[Computed tomography assessment of incorporation bone grafts after cemented acetabular revision]

The aim of the study was assessment, on the basis of computed tomography (CT) examination, of remodelling of compacted frozen bone sliver grafts used in acetabular revision arthroplasty.

The study involved ten patients treated in the years 1998-2000 for aseptic loosening of hip joint prosthesis elements. Eight women and two men were studied. The mean age of the patients was 69.6 years (from 52 to 74 years). The mean time between primary and revision arthroplasty was 6.8 years. Spiral CT examination was performed 6 weeks and 3, 6, 12, 24, 36 months after the operation. Density measurement was done using ROI (region of interest) function including spongy bone area from 50 to 80 mm2. The studied layer thickness was 3.2 mm. In the examination both hip joints were assessed, accepting the joint not operated on as standard for a given patient. The measurement was done in six zones according to DeLee, Charnley.

Progressing reduction of graft density was found in relation to healthy bone density. During the first three months most rapid density reduction was observed in all patients. The lowest density decrease was seen in the postero-superior part of the acetabulum while the highest density reduction occurred in the lower part. Trabeculation change was observed from that resembling compact bony tissue to that corresponding to spongy tissue. In two patients after six months a significant graft density reduction occurred both in the lower and upper parts of the acetabulum. In these patients acetabular loosening was confirmed, requiring reoperation.

CT examination of bone density makes possible quantitative assessment of bone graft remodelling and qualitative assessment imaging the structure of the grafts. The non-invasive method of CT examination of bone graft density allows for prognostication as to stability of the seated acetabulum.