Introduction. Childhood trauma plays a significant role in morbidity and mortality, and for this reason, it is the subject of forensic examination. The study of the biomechanics of long bone fractures in children, depending on the nature of the injury and age, remains relevant today. According to some authors, long bone fractures are more common in children than in adults. Forensic determination of the mechanism of long bone fractures in children is fraught with difficulties due to the anatomical and physiological characteristics of developing bone [3].

Purpose of the study. Study of the nature of fractures of long tubular bones in children of younger and older age groups.

Material and methods. A review and analytical analysis of modern literary and statistical data, as well as practical cases regarding fractures of long tubular bones in children, were used.

Statistics show that the highest number of fractures occur in the age groups from 5 to 14 years [2, 4]. Currently, the State Forensic Examination Committee of the Republic of Belarus conducts approximately 200 types (subtypes) of expert examinations. Among the main types of examinations, a significant number are medical (57.4 %) and forensic (17.5 %) [1].

In forensic medicine, expert opinions based on practical experience have not yet fully disclosed all aspects of childhood pathology, taking into account the child's age, the processes of its constant growth, physiological characteristics, hormonal changes in the body during adolescence, as well as the characteristics of the course of the pathological process depending on age and immunological status.

The mechanisms of tubular bone fractures in children are related to their characteristics: due to their high elasticity, children's bones bend rather than break, but under excessive loads, they break more often in the growth zones (physis) or due to falls, impacts, twisting, as well as due to pathologies (osteoporosis, genetics) or iatrogenic factors; in newborns, these are often birth injuries.They get injured due to activity, immaturity of the musculoskeletal system and insufficient caution, and their radii, ulna and tibia bones break.

Due to their activity, children are prone to the following types of injuries: domestic, street (usually traffic), sports, and, less commonly, criminal. Bone fractures in children are divided into diaphyseal, metaepiphyseal (periarticular), epiphyseal (intraarticular) and apophyseal.

Children are more likely to injure the bones of their upper limbs, as they instinctively extend their arms when falling, and less likely to injure the bones of their lower limbs, usually as a result of severe traumatic factors, such as a traffic accident.

With an indirect mechanism, the point of force application and the site of injury (fracture) do not coincide. An example is a fracture of the surgical neck of the humerus, resulting from a fall on the abducted hand. Fractures resulting from an indirect mechanism of action occur when bones are flexed, twisted, and force is applied along their longitudinal axis. Avulsion fractures, caused by sudden, excessive muscle contraction, also fall into this group.

According to the relationship of the fracture plane to the long axis of the diaphysis, fractures are classified as transverse, oblique, spiral (screw-shaped), oblique-transverse, fragmented, multi-fragmented (shattered), marginal, and perforated.

Research results. Bone tissue in childhood has a coarse parallel fibrous structure, contains a significant amount of water and collagen and is poorly saturated with mineral substances, which leaves an imprint on the types and morphological properties of diaphyseal fractures.

The periosteum in children is flexible, thick, strong, and well-vascularized. The periosteum forms a sheath around the bone, giving it greater flexibility and protecting it during injury. A characteristic of the musculoskeletal system in children is the frequent occurrence (compared to adults) of supracondylar fractures. This is explained by the fact that the capsular-ligamentous apparatus in children is relatively stronger than the periarticular ends of the bones, where the reduced strength is due to the presence of ossification centers and metaepiphyseal cartilages — growth plates. Therefore, injuries that result in joint dislocations in adults lead to peri- and intra-articular fractures in children.

The presence of epiphyses at the ends of tubular bones, connected to the metaphyses by a wide, elastic growth cartilage, helps maintain the integrity of the bone and absorbs the force of impact. As a result, fractures in children occur with a clearly visible «greenstick» periosteal detachment, where only one side of the bone is damaged, leaving the other intact. The area of periosteal detachment on the side of the bone's tension zone is larger than in the compression zone. In the compression zone, «roll-shaped» swellings of the compact bone form, creating a «trough-like» crumpling, while the opposite side of the bone (in the tension zone) remains intact, which is explained by the higher elasticity of the bone tissue. Longitudinal tear cracks may be observed on the lateral surfaces of the diaphysis. The aforementioned signs of the compression zone can be used to determine the direction of bone bending when a transverse force is applied to the diaphyseal portion. Moreover, with increasing age, this type of injury is less common.

In older age groups, fractures occur in the area of which arrow-shaped fragments and visor-like protrusions are formed (a sign of an incompletely formed typical diaphyseal fracture of an adult bone with the formation of a triangular-shaped fragment).

In children, fractures of tubular bones with fragment displacement are less common than in adults, as their bone tissue is more elastic and has a strong periosteum. In children aged 13–16 years and older, diaphyseal fractures are macroscopically practically indistinguishable from those in adults [4].

When a load is applied along the axis of the bone, impacted fractures usually occur with the formation of a circular swelling of the bone substance in the form of a cuff and the possible formation of longitudinal cracks on one side of the bone.

Conclusion. Thus, in younger age groups, when diaphyseal fractures of long tubular bones occur due to transverse bending, the predominant fracture type is shear and rupture, which occurs in a plastic manner. In older children, bone fracture occurs in a brittle-plastic manner.

References:

1. Volkov, A. A. State Forensic Examination Committee: a decade of the agency’s activities / A. A. Volkov // Forensic examination of Belarus. — 2023. — T 1 (16). — P. 5–8.
2. Pediatric traumatology / V. N. Merkulov, A. I. Dorokhin, K. M. Bukhtin; edited by Academician of the Russian Academy of Sciences S. P. Mironov. — GEOTAR-Media. — 2019. — 256 р.
3. Sokolova, O. V. The state and some prospects of studying childhood pathology in forensic pediatrics / O. V. Sokolova, V. L. Popov // Forensic medical examination. — 2023, no. 2 — P. 41–44.
4. Diagnostics of mechanisms and morphology of fractures in blunt skeletal trauma / 2nd edition, revised: edited by Honored Scientist of the RSFSR, Professor V. N. Kryukov. — Novosibirsk: Science, 2011. — 522 p.