Ultrasound evaluation of intraluminal magnets in an ex vivo model.

PURPOSE: The management of foreign body ingestion proves to be a challenge. Magnets pose a unique set of risks when ingested due to their attractive forces and subsequent risk of adherence, pressure necrosis, and perforation complications. Radiographs only provide a limited snapshot in the setting of multiple magnet ingestion when the risk of complication is highest. We hypothesize that abdominal ultrasound (US) has the potential to supplement radiographs in assessing ingested magnets by determining the presence of bowel loop entrapment and of any extraluminal fluid. METHODS: We recreated various scenarios of magnet configurations using animal cadaveric bowel models. X-ray and US images were obtained in various bowel-magnet orientations. RESULTS: We identified several key US features to suggest bowel wall tethering. These include direct visualization of bowel wall entrapment between magnets (what we term the "dangerous V sign"), anti-dependent positions of the magnets, and inability to separate loops of bowel with compression. CONCLUSION: These findings could potentially provide valuable information when directing the urgency of intervention in foreign body ingestion. Ultrasound may supplement and improve the current guidelines in management of magnet ingestion.

Incidental finding of lung hernia in a patient with a remote history of empyema status post video-assisted thoracoscopic surgery.

Lung hernia, the protrusion of pulmonary tissue outside of the thoracic cage, is a rare radiologic finding. The exact incidence of this condition is not well documented. The etiology is either secondary to underlying congenital conditions which weaken the supporting structures of the thoracic wall or more commonly, post-surgical changes. In this report, we describe the case of a 58-year-old male trauma patient who was involved in a motor vehicle collision. Computed tomography of the head, neck, body, and upper extremities was negative for acute injury, but an incidental left-sided herniation of the lingula between the fifth and sixth intercostal spaces was identified. Computed tomography is superior for identifying imaging lung herniations as chest radiographs may not visualize the defect. Upon further investigation, the patient had a remote history of pneumonia complicated by empyema treated by video-assisted thoracoscopic surgery (VATS). This history, coupled with the absence of traumatic injury to the thorax as well as the presence of pulmonary scarring suggests that the lung herniation was likely chronic and secondary to the VATS procedure. The patient was discharged home without surgical intervention. Asymptomatic lung herniations are typically managed conservatively, but patients and physicians should be aware of the risk of lung hernia after VATS as well as associated complications including strangulation or pulmonary infarct.

Mechanical Effects of Lag Screw Retightening in a Simulated Hindfoot Arthrodesis Model.

BACKGROUND: Nonunion following hindfoot arthrodesis may be caused by failure to maintain compression at the arthrodesis site. The ability of lag screws, commonly used in arthrodesis, to maintain compression in hindfoot bones has not been well characterized. The aim of this work was to quantify the stress relaxation response of hindfoot bone with initial and repeated compression with a lag screw. METHODS: Ten sets of 25-mm-diameter bone cylinders were cut from the talus and calcaneus in fresh-thawed cadaveric feet. A load cell was compressed between cylinders with an 8.0-mm partially threaded cannulated lag screw simulating arthrodesis. For 7 sets, screws were tightened by 3 quarter-turns, rested for 3 minutes, retightened 1 quarter-turn, and rested for 30 minutes. Three sets served as controls in which screws were not retightened. RESULTS: Maximum compression after initial screw tightening and retightening averaged 275 and 337 N (P = .07), respectively. Compression 3 minutes after initial screw tightening and retightening averaged 199 and 278 N (P = .027), respectively. The compression recorded 3 minutes after screw retightening was an average of 40% higher than that recorded 3 minutes after initial tightening. The average compression 30 minutes after screw retightening was 255 N, a compression loss of 25% from the average maximum compression after retightening. Eighty percent of this compression loss happened in an average of 5.5 minutes. CONCLUSION: Hindfoot bones exhibit compression loss over time during simulated arthrodesis. Compression maintenance in bone is improved with screw retightening. Further work is needed to understand the mechanism of action and determine optimum time for recompression. CLINICAL RELEVANCE: Retightening lag screws before wound closure may improve compression at the arthrodesis site and thereby decrease the chance of nonunion. LEVEL OF EVIDENCE: N/A, laboratory experiment.