Obesity Is Associated with a Greater Risk of Complications after Shoulder Arthroplasty
For patients undergoing shoulder arthroplasty, higher body mass index is linked to increased complications, including the need for revision procedures, according to a study from Mayo Clinic published in The Journal of Bone & Joint Surgery.
“Increasing BMI is strongly associated with increased rates of revision surgical procedures and postoperative complications after shoulder arthroplasty,” the researchers write. Their findings suggest that, above a certain level of obesity, complication risk increases steadily along with increasing body mass index (BMI).
The study included data on 4,567 shoulder arthroplasties performed between 1970 and 2013.
Forty-three percent of the shoulder arthroplasty patients were obese (defined as a BMI of 30 or higher). The researchers analyzed the relationship between BMI and different types of complications following surgery.
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.
Obese patients were at increased risk of both types of reoperation. Among patients with a BMI of 35 or higher, each additional 1-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 1-unit increase in BMI after 30, there was a 5% increased risk of revision for mechanical failure.
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 1-unit increase in BMI.
In this population of shoulder arthroplasty patients, obesity was not a risk factor for thromboembolism, as it is for patients undergoing hip or knee replacement.
The rising prevalence of obesity – now present in more than one-third of US adults – has had a major impact on healthcare and related costs. Obese patients are at increased risk of several types of complications after total hip or knee replacement surgery. The new study is among the first to assess how BMI affects the risk of complications after shoulder arthroplasty. This study is also unique in that it analyzes BMI in 1-unit increments, rather than in ranges.
The results suggest that the risk of revision surgery and most other complications of shoulder arthroplasty increases along with BMI in obese patients. “These findings support the notion that increasing BMI increases the stress on the implant, leading to higher rates of mechanical implant failure,” the researchers write. They add that the increased infection risk is likely related to immune system changes and to “dead space” created by excess fatty tissue.
The researchers believe their findings will help patients, physicians, and surgeons make better-informed decisions about the relative risks and benefits of shoulder arthroplasty at different levels of BMI.
They discuss the implications of their findings for policy and research, including the need for further studies to modify the risks associated with increased BMI and studies helping to support the risk stratification for reimbursement, providing financial incentives for surgeons treating more complex and high-risk patients.
Wagner ER, Houdek MT, Schleck C, et al. Increasing body mass index is associated with worse outcomes after shoulder arthroplasty. J Bone Joint Surg Am. 2017 Jun 7;99(11):929-937. doi: 10.2106/JBJS.15.00255.