MedicalContinuing Education PODIATRIC RADIOGRAPHY Objectives After completing this mate- rial the reader shall be able to: 1) List the radiographic criteria for systematically evaluating joints and joint disease. 2) Define: joint effusion, AA SystematicSystematic arthritis mutilans, and en- thesopathy. 3) List common joint dis- ApproachApproach toto orders that are associated with arthritis. 4) Explain the importance DifferentiatingDifferentiating of a lesion (erosion, for exam- ple) having either a well- defined or ill-defined margin. JointJoint DisordersDisorders 5) List target areas in the foot and calcaneus for com- X-rays can be an important mon arthritic disorders. 6) Distinguish between tool in confirming your the joint disorders (based diagnosis. on radiographic findings). Welcome to Podiatry Management’s CME Instructional program. Our journal has been approved as a sponsor of Contin- uing Medical Education by the Council on Podiatric Medical Education. You may enroll: 1) on a per issue basis (at $17.50 per topic) or 2) per year, for the special introductory rate of $109 (you save $66). You may submit the answer sheet, along with the other information requested, via mail, fax, or phone. In the near future, you may be able to submit via the Internet. If you correctly answer seventy (70%) of the questions correctly, you will receive a certificate attesting to your earned cred- its. You will also receive a record of any incorrectly answered questions. If you score less than 70%, you can retake the test at no additional cost. A list of states currently honoring CPME approved credits is listed on pg. 246. Other than those entities cur- rently accepting CPME-approved credit, Podiatry Management cannot guarantee that these CME credits will be acceptable by any state licensing agency, hospital, managed care organization or other entity. PM will, however, use its best efforts to ensure the widest acceptance of this program possible. This instructional CME program is designed to supplement, NOT replace, existing CME seminars. The goal of this program is to advance the knowledge of practicing podiatrists. We will endeavor to publish high quality manuscripts by noted authors and researchers. If you have any questions or comments about this program, you can write or call us at: Podiatry Management, P.O. Box 490, East Islip, NY 11730, (631) 563-1604 or e-mail us at [email protected]. An answer sheet and full set of instructions are provided on pages 246-248.—Editor By Robert A. Christman, D.P.M. out question, osteoarthritis is the not unusual for the inflammatory most common, primarily because rheumatic diseases (rheumatoid everal arthritides (types of of the mechanical wear and tear arthritis, psoriatic arthritis, anky- arthritis) have a predilection that weight-bearing activities losing spondylitis, and Reiter’s Sfor the foot (Table 1). With- place on cartilage. However, it is Continued on page 186 www.podiatrym.com APRIL/MAY 2004 • PODIATRY MANAGEMENT 185 Joint Disorders... The archetypal radiographic consider the probable differential presentations of joint disorders diagnoses. Continuingsyndrome) to first appear or that have been described in the be diagnosed in the feet. Fur- literature are not necessarily what Systematic Approach to Medical Education thermore, gouty arthritis and dia- the clinician encounters in every- Differentiating Joint Disorders betic neuropathic osteoarthropa- day practice. The classic picture is A detailed, systematic ap- thy target have a predilection for typically the patient who was di- proach for evaluating pedal joints the foot. agnosed with the joint disease entails three considerations2 many years or even decades ago. In contrast, the patient with acute symptomatology may ini- TABLE 1 tially come for help at the onset of disease or soon thereafter. In To maximize the Joint Disorders such a case, the radiographic detection of early findings are frequently subtle and Affecting nonspecific, the clinical findings arthritis, you “must the Foot are vague, and the diagnosis is know how to look, often elusive. Furthermore, atypi- where to look, and what Osteoarthritis cal cases are common. The chal- lenge, therefore, is to identify the Rheumatoid arthritis to look for.” subtle, early radiographic find- Psoriatic arthritis ings, because the classic features Reiter’s syndrome of a particular joint disorder do Ankylosing spondylitis not manifest until many years later. To maximize the detection (Table 2). For obvious reasons, the Gouty arthritis of early arthritis, you “must know symptomatic joint or joints are as- Neuropathic osteoarthropathy how to look, where to look, and sessed first. The asymptomatic Septic arthritis what to look for.”1 Then, along joints of both extremities should with the clinical and other labo- also be evaluated, for two reasons: ratory findings, you must list and Most joint disorders target both extremities, and joints may be af- fected that are clinically asymp- tomatic. (Joint disease is one of TABLE 2 the few conditions that warrants performing a bilateral radiograph- A Systematic Approach to Evaluating ic study.) The examination does- n’t stop here, however. Sites dis- Joint Disease tant from involved joints, osseous and soft tissue are also considered. Roentgen features at or adjacent to involved joints Abnormal findings at the cal- Primary findings caneal entheses and heel pain, for Osseous erosion example, can be associated with New bone formation joint disease. Finally, the distribu- Joint space alteration tion of radiographic findings must 3 Secondary findings be assessed for specific patterns. Many articular disorders demon- Soft tissue edema strate characteristic patterns of Calcification joint involvement that help dis- Geographic rarefaction tinguish one disease from another. Alignment abnormalities Articular disorders affecting Roentgen features at sites distant from involved joints the foot may involve one or mul- Erosion tiple joints. Monoarticular joint Enthesopathy disease is generally attributed to either trauma, infection, or acute Soft tissue mass gouty arthritis (Table 3). Less com- Patterns of joint disease according to distribution of roentgen findings mon causes of pedal monoarticu- Joints involved lar disease include rheumatoid Targeted joints monoarthritis and pigmented vil- Bilateral versus unilateral lonodular synovitis. Examples of Symmetry versus asymmetry polyarticular joint disorders affect- Extra-articular sites involved ing the foot include osteoarthritis, rheumatoid arthritis, seronegative Continued on page 187 186 PODIATRY MANAGEMENT • APRIL/MAY 2004 www.podiatrym.com MedicalContinuing Education the atrophic joint disor- ders. A subdivision of this TABLE 3 group is commonly associated with an adjacent soft tissue mass Causes of Joint Disease clinically and the preservation of joint space. Forrester and Brown have used the term “lumpy-bumpy” joint Monoarticular disease to characterize this latter Trauma group..4 Infection Neuropathic osteoarthropathy is Crystal deposition divided into two subtypes: forefoot, Gout and the combined midfoot and tar- CPPD sus. Its radiographic features vary de- Rheumatoid monoarthritis pending on location: Forefoot sites exhibit findings characteristic of at- Pigmented villonodular synovitis rophic joint disease; the midfoot and Polyarticular tarsal sites display features of detritus Osteoarthritis (hypertrophic) arthritis. Rheumatoid arthritis Each of the roentgen features Seronegative arthritis associated with joint disease is dis- cussed individually in the following Chronic tophaceous gout sections. Remember the radio- Neuropathic osteoarthropathy graphic categories of joint disor- Pigmented villonodular synovitis (midfoot) ders; you can recognize associations Multiple reticulohistiocytosis between certain roentgen findings and arthritis categories, improving your diagnostic acumen. arthritis (psoriatic arthritis, anky- ing pathologic processes: losing spondylitis, and Reiter’s syn- degenerative, inflamma- drome), neuropathic osteoarthropa- tory, and metabolic4 thy, and chronic tophaceous gout. (Table 4). This classifica- Differentiation of joint disorders tion, unfortunately, does can be simplified by applying a gener- not include neuropathic al classification system to the present- osteoarthropathy. In ing features. One categorization of 1904, Goldthwaite used arthritis has been based on underly- radiographic criteria to distinguish between os- teoarthritis and rheuma- toid arthritis.5 These crite- TABLE 4 ria can be expanded to include the remaining Categories of forms of pedal arthritis. Joint disorders affect- Joint Disease ing the foot can be divid- (based on underlying ed into two radiographic categories, based on the pathology) predominant radiograph- ic feature: hypertrophic Degenerative and atrophic (Table 5). Osteoarthritis Hypertrophic joint dis- Figure 1. Irregular, ill-defined erosion (ankylosing Inflammatory ease features bone over- spondylitis). Rheumatoid arthritis growth and enlargement. The characteristic findings are sub- Roentgen Features at Involved Seronegative arthritis chondral sclerosis and osteophyte for- Joints: Primary Findings Psoriatic arthritis mation at the margin of a joint. Detri- Reiter’s disease tus arthritis, a subcategory of hyper- Osseous Erosion Ankylosing spondylitis trophic arthritis, includes those disor- Bone erosion is a primary fea- ders that exhibit fragmentation in ad- ture of all joint disorders except Septic arthritis dition to exaggerated hypertrophic