Imaging orthopedic implant infections

Abstract

The diagnosis of infections associated with orthopedic implants is based on a combination of clinical signs, laboratory findings and imaging studies. There is no gold standard imaging technique: conventional radiography is indispensable, although 50% of the time the radiograph is normal. Computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonography are valuable to detect soft tissue abnormalities. Bone scintigraphy (BS) rules out active infection. For infections involving the peripheral skeleton, labeled white blood cell (WBC) scintigraphy coupled with colloid scintigraphy is the reference technique, whereas a gallium scan is always necessary for imaging the spine or pelvis. To confirm or rule out infection, needle aspiration with analysis of aspirated fluid is the cornerstone of the diagnostic algorithm.

Use of PET/CT in the early diagnosis of implant related wound infection and avoidance of wound debridement

“…Common serology studies, such as leukocyte count, ESR and CRP, are non-specific and are not helpful in a definitive diagnosis [10]. For evaluation of suspected late infections, plain radiographs and CT have low sensitivity and specificity in the early stage of infection [11]. These investigations can only detect infections when significant morphological changes occur, such as screw loosening or substantial bone resorption around the screw [11].…”

“…For evaluation of suspected late infections, plain radiographs and CT have low sensitivity and specificity in the early stage of infection [11]. These investigations can only detect infections when significant morphological changes occur, such as screw loosening or substantial bone resorption around the screw [11]. The value of MR in the early diagnosis of late infection after spinal instrumentation remains unclear as its accuracy is impaired by metallic artifacts and postsurgical changes of the bone and soft tissues [15].…”

“…Blood tests, such as white blood cell (WBC) count, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are neither specific or sensitive [10]. Conventional imaging modalities, such as plain radiographs and computed tomography (CT), have limited value for an early diagnosis of late infection when structural changes of bone or soft tissues have yet to occur [11]. Magnetic resonance (MR) imaging may be another choice but its accuracy is substantially influenced by the metallic artifacts [8].…”

Sinogram utilization revisited

“…4 Although it is no longer commonly used, the sinogram can be a very useful tool when evaluating the depth and extent of a sinus tract that questionably involves the bone or joint. While MRI and CT scans are more commonly used to discover osteomyelitis and septic arthritis, a major drawback of those studies is the artifact produced by nearby metal objects, such as orthopaedic implants, which can result in poor image quality.…”

Predictors of Diagnostic Efficacy of Tagged White Blood Cell Scans in the Evaluation of Occult Infection

“…However, the authors did not assess how often the TWBCS added new clinical information or impacted management. 13 We examined clinical cases to determine those cases in which TWBCSs were ordered in cases of occult infection. [7][8][9] Even among those with postoperative FUO, computed tomography scanning is generally felt to be a preferred starting point during the early postoperative period.…”