Pediatric supracondylar humerus fractures: effect of bone-implant interface conditions on fracture stability

Fraturas na criança: Estamos ficando mais cirúrgicos?

Historicamente, as cirurgias no esqueleto imaturo eram reservadas às fraturas expostas ou articulares. Nos últimos anos, a melhora na qualidade e segurança das anestesias, novos equipamentos de imagem, implantes desenhados especialmente para fraturas pediátricas, associados à possibilidade de menor tempo de hospitalização e rápido retorno ao convívio social vêm demonstrando uma nova tendência de avaliar e tratar fraturas na criança. O objetivo deste artigo de atualização é responder às seguintes questões: (1) estamos realmente ficando mais cirúrgicos na abordagem das fraturas em crianças? (2) Caso isto seja verdadeiro, esta conduta cirúrgica está baseada em evidências científicas? De fato, nas últimas décadas, a literatura médica demonstra artigos que suportam melhor evolução das fraturas na criança com o tratamento cirúrgico. Nos membros superiores, isto fica muito evidente na sistematização da redução e fixação percutânea das fraturas supracondilianas do úmero e das fraturas de ossos do antebraço. Nos membros inferiores, o mesmo ocorre com fraturas diafisárias do fêmur e tíbia. No entanto, há lacunas na literatura. Os estudos publicados são geralmente com baixa evidência científica. Assim, pode-se deduzir que, mesmo sendo a abordagem cirúrgica mais presente, o tratamento de fraturas pediátricas deve ser sempre individualizado e conduzido de acordo com o conhecimento e experiência do médico profissional, levando em conta a presença de recursos tecnológicos disponíveis para o atendimento do pequeno paciente. Deve-se incluir todas as possibilidades, não cirúrgicas e/ou cirúrgicas, sempre instituindo ações baseadas na ciência e em concordância com os anseios da família.

The most stable pinning configurations in transverse supracondylar humerus fracture fixation in children: A novel three-dimensional finite element analysis of a pediatric bone model

PURPOSE

This study aimed at finding out the effect of exit height, trajectory and number of pins on the stability of cross and divergent-lateral pins used in the fixation of extension-type, transverse supracondylar humerus fracture (SHF) in children, based on finite element analysis.

METHODS

Distal humerus model consisting of the ossific nucleus of the capitellum (ONC) and distal cartilage of a 6-year-old boy was developed via three-dimensional finite modeling. Various cross and divergent-lateral pinning models with either two or three pins were simulated on an extension-type, transverse SHF and tested in six loading directions.

RESULTS

Two-cross pins and 2-divergent-lateral pins were more stable against torsional and translation forces respectively, while 3-cross pins were the most stable against all forces. The cross pins exiting at the upper border of the distal metaphyseal-diaphyseal junction (MDJ) had the best stiffness among the 2-cross pins, while the lateral pins with a middle third ONC distal pin provided the best stiffness among the 2-lateral pins. A third olecranon fossa pin greatly enhanced stability of the 2-lateral pins.

CONCLUSION

For typical transverse fractures, 2-cross pins are found to be superior to 2-divergent lateral pins only against torsional forces. Pins exiting at the upper border of the MDJ provides the best mechanical stability with 2-cross pins. Two-divergent-lateral pins with a distal pin going through the middle third of the ONC provides the best mechanical stability against translation forces for these transverse fractures. Three-cross pins however offer the best mechanical stability against both translation and torsional forces. This study offers important clues in the preoperative evaluation and management of extension-type supracondylar fractures in children.

The effect of the angle between fracture line and Kirschner wires on stability in supracondylar humerus fractures treated with Kirschner wire fixation: A finite element analysis

Objectives

This study aims to investigate the effects of the angles created by the Kirschner wires (K-wires), which are applied in the percutaneous fixation of supracondylar humerus fractures with cross K-wire, with the fracture line on fracture stabilization.

Patients and methods

The study was conducted on distal humerus fracture models. Medial and lateral K-wires were placed in the fracture models. The angle between the fracture line and the K-wire inserted from medial was represented by alpha (α), while the angle between the fracture line and the K-wires inserted from lateral was represented by beta (β). A combination of various angles (30°, 45°, and 60°) was used in each model, where no two models had the same combination of α and β, resulting in nine different wire configurations. The simulation program was used to simulate the effects of forces, which were applied on rotation, flexion and extension directions, on these models. We measured and compared the stress on the wires and the displacement of fractures under different force configurations.

Results

When the force was applied in the counterclockwise direction, the stresses were 58 megaPascal (MPa) on medial K-wire, 24 MPa on lower lateral K-wire, and 45 MPa on upper lateral K-wire in (45°, 45°) wire configuration. When the force was applied in the clockwise direction, the stresses were 57 MPa on medial K-wire, 23 MPa on lower lateral K-wire, and 45 MPa on upper lateral K-wire in (45°, 45°) wire configuration. In all models, the increased α and β angles were translated into the decreased stress on K-wires at the fracture level and decreased displacement under rotational deforming forces. Despite having generally lower fracture displacement, the increased α and β angles led to variable changes in the stress on K-wires against flexion and extension forces.

Conclusion

In supracondylar humerus fractures, increasing the insertion angle of both medial and lateral K-wires augments stabilization and reduces displacement, particularly against rotational deforming forces.

Mechanical stability study of three techniques used in the fixation of transverse and oblique metaphyseal-diaphyseal junction fractures of the distal humerus in children: a finite element analysis

Background

Management of distal humerus metaphyseal-diaphyseal junction (MDJ) region fractures can be very challenging mainly because of the higher location and characteristics of the fracture lines. Loss of reduction is relatively higher in MDJ fractures treated with classical supracondylar humerus fractures (SHFs) fixation techniques.

Methods

Three different fracture patterns including transverse, medial oblique and lateral oblique fractures were computationally simulated in the coronal plane in the distal MDJ region of a pediatric humerus and fixated with Kirschner Wires (K-wires), elastic stable intramedullary nails (ESIN), and lateral external fixation system (EF). Stiffness values in flexion, extension, valgus, varus, internal, and external rotations for each fixation technique were calculated.

Results

In the transverse fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion, varus, internal, and external rotations, while 3L (3-divergent lateral K-wires) was the most stable in extension and valgus. In the medial oblique fracture model, EF had the best stiffness in flexion, extension, valgus, and varus loadings, while the best stiffness in internal and external rotations was generated by 3MC (2-medial, 1-lateral K-wires). In the lateral oblique fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion and internal and external rotations, while ESIN had the best stiffness in extension and valgus and varus loadings.

Conclusion

The best stability against translational forces in lateral oblique, medial oblique, and transverse MDJ fractures would be provided by ESIN, EF, and K-wires, respectively. K-wires are however superior to both ESIN and EF in stabilizing all three fracture types against torsional forces, with both 2-crossed and 3-crossed K-wires having comparable stability. Depending on the fracture pattern, a 3-crossed configuration with either 2-divergent lateral and 1-medial K-wires or 2-medial and 1-lateral K-wires may offer the best stability.

The outcome of early revision of malaligned pediatric supracondylar humerus fractures

BACKGROUND

Supracondylar humerus fractures (SCHF) are the most common elbow fractures requiring surgical treatment in the pediatric age group. Most fractures are reduced and stabilised adequately. Yet, post-surgical malunion may occur. The purpose of this study is to evaluate our results of early revision surgery in 21 surgically treated pediatric SCHF with immediate postoperative loss of alignment and compare them with previous reports of late corrective osteotomies.

METHODS

Twenty-one pediatric SCHF patients that underwent revision surgery for malalignment within 3 weeks of the initial reduction and fixation consisted the study group. Indications for revision were unacceptable radiographic alignment diagnosed within the first 3 weeks after the index surgery. Clinical outcome included pain, range of motion (ROM) and appearance of the elbow. Radiographic outcome was defined as fracture healing and final alignment, assessed in both coronal and sagittal planes.

RESULTS

The average time interval between index and revision surgery was 7.6 days (range 3-18). In revision surgery, closed reduction was performed in 17 out of 21 patients, and open reduction was required in four. In one patient, an external fixator was added. In the most recent follow up, all patients but three regained full ROM. The remaining three had a deficit of 10° or less. Two patients had cubitus varus of 10° or less. All patients had a marked radiographic improvement after revision, especially in the sagittal plane increasing the humero-capitaller flexion angle by an average of 20°.

DISCUSSION

Malunion after reduction and Kirschner wires (KW) fixation of SCHF is an uncommonly reported phenomenon. When malunion is recognised after fracture healing, corrective osteotomies may carry a significant complications rate. We describe our favourable experience with early diagnosis and revision surgery of malaligned SCHF.