There is overwhelming evidence that supports the importance of addressing bone health issues early after SCI. A higher incidence of fragility fractures exist in people who sustain SCI (Table 2); the majority of fragility fractures occur following transfers or activities that involve minimal or no trauma (Comarr et al. 1962; Ragnarsson & Sell; 1981; Freehafer 1995). The distal femur and proximal tibia (knee region) are most at risk, consistent with site-specific decreases in BMD to such a degree that fractures of the distal femur were previously referred to as ‘the paraplegic fracture’ (Comarr et al. 1962).
Risk factors for fragility fracture after SCI include: sex, age at injury, time post injury, type of impairment, low BMI, low knee region BMD, and use of anticonvulsants, heparin, or opioid analgesics. Women are at greater risk compared to men (Vestergaard et al. 1998; Lazo et al. 2001; Nelson et al. 2003; Garland et al. 2004). Increasing age and longer time since injury (Frisbie 1997; McKinley et al.1999; Garland et al. 2004; Garland et al. 2005) increases fracture risk which rises significantly at 10 years post injury. Further, people with paraplegia have more fractures (Frisbie 1997) and those with complete injuries have greater bone mass loss compared with those with incomplete injuries (Garland et al. 2004; Garland et al. 2005).
BMD fracture thresholds are values below which fragility fractures begin to occur, whereas fracture breakpoints are values below which the majority of fractures occur (Garland et al. 2005). Knee region aBMD and vBMD thresholds for fracture and breakpoint have been identified (Mazess 1990; Eser et al. 2005; Garland et al. 2005). The use of heparin (HR 1.48, CI 1.20-1.83), opioid analgesics (HR 1.80, CI 1.57-2.06), or anticonvulsants (HR 1.35, CI 1.18-1.54), especially the benzodiazepine sub-class (HR 1.45, CI 1.27-1.65), is associated with an increased risk of lower extremity fragility fractures in men with chronic (≥ 2 yrs injury duration) SCI (Carbone et al. 2013a, 2013b).In a large retrospective cohort study of men with chronic SCI (N = 6969, ≥ 2 yrs post-injury), the use of thiazide-type diuretics was associated with a 25% reduction in the risk of lower extremity fragility fractures (Carbone et al. 2013c). In the general population, individuals with a prior history of fragility fracture or a maternal history of fracture have an elevated fracture risk; these risk factors should also be considered during a fracture risk assessments among patients with SCI. Men with chronic SCI are at a slightly increased risk of lower extremity fragility fractures when exposed to proton pump inhibitors (HR 1.08, CI 0.93-1.25), selective serotonin reuptake inhibitors (HR 1.05, CI 0.90-1.23), or thiazoledinediones (HR 1.04, CI 0.68-1.61) (Carbone et al. 2013a, 2013b). However, these drugs are known risk factors for the development of osteoporosis in the general population, and should therefore be considered when assessing fracture risk in SCI patients.
Fragility fractures, especially around the knee, are common in people with SCI.
We recommend documenting your patient’s fracture risk by completing the risk factor profile checklist (Craven et al. 2008; Craven et al. 2009). We propose that the presence of ≥ 3 risk factors implies a moderate fracture risk, and ≥ 5 risk factors implies a high fracture risk (Table 3).