Sternal marrow haemostasis is often obtained with the application of bone wax, with potential side effects pertaining to sternal wound healing. We illustrate an alternative technique which also offers some protection to sternal edges. Two lengths of tubing from the discarded cardiopulmonary bypass (CPB) circuit are cut longitudinally on one side. After sternotomy they are placed across each sternal edge and kept in position by two stitches and the spreader blades. They are removed just before sternal closure.
Efficient bone marrow haemostasis after sternotomy improves the surgical field, reduces blood loss, and preserves the patient's coagulative state. This is usually achieved with the application of bone wax which is very effective because it thoroughly seals the trabecular gaps of the sternal spongiosa. Besides, it is very practical because it can be applied with a finger, even in mini approaches, and in a matter of seconds. However, bone wax is a foreign body which degrades slowly  and is virtually impossible to remove completely at the end of the procedure because it penetrates deeply into the sternal marrow. In the severely osteoporotic sternum it is not uncommon to leave behind large chunks of wax in the spongiosa gaps.
There is a general consensus that bone wax may affect sternal consolidation , and in the elderly, obese, patients with diabetes, COPD, chronic renal failure, especially if on dialysis, and in patients on chronic steroid treatments it may increase the risk of a range of sternal wound complications . These may significantly prolong hospitalisation and trigger further problems. In the presence of an intramediastinal prosthesis like an ascending aortic graft, every serious wound problem may become a lethal complication. Senior surgeons are often unaware of the minor sternal wound complications because these are dealt with by junior doctors on the wards or family doctors at home.
Surgeons have looked for alternatives to bone wax. Some prefer not to use anything and rely on the speed of the surgical procedure and a short period off heparin, when blood is lost. Others apply drapes over the sternal edges onto which the pericardium is lifted either with the spreader blades or with suspending stitches. These drapes absorb a considerable amount of blood and are not properly haemostatic, allowing blood to freely gravitate into the pericardial cavity. The use of other chemicals is expensive [4–7].
Cardiac surgeons use bone wax, although with some concerns, because they feel that its risks are outweighed by its advantages and that there are no practical alternatives, but it would be preferable to avoid it altogether.
We illustrate a technique of obtaining satisfactory sternal marrow haemostasis and mechanical protection to the sternal edges.
2. Materials and methods
Two lengths of polyvinyl chloride (PVC) tubing, 15–20 cm long, from the discarded arterial side of cardiopulmonary bypass (CPB) circuit are used. Only if the sternum is particularly thick or the angle of Louis very prominent are segments from the venous side of the circuit used. These tubes, which maintain a curved memory, are cut longitudinally on one side and perpendicularly to the plane of curvature with straight heavy scissors. The sternum is divided and periosteal haemostasis achieved with diathermy. Immediately or after an initial sternal spread and anyway as soon as possible before the administration of heparin, two heavy-needle transfixing stitches (for example a 2 Vicryl stitch) are applied at each of the hemi-sternal extremities and are left untied. The tubes are placed over the sternal edges to wrap them completely. The stiches are then tied by an assistant over the tubes to keep them in position. Finally, the tubes are trimmed to the right length at the xiphoid extremities. The preparation and placement of both tubes does not take more than a few minutes.
The spreader is applied directly, without sternal drapes, and its blades maintain sternal adherence of the tubes and minimize the gap (Fig. 1 ) as do subsequent pericardial lifting stitches. When an internal mammary artery is harvested it is better to initially place only the tube on the opposite side. At present, there is not an adequate spreader able to sustain the wrapped sternal border without slipping. The second tube is placed once harvesting is complete.
The subsequent surgical procedure is carried out as usual. While on heparin some blood may accumulate at both ends of the tubes, mainly in the jugular cavity, but soon after administration of protamine significant sternal bleeding will cease. Bleeding at this stage is probably not sternal in origin. The time spent at the beginning to place the tubes is greatly compensated for at this stage of pre-closure haemostasis. Just before closure the two tubes are removed, leaving behind a thin layer of clot (Fig. 2 ). Any additional periosteal haemostasis is performed with diathermy and the sternotomy closed in the usual fashion.
A segment of PVC tube cut along one side and divaricated behaves like a spring with a strong tendency to recoil back to a cylindrical shape. When used to wrap a dry edge this tension produces a grip sufficient to make the tube self-retaining. On slippery surfaces, like a sternal edge, the grip is still present, albeit to a lesser degree. Therefore, tube wrapping seals sternal edges with a tight, waterproof surface and, together with some initial clots, it can contain sufficiently bone marrow bleeding and also contributes to periosteal haemostasis. At this point, there is no need to apply bone wax or any other haemostatic agents.
PVC wrapping also provides unequalled mechanical protection and support to the sternal edges, with no restriction of the operative field, which otherwise are exposed to spreader injury. This too can also favourably affect sternal consolidation especially when sternal edges, for any reason, are particularly vulnerable. This technique is sufficiently effective and relies on basic principles of haemostasis: compression and occlusion. It has the advantages of low cost, total reversibility, ease of application and absence of all the potential complications associated with the use of bone wax. It is sufficient in most circumstances.
The main and only drawback is that of course PVC sternal wrapping is not always as effective as bone wax and it is more difficult and time consuming to implement. Therefore, it is contraindicated, at least initially, in emergency and life savings procedures and its use may need to be pondered when the patient arrives in theatre with severe coagulative alterations or when the patient is going to remain heparinised after the operation, for example, for an insertion of intraortic balloon contrapulsation. If this is placed at the end of a procedure once the tubes are removed, bone wax, if needed, may still be applied. Sternal wrapping may be partially effective when there is an extremely prominent angle of Louis. Finally, sternal wrapping may be impractical in mini-sternotomy or other mimimally invasive approaches.
In routine cardiac surgery the sternum is split in the middle, made ischemic by the harvesting of one or two internal mammary arteries, generously burnt on both sides, stretched and deformed extremely and eventually perforated by sternal wires. But the application of bone wax is probably the worst of the insults because the sternum for its structure, as every other bone, is easily susceptible to infections which are difficult to eradicate. Also, the presence of a foreign body promotes infection.
The vast majority of patients seem to tolerate bone wax well, without any complication. Some will develop a superficial wound infection or dehiscence. Fewer will develop some degree of sternal instability whereas fewer still may require rewiring for sternal dehiscence. Very rarely mediastinitis will prove fatal.
The main effect of sternal wrapping is to decrease the incidence of sternal deishence, severe sternal wound infections, mediatinitis and lethal mediastinatis, at the cost of a modest increase of postoperative bleeding.
A comparative case–control study is currently ongoing.