
Imaging Techniques Relative to Rehabilitation (39)
A brief presentation of imaging techniques of interest to the physiatrist must necessarily be selective. Because the diagnosis and initial treatment of fractures are primarily the responsibility of the orthopedic surgeon, with the rehabilitation professional typically involved only later in the course, a full discussion of fractures is not presented in this chapter. Only those fractures that bring patients under the long-term care of the physiatrist are included (e.g., vertebral fractures with the potential to damage the spinal cord). Similarly, tumors and infectious processes are de-emphasized. Rather, emphasis is placed on imaging degenerative musculoskeletal processes, spine and head trauma, stroke, and degenerative central nervous system (CNS) diseases commonly seen by the physiatrist. We will also cover imaging in sport medicine as this is a rapidly changing area in radiology and review the current applications of diagnostic ultrasound in the evaluation of musculoskeletal disorders.
In the past two decades, computed tomography (CT) and magnetic resonance imaging (MRI) have become the most sophisticated imaging modalities for evaluating the musculoskeletal system and the CNS. Therefore, this chapter focuses mainly on the recent applications of CT and MRI in the imaging of musculoskeletal and neural pathology of interest to the physiatrist. In the final section, we will introduce some relatively new imaging technologies of interest to the physiatrist, including advanced MRI methods and ultrasound imaging (USI).
The role of plain film examinations in the assessment of abnormalities of specific joint disorders is well established in the medical literature. A brief review of the most commonly performed radiographic examinations of the extremities will be done when addressing the specific subject.
Children categories

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.

Spine and Spinal Cord Imaging (8)
It is clear, after multiple research studies to assess the usefulness of imaging in low back pain, that uncomplicated acute low back pain is a benign, self-limited condition that does not warrant any imaging studies. The vast majority of patients are back to their usual activities within 30 days. Radiographic evaluation of the lumbar spine includes frontal and lateral radiographs. These are indicated in the evaluation of back pain and weight loss, after mild trauma in patients older than 50 y/o, in patients with unexplained fever, immunosuppression, history of cancer, prolonged use of steroids and focal neurologic, or disabling symptoms. Oblique views are useful for the assessment of defects to the pars interarticularis when suspecting spondylolysis and for the evaluation of the nerve root foramina. The relative radiation dose level for a routine radiographic examination of the lumbar spine is between 1 and 10 mSv (56). Although plain radiographs remain valuable for detecting many types of spine fractures and degenerative changes, the high resolution of osseous and soft-tissue structures provided by CT and MRI has made these modalities invaluable for the diagnosis of degenerative, traumatic, neoplastic, and infectious diseases of the spinal column and spinal cord.

Brain Imaging (10)
The following section will be dedicated to brain imaging relevant to rehabilitation. Emphasis is placed on the imaging of ischemic and hemorrhagic strokes, head trauma, and common degenerative diseases. The imaging of brain neoplasms and infections will not be covered in this section, as it is beyond the scope of this text.
Gout Imaging
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezGout 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Rheumatoid Arthritis Imaging
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezRheumatoid 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Osteoarthritis Imaging
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezOsteoarthritis 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Other Ankle Abnormalities
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezTechnetium-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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Ankle Ligament Imaging
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezPreviously, 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Other Knee Abnormalities
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezPatellar 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).
Source: Physical Medicine and Rehabilitation - Principles and Practice
Collateral Ligament Injuries
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezThe 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Cruciate Ligament Injuries
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezThe 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.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Subarachnoid and Intraventricular Hemorrhage
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezSubarachnoid and intraventricular hemorrhage can be spontaneous, as in the case of a bleeding aneurysm or arteriovenous malformation, or secondary to trauma. CT is the imaging modality of choice for evaluating these types of hemorrhages because it detects the hemorrhage from its onset as a hyperdensity. However, subarachnoid hemorrhage is not as radiodense as epidural or subdural hemorrhage because the blood will be diluted by CSF. Unless blood replaces at least 70% of the CSF, the subarachnoid hemorrhage remains isodense to adjacent gray matter (82). When the volume of blood is sufficient to make the hemorrhage hyperdense, it accumulates in the extensions and expansions of the subarachnoid space. Subarachnoid hemorrhage appears as linear radiodensities within the sulci or fissures or as larger aggregations in the basal cisterns (Fig. 6-86). MRI will not visualize a very early hemorrhage when oxyhemoglobin, a nonparamagnetic substance, is the primary constituent, and thus CT is the study of choice in the very early stages. Subarachnoid and intraventricular hemorrhage can cause communicating hydrocephalus by virtue of red blood cells blocking the arachnoid granulations, the CSF resorption sites.
FIGURE 6-86. Subarachnoid hemorrhage secondary to a right middle cerebral artery aneurysm. CT shows this condition as hemorrhagic radiodensities within sulci and cisterns (arrow ).
Aneurysms and arteriovenous malformations can be detected directly by contrast-enhanced CT and MRI, or by their flow void characteristics on non–contrast-enhanced MR images (Fig. 6-87A,B).
FIGURE 6-87. A: CT of an anterior cerebral artery aneurysm (arrow ) that produced a subarachnoid hemorrhage with secondary hydrocephalus. B: Axial collapse image of a time of flight (TOF) MR angiogram in a different patient. The arrow points to a large aneurysm arising from the left anterior communicating artery.
brain imagingSource: Physical Medicine and Rehabilitation - Principles and Practice
Cervical Disc Herniation
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezDisc herniation is typically preceded by degenerative changes in the mucopolysaccharides of the nucleus pulposus, which produce fibrillation of the collagen (60). This eventually causes dehydration and loss of disc volume. As a result, the nucleus pulposus no longer serves as a normal load-dispersing mechanism, and excessive stress is borne by the annulus fibrosus. This produces annular fissuring and tears that can culminate in herniation of the nucleus pulposus. The loss of the load-diffusing function of the normal disc also causes facet joint degeneration and marginal osteophytosis of the vertebral body ends by virtue of the increased loads these joints must bear.
Cervical disc herniation occurs with less frequency than lumbar disc herniation. About 90% of cervical disc herniations occur, in order of decreasing frequency, at C5-6, C6-7, and C4-5 (61,62). On CT examination, a herniated cervical disc appears as a dense soft-tissue mass protruding from the disc space centrally or paracentrally into the spinal canal or posterolaterally into the neural foramen (Fig. 6-51).
FIGURE 6-51. CT evaluation of a herniated C5-6 nucleus pulposus. An axial CT myelogram shows a radiodense protrusion of the C5-6 disc (arrow ) that distorts the left anterior aspect of both the thecal sac and the spinal cord.
On T1-weighted MR images, the herniated cervical disc appears as a posterior extension of the moderate signal intensity of the disc into the low–signal-intensity region of the thecal sac (Fig. 6-52A,B). Because the spinal cord appears as a relatively high–signal-intensity structure outlined by the low–signal-intensity CSF, the relationship of the herniated disc to the spinal cord can be visualized directly by MRI. On T2-weighted MR images, the degenerated disc appears as a narrowed disc interval. The disc herniation appears as a moderate– to low– signal-intensity impingement on the now high–signal-intensity CSF. The posterior margin of the herniated disc may have a to determine its probability of causing a patient’s myelopathic very-low-signal-intensity margin interfacing with the CSF. This findings (Fig. 6-53A,B). It is sometimes difficult to differentiate may be a posterior longitudinal ligament elevated by the herni-lateral herniations of the disc into the neural foramen from osteoated disc, or it may be fragments of the posterior part of the phytic encroachments by MRI because they may both demon- annulus fibrosus (61). T2-weighted images also permit evalua-strate low signal intensity. In these circumstances, CT provides tion of the relationship of the herniated disc to the spinal cord good differentiation between bone and soft-tissue density.
FIGURE 6-52. A: T2*-weighted axial MRI of the cervical spine shows a left posterolateral herniated C6-7 nucleus pulposus (between arrow) indenting the thecal sac (arrowhead ) and extending into the ostium of the ipsilateral nerve root foramina. B: A T2-weighted left parasagittal MRI shows the disc fragment (arrow ) impinging upon the intermediate–signal-intensity thecal sac (arrowheads) and low–signal-intensity posterior longitudinal ligament.
FIGURE 6-53. A: Axial T2-weighted image at the C4-5 level demonstrates a bilobed protrusion contained in the midline by the posterior longitudinal ligament. Note complete obliteration of the normal CSF signal anterior to the cord, posterior displacement, and compression of the cord. B: The herniated disc elevates the posterior longitudinal ligament, compresses the cervical cord, which demonstrates increased signal intensity as a sign of myelopathy.
Source: Physical Medicine and Rehabilitation - Principles and Practice
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Meniscal Injuries of the Knee
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezAll parts of both menisci are well visualized by MRI. Sagittal MR images provide good views of the anterior and posterior horns and a fair view of the body of both menisci. In more central sections, both horns of the menisci appear as wedge- shaped signal voids contrasted on their superior and inferior surfaces by the moderate signal intensity of the hyaline cartilage on the articular surfaces of the femur and tibia. In more peripheral sections, where the images are tangential to the circumference of the menisci, they appear bow tie shaped (Fig. 6-22). Coronal MR images provide the best visualization of the bodies of both menisci.
FIGURE 6-22. Sagittal MR images through a normal peripheral menisci. The anterior and the posterior (arrow ) horns appear wedge (triangular) in shape.
There are three types of meniscal findings visualized by MRI (16,39,40). One is the presence of small globular or irregular high–signal-intensity foci confined to the interior of the meniscus. This is considered to be an early type of mucoid degeneration. A second type of meniscal MRI finding is the presence of a linear region of increased signal intensity within the meniscus that does not extend to either the femoral or tibial articular surface of the meniscus but may extend to the meniscocapsular junction. Histologically, this represents fragmentation and separation of the fibrocartilage and is considered by many to be an intrameniscal tear. The significance of the globular or linear signals that do not extend to either articular surface of the meniscus is not fully agreed on (41).
Frank meniscal tears are demonstrated by MRI as linear or irregular areas of signal intensity that extend to one or both articular surfaces of the meniscus (Fig. 6-23). The high signal intensity is produced by synovial fluid in the crevices within the meniscus. These meniscal tears can be horizontal, vertical, or complex. Bucket-handle tears are vertical tears where the inner meniscal fragment is displaced toward the intercondylar notch (Fig. 6-23C,D). At times, repeated trauma or chronic degeneration may cause a gross distortion of meniscal shape, and the meniscus may then appear to have a truncated apex or to be grossly small with a free fragment.
FIGURE 6-23. Meniscal tears. A: T1-weighted MRI of a horizontal tear (arrow ) at the posterior horn of the medial meniscus that extends to its tibial articular surface. B: Coronal PD-weighted image of a bucket-handle tear. There is a displaced fragment from the lateral meniscus into the intercondylar fossa (arrow ). C: Sagittal FSE-PD fat suppressed sequence of a double “PCL sign.” The displaced fragment from a bucket handle tear (arrow ) projects anterior to the PCL. D: Sagittal PD fat suppressed sequence through the lateral tibiofemoral joint demonstrates the double delta sign. The displaced anterior horn from a large flap injury is projecting anterior to the posterior horn.
Other meniscal abnormalities well visualized by MRI include discoid meniscus, meniscal cysts, and abnormalities involving the postoperative meniscus. In discoid meniscus, typically involving the lateral meniscus, there is a continuous bridge of meniscal tissue between the anterior and the posterior horns in the central part of the joint. Meniscal cysts are usually associated with underlying horizontal meniscal tears through which synovial fluid collects at the meniscocapsular junction (42). They show high signal intensity on T2-weighted images. MRI also can be used to evaluate the postmeniscectomy patient with continuing or recurrent symptomatology (39). It can detect an incompletely excised meniscal tear, retained meniscal fragments, or a tear developing within the residual part of the meniscus. MR arthrography with gadolinium can be helpful to distinguish between retears and old healed tears that might still show increased signal intensity on T2-weighted images (43). .
Source: Physical Medicine and Rehabilitation - Principles and Practice
Hemorrhagic Stroke Imaging
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezA stroke is considered truly hemorrhagic if blood is found within the first 24 hours after initial symptoms. When blood is noted after this time, it is usually hemorrhagic transformation of an ischemic stroke, which is due to reperfusion injury.
Hypertension is the most common cause of intraparenchymal hemorrhage, which can also be caused by ruptured aneurysm, arteriovenous malformation, and more rarely, by infarction, neoplasms, blood coagulation defects, and cerebral arteritis (81). Common hemorrhage sites include the putamen and the thalamus, which receive their major blood supply from the lenticulostriate and the thalamogeniculate arteries, respectively.
Because freshly extravasated blood is more radiodense than gray or white matter, an acute hemorrhagic stroke is well visualized by CT as a hyperdense region usually conforming to an arterial distribution (Fig. 6-84A,B). The radiodensity of the blood clot increases over 3 days because of clot retraction, serum extrusion, and hemoglobin concentration. The extruded serum may form a hypodense rim around the hyper- dense clot (Fig. 6-84C). As edema develops over 3 to 5 days, the hypodense rim may increase. Eventually, the hyperdensity of the clot gradually fades and usually disappears by 2 months, leaving only a narrow hypodense slit to mark the site where hemorrhage took place (Fig. 6-84D).
FIGURE 6-84. CT evaluation of early and evolving hemorrhagic strokes. A: Recent hemorrhagic stroke has occurred in the distribution of the right posterior cerebral artery, which appears hyperdense (arrows). B: A massive hypertensive hemorrhage involving most of the interior of the left cerebral hemisphere with intraventricular hemorrhage, midline shift to the right, and herniation of the left hemisphere under the falx cerebri. C: A 5-day-old hemorrhagic stroke involving the lenticular nucleus shows a hyperdense hemorrhagic center (arrow ) and a hypodense edematous rim (arrowhead). D: The same stroke patient displays replacement of the hyperdense hemorrhage with a narrow hypodense interval (arrows) several months later.
The appearance of hemorrhage by MRI depends on the state of the hemoglobin in the hemorrhage (81). The oxyhemoglobin present in a fresh hemorrhage is nonparamagnetic; therefore, very early hemorrhage is not detected by MRI. Within a few hours, the oxyhemoglobin will be converted to deoxyhemoglobin, which is a paramagnetic substance. Intracellular deoxyhemoglobin will cause acute hemorrhage to appear very hypointense on T2-weighted images and slightly hypointense or isointense on T1-weighted images (Fig. 6-85A). By 3 to 7 days, intracellular deoxyhemoglobin is oxidized to methemoglobin as the clot enters the subacute phase. Although a subacute hemorrhage has several subphases in which the signal intensity of methemoglobin varies, in general methemoglobin appears hyperintense on both T1- and T2-weighted images (Fig. 6-85B). Because the conversion to methemoglobin begins at the periphery of the clot, early in the subacute phase a hemorrhage can have a hyperintense margin and a central hypointense region still containing deoxyhemoglobin. Eventually the entire region of subacute hemorrhage becomes hyperintense. Over several months, the methemoglobin is gradually resorbed and the clot develops a rim of hemosiderin- containing macrophages. Hemosiderin is hypointense on both T1- and T2-weighted images. Therefore, a chronic hemorrhage of several months duration often has a hyperintense methemoglobin center and a hypointense hemosiderin rim. Because the hemosiderin deposits remain indefinitely, an old hemorrhage of several years duration shows up as a totally hypointense area. Gradient-echo sequences have recently been added to many brain MRI protocols, as they are very sensitive in the detection of degrading blood products, which appear as areas of hypointensity. As can be seen, CT provides the very earliest information about cerebral hemorrhage, whereas MRI is the better technique for determining hemorrhage age.
FIGURE 6-85. MRI evaluation of hemorrhagic stroke. A: An acute hemorrhagic stroke involving the occipital lobe appears hypointense (arrow ). B: In the subacute phase, the same area appears hyperintense (arrow ).
brain imagingSource: Physical Medicine and Rehabilitation - Principles and Practice
Degenerative Disc Disease
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezThe intervertebral disc space is a cartilaginous joint with a central nucleus pulposus surrounded by an annulus fibrosus. Degenerative change in the nucleus pulposus is termed inter-vertebral osteochondrosis (Fig. 6-49A,B). Early signs of disc disease may include loss of fluid signal within the nucleus pulposus (dehydration), which results in decreased signal within the central portion of the disc on T2-weighted images, and blurring of the transition between the nucleus pulposus and the annulus fibrosus. This is followed later by narrowing of the intervertebral disc, which sometimes results in vertebral body end-plate degenerative changes. These end-plate changes are referred to as Modic changes (58). Modic type I changes are characterized by signal of edema, that is decreased signal on T1-weighted images and increased signal on T2-weighted images. Type II changes (Fig. 6-50A,B) follow the signal characteristic of fat, with intermediate to increased signal on T1-weighted images and increased signal on T2-weighted images. This is the most common type of reactive end-plate changes appreciated on degenerative osteochondrosis. Type III changes represent osseous sclerosis, characterized by decreased signal on both the T1- and the T2-weighted images.
FIGURE 6-49. A: Sagittal T2WI of the lumbar spine demonstrating different stages of intervertebral osteochondrosis. Normal disk (ND) demonstrates increased signal to the nucleus pulposus and normal height. With early degeneration (ED), the nucleus pulposus loses signal in part related to the decreased water content of the intervertebral disc but preserves the intervertebral height. With advanced degeneration (AD), there is near complete loss to the normal signal of the intervertebral disk and early traction osteophyte formation (TO). Note herniated disk (DH) at the L5-S1 segment. B: Advanced degenerative osteochondrosis on a different patient. There is loss of the intervertebral disk height, Schmorl’s node formation (SN) representing end-plate herniation and moderate traction osteophyte formation (arrow).
FIGURE 6-50. Sagittal T1- (A) and T2- (B) weighted images with degenerative osteochondrosis of the cervical spine. There is decreased T2 signal to most intervertebral discs, decreased disc height throughout, annular bulge, and traction osteophytosis. Note increased signal to the inferior end plate of C5 both on the T1- and T2-weighted images (arrows) characteristic of Modic type II changes.
When the disc becomes degenerated, it may undergo tearing of the annulus fibrosus collagen bundles, which is often a precursor to herniation of the nucleus pulposus, particularly at the posterolateral aspect of the disc. Protrusion is herniation of the nucleus pulposus that is contained by the annulus. In the axial plane, it usually demonstrates a base broader than the height against the parent disc (59). Extrusion is defined as a herniation of the nucleus pulposus beyond the fibers of the
The loss of the load-diffusing function of the normal disc also causes facet joint osteoarthrosis and marginal osteophytosis of the vertebral body ends (spondylosis deformans) by virtue of the increased loads these joints must bear.
Source: Physical Medicine and Rehabilitation - Principles and Practice
Other Hip Abnormalities
Written by Edgar Colón, Jorge Vidal, Eduardo Labat, Gory Ballester and Angel GomezAnother hip region imaging application of potential interest to physiatrists involves the use of technetium bone scanning to evaluate recently described “thigh splints” caused by exaggerated stride length by short female basic trainees in the unisex-oriented military (34). Seven cases of thigh pain in female recruits at one military base were imaged after administration of technetium-99, with the expectation of finding stress fractures. Instead, the scans showed longitudinal linear accentuation sites in the upper or middle femur that were consistent with periosteal elevation and corresponded with the sites of insertion of one or more of the adductor muscles (Fig. 6-21). The reason these findings occur only in female trainees is explained by a Saunders and colleagues’ classic description of pelvic rotation as the first of their six determinants of gait (35). Because the shorter female recruits had to march with taller males, their stride had to be lengthened to maintain straight lines of march, and exaggerating the normal pelvic rotation lengthens stride. The adductor muscles are important pelvic rotators, and their overuse apparently produced avulsion and elevation of the periosteum adjacent to their femoral insertions.
FIGURE 6-21. Thigh splint sites demonstrated by technetium-99 scintigraphy. The accentuation sites (arrowheads) correspond to the insertions of the adductor longus and magnus muscles.
Source: Physical Medicine and Rehabilitation - Principles and Practice
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