Siêu âm trong chấn thương chỉnh hình

The Use of Ultrasound in Evaluating Orthopaedic Trauma Patients David B. Weiss, MD, Jon A. Jacobson, MD, and Madhav A. Karunakar, MD Abstract Musculoskeletal ultrasound is a low-cost, noninvasive method of evaluating orthopaedic trauma patients. It is particularly useful for patients with metallic hardware, which may degrade computed tomography or magnetic resonance images. Ultrasound has been used to evaluate fracture union and nonunion, infection, ligamentous injury, nerve compression, and mechanical impingement caused by hardware. Real-time dynamic examination allows identification of pathology and provides direct correlation between symptoms and the observed pathology. Dr. Weiss is Attending Physician, Department of Orthopaedic Surgery, St. Joseph-Mercy Hospital, Ann Arbor, MI. Dr. Jacobson is Associate Professor, Department of Radiology, University of Michigan Medical Center, Ann Arbor. Dr. Karunakar is Assistant Professor, Department of Orthopaedic Surgery, University of Michigan Medical Center. None of the following authors or the departments with which they are affiliated has received anything of value he use of ultrasound in ortho-paedics traditionally has been limited to evaluating hip dysplasia in newborns and, more recently, ro-tator cuff pathology in adults.1 Re-cent technologic advances, however, have provided improved image reso-lution, with increased accuracy in delineating anatomic structures and a broader range of possible applica-tions.2 Along with a decrease in cost and an increase in the number of trained ultrasonographers, these ad-vances have made ultrasound a valu-able alternative and/or adjunct to on static radiologic or MR images. Basic Principles A transducer crystal produces a sound wave that propagates through tissues beneath the transducer. The beam is reflected or refracted by the various densities of the underlying tissue, received by the transducer, converted into electric current, and displayed as an image. Bright echoes indicate large differences in density, such as with soft tissue–bone inter-face. Each tissue type has a charac- from or owns stock in a commercial computed tomography (CT) and teristic appearance on ultrasound, as company or institution related directly or magnetic resonance imaging (MRI). does metallic hardware, which indirectly to the subject of this article: Dr. Weiss, Dr. Jacobson, and Dr. Karunakar. Reprint requests: Dr. Karunakar, University of Michigan Medical Center, 2912 Taubman Center, 1500 East Medical Center Drive, Ann Arbor, MI 48109. J Am Acad Orthop Surg 2005;13:525-533 Copyright 2005 by the American Academy of Orthopaedic Surgeons. Volume 13, Number 8, December 2005 Ultrasound is particularly useful in the field of orthopaedic trauma,3 especially in the postoperative peri-od, when metallic hardware may sig-nificantly affect CT or MR images. At our institution, ultrasound has been successfully used to evaluate bone union and nonunion, bone and soft-tissue infection, and ligament pathology, as well as tendon sublux-ation and mechanical impingement about the ankle and foot. Dynamic ultrasound examination enables vi-sualization of pathology not evident makes it possible to discern individ-ual tissue layers with a high degree of accuracy.2 Anatomic structures also have characteristic features on ultrasound and are best demonstrat-ed when the beam is perpendicular to the structure.2 Ultrasound images are classified as hyperechoic (bright echo), isoechoic (intensity equal to the background or other reference structure), hypoechoic (dim echo), or anechoic (no echo).2 Tendons appear as hyperechoic, with a fibrillar echo-texture; the surface of bone is hyper- 525 The Use of Ultrasound in Evaluating Orthopaedic Trauma Patients Figure 1 Osseous union of a tibial fracture. Sagittal sonogram demonstrating continuous hyperechoic cortical bone (arrowheads) bridging the site of prior fracture (arrow). The skin surface and transducer are located at the top of the image. healing. However, the presence of metallic hardware can obscure evi-dence of healing. Objective findings, such as bridging of two or more cor-tices, lucencies around the plates and screws, or the absence of broken hardware, indicate that the fracture is stable and, presumably, healing. Unless tomography is done, radio-graphs may be nonspecific in evalu-ating fibrous or stable nonunions. Clinical findings, such as persistent pain at the fracture site, often are used in combination with radio-graphs to diagnose a nonunion. Ul-trasound cannot penetrate hardware, but the ultrasonographer can effec-tively position the probe to image the region of interest while avoiding metallic artifact.8 The presence of fibrous callus at the fracture site, particularly when it echoic, with shadowing; and muscle is relatively hypoechoic, with inter-spersed hyperechoic connective tis-sue.4,5 Peripheralnervesdemonstrate trasound machines usually are more accessible and less expensive than MRI equipment; some machines are portable. In the presence of metallic progresses over subsequent exami-nations, is suggestive of an ongoing healing process. As the callus ossi-fies, it will appear more dense on ul- a mixed hyperechoic and hypoecho- hardware, the probe may be adjusted trasound (equivalent to cortical ic appearance. Simple fluid is to visualize the area free of interfer- bone), a finding that may be identi- anechoic. Ultrasound machines of-ten include an extended field-of-view option, which allows visualiza-tion of an entire muscle or muscle group to assist in accurately charac-terizing the full extent of patholo-gy.6 Ultrasound Versus Magnetic Resonance Imaging and Computed Tomography After plain radiography, MRI is the most common technique for evalu-ating musculoskeletal pathology (es- ence, enabling a dynamic examina-tion with correlation of symptoms. Resolution in the newest transduc-ers approaches 200 to 450 µm, a lev-el at which MRI requires special sur-face coils and techniques. Ultrasound provides valuable ad-ditional information but does not necessarily replace CT and MRI, making it a useful adjunct to these studies. Unfortunately, there are very few blinded research studies comparing MRI and ultrasound, which likely has slowed the overall acceptance of ultrasound as a diag-nostic tool.7 Additionally, although fied significantly earlier than on plain radiographs9-13 (Figure 1). Moedandcolleagues9,10 usedultra-sound to evaluate healing in a series of 51 tibial shaft fractures (open and closed) after treatment with a locked, unreamed, intramedullary nail. Ul-trasound was performed in the first study9 at 2-week intervals for 10 weeks postoperatively and in the sec-ond study10 at 6 and 9 weeks postop-eratively to assess for the presence of fracture callus and for progressive de-crease in the metallic signal of the nail initially seen in the fracture gap (Figure 2). Tissue in the fracture gap pecially soft-tissue and ligamentous musculoskeletal radiologists are was increasingly hyperechoic com- structures). CT scans provide the most detailed evaluation of bone. Both MRI and CT are operator-independent and produce easily rec-ognizable images that may be conve-niently stored and transferred electronically for interpretation or consultation at any workstation. However, ultrasound possesses potential advantages over MRI.7 Ul- readily available in academic medi-cal centers, only recently have these specialists become available in com-munity settings. Evaluation Bony Union and Nonunion Radiographic imaging traditional- ly has been used to evaluate bone pared with the surrounding tibialis anterior muscle, indicating healing callus. This ultrasound finding was comparedwiththeradiographicstud-ies done at the same time. Ultra-sound was markedly more sensitive in detecting the presence of callus and, thus, in predicting earlier which fractures would ultimately progress to union. Ninety-seven percent of 526 Journal of the American Academy of Orthopaedic Surgeons David B. Weiss, MD, et al fractures that eventually healed withoutsecondaryprocedures(37/38) had a positive ultrasound at 6 or 9 weeks, versus only 22% (8/37) with positive radiographic findings at 6 or 9weeks.Fracturesthatdemonstrated no evidence of healing on ultrasound or radiographs by 9 weeks were man-aged with secondary procedures (eg, dynamization, bone grafting). The authors concluded that ultrasound was particularly useful in predicting which fractures would ultimately heal and which would require sec-ondary intervention, well before ra-diographic evidence of healing (or lack thereof). The clinically observed results were correlated with histo-logic specimens from canine frac-tures managed with an intramedul-lary nail. Increasing echogenic tissue detected in the fracture gap by ultra-sound was biopsied and revealed the presence of organizing callus.14 Similar findings were obtained by Eyres et al,15 who correlated ultra-sound, plain radiographs, and dual energy x-ray absorptiometry (DXA) to study healing of the fracture gap during limb lengthening. Increased echogenicity of the callus on ultra- Figure 2 Tibial fracture nonunion. A, Sagittal sonogram demonstrating cortical disruption at the fracture site (closed arrow) and visualization of the hyperechoic intramedullary nail (open arrow). Note the hyperechoic reverberation artifact deep to the nail, which is characteristic of metal (arrowhead). B, Sagittal radiograph of the same patient demonstrating tibial nonunion with an intramedullary nail. sound correlated with increased cor-tical density on DXA scanning. Several authors have used ultra-sound to evaluate for the presence and general quality of maturing cal-lus during bone transport proce- Infection Ultrasound is very useful in eval-uating soft tissues and joints for ev-idence of infection. Some of the earliest signs of infection include tis-sue edema, nonspecific erythema, 3, C). Joint or fluid collection aspira-tion may be performed with a safe starting point away from inflamed or infected tissues, thus avoiding pass-ing a needle through an infected re-gion and into a previously unaffect- dures.11,12 Ultrasound provided con- warmth, and tenderness. Fluid col- ed intra-articular region. This siderable value in confirming that the rate of limb lengthening was ap-propriate or, in several patients, needed to be slowed down. Ultra- lection may develop and is typically well visualized and localized by ul-trasound for aspiration. Joint effu-sion also may be well visualized by technique is particularly useful in patients with cellulitis, soft-tissue edema, or a body habitus that limits physical examination.16 sound also was used to identify cysts ultrasound.16 Using ultrasound for Diagnosing postoperative soft- that formed at the bone ends in sev-eral individuals during transport, en-ablingearlyintervention(eg,draining evaluation and guidance of aspira-tion offers several advantages over the traditional approaches. The joint tissue infection or osteomyelitis can be extremely challenging. The pres-ence of metallic hardware, the often the cysts, temporarily stopping may be examined to determine subtle signs and symptoms of in- lengthening)withsuccessfulresump-tion of regenerate bone growth. Ul-trasound showed the presence of re-generate callus notably earlier than did radiographs, resulting in a de-crease in the patients’ overall expo-sure to ionizing radiation.11,12,15 Volume 13, Number 8, December 2005 whether fluid is present and wheth-er there are specific fluid collections, such as bursitis (Figure 3, A) or soft-tissue abscesses (Figure 3, B); outside the joint, ultrasound can differenti-ate a bursa or soft-tissue abscess from intra-articular effusions (Figure flammation,andthepotentialforde-layed union or nonunion may con-found the clinical diagnosis. Acute infection in the immediate postoper-ative period typically presents with persistent wound drainage or dehis-cence, but subacute or chronic infec- 527 The Use of Ultrasound in Evaluating Orthopaedic Trauma Patients Figure 3 A, Infected olecranon bursitis. Sagittal sonogram over the olecranon process demonstrating mixed but predominantly hypoechoic bursal fluid collection (arrows). The olecranon process ( ) is deep to the bursitis. B, Elbow abscess. Sagittal sonogram demonstrating mixed hypoechoic-isoechoic soft-tissue fluid collection (arrows). Real-time imaging demonstrated swirling motion of the contents, indicating complex fluid collection, which, at the time of ultrasound-guided aspiration, proved to be infectious material. C, Elbow joint effusion. Sagittal sonogram of the posterior elbow in flexion demonstrating hypoechoic distention of the olecranon recess (arrows). tion may have a more subtle presen- mediate postoperative period).17,18 Se- ing the distal tibia and fibula. The tation. Clinical symptoms may rial examinations and correlation continuity of these ligaments may include persistent pain, swelling, warmth, erythema, swollen lymph with clinical findings may help elu-cidate true infection. Although ultra- be accurately assessed with ultra-sound.19,20 The strongest of the four nodes, fever, chills, and night sound cannot typically differentiate ligaments is the interosseous liga-sweats. These are, however, some- between a noninflammatory fluid ment, which extends proximally to what nonspecific. Likewise, labora- collection and purulent fluid, form the interosseous membrane. tory values, such as white blood cell count, erythrocyte sedimentation rate, and C-reactive protein level, may be falsely elevated because of other medical conditions. Radio-graphs are often nonspecific, and CT and MR images are typically degrad-ed by the metallic hardware.7 Ultrasound may determine the presence of a fluid collection around a plate and differentiate it from a bur-sa16 (Figure 4). Hyperemia and soft-tissue fluid collection immediately adjacent to hardware are consistent with infection (although these find-ings also may be present in the im- ultrasound-guided needle aspiration may be performed. When the fluid collection is large enough, aspiration of the fluid may assist in making the diagnosis. Ultrasound also may be useful in the presence of a draining sinus (particularly near hardware) to trackthesourceofthefluidanddem-onstrate whether it communicates with the underlying hardware. Interosseous Ligament Complex of the Ankle In the ankle, the interosseous lig-ament complex (ie, syndesmosis) consists of four ligaments connect- Ultrasound is useful for evaluating the integrity of the interosseous lig-ament in “high” ankle sprains as well as suspected or known syndes-motic injuries associated with ankle fracture. Although controversy ex-ists regarding how best to evaluate syndesmotic injuries and properly stabilize them, ultrasound may pro-vide objective evidence of ligament injury and demonstrate the extent of the injury19,20 (Figure 5). Christodoulou et al19 used ultra-sound to prospectively evaluate 90 Weber type B and C closed ankle fractures both preoperatively and 528 Journal of the American Academy of Orthopaedic Surgeons David B. Weiss, MD, et al Figure 4 Infected humerus plate. Sagittal sonogram along the humeral shaft demonstrating hypoechoic fluid (closed arrows) immediately adjacent to a metal plate (open arrows) and screw heads (arrowheads). Reverberation metal artifact is noted deep to the plate and does not obscure the overlying infected fluid collection. Figure 5 Interosseous membrane disruption in the ankle. A, Transverse sonogram over the symptomatic extremity demonstrating disruption (arrow) of the normally hyperechoic and continuous interosseous membrane (arrowheads). B, Normal appearance on the contralateral asymptomatic extremity (arrowheads). F = fibula, T = tibia. IOM demonstrated the same charac- er two ankles had capsular tears but teristics as an intact one. no ATFL tear. Eleven of the 14 posi-tive examinations were seen on stat- Ligamentous Injury ic examination; the other 3 ankles In the ankle, disruption of the an- required a dynamic examination (an-teriortalofibularligament(ATFL)and terior drawer test) to visualize the postoperatively to assess injury to the syndesmosis and evaluate heal-ing. They demonstrated 89% sensi-tivity and 95% specificity for in-terosseous membrane (IOM) tear after correlating preoperative ultra- calcaneofibular ligament has been well documented on ultrasound.21-23 Ultrasound may provide a useful ad-junct in evaluating chronic symp-toms or may provide a more reliable method of grading the severity of soft-tissue injury. We have success- tear. There were no false-positive re-sults. Ultrasound also has been shown to identify ligamentous pathology in the posterolateral corner of the knee. Sekiya et al24 used fresh cadaveric knees to demonstrate the structures sound with intraoperative findings. fully used ultrasound to evaluate of the posterolateral knee with All unstable IOM injuries (evaluated chronicsoft-tissueankleinjuriesthat sonography. The ability to assess lig-intraoperatively) were stabilized remain symptomatic after nonsurgi- amentous injury via ultrasound has with a screw across the syndesmo- cal treatment (Figure 6). The ability proved to be a useful adjunct to MRI sis. Postoperative ultrasound was to perform a dynamic examination in evaluating multiligamentous performed on all ankles with syndes-motic repair at 2 months postopera-tively (when the syndesmosis screw was invaluable for demonstrating pathologic findings. In their prospective study of 17 knee injuries. The complete nature of these injuries may be difficult to fully appreciate on MRI because of was removed), at 4 months, and lateral ankle soft-tissue injuries the presence of significant hemato-monthly thereafter until healing oc- undergoing surgical exploration, ma and edema as well as the static curred. Healing was confirmed intra-operatively during hardware remov-al. A difference was noted between the gap in the echogenic layer repre-senting the torn IOM seen on preop-erative ultrasound and the mixed echogenic and anechoic areas seen during healing. Once healed, the Volume 13, Number 8, December 2005 Campbell et al21 reported that ultra-soundwasusedtocorrectlydiagnose 14 of 17 ATFL injuries. The ATFL in-juries were confirmed intraopera-tively. The remaining three scans were equivocal. One scan missed an ATFL injury, which also had a calca-neofibular ligament injury. The oth- natureoftheexamination.However, the cruciate ligaments—the posteri-or cruciate ligament in particular— are not well visualized on ultra-sound and are better seen on MRI.7 Ultrasound also may be effective in evaluating the knee after a tibial pla-teaufracturewhenthereissuspicion 529 ... - tailieumienphi.vn