Photodynamic Bone Stabilization in Pathologic Humeral Fractures: Implant Safety, Pain Relief and Functional Outcomes

Background: Pathologic fractures of the humerus due to metastatic disease cause severe pain, loss of function and reduced quality of life. Surgical treatment is predominantly palliative and aims to achieve rapid pain relief, early functional recovery and minimal treatment-related morbidity. The photodynamic bone stabilization system (IlluminOss^®) is a minimally invasive, radiolucent, intramedullary device that may address these needs. Methods: This retrospective analysis of prospectively collected data from two centers included 51 patients with 52 pathologic humeral lesions (completed or impending fractures) treated with photodynamic intramedullary stabilization between 2013 and 2025. Baseline variables comprised demographics, Eastern Cooperative Oncology Group (ECOG) performance status, comorbidities, pain (numeric rating scale, NRS) and function (Musculoskeletal Tumor Society Upper Extremity Score, MSTS-UE; Toronto Extremity Salvage Score, TESS). Lesion characteristics, operative details, in-hospital course, follow-up outcomes (TESS, patient satisfaction/quality of life) and long-term endpoints (survival, complications) were recorded. Results: The study cohort (25 women, 26 men; mean age 68.5 years) represented a highly palliative population with advanced, disseminated malignant disease. Of the 52 humeral lesions, 35 (67.3%) presented as pathological fractures, whereas 17 lesions (32.7%) were classified as impending fractures due to extensive osteolysis. Among the impending fractures, Mirels scores ranged from 8 to 10, with three lesions scoring 8, eight lesions scoring 9, and six lesions scoring 10. ECOG performance status was 0-2 in 75.0% and 3-4 in 25.0% of patients. Preoperative pain was high (mean NRS 7.1) and function markedly reduced (median MSTS-UE 9.5/30; median TESS 36.5/100). Postoperatively, pain improved significantly from NRS 7.1 to 2.0 (p < 0.001). MSTS-UE increased from a median of 9.5 to 20 (p < 0.001). Follow-up showed further functional improvement with an increased TESS of 36.5 to 61 (p < 0.001), high patient satisfaction and subjective improvement in quality of life. Kaplan-Meier analysis (n = 44) demonstrated a median survival of 6 months for ECOG 0-2 and 3 months for ECOG 3-4. Implant failure (Henderson type III) occurred four times (7.7%) and was successfully revised with plate and/or screw osteosynthesis or diaphyseal replacement. Conclusions: Photodynamic intramedullary stabilization provides effective treatment for selected pathologic humeral lesions with low implant failure rate, offering rapid pain relief, functional improvement and low perioperative morbidity. Implant failure in complex fracture morphologies highlights the need for morphology-adapted indication and consideration of supplemental fixation in high-risk cases.