Introduction: Studies have shown Near Infrared Spectroscopy (NIRS) as being an effective tool in measuring oxygenation non-invasively in tissues. More recently it has been used in clinical settings to assess circulatory and metabolic abnormalities, however, clinical studies in bone are lacking.

Materials and Methods: Ten able-bodied (AB) (5 men and 5 women; age, 23-40 years) and ten spinal cord injured (SCI) (complete cord transection above T10, 5 men and 5 women; age 19–38) participants were matched by age, gender, skin pigmentation and studied.

A spectrometer measured between 498-1000nm, at 0.2Hz , using glass optodes (2mm diameter). Five minutes of resting readings, followed by 3 minutes of below knee arterial occlusion and then 6 minutes post-occlusion were made. The second study, started with 5 minutes of resting readings, vibration loading for 3 minutes at 30 Hz with acceleration of 3g and 6 minutes post-vibration was then conducted.

Results: NIRS showed changes in blood parameters during the hyperemic response (avg. 97% increase in Hb from baseline, p< 0.0001). Able-bodied subjects had significantly quicker (p=0.01) capacity for Hb to return to baseline. There was a significant difference (p=0.001) in the time to peak for Hb following arterial occlusion in the SCI group, 16.6 seconds (sd 4.3), and 10.1 seconds (sd 1.7) in the able bodied.

Conclusion: Our findings suggest that there is a reduction in the bone’s ability to restore oxygenated blood in SCI participants compared to the AB participants. Future studies looking at changes in bone following a range of vibration amplitudes and frequencies in the SCI group should be considered using NIRS in order to optimize potential clinical benefits.