Evaluating the role of capacitance to diagnose bone healing – a baseline study

Abstract

Background: Bone is a biological semi-conductor therefore exhibits electrical properties. Till date no gold standard method is available for measuring bone healing in a fractured bone. Bone healing is dependent upon electrical properties of bone and an understanding of these properties for diagnosing bone union. Capacitance is one such property. The objective of the study was to measure changes in capacitance in different parts of the bone as the fractured bone heals and construct validate capacitance against Radiographic Union Score for Tibia (RUST) score Methods: This pilot study was undertaken on 30 patients of compound fracture both bone of leg treated by insulated external fixators permitting measurement of capacitance from the bone without noise from the soft tissue. Capacitance at different point time was measured in different segments of the fractured bone and construct validated against RUST score. Capacitance across the fracture site at week 2 predicted RUST scores at 20 weeks with a sensitivity of 90%, specificity of 71%, and positive predictive value of 41% and Negative predictive value 83%. Conclusion: The trend of increasing capacitance and its sudden fall as the bone unites confirms that bone does behave like a capacitor. Capacitance varies as the bone heals. Capacitance is significantly different in different segments of the bone. Capacitance across the fracture site may be used to predict RUST score at week 20. However unstable readings of capacitance in some patients make the process difficult.