Osteogenic Potential of Bone Callus: A Cross-sectional Study on Microscopic Structure and Healing Stages

Bone callus formation is a critical phase of post-fracture osseous regeneration. Despite extensive animal-model research, human histological data characterizing the osteogenic and osteoconductive microstructure of bone callus across different age groups and genders remain sparse. This study aimed to evaluate the microscopic structure of bone callus with a focus on osteoblast density and osteoconductive parameters in fracture patients at a tertiary care center.

This cross-sectional observational pilot study analyzed bone callus samples from 10 of 23 recruited fracture patients (≥18 years) who underwent open reduction and internal fixation at All India Institute of Medical Sciences, Rajkot. Samples were collected intraoperatively, processed, and stained with hematoxylin and eosin. Five osteoconductive variables - osteoblast density, trabecular thickness, trabecular spacing, trabecular number, and bone volume fraction - were quantified using Image analysis software (NIH, USA) and compared across gender and two age groups (15-24 years vs. 25-64 years). An adult carpal bone (lunate) served as a control. Statistical comparison used the unpaired Student's t-test (Statistical Package for the Social Sciences v16.0).

Male callus exhibited higher osteoblast density (426.7 ± 19.0 vs. 402.5 ± 23.1 N/mm2) and bone volume fraction (54.6 ± 3.0% vs. 51.5 ± 2.7%) than female samples, though not statistically significant (P > 0.05). The younger age group (15-24 years) demonstrated higher osteoblast density (431.3 ± 8.5 N/mm2), trabecular thickness (0.49 ± 0.03 mm), trabecular number (1.74 ± 0.06 N/mm), and bone volume fraction (57.3 ± 2.5%) than the middle-aged group (25-64 years), without reaching statistical significance (P > 0.05). Both callus groups showed higher osteoconductive parameters compared to the adult control bone (lunate).

Bone callus in younger individuals showed numerically higher osteogenic microstructural parameters than middle-aged counterparts, although these pilot-phase differences did not reach statistical significance in this small cohort (n = 10), and all callus samples showed greater osteoblast activity than mature adult bone. These preliminary histological findings suggest - but do not establish - a potential role for bone callus as an autograft material; confirmation of its osteogenic/osteoconductive efficacy will require larger confirmatory cohorts and immunohistochemical, micro-computed tomography, and clinical/experimental validation in the continuation phase of the study.