Does the lumbar spine need to be supported to stabilize the pelvis during total hip arthroplasty in the lateral position?

Total hip arthroplasty is done commonly with the patient in the lateral position. It has been postulated that the lumbar spine may sag in this position because it forms a mobile link between the rigidly held thoracic spine and the sacrum and may cause the pelvis to tilt in the coronal plane, leading to malpositioning of the acetabular cup. To confirm this hypothesis, 10 consecutive patients seen in the preoperative assessment clinic had 2 anteroposterior radiographs taken in the lateral position. The area of exposure was from the lower thoracic spine to the sacrum. In the first radiograph, the lumbar spine was unsupported, and in the second, it was supported. The radiographs showed that the support did not make any significant difference to the position of the lumbar spine or to the position of the pelvis.