This retrospective study investigates the incidence of anterior intertrochanteric ossifications (AIO), especially in comparison with heterotopic ossifications classified according to Brooker. A classification system of AIO regarding short-term results (< 1 year after surgery) was introduced in 2003: AIO occurred solely in 13 % of all cases (ossifications according to Brooker grade 0) and would have been "overlooked" without a lateral X-ray. The incidence of AIO combined with ossifications according to Brooker > 0 was 48.8 % of all cases. Our study reports long-term results, furthermore correlations between ossifications and clinical outcome, rated by the Harris hip score (HHS) and range of motion (ROM), are evaluated.
149 cementless total hip arthroplasties (Hofer-Imhof threaded cup, straight stem), implanted into 140 patients from November 1991 to December 1994 underwent complete clinical and radiological follow-up from December 2005 to October 2006. The average age of the 81 female and 59 male patients at the time of implantation was 64 years. Without exception, a conventional, transgluteal approach (Bauer) was performed. All patients received indomethacin prophylaxis for 8 consecutive days after surgery. Current X-rays (a.-p. and lateral view) were evaluated in comparison with the former X-rays.
AIO were found in 77 cases (51.7 %), heterotopic ossifications corresponding to Brooker in 93 cases (62.4 %), a combination of AIO and Brooker in 58 cases (38.9 %) and solitary AIO in 19 cases (12.8 %). HHS and ROM were not significantly altered by ossifications.
Our long-term findings compare with the short-term results (indicating lack of new bone formation [heterotopic ossification] after more than one year after surgery, as previously described in the literature concerning ossifications according to Brooker) and verify the incidence rate of solitary AIO. Despite a minor correlation with clinical outcome, AIO could be considered as a possible indicator for predilection of heterotopic bone formation, especially if revision arthroplasty or THA of the contralateral side is needed.