A study published recently in The Journal of Bone & Joint Surgery links an increased complication rate—including the need for a “revision” procedure—among people with a high body mass index (BMI) who undergo shoulder joint replacement surgery.

“Increasing BMI is strongly associated with increased rates of revision surgical procedures and postoperative complications after shoulder arthroplasty,” according Eric R. Wagner, MD, and colleagues at the Mayo Clinic, Rochester, Minn. In addition, they suggest, above a certain level of obesity, complication risk increases steadily along with increasing BMI.

The team looked at data from 4,567 patients who underwent shoulder arthroplasty surgery between 1970 and 2013. Among the patients, 43% were obese (defined as having a BMI of 30 or higher).

The tem then analyzed the relationship between the patients’ BMI and the different types of complications that occurred. Overall, 302 patients needed revision surgery due to mechanical failure, loosening of the implant, or other causes. An additional 62 cases required a non-revision reoperation, according to a media release from Wolters Kluwer Health.

Obese patients were at increased risk of both types of reoperation. Among patients with a BMI of 35 or higher, each additional one-unit increase in BMI was associated with a 5% increase in the risk of reoperation for any reason.

Higher BMI was also specifically associated with revision surgery for mechanical failure. For every one-unit increase in BMI after 30, there was a 5% increased risk of revision for mechanical failure, the release continues.

The BMI-related increases in complications remained significant after statistical adjustment for other factors. The strongest association was for superficial wound infection: risk increased by 9% for each one-unit increase in BMI. Among these patients, obesity was not a risk factor for blood clot-related complications (thromboembolism), as it is for patients undergoing hip or knee replacement, per the release.

“These findings support the notion that increasing BMI increases the stress on the implant, leading to higher rates of mechanical implant failure,” Wagner and coauthors write. The increased infection risk is likely related to immune system changes and to “dead space” created by excess fatty tissue, they add.

[Source(s): Wolters Kluwer Health, Science Daily]