What Is “True” Rate of Dislocation After Total Hip Replacement?

A new study shows that the rate of dislocation after total hip replacement is substantially higher than previously thought.

Lars L. Hermansen, M.D. of Hospital of South West Jutland, Esbjerg, Denmark, and colleagues found that the “true” rate of dislocation in the first two years after total hip replace is actually 50% higher at 3.5%.

“Since our results are based on a large cohort over a five-year inclusion period and include all hospital contacts in Denmark within the first two years after THA [total hip arthroplasty], we believe to have found the ‘true’ occurrence of dislocation within this patient group and timeframe,” the researchers wrote.

Hip dislocation is one of the leading reasons for revisions after THA. Previous studies have reported varying rates, making any definite conclusions difficult.

In their study, “’True’ Rate of Dislocation After Total Hip Replacement Is Higher Than Previously Thought,” published online on December 18, 2020 in The Journal of Bone & Joint Surgery, the researchers analyzed 31,105 cases of primary THA for osteoarthritis in Denmark between 2012 and 2014 identified through the Danish National Patient Register.

More than 40% of the patients had at least two dislocations and three-fourths of the initial dislocations happened within the first three months after THA, the researchers found.

They explained they were able to get a more comprehensive look at the dislocation by linking the hip replacement registry to the national patient database and by reviewing alternative procedure codes in patient files.

It is important to note that some hip dislocations are able to be treated without surgical procedure or hospital admission. And some patients don’t get treated for the dislocation at the hospital where they had the THA.

The true rate “was a 50 percent increase compared with the correctly coded dislocations captured by administrative register-data-only,” the researchers wrote.

Dr. Hermansen and his team also found that dislocation risk was lower in patients younger than 65 years old, higher in those over 75 years old, and lower in men than women.

Patients in better health according to the American Society of Anesthesiologists Physical Status Classification System also had a lower risk of dislocation.

A lower risk was association with cemented fixation, lateral surgical approach, larger femoral head size, and use of dual-mobility cups, according to their data.

“Comprehensive search algorithms are needed in order to identify all dislocations so that this complication can be accurately reported in national registers,” they wrote.