STREAMING POTENTIALS IN GAP OSTEOTOMY CALLUS AND ADJACENT CORTEX - A PILOT-STUDY

This study documented streaming potentials generated in vivo by maturi ng osteotomy calluses in 10 canine tibiae, Gap osteotomies were allowe d to heal for 6 or 12 weeks and were stabilized by an external fixator . Then, with the dogs under anesthesia, electrical measurements were m ade from 3 silver-silver chloride electrodes placed surgically in dire ct contact with the callus, with adjacent cortical bone, and with the medullary canal (reference electrode), Streaming potentials were recor ded during step loading and sinusoidal bending (0.1-30 Hertz) as the t ibia was deformed by 2 threaded pins coupled to a servohydraulic devic e, Streaming potentials were generated at callus and adjacent cortical sites, but the magnitude was greater on the immature, flexible callus , where bending strain was concentrated; as the callus became increasi ngly rigid, strain and streaming potential magnitude were distributed more evenly over the callus and adjacent cortical fragments, When norm alized to surface strain, mean streaming potential per strain was less dependent on the microscopic structure, although on individual specim ens streaming potential per strain at callus and adjacent cortical bon e sites tended to increase with decreasing porosity, Despite a wide va riation in data in this pilot series, these observations are consisten t with the natural history of callus maturation: the maximum magnitude of streaming potentials in callus appears to decrease as the strain g radient across the site decreases, whereas streaming potentials normal ized to strain increase as bone matures and becomes more dense.