Histological ageing of fractures in infants: a practical algorithm for assessing infants suspected of accidental or non-accidental injury

Abstract

Aims: This study is the first to systematically document histological features of fractures of known age in infants (≦12 months). It has been used to develop a tabulated database specifically to guide histopathologists to age fractures in children considered to have suffered accidental or non-accidental injury (NAI). Currently in the United Kingdom there are insufficient pathologists with experience in histological ageing of fractures to meet the medicolegal need for this examination. This study provides a practical tool that will allow those skilled paediatric and forensic pathologists currently involved in assessing infants for evidence of accidental or non-accidental injury a basis for extending their assessment into this area of unmet need.

Methods and results: One hundred and sixty-nine fractures of known age at death were obtained from 52 anonymised infants over a period of 32 years (1985-2016 inclusive). Sections stained using haematoxylin and eosin (H&E) and Martius scarlet blue (MSB) were used to identify specific histological features and to relate them to fracture age. In 1999 the data were entered into a tabulated database for fractures accumulated between from 1985 to 1998 inclusive. Thereafter cases were added, and at 2-yearly intervals the accumulated data were audited against the previous database and adjustments made.

Conclusions: This paper describes the final data set from the 2017 audit. The study was terminated at the end of 2016, as there had been no material changes in the data set for three consecutive audits.

Keywords: ageing; fracture; histology; infant.

Figure 1

Graphic table showing the presence of histological features in fractures of different age. The proportion of fractures of a specific age showing the histological feature is represented by different colours of the boxes (see key in top row of figure). Number of cases showing the feature is also given. Timings measured in: hours = green‐headed columns (2–8); and days = yellow‐headed columns (9–22).

Figure 2

Histological sections [haematoxylin and eosin/Martius scarlet blue (H&E/MSB)] from infant fractures of specified ages. A, MSB (24 h). Haemorrhage [yellow, red blood cells (RBC)] and fibrin (red fibres) in fracture line (arrowed). B, H&E (2 h). Osteocyte lacunae mostly empty. C, H&E (3 days). Surface fibrin (black arrow) and periosteal cell proliferation (blue arrow). D, H&E (3 days). Osteoclasis of native metaphyseal periosteal bone. E, MSB (4 days). Granulation tissue/mesenchymal condensation (arrowed). F1, H&E and F2) MSB (4 days). MSB makes early osteoid (arrowed) more visible and distinguishable from fractured native bone (red on MSB); valuable when scanning multiple bones for fracture. G1, H&E (5 days) and G2, MSB (8 days). New hybrid matrix forming crude trabeculae (arrowed). H (9 days), I (22 days), H&E. Trabeculae of woven osteoid (black arrows) and cartilage nodules (blue arrows). J, H&E (24 days) periosteal callus (trabeculae at right angles to surface of native bone) and medullary callus (I2) showing variation in colour across single trabeculae. K1, H&E polarised light and K2, MSB (40 days) surface lamellar bone. Distinct lamellae in polarised light and irregular red colour on MSB (arrowed). L, H&E. 21‐day fracture with 12‐h refracture extending completely through pre‐existing bridging periosteal callus (arrowed). M, H&E (12 h). Metaphyseal fracture. T‐shaped fracture line dividing metaphyseal cartilage from primary spongiosa (black arrow), extending through adjacent medullary bone (blue arrow), stripping perichondrium (green arrow). N, H&E (4 days). Metaphyseal fracture with granulation tissue in medulla (blue arrow) and subperichondrial space (green arrow). O, MSB (5 days). Fracture at the growth plate involving cortex with a healing response consisting of medullary granulation tissue and early osteoid formation (arrowed) in the cortical fracture line.