Muscular and Musculotendinous Rheumatism Syndromes

Muscular and musculotendinous rheumatism syndromes of both scintigraphic and radiographic interest include myositis ossificans, rhabdomyolysis, musculotendinous unit injuries, and distal femoral cortical desmoid.

12.8.1 Myositis Ossificans

Myositis ossificans denotes a condition in which the skeletal muscle is heterotopically ossified. The ossifying myositis caused by trauma is referred to as myositis ossificans traumatica and that unrelated to trauma is called myositis ossificans nontraumatica or pseudomalignant osseous tumor of soft tissue. According to Soule (1945), this condition is noninflammatory in nature and due to the alteration of peri-mysial connective tissue (fascia) and not the myocytes (muscle). It is generally accepted that the perimysial tissue, which induces the osteo-progenitor cells, is the source of heterotopic ossification (Friedenstein 1973). The causes include trauma and surgical damage in myositis ossificans traumatica and burns, paraplegia (Miller and O'Neill 1949), and autosomal mutation in myositis ossificans nontraumatica. The third type is myositis ossificans progressi-va. This is a rare inflammatory disease of mesodermal tissue; hence, it also referred to as fibro-dysplasia ossificans progressiva.

The radiographic features of muscular and musculotendinous ossification are similar regardless of etiology (Figs. 12.38A and 12.39A). However, the ossification in myositis ossificans

Fig. 12.38A, B Old myositis ossificans traumatica. A Lateral radiograph of the right elbow in a 15-year-old boy with myositis ossificans of the biceps muscle shows fusiform ossification in the antecubital fossa (open arrow). Fracture had occurred 9 months previously. The proximal ulna and distal humerus are the sites of old fractures with deformity and osteophytes (arrowheads). B Lateral pinhole scan shows mild tracer uptake in myositis (open arrow). Note marked tracer uptake in fractures and osteophytes (arrowheads)

progressiva is basically different from that of the other two types of myositis ossificans, and is characterized by diffuse sheet-like ossification that often connects different parts of the body such as the shoulder, rib cage, and pelvis.

Gastrocnemius Distal CalcificationLeft Shoulder Myositis

Fig. 12.39A, B Fresh myositis ossificans traumatica. A Oblique radiograph of the left ischium in a 9-year-old girl reveals barely visible amorphous calcification in the muscle below the ischium (solid arrow). Fracture is also faintly visualized with minimal callus formation (open arrow). B Oblique pinhole scan shows intense tracer uptake in both fracture (open arrow) and myositis (solid arrow). Note that tracer uptake in this fresh myositis ossificans is far more intense than that in the old myositis shown in Fig. 12.38B

Fig. 12.39A, B Fresh myositis ossificans traumatica. A Oblique radiograph of the left ischium in a 9-year-old girl reveals barely visible amorphous calcification in the muscle below the ischium (solid arrow). Fracture is also faintly visualized with minimal callus formation (open arrow). B Oblique pinhole scan shows intense tracer uptake in both fracture (open arrow) and myositis (solid arrow). Note that tracer uptake in this fresh myositis ossificans is far more intense than that in the old myositis shown in Fig. 12.38B

Like any diseases that involve heterotopic ossification, the bones formed in myositis ossifi-cans avidly accumulate tracer especially in an active phase so that the diagnosis can easily be suggested or made by 99mTc MDP scintigraphy. Thus, as described by Suzuki et al. (1974) and presented in Fig. 12.40, bone scintigraphy can very efficiently diagnose myositis ossificans even in the absence of radiographic evidence. Pinhole scanning is extremely sensitive, often showing subtle lesions that are not shown on ordinary planar scintigraphs. It can identify an

Muscular Rheumatism

Fig. 12.40A, B Myositis ossificans without radiographic alteration. A Anterior pinhole scan of the right hip in a 66-year-old paraplegic man shows tracer uptake in the gluteus muscle (open arrows). The lesion was an incidental finding on a bone scan performed for another purpose. The lesions were bilateral and confirmed by CT scan. B Anteroposterior radiograph showing no calcific density in the muscle (arrows, arrowheads)

Fig. 12.40A, B Myositis ossificans without radiographic alteration. A Anterior pinhole scan of the right hip in a 66-year-old paraplegic man shows tracer uptake in the gluteus muscle (open arrows). The lesion was an incidental finding on a bone scan performed for another purpose. The lesions were bilateral and confirmed by CT scan. B Anteroposterior radiograph showing no calcific density in the muscle (arrows, arrowheads)

individual muscle or muscle group affected (Figs. 12.38B and 12.39B). A further and unique advantage of this examination is that it can provide information on the metabolic acti-

Myositis Ossificans

Fig. 12.41A, B Postincisional myositis ossificans. A Anteroposterior radiograph of the left thigh in a 37-year-old woman shows derangement of the adductor muscle shadow due to surgical incision (arrows). No calcification is seen. B Anterior planar scan shows large fusiform tracer uptake indicating myositis in the adductor muscles (arrows)

Muscular Rheumatism

Fig. 12.42 Tracer uptake in a fresh incisional skin wound. Anterior bone scintigraph of the abdomen in a 69-year-old woman shows prominent linear uptake in a scar formed after laparotomy performed 6 days previously for gallbladder stone removal (arrows)

Fig. 12.41A, B Postincisional myositis ossificans. A Anteroposterior radiograph of the left thigh in a 37-year-old woman shows derangement of the adductor muscle shadow due to surgical incision (arrows). No calcification is seen. B Anterior planar scan shows large fusiform tracer uptake indicating myositis in the adductor muscles (arrows)

Fig. 12.42 Tracer uptake in a fresh incisional skin wound. Anterior bone scintigraph of the abdomen in a 69-year-old woman shows prominent linear uptake in a scar formed after laparotomy performed 6 days previously for gallbladder stone removal (arrows)

vity of a calcifying lesion in its evolutionary stage. Understandably, fresh lesions accumulate tracer far more avidly than old ones (Figs. 12.38B and 12.39B). Myositis ossificans may result from a surgical incision or an operative injury of skeletal muscles (Fig. 12.41). Incisional soft-tissue wounds accumulate tracer well within a week following an operation (Fig. 12.42), and mineralized foci may be presented as areas of discrete uptake of 99mTc-MDP within a few weeks (Fig. 12.43). Nuclear angiography and equilibrium phase scintigra-phy are ideal for noninvasive dynamic assessment of activity of myositis ossificans in terms of mineralization or calcification (Fig. 12.44).

12.8.2 Rhabdomyolysis

Also known as myonecrosis, this condition is characterized by diffuse skeletal muscular injury with the release of muscle cell contents into the blood plasma. A review of the condition has revealed that it is not an uncommon

Sono Hemoperitoneum

Fig. 12.43A, B Discrete tracer uptake in mineralized incisional scars. A Oblique bone scintigraph of the upper abdomen in a 46-year-old man shows two small spotty "hot" areas in a focally calcified scar formed after a laparotomy performed 3 weeks previously for the treatment of traumatic hemoperitoneum (arrowheads). B Sono-gram demonstrates small plaque-like calcium deposits with acoustic shadows (arrows)

Fig. 12.43A, B Discrete tracer uptake in mineralized incisional scars. A Oblique bone scintigraph of the upper abdomen in a 46-year-old man shows two small spotty "hot" areas in a focally calcified scar formed after a laparotomy performed 3 weeks previously for the treatment of traumatic hemoperitoneum (arrowheads). B Sono-gram demonstrates small plaque-like calcium deposits with acoustic shadows (arrows)

disorder (Gabow et al. 1982). The etiologies are many and varied (Lamminen 1996). The more common etiologies are excessive muscular activity (Matin et al. 1983; Valk 1984), direct muscular injury, ischemia, external compression, and ethanol intoxication (Koffler et al. 1976; Silberstein and Bove 1979). Pathology is characterized by swelling, hyalinization, de

Fig. 12.44A-D Nuclear angiography for disease activity assay of myositis ossificans. A Arteriography of the pelvis and hips in a 55-year-old hemiplegic woman with myosi-tis ossificans nontraumatica of the right gluteus muscles and fascias bridging the right ilium and femur shows increased blood flow (arrow). B Equilibrium pinhole scan reveals prominent tracer uptake in the gluteus and fascias denoting actively progressive mineralization (arrows). C Anteroposterior radiograph demonstrates large ill-defined areas of nebulous mineralization covering the right iliofemoral region (arrows). D Anteroposterior radiograph taken 2 years later shows fully mature heterotopic bones with trabeculation (arrows)

Fig. 12.44A-D Nuclear angiography for disease activity assay of myositis ossificans. A Arteriography of the pelvis and hips in a 55-year-old hemiplegic woman with myosi-tis ossificans nontraumatica of the right gluteus muscles and fascias bridging the right ilium and femur shows increased blood flow (arrow). B Equilibrium pinhole scan reveals prominent tracer uptake in the gluteus and fascias denoting actively progressive mineralization (arrows). C Anteroposterior radiograph demonstrates large ill-defined areas of nebulous mineralization covering the right iliofemoral region (arrows). D Anteroposterior radiograph taken 2 years later shows fully mature heterotopic bones with trabeculation (arrows)

generation, and regeneration of muscle fibers (Armbrustmacher 1988). When muscle fibers disrupt, myoglobin escapes into the extracellular fluid and plasma, resulting in myoglo-binemia, frequently causing acute renal failure. Plasma creatine kinase is elevated. In contrast to myositis ossificans, in which perimysial connective damage prevails, myocytes are mainly affected in rhabdomyolysis. Clinically, half of the cases are indolent, and in the majority of cases objective symptoms and signs are absent (Gabow 1982).

Radiography is not helpful in the diagnosis of rhabdomyolysis, although it can be utilized to exclude inflammatory and calcifying muscular disorder (Fig. 12.45). CT is characterized by low attenuation in affected muscles (Fig. 12.45B) and MRI reveals streaky or mottled high-intensity edema in necrotized muscles on T2-weighted images (Fig. 12.46C).

99mTc-MDP bone scanning has been widely used for the diagnosis of rhabdomyolysis since the first reports of Haseman and Kriss (1985) and Patel and Mishkin (1986). It is a highly reliable and sensitive examination. Procedures include whole-body scintigraphy for systemic survey (Fig. 12.46A) and pinhole scintigraphy for the identification of a specific muscle or muscle group (Figs. 12.45A and 12.46B).

Fig. 12.45A-C Compression rhabdomyolysis. A Anterior pinhole scan of the left hip in a 69-year old bed-ridden man with lung cancer reveals fusiform tracer uptake in the gluteus medius muscle (arrows) (fh femoral head). B Transaxial CT scan at the level of the femoral head top (fht) reveals low attenuation with hypodense foci in the gluteus medius muscle (pair of arrows) and gluteus maximus muscle (single arrow), denoting edema and necrosis. C Anteroposterior radiograph of the hip shows the gluteal muscles in question to be unremarkable (white arrows). Incidentally, there is calcific trochanteric bursitis (long arrow), which does not concentrate tracer. The lesion was asymptomatic

Gluteus Maximus Scan Musculotendinous Unit

12.8.3 Musculotendinous Unit Strain or Injuries

The musculotendinous unit is the portion of a muscle attached to a tendon, tendinous insertion, or enthesis, and strain is defined as a stretching or tearing of the musculotendinous unit (Baker 1984). According to the nature and extent of damage a strain can be graded as first, second, or third degree. The first grade indicates minimal stretching of the musculotendinous unit without permanent injury, the second grade partial tearing, and the third grade complete disruption of a portion of the unit. Among a number of musculotendinous injuries, rotator cuff syndrome, strain of the biceps muscle or triceps muscle, tennis elbow, De Quervain's tenosynovitis, and strain of the quadriceps femoris muscle and the gastrocne-mius-soleus muscle are well known.

Soft-tissue radiography may be used to diagnose injuries in the musculotendinous unit. However, diagnostic yields are generally low and information is not specific except for calcification. Contrast arthrography can accurately delineate musculotendinous injuries and tendon rupture, especially in the shoulder, whose anatomy is complex. MRI, a noninvasive modality, is extremely useful for the investigation of soft-tissue anatomy and pathology (McNamara and Greco 1996) and sonography is increasingly used for the same purpose. 99mTc MDP bone scanning is another noninvasive method. It can sensitively detect injured muscle and tendon. Unless injuries are negligible, pinhole magnification can nearly always show increased uptake of various degrees, identifying the specific muscle or muscle group damaged (Fig. 12.47).

Fig. 12.46A-C Rhabdomyolysis in the lower extremities. A Anterior and posterior whole-body bone scans in a 34-year-old bed-ridden man with cervical fracture and quadriplegia show diffuse tracer uptake in the muscles in the thighs and lower legs (arrows). B Lateral pinhole scin-tigraph of the right lower leg distinctly visualizes and distinguishes the medial (between open arrows) and lateral head of the gastrocnemius muscle (solid arrows) and per-oneus longus muscle (plm). C T2-weighted sagittal MRI shows longitudinal striations of high signal intensity, denoting muscular edema. Note that the muscles are diffusely wasted and thin

12.8.4 Distal Femoral Cortical Irregularity

Distal femoral cortical irregularity, also known as cortical or periosteal desmoid, is characterized by concave, convex, or divergent irregularity of the cortex in the popliteal surface of the distal femur and the epicondyle. One of the first descriptions is due to Kimmelstiel and Rapp (1951). Typical sites of involvement are the attachment of the gastrocnemius muscle head, mostly the medial one (Suh et al. 1996) or adductor magnus muscle. It is not a neoplasm but a traumatic lesion of the musculotendinous unit (Resnick and Greenway 1982), and is considered by some investigators as a variation of ossifying periostitis (Mirra 1989). Pathologically, the condition is characterized by fibrin with mineralization, suggesting a reparative process. In one recent series, the average age of the patients was 34 years, ranging from 4 to 64 years (Suh et al. 1996). The lesions may cause pain in occasional cases.

Radiography shows cortical irregularity that is usually subtle and unimpressive (Fig. 12.48A). However, MRI can clearly show convex or concave aberration or the combination of both. To be exact, MRI of the concave type reveals a well-defined area of low signal intensity on T1-weighted images, which becomes enhanced with administration of gadolinium DTPA (Fig. 12.49A, B). We have performed pinhole bone scans in three patients with this condition: one patient showed ill-defined patchy uptake in the popliteal surface of the distal femur (Fig. 12.48B), and two patients showed well-defined roundish uptake (Fig. 12.49).

Fig. 12.47A, B Musculotendinous strain. A Oblique planar scans of both upper arms in a 26-year-old man who used dumb-bells show peculiar bundle-like tracer uptake in the musculotendinous units of the left upper arm muscles. The medial head unit (mhu) and lateral head unit (Ihu) of the triceps are clearly delineate (me medial epi-condyle of the humerus where the triceps muscles insert). There is an intense tracer uptake in the right medial epi-condyle (thick arrow) representing epicondylitis (reverse tennis elbow). B Lateral radiograph of the distal humerus showing musculotendinous units of the medial head (mhu) and lateral head (Ihu) of the triceps muscles

What Cortical DesmoidWhat Cortical DesmoidMedial Epicondylitis Elbow Radiograph

Fig. 12.48A, B Distal femoral cortical desmoid. A Lateral radiograph of the left distal femur in a 31-year-old woman with focal pain shows concave cortical irregularity in the posterior aspect of the distal femur (arrow and arrowheads). B Lateral pinhole scintigraph reveals an ill-defined area of intense tracer uptake surrounded by a less intense zone denoting main and reactive lesions, respectively (arrow)

Cortical Desmoid

Fig. 12.49A-C Cortical desmoid in the lateral femoral condyle. A Transaxial T1-weighted MRI of the left femoral condyle in a 54-year-old woman with regional pain shows a small roundish area of low signal intensity in the posterior aspect of the lateral femoral condyle (left, arrow). The lesion is enhanced after gadolinium infusion (right, arrow). B Sagittal T1-weighted MRI shows a sharply defined small, roundish lesion with enhancement (arrow). C Lateral (left) and anterior (right) pinhole scans show a characteristic small, roundish hot area in the upper posterior aspect of the lateral femoral condyle (arrow). Note that the lesion in this particular case is not in the medial femoral condyle, but in the lateral condyle

Hypoplastic Femoral Condyles
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