Continuing beyond the pilot phase of the trial was deemed unfeasible

The purpose of this study is to determine the impact of surgical fixation (cancellous screws versus sliding hip screws) and biologic intervention (Vitamin D versus placebo) on patient important outcomes.

Femoral neck fractures are a type of hip fracture associated with high complication rates and poor functional outcomes. It is estimated that over 300,000 hip fractures occur in patients under age 50 annually. Hip fractures in younger aged patients are particularly devastating with profound impairments of quality of life and function. Virtually all patients require surgical repair of their fractures and unlike elderly hip fractures, failure of surgery offers few options for salvage. Arthroplasty is a successful treatment for elderly patients; however, a hip replacement is not a viable option for younger patients because of their higher functional demands for work and recreational activities that are not tolerated by joint replacements.

There is more than one way to perform internal fixation for femoral neck fractures. Cancellous screws have traditionally been the preferred internal fixation implant for femoral neck fractures. Multiple screws (2 or more) are used during fixation, and advocates of this implant promote the construct's superior torsional stability, limited disruption of femoral head blood supply, minimally invasive insertion, and retention of more viable bone than the larger sliding hip screw (SHS). On the other hand, sliding hip screws have been gaining popularity and there is evidence to suggest that SHS provide greater fracture stability and may reduce patient complications. It is currently unknown which method of internal fixation provides the best outcomes for patients.

Femoral neck fracture treatment is further complicated by vitamin D insufficiency in as many as 8 of 10 trauma patients. Vitamin D plays an important role in musculoskeletal health and bone quality because it regulates serum calcium homeostasis. Laboratory research and human clinical studies suggest important associations between vitamin D, musculoskeletal health, and improved fracture healing. Experimental animal studies have demonstrated the concentration of vitamin D metabolites are higher at a fracture callus compared to the uninjured contralateral bone, vitamin D supplementation leads to decreased time to fracture union and increased callus vascularity, and vitamin D increases mechanical bone strength compared to controls. Clinical studies have also demonstrated that vitamin D supplementation increases the callus volume of proximal humerus fractures, increases the number and diameter of type II muscle fibres, and can improve wound healing, however, the effects of vitamin D supplementation in you patients with femoral neck fractures are unknown.

Using a 2x2 factorial design, participant will be randomly allocated to one of four treatment arms. Participants allocated to the cancellous screw group will receive multiple threaded screws (with a minimum of 3 screws and a minimum diameter of 6.5 mm) and those allocated to the sliding hip screw group will receive a single larger diameter partially threaded screw affixed to the proximal femur with a sideplate using a minimum of 2 screws for fixation. Participants allocated to the vitamin D Group will receive a bottle of 2,000 International Units (IU) vitamin D3 drops. Participants will be instructed to take two drops daily for six months, for a total daily dose of 4,000 IU. Participants in the placebo group will receive an identical bottle of placebo drops with no active ingredient. Similarly, they will be instructed to take two drops daily for six months. All vitamin D3 supplement and placebo bottles will be labeled in a blinded manner according to Health Canada and Good Manufacturing Practice.

Participation in this study will last 12 months. In-person participant follow-up visits will occur at enrollment (baseline), post-surgery, 6 weeks, 3 months, 6 months, 9 months, and 12 months post-surgery. Data for all outcomes and radiographs will be collected at each follow-up visit.

Inclusion Criteria

1. Adult men or women ages 18 to 60 years.
2. Fracture of the femoral neck.
3. Fracture amenable to both surgical treatments (SHS and cancellous screws).
4. Operative treatment within 7 days of injury.
5. Provision of informed consent by patient or substitute decision maker.

Exclusion Criteria

1. Patients with previously diagnosed osteoporosis.
2. Fracture-dislocation of the femoral neck and hip joint.
3. Planned antegrade nailing of an ipsilateral femoral shaft fracture (if present).
4. Current infection around the hip (i.e. soft tissue or bone).
5. Stress fracture of the femoral neck.
6. Pathologic fractures secondary to neoplasm or other bone lesion.
7. Patients with known or likely undiagnosed disorders of bone metabolism such as Paget's disease, osteomalacia, osteopetrosis, osteogenesis imperfect, etc.
8. Patients with hyperhomocysteinemia.
9. Patient has an allergy to vitamin D or another contraindication to being prescribed vitamin D.
10. Patient is currently taking an over counter drug and/or food supplement that contains vitamin D and is unable or unwilling to discontinue its use for this study.
11. Likely problems, in the judgment of the attending surgeon, with maintaining follow up (e.g. patients with no fixed address, plans to move out of town). This may include patients with severe mental disorders and drug addictions without adequate support.
12. Pregnancy.
13. Patient is incarcerated.
14. Patient is not expected to survive injuries.
15. The attending surgeon believes the patient should be excluded because they are involved in a conflicting clinical trial.