The present invention relates to disposable scalpels and, in particular, to retractable-blade types thereof.
Medical personnel, especially highly skilled surgeons, are at risk every day from accidental stabbing. Scalpels must be passed from one person to another and back again in surgical procedures. In addition, a surgeon may retain a scalpel in his grasp while trying to use another instrument such as a hemostat or retractor or to adjust an overhead lamp, making it highly likely that an accidental incision or laceration will cause undue harm to a patient or other medical personnel whose hands are nearby.
Injuries arising from the above accidents are known as “sharps” injuries. Medical personnel are always at risk of contracting potentially fatal bacterial and/or, viral infections, including HIV and Hepatitis B and C. It is desirable to cover or shield a scalpel blade when the scalpel is not specifically being used for cutting in a desired place and process.
The simplest way to protect an exposed scalpel blade is cover it with material that won't be subject to being cut when the cover is in place. However, a wide preference among surgeons for scalpels with non-covered blades leads to a single and simple conclusion. The mechanisms and structures in the prior art used to effectively cover scalpel blades are not being used because they unduly interfere with or distract the surgeon. Such surgeons find that they would rather accept a terrible risk of infection to themselves and harm to the patient instead of accepting the reduced surgical performance available from covered blade scalpels that have covers that can be removed before and replaced after use. In many, if not most, prior art blade covers, just the act of removing or replacing the cover exposes the surgeon to risk of injury from the blade.
One type of scalpel with a blade cover are those that cause the blade to be retracted into a cover housing. The cover housing is essentially the scalpel handle. Several serious design challenges arise almost immediately when a scalpel blade must be retracted into a scalpel handle. The mechanism incorporates a spring so that, when released, the blade is automatically withdrawn into the handle. Means are required to maintain the blade in its extended position against the retractive bias of the spring.
U.S. Pat. No. 5,531,754 describes a retractable blade mounted on a blade holder mechanism housed within a cover housing. The housing has regularly-spaced notches while the blade holder mechanism includes a resilient spring clip that is biased against the sheath. When the spring clip engages with a notch, the blade is held in position until pressure is exerted on the spring clip to release the blade for extension or retraction with respect to the sheath. Once extended from the handle, the retractable blade of U.S. Pat. No. 5,431,672 is locked in place by pivoting a button. The button includes a shaped post that, when in one position, allows movement of the blade into and out of the handle but prevents movement of the blade when the button is pivoted through 900. The blade may be permanently locked within the handle by movement of the blade holder mechanism to its fullest extent and over a cleat. The cleat prevents further movement of the blade into or out of the handle so the whole device may be disposed of safely.
U.S. Pat. No. 6,022,364 describes a retractable blade with a rocker switch. The switch includes an internal molding that latches over a bar within the handle to prevent movement of the blade into or out of the handle. Accidental emergence of the blade from the handle is limited by a depression in the internal face of the handle which receives the internal molding of the switch when the blade is fully retracted within the handle.
All the blade locking devices described in the prior art are designed for quick and simple release of a blade so it is automatically retracted within a sheath or handle where its cutting edge and sharp point are protected. However, the Applicant has discovered that these quick-release locks present a substantial problem during surgery when the stability and reliability of surgical implements is of paramount importance. In particular, the Applicant has found that the locks are too easily released, causing accidental retraction of a blade within its handle. The application of the rocker switch described in U.S. Pat. No. 6,022,364 requires a single action with no fallback lock, cover or protection. Indeed, the switch may not be locked properly over the internal bar so an accidental knock of the switch will allow the blade to retract into the handle. Similarly, the pivotable button of U.S. Pat. No. 5,431,672 may not be engaged properly and may be knocked accidentally or worked round during use of the scalpel, thereby allowing accidental retraction of the blade while in use.
It will be appreciated that such accidental retraction of a blade is not only inconvenient but may cause serious injury to the user as well as to a patient. It also breaks the user's concentration and requires the user to interrupt the surgical procedure to re-set or check the blade.