This study will be done to evaluate the effect of load dose of vitamin D compared to the dose of usual clinical practice, in improving mobility and reducing disability in older people following a hip fracture.

Hip fractures and related disabilities are important public health issues for elderly people around the world. Attending the progressive aging of the population, an increase in the number of hip fractures is expected. In fact, some studies estimate that, globally, the incidence will exceed 6 million in 2050. In Spain, approximately 33,000 hip fracture occur annually, with an overall incidence of 517 cases per 100,000 elderly people. 90% occur in people over 64 years of age and the incidence increases exponentially beyond 80 years (> 64: 97/100000 inhabitants-year;> 85: 1898/100000 inhabitants-year).

Regarding the functional prognosis, those patients who survive the episode of the fracture often suffer a functional impairment. Outcomes for people who survive hip fracture are of concern, with more than one-quarter dying within a two-year period, and most of them not recovering their previous functional level. More than 10 % of survivors will be unable to return to their previous residence.

Vitamin D deficiency (serum 25 hydroxyvitamin D, 25OHD, level < 30 ng/mL) is commonly associated with hip fracture in elderly people. Without preventive treatment, however, vitamin D deficiency following hip fracture may result in proximal muscle weakness, pain, reduced dynamic balance and performance speed.

It is not clear how much Vitamin D must be taken in order to reach the optimal level. Although the benefits of supplementing patients with at least 800 to 1000 units (U)/day Vitamin D3 may be recognized, there is little information available to guide physicians regarding the appropriate management of hip fracture patients who may be severely Vitamin D deficient, specially in acute hip fracture patients.

A randomized controlled trial, including 50 older adults (aged 75 or over) who having suffered a hip fracture and with vitamin D deficiency, will be carried out. After surgical treatment, participants with vitamin D deficiency (25OHD < 30 ng/mL) will be randomly allocated to an intervention group or control group. For the intervention group, participants will receive 16.000 U Calcifediol oral daily along 5 days. For the control group will receive 16.000 U Calcifediol oral weekly along 5 weeks.

Functional status will be evaluated using Barthel Index, as well the proportion of patients reaching an optimal level of 25OHD (> 30 ng/mL) will be determined at discharge from hospital (1 month approximately), 3, 6 and 12 months of follow up.

Secondary measures include the Timed Up and Go test, gait speed test, Short Physical Performance Battery to compare the effect of the Vitamin D supplementation strategies on functional and muscle strength scales. In addition, to measure the strength and muscle mass will be used handheld dynamometer and bioimpedance analysis respectively

Inclusion Criteria: Patients aged 75 years or over with fragility hip fracture (requiring surgical treatment) and vitamin D deficiency; able to provide informed consent, either directly or via the person responsible.

Definitions:

• Fragility hip fracture: understood as such those that are produced by trauma of low intensity (for example, falls from the own height in standing or smaller)
• Vitamin D deficiency: 25OHD serum levels < 30 ng / mL

Exclusion Criteria:

• Presence of severe functional dependence prior to fracture of the femur (Barthel Index < 35 points)
• Diagnosis of dementia to a moderate degree (defined on "Global Deterioration Scale" (GDS) and "Functional Assessment Staging" (FAST), GDS-FAST > 5).
• Medical conditions that contraindicate receiving vitamin D supplementation: hypercalcemia (calcemia> 10.5 mg / dL), hyperparathyroidism; chronic renal failure with glomerular filtration rate (GFR) <30 mL / min, calcium lithiasis; pathologies with risk of hypercalcemia (tuberculosis, sarcoidosis ...), as well as pathologies involving intestinal malabsorption.
• Hypersensitivity to the active substance or to any of the excipients.
• Use of drugs that interact with the use of vitamin D and with the risk of causing hypercalcemia (phenytoin, phenobarbital, primidone, digoxin).
• Reduced life expectancy (<12 months) due to the presence of advanced concomitant or end-of-life conditions.