If widespread myalgia is more likely than joint pain \200 Establish there is muscle pathology rather than symp- toms perceived in muscles and occurri ng in other struc- tures (e.g. entheses) or referred from elsewhere (e.g. neurological or v ascular disease). The characteristic sites of tenderness in FM (p. 442) should be recognize d. However, in FM despite discom- fort muscles should be strong. Be careful about diagnosin g FM if there are tender points at entheses, which can occur in SpA or sarcoidosis. Tendern ess of plantar fascia origin and around hind feet would be relevant in this respect. The st rength testing of truncal and some limb muscles may be dif \201 cult in the presence of pa in. Patterns of muscle weakness are not disease speci \201 c. Characteristic patterns: sym metrical proximal limb and truncal in PM/DM (p. 282 and p. 290); quadriceps and forearm/ \201 nger \202 exors in inclusion body myositis; limb muscles in mitochondrial myopathy. Muscles in PMR are not intrinsically weak. Muscle wasting is not speci \201 c, but if prof ound and asso- ciated with a short history consider neoplasia. Basic tests in patients with polyarthropathy \200 Urinalysis (dipstick) can show proteinuria or haematuria \200\223 glomerular or tubular da mage are possible. ESR and CRP are often raised in autoimmune rheumatic/ connective tissue diseases, although they are non- speci \201 c and may be normal in the early stages of the se conditions. If very high (e.g. ESR > 100 mm/h) be suspi- cious of infection or malignanc y. ESR >50 mm/h is one diagnostic criterion of giant cell arteritis. There is often no acut e phase response in patients with enthesitis (even although pain and bony tenderness may be widespread). A mild normochromic normocytic anemia often accom- panies autoimmune connecti ve tissue or rheumatic diseases, infections, and malignancy. Throat swab, ASOT, anti-DNAase B antibodies (post- streptococcal condition). \200 WIDESPREAD PAIN (IN ADULTS) 22 Other simple blood tests, which should be considered given appropriate clinical evidence fo r the relevant dis- ease: random blood sugar, thyroid function tests/thyroid antibodies, li ver function tests, and prostatic speci \201 c antigen. Joint fluid aspiration and culture is mandatory for patients in whom sepsis is a possibility. Fluid should be examined by pol arized light microscopy in suspected cases of crystal-induced synovitis. Testing serum for extractable nuclear antigens (ENAs) may be useful for characterizing the type of autoimmune process. None should be considered alone to be diag- nostic or speci \201 c for any disea se, although diagnostic information is available from certain positive or negative associat ions. In most patients presenting with a short history of widespread joint pains, radiograp hs will be normal. Referral to a sexual health clinic for detailed investiga- tions if ther e \200\231s a suggestion of recent or recurrent genital infection/symptoms may help to stre ngthen the evidence for a diagnosis of reactive arthritis. likely if studied in the acute rather than the chronic phase of the illness. In the acute c ondition denervation and muscle degeneration give rise to \201 brillation poten- tials in 74% of PM and 33% of DM patients. Other features include low-amplitude short-duration moto r unit and polyphasic potentials. Electromyography is poor at discriminating on-going muscl e in \202 ammation in myositis from steroid-induced myopathy. There are characteristic MR patterns of abnormality in PM/DM. Images can be used to identify potential muscle biopsy si tes to avoid false-negative results associated with patchy muscle in \202 ammation. Muscle biopsy \200 With sizeable tissue samples from affected muscle and judicious use of a range of laborator y techniques, diag- nostic information can be provided. Differential diagnosis needs to be discussed with the pathologist whilst plan- ning the biopsy. Myositis may be patchy and bio psy may miss affected muscle. MR is sensitive in identifying areas of muscle in \202 ammat ion. In PM, inflammatory infiltrates predominate in the endomysial area around muscle \201 bres without perifas- cicular atrophy. In DM in \202 ammation is prominent in the per imysial area and around small blood vessels and there is typically perifascicular atrophy. Routine tests do not reliably distinguish PM from cases of viral myositis. Some of the glyc ogenoses will become obviously apparent from light microscopy of biopsy material. Basic laboratory tests in patients with widespread muscle pain/weakness \200 Dipstick urinalysis: to screen for haematuria or myoglobinuria. FBC (CBC) and measures of a cute-phase response. An endocrine and metabolic screen: urea, electrolytes, creatinine, thy roxine and thyroid-stimulating hormone (TSH), blood calcium, phosphate, and 25-hydroxyvitam in D, LFTs. Elevated CK occurs in most cases of PM. Creatine kinase (CK), ALT, AST, LDH are non-speci \201 c markers of muscle damage. Speci \201 c muscle iso-enzymes of CK and LDH exist and normal range of all enzymes may vary in differ- ent populations probably mainly as a function of muscle bulk (e.g. Afro-Caribbean > Caucasian). Muscle enzymes can be eleva ted after non-in \202 ammatory muscle damage, e.g. exercise/trauma. Check for ANA and, if positive, screen for ENAs. Antibodies to certain (cytoplasmic) tRNA synthetases (e.g. Jo-1) are myositis-speci \201 c. All of the above tests may reasonably be done in cases where m uscle pains might be due to \201 bromyalgia, but other pathology needs excluding. Check f or urinary myoglobin in cases where acute wide- spread muscle pain may be associated with e xcessive alcohol or ingestion of certain drugs (cocaine, ampheta- mines, ecstacy, heroin), exercise or trauma. Patients will be at risk of renal failure. PM can be the presenting fea ture of HIV disease. Consider testing HIV serology. In HIV-positive patients, infections ca using muscle disease include TB and microsporidia. Viral myositis is often clinically indis tinguishable from PM. Serology, and PCR of muscle tissue or in \202 ammatory cells may rev eal diagnostic clues. \200 Investigations for malignancy Investigations in adults with widespread muscle or bony pain should aim to rule out malignancy, particularly myeloma and semalignancies from breast, ren al, and prostate cancers. \200 Investigations may include breast US, mammography and MR, urine cytology, PSA, renal US, se rum, and urinary protein electrophoresis. Hypercalcaemia may accompany these conditions, th us check blood calcium, phosphate, and albumin. PTH should be checked in suspected cases of osteoma- lacia (raised s to calcium/vitamin D de \201 ciency) together with 25-hydroxyvit amin D levels (low or low/normal), and ALP (high/normal). Bone scintigraphy can identify si tes of neoplasia, Paget \200\231s disease, severe osteomalacia. Bone biopsy (maintained und ecalci \201 ed by placing sample in 70% alcohol) of affected sites will be diagnostic in s ome, but not all, cases of osteomalacia, osteoporosis, renal osteodystrophy, malignancy, an d Paget \200\231s disease. Good samples are hard to obtain. The best samples are obtained f rom a transiliac biopsy. Bone marrow can be aspirated for examination at the same time. Electrophysiology and imaging in patients with muscle conditions \200 Electromyographic abnormalities occur in 60 \200\22370%of patients with muscle in \202 amm ation. More information is 23 Chapter 2 Investigation of rheumatic disease Plain radiography 24 Ultrasound 26 Computed tomography 30 Magnetic resonance imaging 34 Rad ionuclide imaging 36 Autoimmune serology 38 Synovial \202 uid analysis 42 Clinical neurop hysiology 44 PLAIN RADIOGRAPHY 24 Plain radiography Localized osteopaenia occurs in: Rheumatoid arthritis, when it occurs in a peri-articular d istribution and re \202 ects increased bone turnover and resorption. Regional migratory os teoporosis. Complex regional pain syndrome and disuse atrophy. The initial stages of osteom yelitis. Early lytic Paget \200\231s disease (osteoporosis circumscripta). Focal lesions of bone, such as metastases and myeloma. Generalized osteopaenia occurs in: Senile osteoporos is with subsequent fracturing. Osteomalacia as a result of poor quality osteoid. Hyperparat hyroidism. Haemochromatosis. Diffuse metastatic disease or myeloma. Drug therapy, particula rly long-term high dose steroids. Osteogenesis imperfecta. Plain films remain the most commonly used imaging modality for the investigation of rheumat ic disease despite the advent of more complex techniques. There are a number of reasons for this: \200 \200 \200 \200 \200 Plain \201 lms are convenient for patients, cheap and repro- ducible. This allows direct comparison between \201 lms taken at different times and at different sites in the follow -up of patients. The resolution of X-ray \201 lm exceeds that of MRI, CT, ultrasound or n uclear medicine, providing exquisite detail of \201 ne bony architecture. The body of kno wledge of the radiology of rheumatic disease is based on plain \201 lm appearances, and i t remains the most useful imaging technique for discriminating between the various arthropa thies. \200 \200 \200 \200 \200 \200 Disadvantages \200 Plain \201 lms involve ionizing radiation and this needs to be taken into consideration i n their use. For instance a lumbar spine \201 lm has the equivalent radiation dose of 50 chest X-rays. They are insensitive in the early stages of many diseases. They provide at be st limited evidence of soft tissue pathology, such as tendon rupture. \200 Indications Plain \201 lms are the usual imaging technique for the initial investigation of a symptomatic joint or joints, and serial imaging allows assessment of disease progressi on or response to therapy. Whilst plain \201 lms are commonly used in the investigation of any symptomatic joint, th e hands are most often imaged for initial assessment and follow-up of localized and more ge neralized arthralgia. The standard view is the antero- posterior (AP) projection of both ha nds. This allows assessment of both the nature of any radiographic change and its distribut ion. Figure 2.1 Early gout arthropathy with peri-articular soft tissue swelling and calci \201 cation. Plain \201 lms can also be useful in the evaluation of joint stability. For example, late ral views of the cervical spine in \202 exion and extension allow assessment of instabili ty at the craniocervical junction in patients with rheumatoid arthritis. Plain \201 lm \201 ndings The following are the major \201 ndings seen on plain \201 lms in rheumatol ogical disease. They are described in relation to the hands in line with clinical practice and for ease of comparison, except where otherwise speci \201 ed. Soft tissue swelling (Figure 2.1) Peri-articular soft tissue swelling often re \202 ects s ynovitis, and until the advent of ultrasound and MRI was often the earliest radiological \201 nding in arthritis. It also occurs in: \200 Joint effusions or bursal distention (e.g. pre-patellar bursitis). Dactylitis. Soft tissue injuries. Crystal arthropathy, when calci \201 c deposits may be seen in the soft tissues or cartilage (CPPDD). \200 \200 Figure 2.2 Rheumatoid arthritis with subtle ulnar deviation of MCP joints and peri-articula r osteopaenia and erosions. Osteopaenia (Figure 2.2) Osteopaenia is de \201 ned as reduction of bone quantity whilst m aintaining quality, whereas osteoporosis speci \201 - cally re \202 ects reduced osteoid production. CHAPTER 2 Investigation of rheumatic disease 25 Sclerosis (Figure 2.3) Subchondral sclerosis is seen in osteoarthritis accompanied by reduc ed joint space and subchondral cyst formation, but localized sclerosis may also occur in: \200 \200 \200 \200 \200 Avascular necrosis and bone infarcts. Osteomyelitis. Paget \200\231s disease. Fibrous dyspl asia. Benign focal lesions, such as bone island, osteoid osteoma and healing fractures. Pri mary and secondary bone tumors. Generalized sclerosis is seen in: Myelo \201 brosis. Diffu se metastatic disease. Sickle cell disease. Advanced Paget \200\231s disease. Polyostotic \201 brous dysplasia. Renal osteodystrophy. Hypoparathyroidism and pseudohypoparathyroidis m. \200 \200 \200 \200 \200 \200 Erosions (Figure 2.2) Erosions represent focal cortical lucencies and occur as a result of local in \202 ammation. They are seen in: \200 \200 Figure 2.4 Hyperparathyroidism with widespread acro-osteolysis, and sub-periosteal resorpti on of bone affecting the index \201 nger middle phalanx. Rheumatoid arthritis. Psoriatic arthritis, unlike rheumatoid arthritis (RA) tending to affe ct the DIP joints. Reiter \200\231s syndrome, which primarily affects in the feet. Erosive (in \202 ammatory) osteoarthritis. Ankylosing spondylitis, especially at the margins of ve rtebrae (preceding the sclerotic \200\230shining corner \200\231 or Romanus lesion). Gout, in which the erosions are adjacent to the articular surface and have the typical appearanc e of an overhanging edge and sclerotic margin ( \200\230rat bite \200\231 erosion). Hemophi lia. Acro-osteolysis (erosion of the terminal tufts) occurs in psoriatic arthritis, sclerod erma, hyperparathyroidism and Sj gren \200\231s syndrome (Figure 2.4). Bone proliferation (Figure 2.3) The osteophyte is the hallmark of osteoarthritis, but bony proliferation may also be seen in: \200 \200 \200 In \202 ammatory spondyloarthropathy, in which there is new bone formation at the enthesis (e.g. syndesmophyte). Diffuse idiopathic skeletal hyperostosis (DISH). Healing fractures. Bone-forming tumors. \200 \200 \200 Other \201 ndings Joint Space (Figure 2.3) The joint space may be increased in the presence of active synovit is which distends the joint. Joint space reduction is a hallmark of osteoarthritis, and is also a feature of psori- atic arthritis, CPPDD, and haemochromatosis. It is less common in gout, sarcoidosis, scleroderma, and is seen only late in rheumatoid arthritis. Malalignment (Figure 2.3) Joints may become malaligned sue to asymmetric loss of joint spac e, such as in the genu vara deformity seen in osteoarthritis. Subluxation and dislocation m ay occur in advanced rheumatoid arthritis as a result of ligamentous instability (Figure 2. 2). Periosteal reaction In rheumatological practice this is seen in Reiter \200\231s syndrome, juvenile idiopathic arthritis (JIA) and psoriatic arthritis. It is also seen in bone tumors , osteomyelitis, healing fractures, hypertrophic osteoarthopathy, thyroid acropachy, and ve nous stasis. Subperiosteal resorption of bone is a characteristic feature of hyperparathyro idism (Figure 2.4). Lucencies Subchondral cysts are a hallmark of osteoarthrosis, and are also seen in hemophil ia, amyloidosis, and haemochro- matosis. Figure 2.3 Osteoarthritis of the knee with joint space narrowing, subchondral sclerosis, pe ripheral osteophyte formation, and varus deformity. ULTRASOUND 26 Ultrasound Ultrasound has only fairly recently been introduced in musculoskeletal cases and its use is expanding rapidly. Unlike other modalities ultrasound enables clinical correla- tion as th e radiologist is with the patient while performing the scan. Advantages \200 Unlike plain \201 lms, computerized tomography (CT) and nuclear medicine, it does not inv olve ionizing radiation. It is quick to perform and well tolerated by patients. It is cheap er to perform than CT and magnetic resonance imaging (MRI). The apparatus is portable and s o can be used in clinic or at the bedside. It provides excellent resolution of soft tissues , including assessment of neovascularity with Doppler imaging. It allows precise real-time targeting of needles for diag- nostic and therapeutic intervention. \200 Figure 2.5 Normal MCP joint with the articular cartilage clearly seen as a thin black strip e on the metacarpal head (arrows). Disadvantages \200 It is operator dependant to a greater extent than other modalities, which may make follow-u p assessment less accurate. It is only able to assess the bone surface so cannot identify m arrow oedema or pure bony abnormalities. Indications Clinical indications for ultrasound in rheumatological practice include, but ar e not limited to: \200 Figure 2.6 Synovitis of the thumb macrophage chemotactic protein (MCP) joint with an effusi on and hyperaemia. An erosion is present (arrow). Assessment for synovitis and/or taenosynovitis in early arthralgia, thereby allowing prompt initiation of disease- modifying antirheumatic drugs. Erosions are also well demonstrated. Assessment of rotator cuff pathology. Unlike MRI, ultrasound allows dynamic scanning to in vestigate impingement, and is the initial investigation of choice for rotator cuff patholog y in many institutions in the UK. Investigation of masses such as ganglia. Investigation of functional problems such as trigger \201 nger. Guiding diagnostic and/or therapeutic inj ections, including bursal injections and joint aspirations. Each of these stages can be accurately identi \201 ed on ultra- sound. The earliest signs are thickening, hypo-echogenicity and loss of the normal \201 brillar pattern. Tears are seen as focal hypo-echoic clefts or defects, and the frayed ends of ruptured tendons can be localized prior to repair or reconstruction (Figure 2.7). Normal tendons contain no identi \201 able blood vessels, and their presence is a further indicator of tendon pathology. \200 \200 Taenosynovitis usually appears as hypo-echoic \202 uid dis- tending the sheath surroundin g the tendon. It can contain echogenic hypertrophied synovium (Figure 2.8) and may or Joints (Figure 2.5) Synovitis Ultrasound is becoming increasingly utilized in the investi- gation and management of early arthralgia as it can detect synovitis at an earlier stage th an plain \201 lms, and is of comparable sensitivity to MRI, but signi \201 cantly more c on- venient and cheaper. Synovitis is seen as soft tissue proliferation arising from a joint with or without an effu sion (see Figure 2.6). As expected it is hyperaemic on power Doppler scanning. Other \201 ndings In addition to synovitis, ultrasound is accurate in assess- ment for th e presence of joint effusions and the constella- tion of abnormalities seen in osteoarthros is including osteophytes, loose bodies, capsular proliferation and joint space narrowing. T endon abnormalities Tendon degeneration spans a continuum from mild tendinosis through part ial tears to complete rupture. Figure 2.7 Ruptured Achilles tendon. The frayed ends (white arrows) are clearly seen and ca n be marked prior to reconstruction. The defect is \201 lled with echogenic haematoma. CHAPTER 2 Investigation of rheumatic disease 27 Soft tissue masses Ultrasound is a valuable tool in the investigation of super \201 - cial soft tissue masses due to its excellent spatial resolution and Doppler assessment. Ganglia are seen as lobulated, septated \202 uid collections in characteristic locations such as the dorsum of the wrist (Figure 2.10). The neck of the ganglion can usually be followed to an underlying joint or ligament. Lipomas are also well seen, except benign unen- capsulate d super \201 cial lipomas, which are indistinguishable from the normal subcutaneous fat. V ascular malformations are usually soft masses with varying amounts of fat but are strikingl y hypervascular (Figure 2.11). Their feeding vessels can often be traced. Malignant soft ti ssue masses are also well seen, but ultrasound has limited speci \201 city and MRI scannin g is usually required. Figure 2.8 Taenosynovitis of the tibialis posterior tendon (white outline). The tendon shea th (red outline) is distended and contains echogenic synovium. may not be associated with tendon abnormalities. The exception is De Quervain \200\231s tae nosynovitis, which affects the extensor group one tendons at the wrist (abductor pollicis l ongus and extensor pollicis brevis). This is a ste- nosing taenosynovitis, which appears as a thickening of the tendon sheath with little or no associated \202 uid. Type 1 tendons, such as the Achilles are not surrounded by a ten- don sheath, instead there is a layer of loose areolar tissue called paratenon. This too can become distended with \202 uid (parat endonitis). Functional tendon abnormalities such as triggering and subluxation are well demonstrated us ing dynamic scanning, when tendon excursion can be observed during active and passive movem ent. Bursae Bursae usually occur in recognized locations and are easily assessed with ultra sound. When in \202 amed they are usually seen as hyporechoic foci with a hyperechoic marg in. The subacromial-subdeltoid bursa (Figure 2.9) is often distended in patients with rotat or cuff symptoms, and can be seen overlying the supraspinatus tendon. Dynamic scanning dur- ing shoulder abduction may show \201 lling of the bursa and/or bunching up of the tendon \201 bres under the acromion and/ or coraco-acromial ligament and con \201 rms impingme nt. Figure 2.10 Ganglion arising from the dorsum of the wrist, seen as a lobulated and septated \202 uid collection. The distal radius (RAD), lunate (LUN) and capitate (CAP) have been marked. Figure 2.11 Vascular malformation over the thenar eminence with a prominent feeding vessel. Intervention The use of ultrasound to guide interventional procedures in the musculoskeleta l system is increasing rapidly. It enables real-time visualization of needle position and s o is likely to reduce the risk of injections or biopsies being inaccurate. Interventional procedures performed with ultrasound include: \200 Therapeutic injection of corticosteroid into tendon sheaths, joints or bursae (Figure 2.12) . Diagnostic injection of local anesthetic into joints, for example, into the hip to distin guish between lumbar and hip origins of leg pain. Aspiration of joints, tendon sheaths, or soft tissue collec- tions when infection is being considered. Figure 2.9 Distended and in \202 amed subacromial-subdeltoid bursa (white arrows). The hum eral head (HUM), supraspinatus tendon (SST) and overlying deltoid (DELT) are shown. The pre-Achilles, pre-patellar, intermetatarsal, iliopsoas, trochanteric, olecranon, and se mimembranosus-medial head of gastrocnemius (Baker \200\231s cyst) bursae are amongst those also frequently visualized. They may contain hyper- trophied synovium or loose bodies. ULTRASOUND 28 Dry needling of tendonitis and enthesitis, e.g. tennis elbow, plantar fasciitis, and Achill es tendonitis. This is usually accompanied by steroid in \201 ltration into the adja- cent soft tissues. The injection of autologous blood into damaged tendon may be used in refract ive cases. Barbotage and aspiration of calci \201 c tendonitis. Aspiration and barbotage o f ganglia. Biopsy of soft tissue masses. This is often done to con- \201 rm or exclude a sarcoma, in which case it should only be performed under the clear direction of the surgeon who would perform any subsequent resection. This is important because the biopsy tract nee ds to be excised at operation, and the procedure needs to be planned to avoid contamination of adjacent compartments. \200 \200 Figure 2.12 Ultrasound-guided injection of corticosteroid into the tendon sheath of tibiali s posterior. The needle is seen entering from the left with echogenic steroid \201 lling the distended sheath. This page intentionally left blank COMPUTED TOMOGRAPHY 30 Computed tomography CT is a well established modality for imaging across the clinical spectrum. The recent intr oduction of multislice scanners allows detailed imaging of the musculoskeletal system. Advantages \200 \200 \200 \200 \200 Excellent detail of bone. Greater spatial resolution than MRI. Quick and generally well tol erated by patients. Widely accessible modality. Multidetector CT (MDCT) scans with multipla nar reconstructions allow joints to be viewed from many angles (Figure 2.13). 3D reconstruc tions can also be made and are particularly useful in trauma. High resolution CT (HRCT) of the chest is more sensi- tive than chest X-ray in assessing for the presence of pulmonary \201 brosis or other interstitial processes. May be helpful if MRI is contraindicated (e.g . CT arthro- gram in lien of MRI Knee). Can be used to guide interventional procedures, par ticularly in the spine. Figure 2.14 Axial CT showing an osteoarthritic glenohumeral joint prior to replacement. Not e the reduced joint space, marginal osteophytes and subchondral sclerosis of the humeral he ad, and subchondral cysts in the glenoid. In assessing advanced in \202 ammatory spondyloarthritis, in particular the extent of any ankylosis in the spine. It provides excellent detail of the sacroiliac joints, but MRI is o ften preferred in the early stages when marrow oedema precedes structural bone alteration. To accurately localize a lesion within bone, such as a cortically-based osteoid osteoma. Disadvantages \200 CT involves ionizing radiation in signi \201 cant dose. For example a CT of the lumbar spi ne is equivalent to 500 chest X-rays. Limited soft tissue detail, and early changes such as marrow oedema cannot be identi \201 ed. Image quality is degraded in the presence of meta llic prostheses or \201 xation devices. Trauma CT imaging of the body is widely used in the context of acute trauma to exclude visc eral or head injury. While plain \201 lms are usually the initial modality for skeletal t rauma, CT is used to assess complex fractures, to exclude fractures where plain films are i nconclusive, and for follow-up of fractures and their fixation. Examples include: \200 Assessment of bony detail in spinal injuries. Sagittal and coronal reconstructions are espe cially useful (Figure 2.15) particularly if there is pre-existing spinal disease, such as a nkylosing spondylitis. Assessment of pelvic fractures, when 3D reconstruc- tions are often performed (Figure 2.16). Figure 2.13 Single image from a CT of a normal wrist reconstructed in the coronal plane. No te the excellent bone but limited soft tissue detail. Clinical applications CT is useful in a number of clinical scenarios. Arthropathy \200 CT is particularly useful prior to joint replacement in order to assess the state of the ar ticular surfaces, e.g. the glenoid prior to shoulder replacement (Figure 2.14). To quantify the extent of bone destruction in processes such as septic arthritis. Figure 2.15 Sagittally reconstructed CT of the lumbar spine showing a burst fracture of L1, with a large retropulsed fragment lying in the spinal canal. CHAPTER 2 Investigation of rheumatic disease 31 Intervention CT is used to guide interventional procedures in the musculoskeletal system an d elsewhere, for example: \200 Spinal nerve root blocks and facet joint injections. \200 Bone biopsy. \200 Lung and other visceral biopsy, particularly in the pelvis and retrop eritoneum. Chest imaging CT of the chest is used to further assess masses or other abnormalities seen on chest X-ray. In rheumatological practice these may include: \200 \200 \200 Granulomas in Wegener \200\231s disease. Nodules or pleural effusions in rheumatoid arthrit is. Parenchymal masses, and/or mediastinal or hilar lymph nodes in sarcoid. Primary or seco ndary malignancy. High resolution CT (HRCT) is the optimum modality for imaging the pulmona ry parenchyma in the context of suspected interstitial lung disease. It achieves resolution of up to 300 m and visualizes the secondary pulmonary lobule. Typical \201 ndings incl ude: \200 Figure 2.16 3D reconstruction of the bony pelvis showing a fractured posterior right acetab ular wall. \200 To con \201 rm or exclude non-union of fractures. In the investigation of pars defects, pa rticularly if surgery is being considered (Figure 2.17). CT arthrography or myelography is occasionally used in patients in whom MRI is contraindicated (Figure 2.18). Basal \201 brosis and honeycombing in usual interstitial pneumonia (UIP, Figure 2.19), which is associated with rheumatoid arthritis and some drugs. Basal \201 brosis and a dil ated esophagus in scleroderma. Upper lobe \201 brosis in ankylosing spondylitis or sarcoi dosis. Perilymphatic nodules, irregular septal thickening and traction bronchiectasis among st other \201 ndings in sarcoidosis. \200 \200 Figure 2.17 Sagittally reconstructed CT of the lumbar spine showing pars defects at L4 and L5 (white arrows). Figure 2.19 HRCT of the chest showing bibasal \201 brosis and honeycombing. These appeara nces may be seen in rheumatoid arthritis and other collagen vascular diseases. Other applications Further applications of CT in rheumatological practice include: \200 To investigate the sinuses and orbits in, for instance, Wegener \200\231s granulomatosis or lymphoma (Figure 2.20). CT angiography may be helpful in imaging the vascular system in po lyarteritis nodosum or other vasculitides. To investigate abdominal masses, such as splenom egaly in SLE, rheumatoid arthritis, or sarcoidosis. To accurately assess the craniocervical junction in rheumatoid arthritis, particularly in the pre-operative situation. Figure 2.18 CT arthrogram of the knee showing a tear of the medial meniscus (white arrows). COMPUTED TOMOGRAPHY 32 Figure 2.20 Sagittally reconstructed CT of the sinuses showing gross mucosal thickening and destruction of the inferior turbinate on the right in Wegener \200\231s. This page intentionally left blank MAGNETIC RESONANCE IMAGING 34 Magnetic resonance imaging MRI has only become widely available in the NHS within the last 10 years. It has a wide ran ge of applications, with musculoskeletal imaging (including spine) forming a signi \201 - cant proportion of cases scanned. sensitive in the early stages of the process. However it remains unclear whether all those with an abnormal MRI will go on to develop a full-blown in \202 ammatory spondylo- arthopa thy. Other advantages include: \200 The ability to assess adjacent structures in the same examination, e.g. hips, pelvis and pr evertebral structures. Repeat imaging can be used to assess disease response or progression . Reliable distinction between degenerative and in \202 amma- tory processes. Infective di scitis and osteomyelitis are well seen (Figure 2.23). Advantages \200 It does not involve ionizing radiation, but instead forms images from electromagnetic radia tion. This makes it a generally safe technique; Excellent soft tissue detail and contrast ( Figure 2.21). It is the best modality for assessing bone marrow, and so is sensitive in the early stages of many diseases. Its ability to assess soft tissue and bone together, and in detail sets it apart from other modalities. MR arthrography has largely replaced conventio nal diag- nostic arthroscopy, e.g. in imaging the glenoid labrum. \200 Figure 2.22 Coronal T2 fat saturated MRI of asymmertic sacroilitis, with marrow oedema (sol id arrows) and erosions (broken arrows). Figure 2.21 Axial T2-weighted MRI of a normal ankle showing the tendons of peroneus longus (solid arrow), peroneus brevis (PB), \202 exor hallucis longus (FHL), Achilles (A), \202 exor digitorum longus (broken arrow), and tibialis posterior (short arrow). The poster ior tibial neurovascular bundle lies between FHL and FDL. The extensor tendons are seen ant eriorly. Disdvantages \200 \200 It is more expensive than other modalities. It is time consuming, with scans lasting from 2 0 min to 1 hour. It is also very sensitive to movement artifact. Many patients suffer from claustrophobia and cannot complete the examination. It is absolutely contraindicated in pat ients with devices such as cardiac pacemakers and neural stimulators. Whilst very sensitive to early disease processes, speci \201 - city can be limited. For example a joint effusio n and syn- ovial proliferation require contrast to be distinguished as both are of similar signal on unenhanced imaging. Figure 2.23 Sagittal T2 fat saturated MRI of the lumbar spine showing endplate destruction and a \202 uid collection in acute infective discitis. Appendicular skeleton In \202 ammatory disease of bone, joints and soft tissues in the per ipheral skeleton is well demonstrated on MRI. Examples include: \200 MRI in in \202 ammatory disease Spine MRI plays an important role in the investigation of in \202 am- matory spondyloarthropathy (Figure 2.22). Whilst plain \201 lms and CT can o nly detect established bony changes, the ability of MRI to detect marrow oedema makes it ve ry Hip pathologies such as avascular necrosis, synovitis and trochanteric bursitis (Figure 2.2 4); Tendinopathy and taenosynovitis, e.g. at the ankle; Subacromial bursitis and rotator cu ff pathology; In \202 ammatory arthropathy with synovitis (Figure 2.25); \200 \200 CHAPTER 2 Investigation of rheumatic disease 35 \200 Entheseal changes, e.g. tennis elbow Muscle abnormalities such as myositis or wasting with fatty in \201 ltration. Figure 2.26 Coronal and sagittal T2 weighted images of a left paracentral disc herniation a t L5/S1 compressing the traversing left S1 root in the lateral recess (arrowheads comparing both). Less severe degenerative changes affect the L4/5 disc. Appendicular skeleton MRI is also very sensitive in the early stages of the degen- erative process in the remainder of the skeleton. Areas commonly imaged include: \200 \200 \200 \200 \200 MR arthrograms are sometimes performed to assess cartilaginous structur es, such as the labrum in the shoulder and hip, and articular cartilage surfaces in other j oints, triangular \201 brocartilagenous complex in the wrist. Hips Knees Ankles Shoulders Wrist Figure 2.24 Coronal T2 fat saturated image of the left hip showing high signal adjacent to the greater trochanter indicating trochanteric bursitis and/or gluteal tendinopathy (arrow) . MRI is also commonly used in trauma, both acute and chronic. A good example is in the inves tigation of osteo- chondral lesions which are most commonly seen in the knee and ankle (Fig ure 2.27). Figure 2.25 Sagittal contrast-enhanced T1 fat saturated MRI of the elbow in rheumatoid arth ritis, showing prominent enhancing synovitis (high signal) with erosions of the capitellum (solid arrow) and cartilage thinning on the radius (broken arrow). Degenerative disease Spine MRI is a fundamental part of the assessment of back pain, the ma jority of which is due to degenerative change affecting the intervertebral disks and/or the facet joints, with or without subsequent neural compression. MRI \201 ndings include: \200 \200 Figure 2.27 An osteochondral lesion is shown in the medial aspect of the talar dome. There is chondromalacia of the overlying articular cartilage. Loss of signal in and height of the intervertebral disks. Herniation of disc material causi ng compression of nerve roots in the lateral recess or exiting nerves in the intervertebral foramen (Figure 2.26). Spinal stenosis, which may cause cord compression, cauda equina syn drome or myelopathy. Spondylolisthesis, which may be due to facet joint degen- eration or p ars interarticularis defects. Vertebral end plate reactive changes. RADIONUCLIDE IMAGING 36 Radionuclide imaging Gamma camera imaging using radionuclides in the investi- gation of musculoskeletal cases is long established. Positron emission tomography (PET) imaging is a recent development whose role is expanding rapidly. All methods involve ionizing radiation with a dose to each pati ent. For example the effective dose from a bone scan equates to 200 chest X-rays. The image s generated are physiological, rather than anatomical as provided by other modalities (i.e. a bone scan is an image of the distribution of osteo- blastic activity, rather than of the bones themselves). Improved specificity has been repor ted using 99mTc-labeled IgG. The radiation dose is high er than plain \201 lms. Limited anatomical detail. Lesions where there is not increased o steoblastic activity will not demonstrate increased activity may be missed, e.g. plasmacyto ma. \200\230Cold spots \200\231 are areas of photopenia and occur where there is reduced o steoblastic activity compared with the surrounding bone and may be difficult to detect. Exa mples include \201 brous dysplasia and prostheses. Interpretation in the immature skeleto n is hampered by normal increased activity at the growth plates. \200 \200 Nuclear medicine Bone scan (Figure 2.28) Technetium-99m-labeled methylene diphosphonate (99 mTc-MDP) is incorporated into bone at a rate depen- dant on blood \202 ow and osteoblasti c activity. Rheumatological indications Indications for bone scan in rheumatological practice include: \200 Advantages \200 \200 Elevated serum markers but no localizing information (e.g. in Paget \200\231s disease). Inv estigation of painful prostheses. In complex regional pain syndrome (CRPS). Investigation o f metastatic disease (Figure 2.29). Cheap compared to MRI. Readily available with most radiology departments having gamma camer as on site. Excellent sensitivity to bone turnover. Increased uptake often precedes plain \201 lm changes. Whole body imaging allows investigation of non-speci \201 c abnormalitie s such as raised serum alkaline phosphatase. Early synovitis is seen as increased activity in the affected joint(s) and can be useful as a \200\230one shot \200\231 view, although i t has largely been superseded by ultrasound or MRI. Early images visualize perfusion and bl ood pool phases, and so identify hyperaemia in infection/in \202 ammation. Serial imaging enables follow-up. Improved anatomical detail with single photon emission computed tomograp hy (SPECT) imaging, in which the gamma camera rotates 360* around the patient provides impr oved lesion conspicuity and spatial resolution at the expense of increased time for image a cquisition. \200 \200 \200 Figure 2.29 Bone scan showing multiple areas of increased uptake of 99mTc-MDP in a patient with extensive skeletal metastases. A urinary catheter is in place. Other nuclear medicine applications Other applications of nuclear medicine include: \200 Ventilation-perfusion (V/Q) scans using 99mTc-labeled MAA for perfusion and aerosolized 99m Tc-DTPA for ventilation in the investigation of pulmonary emboli. A normal chest X-ray is r equired to obtain adequate information, otherwise a CT pulmonary angiogram is performed. In dium-111 or 99mTc can be used to label white blood cells in imaging for infection or in \202 ammation, e.g. in pyrexia of unknown origin, in \202 ammatory bowel disease, infected grafts (Figure 2.30) or osteomyelitis. 99mTc-pertechnetate and occasionally Iodine-123 are used to image the thyroid in the investigation of a palpa- ble mass, hyperthyroidism or th yroid malignancies. Iodine-131 is much higher energy and is used to treat active nodules, d iffuse toxic goiter and thyroid cancer. Figure 2.28 Bone scan showing mildly increased uptake of tracer at the CMC joints of both t humbs in keeping with osteoarthritis, but otherwise normal distribution of tracer. Disadvantages \200 Although sensitive to osteoblastic activity, it is not spe- ci \201 c, with increased upta ke seen in any area of increased bone turnover, including healing fractures, OA and other a rthropathies, neoplastic lesions (both primary and sec- ondary), infection, and avascular n ecrosis. Correlation with plain \201 lms or other modalities is often required.