Group 1 underwent percutaneous long Kirschner wire intramedullary fixation (Long K-wire group, Figures 1A,B). The patient was positioned supine under general anesthesia, and the injured limbs was prepared under sterile conditions. The operator and assistant held the distal and proximal ends of the fracture, respectively, applying anti-traction, flexion, and reduction of the fracture end to the volar or dorsal side. The C-arm machine showed that the fracture was well-aligned. A Kirschner wire was employed to fix the fracture end and reach the bone marrow cavity of the proximal end of the fracture. An additional K-wire was inserted for additional stabilization, crossing the first K-wire into the bone marrow cavity or bone cortex of the proximal end of the fracture. In additional fluoroscopy, the fracture exhibited proper alignment, the K-wire was in place, and the fixation was firm. The K-wire end was shortened and bent, and the sterile gauze material was bandaged and supplemented with plaster external fixation.

Group 2 underwent open reduction and internal fixation with a plate and screws (Plate Group, Figures 1C,D). In this group, the patient was positioned supine under general anesthesia and the injured limbs was prepared under sterile conditions. A suitable incision was made at the fracture site, and the skin and fascia were dissected. Blood vessels were separated and protected, and the fracture end was exposed through the intermuscular space. A metal osteosynthesis plate was placed after direct vision reduction, and fixation was achieved with 4–6 screws. The C-arm revealed that the fracture fixation was and the fixation appeared stable and the fragments were adequately aligned. The wound was cleaned with normal saline, and sutured in layers, and a sterile dressing was applied with external plaster support.

Statistical analysis was conducted using SPSS (version 28.0.1.1). Measurement data (radiographic evaluation, incision length, operation duration, postoperative hospital stay, forearm function, and complications) are expressed as x¯±s. Independent samples t test was employed to compare the two groups. Count data were compared using x2 test or corrected x2 test. P < 0.05 was considered statistically significant.

Surgery was successfully completed in all cases. In the long K-wire group, four participants were treated with a single long K-wire percutaneous intramedullary fixation, one participant was treated with 3 K-wires for stable fixation. The long K-wire group had a significantly shorter operative time and postoperative hospital stays compared to the plate group (P < 0.05) (Table 3).

The average follow-up time of the two groups was 14 ± 7 months. During the follow-up period, 1 participant in the plate group experienced a refracture due to secondary trauma before plate removal. The refracture was treated with open reduction and replacement of plate internal fixation. Similarly, one participant in the long K-wire group experienced a refracture, which was treated with closed reduction and long K-wire intramedullary fixation. The fractures of both participants healed well after the second surgery. There was no vascular or nerve injury before and after surgery in the two groups. Furthermore, no complications, such as delayed union or non-union occurred during the fracture healing period. The Gartland-Werley score was assessed through telephone follow-up. No residual deformity or arthritis was observed in the plate and screw group. One participant reported limited mobility, along with wrist weakness, reduced dorsiflexion, and impaired palmar flexion. Two other participants in the plate and screw group experienced sustained local pain.

Regarding forearm function measured based on the Gartland-Werley score (Table 4), the results were as follows: Plate Group: 30 excellent and 2 fair. Long K-Wire Group: 30 excellent and 1 fair. There was no significant difference between the two groups (P > 0.05, The precise P-value is presented in the table).

The results of image evaluation for both groups are presented in Table 5. Compared to measurements conducted after 1 day and 1 month post-operatively, no significant differences were found between the two groups in terms of RMI, IRI, and IRL (P > 0.05).

The transition zone was between the distal one-third boundary of the radius and the upper edge of the metaphysis, and this concept has undergone years of development (Figure 3) (8). In 2006, the International Society for the Study of Internal Fixation (PCCF) divided children's long bones into proximal epiphysis and metaphyseal ends, diaphysis, distal epiphysis, and metaphyseal ends (8). Liber et al. took the sum of the widths of the distal epiphyseal plates of the radius and the distal epiphyseal plates of the ulna and radius as the side length. In 2010, they defined the area where the two squares do not overlap as the junction of the metaphyseal plates (2). Ten years later, Li et al. defined the area between the distal one-third boundary of the radius and the upper edge of the metaphysis as the transition zone (9). Distal radius metaphyseal-diaphyseal transition fracture is at high risk of delayed healing and non-healing due to insufficient blood supply. The actual size of the distal radius is affected by several factors, such as the patient's age and height. In this study, distal radius metaphyseal transition referred to the area between the distal one-third boundary of the radius and the upper edge of the metaphysis.

The metaphyseal transition of the distal radius is located in the transition between the metaphysis and the diaphysis, with relatively few vascular perforating branches (10); thus, its local blood supply and remodeling potential are weaker than those of the metaphysis. It is also easily affected by the traction of peripheral tendons such as the extensor pollicis brevis, abductor pollicis longus, and brachioradialis muscle, which elevates the risk of unstable fractures (1).

Fractures observed in children are different from those observed in adults, as the bones contain more organic components, leading to greater toughness and orthopedic ability (11, 12). The generally acceptable angle for complete remodeling of distal radius metaphyseal fractures within 5 years is 30–35 degrees in the sagittal plane and 10 degrees in the coronal plane, but it often differs by age and gender (13). Therefore, appropriate methods that can ensure functional recovery and align with the growth characteristics of children's bones are necessary for treating fractures of the distal radius epiphyseal transition in children (14).

Forearm fractures are among the most common fractures observed. While stable fractures of both adults and children can be managed conservatively through closed reduction and cast immobilization (15), unstable fractures may necessitate surgical fixation (16–19). Open reduction with plate fixation and closed reduction with intramedullary Kirschner wire fixation were two commonly employed surgical methods (20–22), with completely different treatment concepts. One is based on the Arbeitsgemeinschaft für Osteosynthesefragen (AO) principle, offering anatomical reduction and firm fixation. The other one is based on the principles of Biological Osteosynthesis (BO), offering functional reduction with minimal surgical trauma. Most fractures in the distal radial metaphyseal transition zone can be observed among adolescents aged 8–14 years old, when the bone is in the growth stage. Older children (12–14 years old) may require perfect reduction (axial malalignment of less than 10) anatomical reduction and internal fixation based on the AO principle, while younger children (8–10 years old) may be more inclined to choose functional reduction based on the BO principle. This leads to a relative age limitation in the selection of treatment options. Since the growth and development of different individuals are different, the treatment plan cannot be completely determined based on children's age. Through preliminary analysis of the characteristics of radial bone growth, we found that there is a narrow segment in the medullary cavity of the radial shaft. This narrow segment is narrower than the medullary cavity of the proximal and distal ends of the radius and is the narrowest segment of the entire radial medullary cavity. We found that the stability of the Kirschner wire intramedullary fixation greatly increases when the intramedullary Kirschner wire is fixed through this narrow segment. We hypothesize that the intramedullary fixation of the Kirschner wire can increase the stability of the Kirschner wire intramedullary fixation when it is fixed through the narrow segment of the radial medullary cavity (for children aged 8–14 years). Open reduction and internal fixation with plates and screws can achieve anatomical reduction, restore the physiological curvature of the distal radius, and facilitate forearm function recovery in children, but is associated with prospective disadvantage (3). Closed reduction percutaneous Kirschner wire intramedullary fixation technology is minimally invasive (23, 24), promotes the rapid healing of fractures, and requires a short hospitalization period. The surgical approach we advocate causes less trauma compared to plate and screw internal fixation and elastic intramedullary nail fixation. It does not require a second hospitalization for the removal of internal fixation (similar to other percutaneous Kirschner wire internal fixation treatment methods, only the steel pins need to be removed in the outpatient department).

In our clinical practice, we noted that long intramedullary Kirschner wires may enhance the stability of Kirschner wire fixation; however, the precise definition of “long” Kirschner wires remains elusive. The optimal length of Kirschner wires for insertion into the medullary cavity of the distal radius is currently under investigation and scrutiny. Therefore, we explored the anatomical features of the radius, which is a key factor in the surgical management of patients with distal radius fractures. Long Kirschner wires enhance the stability of fixation through the medullary cavity because a constricted region exists in the medullary cavity of the central portion of the radial shaft. When a long Kirschner wire extends through the medullary cavity to this constricted region, it significantly improves the stability of fixation through the medullary canal. This empirical conclusion is supported by clinical observations and a profound understanding of the radial isthmus, where the narrowed medullary canal provides a critical biological anchor point for long Kirschner wires to maximize rotational and axial stability (25).

Based on our experience, intramedullary fixation longer than 7 cm generally suffices to effectively prevent restoration loosening and angulation deformities at the fracture site, so a “long Kirschner wire” denotes a Kirschner wire in the medullary cavity with more than 7 cm length. A narrow segment of the radial medullary cavity appears nearly 7 cm away from the distal end of the radius, and the exact value varies among individuals (Figure 4). Prospective randomized controlled studies with a larger volume of clinical data should validate these findings. Additionally, we recommend the application of forearm tube plaster postoperatively for 3–4 weeks as adjunctive therapy. This method introduces controlled micro-motion at the fracture site, which partly promotes fracture healing by stimulating stress at the fracture site.

The incidence of this particular type of fracture is not high, making it difficult to obtain a huge number of participants who meet the requirements for inclusion. Our conclusions require a larger prospective randomized controlled study for confirmation.