Background: Osteonecrosis of the femoral head is a debilitating
condition characterized by progressive degeneration of bone that eventually
leads to collapse of the femoral head in the majority of patients. Femoral
head-sparing procedures have been more successful in pre-collapse stages of
osteonecrosis than in post-collapse stages, although some patients with early
post-collapse disease have had no additional progression of the disorder.
Nevertheless, the effects of collapse on the articular cartilage are not well
understood, and radiographic staging of femoral head collapse does not address
the condition of the articular cartilage.
Methods: In the current study, we investigated the relationship
between the mechanical properties of post-collapse articular cartilage and the
histologic findings and macroscopic grades of the articular cartilage from
hips with stage-IV osteonecrosis, those with stage-V osteonecrosis, and those
Results: The cartilage from both stage-IV and stage-V hips showed
significant degeneration compared with the normal control cartilage, but there
was no significant difference between the two stages. There was significant
variability in the histologic and mechanical properties of these samples that
correlated strongly with the gross appearance of the cartilage surface but not
with the lesion size.
Conclusions: These results suggest that articular cartilage that
appears macroscopically normal may remain mechanically functional even in
patients with large osteonecrotic lesions or a late radiographic stage of the
Clinical Relevance: These findings lend support to the position that
femoral head-sparing surgical strategies designed to restore the contour of
the femoral head may have utility in some patients with advanced osteonecrotic
disease. The gross appearance of the articular cartilage may be a useful tool
for identifying those patients.