A surgical navigation system for tracking anatomic structures without fiducial markers fixed to an anatomy, the system comprising: a head-worn display device, to be worn by a user during a surgical procedure, comprising a processor unit, a display generator (204, 302), a sensor suite (210, 306) having at least one tracking camera or depth sensor wherein: the processing unit is configured to: receive a topographical map of an exposed surface of an anatomical object of a bone, wherein the topographical map is generated by scanning the exposed surface using the depth sensor or by generating simultaneous localization and mapping data using the tracking camera; create a reference surface map of the exposed surface of the anatomical object of the bone using the topographical map; establish a reference frame relative to the sensor suite for the reference surface map by matching a three-dimensional surface to a three-dimensional model of the anatomical object from a pre-operative scan; and track a pose of the anatomical object of the bone relative to the head-worn display device by: repeatedly scanning the exposed surface of the anatomical object of the bone, generating a displaced surface map of the exposed surface for each scan, comparing the displaced surface map to the reference surface map of the exposed surface of the anatomical object of the bone, determining a rotation and translation required to best fit the displaced surface map with the reference surface map, and rotating and translating the displaced surface map to align the displaced surface map with the reference surface map for best fit. a head-worn display device, to be worn by a user during a surgical procedure, comprising a processor unit, a display generator (204, 302), a sensor suite (210, 306) having at least one tracking camera or depth sensor wherein: the processing unit is configured to: receive a topographical map of an exposed surface of an anatomical object of a bone, wherein the topographical map is generated by scanning the exposed surface using the depth sensor or by generating simultaneous localization and mapping data using the tracking camera; create a reference surface map of the exposed surface of the anatomical object of the bone using the topographical map; establish a reference frame relative to the sensor suite for the reference surface map by matching a three-dimensional surface to a three-dimensional model of the anatomical object from a pre-operative scan; and track a pose of the anatomical object of the bone relative to the head-worn display device by: repeatedly scanning the exposed surface of the anatomical object of the bone, generating a displaced surface map of the exposed surface for each scan, comparing the displaced surface map to the reference surface map of the exposed surface of the anatomical object of the bone, determining a rotation and translation required to best fit the displaced surface map with the reference surface map, and rotating and translating the displaced surface map to align the displaced surface map with the reference surface map for best fit. receive a topographical map of an exposed surface of an anatomical object of a bone, wherein the topographical map is generated by scanning the exposed surface using the depth sensor or by generating simultaneous localization and mapping data using the tracking camera; create a reference surface map of the exposed surface of the anatomical object of the bone using the topographical map; establish a reference frame relative to the sensor suite for the reference surface map by matching a three-dimensional surface to a three-dimensional model of the anatomical object from a pre-operative scan; and track a pose of the anatomical object of the bone relative to the head-worn display device by: repeatedly scanning the exposed surface of the anatomical object of the bone, generating a displaced surface map of the exposed surface for each scan, comparing the displaced surface map to the reference surface map of the exposed surface of the anatomical object of the bone, determining a rotation and translation required to best fit the displaced surface map with the reference surface map, and rotating and translating the displaced surface map to align the displaced surface map with the reference surface map for best fit.