As we see femoral head size increasing, thought a team of researchers from Australia, it would be useful to know if there is a difference in revision rates for different femoral head sizes used with different acetabular component sizes. Their study, “A Comparison of Revision Rates and Dislocation After Primary Total Hip Arthroplasty with 28, 32, and 36-mm Femoral Heads and Different Cup Sizes,” was published in the August 17, 2022, edition of The Journal of Bone and Joint Surgery.
“Head size choice remains an important decision step, with surgeons weighing early and long-term complications associated with each head size,” said co-author Wayne Hoskins, M.B.B.S.(Hons), Ph.D. to OTW. “An ideal size is not known. Additionally with different size acetabular components it is unknown how different head sizes perform with different polyethylene thickness. There is also controversy as to the preferred femoral head material with concerns about trunnionosis with the larger femoral heads.”
Dr. Hoskins and his team used data from the Australian Orthopaedic Association National Joint Replacement Registry to capture patients undergoing primary total hip arthroplasty (THA) for osteoarthritis (September 1999 to December 2019). They stratified the acetabular components into quartiles: <51 mm, 51 to 53 mm, 54 to 55 mm, and 56 to 66 mm; femoral head sizes of 28 mm, 32 mm, and 36 mm were compared for each cup size.
It turned out that for acetabular components of <51 mm, 32-mm and 36-mm femoral heads had a lower cumulative percent revision for aseptic causes than 28-mm heads; 36-mm heads had fewer dislocations than 28-mm, and 32-mm heads.
For 51 to 53-mm, 54 to 55-mm, and 56 to 66-mm-diameter acetabular components, there was no difference in the cumulative percent revision for aseptic causes among head sizes. They found that a 36 mm femoral head had fewer dislocations in the first 2 weeks than a 32-mm head for the 51 to 53-mm acetabular components and for the entire period for 56 to 66-mm acetabular components.
“Our findings determined that no ideal head size exists,” commented Dr. Hoskins to OTW, “with 32 and 36mm having equivocal long term revision rates, but the causes of revision and the complication profile differ. In general, 36mm heads provide the most stability and perform well in smaller acetabular components with thinner polyethylene. There was no difference between metal and ceramic heads for any head or acetabular component size.”
Dr. Hoskins’ advice: “Surgeons need to be aware of the complication profiles of each femoral head size, and choice to be made based on both patient and surgeon factors. It is safe to use larger heads with smaller acetabular components and larger heads should be favored when stability is prioritized. Metal and ceramic femoral heads are both acceptable choices.”
