Feasibility Study to Investigate the Potential Reduction of Bone Mineral Density Loss in Spinal Cord Injured Patients Using Ekso Therapy

There are an estimated 40,000 people living with a Spinal Cord Injury (SCI) in the UK alone (http://www.apparelyzed.com/statistics.html).

Spinal cord injury (SCI) leads to rapid and profound bone loss with large decreases in bone mineral density (BMD) below the level of the lesion (Frey-Rindova et al., 2000). Decreases in BMD of ~2% per month from the lower limbs have been reported and rates of loss are maximal over the first two years (Jiang et al., 2005). Bone loss is associated with increased bone resorption and remodelling imbalance which is thought to be due to the combined effects of immobility together with neurogenic effects. As a consequence, there is an increased risk of fragility fractures particularly of the lower limbs including an increased risk of hip fracture. Lower limb fragility fractures affect up to 35% of patients following SCI. These fractures are associated with considerable morbidity and an increase in mortality.

BMD is conventionally measured using dual-energy x-ray absorptiometry (DXA). This technique enables measurement of bone mineral content, projected area and areal BMD at the lumbar spine and proximal femur. DXA does not allow differentiation between cortical and trabecular bone and does not have the ability to examine microstructural change. High resolution peripheral quantitative computed tomography (HR-pQCT) is a novel technique which enables changes in trabecular and cortical microstructure to be evaluated. Using HR-pQCT it is possible to detect changes in surrogate measures of bone strength in response to loss of weight bearing activity over just 6 weeks (Kazakia et al, 2014).

To date, there is no established intervention which has been demonstrated to prevent or reverse bone loss and fractures in this clinical setting. Small studies have suggested that anti-resorptive agents including bisphosphonates (Bryson et al., 2009) and denosumab (Gifre et al., 2015) have potential to protect against bone loss following SCI. Physical therapy using vibration was ineffective (Dudley-Javoroski et al., 2015) as was an ambulation programme undertaken late in the management of SCI (Needham-Shropshire et al., 1997). Once bone loss has occurred, it appears to be at best only partially reversible on recovery of lower limb function. It has been postulated that weight-bearing activity on its own (Dionyssiotis et al., 2015) or perhaps in combination with anti-resorptive treatment has the potential to preserve or improve bone health following SCI.

In 2014, a new therapy service called 'Ekso Therapy' was introduced at the Sheffield Princess Royal Spinal Injuries Centre. Ekso is a revolutionary powered exoskeleton device, which is strapped on to patients with a SCI to enable them to stand and walk. The device is manufactured by Ekso Bionics and is CE marked. It has been reported to be a good form of exercise allowing patients to stretch, and is claimed to be beneficial for muscle strength, bone health, bowel and bladder function and circulation and has a positive psychological impact. None of these claims have been investigated or proven in large clinical trials.