Musculoskeletal Imaging

Musculoskeletal Imaging (21)

The advent of the multidetector CT (MDCT) scanner has increased the applicability of this imaging technique for the assessment of the musculoskeletal system. This technology allows for the acquisition of large data set in the axial plane that can be reconstructed in multiple planes of imaging with the use of multiplanar reconstruction (MPR) algorithm. 

 

Diffuse idiopathic skeletal hyperostosis (DISH) is not really an arthropathy because it spares synovium, articular cartilage, and articular osseous surfaces. It is a fairly common ossification process involving ligamentous and tendinous attachments to bones and occurs in 12% of the elderly (55). It most commonly affects the thoracic spine but also may involve the pelvis, foot, knee, and elbow. It can involve ossification of all the ligaments surrounding the vertebral bodies, particularly the anterior longitudinal ligament. Ossification of the posterior longitudinal ligament (OPLL) can also be seen. This is reported to be more common in orientals and can be responsible for significant spinal canal stenosis. By definition, DISH must involve a flowing ossification of at least four contiguous vertebral bodies (Fig. 6-43A,B). There must be normal disc spaces and facet joints, without joint sclerosis.

FIGURE 6-43. Diffuse idiopathic skeletal hyperostosis. Frontal (A) and lateral (B) radiographs of the lower thoracic spine. There are flowing ossifications (arrowheads) of the paraspinal ligaments bridging more than four segments of the spine. Note relative preservation of the intervertebral disc spaces.

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Source: Physical Medicine and Rehabilitation - Principles and Practice

It is also known as pseudogout and has the classic triad of pain, cartilage calcification, and joint destruction. Chondrocalcinosis at the knee, wrist, or symphysis pubis is virtually diagnostic of calcium pyrophosphate dehydrate deposition disease (CPPD) (Fig. 6-42).

FIGURE 6-42. Chondrocalcinosis. Frontal radiograph of the right knee. Calcifications (arrows) are present within the medial and lateral tibiofemoral joint along the expected location of the meniscus.

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Source: Physical Medicine and Rehabilitation - Principles and Practice

Gout is a metabolic disorder that most commonly involves the feet, especially the first metatarsophalangeal joint, as well as the ankles, knees, hands, and elbows in asymmetric fashion. It is produced by a deposition of monosodium urate crystals in tissues with a poor blood supply, such as cartilage, tendon sheaths, and bursae. The radiographic features of gout typically do not appear until after 4 to 6 years of episodic arthritis. Radiographic features characteristic of gout include the following:

  • Tophi or periarticular soft-tissue nodules/masses created by the deposition of urate crystals that may contain calcium.
  • Tophi-induced periarticular or intra-articular bone erosion. Prominent cortical edges overhanging the tophi and well-defined bone erosions (with sclerotic margins) (Fig. 6-41) (54).
  • Random distribution, without marked osteoporosis.

FIGURE 6-41. Gout arthritis affecting the 1st MTP joint. There are large periarticular bone erosions with overhanging edges (arrow) and significant soft tissue swelling.

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Source: Physical Medicine and Rehabilitation - Principles and Practice

Rheumatoid arthritis is a connective tissue disorder of unknown etiology that can affect any synovial joint in the body. It is a bilaterally symmetric inflammatory degenerative disease that involves the following joints in order of decreasing frequency: :

  • Small joints of the hands and feet, with the exception of the distal interphalangeal joints
  • Knees
  • Hips
  • Cervical spine
  • Shoulders Elbows

The major radiographic findings include the following: :

  • Symmetric periarticular soft-tissue swelling
  • Juxta-articular osteoporosis proceeding to diffuse osteoporosis
  • Erosions of the intracapsular portions of the articulating bones not covered by cartilage, which can proceed to severe subchondral bone erosion
  • Uniform joint space narrowing
  • Synovial cysts (e.g., Baker’s cysts behind the knee)
  • Subluxations (e.g., boutonniere or swan-neck deformities of the fingers, and palmar and ulnar subluxation of the proximal phalanges on the metacarpal heads) (Fig. 6-40A,B) (54)

FIGURE 6-40. Frontal projections of both hands. There is extensive erosive disease within the wrist joints bilaterally, ulnar subluxations to the 2nd, 3rd MCP and to the 4th PIP and radial subluxation to the 5th PIP on the left.

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Source: Physical Medicine and Rehabilitation - Principles and Practice

Osteoarthritis or degenerative joint disease (DJD) is an asymmetric, usually bilateral mechanical degenerative process that involves joints significantly involved in weight bearing, such as the hip, knee, and spine, and those involved in frequent repetitive mechanical trauma, such as the distal interphalangeal joints of the fingers, trapezium–first metacarpal joint, trapezium- scaphoid joint, and metatarsophalangeal joint of the great toe. It is the most common arthritis, and it is estimated that 80% of the population with more than 50 years will show radiographic evidence of osteoarthritis. The most common radiographic findings include the following:

  • Nonuniform loss of joint space caused by cartilage degeneration in high load areas (e.g., the superior aspect of the hip and medial knee).
  • Sclerosis of the subchondral bone.
  • Osteophyte formation at the margins of the articular surfaces.
  • Cystlike rarefactions in the subchondral bone that may collapse to produce marked joint deformities.
  • Adjacent soft-tissue swelling (e.g., that which occurs with Heberden’s nodes of the distal interphalangeal joints of the fingers) (Fig. 6-39) (53).

FIGURE 6-39. Frontal projection of both hands demonstrates joint space narrowing, marginal osteophytosis, subchondral bone sclerosis involving the distal interphalangeal joints and the triscaphae joints (short arrow ) of the hands and wrist. In this patient, there are erosions on the right second DIP and left third DIP joints (long arrow ) that suggest erosive OA.

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Source: Physical Medicine and Rehabilitation - Principles and Practice

Technetium-99 scintigraphy has been valuable for detecting stress fractures of metatarsal and tarsal bones, and CT has high accuracy for detecting osteochondral fracture. In foot pain of undetermined etiology, however, MRI is an excellent screening modality because it permits direct evaluation of all osseous and soft-tissue structures.

MRI is superior to any other modality in displaying tendon pathology (47,48). In tenosynovitis, MRI detects fluid within the tendon sheath as having moderate signal intensity on T1-weighted images and as hyperintense on T2-weighted images. Tendinosis is commonly observed in the Achilles, tibialis posterior, flexor hallucis longus, tibialis anterior, and peroneal tendons (Fig. 6-37). Tendinosis is visualized as a focal or diffuse thickening of the tendon that may show areas of increased signal intensity on T2-weighted images. Plantar fasciitis shows similar changes within the plantar aponeurosis (Fig. 6-38). With a complete tendon rupture, axial MR images show absence of the tendon and its replacement by edema. Sagittal and coronal MR images display the site of discontinuity, with edema occupying the gap and surrounding the torn ends of the tendon.

FIGURE 6-37. A: Axial T1-weighted image at the level of the talar dome. There is thickening and splitting to the fibers of the peroneus brevis (short arrows). Note normal signal and configuration to the peroneus longus (PL). B: Axial PD fat suppressed sequence. The split fibers of the peroneus brevis are better depicted (arrowheads). There is an effusion within the tendon sheath (short arrow).

FIGURE 6-38. A: Sagittal T1-weighted image of the hindfoot. There is thickening and increased signal (short arrow) within the proximal fibers of the plantar fascia (PF). TT tarsal tunnel; ST, sustentaculum talus. B: Coronal T2-weighted fat suppressed sequence. There is asymmetric thickening and increased signal to the medial bundle of the plantar fascia (MB). Edema extends into the adjacent fat (arrowhead ). Note normal thickness and signal to the lateral bundle (LB).

Stress fractures of the tarsal or metatarsal bones appear on MRI as linear areas of decreased marrow signal intensity. There are adjacent areas of marrow edema that are hypointense relative to marrow fat on T1-weighted images and hyperintense on T2-weighted images (47). By MRI, osteochondral fractures (e.g., of the talar dome) have an appearance similar to that of osteochondritis dissecans of the knee. The primary task of MRI is to determine the stability of the fragment by demonstrating the integrity of the articular cartilage and the absence of fluid between the osteochondral fragment and the parent bone. Synovial cysts of intertarsal joint origin demonstrate moderate signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

Previously, arthrography and tenography were the primary means of imaging ankle ligament injuries. They had the limitations of being invasive, providing only an indirect depiction of ankle ligament disruption, and yielding potentially false- negative results. MRI provides a noninvasive means of directly imaging all the ligaments in the vicinity of the ankle as well as all the other osseous and soft tissues.

Axial MR images provide good visualization of the tibiofibular ligaments of the tibiofibular mortise. All the lateral collateral ligaments of the ankle have an oblique orientation, and to image these ligaments in full length, either an oblique imaging plane that parallels their length must be chosen or the foot must be placed in sufficient dorsiflexion or plantar flexion to bring the ligaments into one of the standard imaging planes. With the imaging plane parallel to the anterior talofibular ligament, it is displayed as a low–signal-intensity band extending anteromedially from the lateral malleolus to gain attachment to the talus just anterior to its fibular articular surface (Fig. 6-33A) (50). The calcaneofibular ligament is visualized as a low–signal-intensity structure extending from the lateral malleolus to the calcaneus, with the peroneus longus and brevis tendons situated superficial to its fibular end (Fig. 6-33B). The posterior talofibular ligament is visualized as a wide low–signal- intensity structure extending from the deep surface of the lateral malleolus to a broad attachment on the talus from its fibular articular surface to its posterior process (Fig. 6-33C).

FIGURE 6-33. T1-weighted images of the normal lateral collateral ligaments of the ankle. A: The anterior talofibular ligament (ATAF) extends from the fibular malleolus to the neck of the talus. B: The calcaneofibular ligament (CFL) attaches to the calcaneus and is deep to the peroneus tendons. C: The strong talofibular ligament (between arrowheads).

MRI of ankle ligament injuries offers promise for the noninvasive evaluation of the site and severity of both acute ankle ligament injuries and chronic ankle instability (51).

The mechanism of injury of the lateral collateral ligaments typically involves plantar flexion and inversion, and they are usually injured in a predictable sequence from anterior to posterior. The anterior talofibular ligament is the most commonly injured, followed in sequence by injury to the calcaneofibular and posterior talofibular ligaments. The major MRI finding in a complete rupture (i.e., grade III sprain) of the anterior talofibular ligament is a complete discontinuity of the ligament visualized at all imaging levels (Fig. 6-34A,B). This is accompanied by periarticular edema or hemorrhage and joint effusion because this ligament is a thickening of the ankle joint capsule. The edema and effusion are visualized with moderate signal intensity on T1-weighted MR images and hyperintensity on T2-weighted images. A partial tear (i.e., grade II sprain) of the anterior talofibular ligament is visualized on MRI as a discontinuity of the upper part of the ligament, with the lower portion remaining intact. Again, there is periarticular edema, hemorrhage, and joint effusion. Grade II sprains of the calcaneofibular ligament may appear as a longitudinal splitting In contrast to the three discrete lateral collateral ligaments, or waviness of the ligament with fluid accumulation within the the medial collateral or deltoid ligament is a continuous tendon sheath of the overlying peroneal tendons (Fig. 6-35). ligamentous sheet with an apical attachment to the tibial malleolus, and a broad base attaching below to the navicular, talar neck, spring ligament, sustentaculum tali of the calcaneus, and posterior talus. The posterior tibiotalar part of the deltoid ligament is its thickest and strongest (52). The deltoid ligament can be visualized by either axial or coronal MRI. Axial images allow simultaneous visualization of all parts of the deltoid ligament, the overlying flexor retinaculum, and the walls and contents of the tarsal tunnel (Fig. 6-36A). The contents of the four compartments under the flexor retinaculum include, from anterior to posterior, the tibialis posterior tendon, flexor digitorum longus tendon, posterior tibial artery, tibial nerve, and flexor hallucis longus tendon. Coronal MR images through the deltoid ligament display the proximal and distal attachments of each part of the deltoid ligament (Fig. 6-36B).

MRI has the potential to visualize even grade I sprains, which are microtears confined to the interior of the ligament. The minute foci of edema and hemorrhage accompanying such tears become hyperintense on T2-weighted images. Findings compatible with such grade I tears have been identified in the posterior tibiotalar portion of the deltoid ligament. They are frequently accompanied by fluid within the tendon sheath of the overlying tibialis posterior.

In chronic ankle instability, MR images show thinned, lengthened, wavy ligaments in some locations and thickened, scarred ligaments in others.

FIGURE 6-34. Complete rupture of the anterior talofibular ligament. Axial T1-weighted (A) and T2-weighted fat suppressed sequences (B). There is discontinuity to the ligament fibers (arrows) and associated soft tissue swelling (arrowhead in B).

FIGURE 6-35. Partial tear to the calcaneofibular ligament. There is thickening and increased signal within the ligament fibers (long arrow) and edema within the soft tissues between the ligament and the calcaneus.

FIGURE 6-36. Normal tibial collateral ligament (i.e., deltoid ligament) and contents of the tarsal tunnel. A: Axial T1-weighted image demonstrates the deltoid ligament (DL), flexor retinacula (FR), tibialis posterior (TP), flexor digitorium longus (FDL), posterior tibialis artery and vein (PTA/V), posterior tibialis nerve (PTN) and the flexor hallucis longus (FHL). B: Coronal T2-weighted fat suppressed image demonstrating the superficial and deep fibers of the deltoid ligament.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

Patellar tendinitis (jumper’s knee) is demonstrated by MRI as an area of edema within the patellar ligament (i.e., tendon) at its patellar (Fig. 6-28) or tibial tuberosity attachment. There is also associated edema in the adjacent subcutaneous fat or the infrapatellar fat pad.

FIGURE 6-28. Sagittal T2-weighted fat suppressed image of patellar tendinitis. The arrow points to the increased signal intensity within the proximal tendon fibers and the adjacent infrapatellar fat pad. .

Ischemic necrosis about the knee most commonly involves the weight-bearing surface of the medial femoral condyle, and its MRI findings are as described for the hip.

Osteochondritis dissecans occurs mainly in adolescents and involves a partial or total separation of a segment of articular cartilage and subchondral bone from the underlying bone (39). It commonly involves the intercondylar portion of the medial femoral condyle articular surface. It is visualized on T1-weighted MR images as a low–signal-intensity region in the subchondral bone with or without disruption of the overlying articular cartilage (Fig. 6-29A,B). If the involved osteochondral segment becomes completely separated from the underlying bone, it becomes an intra-articular loose body. The role of MRI in osteochondritis dissecans is mainly to determine the stability of the fragment, because the treatment hinges on that.

FIGURE 6-29. Osteochondral lesion (previously osteochondritis dissecans). T2-weighted fat suppressed (A) and PD (B) sequences. A: There is a hyperintense T2 signal at the interface of the OC lesion and the adjacent cortex compatible with an unstable fragment. B: The lesion is well demarcated by a hypointense rim (short arrows).

Chondromalacia patella can be diagnosed and graded noninvasively by MRI (40). In stage I, the posterior patellar articular cartilage demonstrates local areas of cartilage swelling with decreased signal intensity on both T1- and T2-weighted images. Stage II is characterized by irregularity of the patellar articular cartilage with areas of thinning. Stage III demonstrates complete absence of the articular cartilage with synovial fluid extending through this cartilaginous ulcer to the subchondral bone (Fig. 6-30).

FIGURE 6-30. Grade IV chondromalacia. Sagittal PD sequence with grade IV chondromalacia. There is a full thickness defect (arrow) with subchondral bone sclerosis and early subchondral cyst formation within the proximal patella.

Popliteal (i.e., Baker’s) cysts and other synovial cysts about the knee appear hyperintense on T2-weighted images (Fig. 6-31A–D). They can be visualized on axial, sagittal, or coronal images. Popliteal cysts are usually an enlargement of the semimembranosus-gastrocnemius bursa, which is located between the tendon of insertion of the semimembranosus and the tendon of origin of the medial head of the gastrocnemius. Popliteal cysts may communicate with the knee joint and therefore may be caused by chronic knee joint pathology that produces effusion. A previously undescribed bursa is now known to be consistently present be tween the tibial collateral ligament and a major slip of the semimembranosus tendon that extends beneath it, and may serve to clarify many cases of previously unexplained medial knee pain (46). Inflammation of this bursa is well demonstrated by MRI (Fig. 6-32A,B).

FIGURE 6-31. Baker’s cyst. A: A T1-weighted axial MRI demonstrates a hypointense Baker’s cyst (arrowheads) in the interval between the semimembranosus (SM) and the medial head of the gastrocnemius (MG). T1-weighted (B) and T2-weighted (C) sagittal MR images through Baker’s cyst (arrowheads). Note that the hypointense fluid in the cyst in the T1-weighted image becomes hyperintense on the T2-weighted image. D: A coronal T1-weighted image locates the cyst between the SM and the MG.

FIGURE 6-32. Axial (A) and coronal (B) T2-weighted PD fat suppressed sequences. A: There is minimal fluid anterior to the semimembranosus (long arrow). B: The fluid is deep to the semitendinosus (St) and superficial to the meniscocapsular junction of the medial meniscus (long arrow in B). FIGURE 6-33. T1-weighted images of the normal lateral collateral ligaments of the ankle. A: The anterior talofibular ligament (ATAF) extends from the fibular malleolus to the neck of the talus. B: The calcaneofibular ligament (CFL) attaches to the calcaneus and is deep to the peroneus tendons. C: The strong talofibular ligament (between arrowheads).

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

The collateral ligaments are best visualized by coronal MR images (Fig. 6-27). The medial collateral ligament appears as a narrow low–signal-intensity band extending from the medial epicondyle of the femur to an attachment on the anteromedial aspect of the tibia 5 to 6 cm below the joint line. It is overlaid at its tibial attachment by the tendons of the pes anserinus, which are separated from it by an intervening anserine bursa that is not visualized unless it is inflamed. Deep to the tibial collateral ligament, the medial capsular ligament, sometimes called the deep portion of the tibial collateral ligament, has femoral and tibial attachments close to the joint interval and deep attachments to the medial meniscus, referred to as the meniscofemoral and meniscotibial or coronary ligaments. Valgus and rotary stresses can injure the medial capsular ligament or the tibial collateral ligament, usually in that order (39). In a complete rupture (i.e., grade III injury), MRI can show discontinuity, serpentine ligamentous borders, and edema within adjacent connective tissues. In a partial tear (i.e., grade II injury) or in the case of microtears confined to the ligament substance (i.e., grade I injury), the ligament may show no discontinuity, but the overlying subcutaneous fat typically demonstrates edema and hemorrhage, which is indicated by moderate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Injury to the tibial collateral ligament is commonly associated with injuries to the anterior cruciate ligament and medial meniscus.

FIGURE 6-27. Tibial collateral ligament tear (MCL). A: Coronal T2-weighted fat suppressed sequences of grade I injury. There is edema (short arrows) overlying the intact fibers of the MCL (long arrow). B: Normal MCL (arrow).

The lateral collateral complex commonly refers to the lateral supporting structures of the knee, whose main components are the iliotibial tract, the lateral collateral ligament, the long head of the biceps femoris, and the popliteofibular ligament. These structures are best seen on axial and coronal MR images as a low–signal-intensity band extending somewhat obliquely from the lateral femoral epicondyle to the fibular head. The lateral collateral ligament is usually injured by varus and rotary stresses to the knee, although its frequency of injury is less than that of the tibial collateral ligament. The MRI findings of the injured fibular collateral ligament are similar to those for the tibial collateral ligament.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice

The cruciate ligaments are best visualized by sagittal or oblique sagittal MR images that display the full length of the ligaments (Fig. 6-24A). On straight sagittal images, the slender nature of the anterior cruciate ligament and its oblique course cause a volume-averaging effect that averages fat signal intensity about the ligaments with the normal low signal intensity of the ligament so that the anterior cruciate ligament frequently does not appear as a complete signal void. Furthermore, straight sagittal images typically fail to demonstrate the anterior cruciate ligament’s femoral attachment because of its oblique orientation in both sagittal and coronal planes. Oblique sagittal images that parallel the ligament show the full thickness and length of the anterior cruciate ligament without subjecting it to partial volume averaging (44). In the extended position of the knee, which is typically used for MR images, the anterior cruciate ligament is normally taut. The posterior cruciate ligament is a thicker ligament and is therefore well visualized on straight sagittal MR images (Fig. 6-24B). It can be visualized as a signal void structure from its attachment to the posterior tibial intercondylar area to its attachment on the medial femoral condyle. With the knee extended, the posterior cruciate ligament is visualized as thick and posteriorly bowed. It straightens with knee flexion. Axial images can be very helpful to evaluate the femoral insertion of the anterior and the posterior cruciate ligaments.

FIGURE 6-24. Normal cruciate ligaments. A: An oblique sagittal MRI parallel to the anterior cruciate ligament demonstrates excellent visualization of all borders and attachments of the anterior cruciate ligament (arrow ). B: A T2-weighted MRI of the posterior cruciate ligament (arrow ), which is normally posteriorly bowed when the knee is extended.

The MRI appearance of an anterior cruciate ligament injury depends on the site and degree of disruption, as well as on the age of the tear. A complete tear may be visualized as a discontinuity of the ligament (Fig. 6-25A–D). In the acute complete tear, the interval between the torn ends of the ligament is often occupied by a mass of intermediate signal intensity on T1-weighted images that appears hyperintense on T2-weighted images (45). At other times, the torn ligament may present as a fusiform or irregular soft-tissue mass of intermediate signal intensity on T1-weighted images that appears hyperintense on T2-weighted images. These fluid masses are usually a combination of edema and hemorrhage, and there may be an associated joint effusion. If the ligament tears from its femoral attachment, the axial images will show fluid signal between the lateral femoral condyle and the expected ligament insertion. In partial tears there is no complete discontinuity, but the ligament that appears intact on a T1-weighted image may show a hyperintense signal on T2-weighted images, or the ligament may display an interrupted or concave anterior or posterior margin when the knee is extended (42). In chronic anterior cruciate ligament deficiency, there may be a complete absence of the ligament, or there may be only remnants remaining in its usual location. Some secondary signs of anterior cruciate ligament injury may be present. These include a forward shift of the tibia and an anterior bowing or buckling of the posterior cruciate ligament caused by the position of the knee within the coil, which duplicates the knee position of an anterior drawer or Lachman test (39).

FIGURE 6-25. Acute ACL injury; spectrum of findings. A: Sagittal PD and B: Sagittal PD fat suppressed sequences. The arrow demonstrates the torn ACL resting against the tibial spine. There is diffuse marrow edema with increased signal intensity on the T2-weighted sequence. C: Axial T2-weighted fat suppressed sequence. The long arrow is pointing to the ACL fibers. There is edema anterior to the ACL (short arrow) within the intercondylar fossa. The arrowheads demarcate an area of marrow edema within the lateral femoral condyle. D: There is bone marrow edema within the posterior tibial plateau (long arrow) and the anterior femoral condyle (short arrow), tipical contusion pattern in ACL injuries. There is a small radial tear to the free inner margin of the lateral meniscus (arrowhead) secondary to the compression injury.

On T1-weighted MR images, partial tears of the posterior cruciate ligament typically appear as foci of increased signal intensity within the normal black signal void of the ligament. These appear hyperintense on T2-weighted images. With complete tears, a frank discontinuity is visualized with an intervening fluid mass that becomes hyperintense on T2-weighted images (Fig. 6-26). The gap between the ends of a completely torn posterior cruciate ligament can be exaggerated by imaging the knee in flexion, which tenses the posterior cruciate ligament.

FIGURE 6-26. Sagittal T1-weighted image of a chronic PCL tear. The arrow points to the thickened posterior cruciate ligament. Intermediate signal intensity is replacing the normal hypointensity of the ligament.

Refferences

Source: Physical Medicine and Rehabilitation - Principles and Practice
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