Nearly one year 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 normally and continue to strengthen my leg muscles. With this personal anniversary, 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 300 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 hip replacement surgery really dates 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.
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.
Other, more 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. 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.
Given the overall success rate, an ever-aging population, and a need for the replacement of spent joints, one thing seems certain — hip replacements are not going away anytime soon. That guarantees that innovation in this space will continue to flourish.
Tags: hip, medical devices, patent, patents, prosthetic devices
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