The direct muscular origin of the semitendinosus: a pitfall in categorization of proximal hamstring tendon tears.

The ischial origin of the hamstring musculature is complex. While the conjoint tendon and semimembranosus are commonly discussed and understood by radiologists, there is a lesser-known origin of the semitendinosus along the inferior and medial surface of the ischium in the form of a broad direct muscular connection. This secondary origin is infrequently described in the radiology literature and is a potential pitfall during grading of semitendinosus injuries if the interpreting physician is unaware of its presence. In a proximal hamstring tendon tear, the direct muscular origin of the semitendinosus can be spared, torn along with the conjoint tendon, or remain intact and contribute to a vertical shearing injury of the semitendinosus myotendinous junction. Detailed knowledge of this anatomy and its imaging appearance in the setting of injury enables the reader to correctly diagnose these unique hamstring injuries.

Magnetic resonance imaging does not reliably detect Kaplan fiber injury in the setting of anterior cruciate ligament tear.

PURPOSE: There has been a continued effort to better understand the role Kaplan fiber injury plays in persistent instability following ACL tears. However, the prevalence of these injuries remains poorly understood. Therefore, the purpose of this study was to define the prevalence of Kaplan fiber injury in the setting of complete anterior cruciate ligament tear using a commonly used grading system for assessing ligament injuries. The inter-rater reliability of this commonly used grading system and the relationship between Kaplan fiber injury and injury to other structures commonly found in conjunction with ACL tears was also evaluated. METHODS: All isolated, complete anterior cruciate ligament tears confirmed on magnetic resonance imaging within 90 days of injury between 2014 and 2020 at a single institution were included for analysis. Each scan was read by two, fellowship-trained musculoskeletal radiologists. Kaplan fiber injury was evaluated using a previously described grading scheme. Kappa, [Formula: see text], of inter-rater agreement was determined for all magnetic resonance image scans. Kruskal Wallis test was performed to assess for associations between Kaplan fiber injury and magnet strength (1.5 T vs. 3.0 T), patient gender, the presence of medial and/or lateral meniscal tears, and/or posterolateral tibial bone bruise. RESULTS: Between 2014 and 2020, 131 patients (94 males, 37 females) with a complete anterior cruciate ligament tear were included in the final analysis. The mean age of the cohort was 27.8 ± 6.8 years. Kaplan fiber injuries were identified in 51 of 131 (38.9%, CI 31.0-47.5%) scans with complete anterior cruciate ligament injuries (Grade 1: 28, Grade 2: 18, and Grade 3: 5). Inter-rater agreement for Kaplan fiber injury was fair ([Formula: see text] with 43 (32.8%) scans requiring third reviewer adjudication. There were no significant associations between Kaplan fiber injury and gender, magnet strength, meniscal tears, or posterolateral tibial bone bruise. CONCLUSION: The prevalence of Kaplan fiber injuries was comparable to previously described rates; however, the classification system used to report Kaplan fiber injury was associated with low inter-rater reliability. The presence of Kaplan fiber injury was not associated with other injuries commonly observed in conjunction with ACL tear. The previously proposed Kaplan fiber injury classification system is not reproducible nor is it likely to aid surgeons in distinguishing higher grades of rotatory knee instability. LEVEL OF EVIDENCE: Level IV.

Spontaneus Suburothelial Hemorrhage Associated With Forniceal Rupture and Retroperitoneal Hemorrhage.

Spontaneous suburothelial hemorrhage is a rare process of unclear pathologic etiology, although it has been associated with bleeding diathesis and anticoagulation. The most common clinical presentation is acute onset flank pain and macroscopic hematuria. On imaging, there is a mural thickening of the renal pelvis and upper ureters leading to luminal narrowing. Despite luminal narrowing, hydronephrosis has only rarely been reported in the association. The imaging finding of mural thickening has led to the misdiagnosis as malignancy, resulting in unnecessary nephrectomy. Suburothelial hemorrhage can be unilateral or bilateral, although the majority of reported cases are unilateral. We present a case of a patient with bilateral spontaneous suburothelial hemorrhage with forniceal rupture and spontaneous retroperitoneal hemorrhage, a unique triad compared to prior cases presented in the literature.

MRI Does Not Reliably Detect Kaplan Fiber Injury In Skeletally Immature Patients with an Acute ACL Tear.

Background: To our knowledge, there have been no previous efforts to evaluate the prevalence of Kaplan fiber (KF) injury in skeletally immature patients with an acute anterior cruciate ligament (ACL) tear on magnetic resonance imaging (MRI) nor has there been any comparison of the reliability of previously described KF diagnostic criteria in this cohort. Purpose: To define the prevalence of KF injury in the setting of acute ACL tears using MRI performed within 90 days of injury among skeletally immature patients, and to compare the reliability of MRI in detecting KF injuries using 2 previously described diagnostic criteria. Study Design: Cohort study; Level of evidence, 3. Methods: Skeletally immature patients with an acute ACL tear confirmed using MRI within 90 days of injury were assessed. Two fellowship-trained musculoskeletal radiologists independently interpreted each MRI scan twice. KF injury was first assessed using the Van Dyck scheme (grade 0, normal; grade 1, periligamentous; grade 2, partial tear; and grade 3, complete tear). MRI scans were then reviewed again using the KF injury criteria proposed by Batty. Discrepancies in KF injury schemes were adjudicated by a third musculoskeletal radiologist. Interrater agreement for both methods was determined using Cohen κ. Results: Included were 45 patients (33 male, 12 female) with a mean age of 13.2 ± 1.6 years. KF injuries were identified in 17 of 45 (37.7%) knees of using the traditional Van Dyck grading scheme (interrater agreement κ = 0.40). The Batty diagnostic criteria identified KF injury in 5 of 45 (11.1%) (interrater agreement κ = 0.45); 17 (37.8%) MRI scans required a third reviewer adjudication for the Van Dyck scheme, while 4 (8.9%) required a third reviewer using the Batty criteria. Conclusion: The Batty diagnostic criteria detected a lower KF injury prevalence than previously reported in the adult population, while the Van Dyck prevalence was similar to rates in adult populations. Both grading criteria had poor interrater reliability in diagnosing a KF injury.

Slipped Capital Femoral Epiphysis as a Presentation of Underlying Metabolic Disorders: Pseudohypoparathyroidism and Juvenile Hypothyroidism.

Slipped capital femoral epiphysis (SCFE) is an abnormality of the proximal femoral physis typically occurring in adolescents and most commonly associated with obesity, although its exact etiology is unknown. In addition to obesity, other associations and predisposing factors proposed in the literature include trauma, vascular injury or compromise, and immunologic, genetic, and metabolic conditions. While not common, metabolic conditions are known to predispose to SCFE and it is essential for radiologists to recognize SCFE as a possible initial presentation of an underlying metabolic disorder. Understanding imaging findings and identification of atypical presentations of SCFE by radiologists can assist clinicians in guiding workup and lead to expedited treatment to prevent worsening outcomes associated with developmental delay.

Challenges in the Interpretation of MRI Examinations Without Radiographic Correlation: Pearls and Pitfalls to Avoid.

As physics introduces more complex and seemingly thorough techniques to evaluate patient symptoms, cross-sectional imaging, especially magnetic resonance imaging (MRI), seems like the modality of choice to best help patients. However, musculoskeletal radiology (MSK) requires not just the excellent soft-tissue contrast provided by MRI but also an evaluation of the aggressiveness of a lesion, a detailed evaluation of osseous anatomy or distribution of disease, and a way to easily identify calcifications and gas in soft tissue in order to make the correct diagnosis. This article will demonstrate, through numerous cases, the importance of radiographs in the full characterization of MSK-related pathology. It will focus on imaging pearls and pitfalls to avoid when radiographs are not available and discuss the findings that can be expected if comparison radiographs were available.

Ligand-induced changes in the structure and dynamics of Escherichia coli peptide deformylase.

Peptide deformylase (PDF) is an enzyme that is responsible for removing the formyl group from nascently synthesized polypeptides in bacteria, attracting much attention as a potential target for novel antibacterial agents. Efforts to develop potent inhibitors of the enzyme have progressed on the basis of classical medicinal chemistry, combinatorial chemistry, and structural approaches, yet the validity of PDF as an antibacterial target hangs, in part, on the ability of inhibitors to selectively target this enzyme in favor of structurally related metallohydrolases. We have used (15)N NMR spectroscopy and isothermal titration calorimetry to investigate the high-affinity interaction of EcPDF with actinonin, a naturally occurring potent EcPDF inhibitor. Backbone amide chemical shifts, residual dipolar couplings, hydrogen-deuterium exchange, and (15)N relaxation reveal structural and dynamic effects of ligand binding in the immediate vicinity of the ligand-binding site as well as at remote sites. A comparison of the crystal structures of free and actinonin-bound EcPDF with the solution data suggests that most of the consequences of the ligand binding to the protein are lost or obscured during crystallization. The results of these studies improve our understanding of the thermodynamic global minimum and have important implications for structure-based drug design.

Mapping the surface of Escherichia coli peptide deformylase by NMR with organic solvents.

Identifying potential ligand binding sites on a protein surface is an important first step for targeted structure-based drug discovery. While performing control experiments with Escherichia coli peptide deformylase (PDF), we noted that the organic solvents used to solubilize some ligands perturbed many of the same resonances in PDF as the small molecule inhibitors. To further explore this observation, we recorded (15)N HSQC spectra of E. coli peptide deformylase (PDF) in the presence of trace quantities of several simple organic solvents (acetone, DMSO, ethanol, isopropanol) and identified their sites of interaction from local perturbation of amide chemical shifts. Analysis of the protein surface structure revealed that the ligand-induced shift perturbations map to the active site and one additional surface pocket. The correlation between sites of solvent and inhibitor binding highlights the utility of organic solvents to rapidly and effectively validate and characterize binding sites on proteins prior to designing a drug discovery screen. Further, the solvent-induced perturbations have implications for the use of organic solvents to dissolve candidate ligands in NMR-based screens.

Perirenal hemorrhage as first presentation of Wilms tumor.

Wilms tumor typically presents as an abdominal mass, though occasionally patients present with other manifestations. We report a case of a child presenting with a perirenal hemorrhage and an initially occult Wilms tumor, found only on subsequent renal arteriography. Symptoms in this patient were caused by the presence of perirenal and subcapsular hemorrhage rather than the tumor itself. Despite an unusual presentation, we need to consider underlying neoplasia in children with renal hemorrhage and the absence of a history of trauma. Follow-up studies might help clarify initial negative imaging results.