The invention is directed toward a bone block, a bone-tendon-bone assembly and method of tendon reconstruction in which at least one tendon replacement is extended between two bone blocks and fixed within each of two bone tunnels in the bones of a joint using interference screws. A series of top hats are provided for selective attachment to the piers to increase the depth of the slots between piers, and thereby increase the depth of a joist formed by hardened concrete poured into the slot. The multiphase converter has gate inputs with PWM signals appropriately phase-shifted depending on the number of phases to make balanced phase voltages across the transformer windings.