The aim of this study is to evaluate the external validity of a randomized controlled trial comparing choice of hip arthroplasty for elderly patients (>80 years) with a displaced femoral neck fracture.

The hypotheses are that patient reported hip function, quality of life are better and healthier in those included in the randomized controlled trial than those excluded. The external validity of the randomized controlled trial is acceptable.

A prospective randomized controlled trial is planned and patients with a displaced femoral neck fracture will be included and randomized between either a hemiarthroplasty or total hip arthroplasty. All patients screened will be included in a prospective cohort study for evaluation of the external validity of the randomized controlled trial. The prospective cohort study will consist of 3 different groups.

Patients included in the randomized controlled trial will form group 1. Patients eligible for the randomized controlled trial but did not give their informed consent and therefore excluded, form group 2.

Patients with a femoral neck fracture which by any reason were excluded form group 3.

Primary endpoint is patient-reported hip function (Harris hip score) and pain on the operated extremity evaluated with VAS (Visual Analogue Scale) and patient reported quality of life evaluated with EuroQol (EQ-5D). Secondary outcome measurement are the frequency of the complications, periprosthetic fracture, dislocation, revision surgery due to wound infection (deep and superficial) and loosening of the components. Baseline data, age, sex, comorbidity, cognitive status, weight, height, motor function, complications and reoperations. Follow up is performed 1-2 years after surgery.

Group 1 is followed up in the ongoing randomized controlled trial by visits to the orthopedic department at Danderyd Hospital. Group 2 and 3 are followed up by telephone interview 1-2 year after surgery.

The aim of this study is to evaluate the external validity of a randomized controlled trial comparing choice of hip arthroplasty for elderly patients (>80 years) with a displaced femoral neck fracture.

The hypotheses are:

1. The patient reported hip function and quality of life are better in those included in the randomized controlled trial than those excluded.
2. Patients included in the study are healthier than those excluded.
3. The external validity of the randomized controlled trial is acceptable, defined as the difference between patients that provide and do not provide their informed consent do not reach clinical significance (a mean difference in Harris hip score of 10 points).

All patients above 80 years old with an acute displaced femoral neck fracture at Danderyds hospital AB during 2009-2016 will be screened and asked for participation in a randomized controlled trial. Those who fulfill the criteria for inclusion and give their informed consent are enrolled in the randomized controlled trial. Patients that will not give their informed consent and those which do not fulfill the inclusion criteria are enrolled in a prospective cohort study for evaluation of the external validity.

The prospective cohort study will consist of 3 different groups. Patients included in the randomized controlled trial study will form group 1. Patients eligible for the randomized controlled trial but did not give their informed consent and therefore excluded, form group 2.

Patients with a femoral neck fracture which by any reason were excluded form group 3.

Follow-up is performed 1-2 years after surgery. Inclusion criteria in the randomized controlled trial.

1. Age above 80 years 2. Acute (<36h) displaced femoral neck fracture. 3. Independent walker 4. Abscence of cognitive impairment (Pfeiffer test >7) 5. Did not fulfill any exclusion criteria Exclusion criteria in the randomized controlled trial

1. Patient with osteoarthritis or rheumatoid arthritis in the fractured hip

2. Pathological fracture

3. Non walker

4. Cognitive impairment (Short Portable Mental Questionnaire <7)

5. Contraindication to total hip replacement due to wound, patients with comorbidities, deemed not suitable for a total hip replacement by the anesthesiologist, severe coagulation disorder, and severe drug abuse.

6. Deemed unsuitable for inclusion by other reason.

   1. Primary endpoint is patient-reported hip function (Harris hip score) and pain on the operated extremity evaluated with VAS (Visual Analogue Scale)
   2. Patient reported quality of life evaluated with EQ-5D.

Secondary outcome:

1. Secondary outcome measurement are the frequency of the complications, periprosthetic fracture, dislocation, revision surgery due to wound infection (deep and superficial) and loosening of the components.
2. Baseline data, age, sex, comorbidity, cognitive status, weight, height, motor function and complications and reoperations.

Secondary outcome measurements are obtained in the medical records.

Inclusion Criteria randomized controlled trials:

• Age above 80 years
• Acute (<36h) displaced femoral neck fracture.
• Independent walker
• Abscence of cognitive impairment (Short Portable Mental Questionnaire >7points)
• Did not fulfill any exclusion criteria

Exclusion Criteria randomized controlled trial:

• Patient with osteoarthritis or rheumatoid arthritis in the fractured hip
• Pathological fracture
• Non walker
• Cognitive impairment (Short Portable Mental Questionnaire <7points)
• Contraindication to total hip replacement due to wound, patients with comorbidities, deemed not suitable for a total hip replacement by the anesthesiologist, severe coagulation disorder, and severe drug abuse.
• Deemed unsuitable for inclusion by other reason.

Inclusion into prospective cohort study

• Included into the randomized controlled trial.
• Did not give their informed consent for participation in the randomized controlled trial.
• Patients above 80 years of age excluded from participation in the randomized controlled trial due to fulfillment of exclusion criteria or did not fulfill inclusion criteria.

Exclusion into prospective cohort study

• Age below 80 years of age.

A femoral neck fracture in the elderly patient is a common cause of suffering and premature death in an aging population. Femoral neck fractures are mainly a fragility (osteoporotic) fracture, predominantly affecting women after menopause. Included in the study are elderly patients (>80 years) with a displaced femoral neck fracture.