Type of Anchor at the Proximal Fusion Level Has a Significant Effect on the Incidence of Proximal Junctional Kyphosis and Outcome in Adults After Long Posterior Spinal Fusion

Abstract Study Design Retrospective review. Objectives To compare the incidence of proximal junctional kyphosis (PJK) and the clinical, radiographic, and functional outcomes in adults undergoing long posterior spinal fusion with transverse process hooks versus pedicle screws at the uppermost instrumented vertebrae. Summary of Background Data Proximal junctional kyphosis often occurs after instrumented long spinal fusion. Although there have been numerous studies of PJK development in adolescents with idiopathic scoliosis, few studies have focused on adults. Methods This study reviewed data on 47 consecutive adult patients who underwent long spinal fusion (five or more levels) with hooks or screws at the uppermost instrumented vertebrae, from 2004 through 2009, and had 2-year radiographic and clinical follow-up. The hook group (20 patients) and screw group (27 patients) were similar in terms of age, gender, and levels fused. Proximal junctional kyphosis was defined as a sagittal Cobb angle of at least 10° between the lower end plate of the uppermost instrumented vertebrae and the upper end plate of the 2 immediately superior vertebrae, and at least 10° of progression from the previous measurement. The groups' radiographs, complications, and functional outcomes (Scoliosis Research Society–22 Patient Questionnaire and the Oswestry Disability Index) were compared using Hotelling's t2 test (significance, p < .05). Results Comparing immediate postoperative and final follow-ups, none of the 20 patients in the hook group versus 8 of 27 patients in the screw group (29.6%) developed PJK (p = .01). There were no statistical differences between groups in major or minor complications rates. At final follow-up, patients with hooks had significantly higher functional scores than those with screws (p < .05), and patients with PJK had significantly lower functional scores in all Scoliosis Research Society–22 Patient Questionnaire domains except satisfaction. Conclusions Transverse process hooks were associated with a lower incidence of PJK and higher functional scores than pedicle screws.