Table 5 Proposed mechanisms and mediators for the mortality effect of patient factors

Age

Aging reduces the reserve capacity necessary to cope with a double trauma of hip fracture and surgery [22, 37].

Hypothesis only

The number of chronic conditions increases with age [47, 70].

Extent of comorbidity

Sex

Men present with more comorbidity than women [47, 54, 65, 68].

Extent of comorbidity

Men develop delirium [60], lung infection, pneumonia, and septicemia more often than women [54, 68].

Complications

Prefracture function

Patients with poorer pre-fracture ambulatory status often have reduced cardiorespiratory function compared to those with better status [68].

Cardiorespiratory function

Patients with a high degree of dependency are more often delayed to admission than patients with a low degree of dependency [50].

Hospitalization delay

Patients with poor pre-fracture ambulatory status are quickly placed in nursing homes while patients with better status wait in hospital for rehabilitation beds [36].

Length of stay

Preadmission residence

Institutionalized patients develop pneumonia and pressure ulcer more often than patients from community [54, 60].

Complications

Socioeconomic status

Patients with low socioeconomic status are more often delayed to admission than patients with high socioeconomic status [50].

Hospitalization delay

Clinical stability

Patients who are acutely unstable on admission are delayed to surgery more often than those who are stable [25, 39].

Surgical delay

Extent of comorbidity

Multiple comorbidities diminish reserves for stresses of surgery and delays recovery [37, 38].

Hypothesis only

Patients with more comorbidity are delayed to surgery more often than those with less comorbidity [25, 48].

Surgical delay

Patients with more comorbidity are quickly placed in nursing homes while patients with less comorbidity wait in hospital for rehabilitation beds [36].

Length of stay

Body composition

Patients with low BMI are more likely to develop adverse cardiac event post hip fracture surgery [66].

Complications

Patients with low BMI are more likely to be frail [66] and have diminished reserves to cope with the stress of surgery [38].

Hypothesis only

Patients with low BMI often have reduced cardiorespiratory function and a supressed immune system [38].

Immune response, Cardiorespiratory function

History of cerebrovascular accident

Patients with hemiplegia often have more comorbidity and poor pre-fracture ambulatory status [68].

Extent of comorbidity, Pre-fracture function

Dementia

Patients with dementia often have more comorbidity and poor pre-fracture ambulatory status [68].

Extent of comorbidity, Pre-fracture function

Diabetes

Diabetes may lead to poor bone remodeling post hip fracture [52].

Bone remodeling [77]

Diabetes may lead to poor wound healing post hip fracture surgery [52].

Hypothesis only

Patients with diabetes may have poor glycemic control leaving the body prone to infections and complications after surgery [52].

Glycemic control [78] Complications

Malnutrition

Patients with malnutrition often present with more comorbidity and poor pre-fracture ambulatory status.(16;38)

Extent of comorbidity, Pre-fracture function

Myocardial infarction

Patent foramen ovale allows procoagulant cell conjugates and fragments to pass directly from the venous to the arterial blood [37].

Hypothesis only

Secondary hyperparathyroidism

Patients with secondary hyperparathyroidism often have more comorbidity [51].

Extent of comorbidity

Secondary hyperparathyroidism leads to severely altered calcium homeostasis [32].

Calcium homeostasis