A surgical saw blade is used to cut the tissue against which the blade is applied. Many surgical saw blades are configured to cut hard tissue, bone. A sagittal surgical saw blade is a surgical saw blade with a head that pivots around an axis that is perpendicular to the plane of the blade. Some surgical saw blades are known as reciprocating saw blades. This type of blade is designed to so the body of the blade moves back and forth along the longitudinal axis that extends along, though, the body of the blade. Both types of saw blade include features that facilitate the releasable attachment of the blade to the saw used to actuate the blade. The saw includes a motor. When the saw motor is actuated, the saw moves the blade in a back and forth pattern. As implied by the name, a reciprocating blade is, when actuated, considered to reciprocate back and forth. A sagittal saw blade, when actuated, is often considered to oscillate back and forth around a pivot point.
PCT Pub. No. WO 2006/017066A2/U.S. Pat. No. 7,497,860 and PCT Pub. No. WO 2007/030793/U.S. Pat. No. 7,704,254, the contents of both of which are incorporated herein by reference, each disclose a sagittal saw blade cartridge. A sagittal saw blade cartridge includes a static guide bar and a blade. The guide bar is an elongated assembly that is releasably attached to the handpiece, the saw, that actuates the cartridge. The blade is pivotally mounted to the guide bar. The blade has teeth that extend forward of the guide bar. Also part of the cartridge and internal to the guide bar are one or more drive links. Each drive link extends from the blade towards the proximal end of the guide bar. The drive links are reciprocated back and forth by a drive assembly internal to the saw. The reciprocation of the drive links causes the blade to pivot, to oscillate, back and forth. The pivoting of the blade is what enables the teeth to cut the tissue against which the blade is pressed. Sometimes, this type of cartridge is referred to as an oscillating tip saw blade cartridge.
An advantage of the sagittal surgical blade cartridge is that the only portion of the cartridge that pivots is the distally located blade. In contrast, a conventional sagittal saw blade pivots from its point of attachment to the saw to which the blade is attached. As a consequence the saw to which a cartridge is attached vibrates less than the saw to which a conventional sagittal saw blade is attached. Thus, the saw to which a sagittal surgical blade cartridge is attached can be easier to control than a saw to which a conventional surgical sagittal saw blade is attached. Also, it is common practice to use a cutting guide to properly position a sagittal saw blade relative to the tissue the blade is intended to cut. When a conventional blade is actuated, the oscillating movement of the blade wears against the surfaces of the cutting guide defining the slot in which the blade is seated. The guide bar of a surgical sagittal blade cartridge only minimally moves in this slot. Thus, by using a cartridge, instead of a conventional blade, less of the material forming the cutting guide is rubbed off the guide. This reduces the extent to which the surgeon has to flush worn off cutting guide material from the surgical site. Further, use of the oscillating tip blade reduces the extent to which the material forming the guide becomes so worn that the guide itself is rendered useless.
A surgical sagittal blade cartridge has another benefit over a conventional sagittal saw blade. Since the guide bar remains static when the blade is actuated, the practitioner can press one or more fingers against the guide bar. This facilitates the holding of the cartridge in the desired position as the cartridge is advanced against the tissue that is to be cut.
PCT Pub. No. WO 2006/017066A2/U.S. Pat. No. 7,497,860 also discloses a reciprocating blade cartridge. This cartridge has a blade that extends laterally, from a side of the bar portion of the cartridge. A drive rod internal to the bar reciprocates the blade back and forth along an axis that is parallel to the proximal-to-distal longitudinal axis through the bar. The Applicant's U.S. Prov. Pat. App. No. 62/268,536, the contents of which are explicitly incorporated by reference and contained in U.S. patent application Ser. No. 16/062,727/PCT Pub. No. WO 2017/106533 A2 also discloses a reciprocating blade cartridge.
Surgical blade cartridges work well for the purposes for which they are designed. Nevertheless, a surgical blade cartridge shares a limitation with a conventional surgical saw blade. It can be difficult for the surgeon pressing the blade cartridge against bone to control the depth of the cut of the cut of formed by the cartridge. Essentially a surgeon has to rely on the feel of the saw and cartridge to determine if the blade has formed the desired cut and the surgeon should stop applying a forward force to the cartridge. It is desirable to so stop plunging the blade forward because it is typically undesirable to allow the cartridge to cut the soft tissue inwardly of the bone. To ensure that blade cartridge does not advance beyond the desired depth, the surgeon is required to control the force applied to the saw. Specifically the force needs to be sufficient to overcome the resistive force of the bone against which the blade is applied. The force, however, cannot be so great that, when the blade breaks through the bone, the momentum of the saw, results in the appreciable advancement of the blade through the underlying soft tissue. Simultaneously with having to so regulate the force applied to the saw and cartridge, the surgeon needs to tactilely sense the change in the resistive force to which the cartridge is exposed. The sensing of the sudden drop off of this force functions as the cue that the cartridge has cut through the bone being cut and that it is necessary to stop applying a forward force to the saw and the blade.
Having to simultaneously perform these control and sensing steps can add to the physical and mental stress associated with applying either a sagittal saw blade or a sagittal saw blade cartridge to the bone in which the cut is to be formed.
Further, there are a number procedures for which the most appropriate blade to form the cut bone is the reciprocating blade. This is true for procedures that involve forming cuts in the jaw. This is also true in many situations when it is necessary to form a cut in the sternum, the bone that covers the heart and lungs. When performing this type of procedure, the motion and shape of the sagittal blade typically does not make it possible to use this type of blade to form the desired cut. The incorporated by reference PCT Pub. No. WO 2006/017066A2/U.S. Pat. No. 7,497,860 discloses a sagittal saw blade cartridge with a blade that projects laterally, from the side of the guide bar. Even this type of sagittal blade cartridge has not proven to be a suitable replacement for a reciprocating saw blade. There are some reciprocating saws specifically designed to use a reciprocating blade especially designed to cut through the sternum. This means that a facility that performs both orthopedic surgery and surgery on the chest must have two types of saws available. A first saw needs to be provided to drive the sagittal blades used by an orthopedic surgeon. A second saw needs to be provided to drive the reciprocating blade a chest surgeon uses to access organs and tissue below the sternum.