A plumb line is a vertical line that is created from a string that has a suspended weight. The suspended weight in ancient times was probably a stone and was replaced by lead in medieval times, as it was dense, heavy, and resisted movement from the wind. In modern times, the lead was replaced by a brass conical cylinder with a point at the bottom. The reproducible and constant vertical reference line created by this construct is known as the “plumb line.” It is called a “plumb” line after the lead weight (Latin for lead is “plumbum”) from which the line was historically suspended.
Early use of the plumb line was recorded nearly 4000 years ago during ancient Egyptian times.1 The tool was in the shape of an “F,” with the plumb line suspended, from the upper outboard part of the F (Fig. 1). The backbone of the “F” was placed against a wall, and the wall was determined to be perfectly vertical, when the plumb line touched the middle outerboard part of the middle of the “F.” The Egyptians also used the plumb line to determine perfect horizontal reference lines as well. The plumb line was attached to the tip of an “A” frame, and the legs of the “A” were placed on a surface (Fig. 1). If the plumb line bisected the crossbar of the “A,” it was horizontal. This simple tool consistently and accurately defined horizontal and vertical planes and allowed for the complex construction of buildings, canals, and pyramids, which have endured for centuries.
As surgeons, we understand the need for a reliable and accurate reference or a “plumb line,” in order to execute the procedures correctly. We often reference intramedullary alignment, coronal alignment, and anatomic references to properly make our osteotomy cuts, place arthroplasty components, and reduce fractures. The concept of the plumb line can be translated into an imaginary line to assist in navigating the hand surgery jungle—from indications and contraindication of procedures, to safety checks preoperatively and postoperatively, determining pain prescription guidelines for patients, and for billing and ethical decision making. The early Egyptians noted that, without a plumb line as a reference, larger structures could not be built. Without a plumb line reference, there is the inadvertently slow drift from the reference line, which can occur without us recognizing it until we have drifted too far, and the building becomes off axis and unstable.
This imaginary plumb line of surgery can be the indications and contraindications of a particular procedure. The further we drift from this plumb line, the greater is the risk of not having the expected or optimal outcomes. Occasionally, our wishful thinking or not wanting to do something more complex allows us to rationalize the drift. It is in these situations that the plumb line becomes more important to guide us back to the true vertical.
The plumb lines in our profession are determined by the collective knowledge and experience of our mentors, peer-reviewed scientific articles, and ethics presented by our professional societies and by society. As we seek newer and novel surgical techniques and push the indications for procedures in an effort to improve outcomes, we must always keep the plumb line in view to reference our efforts.