A total hip replacement is a surgical procedure that entails removing a damaged or diseased hip joint and replacing it with an artificial hip, called a prosthesis. This type of surgery is normally performed to relieve pain and loss of mobility caused by a range of conditions, including: osteoarthritis, which damages the cartilage that enables the joint to move smoothly; rheumatoid arthritis, which is an autoimmune disease that can cause joint damage; or serious hip fractures.
Risk of post-surgical complications
Every year in the UK around 100,000 hip replacements take place, a figure that is rising all the time. However, while hip replacement surgery is routine and generally a safe and highly effective procedure, like all surgery it carries a risk of complications. After surgery, there is a small risk of developing an infection in the wound site or within the prosthesis itself. There is a chance of developing blood clots in the leg veins, which can be dangerous if they travel to vital organs such as the lung, heart or brain. Other possible complications include dislocation of the hip, fractures of healthy sections of the hip joint, nerve damage or loosening of the implant over time.
BMI research
Obesity is one factor that can increase the risk of developing complications after a total hip replacement. A research team from the Keck School of Medicine at the University of Southern California set out to explore the link between body mass index (BMI) and the risk of early post-operative complications, including periprosthetic joint infection (PJI), composite surgical and composite medical complications.
What they did
The team used the Premier Healthcare Database to identify primary elective total hip replacements performed between 1 October 2015 and 31 December 2021 that had been followed by a diagnosis of PJI within 90 days of surgery. They focused on BMI as a continuous variable, using logistic regression to develop restricted cubic splines as a way of determining the impact of BMI on the PJI risk. Bootstrap simulation was used to identify the inflection point in the final model.
The findings
The team found there was an increased risk of periprosthetic joint infection beyond a BMI of 37.4 kg/m 2, and this increased exponentially. Relative to this threshold, patients with a BMI of 40 or 50 kg/m 2 had a 1.22 to 2.55 times greater risk of developing PJI.
The researchers also considered the risk of surgical complications, which were found to increase at a BMI of 32 kg/m 2, and medical complications, which increased at a BMI of 39 kg/m 2. Patients with a BMI of 50 kg/m 2 were at a 1.36 to 2.07 times higher risk of developing medical and surgical complications, respectively.
The study, which was published in the Bone & Joint Journal, concludes that there is a relationship between a patient’s BMI and their risk of early post-operative infection in the prosthesis, as well as composite medical and surgical complications.
Losing weight prior to surgery
For this reason, if you are due to undergo a total hip replacement and you have a high BMI, your orthopaedic surgeon will advise you to lose weight. Prior to surgery, even a 5% reduction in your body weight will help to reduce joint pain and improve mobility because it lessens the amount of stress placed on the joint when you stand, walk or move.
If you need advice on losing weight safely, your surgical team will be happy to advise you. Ideally, a combination of healthy eating and gentle exercise will help you both to reduce your BMI and improve flexibility and movement within the affected joints. A physiotherapist will be able to recommend some simple stretching and strengthening exercises and you may wish to combine these with a low-impact activity such as walking or swimming.
Contact us for more information about managing joint pain and the range of surgical treatment options available, including total hip replacement.
