Proximal humerus fractures (PHFs) are common osteoporotic fractures in adults and the elderly, leading to significant disability and reduced quality of life. Current treatment options for displaced PHFs include locking plate fixation (LCP) and various augmentation techniques, but there is no consensus on the optimal treatment. Although, femoral allografts have shown promising results, there is a need for more definitive evidence regarding the utilization of femoral graft augmentation in addition to locking plate fixation in 3- and 4-part PHFs. This study aims to evaluate the effectiveness of using a mushroom-shaped femoral allograft combined with LCP fixation compared to LCP fixation alone. We hypothesize that femoral allograft augmentation with LCP fixation will result in better clinical and functional outcomes than LCP fixation alone at 24 months post-operative

Rationale: Proximal humerus fractures (PHFs) are common osteoporotic fractures in adults and the elderly, leading to significant disability and reduced quality of life. Current treatment options for displaced PHFs include locking plate fixation (LCP) and various augmentation techniques, but there is no consensus on the optimal treatment. Although, femoral allografts have shown promising results, there is a need for more definitive evidence regarding the utilization of femoral graft augmentation in addition to locking plate fixation in 3- and 4-part PHFs.

This study aims to evaluate the effectiveness of using a mushroom-shaped femoral allograft combined with LCP fixation compared to LCP fixation alone. We hypothesize that femoral allograft augmentation with LCP fixation will result in better clinical and functional outcomes than LCP fixation alone at 24 months post-operative.

Objective:

Primary Objective: To compare the CMS between patients treated with LCP fixation plus femoral allograft and those treated with LCP fixation alone at 24 months. The CMS is a validated tool used for assessing overall shoulder function, incorporating bothsubjective and objective components.

Secondary Objectives: To assess differences in clinical outcomes (using Oxford Shoulder Score, Subjective Shoulder Value, Numeric Rating Scale, EQ-5DL), radiological outcomes (humeral head height, humeral neck shaft angle), and the incidence of complications at 24 months.

Study design: This is a single-center, prospective, single-blind, two-armed, parallel-group randomized controlled trial (RCT) to be conducted at Tergooi MC. The study will span a maximum of 48 months, including 24 months for patient recruitment and 24 months for follow-up.

Study population: The study will enroll adults aged 40-70 years presenting with acute (≤3 weeks) three- or four-part PHFs Intervention: Participants will be randomly assigned to either the intervention group (LCP fixation plus femoral allograft) or the control group (LCP fixation alone).

Main study parameters/endpoints: The main study parameter will be the CMS score at 24 months.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation in this study involves no additional burden compared to standard care at Tergooi MC. The study uses routine shoulder function assessments already part of the follow-up protocol, with no extra hospital visits, invasive procedures, or questionnaires required. The risks associated with the investigational treatments are minimal, similar to those observed in previous studies on fibular and femoral allografts. The use of allografts carries potential risks, such as infection and immune reactions, but these are minimized through careful donor selection and screening. Bone allografting is gen-erally safe, though risks like infection, bleeding, and impaired healing remain. Hospitalization and mortality risks are very low. The procedure aims to improve stability and reduce complications, supported by existing literature

Inclusion Criteria:

• Patients between 40 and 70 years
• Presenting with acute (< 3 weeks) 3- or 4-part PHF (NEER classification) Be able to understand and communicate in Dutch; Patient must be competent to make decisions; Patient is willing and able to complete scheduled study procedures Provide written IC.

Exclusion Criteria:

• Head-split fractures;
• Pathological fractures due to malignancy or metastases;
• Individuals diagnosed with dementia or residing in institutional care or other cognitive impairment;
• Terminal illness; Patients with convulsive disorders, collagen diseases, and any other condition that might affect the mobility of the shoulder joint; Active joint or systemic infection; History of prior surgery on the same shoulder; Previous fracture in the same shoulder; Psychiatric illness that precludes informed consent.

Supporting data when the request is reasonable

Beginning after publication with no end date.

Anyone will be able to access the qualitative supportive data via an online data repository.