HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Edward B. Diethrich Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Diethrich, E. B. Search for Related Content PubMed PubMed Citation Articles by Diethrich, E. B.

J Thorac Cardiovasc Surg 1994;107:1157-1159
© 1994 Mosby, Inc.

LETTERS TO THE EDITOR

The sternal saw: A historical note with a modern message

Chief of Cardiovascular Surgery
Arizona Heart Institute & Foundation
Phoenix, AZ 85006

To the Editor:

At the beginning of my rotating internship in the summer of 1961, I had already received an appointment in the neurosurgical residency program at the University of Michigan under the world-famous neurosurgeon Dr Edgar A. Kahn. His instructions to me were specific: "Complete the internship, then one year of general surgery, and come to my program with some research experience."

Even at this time, however, research was no stranger to me. I had spent many nights and long weekends in the dog laboratory working on homemade arterial grafts and various vascular projects, including a heat exchanger to rapidly cool the brain during various neurologic maladies.

Certainly, the challenges of neurosurgical research were acceptable, but entering the skull to access the brain was formidable. Drilling three burr holes in a triangle and uniting them by seesawing back and forth with a Gigli saw seemed not only extremely time-consuming but, quite frankly, barbaric. I therefore set about to develop a "proper" saw for cranial entry, one that not only would expedite my own research but also assist clinical neurosurgeons confronted with exposing the brain on a daily basis.

The project did not seem conceptually too difficult. Certainly, the handyman's oscillating saber saw could adequately cut any bony structure. The only missing element was a method to protect the underlying dura mater and the brain beneath it. The problem appeared solved when I devised a small protective shield to attach at the end of the cutting blade. Like so many research endeavors, however, what at first seems simple often turns out to be complex.

Despite numerous variations in the design of the "protective" footpiece, the limited space between the underside of the cranium and the epidural surface was too shallow. The result was persistent injury to the brain tissue and great frustration and discouragement on the part of the researcher.

One evening, after another failed experiment, it suddenly occurred to me that the Gigli saw was not the only grotesque instrument in the hands of skilled surgeons. The Lebsche knife, actually a right-angled chisel hit with a mallet, was what the new generation of cardiac surgeons were using to access the anterior mediastinum. Could my poorly functioning saber saw cum footpiece be used to split the sternum?

Quickly, another dog was anesthetized, but this time positioned with all four paws upright. As thin as a dog's sternum is, the saw made a perfect midline cut. The following week, two median sternotomies were performed without incident in human beings.

The device was named "the sternal saw" and described in the July 1962 issue of Surgery. (The editors must have wondered why the development of a sternal saw was sponsored by a grant from a neurosurgical foundation! ) It was later marketed by Sarns, Inc. (I was instructed by one of my professors that it would be unethical for me to have my name attached to the saw or to be involved with the manufacture of equipment that could benefit me personally! ) The saw became the standard method for opening the mediastinum and was used exclusively in many institutions around the world.

Now the scene changes to 1993. Many expert and experienced surgeons today elect not to use the sternal saw if the sternum has been opened previously. Rather, they prefer an oscillating blade, assuming it is less likely to cut into the pericardium or myocardium lying beneath the bone. I even understand that the current instruction sheet that accompanies the saw does not recommend its use for "redo" situations.

I must raise a technical detail as it relates to this point. The early developmental use of the saw, where dura mater was being pushed away from the oscillating blade, is identical to the sternotomy redo scenario. In the original journal article describing the saw, I noted, "The saw is equally effective when reoperation necessitates splitting the sternum for a second time."

I then went on to explain, "While the operation of the saw would seem obvious, the natural tendency to lift the saw and footpiece against the sternum may produce inhibition of the cut. This is most likely to occur at the sternal angle. Relieving the upward tension allows the saw to cut freely."

A similar problem arises, however, when the saw is applied in redo sternotomies with the same technique as for de novo exposures. In the redo situation, there are always adhesions present, and if the saw is advanced forward in a continuousmotion, there is the opportunity for tissue injury (Fig. 1, A). However, if a forward-reverse (to-fro) motion is used, the footpiece of the saw will disengage from the adhesions, creating a pathway (Fig. 1, B). Attention to this technical detail is of paramount importance and will, in the majority of cases, prevent saw-induced injury, although every cardiac surgeon realizes there are no foolproof methods where the aorta or right ventricle has become part of the healed incision on the back wall of the sternum.

View larger version (41K): [in this window] [in a new window]   Fig. 1. The proper technique must be applied to avoid injury to the myocardium and great vessels during reentry into the anterior mediastinum with the sternal saw. First, the tissue should be cleared from beneath the manubrium with Mayo scissors used to free adhesions between the innominate vein, right ventricle, and epicardial surface. The index finger can then be advanced adjacent to the substernal border to create a free plane of dissection. A similar process is repeated at the xiphoid end of the sternum, thereby creating the most ideal entry point for the sternal saw. A,Continued forward advancement of the saw (and attached footpiece) should be avoided. There is potential for the footpiece to catch or snare on an adhesion, which could result in laceration of the ventricle or other vital structures. B,Rather, the saw is advanced only a short distance and then retracted slightly to free the footpiece of any tissue (lungs are completely deflated during the reopening of the sternum). If any resistance is noted as the advancing maneuver proceeds, the saw is retracted to assure that there is no tissue adherent to the footpiece.

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Edward B. Diethrich Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Diethrich, E. B. Search for Related Content PubMed PubMed Citation Articles by Diethrich, E. B.