge with regard to accurate needle placement. In our experience, the following measures are helpful in patients with obesity. First, a longer 3.5-inch spinal needle should be considered. Second, the provider should have a lower threshold for the use of image guidance. US imaging may be optimized with use of a lower frequency, curvilinear probe as well as optimizing the focal zone to target deeper structures. If image quality remains poor after US optimization, fluoroscopy or CT guidance should be considered as an alternative. Finally, immediate pain relief with the use of a local anesthetic in the injection solution may help confirm the accuracy of needle placement.
Hip and Knee Regions
Intra-articular hip aspiration is commonly used to assist in the diagnosis of infection.[13,14] Septic hip arthritis is more common in the pediatric patient; however, the incidence in adults ranges from 2 to 10 per 100,000 person-years.
Localizing the hip may be hindered both by body habitus and the inherently deep location of the joint. As such, image guidance, including fluoroscopy, CT, or US, is recommended. Anterior and lateral approaches have been described (Table 2). Smith et al evaluated the accuracy of US-guided intra-articular injections performed in 30 native adult hips. An anterior approach was used, and body mass index ranged from 20 to 39 kg/m2. The authors reported an accuracy rate of 97%, which was confirmed by contrast-enhanced fluoroscopic examination performed by an independent observer. Meanwhile, Mei-Dan et al investigated the accuracy and safety of hip injections without image guidance in 55 adults. The authors used an anterior approach, and the injections were performed before supine hip arthroscopy. The accuracy of needle insertion was assessed with an air arthrogram and by direct visualization with the arthroscope. A 93% success rate was reported, with female sex correlating with more difficult needle placement (P= 0.06). The proposed reasons for misplacement included a high-riding trochanter, increased femoral version, thick adipose tissue, and ilium morphology.
Aspiration of the knee joint may be performed to assist in the diagnosis of both infectious and noninfectious effusions. Corticosteroid injection into the knee is used for both diagnostic and therapeutic purposes in a noninfectious, inflammatory process. Commonly used approaches for knee aspiration include the suprapatellar, midpatellar, and infrapatellar approaches (Table 2).
The knee joint may be accessed using manual palpation alone or with image guidance (Figures 1 and 2). Curtiss et al evaluated the accuracy of US-guided and palpation-guided knee injections using the superolateral approach in a single-blinded, prospective study of 20 cadaver specimens. This study also compared the accuracy of a less-experienced clinician (ie, orthopaedic fellow) with a staff physician in the second decade of practice. US-guided knee injections were 100% accurate for both clinicians, whereas palpation-guided injections were markedly less accurate when comparing the fellow with the staff physician (55% versus 100%, respectively). A 2002 investigation by Jackson et al studied the accuracy of palpation-guided needle placement in 240 consecutive injections through three commonly used knee joint portals: anteromedial, anterolateral, and lateral midpatellar. Confirmation of placement was performed with fluoroscopy. The authors reported that a lateral midpatellar injection was intra-articular 93% of the time and was more accurate than injections using either of the other two portals (71% and 75% for the anterolateral and anteromedial approaches, respectively). In a systematic review of 429 injections assessing the injection site, Daley et al reported no notable difference between injection site approaches, with an average accuracy of 84% (range, 70% to 93%). With regard to imaging, an additional analysis of 660 knee injections, 75 of which were performed with image guidance (US), found that the accuracy of image-guided procedures was 99%, compared with 79% of injections performed without guidance. Chi-square with Yates correction yielded a Pvalue of <0.001 and relative risk of 1.246 (confidence interval between 1.392 and 1.117), supporting a statistically significant difference in the accuracy of image-guided versus nonguided injections.
Photograph showing the palpation-guided suprapatellar approach to the knee joint at the superolateral border of the patella
Photograph showing the ultrasonography-guided suprapatellar approach to the knee joint at the superolateral border of the patella.
Proximal Tibiofibular Joint
The proximal tibiofibular joint (PTFJ) consists of the articulation between the medial aspect of the fibular head and the proximal posterolateral tibia. It is a less common and potentially overlooked etiology of lateral knee pain. Pathology at this location may be due to arthritis, injury, compression of the common peroneal nerve, or a symptomatic ganglion cyst.[21,22] Injection of the joint may be conducted for diagnostic and therapeutic purposes and performed by palpation alone or with image guidance. Positioning the patient in the lateral decubitus position with the knee slightly flexed may facilitate needle placement (Table 2; Figure 3). Smith et al reported a comparison of palpation-guided injections and US-guided techniques for the PTFJ in a cadaver model. The authors reported 100% accuracy with image guidance versus 58% with a palpation-guided technique. Inaccurate placement was superficial and inferior to the PTFJ in all cases of unsuccessful injection, with extravasation into the adjacent musculature. Only two palpation-guided injections delivered all the fluid into the PTFJ (17%).
Photograph showing the ultrasonography-guided approach to aspiration or injection of the proximal tibiofibular joint.
Pes Anserine Bursa
The pes anserinus is a confluence of the sartorius, gracilis, and semitendinosus tendons onto the proximal anteromedial tibia. A potential bursa lies between the pes anserinus tendons and the more deeply located medial collateral ligament and/or medial tibia. Pain in the area of the pes anserine bursa is most commonly secondary to an inflammation of the bursa, tenosynovitis, or tendinopathy as a result of repetitive overuse or direct trauma. Injection may be considered as a diagnostic tool or as a treatment modality for recalcitrant pain.
The confluence and its bursa are best palpated on the anteromedial aspect of the proximal tibia. Alternatively, the tendons and bursa may be visualized using US. Patients are placed in the lateral decubitus position, with the knee slightly flexed to facilitate needle placement (Table 2). Despite the superficial location of the pes anserinus, unguided bursa injections have proved less accurate than US-guided injections. In a single-blinded, prospective study, Finnoff et al reported a markedly different accuracy of 92% versus 17%, respectively, when comparing the US-guided versus palpation-guided technique in adult cadaver specimens.
Foot and Ankle Region
The tibiotalar joint is a common site of arthritis, synovitis, osteochondral injury, and impingement. Both the anterolateral and anteromedial approaches to the tibiotalar joint are useful to access the joint (Table 2; Figure 4). The needle is placed just medial to the tibialis anterior tendon for the anteromedial approach and just lateral to the peroneus tertius for the lateral approach.
Photograph showing the palpation-guided anteromedial approach to aspiration or injection of the ankle joint.
With regard to the use of image guidance, Wisniewski et al found superior accuracy of US-guided versus nonguided anteromedial tibiotalar joint injections (100% versus 85%, respectively) in a cadaver model. Reach et al similarly reported 100% accuracy of US-guided anteromedial injections to the tibiotalar joint; however, no comparison group existed.
The subtalar (talocalcaneal) joint allows for inversion and eversion of the hindfoot. Three anatomic approaches have been described (ie, anterolateral, posterolateral, posteromedial), with the posterolateral often preferred because of its distance from neurovascular structures[5,9] (Table 2). Reach et al reported slightly less accuracy (90%) in their investigation of US-guided injection of the subtalar joint in the cadaver model. Henning et alevaluated the accuracy of three US-guided approaches (ie, anterolateral, posteromedial, posterolateral) to inject the posterior subtalar joint and found that all three approaches provided accurate needle placement while also minimizing the risk of needle entry into adjacent soft-tissue structures. In a comparison of the palpation-guided anterolateral and the posterolateral approach in 68 cadaver models, 23 (67.7%) of the anterolateral injections were successful compared with 31 (91.2%) of the posterolateral injections.The greater accuracy of the posterolateral approach was statistically significant (P = 0.016).
Peroneal Tendon Sheath
In the supramalleolar region, the peroneal tendon complex comprises the peroneus longus tendon and the more medial peroneus brevis muscle and tendon. As the complex courses distally, the peroneus longus courses posterior to the brevis tendon. Trauma to the tendons occurs from a forceful contraction of the muscles, with the foot in plantar flexion and inversion. Anatomic variations, such as a shallow or flat retrofibular groove, which houses the tendons as they course behind the fibula, may contribute to persistent or recurrent subluxation of the tendons. Tenosynovitis or tendinopathy occurs secondary to trauma or repetitive microtrauma. Anesthetic injections may be used for diagnostic purposes to assist in the clinical decision-making process and to assess for surgical appropriateness.
The patient is positioned supine, with the hip internally rotated and a towel roll placed under the medial aspect of the ankle (Table 2). Injections to the sheath are performed via palpation or with image-guided assistance. In one cadaver study, US-guided peroneal tendon sheath injections were markedly more accurate than palpation-guided injections (100% versus 60%, respectively). Accuracy is particularly important in the peritendinous injection to minimize the chance of an intratendinous injection, particularly if corticosteroid is used. Reach et al similarly reported 100% accuracy with US guidance for injections of the posterior tibialis and flexor hallucis longus tendon sheaths.
Midfoot and Forefoot
Khosla et al reported on the accuracy of intra-articular injections using palpation versus dynamic US in a cadaver model and reported 100% accuracy in subtalar and ankle joint injections in both techniques. However, using palpation, the needle was correctly placed into the first transmetatarsal joint in 3 of 14 cadavers, compared with 10 of 14 cadavers using US. Similar results were obtained with placement into the second transmetatarsal joint (ie, four with palpation versus eight with US).
The first metatarsophalangeal (MTP) joint comprises the articulation between the first metatarsal and the proximal phalanx of the hallux. Pain at the MTP joint may be acute or chronic in nature and the result of trauma, gout, or other inflammatory arthritides. Variation exists in the size and shape of MTP joints; therefore, palpation in the setting of conditions such as advanced degenerative arthritis may prove challenging. If necessary, distraction of the joint is helpful during needle placement (Table 2). Diagnostic aspiration or therapeutic injection may be useful in the management of advanced osteoarthritis, rheumatoid arthritis, and gout (Figure 5).
Photograph showing the ultrasonography-guided approach to aspiration or injection of the first metatarsophalangeal joint.
Few data are available on the comparison between palpation and image-guided techniques for injection or aspiration of the first MTP joint. Reach et al report 100% accuracy when using US guidance; however, this analysis was performed without a comparison group. Balint et al reported markedly lower accuracy rates in the conventional, palpation-guided technique for joint and soft-tissue aspiration compared with the US-guided technique. In the conventional group, successful aspiration was achieved in only 32% of the joints, compared with 97% of the aspirations in the US-guided group. The mean volume of fluid obtained with successful aspirations was similar in both groups.
Synovial Fluid Analysis
Joint fluid analysis is a useful diagnostic tool in the management of both septic arthritis and inflammatory disease. Analysis of the aspirate is critical in the treatment of adult septic arthritis because it guides antibiotic management. It also allows for the establishment of an accurate diagnosis in crystalline disease and guides management of inflammatory arthritis. The macroscopic appearance of synovial fluid provides immediate information to apply toward the differential diagnosis. The color, clarity, and viscosity can be appreciated on gross examination (Table 3). Synovial fluid specimens are placed in specimen containers specific to the test being ordered. A heparinized tube is preferable for cell counts, sterile containers for microbiology testing, and plain tubes for chemistry and immunological testing of the fluid. The volume aspirated from the joint may be small, and if only a few milliliters of fluid are available, preference should be given for cell count analysis. Normal synovial fluid is straw-colored, clear, and viscous. Increased inflammation changes the fluid’s macroscopic appearance; the color ranges from yellow to greenish yellow, the clarity is more opalescent, and the viscosity is decreased. In the setting of a pyogenic infection, the aspirate may appear as frank, purulent material. Bloody fluid may be the result of joint trauma, coexisting anticoagulation therapy, baseline coagulation disorders, or synovial tumors such as pigmented villonodular synovitis. The appearance of particles other than cells may indicate the presence of crystals. In rare instances, concomitant septic and gouty arthritis exists; therefore, early diagnosis requires a high level of suspicion because there may be an absence of fever or leukocytosis. Synovial fluid aspirate should be sent for cell count and differential, Gram stain, microbiologic culture, and crystal analysis, with results guiding subsequent management (Table 3). Of note, the cell count suggestive of septic arthritis in a prosthetic joint is much lower compared with a native joint. Additional biochemical studies, including the analysis of glucose, protein, and complement level, may be performed to provide further characterization of inflammatory arthritides.
Aspiration and injection of joints and soft tissues are safe and effective techniques for the diagnosis and treatment of musculoskeletal disorders. Intra-articular aspiration provides invaluable diagnostic information in cases of septic arthritis and inflammatory arthritides. Injection of local anesthetic may be of great utility for diagnostic purposes, and corticosteroid injections may be both diagnostic and therapeutic. Although correct needle placement in most of the peripheral joints of the lower extremity is routine in the hands of the experienced clinician, the use of image guidance to localize joint and soft-tissue structures may be beneficial. Correct needle placement has important implications for the administration of local treatment and underscores the significance of US as a useful device in clinical practice.
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