Waterjetting 17e - Liposuction and other medical uses

One of the advantages of using high-pressure waterjet streams as a cutting or cleaning tool is that, unlike more mechanical devices, there is much less need to apply additional force through the tool in order for it to work. This was one of the considerable advantages that waterjetting had when it was first introduced, and married with robotic arms in cutting different materials. Early robots had little arm strength – it was a major constraint in the design of new equipment since we had to recognize that, for example, in order for the arm to keep its precision and accuracy we could apply no more than ten or twenty pounds of thrust through the nozzle. This limit was overcome when the power was applied from a jet at 50,000 psi pressure, over a very small nozzle diameter and meant that the combination of robot controlled manipulators and jet nozzles could cut complex shapes in materials ranging from shoe leather through carpet, through automobile and aircraft components.

That advantage remains as tool size is shrinking and waterjets are gaining an increasing role in the medical part of the waterjet market. I had mentioned, in previous posts, how waterjet systems are increasing being used to debride wounds, remove cancers and help expose blood vessels in liver surgery. But with the small sizes of nozzles that are now available, it is also possible for jets to be transmitted through the small tools used in laparoscopic (keyhole) surgery. As a result surgeries can be smaller in scale, less traumatic to the patient and faster to heal because of the smaller footprint of the surgery. In liver surgery, as an example, the increasing use of waterjets in resection has reduced the amount of transfusion liquid required by more than 75%.

Tool sizes have continued to shrink, and thus it is now possible to use the jets in surgeries beyond those that we originally envisioned. For example there have been a number of studies over the years on the use of waterjets to cut bone. One of the problems in hip, knee and other joint replacement surgeries is that the faces of the cuts need to be quite precisely aligned in order for the prosthesis to fit into place. With surgeons using a common saw to cut through the bone, the cut can deviate from that clean alignment. Further the saw can generate heat that can damage the bone and tissue along the cut line. High pressure jets both cool and help align the cut to minimize misalignment of the cut line.

Other tissues are more easily cut, and waterjets are being used more extensively in tumor removal and in cutting the ligaments that hold organs, such as the gall bladder or prostate in place, making endoscopic surgeries easier.

Other body tissue can also be removed. As I have updated the range of applications for waterjets in the medical field over the years it is only now that I am finding references to the use of waterjets in liposuction. Waterjet Assisted Liposuction (WAL) has been described as:

Using a fan-shaped laminar jet, the body-jet® simultaneously irrigates and aspirates fatty tissue. The gentle separation of fat cells from connective tissue minimizes trauma to the patient. At the same time, significantly less infiltration fluid is needed with the WAL procedure as compared to traditional methods, helping to reduce exposure to tumescent fluid, minimize swelling, allow real-time precise contouring, and dramatically shorten procedure times.

Other sites provide similar comments:

Body-Jet Water Liposuction relies on the power of highly concentrated water to gently dislodge and remove fat cells from the body. Using water-jet technology, fat is removed from the body with significantly less force than older liposuction techniques. The power of the water-jet detaches fat cells from their surrounding tissues, allowing the suction cannula to move freely. This limits the possibility of trauma to surrounding tissues, including skin, muscles, nerves, blood vessels, and septal attachments. . . . . . Because the process is so gentle, Body-Jet Water Liposuction is typically performed as an out-patient procedure under local anesthesia. On average, the entire procedure takes between 30 to 45 minutes for each part of the body that is treated. The majority of body-jet water liposuction patients find that they can return to their regular activities immediately following the procedure. In fact, Body-Jet Water Liposuction has been called “lunch break lipo” because most patients are able to have the procedure performed and immediately resume regular activities.

There is a video about the procedure here .

As I mentioned earlier in regard to back surgery the small amount of damage outside of the region where the jet is cutting means that many of these procedures can be carried out as outpatient surgery with the patient being able to leave without hospitalization. Further because the jet works by discriminately removing the desired tissue without damage to surrounding hard tissue, and it can reach “around corners” to flush out cavities it has been reported, for back surgeries:

In treating spines, where the disc is removed before carrying out spinal fusion the waterjet was able to get out some 96% more of the soft tissue that was achieved by conventional means.

More refined applications, such as in breaking up blood clots in thrombectomy have also now been developed, The technique appears to be more widely tested in Europe than in the United States at the moment. It has been approved for use in the United States.

Each year in the U.S., approximately 600,000 patients are diagnosed with deep vein thrombosis. Complications range from severe pain and limitation of mobility, to limb loss and even death. Moreover, 200,000 people die from pulmonary embolism (PE) each year, which occurs when venous thrombus migrates to the lungs and blocks blood flow. . . . . . The FDA's clearance of AngioJet thrombectomy . . . . . gives doctors a powerful tool to restore flow to blocked veins. Patients may benefit from faster resolution of leg pain and reduced risk of complications.

There are, in short, increasing applications for high-pressure waterjets in the medical field, and the advantages which the tool brings to cutting in more mundane applications seem also to carry over into surgical applications. It has only, however, been after smaller and more precise tools have been developed that this set of applications has evolved, and it will be interesting to see how much longer the list grows in the years to come.

Waterjetting Technology 17d - Some medical applications - don't blink!

Our discussion on the ability of high-pressure waterjets to remove some materials without damaging others has, as I noted in the last post, found some applications in the medical field. The example that I provided in that post dealt with the use of waterjets to dislodge material in the cleaning of wounds, or to carefully excise thin layers of burnt flesh without doing damage to the underlying tissue. I also pointed to the ability of a waterjet to remove weaker diseased tissue, such as brain and skin tumors, without damaging the surrounding tissue, which is healthy and thus able to resist the pressure of the cleansing waterjet.

There are a number of other applications in the medical field which have developed from these advantages. The first is in surgery on the liver and kidneys in particular. In these organs there are generally a large number of blood vessels that carry blood through the organ so that the blood can be cleaned of impurities. The difficulty that this creates usually occurs in cases where the organ becomes diseased. Medical treatment recommends that the diseased volume of the organ be removed, and the historic method for doing this has been to take a scalpel and carefully cut around the diseased region, so that it can be lifted out. This is often referred to as liver resection.

The problem that this creates is that, in the process of cutting out the diseased part of the organ, the surgeon must also cut through the blood vessels in that part of the organ. Because they are buried in the organ, it is not clear where these vessels are, and they are conventionally difficult to isolate. Early work in finding an answer was carried out in Japan.

However blood vessels are relatively tough (and when full of blood require pressures of around 2,000 psi or more to penetrate) whereas the surrounding tissue is much softer. As a result – using the same conceptual approach that I described last time for the removal of skin cancer, a surgeon can remove the tissue from around the blood vessels and along the projected line of dissection, without cutting through the vessels. Tests during brain operations have shown that as long as the pressure is kept below 300 psi there is no damage to any of the vessels in the brain, and similar conclusions are likely to hold for other organs in the body. The jet was, however able to remove diseased tissue, while leaving healthy tissue.(In these surgeries the jet is on the order of 100 microns in diameter, and as a result uses very little water during the operation.)

Figure 1. Japanese surgical removal of liver tissue around blood vessels of the liver, exposing them so that they can be tied off, before being cut, thereby significantly reducing blood loss.

Clinical trials rapidly spread around the world, Papachristou had published on the technique in 1982 when, after 75 trials with dogs it was tried in four male human patients. At the time it was noted that there was significant reduction in blood loss. This is fairly critical in older patients (who are more likely to need these operations) since large losses of blood can induce shock, and can be fatal. Blood loss is the most common complication of the surgery and consequent cause of death (which now runs around 5%, but was higher prior to waterjet introduction).

It also impacts long-term survival and post-operative complications. (Historically the problem was addressed using what is known as the Pringle manoeuvre in which all the blood flow to the liver is halted by clamping for the period of the operation. However this can only be applied for limited amounts of time and is of limited effectiveness.) Using a waterjet approach has the advantage, over ultrasonic and cavitating techniques, that the path cut through the liver is narrower and the vessels are more clearly delineated. At the same time, as figure 1 shows, the sides of the cut are relatively clean and well defined. The jet is able to handle the tougher tissue in a cirrhotic liver either through a longer residence time, or by raising the pressure of the jet by about 150 psi.

The very narrow cut achieved by the waterjet has another useful feature in that the jet will, in fibrous tissue, push apart the fibers rather than fusing them, as would be the case with laser cutting. This has advantage in eye surgery where any such fuse points can cause scarring that interferes with future vision, while the separation of the tissues with the jet does not carry that problem.

Figure 2. Precision cutting across the face of the eye at a jet pressure of 20,000 psi and with a jet diameter of 10 to 100 micron.

The technique was first announced in 1994 and animal tests had been successfully completed by 2001. Because the jet cuts so fast (less than a second per cut) there is no tissue loss. (The operation uses a device that fits to the eye to hold the lens in the right position to make the cut).

The technique has not, however, been that successful in the field as has another application, that of removing herniated disks in the spine. The technique uses a procedure known as Hydrocision. It is interesting to read a quote from an article last November on the technique:

"It's basically a high-velocity water jet eroding system," Kevin Staid said about the medical device that his North Billerica, Mass.-based company makes. "And this is our first entry into the area."

With HydroCision, a jet of saline solution comes out of a nozzle that is 0.005 inches in diameter -- "slightly larger than a hair" -- and can cut away protruding disc tissue that can cause the back and leg pain without an actual blade.

"Just the energy of the jet would be doing the cutting," said Staid, an engineer. "In our case, the water is going about 600 miles an hour and has the ability to cut quite effectively."

The advantages of the 20-minute outpatient procedure are: No hospitalization, quicker recovery times, less pain, no surgical trauma to the back muscles and no general anesthesia.

"There is no muscle damage, no bone removal, no nerve root manipulation ... and the size of the wound is approximately 4 mm," Kowalkowski said.

The use of the tool is sufficiently popular that in 2009 the company (Hydrocision) announced that the tool had been used in more than 40,000 procedures.

I’ll give other medical examples in the next post.