A new classification for heterotopic ossifications in total hip arthroplasty considering the surgical approach.

We would like to introduce a new classification for heterotopic ossifications (HO) after total hip arthroplasty which also considers ossifications within the region of the surgical approach. Furthermore, we will point out the influence of the surgical approach on the rate of HO. We analyzed 75 cementless hip arthroplasties with consecutive HO in a prospective study. The operations were performed by three experienced orthopaedic surgeons using an identical stem and a standardized lateral approach. All patients followed an identical rehabilitation procedure. Clinical and radiological data were documented in a standardized way. We found a total of 40 HO. Only 24 could be exactly classified by the known methods. Our classification considers 3 regions and 4 grades and is relevant for all 40 HO. Electrocauterisation to dissect the muscles in the lateral approach reduced the rate of HO: overall 64.3% to 39.4%; clinically relevant ossifications were reduced to 3.0% from 16.7%. Our new classification considers all HO concerned with total hip arthroplasty, especially those localized in the intertrochanteric region. The rate of HO can be reduced by using electrocauterisation for muscle dissection in the lateral approach.