Background: A better understanding of the factors associated with
the size and/or progression of osteolytic lesions has been hampered by a lack
of sensitivity of radiographic measurement techniques.
Methods: We retrospectively analyzed quantitative computed
tomography scans that had been made with use of a high-resolution multi-slice
scanner with a metal artifact-suppression protocol. The scans had been made to
determine the volume of osteolytic lesions around thirty-five cementless
Harris-Galante acetabular components that had been in situ for at least ten
years. Repeat scans of thirty hips allowed for the measurement of progression
in the size of osteolytic lesions over a one-year period. Associations between
the volume of osteolytic lesions, progression in the size of the lesions,
polyethylene wear since the time of implantation, change in component
position, and patient-related variables (age, gender, body mass index,
activity level, walking limitations, joint pain, and function) were
determined.
Results: In sixteen of the thirty hips that had repeat computed
tomography scans, the lesions progressed in size during the study period. The
median size of the lesions in these sixteen hips was 10.3 cm3 at
the time of the initial scan, compared with 13.3 cm3 at a median of
fifteen months later (p = 0.001). Osteolytic lesions measuring >10
cm3 in volume on the initial scan were 2.5 times (95% confidence
interval 1.3 to 4.8 times) more likely to progress in size over one year than
smaller lesions were. Patients with greater polyethylene wear rates, higher
activity levels, no walking limitations, and larger prosthetic femoral head
dimensions (26 or 28 mm) had significantly larger osteolytic lesions (p <
0.0001, p = 0.009, p = 0.006, and p = 0.028, respectively). Progression in the
size of the osteolytic lesions over one year was significantly associated with
larger initial osteolytic lesions (p = 0.002), greater polyethylene wear rates
(p = 0.009), and larger (26 or 28-mm) prosthetic femoral head dimensions (p =
0.019).
Conclusions: There is considerable variation in the rates of
progression of the size of osteolytic lesions around stable acetabular
components. Lesion size and the progression of lesion size are generally
related to polyethylene wear rates, higher patient activity levels, and
larger-diameter femoral heads. Osteolytic lesions measuring >10
cm3 in volume are associated with a high rate of progression.
Level of Evidence: Prognostic Level III. See Instructions
to Authors for a complete description of levels of evidence.