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Pioneer surgeon drove ultra clean technology

1 May 2013

On the 50th anniversary of the development of his ground-breaking hip replacement surgical technique, Amanda Parkin, communications consultant with clean air technology specialist, Howorth Air Technology, examines Professor Sir John Charnley’s influence on orthopaedic surgery, and explains how his realisation that any subsequent infection may not appear until long after the operation, and that keeping bacteria away from the wound during the procedure is the the key to minimising the risk, led to the emergence of ‘ultra clean’ operating theatre technology – within which Howorth was an early pioneer.

Since its introduction in the 1960s, total hip replacement surgery has proved one of the most effective procedures in modern medical history – a true landmark in 20th century surgery. What was once a rare and risky operation has now become one of the world’s most performed elective surgical procedures, with over 70,000 people each year in the UK alone getting a new hip, and a new lease of life as a result. November 2012 marked the 50th anniversary of the development of the technique which revolutionised hip replacement surgery – a technique which has basically remained unchanged since then, and forms the basis for all modern hip implants. It was developed by a British surgeon – Professor Sir John Charnley, while he was working at Wrightington Hospital in Lancashire, a hospital which today remains a Mecca for orthopaedic surgeons.


Wrightington Hospital and the hip implant

By the early 1950s, Professor Charnley was a very successful Manchester-based consultant, who already had a reputation for ground-breaking work in the field of trauma and fractures. One day, he saw a patient suffering from a rather embarrassing problem with his existing hip implant – every time he reached forward to get the salt at mealtimes, it squeaked, and his wife said it made her feel sick. This inspired Professor Charnley to start thinking about what was going on at the joint, and how both the new joint, and the process of replacement,


In 1958, he decided to put all his efforts into the development of hip replacement research and surgery. He moved to Wrightington Hospital, Lancashire, where he established a hip surgery centre. On arrival, his first action was to build a biomechanical laboratory that could be used to test the implants for wear, and develop the instruments to perform the operation. This resulted in the ‘seven tray system’ of instruments – one tray for each stage of the procedure. On 26 March 1959 he delivered a lecture where his views on hip surgery were clearly expressed. He said to those assembled:


“In a speciality as vast as that of orthopaedics, surgeons yearn for an easy hip operation, or, if a good operation is difficult, they hope that, having mastered its performance through trial and tribulation, it should be universally applicable.”


Self-taught engineer

Professor Charnley was a self-taught engineer, as well as a surgeon. One of his most important discoveries early on was that the realisation that low friction between the ball and socket of the hip implant was vital, as it would allow easier and more successful movement, which led him to design his own implant. After several failures, he produced a two-component joint made of metal and plastic. The metal part was placed in the femur, which was hollowed out during surgery, and the plastic component cemented into the pelvis – to create a joint that worked in a similar way to a natural one. Vitally, he also developed the surgical procedure to go with it, thus creating the total hip replacement.


He also believed it was vital to obtain artificial joints from patients who had died some years after the surgery, to study the degree of wear and tear on the joints, and thus improve materials. He asked all patients if he could have the hips back when they died, and, when the time came, would send round what became known as ‘the black box squad’ to collect the hips and lymph nodes to correlate the facts, and see how the joints had worked during the years they had been in the body.


Worldwide interest

As his invention proved more and more successful, he started to attract surgeons from all over the world to Wrightington to learn about his unique approach. Only when the Professor was satisfied that surgeons under his tutelage could perform the procedure on their own, to his exacting standards, did he issue them with a letter allowing them to obtain the instruments – supplied by Leeds-based manufacturer, CF Thackrays – necessary to perform the surgery. To this day, the Wrightington Hospital remains at the forefront of this field, and performs more hip replacement surgery than any other single hospital site in the UK.


Howorth and ‘the greenhouse’

The insertion into the tissues of a large mass of foreign material, as occurs during a hip replacement, carries a high risk of infection at the site of the operation. Professor Charnley found, however, that infection may not appear until long after the operation, and, in about half the cases, the organisms were of a kind which were commonly found on the skin, but rarely gave rise to wound infection after other types of operation.


This led him to start researching methods to keep bacteria away from the wound during surgery. He tried using antibiotics prophylactically, but by the 1970s had stopped using them as routine altogether. He decided it would be necessary to develop ‘clean air’ operating conditions, and also to isolate the open wound bacteriologically from the theatre staff. On December 10, 1961, he approached Hugh Howorth, whose family firm, then called Howorth Air Engineering and then, as now, based near the hospital in Bolton, had been making filtered air systems for more than a hundred years. Professor Charnley explained that he wanted a clean air system, free from contaminants, for his hip replacement operations. Hugh Howorth replied that creating such a system should be well within his capabilities, since he was used to designing bacterial elimination systems for brewery fermenting rooms, where it was necessary to ensure that unfermented yeast avoided contamination.


The ‘piston effect’

Working together using the knowledge that existed at the time, Hugh Howorth and Professor Charnley attempted to perfect the ‘piston effect’ of a downward flow of air. Instead of using the whole of the operating room ceiling, they restricted it to a much smaller area, and hence improved the downward flow of air. They used a 7 ft x 7 ft ‘greenhouse’ placed within the operating theatre, within which the surgical team would work. The ‘greenhouse’ also had to be portable, as the theatre was still being used for general surgery at this time. Professor Charnley and Hugh Howorth combined their medical and engineering knowledge and succeeded in creating the world’s first successful clean air operating enclosure, something that was to revolutionise the way that orthopaedic surgery was carried out, and ensure that many more people lived to enjoy the new lease of life that their hip replacement gave them.


The pair also designed a ‘total body exhaust system’ for the surgeon and his team, comprising a helmet-like mask, and a gown of ventile material, from which air was removed by suction through narrowbore plastic tubing.


In addition, Professor Charnley designed the operating table and a double bank of lights for use in the enclosure, and had an X-ray tube sunk directly into the floor underneath the table, in line with the patient’s pelvis, to avoid having to move the patient into another area for X-rays. He also designed the surgical instruments, and pioneered a new way of laying them out for different stages of the operation on seven different trays, to minimise the risk of contamination. The whole system was extremely successful, and reduced the postoperative infection rate from 9% to under 1%, as shown in Figure 1.


Global impact

Other surgeons and hospitals soon realised the benefits of ‘ultra-clean’ surgery, and wanted their own version of the Wrightington ‘greenhouse’. Its influence was global – a few years down the line, a colleague of Professor Charnley’s, Henry Hamilton, would take the principle of the greenhouse, re-design it, and use it at Vietnam’s Phan-rang Hospital to treat troops during the Vietnam War.


The modern ultra clean ventilation system, of which the Wrightington greenhouse was the forerunner, supplies HEPA-filtered (HI4 99.997%) and conditioned air over the wound site, and returns the air at low or high level through G4 pre-filters. The canopy recirculates air via integrally mounted or remotely sited recirculation fans, and the traditional glazed ‘discipline’ panels prevent entrainment of dirty air into the operating field. The air is recirculated 500 times over the operating field, reducing the number of colony forming units (CFUs), i.e. those particles of 0.5 microns or greater that support bacterial growth, to less than 10 per m3 – equivalent to a Grade B cleanroom environment.


Ultra-clean surgery is now considered the norm for orthopaedic operations, and is increasingly being used for other operations where there may be a risk of infection from airborne organisms.


Professor Charnley’s legacy

Since Professor Charnley’s work in the 1960s, total hip replacement surgery has played an important role in alleviating pain and restoring mobility to millions of arthritis sufferers. It quickly became a flagship operation, raising the status of British orthopaedic surgery. Its development was a result of innovation in materials, instruments, and operative procedures, many of which have since been adapted to treat other joints, and applied across a range of surgical specialities. Professor Charnley also devised a revolutionary method of teaching, described in detail in his book, ‘Low Friction Arthroplasty of the Hip’, which has been used to train surgeons from all over the world, many of whom travel to Wrightington specifically to learn the technique he pioneered.


Anil Gambhir, a consultant at Wrightington, says: “As an orthopaedic surgeon, I am bound to be biased; I am bound to tell you that hip replacement is the number one innovation, but I don’t think I am far wrong. It certainly ranks alongside the discovery of penicillin, coronary artery bypass grafting, and coronary stenting. Above all, however, it has had a huge impact on patients’ lives around the world, delivering pain relief, and a return to function.”


In 1974, Professor Charnley was presented with the Lasker Award (usually the precursor to the Nobel Prize), and in 1975 he was awarded the Lister Medal for his contributions to surgical science, while 1977 saw him knighted. He died in Manchester in 1982. In May 2008 he was invested into the American Inventors Hall of Fame. To this day, Wrightington Hospital holds the status of Centre of Excellence (Orthopaedic Surgery), and credits the seminal work undertaken there by Professor Sir John Charnley on the opening page of its website.


A ‘greenhouse for the 21st century’

As operating theatres become ever more high-tech, featuring integrated digital technology that requires monitors and touchscreens within the operating site clean zone, as well as integrated scanners, X-rays, and microscopes, space, particularly at ceiling level, is at an everincreasing premium. A 21st-century operating theatre needs to allow for flexibility of equipment choice and changing work practices, as well as looking streamlined and almost futuristic in design.


In response to this, Howorth Air Technology, as Howorth Air Engineering became, developed a new Screenless Ultra Clean Canopy, the Exflow Evolution (HEJ – August and November 2012), to complement the range of Exflows it has been installing in private and public hospitals around the world for over 40 years. In keeping with the company’s innovative approach to design, Howorth chose to follow a different path to competitors, and developed its own unique system, which is suitable for both retrofits and new builds. The Evolution has recently been installed at Southmead Hospital in Bristol, which now has 16 new operating theatres with screenless canopies.


Improved performance

The Evolution essentially retains the basic construction of Howorth’s highly successful existing models, the Exflow 28 and Exflow 32, but, with some innovative engineering at the air discharge, the company has recreated, and in many ways improved, the performance of the systems, without the need for the traditional partial walls or the additional requirement of low level recirculation ducts, remote fans, or cooling coils, that many other models require. The unit remains an integral fan unit of modular construction, ideal for new build or retrofit situations. Installation time is kept to an absolute minimum, and, as primary airflow to the theatre remains the same as with other Exflow models, longterm maintenance and running costs can be lower than competitive products.


At the core of this new product are the patented Passive Coanda and Active Coanda systems. These are unassisted (Passive) or assisted (Active) air displacement devices, designed to replicate the controlled airflow of a solid side screen. Both the Evolution models, designated the Exflow 28-12 and Exflow 32-12, exceed the performance requirements of HTM 03-01 in many areas, particularly with regard to the non-entrainment test.


Backed by the Howorth’s 150 years of experience in engineering clean air, the new Exflow Evolution takes operating theatre design into the 21st century and beyond, but always remains true to Professor Charnley’s vision.


The original article can be found on the Health State Journal’s website by Clicking Here