Abstract
BackgroundC-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been shown to be useful for diagnosis of prosthetic hip and knee infection. Little information is available on CRP and ESR in patients undergoing revision or resection of shoulder arthroplasties or spine implants.Methods/ResultsWe analyzed preoperative CRP and ESR in 636 subjects who underwent knee (n = 297), hip (n = 221) or shoulder (n = 64) arthroplasty, or spine implant (n = 54) removal. A standardized definition of orthopedic implant-associated infection was applied. Receiver operating curve analysis was used to determine ideal cutoff values for differentiating infected from non-infected cases. ESR was significantly different in subjects with aseptic failure infection of knee (median 11 and 53.5 mm/h, respectively, p = <0.0001) and hip (median 11 and 30 mm/h, respectively, p = <0.0001) arthroplasties and spine implants (median 10 and 48.5 mm/h, respectively, p = 0.0033), but not shoulder arthroplasties (median 10 and 9 mm/h, respectively, p = 0.9883). Optimized ESR cutoffs for knee, hip and shoulder arthroplasties and spine implants were 19, 13, 26, and 45 mm/h, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 89 and 74% for knee, 82 and 60% for hip, and 32 and 93% for shoulder arthroplasties, and 57 and 90% for spine implants. CRP was significantly different in subjects with aseptic failure and infection of knee (median 4 and 51 mg/l, respectively, p<0.0001), hip (median 3 and 18 mg/l, respectively, p<0.0001), and shoulder (median 3 and 10 mg/l, respectively, p = 0.01) arthroplasties, and spine implants (median 3 and 20 mg/l, respectively, p = 0.0011). Optimized CRP cutoffs for knee, hip, and shoulder arthroplasties, and spine implants were 14.5, 10.3, 7, and 4.6 mg/l, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 79 and 88% for knee, 74 and 79% for hip, and 63 and 73% for shoulder arthroplasties, and 79 and 68% for spine implants.ConclusionCRP and ESR have poor sensitivity for the diagnosis of shoulder implant infection. A CRP of 4.6 mg/l had a sensitivity of 79 and a specificity of 68% to detect infection of spine implants.
Highlights
C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) are inexpensive, non-invasive tests that are often obtained in subjects with orthopedic implants prior to implant removal to assess for implant-associated infection
There is little data available on the performance of CRP and ESR in the diagnosis of spine implant-associated infection, Hahn et al reported that normal CRP and ESR do not rule out late infection associated with spinal instrumentation [3]
CRP was significantly different in subjects with aseptic failure and infection of knee, hip, and shoulder arthroplasties, and spine implants
Summary
C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) are inexpensive, non-invasive tests that are often obtained in subjects with orthopedic implants prior to implant removal to assess for implant-associated infection. CRP and, to a lesser extent, ESR, have been shown to be useful in the diagnosis of prosthetic hip and knee infection, especially if validated cut-off values are applied (Table 1). ESR and CRP have poor sensitivity to detect prosthetic shoulder infection when cutoffs of 30 mm/h or 10 mg/l, respectively, are applied [1]. This may relate to the frequent implication of the low virulence organism, Propionibacterium acnes, in shoulder arthroplasty infection [1,2], or to failure to use optimized cutoff values for shoulder arthroplasty infection. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been shown to be useful for diagnosis of prosthetic hip and knee infection. Little information is available on CRP and ESR in patients undergoing revision or resection of shoulder arthroplasties or spine implants
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