Having both total hip and a lumbar fusion with alterations of your sagittal balance and pelvic tilt may make you at greater risk for dislocation of that total hip. In a symposium at our recent orthopedic Academy meeting the relationship of total hip arthroplasty and lumbar fusion was discussed. The risk is that with a lumbar fusion a total hip may dislocate more readily. The pelvic tilt is an essential parameter and spinal deformity surgery and also in acetabular positioning for total hip surgery. The measurement of the tilt is variable between spine surgeons and hip surgeons. The hip surgeons measured the anterior pelvic plane tilt whereas spine surgeons measure of the spino-pelvic tilt. Both of these measures correlate very well. Lumbar fusion is known to reduce pelvic tilt between standing and sitting. A flexible lumbopelvic unit increases the stability of the total hip arthroplasty when seated by increasing the anterior clearance and acetabular anteversion. Thereby preventing impingement of the hip prosthesis. Lumbar fusion may eliminate this protective pelvic movement. The effect of lumbar fusion on stability of total hip arthroplasties has not been investigated until recently. Patients with spinal pelvic malalignment with previous lumbar fusion had a high prevalence of excessively anteverted acetabular components. Changes in anteversion of the hip are most closely related to changes in pelvic tilt and almost one-to-one ratio. Sagittal spinal correction following total hip arthroplasty resulted in reduced acetabular anteversion which may have implications for stability. It is important for hip surgeons when placing acetabular hip components to understand these parameters and help to prevent subsequent dislocation of the total hip arthroplasty. It is important for your hip surgeon to know what your spinal pelvic parameters are and if you have had a lumbar fusion in the past. It also is important for her spine surgeon to know about your previous total hip replacements.