By: 5 August 2014
People who are severely overweight need joint replacement twice as often and face double the risk of complications


The obesity epidemic has arrived in orthopaedics: Anyone who gets a hip or knee replacement today is very likely to be overweight, according to experts at the EFORT Congress. The situation presents a major challenge for orthopaedic surgery and new studies show that anyone hitting the scales with too many kilos is at higher risk of complications.

More kilos weighing on first knee prostheses
People who need their first knee replacement these days tend to be heavier than candidates for prosthetics in past decades, according to a Scottish long-term study. The study compared 686 patients who underwent primary total knee arthroplasty between December 1994 and August 1998 with 1,408 patients who underwent such surgery between January 2009 and November 2012. “The patients in the second group had an average BMI of 32.0 kg/m2, significantly higher than patients in the first group who weighed in at 29.4 kg/m2 on average,” study author Dr Ewan Barclay Goudie (Victoria Hospital, Kirkcaldy) reported at the EFORT Congress.

Risks increase beyond a BMI of 35
A new Swiss study shows when an increased body mass index (BMI) becomes problematic. “Obese people with a BMI of 35kg/m2 and more are particular risk candidates for reoperations and infections. As compared to patients with BMIs below this value, they needed double the number of revisions and suffered deep infections twice as often. The effect was higher in men than in women,” said Dr Matthieu Zingg from the University Hospital in Geneva. Data from nearly 2,500 patients with knee prosthetics were analysed for the study.

Obese people need twice as many knee replacements
The need for prostheses increases along with the kilos, a recent Northern Ireland study shows. “Compared to the Northern Irish population, obese men face double the risk of eventually needing an artificial knee joint. With obese women, the risk is 2.4 times as high. Effective programs for preventing obesity are needed to respond to these alarming figures in order to dampen the enormous demand for arthroplasty and the resulting drastic costs to the healthcare system,” said Dr Christopher O’Neill (Musgrave Park Hospital, Belfast). The BMI of 1,000 people needing total knee replacement was measured for the study. More than 90% of study participants were overweight or obese, whereas 59% of Northern Ireland’s general population are so evaluated. Among the study participants, 28.5% had a BMI of 25.0 – 29.9 kg/m2 (overweight) and nearly 62% were obese (BMI > 30.0 kg/m2). Women on average were in worse shape than men.

New surgical technique for obese patients
In the future, orthopaedic surgeons should apply customised patient-specific guides for adapting knee prostheses in obese patients, adjusting the size of components, axis position and rotation according to usual surgical principles, Australian surgeon Prof Warwick Bruce and British surgeon Dr Rahij Anwar recommended at the EFORT Congress. “Patient-specific guides are a great technological improvement compared to conventional methods of total knee arthroplasty. They increase precision, reduce blood loss and surgical time and also help to properly measure the size of implants in patients with a large BMI. Additionally, the mechanical axis can be reliably restored using patient-specific guides,” Dr Anwar said. They have tested the new method in Sydney with an international research team in 47 cases. Performing total knee replacement in obese people is tricky. Anatomic assessment becomes more difficult and the large soft-tissue volume may impede the proper application of standard guides.


EFORT Abstract Goudie et al: Are They Getting Fatter? Changing Trends In Total Knee Arthroplasty; EFORT Abstract O’Neill et al: The Effect Of BMI On Requirements For TKA Within The Northern Ireland Population; EFORT Abstract Zingg et al: Influence Of Obesity On Revision And Infection Rates After Primary Total Knee Arthroplasty; EFORT Abstract Anwar et al.: Total Knee Arthroplasty Using Patient Specific Guides In Patients With A Body Mass Index Of 35 And Above: Our Experience In 47 Knees.