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.

OBJECTIVE: In this retrospective study we compared clinicoradiologic outcomes and complication profiles of the traditional 2-rod construct versus the 4-rod construct in patients with adult spinal deformity (ASD) who underwent pedicle subtraction osteotomy (PSO). METHODS: We performed a retrospective review of 208 ASD patients at 2 referral centers who underwent lumbar PSO and long fusion from thoracic to the pelvis. Two different techniques, including the 4-rod construct and the traditional 2-rod technique, were used at the PSO level. Clinicoradiologic outcomes and complication profiles of the patients were documented and compared statistically between the groups. RESULTS: The 4-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 4-rod construct 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 4-rod construct was associated with improved quality of life (P = 0.04) and statistically lower Oswestry Disability Index score at 12 months postoperatively (P < 0.01). CONCLUSIONS: Our results showed that the 4-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 2-rod technique. The 4-rod construct was also associated with improved quality of life and Oswestry Disability Index and lower complication profiles.