ILOBONE: A phase I/IIa randomized controlled trial to assess the safety and feasibility of local iloprost therapy for enhancing proximal humerus fracture healing – a pilot study design

Background: Proximal humerus fractures (PHFs) are the third most common fractures in elderly patients. Over 70% of PHFs in patients aged over 60 are displaced fractures, often necessitating surgical treatment. However, osteosynthesis is associated with a high rate of complications, highlighting the urgent need for additional therapeutic approaches to enhance bone healing and prevent osteonecrosis. This study evaluates the safety, feasibility and potential efficacy of local prostacyclin (iloprost) to improve bone healing in patients with PHFs. Methods: Thirty eligible patients will be randomized into one of three groups at a 1:1:1 ratio. All patients will receive angular stable locking plate fixation. Two treatment groups will receive an additional single dose of local iloprost through a 24-hour infusion postoperatively (group 1: low dose; group 2: high dose), while the control group will only receive the osteosynthesis. Patients will be monitored for 52 weeks. The primary endpoint is safety, with secondary endpoints including the preservation of the screw tip apex distance as an indicator of fracture healing, head shaft angle, necrosis rate, and patient-related outcome measures. Discussion: The Ilobone study aims to provide data on the potential for biological augmentation of osteosynthesis procedures in PHFs, prone to healing challenges and complications. Trial registration: The trial is registered with ClinicalTrial.gov (NCT04543682), registered 02 Sep. 2020, https://clinicaltrials.gov/show/NCT04543682 and the German Clinical Trials Registry (DRKS00027081), registered 10 Nov. 2021 https://drks.de/search/de/trial/DRKS00027081.