Large acetabular cups implanted to accept large heads can lead to bone loss

CHICAGO — In a study into some of the detrimental effects of the popular trend of upsizing acetabular components for total hip arthroplasty, researchers from Grand Medical Center in Columbus, Ohio, found when the size of component exceeded the size of the native femoral head by 125% to150% the resultant cross-sectional bone loss could reach 27%.

“Careless reaming and not paying attention to what you’re doing can lead to significant bone loss at primary THA [total hip arthroplasty], increasing risk of anterior-posterior wall compromise and reduced bone coverage,” Sharat K. Kusuma, MD, said.

The researchers studied 74 cadaveric pelves in nonarthritic hips, along with a model based on radiographic CT scans and a special OsiriX radiographic software package approved by the FDA. The 3-D calculations of bone area that this combination of technologies made it possible for Kusuma and a collague to simulate reaming and placement of acetabular components.

Sharat K. Kusuma

Implanting a large femoral head combined with excessive reaming can lead to later problems when it is time for a revision THA, Kusuma said. Another consequence of using larger prosthetic head sizes to mitigate dislocation and instability problems and improve hip range of motion was that upsizing the component resulted in less acetabular component coverage, based on reaming data and results of other analyses.

“We propose that surgeons who are going to operate use the femoral head size to begin the templating process and be very cognizant of the amount of bone loss. It can be dramatic with subtle increases in component size,” Kusuma said.

Reference:

Kusuma SK. Paper #36. Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 19-23, 2013; Chicago.

Disclosure: Kusuma is on the speakers bureau for Zimmer and Medtronic, is a paid consultant to Graftys SA, Medtronic, Zimmer, Smith & Nephew and receives research/institutional support from Smith & Nephew.