Rhabdomyosarcoma (RMS), the most prevalent soft tissue sarcoma among children and adolescents, is an extremely malignant sarcoma that exhibits a myogenic differentiation propensity. Annually, there are approximately 6 cases per million individuals worldwide, with the majority affecting children, constituting 4.5% of all childhood cancer cases. The male to female ratio falls between 1.4 to 1.7, and the primary sites include the head and neck, trunk, limbs, and genitourinary system. Moreover, due to the lack of specific clinical symptoms, RMS is frequently diagnosed at advanced stages (III to IV) initially, and early metastasis is possible (1). ARMS, the most undifferentiated subtype of RMS, is associated with aggressive behavior. It is predominantly detected in the extremities, perineum, and paravertebral regions; however, it can potentially occur in any area. Furthermore, this condition may be accompanied by lymph node and bone marrow involvement (2, 3). Several reports have emerged regarding ARMS affecting the upper limbs, particularly in the hands. This condition manifests as a gradually increasing soft tissue mass, typically detected through MRI examination as a uniform solid mass (4, 5). There were also cases of multiple bone marrow involvement after metastasis (6). However, only a small number of cases involving Alveolar Rhabdomyosarcoma (ARMS) have been reported to occur in proximity to the long bone in the forearm. These cases exhibit a distinct pattern of breaking through the compartment and causing localized infiltration and of the bone cortex. In this particular report (specific time points in Figure 1 ), we present a compelling case of ARMS manifestation in the left forearm. Notably, the tumor extensively invaded the volar cortex of the ulna, forcefully penetrating the compartment, and compromising multiple vital flexor muscles situated on the volar surface.

Over the past 20 years, significant advancements in medical technology and the adoption of multi-disciplinary treatment have greatly enhanced the survival rates of patients with ARMS (7, 8). How to preserve patients’ limb function after treatment has become the next problem to be solved.

Amputation, an ancient skill, has been gradually submerged by the tide of the times while limb-sparing surgery is now the cornerstone for the treatment (9). The primary principle of surgery dictates that the ARMS must be excised in an “en bloc” way. This entails ensuring that the pseudocapsule of the tumor remains intact, without any breaches, and that the surgical boundaries encompass a wide resection area. Achieving a thorough and precise resection is absolutely crucial for successful functional reconstruction. Any attempts to reconstruct without adhering to proper surgical boundaries would simply be an exercise in futility (10). The second principle requires evaluating the extent of resection margin based on the tissue type surrounding the tumor. When a robust anatomical barrier is present, there is no need for an overly extensive resection range, and it is crucial to preserve as much normal tissue as possible (11).

For upper limb biological reconstruction, skin flaps, muscular reconstruction, ligament repair, and bone reconstruction are all vital components of these techniques. However, in this article, the focus will primarily be on the different approaches used for bone reconstruction ( Table 1 ). Firstly, it should be highlighted that osteotomy is only necessary when there is involvement of bone tissue, as the bone cortex and periosteum provide an effective barrier. Blindly performing osteotomy can result in a poor prognosis (12).

Autogenous bone grafting serves a crucial purpose in bone defect repair. Among the available options, the fibula presents a preferred choice due to its compatible diameter and shape with the radius and ulna. Particularly, when the bone defect surpasses 5cm, employing vascularized fibula yields superior benefits for promoting bone healing (13). The principle of Capanna technique is similar. It increases the support of peripheral cortical bone and enhances the load-bearing and compressive capacity of bone graft composite. As a result, it is primarily utilized in the repair of lower limb bone defects (14).

Tumor-bearing segment devitalization and autograft replantation have a longstanding history in the treatment of bone defects, encompassing methods such as alcohol devitalization, microwave ablation, radiofrequency ablation, and others. However, the adoption of this method has been hindered by concerns about graft reliability. In the last decade, substantial progress in liquid nitrogen devitalization technique has emerged, holding the potential to significantly expand the utilization of this technique in bone defect reconstruction (15).

The treatment of large bone defects presents a challenge due to the contrasting growth rates between bone and surrounding tissues. This disparity often results in the bone defect area becoming filled with connective tissue, making it arduous for the bone defect to heal. However, Masquelet technique introduces a solution by employing an induced membrane that creates an optimal space for bone growth. In addition, this method generates a bioactive-rich environment, expediting the swift repair of bone defects (16).

The Ilizarov bone transport technique utilizes the principle of distraction osteogenesis, aided by an external fixator, to transfer the displaced bone segment to the site of the bone defect in a predetermined direction. This promotes the regeneration of bone tissue within the distraction gap. This technique offers significant advantages such as independence from graft material and avoidance of immune rejection or the need for risky tumor-bearing segment replantation. Additionally, it ensures optimal strength upon the completion of bone maturation. However, it is important to acknowledge the drawbacks of this method, which include a lengthy treatment duration, challenging nursing requirements, and potential complications (17).

Compared to traditional techniques, biological 3D printing technology offers several advantages. It allows for 100% individualized precise customization, enabling high-precision printing of complex anatomical structures. Additionally, it provides an unlimited supply of reconstruction materials. Consequently, although not yet widely employed in clinics, 3D printed biomaterials have garnered extensive attention and are considered the next generation of ideal biological reconstruction technology (18).

In conclusion, we present a unique case of paraulnar ARMS in the forearm, where the tumor has penetrated through the cortex of the bone and impacted the intramedullary region. Our case demonstrates that the management of ARMS necessitates the involvement of a multidisciplinary team. Neoadjuvant chemotherapy is beneficial for facilitating surgical intervention, which remains the cornerstone of treating nonmetastatic ARMS. Ensuring adequate surgical margins is paramount for effective local treatment, while implementing suitable reconstruction techniques can lead to optimal limb function. The incorporation of cutting-edge technologies like 3D printing exhibits considerable potential for transforming this field in the imminent future.

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding author.

Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article. Written informed consent was obtained from the participant/patient(s) for the publication of this case report.

CY: Conceptualization, Resources, Writing – original draft. XW: Supervision, Writing – review & editing. HL: Resources, Writing – review & editing. JZ: Resources, Writing – review & editing. ZX: Resources, Writing – review & editing. WW: Conceptualization, Supervision, Writing – review & editing.