High Yield Films II: Arthritides, Tumors, Infection, Metabolic Disease and Soft Tissue

Most films in a chiropractic office are not trauma films. They show degeneration, inflammation, a congenital surprise, a curve, a quiet lytic lesion, or a calcified aorta in front of the lumbar spine. In an imaging station, the candidate who can name the pattern, say why it fits, and attach the right recommendation (treat with modification, order the next test, or refer today) shows exactly the judgment the practical exam is built to score.

Section 1Arthritides on film

The ABCDS of arthritis

Every arthritis can be described with the same five headings, and saying them aloud in a station shows a method rather than a guess: Alignment (subluxation, deformity), Bone density (normal or periarticular osteopenia), Cartilage space (uniform or nonuniform narrowing, or preserved), Distribution (which joints, symmetric or not, axial or peripheral) and Soft tissue (swelling, tophi, calcification). Two further questions finish the analysis: are there erosions (marginal, central, or punched out away from the joint), and is there new bone (osteophytes, syndesmophytes, periostitis, ankylosis)?

Degenerative joint and disc disease

Degenerative joint disease (osteoarthritis) is cartilage failure with a bony repair response. The film shows nonuniform joint space narrowing where load is greatest (superolateral hip, medial knee compartment), subchondral sclerosis, osteophytes and subchondral cysts (geodes), with normal bone density. In the hands it involves the DIP joints (Heberden nodes), PIP joints (Bouchard nodes) and the first carpometacarpal joint, sparing the MCPs; erosive osteoarthritis adds central erosions that make a gull wing shape in the DIP joints.

In the spine, degenerative disc disease gives disc space narrowing, endplate sclerosis, the vacuum phenomenon (gas in a degenerated disc, which effectively excludes infection), and osteophytes that arise a few millimeters from the endplate margin, project horizontally and then curve toward the adjacent body. The posterior joints develop facet arthrosis (enlarged, sclerotic articular processes). In the cervical spine the uncovertebral joints hypertrophy and, with facet osteophytes, narrow the intervertebral foramina, best seen on the oblique views. Combined disc, facet and ligamentum flavum changes produce spinal stenosis, which plain films suggest but MRI confirms. Degenerative change is common and often painless, so the board answer links findings to symptoms rather than treating the film.

DISH

Diffuse idiopathic skeletal hyperostosis (Forestier disease) is a bone forming enthesopathy of older adults, more common in men and in people with diabetes and obesity. The diagnostic picture is flowing ossification along the anterolateral aspect of at least four contiguous vertebral bodies with preserved disc height, no significant facet ankylosis and normal sacroiliac joints (bridging of the upper, ligamentous part of the SI joint can occur). It favors the right side of the thoracic spine, because the pulsating descending aorta on the left inhibits it. A thin lucent line often separates the ossified ligament from the vertebral body. Peripheral entheses ossify too (heel and olecranon spurs, pelvic "whiskering"). DISH in the cervical spine can cause dysphagia, and it travels with ossification of the posterior longitudinal ligament (OPLL), which narrows the canal. A long ossified segment behaves like a long bone: it fractures with minor trauma and is unstable when it does.

Rheumatoid arthritis

Rheumatoid arthritis is a synovial disease, and its film signs follow: soft tissue swelling, periarticular osteopenia, uniform joint space loss, and marginal erosions at the bare areas where synovium touches bone not covered by cartilage, with little or no new bone. It is bilateral and symmetric in the MCP, PIP and wrist joints (an early erosion of the ulnar styloid is classic) and the MTP joints of the feet; late deformities include ulnar deviation, swan neck and boutonniere. In the hip it causes axial migration and protrusio acetabuli; in the knee, uniform loss across all compartments.

The cervical spine is the high stakes area. Pannus at C1 to C2 weakens the transverse ligament and erodes the dens, producing atlantoaxial instability (ADI over 3 mm in an adult), cranial settling (basilar invagination, the dens migrating up toward the foramen magnum) and subaxial stair step subluxations. Neutral and flexion lateral films (taken carefully) are standard before any treatment of the neck in a patient with RA; instability or myelopathic signs (hand clumsiness, gait change, hyperreflexia) are an absolute contraindication to cervical manipulation and a reason for referral.

Ankylosing spondylitis and the seronegatives

The seronegative spondyloarthropathies (ankylosing spondylitis, psoriatic arthritis, reactive arthritis and enteropathic arthritis with inflammatory bowel disease) share HLA B27 association, sacroiliitis, enthesitis and new bone formation. Ankylosing spondylitis begins in young adults, more often men, with inflammatory back pain (morning stiffness over 30 minutes, better with exercise). It starts in the sacroiliac joints, bilaterally and symmetrically: erosions on the iliac side make the joint look wide and irregular (pseudowidening), then sclerosis and finally fusion. In the spine, inflammation at the annulus attachment gives Romanus lesions (shiny corners), then squaring of the vertebral bodies, then thin marginal syndesmophytes that bridge the discs to create the bamboo spine. Ossified interspinous and supraspinous ligaments give the dagger sign, and with fused facets the trolley track sign. The hips are often involved, bilaterally and concentrically.

Psoriatic arthritis is asymmetric and favors the DIP joints, with erosions that create the pencil in cup deformity, fluffy periostitis, acro osteolysis and the sausage digit; its SI involvement is often asymmetric and its spinal bone is bulky, nonmarginal and asymmetric (parasyndesmophytes). Reactive arthritis looks similar but favors the feet and heels. Enteropathic arthritis mimics AS.

Gout and CPPD

Gout (monosodium urate, negatively birefringent needle shaped crystals) is a disease of middle aged men and postmenopausal women; film changes appear only after years of attacks. Look for punched out erosions with sclerotic, overhanging edges (the Martel or rat bite sign), often slightly away from the joint, preserved joint space until late, normal bone density and asymmetric tophi (soft tissue masses that may calcify). The first MTP (podagra) is classic; the elbow (olecranon bursa), hands and knees follow.

Calcium pyrophosphate deposition (positively birefringent rhomboid crystals) has two film faces. Chondrocalcinosis is calcification in cartilage: the knee menisci, the triangular fibrocartilage of the wrist and the pubic symphysis. Pyrophosphate arthropathy looks like osteoarthritis in unusual places: the radiocarpal joint, the second and third MCP joints (with hook like osteophytes), and isolated patellofemoral disease. Calcification around the dens (crowned dens) can cause acute neck pain with fever that mimics meningitis. Hemochromatosis gives an almost identical picture.

Section 2Congenital anomalies and scoliosis on film

Why anomalies matter in a station

Congenital anomalies arise from failures of segmentation (somites do not separate), formation (part of a vertebra never develops) or fusion (ossification centers do not unite). Most are incidental, but the examiner wants three things from you: do not call them fractures or disease, know which ones change mechanics or stability, and know which ones alter your technique.

Scoliosis on film

Scoliosis is a lateral curvature of the spine of 10 degrees or more measured by the Cobb method, usually with vertebral rotation. Most cases in adolescents are idiopathic, typically a right thoracic curve in a girl. Features that suggest an underlying cause and call for MRI include a left thoracic curve, a painful curve (consider osteoid osteoma, with the lesion on the concave side), rapid progression, a curve in a young child, and neurologic signs or cutaneous markers (hair patch, dimple). Functional (nonstructural) curves from leg length inequality or muscle spasm straighten on side bending or when the leg length is corrected; structural curves do not.

Measuring and managing the curve

The Risser sign grades ossification of the iliac crest apophysis, which spreads from the anterior superior iliac spine toward the posterior superior iliac spine: grade 0 none, 1 up to 25%, 2 up to 50%, 3 up to 75%, 4 complete but not fused, 5 fused to the ilium. Low Risser grades mean growth remains and the curve is more likely to progress. Commonly taught thresholds in a growing adolescent: under about 20 to 25 degrees, observe with periodic films (typically every 4 to 6 months); about 25 to 40 degrees in a skeletally immature patient (Risser 0 to 2), refer for bracing; over about 40 to 50 degrees, refer for surgical consultation. Curves over about 50 degrees may keep progressing in adulthood. Chiropractic care can be part of management, but it does not replace indicated bracing or surgical referral, and serial imaging should use PA projections and the lowest dose that answers the question.

Measurement error for the Cobb angle is about 3 to 5 degrees, so a change of 5 degrees or more between films is the usual definition of progression. Measure from the same end vertebrae on each film.

Section 3Tumors and tumor like lesions on film

Aggressive or nonaggressive: the first judgment

You do not need to name every bone tumor in a station, but you must decide whether a lesion looks aggressive or nonaggressive, because that decision sets the recommendation. Combine the patient's age (over 40, metastasis and myeloma dominate; under 30, primary tumors and benign lesions) with five film features.

Matrix narrows the differential: cloud like or ivory density suggests osteoid (osteosarcoma, osteoblastic metastasis); rings and arcs or popcorn stippling suggest cartilage (enchondroma, chondrosarcoma); hazy ground glass suggests fibrous dysplasia. Remember that plain films show a lytic lesion only after roughly 30 to 50% of the bone is gone, so a normal film does not exclude tumor in a patient with red flags; MRI is the sensitive test for marrow disease.

Metastasis and myeloma

Metastasis is the most common malignant tumor of bone and goes where red marrow is: spine, pelvis, ribs, skull and proximal long bones. Most metastases are lytic (lung, kidney, thyroid, breast, gastrointestinal); blastic lesions point to prostate cancer in men and breast cancer in women (mixed lesions are common in breast). In the spine, the plain film hallmark is the missing pedicle on the AP (the winking owl or one eyed pedicle sign), because tumor that starts in the posterior body destroys the cortical pedicle ring. A single dense vertebra, the ivory vertebra, has a short differential: blastic metastasis, Hodgkin lymphoma and Paget disease (Paget enlarges the bone; the others do not). Metastasis typically spares the disc. Recommendation: no manipulation of the involved region, MRI, laboratory tests and urgent referral; screen every patient for spinal cord compression (band like pain, leg weakness, sensory level, bladder change), which is an emergency.

Multiple myeloma is the most common primary malignant tumor of bone, in adults over about 40 to 50. Films show punched out lytic lesions without sclerotic margins (the raindrop skull), or simply diffuse osteopenia with compression fractures. The pedicles tend to be spared early, because they contain little red marrow, which helps separate myeloma from metastasis. Myeloma is often cold on bone scan (there is little osteoblastic response), so a skeletal survey, low dose CT or MRI is used. Laboratory clues follow CRAB: hyperCalcemia, Renal failure, Anemia and Bone lesions, with an M protein on serum protein electrophoresis. A single lesion is a plasmacytoma.

Benign lesions you must recognize

Primary malignancies

Osteosarcoma peaks in adolescence (with a second peak in older adults with Paget disease or prior radiation), in the metaphysis around the knee; it shows mixed destruction with cloud like osteoid, a sunburst periosteal reaction, a Codman triangle and a soft tissue mass. Ewing sarcoma affects children and young adults (about 5 to 20 years), often in the diaphysis of long bones or in flat bones (pelvis), with a permeative pattern, laminated onion skin periosteal reaction and a large soft tissue mass; fever and a raised ESR mimic infection. Chondrosarcoma affects adults (40 to 60) in the pelvis, proximal femur and shoulder girdle, with rings and arcs and deep endosteal scalloping. Chordoma arises from notochord remnants in the sacrum and clivus of older adults as a midline destructive mass. Any of these is an urgent referral to an orthopedic oncologist, with no manipulation of the region.

Section 4Infection, hematologic, metabolic and endocrine disease on film

Discitis and vertebral osteomyelitis

Spinal infection usually reaches the spine through the blood and settles first in the vascular endplate, then spreads into the disc, which in turn destroys the endplate on the other side. That sequence explains the defining film rule: infection crosses and destroys the disc; tumor usually spares it. Pyogenic discitis (most often Staphylococcus aureus; consider gram negatives in intravenous drug users and after urinary procedures) is most common in the lumbar spine of older adults, diabetics, the immunocompromised and patients after spinal procedures. The earliest film sign is disc space narrowing, followed by loss of the sharp white endplate line and erosion of both endplates, then destruction of the bodies and, with healing, sclerosis and fusion. Films lag the disease by about 2 to 3 weeks; MRI is the test of choice early, with ESR and CRP (almost always raised), CBC and blood cultures.

Tuberculous spondylitis (Pott disease) is slower, favors the thoracolumbar spine, spreads under the anterior longitudinal ligament to several contiguous levels, preserves the disc longer, produces large paraspinal and psoas abscesses (which may calcify) and ends in anterior collapse with a sharp kyphosis (gibbus), usually with little sclerosis.

In long bones of children, hematogenous osteomyelitis settles in the metaphysis; films are normal for about 10 to 14 days, then show permeative lysis and periosteal reaction, and later a sequestrum (dead bone) and involucrum (new bone shell). A Brodie abscess is a subacute lucent metaphyseal lesion with a sclerotic rim. Septic arthritis destroys cartilage on both sides of a joint within days and is an emergency.

Avascular necrosis and sickle cell disease

Avascular necrosis (osteonecrosis) most often affects the femoral head. Risk factors are commonly remembered as ASEPTIC: Alcohol and AIDS, Steroids and sickle cell, Erlenmeyer flask (Gaucher disease), Pancreatitis, Trauma, Idiopathic and infection, Caisson disease and collagen vascular disease (lupus). Films are normal early (MRI shows the double line sign), then show mottled sclerosis and lucency, a subchondral lucent crescent sign (subchondral fracture), flattening and collapse of the head, and finally secondary osteoarthritis. Unlike osteoarthritis, the joint space is preserved until collapse. Named osteonecroses include Legg Calve Perthes (child femoral head), Kienbock (lunate, linked with negative ulnar variance), Preiser (scaphoid), Freiberg (second metatarsal head), Kohler (navicular) and Panner (capitellum). Recommend MRI for early disease, protected weight bearing and orthopedic referral.

Sickle cell disease causes marrow hyperplasia and repeated infarction. Look for H shaped vertebrae (square central endplate depressions from infarction of the central growth plate), serpiginous medullary bone infarcts, AVN of the femoral and humeral heads, dactylitis in infants, and widened medullary cavities. Patients are prone to osteomyelitis, classically with Salmonella.

Metabolic and endocrine bone disease

Section 5Soft tissue findings on spine and chest films

Look outside the bones

The soft tissues are a review area that candidates skip under time pressure, and examiners know it. A lateral lumbar film shows the abdominal aorta and the kidneys; a thoracic or cervical film shows lung apices, pleura and the prevertebral space; an AP lumbar or pelvis film shows the renal outlines, the gallbladder region and the pelvic calcifications. Finish every film by sweeping these areas deliberately and saying that you did: "Soft tissues: no abnormal calcification, aorta not dilated, lung apices clear."

Abdominal aortic aneurysm

An abdominal aortic aneurysm (AAA) is a dilation of the aorta to 3 cm or more (normal is about 2 cm). Most are infrarenal and lie in front of L2 to L4, ending at the bifurcation at about L4. Risk factors are age over 65, male sex, smoking, hypertension, atherosclerosis and family history. On the lateral lumbar film, atherosclerotic calcification often outlines the walls as thin curvilinear lines in front of the vertebral bodies; measure from the outer edge of the anterior wall to the outer edge of the posterior wall. A plain film can suggest an aneurysm but cannot exclude one, because many are not calcified. Confirmation is by ultrasound (or CT).

The recommendation depends on size and symptoms. Any AAA needs confirmation by ultrasound and referral to the patient's physician or a vascular surgeon for surveillance; the commonly taught repair threshold is about 5.5 cm in men (about 5 cm in women) or growth faster than about 0.5 to 1 cm per year. A tender or painful aneurysm is an urgent referral; back, flank or abdominal pain with hypotension, syncope or a pulsatile mass suggests rupture, a 911 emergency. Avoid forceful lumbar manipulation, especially rotational side posture thrusts and deep abdominal pressure, in a patient with a known or suspected aneurysm until it has been evaluated; many clinicians use low force methods only.

Abdominal and pelvic calcifications

Chest findings on spine films

Thoracic and cervical films show part of the lungs. A solitary pulmonary nodule (under 3 cm) or mass (3 cm or more) seen on a spine film needs a dedicated chest film or CT and referral; a smoker, an irregular or spiculated edge, or growth raise concern for cancer. The classic trap is a Pancoast (superior sulcus) tumor: an apical opacity, sometimes with destruction of the first to third ribs, in a smoker with shoulder and arm pain in the C8 to T1 distribution and possibly Horner syndrome (ptosis, miosis, anhidrosis). It mimics a cervical radiculopathy, so always look at the lung apices on cervical and upper thoracic films.

A pneumothorax shows a thin white visceral pleural line with no lung markings beyond it; on a supine film, air collects anteriorly and inferiorly and deepens the costophrenic angle (deep sulcus sign). Spontaneous pneumothorax typically occurs in tall, thin young men and in smokers or people with emphysema; it can also follow rib fracture. A tension pneumothorax (mediastinal shift away from the affected side, flattened diaphragm, worsening breathlessness and falling blood pressure) is a 911 emergency. A pleural effusion blunts the costophrenic angle with a curved meniscus. Rib lesions (lytic metastasis, healing fractures) are also part of the chest sweep.

Prevertebral swelling and neck calcifications

On the lateral cervical film, widened prevertebral soft tissue (more than about 7 mm at C2 or 22 mm at C6 in an adult) has three main causes: hematoma from trauma (Chapter 3), retropharyngeal abscess (usually a child or an adult after pharyngeal infection, with fever, painful swallowing, drooling and neck stiffness; sometimes gas in the soft tissue; an emergency because of airway risk) and acute calcific tendinitis of the longus colli (amorphous calcification in front of C1 to C2 with swelling below it, acute neck pain and painful swallowing, self limiting with NSAIDs, but it must be separated from abscess). Other neck calcifications: carotid artery calcification near C3 to C4 (atherosclerosis; recommend carotid ultrasound and physician follow up, and use caution with cervical manipulation), calcified stylohyoid ligament (Eagle syndrome), nuchal ligament ossicles and calcified thyroid or tracheal cartilage (normal with age).

Words worth knowing