14C bombe-pulse dating: a novel method to measure bone turnover in human sternum.

Heart surgery is most commonly performed through a central division of the sternum, a sternotomy. This procedure provides full overview of the thoracic cavity and access to the organs within. At the department of Cardiothoracic & Vascular Surgery at Skejby Hospital alone, over 1000 sternotomies are performed each year. When closing the sternum, the normal procedure is to use steel wires to hold the two sternal halves together. Following surgery, sufficient healing of the sternum is important to prevent complications and to ensure a high level of quality of life for the patient. It has been shown that forces, equally to those produced during a normal cough, can displace the wire-fixated sternum by more than 2 mm. Reduced stability of the sternum has a negative impact on the healing process and increases the risk of infections. Another known complication to sternotomy is pseudoarthrosis (nonunion), which is caused by insufficient healing of the sternum and may result in instability, chronic pain and reduced quality of life. These complications result in prolonged admittance time, increased mortality and morbidity and from a financial point of view, increased treatment-costs for each patient.
Today, the rate of bone turnover in the sternum is unknown. It is unclear whether the normal bone physiology of the sternum might be a contributing factor to the reduced healing after sternotomies. Standard method used to measures bone turnover is by labeling with the antibiotic tetracycline.
The radiocarbon isotope 14C has for long been used to determine age of archaeological findings. 14C is also part of human connective tissue collagen and can be measured by accelerator mass spectrometry (AMS)5. Due to nuclear-bomb testing during the Cold War, atmospheric 14C concentrations dramatically increased until the declaration of the Test Ban Treaty in 1963 when levels again deteriorated. This swift peak in atmospheric 14C concentrations is called the “Bombe-pulse”. It is possible to determine formation age of a specific tissue with a known turnover by comparing atmospheric 14C concentrations with 14C concentrations in that specific tissue. This method is called 14C bombe-pulse dating. 14C bombe-pulse dating can also be used to determine unknown turnover in a certain tissue by comparing formation age, tissue 14C concentrations, and atmospheric 14C concentrations. We therefore wish to investigate whether 14C bombe-pulse dating can be used as a valid method to measure bone turnover in the human sternum.