Fragility fractures of the distal femur and proximal tibia are common in people with spinal cord injury (SCI).
Bone health monitoring should begin in the subacute phase after SCI given the anticipated substantial 30-50% declines in hip and knee region bone mass in the first year, and the associated lifetime increased fracture risk (~1-4% per year post-SCI).
Individuals with chronic SCI and increased risk for lower extremity fragility fractures can be readily identified based on the completion of clinical history and fracture risk factor profile.
Measuring and monitoring hip and knee region bone mineral density (BMD) after SCI are essential to identify low bone mass and quantify lower extremity fracture risk.
Biomarkers provide clinical insight into the metabolic activity of bone, while imaging techniques provide insight into bone density, quality, and architecture. To date, no published prospective study has had sufficient power (sample size and study duration) to evaluate fracture risk reduction.
Bisphosphonates for Prevention of Sublesional Osteoporosis (SLOP) – Benefits
The efficacy of bisphosphonates for the prevention of SLOP appear greater when administered early after SCI onset
Oral tiludronate and clodronate prevent a decrease in hip and knee region BMD in men with paraplegia.
Oral etidronate prevents a decrease in hip and knee region BMD among adults with incomplete paraplegia or tetraplegia who return to walking.
Oral alendronate once weekly maintains hip region BMD.
Once yearly intravenous infusion of zoledronate may reduce hip region BMD decline 12 months following administration.
Pamidronate 30 mg or 60 mg intravenous 4x/year is not effective for the prevention of hip and knee region BMD loss early after SCI among adults with motor complete paraplegia or tetraplegia.
In summary, there is limited evidence that bisphosphonates are moderately effective at preventing declines in hip and knee region BMD by mitigating excessive resorption early after SCI among adults with motor complete paraplegia.
Bisphosphonates for Prevention of SLOP – Side effect control
Bisphosphonates should be used with caution in 1) premenopausal women due to the unknown teratogenic effects of these medications on the fetus during pregnancy; or 2) patients with a prior history of cancer and radiotherapy due to the increased risk of osteonecrosis of the jaw.
Short-term side effects of intravenous bisphosphonates include fever and transient low white blood cell count; oral bisphosphonates may cause heartburn, upset stomach and/or joint pain. Patients taking non-steroidal anti-inflammatory medication and /or anti-coagulants concurrently may require gastrointestinal prophylaxis to reduce the risk of developing upper GI bleeding.
All bisphosphonates (oral or intravenous) may increase the risk of atrial fibrillation, osteonecrosis of the jaw, and atypical femur fracture.
Treating physicians must weigh the relative risk of fracture versus the adverse sequelae of therapy, prior to prescribing oral or intravenous bisphosphonate therapy.
Pharmacologic Therapy for Treatment of SLOP
Alendronate 10 mg daily and calcium 500 mg orally 3x/day is effective for the maintenance of BMD of the total body, hip, and knee region for men with paraplegia.
Vitamin D supplementation results in maintenance of leg region BMD.
Non-pharmacologic Therapy for Prevention and/or Treatment of SLOP
Short-term (6 weeks) therapeutic ultrasound is not effective for preventing
BMD decline after SCI.
Functional electrical stimulation cycling (FES-cycling) does not improve or maintain bone at the tibial midshaft in the acute phase.
FES-cycling may increase lower extremity BMD over areas stimulated among adults with chronic SCI.
Six months of activity-based training is effective for increasing spine BMD.
Neuromuscular electrical stimulation can maintain or increase BMD over the stimulated areas.
There is inconclusive evidence for reciprocating gait orthoses, long leg braces, passive standing, or self-reported physical activity as a treatment for low BMD.
There is a lack of definitive evidence supporting non-pharmacological interventions for either prevention or treatment of SLOP after SCI.