Alignment apparatus for use in surgery

1. An apparatus comprising:

an electronic orientation sensor comprising a gyroscope, an accelerometer, a magnetic field sensor, and a display;

wherein the electronic orientation sensor is configured to measure a vector of gravity;

wherein the electronic orientation sensor is configured to measure and record its orientation relative to the gravity vector as the electronic orientation sensor is rotated, and calculate the axis of rotation based on collected data;

wherein the electronic orientation sensor is configured to be mounted on the pelvic region of the patient and used to track motion of the pelvic region during surgery in at least two rotational axes, the electronic orientation sensor being configured to be attached to the pelvic region so that as the patient is rotated, the electronic orientation sensor measures and records its orientation relative to the gravity vector, wherein the electronic orientation sensor measures the gravity vector when the patient is in a supine or prone position on a flat surface, and then measure and record its orientation relative to the gravity vector as the patient is rotated towards their right and/or left side;

wherein the collected orientation data is used to calculate the longitudinal axis of rotation of the patient's pelvis, wherein defining the longitudinal axis and the gravity vector allows calculating the transverse vector between anterior superior iliac spines of the pelvis, and wherein an anatomical reference frame of the patient's pelvis is determined independently of any anatomical landmarks,

the electronic orientation device configured to display orientation of an impactor shaft relative to the anatomical reference frame, in terms of angle of anteversion and angle of inclination, in real-time, and

wherein the anatomical reference frame approximates a radiographic image of a bone region of the patient's body in the lateral position from above.

2. The apparatus of claim 1 , wherein the electronic orientation device is mounted on the pelvic region via releasable fixation means so that the orientation of the electronic orientation sensor is substantially fixed relative to the pelvic region, and is mountable so that its bottom edge substantially lines up with a vector line extending between right and left anterior superior iliac spines.

3. The apparatus of claim 1 , wherein the electronic orientation sensor further comprises one or more of: an angular position sensor, a rotary sensor, an absolute position sensor, and a relative position sensor.

4. The apparatus of claim 1 , wherein the electronic orientation sensor is adapted to display a pelvic calibration screen.

5. The apparatus of claim 1 , wherein the electronic orientation sensor is adapted to display a pelvis tracking screen which represents the current orientation of the pelvis substantially in real-time during the surgical procedure.

6. The apparatus of claim 1 , wherein the electronic orientation sensor is operable such that predetermined limits on the degree of motion of the pelvis are inputted by a clinician, and an audible signal is provided when these limits are exceeded.

7. The apparatus of claim 1 , wherein the electronic orientation sensor, using information from a radiographic image of the pelvic region in the lateral position captured with a vertical beam and an x-ray plate beneath the patient, determines sagittal pelvic tilt of the patient.

8. The apparatus of claim 1 , wherein the electronic orientation sensor, using the information from the radiographic image of the pelvic region, determines a discrepancy between the transverse vector of the pelvis and the gravity vector based on alignment of the left and right anterior superior iliac spines.

9. The apparatus of claim 1 , wherein the electronic orientation sensor determines correction of references axes based on the sagittal pelvic tilt and alignment of the left and right anterior superior iliac spines.

10. An apparatus comprising:

an electronic orientation sensor comprising a gyroscope, an accelerometer, a magnetic field sensor, and a display, the electronic orientation device displays orientation of an impactor shaft relative to the anatomical reference frame, in terms of angle of anteversion and angle of inclination, in real-time;

wherein when the electronic orientation sensor is mounted on the pelvic region of a patient during surgery, the electronic orientation sensor tracks motion of the pelvic region in at least two rotational axes;

wherein when the electronic orientation sensor is attached to the pelvic region and the patient is rotated, the electronic orientation sensor measures and records its orientation relative to the gravity vector;

wherein the electronic orientation sensor measures the gravity vector when the patient is in a supine or prone position on a flat surface, and then measures and records the orientation relative to the gravity vector as the patient is rotated towards their right and/or left side;

wherein the collected orientation data is used to calculate the longitudinal axis of rotation of the patient's pelvis, wherein defining the longitudinal axis and the gravity vector allows calculating the transverse vector between anterior superior iliac spines of the pelvis, and wherein an anatomical reference frame of the patient's pelvis is determined independently of any anatomical landmarks; and

wherein the anatomical reference frame approximates a radiographic image of a bone region of the patient's body in the lateral position from above.