A method spacing spinal elements includes installing a first spinal implant having a sensor associated therewith; selecting a second spinal implant based on measurement data provided by the sensor; and replacing the first spinal implant with the second spinal implant. The first and second implants may be installed in separate surgical procedures, or during the same surgical procedure, and the implants may be positioned between a superior spinous process and an inferior spinous process and advantageously directly engage the same. The selection of the second implant may be based on the data provided by the sensor and a material property of the second spinal implant, such as its stiffness. The measurement data may correspond to strain or force data. The sensor may be, but is not required to be, embedded in the first spinal implant. A corresponding apparatus is described.