We wanted to measure the size of the osteolysis of the pelvis and to quantify its location and we wanted to assess the correlation of these measurements with the clinical result.

We evaluated 40 hips (31 patients) that showed definitive osteolysis among 116 hips (97 patients) that underwent 3 dimensional CT scanning post-operatively after total hip arthroplasties with using cementless acetabular cups. The inclusion criteria were a follow up duration of more than 18 months and no history of infection. The radiographs were obtained at the 6th to 12th week postoperatively. The size of pelvic osteolysis was divided into 4 groups (less than 1 cm3 (A), between 1 cm3 to 2 cm3 (B), between 2 cm3 to 3 cm3 (C), more than 3 cm3 (D)), and the location of osteolysis was divided into 5 groups (anterior, posterior, superior, inferior and central) The size and location of osteolysis and the wear of the polyethylene were analysed in relation to the clinical outcome, which was assessed using the Harris Hip Score).

The average size of the osteolysis was 3.2 cm3 (A 14 cases in group A, B 11 cases in group B, C 4 cases in group C, and D 11 cases in group D). There was significant correlation between the size of the osteolysis and the clinical outcome (Rs=-0569). However, there was no significant correlation between the osteolysis location (Anterior: 18 cases, Superior: 5 cases, Posterior: 10 cases, Inferior: 33 cases and Central: 32 cases) and the clinical outcome (P=0.35).

There is a significant correlation between the size of the osteolysis and the Harris Hip Score (Rs=- 0569). Especially, a pelvic osteolysis of more than 3 cm3 was found to be correlated with a decreased postoperative HHS (P=0.022). We hope that these results may be useful to help guide the treatment of osteolysis.