The Advantages of 4-rod Construct over the 2-rod Techniques in Adult Spinal Deformity Patients who Underwent Pedicle Subtraction Osteotomy: A Multicenter Retrospective Comparative Study

Abstract

Study DesignRetrospective study ObjectiveTo compare clinicoradiological outcomes and complication profiles of the traditional two-rod construct versus the four-rod construct in patients with adult spinal deformity (ASD) who underwent pedicle subtraction osteotomy (PSO). MethodsWe performed a retrospective review of 208 ASD patients who underwent lumbar PSO and long fusion from thoracic to the pelvis at two centers. Two different techniques including the four-rod construct and the traditional two-rod technique were used at the PSO level. Clinicoradiological outcomes and complication profiles of the patients were documented and compared statistically between the groups. ResultsThe four-rod construct was associated with statistically lower rates of rod fracture (44.8% vs 26.4%, p<0.01), pedicular screw loosening at the PSO level (25.3% vs 14.0%, p=0.04) and reoperation (49.4% vs 33.9%, p=0.02). Radiologically, the four-rod technique was associated with higher degree of lumbar lordosis (LL) (-37.4°vs -26.8°; p<0.01) and improved pelvic tilt (PT) (-17.2° vs -9.9°; p<0.01) and sacral vertical axis (SVA) corrections (-211.5° vs -192.2°; p=0.04). Overall, the four-rod construct was associated with improved quality of life (p=0.04) and statistically lower oswestry disability index at 12 months postoperatively (p<0.01). ConclusionsOur results showed that the four-rod construct was associated with statistically lower rates of rod fracture and pedicular screw loosening at the osteotomy level, higher degree of LL correction and improved PT and SVA than the two-rod technique. The four-rod technique was also associated with improved quality of life and disability index and lower complication profiles.