NEW INSTRUMENTS

Sternal Safety Blade for Median or Transverse Sternotomy

Joseph Hodge, MD, Spartanburg, South Carolina

Sternal splitting incisions are used to approach the anterior, superior, and middle mediastinum for re- moval of lesions of the thymus, exploration for parathyroid adenomas, and for open heart proce- dures. The midline incision affords excellent expo- sure of the right atrium, superior vena cava, pulmo- nary artery, and aorta and is useful for treating traumatic injuries to the heart and great vessels. The safety blade is especially helpful in exposing the mediastinum a second time for repeat cardiac valve or coronary bypass surgery.

Material and Methods

The blades are triangular and circular (Martin Medi- cal-surgical Instruments Co., Desota, KS). The triangular blade is one that oscillates, consisting of stainless steel, to which there is attached a guard element to prevent injury to the heart and great vessels of the mediastinum. The safety guard on the triangular blade is an arcuate member measuring 1 cm and extends along the cutting surface of the blade (Figure 1). The circular safety blade (Figures 2 and 3) contains a guard element that extends around the circumference of the saw blade and is eccentrically located 1 cm, 2 cm, and 2.5 cm from the cutting edge of the blade. The blades oscillate and can be attached to a conventional power source, such as the Hall air driver (Martin Medi- cal-surgical Instruments). The circular sternal blade is more commonly used, but the triangular blade is indicated in large chested obese patients.

The marrow cavity varies with the age and the sire of the patient. The average adult sternum measures 1 cm to 2.5 cm in thickness, and the average depth from the outer table through the marrow cavity and the inner table is approxi- mately 1.5 cm. The sternum is thickest at the manubrium and thinnest at the xiphoid process. The depth of the an- terior mediastinum is significantly reduced after previous cardiac or mediastinal surgery. The operator rotates the saw blade to the 2.5 cm edge at the manubrium, and the depth of the blade is decreased to 1 cm at the xiphoid process, thus permitting the blade to safely penetrate the outer table, marrow cavity, and the inner table. The guard

From ths Department of Sugery. Spartanburg General Hospiil, Spartanburg, South Carolina.

Requests for reprints should be addressed to Joseph l-lodge. MD, l-lodge Building, 964 North Church Street, Spartanburg. South Carolina 29303.

safety rests on the outer table, thus preventing penetration and injury to the great vessels of the mediastinum and the heart.

Technique

A midline sternal incision is made through the skin’s subcutaneous tissue from the upper border of the manu- brium to the xiphoid process and carried distally to the proximal linea alba [I]. With the sternal safety blade, the sternum is split from the suprasternal notch to the xiphoid process by rotating the power source to which the blade is attached, beginning at the 2.5 cm marking at the manubrial level. As the blade oscillates through the outer table, marrow cavity, and through the inner table, the semicir- cular guard element locks by resting on the outer table of the sternum, thus preventing the saw blade from pene- trating deeper into the mediastinum and avoiding injury to the innominate veins and to the pericardium. In some cases, depending on the size and age of the patient, it may be necessary to utilize the safety blade to penetrate the outer table and marrow cavity, and sternotomy is com- pleted with the Lebsche knife.

Transverse sternotomy is performed by making an incision below both breasts over the fourth intercostal space through the skin’s subcutaneous tissue and fibers of the pectoralis major. The anterior intercostal membrane

_ WARD ELEMEWI

Flguru 1. Trfaqvdar safety power bfade. Safefy guard efenmni on each side of blade.

402 The American Journal of Surgery

Sternal Safety Blade for Sternotomy

power ’ bleds.

F&we 3. Chwiar power sa&fy blade, side view.

and external intercostal muscles are divided. The internal mammary vessels lying 1 cm lateral to the outer border of the sternum are secured. The sternum is divided, thus providing excellent exposure of the heart and great ves- sels.

In children and very thin patients, care must be taken to stop before the guard reaches the outer table of the sternum. In second-look patients, if there is any question as to the thickness of the sternum, the combination tech- nique of the safety blade saw and the Lebsche knife should be utilized.

Summary

Sternal safety blades are useful for splitting the sternum in approaching the anterior, superior, or middle mediastinum for the removal of lesions of the thymus, exploration of parathyroid adenomas, re- moval of large substernal thyroids, open heart pro- cedures, and traumatic chest injuries. One of the chief indications for using the safety blade is in pa- tients undergoing second open heart procedures, since the anterior mediastinum is markedly reduced in size, thus making the heart and great vessels vul- nerable to injury.

Acknowledgment: I wish to express my appreciation and thanks to Dr. John Y. Templeton, III, and his asso- ciates for their comments.

References

1. Gibbon JH. Surgery of the chest. Philadelphia: WB Saunders, 1962:146.

vofuma 149, soQtmfm 1994 403