For restoring function and reducing pain, total hip replacement surgery is one of the most successful, cost-effective and safest options available – yet surgery-related complications do occur. A new study published recently in the journal BMJ has found that patients whose surgeons perform more than 35 total hip replacements (THR) per year – roughly three or more per month – have fewer complications compared to patients whose surgeons don’t meet that threshold.

Researchers at the University of Toronto in Canada analyzed the administrative health records of 37,881 people with osteoarthritis from the province of Ontario who got their first THR between 2002 and 2009. They pulled data on the rates of complications – including venous thromboembolism (blood clots) or death within 90 days of the surgery, as well as infection, dislocation or revision within two years of the surgery. They also gathered information on patient characteristics, such as age, socioeconomic status, additional health conditions and frailty.

The researchers then matched the patients – both those with and without complications – to their surgeons, and looked at the annual number of total hip replacements performed by those surgeons.

They calculated that patients whose surgeons had performed more than 35 THR in the preceding year had a 30 percent lower rate of early dislocations or revisions compared to patients whose surgeons had performed 35 or fewer procedures in the prior year. Patients operated on by these “high volume” surgeons also had lower risks of dislocation and of needing a revision than those with “low volume” surgeons.

Even for surgeons under the 35-a-year threshold, the risk of complications continued to rise as surgery volume fell. In other words, surgeons doing 25 surgeries a year, for example, had fewer complications than those performing only 10 a year.

The idea that higher volume leads to better outcomes isn’t limited to surgeons. Previous studies have found that complication rates after total joint replacement can vary widely by hospital, but generally are lower in hospitals with a higher volume of surgeries. One study – published in Arthritis & Rheumatism in August 2011 – found that when it come to total hip replacements, hospitals that do more than 200 surgeries a year have significantly fewer complications than those with lower volume.

“It’s well-established that increased volumes are generally correlated with improved outcomes following surgery, and it makes sense that if you do more of something, you will probably get better at it,” explains the lead researcher of the current study, Bheeshma Ravi, MD, PhD, a resident physician at the University of Toronto. “It’s also likely that surgeons are more apt to perform procedures they feel comfortable performing, and this might be reflected in the volume of their practice.”