Spinal fractures are common following underbody blast. Most injuries occur at the thoracolumbar junction, and fracture patterns suggest the spine is flexed at the moment of injury. However, current mechanistic descriptions of vertebral fractures are based on low energy injuries, and there is no evidence to correlate fracture pattern with posture at the loading rates seen in blast injury. The T12-L1 segment of 4 human spines was dissected to preserve the paraspinal ligaments and potted in polymethylmecrylate. The specimens were impacted with a 14 kg mass at 3.5m/s in a drop tower; two specimens were impacted in neutral posture, one in flexion, and one in extension. A load cell measured the load history. CT scans and dissection identified the injury patterns. Each specimen sustained a burst fracture. The neutral specimens demonstrated superior burst fractures, the flexed specimen demonstrated a superior burst fracture with significant anterior involvement, and the extended specimen showed a posterior vertebral body burst fracture. At high loading rates, the posture of the spine at the moment of injury appears to affect the resulting fracture. This supports understanding the behaviour of the spine in blast injury and will allow improved mitigation system design in the future.
Bone cement reaches high temperatures while polymerising. Bone has been shown to be sensitive to thermal injury with osteonecrosis reported after one minute at 47°C. Necrosis during cementing might compromise the bone-cement interface. Some surgeons fill the joint cavity with irrigation fluid to provide a heatsink during cementing, but this has not been supported by research. We used a model acetabulum in a bovine humerus to allow measurement of bone temperatures in cementing. Models were prepared with a 50mm diameter acetabulum and three temperature probe holes. Four warmed models were cemented with Palacos RG using a standard mixing system and a 10mm UMHWPE disc to represent an acetabular component. Two of the acetabular models were filled with room temperature water to provide a heatsink. An electronic probe measured temperature at 5 second intervals from the moment of cementing. In the models with no heatsink, peak temperature was 40.3°C. The highest temperature rise was 7.5°C. In the models with a heatsink, there was a mean fall of 4.4°C. These results suggest that using a heatsink while cementing prostheses may reduce the peak bone temperature.
Hip fractures are common injuries in the elderly, with significant mortality and morbidity from several factors. Many of these patients have cardiac disease, and some develop cardiac complications which may increase mortality. Troponin T is a marker of myocardial injury but can be raised in other conditions. Patients over 60 years old admitted with hip fracture during the study period had their troponin T measured on admission and following surgery. Assay was performed after the patient had completed their treatment. We report the results of this study one year after the last patient was admitted. 108 patients were recruited. The average age was 84 years; 86% were female. This study found that 27% of hip fracture patients had some increase in the troponin T levels in the peri-operative period. This increase was not associated with an increase in early mortality, but there was an increase in one-year mortality for those with an increase in troponin T (45% versus 22%, p=0.03). These findings indicate that the routine measurement of troponin T after a hip fracture is unnecessary.
