Safety of Magnetic Resonance Imaging in Orthopaedic Trauma Patients With External Fixation: A Two-Center Case Series.

OBJECTIVES: To report on adverse events during magnetic resonance imaging (MRI) in patients with external fixators. METHODS: . DESIGN: Retrospective case series. SETTING: Two Level 1 trauma centers. PATIENT SELECTION CRITERIA: Patients with external fixators on the appendicular skeleton or pelvis undergoing MRI between January 2005 and September 2023. OUTCOME MEASURES AND COMPARISONS: Adverse events, defined as any undesirable event associated with the external fixator being inside or outside the MRI bore during imaging, including (subjective) heating, displacement or pullout of the external fixator, or early MRI termination for any reason. RESULTS: A total of 97 patients with 110 external fixators underwent at least one MRI scan with an external fixator inside or outside of the MRI bore. The median age was 51 years (interquartile range: 39-63) and 56 (58%) were male. The most common external fixator locations were the ankle (24%), knee (21%), femur (21%), and pelvis (19%). The median duration of the MRI was 40 minutes (interquartile range: 26-58), 86% was performed using 1.5-Tesla MRI, and 14% was performed using 3.0-Tesla MRI. Ninety-five percent of MRI was performed for the cervical spine/head. Two MRI scans (1.6%), one of the shoulder and one of the head and cervical spine, with the external fixator outside of the bore were terminated early because of patient discomfort. There were no documented events of displacement or pullout of the external fixator. CONCLUSIONS: These findings suggest that MRI scans of the (cervical) spine and head can be safely obtained in patients with external fixators on the appendicular skeleton or pelvis. Given the low numbers of MRI scans performed with the external fixator inside the bore, additional studies are necessitated to determine the safety of this procedure. The results from this study can aid orthopaedic surgeons, radiologists, and other stakeholders in developing local institutional guidelines on MRI scanning with external fixators in situ. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Dual energy computed tomography cannot effectively differentiate between calcium pyrophosphate and basic calcium phosphate diseases in the clinical setting.

Background: Recent reports suggested that dual-energy CT (DECT) may help discriminate between different types of calcium phosphate crystals in vivo, which would have important implications for the characterization of crystal deposition occurring in osteoarthritis. Purpose: Our aim was to test the hypothesis that DECT can effectively differentiate basic calcium phosphate (BCP) from calcium pyrophosphate (CPP) deposition diseases. Methods: Discarded tissue after total knee replacement specimens in a 71 year-old patient with knee osteoarthritis and chondrocalcinosis was scanned using DECT at standard clinical parameters. Specimens were then examined on light microscopy which revealed CPP deposition in 4 specimens (medial femoral condyle, lateral tibial plateau and both menisci) without BCP deposition. Regions of interest were placed on post-processed CT images using Rho/Z maps (Syngo.via, Siemens Healthineers, VB10B) in different areas of CPP deposition, trabecular bone BCP (T-BCP) and subchondral bone plate BCP (C-BCP). Results: Dual Energy Index (DEI) of CPP was 0.12 (SD â€‹= â€‹0.02) for reader 1 and 0.09 (SD â€‹= â€‹0.03) for reader 2, The effective atomic number (Zeff) of CPP was 10.83 (SD â€‹= â€‹0.44) for reader 1 and 10.11 (SD â€‹= â€‹0.66) for reader 2. Nearly all DECT parameters of CPP were higher than those of T-BCP, lower than those of C-BCP, and largely overlapping with Aggregate-BCP (aggregate of T-BCP and C-BCP). Conclusion: Differentiation of different types of calcium crystals using DECT is not feasible in a clinical setting.