Clinical Outcomes of a Customized 3D-printed Arthrodesis Prosthesis for Reconstruction of Segmental Defects following Tumor Resection in the Proximal Humerus.

BACKGROUND: Currently, shoulder joint function remains poor and the incidence of complications is high after proximal humerus tumor resection. A consensus has not yet been reached on the reconstruction method. Our study investigates whether the use of a customized 3D-printed arthrodesis prostheses can improve shoulder joint function and reduce complications.

METHODS: We conducted a retrospective analysis of consecutive patients with malignant tumors who underwent Malawer type I proximal humeral resection and customized 3D-printed arthrodesis prosthesis reconstruction at our institution from September 2021 to October 2023. We used the Enneking staging system to stage our patients. Functional outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) scoring system and the American Shoulder and Elbow Surgeons (ASES) score. Shoulder range of motion (ROM) was also measured. The demographic data, surgical parameters, functional outcomes and complications were analyzed in this study.

RESULTS: The cohort comprised of 30 patients. The mean age of the patients was 20.1 years (11-57 years) and the mean follow-up duration was 37.7 months (24-49 months). The average resection length of the humerus was 15.5 cm (10-23.5 cm). Among the patients, 28 were classified as Enneking stage IIB, while 2 were classified as stage III. The average MSTS score was 84% and ASES 85%. The average shoulder abduction was 81°, and forward flexion was 82°. The complications included 4 cases of delayed wound healing, 1 case of prosthetic loosening and 2 cases of plate exposure. 4 cases of lung metastasis and 1 case with metastases in both lung and bone occurred during the follow-up period. Six patients (20.0%) experienced soft-tissue failure. Total deltoidectomy was significantly associated with soft-tissue failure in bivariate analysis (P=0.009). There was no case of local recurrence. Radiographic fusion was achieved in 100% of cases at the 12-month follow-up period.

CONCLUSION: For Malawer type I resection of the proximal humerus, shoulder arthrodesis using a customized 3D-printed arthrodesis prosthesis can significantly improve upper limb function. However, total deltoidectomy was associated with an increased risk of soft-tissue complications.