Large Study Finds Surgical Volume That Lowers THA Risks

May 28, 2014

For the success of total hip replacements, 35 is the magic number, a very large Canadian study finds. Procedures done by surgeons with lower volumes per year have much greater failure risks.

Michaëlsson K. Editorial: Surgeon volume and early complications after primary total hip arthroplasty  BMJ (2014) 348 doi: Published online before print May 23, 2014

Ravi B, Jenkinson R, Austin PC et al.Research: Relation between surgeon volume and risk of complications after total hip arthroplasty: propensity score matched cohort studyBMJ (2014) 348 doi: May 23, 2014

Surgeons should do at least 35 total hip arthroplasty (THA) procedures a year to be proficient, these articles say. More benefits from the Canadian medical system: A population-based study found higher rates of dislocation and revision for surgeons with volumes lower than 35.

The researchers examined THA procedures for the entire population of Ontario from 2002 to 2009, tracking patient records for two years after surgery. The data included 37,881 patients receiving hip replacements at the hands of 350 surgeons with a median surgical volume of 55 procedures a year. The outcome measures were surgical complications (venous thromboembolism, death) within 90 days and infection, dislocation, periprosthetic fracture, or revision within two years.

The risk of early dislocations or revisions was 30% lower for surgeons who performed ≥35 procedures a year than for those with lower volumes.

This study used a novel statistical method to find the “cut point” at which surgeon volume changes the risk significantly. Instead of dividing the results into ranges such as quartiles or quintiles, which are often arbitrary, they found the inflection point that showed the best fit for an area under the curve model.

There was no statistically significant correlation between surgeon volume and the most grave complications of death, infection or venous thromboembolism, or for periprosthetic fracture. The editorial suggests that patient factors rather than surgical performance may be more important to these risks.

Nor was there any correlation with surgical experience in years.

The editorial raises some difficult questions. “Should low volume orthopaedic surgeons stop performing surgery or try to increase their annual number of operations?” While we wait for more rigorous studies, it says, “surgeons would be well advised to keep their engines running at fairly high speed.”

A “delicate issue” is innate surgical skill, independent of volume or experience, which has been demonstrated in bariatric surgery, writes the author, a Swedish orthopaedist. “Surgeons themselves know who they would like to have as their own surgeons.”

“Less skilled surgeons” might switch to administration, teaching, or research, he suggests.