In the field of surgery, the importance of thorough cleaning of exposed tissues has long been recognized. In orthopedic surgery, the need for cleaning bony tissues is an added concern. Traumatic wounds, which can involve both soft and bony tissues, must be thoroughly cleansed of contaminants in order to minimize the risk of serious infection. The same risk requires that soft and bony tissues at surgical sites for procedures such as prosthetic joint replacement must also be thoroughly cleansed.
Cemented joint replacement surgery also requires especially thorough cleaning of the bone bed sculpted to receive an implant, for two additional reasons. The bone cement (typically polymethyl methacrylate) which secures the implant to the prepared bone is not an adhesive material, and accordingly, successful prosthetic fixation depends upon intimate mechanical interlock between cement and the open, three-dimensional network of cancellous bone surrounding the implant site. Thorough removal of fat, debris, and fluids from this bony network prevents these materials from forming an interposed layer between cement and bone, and thus allows for more direct cement-bone contact, helping to contribute to improved long-term mechanical fixation. Secondly, placement of cement into a prepared bony cavity, followed by insertion of the implant, often generates significant pressures which can force fat or particulate debris into the patient's circulatory system. Fat embolism has been a serious potential complication of cemented joint replacement surgery, but the incidence has been shown to be reduced by thorough cleaning, which removes substantial volumes of fat, marrow, and debris from the prepared bone bed.
Cleaning, or lavage, of the prepared bone surface or other tissue is generally accomplished by rinsing and flushing with a saline solution, which washes away surface debris. Traditionally, this has been accomplished by manually squirting saline from a bulb-style syringe. More recently, a variety of commercially available lavage devices have been developed, which deliver the saline solution in a pulsating stream, at higher flow rates and impact forces than can be readily achieved with manual delivery. Examples of these pulsatile lavage devices are described in U.S. Pat. No. 4,662,829 (Nehring), U.S. Pat. No. 4,583,531 (Mattchen), and U.S. Pat. No. 5,046,486 (Grulke et al.). Each of these devices delivers a stream of discrete pulses of saline to the surgical site.
Pulsatile lavage has been shown to contribute to improved cleaning of the trabecular bone. Intermittent flow may temporarily interrupt the formation of hydrostatic blockages in the bony pores, and further the pulses of saline may help the bone to "throw off" debris, as it rebounds from the impact of each delivered pulse. Mattchen and Grulke et al. both emphasize the importance of sharp irrigant pulses for effective cleaning. In both of these devices, the pulses of saline are delivered with relatively sharp on-off characteristics, so that the liquid stream comprises a series of repetitive impacts.
Each of the three devices mentioned above (Nehring, Mattchen, Grulke et al.) relies upon a pressurized gas to drive the pumping action. The gas typically employed is compressed nitrogen gas, which is readily available in the operating room because it is a common power source for surgical instruments such as drills and saws. The Nehring patent describes a diaphragm pump, in which the liquid is moved by the expansion of a flexible elastic diaphragm under pressure from the gas. Expansion of the diaphragm pressurizes the liquid contained in an adjacent chamber. Both the Mattchen and Grulke patents describe piston-style pumps to drive the saline solution. In each, the pump is powered by a compressed gas, as mentioned above. The Mattchen device employs a sliding valve timing assembly, and utilizes a disposable pump cartridge which is locked into position in a resterilizable handpiece for use. The Grulke device utilizes a spring-loaded piston pump, contained within a fully disposable handpiece unit to eliminate the need for hospital sterilization.
In all three of these devices, care is taken to ensure that the pathways for saline and pressurized gas are kept completely separate, and that the gas is safely vented away from the surgical site. This is an important patient safety feature, because the nitrogen gas typically employed with surgical instruments diffuses very slowly in physiological fluids, and therefore blood uptake of the gas can form a gas embolus, possibly leading to significant physiological disruption. Pressurized air directed at the surgical site could lead to similar problems, both because of its high nitrogen content and because oxygen also diffuses slowly in physiological fluids.
U.S. Pat. No. 5,037,437 (Matsen) describes a device for cleaning and drying the bone bed with a stream of physiologically benign flowing pressurized gas, to aid in more complete removal of debris and fluids. Flowing gas has been found to be helpful in loosening impacted bony debris and in lifting debris, fat and fluids from trabecular recesses and bringing them to the surface for more complete removal, which allows for better cement-bone interdigitation. This patent teaches the use of carbon dioxide or another gas with similar diffusibility in physiological fluids, an important safety feature to minimize any risk of gas embolism, as noted above.
Surgical procedures for repair of a variety of conditions caused by disease or traumatic injury may involve the application at the surgical site of one or more agents which serve therapeutic purposes. An example of this would be the application of antibiotics to the tissues exposed by the surgical or traumatic wound, to minimize the risks of wound infection and its accompanying physiological complications.
Surgical lavage devices are generally used to irrigate and cleanse the wound with saline solutions, and antibiotics may be added to the liquid solutions so that they can be washed over the surgical site. Other therapeutic or bioactive agents are applied topically to the exposed tissues. One example of this would be the use of topical hemostatic agents, often applied to the exposed bone surfaces to reduce bone bleeding in orthopedic joint replacement procedures. An agent such as thrombin or epinephrine is mixed into a small amount of liquid and dabbed onto the bone with surgical gauze sponges. In other instances, materials such as hydroxyapatite compounds are applied to the sculpted bone bed in order to facilitate bone growth and repair.
In contemporary surgical devices, delivery mechanisms for such materials are limited to admixing with volumes of saline, or manual delivery such as with sponges. In the first instance, the materials applied are diluted by the liquid solution, and are flushed through and across the site in the liquid stream, limiting the user's ability to place the material at a specific site. In the second instance, delivery efficiency is limited to the uppermost exposed surfaces which can be contacted by a sponge or similar device.
There is a need in the art for surgical devices and methods which address at least some of the above concerns or other concerns for preparing bone and other tissues.