Trabecular microfractures. Nature and distribution in the proximal femur.

The nature and distribution of healing trabecular microfractures (TMF) of femoral heads were studied in 50 autopsy specimens, 30 patients with osteoarthritis (OA) of the hip and 45 patients with subcapital fractures of the femoral neck (SFFN). Macerated coronal slices were examined with a dissecting microscope, and the TMFs were identified where there was callus formation, either nodular or smooth. The number of TMFs did not differ significantly in the SFFN and age-matched control groups. The number of TMFs in the OA group was lower than in SFFN and age-matched control groups. The numbers of nodular TMFs in the control and SFFN groups did not differ significantly but were fewer in the OA group. Smooth TMFs were present in similar numbers in OA, control, and SFFN groups. The ratio of the nodular to smooth TMFs regressed with age. The greater proportion of nodular TMFs in older patients was indicative of an early stage of woven bone callus formation. In all three groups (excluding controls younger than 50 years of age), TMFs tended to appear some distance from the midpoint of the trabeculae. The number of TMFs in trabeculae parallel and perpendicular to the direction of principal stress was similar in all three groups.