Faculty Bibliography

Introduction/objectives: Adult spinal deformity correction results in changes in acetabular anteversion. Spinopelvic fusion reduces the protective motion of the pelvis between sitting and standing to prevent THA dislocation. Our hypothesis is that spinal deformity correction may result in dislocation of previously stable THA due to changes in acetabular orientation and fixation to the pelvis. Methods: Patients with previously implanted THA were identified from a prospective database of spinal realignment patients if they had a THA in situ prior to spinal surgery. Only patients with at least 6 months postoperative follow-up and visible THA prostheses were included. All postoperative imaging was reviewed. A chart review was performed to determine the indication for revision THA. Acetabular orientation and global/regional spinopelvic parameter were measured pre-and post-SSD correction. Results: 42 patients met criteria. 27 of these patients underwent a 3-column osteotomy. Four patients (7.2% of patients-5.7% hips) required revision THA after spinal realignment procedure: all revisions were for recurrent dislocations. All had stable THAs prior to spinal realignment. All acetabular components were within Lewinnek's 'safe zone' after ASD correction. There was no difference between the revised and non-revised group in mean anteversion or inclination. All hips requiring revision were fused to the pelvis as part of their SSD correction. Conclusions: Dislocation of a previously stable THA is a potential complication after ASD correction. Instability may be a result of a combination of change in alignment of the acetabular prosthesis, as well as reduced spinopelvic motion from spinopelvic fusion

Introduction/objectives: Lumbar fusion is known to reduce the variation in pelvic tilt between standing and sitting by reducing flexibility of the lumbar spine. Flexibility of the lumbo-pelvic segment theoretically improves stability of a hip replacement during sitting by increasing anterior clearance and acetabular anteversion, thus preventing prosthetic impingement. The effect of lumbar fusion on stability of THA has not been previously investigated. Methods: Medicare database was searched from 2005 to 2012 for patients who underwent THA and spinal fusion. PearlDiver software was used to query the database by ICD-9 procedural code for primary THA and lumbar spinal fusion. The lumbar fusion and THA patients were then divided into three groups-1-2 levels fused, 3-7 levels, and 8 + levels. THA dislocation rates were searched within each group. Patients undergoing THA but no spinal fusion were used as the control group. Statistical significant difference between groups was tested with chi-squared test, and significance at p<0.05. Results: 2912 patients were identified to have THA after lumbar spinal fusion (2420 1-2 level, 476 3-7 level) and 2-year follow-up. The control group of THA patients with no history of spinal fusion consisted of 839,004 patients. The dislocation rate in the control group was 1.55%. Higher dislocation rates were found in patients with spinal fusion of 1-2 levels (2.73%, p<0.0001), 3-7 levels (4.62%, p<0.0001). Patients with 3-7 levels fused had higher dislocation rates than patients with 1-2 levels fused (p<0.0001). Conclusions: Patients with a previous history of lumbar spinal fusion have significantly higher rates of dislocation of their THA than patients without lumbar spinal fusions, and longer fusion segments also had higher dislocation rates