Bone fracture during electrical stimulation of the quadriceps in a spinal cord injured subject

Abstract We report a fracture through the lateral femoral condyle of a paraplegic subject caused by electrical stimulation (ES). The subject was a 50-year-old man who 4 years earlier had sustained a complete spinal cord injury (SCI) at level T6. The fracture occurred during ES-induced measurement of maximal isometric torque of the quadriceps with the knee flexed at an angle of 90°. ES was delivered through surface electrodes with biphasic square wave pulses from a constant current stimulator. The torque was calculated to be 93Nm, corresponding to 20.8kg at the ankle. The regional bone mineral density of the entire lower extremities was .83g/cm 2 , corresponding to 60% of sex- and age-matched able-bodied reference values. Several factors are suspected to have contributed to the fracture: maximal ES in combination with a muscle spasm, servere osteoporosis, increased muscular strength induced by regular ES cycling (twice a week), and testing position with the knee locked in 90° flexion. The risk of fracture as well as various precautions are discussed and should be taken into consideration in future studies.