09 Sep 2014
Research has been undertaken at Anglia Ruskin University since the mid-1990s to address inadequate surgical guidelines on implant fixation in total hip replacement (THR) operations. Our research started with an investigation into the biomechanical integrity of the ‘cement-within-cement’ reconstructed joint revision technique. We found that a thin layer of blood and marrow debris at the interface weakened the bond by 80%. This finding was used to raise surgeons’ awareness of the need to remove all old cement if the entire interface could not be reliably cleared of blood and marrow fat during revision.
In 1998 we went on to conduct a survey of practice amongst nearly 500 orthopaedic surgeons in the UK, which revealed wide variations in surgical techniques used in THR. We studied the effects of these varied surgical techniques on the long-term stability of THRs, with the aim of improving patient outcomes. Our research activities were clinically led; we worked closely with orthopaedic clinicians from the Mid Essex Health Trust, Broomfield Hospital and Ramsay Springfield Hospital.
As a result of our research, orthopaedic surgeons can make better-informed decisions on treatment methods and have changed the way in which they carry out THRs. For example, fewer and larger anchorage holes are drilled perpendicularly to the hip socket to reduce stress and implant failure. The subchondral bone is preserved to maintain good load distribution in the hip socket and cement mantle thickness is selected according to patient bone quality and size. Also, the cement-to-cement interface is thoroughly cleaned during revision surgery to maintain mechanical integrity. These techniques increase implant longevity and can delay or avoid the need for revision surgery.
Our research has been welcomed by surgeons. For example, a Consultant Orthopaedic Surgeon at MEHT (Broomfield Hospital) testified: “...I have used the techniques that were seen to be effective from the research you did concerning the shape, number of key holes and cement mantle thickness in cemented total hip replacements since 2000, with excellent results. I think that the use of these techniques would reduce the need for revision hip surgery by 50%.” Another believes that our recommended surgical fixation technique has resulted in a reduced length of stay in hospital by 4 days for each THR operation as well as reduced patient recovery time, while THR patient satisfaction has remained at 98%. The savings associated with length of stay in hospital alone (£300/day) are estimated to be £696,600 between 2008 and 2013. Further savings are associated with the lower unit cost of a cemented polyurethane cup compared to the alternatives, resulting in a saving of £1,000-£1,300 per operation.
In addition, Broomfield Hospital has recently been highly rated nationally for total hip replacements, with the best patient-recorded outcome among more than 200 English NHS hospitals.
Dr Rajshree Mootanah, Director of the Medical Engineering Research Group at Anglia Ruskin University