Yoshimi Endo

Background: “Rice body” describes the gross appearance of hyperplastic synovial villi that develop into rice-like fibrinous loose bodies. Rice bodies have historically been associated with tuberculosis and inflammatory arthritis, but no retrospective studies have correlated their magnetic resonance imaging (MRI) appearances to histology or to the underlying diagnoses. Purpose: We sought to correlate the appearance on MRI of rice body-like particles with histology and describe the associated diagnoses. Methods: We conducted a retrospective cross-sectional study of MRI reports in our institutional imaging database in which a radiologist described “rice bodies.” The search was performed by a keyword search for “rice,” ultimately yielding a total of 100 patients between June 1992 and July 2022. Patients were excluded if their MRI was not available for retrospective review or if there was insufficient follow-up to establish a clear underlying diagnosis. Cases were included if the MRI finding of rice bodies was confirmed by retrospective review of the images and there was clinical follow-up or surgery with histology establishing the underlying diagnosis. Results: Of the 52 patients who met inclusion criteria and were enrolled in our retrospective study, 37% (19/52) had prior surgery, 73% (14/19) being arthroplasty. Diagnoses associated with rice body-like particles on MRI were inflammatory arthritis (52%; 27/52), infection (25%; 13/52), synovial chondromatosis (8%; 4/52), osteoarthritis (6%; 3/52), bursitis (6%; 3/52), and adverse local tissue reaction (4%; 2/52). Among 13 infections, only 1 was mycobacterial while 46% (6/13) were staphylococcal and 31% (4/13) were culture-negative. In the presence of arthroplasty, rice body-like particles were associated with infection in 71% (10/14), followed by adverse local tissue reaction (14%; 2/14), 46% (24/52) underwent surgery after MRI, and 45% (10/22) had rice bodies confirmed on histology. Conclusion: Our retrospective findings suggest that rice body-like synovial particles on MRI are not specific to tuberculosis and inflammatory arthritis. Other diagnoses may also be considered, particularly nonmycobacterial infection when there is an arthroplasty. Level of Evidence: Level IV: retrospective cross-sectional study.

Objective Describe features of iatrogenic “overshoot” nerve injuries on ultrasound and MRI, which occur when an instrument passes through the bone and injures the nerve after it penetrates the opposite cortex. Materials and methods After a keyword search of the radiology database at a tertiary care orthopedic hospital from January 2016 to December 2022, those fulfilling the inclusion criteria of (1) instrumentation through the bone during surgery, (2) acute neuropathy immediately after surgery, (3) nerve injury confirmed on electrodiagnostics, and (4) imaging consistent with overshoot nerve injury were included. Imaging studies were retrospectively evaluated to determine primary and secondary signs of an overshoot nerve injury. Results Six patients (3 females, mean age 26.7 (range 10–49) years) had nerve injury fitting the mechanism of injury: 3 injuries to the radial nerve during fixation of distal humerus fractures, 1 tibial nerve and 1 superficial peroneal nerve injury during fixation of tibial fractures, and 1 posterior interosseous nerve injury during biceps tendon repair. Ultrasounds were performed in all while 4 also had MRI. Secondary signs included (1) cortical defect adjacent to injured nerve (n=2); (2) scar extending from bone to injured nerve (n=2); (3) screw tip pointing to injured nerve (n=1, 4) tract in bone on MRI from previous instrumentation pointing to injured nerve (n=2). Conclusion In addition to primary signs such as laceration or neuroma, secondary signs of “overshoot” nerve injury include cortical defect, scar extending to nerve, screw tip pointing to nerve, and linear tract in the bone on MRI.

Objective In this technical report, we describe our protocol for the dynamic sonographic evaluation of the hip and assess reliability of the ultrasound assessment of hip microinstability. Materials and methods Our clinical experience with a standardized dynamic ultrasound of the hip performed in a series of 27 patients with imaging performed by an experienced musculoskeletal radiologist during physical examination by an orthopedic surgeon specializing in hip preservation is illustrated with clinical photographs and ultrasound images from volunteers and selected patients. Interrater reliability for the diagnosis of microinstability was calculated. Results Dynamic ultrasound technique and findings of hip instability, femoroacetabular impingement, and ischiofemoral impingement with corresponding clinical photos showing the necessary physical examination maneuvers are described. Interrater agreement for the diagnosis of microinstability was substantial (κ 0.606 [0.221–0.991]). Conclusion At our institution, dynamic ultrasound of the hip during physical examination complements information gathered from static imaging by providing real-time correlation of symptoms with what is occurring anatomically.

MRI demonstrated substantial to excellent interreader reproducibility and had a higher sensitivity and slightly lower specificity than did radiography in diagnosing loosening of the patellar compon... Background Because loosening of total knee arthroplasty (TKA) occurs due to poor osseous integration at component-bone interfaces, interface assessment may be helpful in diagnosing loosening at MRI...

Objective Describe tendon injuries and their structural causes seen on ultrasound in wrists with distal radius fractures and estimate the accuracy of ultrasound and its impact on clinical management. Materials and methods Ultrasounds of 226 wrists (221 patients) with distal radius fractures were retrospectively reviewed. Ultrasound findings of tendon injuries and their structural causes were correlated with surgery and clinical outcome. Accuracy and inter- and intra-observer reproducibilities were calculated. Results Twenty-five wrists were treated non-operatively while 201 underwent surgery. Ultrasound demonstrated hardware contact with flexor pollicis longus (FPL) in 76 wrists, extensor pollicis longus (EPL) in 21, and other tendons in 94. Ultrasound identified tendon ruptures in 23 wrists (13 EPL/8 FPL/2 extensor indicis proprius (EIP)), most of which were surgically confirmed. Among 12 wrists with confirmed EPL ruptures, distal radius fracture had been treated with volar plating in 6 and non-operatively in 6, and ultrasound showed osseous irregularity at the rupture site in 8. All FPL ruptures occurred in wrists with volar plating. Ultrasound findings were concordant with subsequent clinical management in most. In 2, ultrasound findings led to the decision to remove hardware despite lack of symptoms. Ultrasound had sensitivity/specificity/accuracy of 88/99/98% for identifying a specific tendon as ruptured and 88/87/88% for tendon abnormalities in general. Inter- and intra-observer reproducibilities were excellent (kappa = 0.85 ~ 1.0). Conclusion Certain wrist tendons, particularly EPL and FPL, are vulnerable after distal radius fractures. Ultrasound is accurate and useful for detecting tendon injury and sources of tendon irritation and can guide clinical management.