Accuracy of Sonographically Guided Posterior Subtalar Joint Injections

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1 CME Technical Advance Accuracy of Sonographically Guided Posterior Subtalar Joint Injections Comparison of 3 Techniques Jay Smith, MD, Jonathan T. Finnoff, DO, Philip T. Henning, MD, Norman S. Turner, MD Objective. The primary purpose of this investigation was to determine the accuracy of 3 different sonographically guided posterior subtalar joint (PSTJ) injection techniques in an unembalmed cadaveric model. Methods. A single experienced examiner injected the PSTJs of 12 unembalmed cadaveric anklefoot specimens using the anterolateral, posterolateral, and posteromedial approaches. The injection order for each specimen was randomized, and each technique was completed with a different-color diluted latex solution. Coinvestigators blinded to the injection technique dissected each specimen and graded the colored latex location as accurate (in the PSTJ), accurate with overflow (within the PSTJ but also in other regions), or inaccurate (no latex in the joint). Results. All 3 sonographically guided PSTJ injection approaches accurately placed latex into the PSTJ (100% accuracy). Latex was also found in adjacent regions in 19.4% (7 of 36) of injections: 8.3% (3 of 36) within the tibiotalar joint, 8.3% (3 of 36) in the peroneal (fibularis) tendon sheath, and 2.8% (1 of 36) in the flexor hallucis longus tendon sheath. The anterolateral approach placed latex outside the PSTJ 25% of the time (3 of 12 injections: 1 tibiotalar and 2 peroneal [fibularis] sheath), the posterolateral approach 25% of the time (3 of 12 injections: 1 tibiotalar, 1 peroneal [fibularis] sheath, and 1 flexor hallucis longus tendon sheath), and the posteromedial approach 8.3% of the time (1 tibiotalar). Conclusions. This cadaveric investigation suggests that all 3 sonographically guided PSTJ techniques may be used to access the PSTJ with a high degree of accuracy. Clinicians should consider sonographically guided PSTJ injections as a favorable alternative to fluoroscopy and computed tomographic guidance when diagnostic or therapeutic image-guided PSTJ injections are indicated. Key words: ankle injection; hindfoot; sonography; subtalar. Abbreviations CT, computed tomographic; PSTJ, posterior subtalar joint Received June 22, 2009, from the Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine and Mayo Clinic Sports Medicine Center (J.S., J.T.F., P.T.H.), Rochester, Minnesota USA; Department of Radiology, Mayo Clinic Sports Medicine Center, Rochester, Minnesota USA (J.S.); and Department of Orthopedic Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota USA (N.S.T.). Revision requested July 13, Revised manuscript accepted for publication August 13, This work was funded by the Mayo Clinic Department of Physical Medicine and Rehabilitation Small Grants Program. Address correspondence to Jay Smith, MD, Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, E10, Mayo Building, 200 First St SW, Rochester, MN USA. smith.jay@mayo.edu CME Article includes CME test The diagnosis and management of posterior subtalar joint (PSTJ) pain remain clinically challenging. 1 5 Functionally limiting hindfoot pain arising from the PSTJ may result from chondral injury, osteoarthritis (idiopathic or posttraumatic), inflammatory arthritis, calcaneovalgus, tarsal coalition, or loose bodies. 1 3,5 8 However, pathologic processes arising from adjacent tendons, bursae, nerves, and osseous structures such as the tibiotalar joint and os trigonum may also produce hindfoot pain. 1,2,4,6,9 Prior research has shown that the history, physical examination, and radiographic findings are insufficient to accurately identify the PSTJ as the etiology of hindfoot pain. 5,9 11 Consequently, PSTJ injections have been used to support a clinical and radiographic diagnosis of a symptomatic PSTJ and facilitate therapeutic decision making. 1,3,4,5,8,9,12,13 Although 2009 by the American Institute of Ultrasound in Medicine J Ultrasound Med 2009; 28: /09/$3.50

2 Sonographic Subtalar Joint Injection nonguided techniques have been described, many authors recommend image guidance when performing PSTJ injections because of the joint s complex anatomy and tightly packed joint surfaces. 1,3 5,8,10,11,14 16 Furthermore, Remedios and colleagues 10 reported that fluoroscopically guided PSTJ injections provide more predictable and longer efficacy when compared with nonguided injections, explaining the observed differences based on injection accuracy. Multiple fluoroscopic approaches have been described for the PSTJ. 3 5,8 12,14,16 However, fluoroscopic approaches are limited by the inability to image nearby tendon and neurovascular structures, require expensive and at times cumbersome equipment, expose the operator and patient to ionizing radiation, and incur the additional risk of contrast agent reactions Even in experienced hands, up to 15% of fluoroscopically attempted PSTJ injections may fail to reach their target, typically because of distorted anatomy in the setting of posttraumatic osteoarthritis. 4,5 Computed tomographic (CT) guidance is considered the reference standard for image-guided intra-articular injections. 7 Although CT can identify nearby neurovascular structures, CT guidance is also limited by machine size, cost, and availability and also exposes the operator and patient to ionizing radiation. 7 In the only previously published report assessing the accuracy of CT guided PSTJ injections, experienced operators failed to reach their targets in 5% of cases. 7 Sonography has been increasingly used to guide diagnostic and therapeutic injections in the musculoskeletal system. 17,20 22 It can identify effusion and synovitis in the lateral PSTJ with greater sensitivity than the history, physical examination, and plain radiographs. 9,23 Surprisingly, only 1 previously published report specifically described a method to inject the PSTJ using sonography. 22 Koski 22 used a sonographically assisted technique (also called an indirect method) during which the skin overlying the lateral PSTJ in the vicinity of the peroneal (fibularis) tendons was marked using sonographic visualization. The injection was subsequently performed without sonographic guidance, but the skin mark was used to direct the point at which the needle was passed through the skin. 22 The accuracy of the technique was not reported, and a major limitation of the indirect method is the lack of real-time visualization of the needle passing into the articulation or one of its recesses. 17,20 22 Over the past 5 years, our practice has used direct sonographic guidance to inject the PSTJ using 3 different approaches: anterolateral, posterolateral, and posteromedial (P.T.H., J.S., and J.T.F., unpublished data, 2009). Prior anatomic research from our institution has shown that all 3 approaches provide access to the PSTJ while avoiding adjacent neurovascular structures (P.T.H., J.S., and J.T.F., unpublished data, 2009). However, the accuracy of these sonographically guided PSTJ injection techniques has not been formally documented. The primary purpose of this investigation was to determine the accuracy of sonographically guided PSTJ injections using the anterolateral, posterolateral, and postero - medial approaches in a cadaveric model. We hypothesized that all 3 techniques would be 100% accurate in placing injectate into the PSTJ. Documenting the accuracy of these techniques represents a necessary step to establish sonography as a favorable alternative to fluoroscopically or CT guided PSTJ injections when image guidance is indicated. Materials and Methods General Design The senior author (J.S.) injected 12 unembalmed cadaveric ankle-foot specimens (6 right side and 6 left side) using 3 different sonographic techniques: anterolateral, posterolateral, and posteromedial. All injections were completed in the Mayo Clinic Procedural Skills Laboratory, and cadaveric specimens were obtained through the Department of Anatomy s Mayo Foundation Bequest Program. Fresh-frozen specimens were thawed at room temperature immediately before the study. At the time of the investigation, the senior author had 5 years of experience in musculoskeletal sonography, including sonographically guided PSTJ injections. The project was approved by the Mayo Clinic s Biospecimens Subcommittee of the Institutional Review Board. Equipment All procedures were completed using an iu22 ultrasound machine with a 17 5 MHz linear array 1550 J Ultrasound Med 2009; 28:

3 Smith et al transducer (Philips Healthcare, Bothell, WA) and 25-gauge, 38-mm stainless steel needles. Injection Procedure Each specimen was injected by all 3 sonographic approaches. In all cases, only a single needle pass was required to complete each procedure. The injection order in each cadaver was determined by a computer-generated randomization scheme. Each injection was performed using a different-color liquid latex diluted with 50% tap water (anterolateral, yellow; posterolateral, blue; and posteromedial, pink) to facilitate determination of the accuracy of each approach. One and one-half milliliters of the diluted liquid latex was injected with each technique. Pilot studies indicated that mixing of injected latex colors did not preclude determination of intra- versus extraarticular injection. The 3 sonographically guided PSTJ injection techniques were developed by adapting previously described fluoroscopic and CT guided PSTJ approaches and have been detailed elsewhere (P.T.H., J.S., and J.T.F., unpublished data, 2009). The 3 approaches are summarized as follows: 1. Anterolateral. 3,4,6,8 The ankle-foot is positioned with its medial side facing down and supported on a towel or bolster to promote subtalar inversion. The entry point into the lateral PSTJ is identified by scanning posteriorly from the sinus tarsi, or anteriorly from the peroneal (fibularis) tendons. The lateral aspect of the PSTJ is identified just anterior (or superior) to the peroneal (fibularis) tendons, just anterior to the lateral malleolus. This location approximates the angle of Gissane, which has been used radiographically to identify the anterior aspect of the lateral PSTJ. 6,13 In this position, the transducer is positioned parallel but anterior to the calcaneofibular ligament. The peroneal (fibularis) tendons and accompanying sural nerve lie caudal to the joint at this level (P.T.H., J.S., and J.T.F., unpublished data, 2009). The position of the PSTJ is identified on the display screen. The needle is placed perpendicular to the long axis of the transducer (ie, a short-axis or out-of-plane approach) and directed anterior to posterior (Figure 1). The position of needle entry into the skin with respect to the long axis of the transducer is chosen to coincide with the position of the joint line on the display screen. The initial needle pass is shallow, identifying the needle tip by the appearance of an echogenic dot on the screen. Once the tip is identified, real-time sonographic visualization is used to guide the needle into the PSTJ. 2. Posterolateral. 2 4,6,14,16,24 26 The ankle-foot is positioned prone with the ankle dorsiflexed. The transducer is placed just lateral to the Achilles tendon in an anatomic parasagittal plane, medially angling the transducer face to identify the posterior tibial border, posterior talus, posterior talar process (or os trigonum), and posterior calcaneus. The PSTJ is clearly visualized between the posterior talus and calcaneus, often with a prominent PSTJ recess in pathologic condi- Figure 1. A, Lateral view of a skeleton ankle showing transducer and needle orientation for PSTJ injection from an anterolateral approach. Note the superior angulation of the needle to achieve colinearity with the slope of the PSTJ. Left is anterior; right, posterior; and top, cranial. B, Sonogram of PSTJ injection using the anterolateral approach showing the echogenic needle tip passing between the talus and calcaneus (CALC) using a short-axis approach. Note the peroneal tendons (PER), which lie inferior to the needle path. Left is cranial; right, caudal; and top, lateral. A B J Ultrasound Med 2009; 28:

4 Sonographic Subtalar Joint Injection tions. 3,14 The needle enters the skin at the caudal end of the transducer, colinear to the long axis of the transducer. Using this long-axis approach, both the needle shaft and tip can be visualized en route to the PSTJ. Real-time sonographic guidance is used to advance the needle just superior to the posterosuperior calcaneus, through Kager s fat pad, and into the posterior aspect of the PSTJ or its enlarged recess (Figure 2). The sural nerve and lesser saphenous vein lie anterior to the needle path (P.T.H., J.S., and J.T.F., unpublished data, 2009). 3. Posteromedial. 4,6,27 The ankle-foot is positioned with the lateral side facing down on a rolled-up towel or bolster to facilitate subtalar eversion. The transducer is placed in an anatomic coronal plane with the cranial end of the transducer on the medial malleolus and the caudal end imaging the sustentaculum tali. The anechoic space between the sustentaculum tali and talus represents the middle facet of the subtalar joint, which is contiguous with the anterior facet and forms the anterior articulation of the subtalar joint. 2,6 The subtalar joint line is followed posterior to the middle facet opening, revealing the anechoic medial aspect of the PSTJ. Typically, the posterior tibialis and flexor digitorum tendons are cranial, and the flexor hallucis longus, plantar nerves, and plantar arteries are caudal, providing access to the PSTJ in this region. Similar to the procedure used for the anterolateral approach, the PSTJ articulation is identified on the display screen, and the needle is advanced perpendicular to the long axis of the transducer (ie, short-axis or out-of-plane approach; Figure 3). The position of needle entry with respect to the long axis of the transducer is chosen to coincide with the position of the joint line on the display screen. The initial needle pass is shallow, identifying the needle tip by the appearance of an echogenic dot on the screen. Once the tip is identified, real-time sonographic visualization is used to guide the needle in to the PSTJ, the needle typically passing beneath the flexor digitorum longus or between it and the adjacent neurovascular bundle. of the technique used for each injectate placement. Injections were graded as accurate (in the PSTJ), accurate with overflow (in the PSTJ but also elsewhere), or inaccurate (no latex in the joint). Figure 2. A, Lateral view of a skeleton ankle showing transducer and needle orientation for PSTJ injection from a posterolateral approach. The transducer would be placed just lateral to the Achilles tendon with the face angled both medially and caudally as shown. Note the superior angulation of the needle to achieve colinearity with the up-sloping posterior aspect of the PSTJ. Left is posterior; right, anterior; and top, cranial. B, Sonogram of PSTJ injection using a posterolateral approach. Note the hyperechoic needle tip visualized in a distended posterior recess of the PSTJ. Arrows depict the shaft position within Kager s fat pad, which is poorly visualized due to isoechogenicity. CALC indicates calcaneus. Left is caudal; right, cranial; and top, superficial/posterior. A B Assessment At a minimum of 24 hours after injection, the coauthors dissected each specimen to assess injectate placement. The coauthors were unaware 1552 J Ultrasound Med 2009; 28:

5 Smith et al Results The accuracy results of the 3 injection techniques are presented in Table 1. All 36 sonographically guided injections successfully placed injectate into the PSTJ, resulting in an overall accuracy rate of 100% (36 of 36 total injections; 95% confidence intervals for each injection, 74% 100% accuracy). Latex was also found in adjacent regions in 19.4% (7 of 36) of injections: 8.3% (3 of 36) within the tibiotalar joint, 8.3% (3 of 36) in the peroneal (fibularis) tendon sheath, and 2.8% (1 of 36) in the flexor hallucis longus tendon sheath. Three of the 12 cadavers (25%) accounted for these latter findings. All 3 tibiotalar joint latex placements occurred in a single cadaveric specimen, suggesting the presence of a previously described communication between the PSTJ and tibiotalar joint. 1,3,4,11,14,24,25,27,28 In this same specimen, both the anterolateral and posterolateral approaches placed injectate into the peroneal (fibularis) tendon sheaths. In a second cadaver, the posterolateral approach placed injectate into the flexor hallucis longus tendon sheath, whereas in the third cadaver, the anterolateral approach resulted in flow into the peroneal (fibularis) tendon sheath. Considering the presence of injectate flow beyond the PSTJ based on the approach, the antero lateral approach placed latex outside the PSTJ 25% of the time (3 of 12 injections: 1 tibiotalar and 2 peroneal [fibularis] sheath) in 2 of 12 cadavers (16.7%). The posterolateral approach was quantitatively similar, although the 3 additional placements occurred in the tibiotalar joint (1), peroneal (fibularis) tendon sheath (1), and flexor hallucis longus tendon sheath (1). The posteromedial approach resulted in injectate placement outside the PSTJ on only a single occasion, producing flow into the tibiotalar joint in a single cadaveric specimen (8.3% of injections and 8.3% of specimens). and extracapsular ligaments, and is surrounded by tendons, nerves, and vessels. 2,3,6,9,15,27,28 The lateral PSTJ is shaped like a V (Figure 1), whereas the medial side is shaped like an inverted V (Figure 3). 2,15,27,28 This complex anatomy limits Figure 3. A, Medial view of a skeleton ankle showing transducer and needle orientation for a posteromedial approach to the PSTJ. Note needle passage superior and posterior to the sustentaculum tali entering the PSTJ via a short-axis approach. Left is posterior; right, anterior; and top, cranial. B, Sonogram of PSTJ injection using a posteromedial approach. The hyperechoic needle tip is visualized between the talus and calcaneus (CALC). In this particular case, the needle passed deep to the flexor digitorum longus tendon (FDL) on route to the PSTJ. This approach ensured that the needle passed from superficial to deep anterior to the tibial neurovascular bundle, with a position posterior to the flexor digitorum longus tendon. Left is cranial; right, caudal; and top, superficial/medial. A B Discussion The PSTJ is an articulation formed by the posteroinferior aspect of the talus and the posterosuperior calcaneus. 2 4,6,8,9,15,27,28 It is a complex planar joint allowing coupled 3-dimensional motion, is reinforced by a variety of intracapsular J Ultrasound Med 2009; 28:

6 Sonographic Subtalar Joint Injection Table 1. Posterior Subtalar Joint Injection Accuracy Injectate Location, % (n) Injection TT Peroneal FHL Outside Technique PSTJ Joint Sheath Sheath PSTJ Anterolateral 100 (12/12) 8.3 (1/12) 16.7 (2/12) 0 25 (3/12) Posterolateral 100 (12/12) 8.3 (1/12) 8.3 (1/12) 8.3 (1/12) 25 (3/12) Posteromedial 100 (12/12) 8.3 (1/12) (1/12) FHL indicates flexor hallicus longus; and TT, tibiotalar. safe access to the PSTJ for diagnostic or therapeutic injections, resulting in recommendations to use image guidance for needle placement into the PSTJ. 1,3 5,8,10,11,15,16 This study represents the first formal accuracy assessment for recently described sonographically guided PSTJ injection techniques (P.T.H., J.S., and J.T.F., unpublished data, 2009). Our results confirm that sonographic guidance can be used to inject the PSTJ with a high degree of accuracy. In our cadaveric model, all 3 sonographic techniques placed latex into the PSTJ with 100% accuracy. These results compare favorably with previously published accuracy rates for fluoroscopically and CT guided PSTJ injections. 4,5,7 In addition, compared with fluoroscopy and CT, sonography is widely available, is portable, lacks ionizing radiation, and provides detailed images of the adjacent tendinous and neurovascular structures at risk during PSTJ injections. 17,20,21,23 The 100% intra-articular accuracy rate for sonographically guided PSTJ injections is reassuring when performing an injection for therapeutic purposes. However, latex was discovered in adjacent regions after several injections, potentially raising concerns regarding diagnostic specificity. 1,14 Three explanations can be offered for the presence of latex in adjacent regions despite successful intra-articular placement. First, latex may have flowed out of the PSTJ and into the adjacent regions. Such communications have been documented in both asymptomatic populations and those with previous ankle injury. 1,14 The PSTJ has been reported to communicate with the tibiotalar joint in up to 22% of individuals. 1,3,4,11,14,24,25,27,28 We believe that such a communication existed in our single specimen in which all 3 PSTJ injection approaches resulted in latex being found in the tibiotalar joint. Although less common, PSTJ communications have been reported with the peroneal (fibularis) tendon sheath in 7% of asymptomatic individuals and the flexor hallucis longus tendon sheath in 13%. 3,25 Second, it is possible that the needle traversed adjacent regions en route to the PSTJ. This would be a highly unlikely explanation for latex in the tibiotalar joint but may explain latex in the peroneal (fibularis) and flexor hallucis longus tendon sheaths. Latex was found in the peroneal (fibularis) tendon sheath in 3 cases (8.3%), 2 occurring after an anterolateral approach and 1 after a posterolateral approach. Although the anterolateral approach does place the needle in proximity to peroneal (fibularis) tendon sheaths, the posterolateral approach does not (P.T.H., J.S., and J.T.F., unpublished data, 2009). The single flexor hallucis longus sheath injection occurred after a posterolateral approach. It is possible that a needle passing from lateral to medial during this approach not only can enter the posterior recess of the PSTJ but also can pass medially into the flexor hallucis longus tendon sheath. A third explanation for extra-articular latex may be the presence of ligamentous, capsular, or other pathologic conditions in our cadaveric specimens, resulting in abnormal communications between the PSTJ and adjacent structures. 1,3,4,11,14,24,25,28 Although our cadaveric specimens showed no overt signs of major trauma or deformity, we are unable to assess the impact of prior trauma on the flow of injectate into adjacent regions. In our opinion, the presence of extra-articular latex after successful PSTJ injection likely reflects normal communications between the PSTJ and adjacent regions. It is worth emphasizing that the presence of these communications is not specific to the sonographically guided techniques described herein because they have been reported after nonguided, fluoroscopically guided, and CT guided PSTJ injections with similar frequencies. 13 Nonetheless, clinicians performing sonographically guided PSTJ injections should be aware of the potential presence of these communications when interpreting injection results. Several technical considerations are noteworthy on the basis of our results and our clinical experience with sonographically guided PSTJ injections. First, it is advantageous to become comfortable with all 3 techniques described 1554 J Ultrasound Med 2009; 28:

7 Smith et al herein. In clinical practice, patients often have deformity, narrowed joint spaces, instrumentation, or overhanging osteophytes, all of which may limit PSTJ access using a single approach. 4 We prefer to initially visualize the PSTJ via the anterolateral and posterolateral approaches because of the relative ease of these techniques and the lack of proximity to major neurovascular structures (P.T.H., J.S., and J.T.F., unpublished data, 2009). Even if the joint space is poorly visualized, a distended lateral or posterior joint recess can be targeted for injection using these approaches. 3,4 As necessary, we have used the posteromedial approach, recognizing the potential for injury to the neurovascular bundle (P.T.H., J.S., and J.T.F., unpublished data, 2009). 4 Second, patient positioning is critically important. As previously described, ankle inversion will increase visibility of the PSTJ for the anterolateral approach, whereas eversion will facilitate joint access via a posteromedial approach. During the posterolateral approach, we typically maintain ankle dorsiflexion passively by placing our knee on the plantar surface of the patient s foot while performing the injection. Dorsiflexion usually widens the posterior joint space and improves the angle of needle passage via the long-axis approach into the posterior joint recess or the joint itself. 2,3,6,14,16,24 26,29 Third, as is the case with any procedure, safety is extremely important. Clinicians should be aware of adjacent neurovascular structures and proceed accordingly. We identify all adjacent tendons, vessels, and nerves as part of our preliminary scan while planning a procedure. The sural nerve and lesser saphenous vein are theoretically at risk using the anterolateral and posterolateral approaches (P.T.H., J.S., and J.T.F., unpublished data, 2009). Injury to the medial plantar nerve has been reported using a fluoroscopic posteromedial approach, which is not surprising given the close proximity between the needle and the neurovascular bundle (P.T.H., J.S., and J.T.F., unpublished data, 2009). 4,6,7 For this reason, we typically use the posteromedial approach as a last resort in our clinical practice. Fourth, when performing diagnostic PSTJ injections, we typically complete a preliminary scan of adjacent structures of potential interest: peroneal (fibularis) tendons, flexor hallucis longus tendon, tibiotalar joint, and lateral and posterior recesses of the PSTJ. We specifically note the presence or absence of fluid in these regions before the injection. Posterior subtalar joint injection volumes are typically kept low (2 3 ml), and injections are delivered slowly to better appreciate capsular distention and avoid overdistention. 3,7,14,16,24,27 After the injection, we reevaluate these regions. Distention of the lateral (for a posterolateral or posteromedial approach) or posterior (for an anterolateral or a posteromedial approach) recesses confirms PSTJ intraarticular injectate placement, whereas the absence of fluid in the adjacent regions (tendon sheaths and tibiotalar joint) provides some validation of the diagnostic specificity of the injection. The presence of fluid in the tendon sheaths or tibiotalar joint before or after injection is noted and considered in the interpretation of injection results. Several study limitations are noteworthy. First, clinicians may choose to exercise caution when extrapolating our cadaveric results to patients. However, we think that the precision of sonography and the ability to atraumatically direct the needle into the PSTJ would further favor sonography over previously described nonguided, CT guided, and fluoroscopically guided techniques when applied to patients who may have pain and anxiety during a procedure. Similar to our findings in cadavers, our clinical experience indicates that the PSTJ can be accessed with the chosen technique using a single needle pass in most cases. Prior authors have indicated the frequent need for multiple needle adjustments to access the PSTJ, reflecting the challenging nature of PSTJ injection. 13 Nonetheless, future investigators may consider sonographically guided PSTJ needle placement with fluoroscopic, contrast- controlled validation in patients referred for PSTJ injection. Second, our choice of 12 cadaveric specimens for this investigation may be considered a small number by some clinicians. It is unknown whether our 100% accuracy rate for each PSTJ injection approach would be achieved in a larger-scale study. Nonetheless, calculated 95% confidence intervals of 74% to 100% accuracy for each approach suggest a favorable degree of accuracy for the techniques described herein. Third, our cadaveric specimens were free from major deformity, prior J Ultrasound Med 2009; 28:

8 Sonographic Subtalar Joint Injection surgery, or severe arthritis. Prior investigators have reported reduced success in performing CT guided and fluoroscopically guided PTSJ in patients exhibiting these conditions. 4,5,7 Thus, it is possible that the accuracy rate of sonographically guided PSTJ injections may be similarly reduced when these conditions are present. Reassuringly, we have successfully performed sonographically guided PSTJ injections on patients with severe calcaneovalgus, limited subtalar motion, instrumentation, and tendon transfers. We believe the key to success in these cases is the flexibility that sonography provides to access the PSTJ or its recesses from a variety of directions while clearly visualizing neurovascular structures at risk. Fourth, all injections were performed by a single experienced clinician very familiar with sonographically guided PSTJ techniques. Although the techniques described herein are technically challenging, in our experience, those individuals familiar with sonographically guided procedures can learn the techniques after a few observation and mentoring sessions, optimally supplemented by cadaveric training where possible. In conclusion, this investigation indicates that 3 different sonographically guided PSTJ techniques may be used to access the PSTJ with a high degree of accuracy. Clinicians should consider sonographically guided PSTJ injections as favorable alternatives to fluoroscopy and CT guidance when diagnostic or therapeutic imageguided PSTJ injections are indicated. References 1. Lucas PE, Hurwitz SR, Kaplan PA, Dussault RG, Maurer EJ. Fluroscopically guided injections into the foot and ankle: localization of the source of pain as a guide to treatment prospective study. Radiology 1997; 204: Phisitkul P, Tochigi Y, Saltzman CL, Amendola A. Arthroscopic visualization of the posterior subtalar joint in the prone position: a cadaver study. Arthroscopy 2006; 22: Goossens M, DeStoop N, Claessens H, Van der Straeten C. Posterior subtalar joint arthrography: a useful tool in the diagnosis of hindfoot disorders. Clin Orthop Relat Res 1989; 249: Ruhoy MK, Newberg AH, Yodlowski ML, Mizel MS, Trepman E. Subtalar joint arthrography. Semin Musculoskelet Radiol 1998; 2: Mitchell MJ, Bielecki D, Bergman AG, Kursunoglu-Brahme S, Sartoris DJ, Resnick D. Localization of specific joint causing hindfoot pain: value of injecting local anesthetics into individual joints during arthrography. AJR Am J Roentgenol 1995; 164: Phisitkul P, Junko J, Femino J, Saltzman C, Amendola A. Technique of prone ankle and subtalar arthroscopy. Tech Foot Ankle Surg 2007; 6: Saifuddin A, Abdus-Samee M, Mann C, Singh D, Angel JC. CT guided diagnostic foot injections. Clin Radiol 2005; 60: Cahill AM, Cho SS, Baskin KM, et al. Benefit of fluoroscopically guided intraarticular, long-acting corticosteroid injection for subtalar arthritis in juvenile idiopathic arthritis. Pediatr Radiol 2007; 37: d Agostino MA, Ayral X, Baron G, Ravaud P, Breban M, Dougados M. Impact of ultrasound imaging on local corticosteroid injections of symptomatic ankle, hind-, and midfoot in chronic inflammatory diseases. Arthritis Rheum 2005; 53: Remedios D, Martin K, Kaplan G, Mitchell R, Woo P, Rooney M. Juvenile chronic arthritis: diagnosis and management of tibio-talar and sub-talar disease. Br J Rheumatol 1997; 36: Khoury NJ, el-khoury GY, Saltzman CL, Brandser EA. Intraarticular foot and ankle injections to identify source of pain before arthrodesis. AJR Am J Roentgenol 1996; 167: Ward ST, Williams PL, Purkayastha S. Intra-articular corticosteroid injections in the foot and ankle: a prospective 1- year follow-up investigation. J Foot Ankle Surg 2008; 47: Kirk KL, Campbell JT, Guyton GP, Schon LC. Accuracy of posterior subtalar joint injection without fluoroscopy. Clin Orthop Relat Res 2008; 466; Pavlov H. Ankle and subtalar arthrography. Clin Sports Med 1982; 1: Bilstrom E, O Rourke KS, Deodhar A. Injection of the subtalar joint and sinus tarsi. J Musculoskeletal Med 2008; 25: Taillard W, Meyer JM, Garcia J, Blanc Y. The sinus tarsi syndrome. Int Orthop 1982; 5: Balint PV, Kane D, Hunter J, McInnes IB, Field M, Sturrock RD. Ultrasound guided versus conventional joint and soft tissue fluid aspiration in rheumatology practice: a pilot study. J Rheumatol 2002; 29: Qvistgaard E, Kristoffersen H, Terslev L, Danneskiold- Samsøe B, Torp-Pedersen S, Bliddal H. Guidance by ultrasound of intra-articular injections in the knee and hip joints. Osteoarthritis Cartilage 2001; 9: Qvistgaard E, Christensen R, Torp-Pedersen S, Bliddal H. Intra-articular treatment of hip osteoarthritis: a randomized trial of hyaluronic acid, corticosteroid, and isotonic saline. Osteoarthritis Cartilage 2006; 14: J Ultrasound Med 2009; 28:

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