A Note from Gene: Nearly two weeks ago, on Tuesday, April 8, 2014, I had a total right hip replacement. The surgery went very well. The biggest problem I encountered was nearly non-stop hiccups for the first week, which was likely due to the anesthesia. I was walking the next day, and I am now walking with only the assistance of a cane. Rehab is going nicely. With this going on in my personal life I thought it would be interesting to take a look at the evolution of hip replacement technology through the lens of issued U.S. patents.
Hip surgeries have been taking place for at least three hundreds years, and have progressed from rudimentary surgeries to the sophisticated total hip replacement (i.e., total hip arthroplasty or THA) surgeries that are so commonplace today. According to the CDC, during 2010 there were 332,000 in patient total hip replacements performed in the U.S. Indeed, hip replacement surgery today is widely recognized as one of the most successful surgical interventions ever developed. See Early Attempts at Hip Arthroplasty.
Modern days of hip replacement surgery really date back to the 1960s, with the development of new devices that reduced the wear sustained by artificial hip joints over time, and which provided more predictable outcomes. Still, as with all great scientific advancement, it is impossible to overlook the important discoveries of the early days. Without first steps in any scientific endeavor future steps are impossible.
With this in mind, today we embark on the first of our Evolution of Technology series, taking a look at the innovation history of hip replacement surgery and technologies, from the first femoral head attachments fashioned from ivory to current technologies which may enable surgeons to conserve more natural bone than ever before through the use of synthetic cartilage.
A Short History of Hip Replacements
By the late 1700s, surgical procedures involving the upper femur and hip had progressed due to discoveries earlier in the century regarding the physiology of skeletal tissues. Joint excision surgery had become a larger area of study at this time as an alternative means of treating major injuries sustained by commercial sailors and wounded soldiers. This allowed doctors to treat patients without resorting to radical life-saving techniques, such as amputation.
Many of the early hip joint innovations can be traced to the Westminster Hospital in London, where in 1821 the first reported excision arthroplasty was performed by Anthony White. After White’s excision arthoplasty various advances occurred in hospitals in France, Germany and Philadelphia. It wasn’t until the late nineteenth century, however, that the first recorded hip replacement occurred in central Europe. In 1891, Themistocles Gluck invented an implantable hip replacement, a ball-and-socket joint fashioned of ivory and affixed with nickel-plated screws. Thus, hip replacement surgery has been performed in one manner or another for 123 years.
Hip arthroplasty, the surgical repair or replacement of the musculoskeletal joint at the hip, progressed through the early 1900s, although treatments would often produce widely varied results. Earlier procedures would only allow motion for a few years before a patient would become severely handicapped, but by the 1920s, long-term mobility after hip arthroplasty could be achieved with fair consistency.
In the first half of the twentieth century, prosthetic hip joints grew in popularity among surgeons, and many new implantable joints were developed within a few decades. Along with ivory, other designs utilized rubber, acrylic and Vitallium, a metallic alloy trademarked in the 1930s by Austenal Laboratories of New York, NY. One of the earliest patents regarding hip arthroplasty was issued to Austenal Labs in August 1955. U.S. Patent No. 2,716,406, titled Hip-Nail Driver for Angular Hip Nails, protects a driver for angular hip nails that allows for the better use of guide rods when setting nails to treat hip joint fractures.
Another early patent on the subject lists Edward J. Haboush as the sole inventor. Haboush, a former surgeon at New York City’s Hospital for Special Surgery in the 1950s, was another innovator who contributed to the early development of modern total hip arthroplasty. He was greatly responsible for certain developments in prosthetic design and also experimented with the use of dental acrylic glue for artificial joint construction. U.S. Patent No. 2,668,531, titled Prosthesis for Hip Joint, was issued in February 1954 by the USPTO. This patent protected a metallic replacement head for a chipped or shattered femur that could be anchored to the femur bone and complete the joint.
Increases to the design complexity for hip replacements would increase with time, as can be seen in U.S. Patent No. 3,656,184, which is titled Artificial Hip Joint. This patent, issued to solo inventor Harold Victor Chambers of Brantford, Ontario, protects a two-part replacement for a patient’s hip joint, providing both a ball-shaped head to the femur bone and the socket created by the pelvis’s acetabulum. This joint was designed to provide better retention of the femur’s ball-head within the socket, preventing dislocation without the use of a retaining ring.
Sir John Charnley and Total Hip Arthroplasty
Beginning in the early 1960s, materials and techniques for hip prostheses would undergo some revolutionary advances, thanks in large part to the low friction arthroplasty procedures developed by Sir John Charnley, the orthopedic surgeon largely considered to be the father of modern total hip replacements. He set out to create a hip replacement that created lower frictional forces after examining one hip replacement patient whose prosthesis created an annoying squeak while walking.
Charnley developed a hip replacement consisting of a metal femoral stem and a polyethylene component for seating the joint in the acetabulum of the pelvis. The replacement method also used acrylic bone cement that had been used in dentistry. The reduced size of the femoral head reduced the amount of wear this device would endure over time, thus addressing one of the major problems involved with hip arthroplasty.
Some of the earlier patents regarding hip arthroplasty and prosthetic devices were issued by the U.S. Patent and Trademark Office by the late 1970s, and Charnley is listed as an inventor on some notable patents. In May 1977, he was issued U.S. Patent No. 4,021,865, titled Femoral Prosthesis. This patent protected a prosthesis for the femur which provided better durability after years of service, especially when the load on the hip was larger due to the patient’s frame. This novel prosthetic design was developed to better support the upper half of the prosthetic joint and reduce stress on the acrylic cement, which could fracture.
John Charnley is also listed as the sole inventor of U.S. Patent No. 4,327,449, entitled Acetabular Prosthesis. Issued by the USPTO in May 1982, this patent protects a prosthetic device for the acetabulum of the pelvis. The adjustments to the anterior and posterior lips of the socket member on the prosthesis were designed to encourage a range of movement beyond a 90 degree angle without contributing to more stress and wear.
Current Developments in Hip Replacement Technology
Even with the significant technological progress of hip replacements throughout the twentieth century, there are still a number of improvements being sought by medical professionals. In July 2012, a surgical team at St. Joseph Hospital in Orange, CA, completed the first total hip replacement of a new procedure utilizing robotics for more precise implantation of replacement devices. The procedure was developed by MAKO Surgical Corporation of Fort Lauderdale, FL, a company with 51 assigned patents according to our most recent database search. An illustrative patent, U.S. Patent No. 8,498,744, titled Surgical Robotic Systems With Manual and Haptic and/or Active Control Modes, protects a surgical robotic system for hip replacement that provides a surgeon with better manual control of the system. Along with hip replacement, this technology could be used in arthroplasty procedures for other joints, including the knees or shoulders.
Other recently patented technologies point out a growing trend in hip arthroplasty: minimally invasive surgery. These surgical techniques, which minimize damage to the soft tissues surrounding the hip joint, help greatly reduce the recovery time and associated hospital stay for patients, even making hip replacement an out patient surgery in some situations if the recipient is a candidate for such an approach. For example, U.S. Patent No. 8,657,824, titled Universal Double Offset Surgical Instrument, protects a smaller device for preparing a femur’s medullary canal for a prosthetic hip installation. This device is capable of performing minimally invasive surgical techniques while requiring less inventory storage space. U.S. Patent No. 8,679,005, entitled Posterior Tissue Retractor for Use in Hip Replacement Surgery, protects a device for the posterior retraction of tissues surrounding the acetabulum which can achieve more stable leverage for surgical procedures. It should be noted that many of these patents, especially this ‘005 patent, have some incredibly elongated claims that would typically denote a narrow patent. However, with so many hip replacement surgeries performed annually in the United States, these technologies are certainly valuable even if the patent claims themselves are quite narrow.
American universities and colleges have also been bastions of medical research in recent decades in a number of fields, as we’ve seen in our recent coverage of academic systems like the University of California. Our search today also turned up one patent in particular that is co-assigned to Stanford University of Palo Alto, CA, and the Department of Veteran Affairs; U.S. Patent No. 8,679,190, titled Hydrogel Arthroplasty Device. This technology may represent a new future for surgical treatment of joint injuries that doesn’t resort to total hip arthroplasty, which usually sacrifices a lot of bone tissue. The arthroplasty device protected by this patent uses an interpenetrating polymer network hydrogel which can mimic the molecular structure and many of the characteristics of natural cartilage. Furthermore, another innovative aspect of the this innovation is seen in the anchoring strategy strategy, which uses a combination of physical, chemical, and biological meansto anchor the device to bone.
In comparison to some of the other patent claims we have seen relative to hip replacement technologies, Claim 1 of the ‘190 patent is relatively short and reads:
An arthroplasty device comprising a bearing region adapted to articulate with another bearing surface and a bone-interfacing region adapted to interact with underlying bone, the bearing region comprising a hydrogel having a first interpenetrating polymer network, the bone-interfacing region comprising another polymer integrated with the first interpenetrating polymer network to form a second interpenetrating polymer network between the hydrogel in the bearing region and the other polymer in the bone-interfacing region, wherein the interpenetrating polymer network hydrogel of the bearing region comprises a first network and a second network, the other polymer in the bone-interfacing region is partially interpenetrated within the first and second networks to form a triple network in the bone-interfacing region.
The ‘190 patent, which issued just several weeks ago on March 25, 2014, is a part of a patent family that dates all the way back to provisional patent application first filed in September 2006. There have been several continuation-in-part applications filed as the technology has continued to develop.
As people increasingly live longer lives, and as medical technology advances, hip replacement surgery, which enjoys over a 95% success rate, is here to stay. Although hip replacement surgery is overwhelmingly a success, materials break down, which will be an increasing issue as we live longer lives, outliving the usefulness of the new hips we have been given. Thus, we can expect to see ever more innovation in this field over the years to come. Already there is research into growing a new hip of natural bone, as is research into materials of greater and greater hardness.
Even companies like Intel are have their eyes and ears open when it comes to implanted medical devices. While Intel is best known as a leading manufacturer of computer chips, U.S. Patent No. 8551555, entitled Biocompatible Coatings for Medical Devices protects a method of providing implanted medical devices (including hip replacements) with a more uniform biocompatible coating for a lower risk of infection.
Given the overall success rate, an ever aging population and a need for the replacement of spent joints, when discussing hip replacement procedures one thing seems certain — they are not going away anytime soon. That guarantees that innovation in this space will only continue to flourish.