Joint replacement surgeries—hip, knee and shoulder replacements in particular—can significantly improve quality of life but many obese patients are denied these procedures due to health risk concerns.

There are no formal recommendations on joint replacement surgeries for obese patients, and evidence about the risks involved for this cohort is limited and mixed at best.

A PLOS Medicine study found that shoulder replacement surgery is safe and effective in obese patients and access to the procedure should not be restricted based on body mass index (BMI) alone. “The ‘obesity paradox’ has previously been identified in hip and knee replacements, where obesity appears to be associated with reduced early mortality after surgery. However, the association of high BMI with reduced mortality demonstrated in our study on shoulder replacements is even greater than that identified for hips and knees,” the study authors concluded.

Researchers analyzed more than 20,000 elective shoulder replacement surgeries performed in the United Kingdom and Denmark to see whether BMI was associated with death or other complications. Compared to patients with a healthy BMI (21.75 kg/m2), patients with obesity (BMI 40 kg/m2) had a 60% lower risk of death within the year following surgery. Those considered underweight however, (BMI <18.5 kg/m2) had an 18% higher risk of death, in addition to an increased risk of other poor outcomes.

“Clinicians and hospitals should be aware that underweight patients appear more at risk of mortality, serious adverse events and revision surgery after shoulder replacement,” the study authors said.

One of the study’s main limitations was the small sample size of the underweight population (131 for the U.K. data, 70 for the Denmark data). However, this was a large study that consistently showed a lower risk of death in patients with obesity undergoing shoulder replacement surgery across multiple outcomes and two countries. The results can help patients, surgeons, and policymakers make informed decisions about the types of patients that should be considered fit for these surgeries, the study claims.

“Shoulder replacements offer patients the opportunity for excellent pain relief and improved quality of life,” lead study author Epaminondas Markos Valsamis noted. “Our research shows that patients with a higher BMI do not have poorer outcomes after shoulder replacement surgery.”

“While BMI thresholds have been used to limit access to joint replacement surgery, our findings do not support restricting higher BMI patients from accessing shoulder replacement surgery,” senior study author and professor Jonathan Rees added.

The research was supported by the NIHR Oxford Biomedical Research Centre (BRC) and Aarhus University.