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Get your power tools prepared! The transformative scientific advancements behind hip and knee replacements.

Get your power tools prepared! The transformative scientific advancements behind hip and knee replacements.


Doncaster is in surprisingly good spirits despite the fact that he is about to undergo a major surgical procedure. He jokes, “I have a busy life, so it’s nice to have a break.” It is 8:30am on a cold December morning and he is at Warwick Hospital, preparing to receive a partial knee replacement.

Doncaster, who is currently 62 years old, has always been a active person. In his youth, he played rugby but had to give it up due to a knee injury. He then picked up other sports to stay active. However, his knee is now causing issues once again. As a self-employed chartered engineer, he needs to have the ability to climb up and down tower blocks. Even something as simple as going on a hike with his wife seems like a distant dream. Doncaster believes that his knee problems will only worsen in the future.

Doncaster is undergoing a patellofemoral replacement, a form of partial knee replacement. This involves removing the damaged cartilage on the femur and underside of the kneecap and replacing it with implants.

Before undergoing surgery, he appears to have familiarized himself with the process through watching videos on YouTube. He remarks, “It’s a harsh procedure. They literally slice the knee in half and tear it apart. Orthopedic surgery is essentially like carpentry, isn’t it?” Doncaster’s observation is accurate – the instruments used for joint replacements are similar to those found in a woodshop.

Doncaster is prepared for surgery by putting on a medical gown and receiving anaesthesia in his spine. He is then taken into the operating room where his leg is quickly wrapped with a yellow antibacterial covering. A blue cloth is placed in front of his chest as he continues to talk.

A group of approximately six nurses wearing blue scrubs and masks are prepared for their duties. While it is a significant day for Doncaster, it is a usual morning for the team. These procedures usually take a little over an hour to complete. The nurses confirm the correct patient and procedure and make sure all necessary tools, ranging from heavy-duty power tools to fragile scalpels, are ready for use. They stand in a calm but alert manner, ready to hand over instruments, collect soiled swabs, or dispose of any extra bone cement.

In the room, a radio can be heard playing Dusty Springfield while Mohammad Faisal, the consultant orthopaedic surgeon, takes a scalpel and makes an incision into Doncaster’s knee. The tissue is moved to the sides and Faisal proceeds to dissect the muscle, revealing the bone. Upon tapping the knee, he determines that the cartilage between the kneecap and femur has deteriorated. He turns over Doncaster’s kneecap and uses a power drill to secure a jig and cutting guide to the femur. Then, he grabs a power saw and removes the top of the femur, causing bone fragments to scatter around.

Faisal prepares another guide and then proceeds to collect a sample implant, along with a hammer and a rod-shaped tool. He uses the rod to strike the implant with significant force.

Tools used in knee operations

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Based on information from the NJR, which encompasses regions such as England, Wales, Northern Ireland, the Isle of Man, and Guernsey, there were a total of 99,043 initial surgeries for hip replacements and 98,469 initial surgeries for knee replacements in 2022, including partial replacements. “Primary” refers to the first instance of joint replacement for the patient.

The rate of prevalence is at its peak among individuals in their mid to late-70s. According to data from NHS England for the year 2021/22, the rate of hip replacements for women aged 75 to 79 was 621.8 per 100,000; and for knee replacements, including partial ones, it was 649.2 per 100,000. For men in the same age group, the rates were 420.6 and 587.7 per 100,000 respectively. However, these surgeries are no longer limited to older individuals.

According to Faisal, the frequency of hip and knee replacements is increasing as they are being performed at an earlier stage.

Implants now have a longer lifespan and the surgical methods used have improved, resulting in reduced risks. Additionally, these procedures are often performed using spinal anesthesia rather than general anesthesia, further decreasing potential complications. These advancements have also led to a higher frequency of subsequent or revised replacements.

According to NJR statistics, individuals are gaining weight with an average BMI of 28.7 for hip-replacement patients, indicating overweight, and 30.7 for knee replacement patients, which is considered obese.

Faisal warns that being overweight can lead to faster wear and tear on your joints. Many people only realize this when they start experiencing issues.

Hip and knee replacements have been in existence since the end of the 1800s. The initial procedures were performed by Prof Themistocles Gluck in Germany, who implanted ivory in individuals with tuberculous joints. In the early 1900s, artificial materials like glass, acrylic, and metal alloys were introduced. However, there were inconsistent results, including issues with infections, broken glass, and the wearing and loosening of implants.

During the 1960s, a British surgeon specializing in orthopedics named John Charnley transformed the field with his innovations in hip replacement surgery. Charnley not only created a more efficient and durable hip replacement, but also pioneered the surgical technique for the procedure. This approach proved to be highly effective and has since become a standard practice in the medical community. As the saying goes, the rest is history.

Faisal, under the bright lights of the theater, prepares to perform a hip replacement surgery on his second patient, 78-year-old Lesley Gisbourne. As the retractors hold open a large incision, the light reveals the pristine ball and socket joint that has remained hidden until now.

Faisal quickly grabs the electric saw and removes the top of Gisbourne’s femur in a flash. The piece, roughly the size of a plum, sits in Faisal’s hand and gleams like a massive marble. He then proceeds to use power tools, including a large drill with a formidable attachment, to extract tissue from the joint socket and a hammer to insert new components.

The contrast between the rough, heavy process and the precise abilities, expertise, and nimbleness necessary to perform it is surprising. However, as Faisal takes hold of the fresh ball for the joint – a sleek, glossy, silver orb – there is a feeling of optimism. Because when Gisbourne awakens, she will finally have the opportunity to walk without discomfort.

The widespread use of joint replacements may not fully reflect the significant impact they have on patients. Although they are a routine procedure for the healthcare system, they can be life-changing for those who undergo them. According to data from NHS England, 93% of individuals who received hip replacements rated their results as excellent, very good, or good. Faisal explains that these replacements are often referred to as “forgotten hips” because patients are able to resume their normal activities after just one year. Satisfaction rates for knee replacements are slightly lower due to the complexity of the joint and the difficulty in replicating its movements with implants. However, 87% of patients still report positive outcomes.

However, there is potential for enhancement. Scientists have been working on creating materials that have a slower rate of wear and are still compatible with the body. According to Faisal, the latter is extremely important. “In laboratory settings, metal-on-metal hip replacements were considered to be the most durable option,” he explains. “But when used in the body, the shedding of metal caused a negative reaction.” This ultimately led to a controversy in the medical field.

According to Professor Richard M Hall from the University of Birmingham, a specialist in medical engineering, the use of new materials like highly cross-linked polyethylene has greatly improved the durability of implants. This is especially important as patients are now living longer and requiring replacements at an earlier age. Recent data shows that the wear and tear in implants made with these materials is minimal even after 15 years since the procedure.

Surgical power tools waiting to be used.View image in fullscreen

Dr. Edgars Kelmers from the University of Leeds and other researchers have been developing “smart joints” that are equipped with various sensors. According to Kelmers, these joints could provide valuable data on the pressure and tension within the joints. He believes that this data is crucial for understanding the performance of implants and making improvements in the future.

These hi-tech implants might bring other benefits, too: temperature sensors could give early warning of an infection, while movement sensors could give patients confidence to exercise and feel safe in the knowledge that any problems would be quickly detected. The Persona IQ smart knee from Zimmer Biomet can collect data on step count, walking speed and rate, distance travelled, stride length and knee movement.

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New technologies, such as robotics and navigation, have the potential to improve the precision and balance of knee and hip replacements. According to Chethan Jayadev, a knee surgeon at the Royal National Orthopaedic Hospital in Stanmore, these advancements may lead to more accurate placement of components during the procedure.

Although knee and hip replacements are expected to continue being a significant part of the NHS’s responsibilities, specialists are also discovering methods to prevent them and maintain or regenerate problematic joints. This can include procedures like cartilage transplants or stem-cell therapies. The former may involve placing cartilage cells or sections into the affected area, while the latter typically involves extracting stem cells from the patient and transferring them to the damaged joint.

Mark Campbell, a professor at the University of Ottawa, highlights that there has been skepticism towards stem-cell techniques due to a lack of proof of their effectiveness. He states, however, that we still have a ways to go before stem-cell therapy for regenerating joint cartilage is widely accepted by medical organizations and backed by solid evidence.

These issues have caused multiple government regulatory agencies to stop utilizing stem-cell therapy for joints until there is more solid evidence.

Jayadev acknowledges that there is limited evidence to support the use of cell-based methods for repairing cartilage, but he mentions that certain types of cartilage cell transplants and procedures involving healthy cartilage plugs have proven to be reliable. However, these treatments are not effective for treating degenerated joints.

Jayadev compares the condition of cartilage to a road, stating that for some individuals, their cartilage is mostly intact with only a small area damaged, similar to potholes on a road. In these cases, regenerative procedures like cartilage repair or stem-cell transplantation are highly successful. If these methods do not work, there is also the option of using small metal or cross-linked polyethylene implants for localized repairs.

Regrettably, when individuals finally consult a surgeon for their joint discomfort, the road has already been extensively damaged. In simpler terms, significant portions of cartilage have deteriorated and osteoarthritis has developed. According to Jayadev, this indicates that the joint may have additional issues that cannot be remedied through regenerative surgeries.

According to Jayadev, joints play a vital role in movement and can be compared to other organs like the kidney or liver. Just like these organs, joints are also susceptible to failure, which is known as osteoarthritis.

In summary, joints affected by osteoarthritis have an atypical communication environment. According to Jayadev, proper signals are necessary for stem cells and cartilage cells to transform into healthy, normal material.

For the majority of patients, there are two choices. According to Jayadev, “You can either avoid using the road, or you can rebuild the road.” The first option involves making changes to activities, using braces, or undergoing surgeries to fix the alignment of the joint and lessen the pressure it endures. The second option involves replacing the joint entirely.

The issue is that individuals in the initial phases of osteoarthritis may not require surgery, but have few options aside from weight loss, physiotherapy, and temporary pain relief injections. This results in what Jayadev refers to as the “treatment gap.” He emphasizes the need for focused efforts to address this gap and find effective solutions for these patients.

Patients not only encounter one obstacle, but also have to deal with long waiting lists when they become eligible for a replacement procedure.

Ian Doncaster before his knee surgery at Warwick hospital.View image in fullscreen

In August, Doncaster made the decision to proceed with surgery. He was given a November date, but had to change it due to a holiday. Currently, Warwick hospital has a Vanguard mobile operating theatre and a specialized team of physiotherapists and nurses who follow up with patients at home after the procedure. This has increased their ability to perform these surgeries and quickly release patients.

Unfortunately, knee and hip-replacement patients in the NHS are experiencing longer waiting times for their procedures. This is due to a decrease in surgeries during the pandemic and cancellations caused by doctors’ strikes, resulting in a backlog.

The West Suffolk NHS Foundation Trust’s website, which is one of the few to openly display its waiting times, states that the average wait for a hip or knee replacement is currently 57 or 59 weeks. This goes against the NHS constitution, which guarantees patients the right to receive this surgery within 18 weeks.

However, the wait may prove worthwhile. Patients like Gisbourne have a promising future with a new hip that could potentially alleviate her pain once and for all.

Faisal smiles, feeling painless and vibrant.

Source: theguardian.com