In 1 study, without mention of whether the radiologist was blinded but using an appropriate post-traumatic control group, sensitivity of 80% and specificity of 80% were reported (LOE: 2, casecontrol design).27 In a cohort of persons with upper extremity pain, also without mention of blinding, sensitivity of 73% and specificity of 86% were reported (LOE: 2, cohort design).25 Using normal controls, not a clinically relevant comparison, sensitivity of 97% and specificity of 86% using bone scans have been reported (LOE: 2, case control design).26
Despite the reasonable sensitivity and specificity of the bone scans in these studies, clinical assessment was used as the gold standard for diagnosis and the bone scans did not add any degree of accuracy to that clinical assessment. Based on these studies, clinicians using a bone scan to rule in or rule out CRPS type 1 instead of using a clinical assessment risk missing up to 27% of cases and over-diagnosing 20% of cases.
Older literature suggested that osteopenia/porosis demonstrated on plain radiography or dual energy x-ray absorptiometry (DEXA) scanning was important for the diagnosis of CRPS type 1, but more recent studies have revealed sensitivity for plain radiography as low as 23% (LOE: 2, exploratory cohort study with good reference standards)13 and for DEXA a sensitivity of 76% (LOE: 2, case-control design).28 No studies were identified that used a control group post-trauma, so an adequate assessment of specificity has not been made.
Applying the evidence in practice
CRPS type 1 is often relegated to specialists. But, in fact, no special equipment or testing is required for the diagnosis of CRPS type 1, and the best treatments appear to be non-invasive and completely within the realm of family medicine.
With more attention to deviations from the normal course of recovery from trauma, the family physician will begin to recognize more cases of CRPS type 1 and can have full confidence that the treatments prescribed and monitored are in fact the treatments of choice.
Preventing CRPS 1
For persons with hemiplegia, and of course early inpatient rehabilitation of post-stroke patients with upper extremity hemiplegia. Give 500 mg of vitamin C daily to post-fracture patients in the hope of preventing CRPS type 1 (SOR: B).
Pathophysiology unclear
Researchers have been unable to identify the underlying pathophysiology for CRPS type 1, perhaps in part because patients with different pathophysiologies may present with similar clinical findings.9 Recent discovery of an HLA linkage suggests that there may be a genetic predisposition to CRPS type 1.40
By definition, in CRPS type 1 no major nerve damage can be detected, but there may be damage to nerve fibers too small to detect on electromyograph. Research suggests that injured peripheral C-fibers and A-delta pain fibers immediately flood the central nervous system (CNS) with neurochemicals via the dorsal root ganglion and central pain projecting neurons of the CNS. The CNS is pathologically altered and sends signals to the injured area that serve to maintain the clinical signs and symptoms of CRPS type 1: peripheral pain and sensory changes, local sympathetic changes in blood vessels and sweat glands, and local motor changes.9 Abnormal sympathetic activity can be clearly demonstrated, but there is no evidence to suggest that this is the cause of CRSP type 1.41
Base evaluation on history and physical exam
More often, the family physician will be in the position of evaluating persistent post-traumatic pain. Given the absence of compelling evidence in the literature, rely on your experience to guide the work up.
To diagnose CRPS type 1, first rule out other diseases (FIGURE).4 The frequency with which other conditions occur in persons at risk for CRPS type 1 is not known because the research concerning CRPS type 1 has been undertaken in specialty care clinics; primary care physicians had already done the work of excluding many other disorders.
Physical diagnosis. The differential diagnosis for limb pain is extensive and includes fracture non-union, tendonitis, diabetic neuropathy,4 osteomyelitis or cellulitis,13 polyneuropathy, radiculopathy,11 phlebothrombosis,13 and Raynaud’s disease.13 Physical exam will reveal signs of infection, focal tenderness consistent with tendonitis, erythema suggestive of cellulitis, a distribution of pain following a nerve suggestive of radiculopathy or carpal tunnel syndrome, or the stocking-glove distribution diabetic neuropathy.
Auxiliary testing. Limited testing may be helpful. Plain radiography or bone scanning may identify a poorly healed fracture or other bony lesions. A white blood cell count and inflammatory markers may identify infection or autoimmune disorders.