2012 – Acute Proximal Junctional Failure Following Posterior Spinal Fusion for Deformity: Risk Factors and Radiographic Analysis Comparing Thoracolumbar To Upper Thoracic Failures

AUTHORS: Hart RA¹ Hostin R², Bess S⁹, Line B⁹, Ames CP³, Kebaish K⁴, Burton DC⁵, Lafage V⁶, O’Brien MF¹, Schwab FJ⁶, Shaffrey CI⁷, Smith JS⁷, Wood KB⁸

INSTITUTIONS:

• 1. Orthopaedic Surgery, Oregon Health Sciences University, Portland, OR, United States;
• 2. Orthopaedic Surgery, Baylor Scoliosis Center, Plano, TX, United States;
• 3. Neurological Surgery, University of California – San Francisco Medical Center, San Francisco, CA, United States;
• 4. Orthopaedic Surgery, Johns Hopkins University, Baltimore, MD, United States;
• 5. Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, KS, United States;
• 6. Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, NY, United States;
• 7. Neurological and Orthopaedic Surgery, University of Virginia, Charlottesville, VA, United States;
• 8.Orthopaedic Surgery, Massachusetts General Hospital, Boston, MA, United States;
• 9.Orthopaedic Surgery, Rocky Mountain Hospital for Children, Denver, CO, United States

Introduction: Acute proximal junctional failure (APJF) is a challenging complication following spinal deformity surgery. Recent data indicates APJF is not a homogeneous entity; multiple etiologies exist for APJF. Little data exists comparing APJF in the thoracolumbar spine (TL-APJF) to APJF in the upper thoracic spine (UT-APJF). Purpose: identify demographic and radiographic characteristics of patients suffering TL-APJF vs. UT-APJF.

Methods: Multi-center, retrospective analysis of spinal deformity patients suffering APJF within 6 months of posterior instrumented fusion >4 levels. APJF defined as 15 degree postop increase in kyphosis between upper instrumented vertebra (UIV) and UIV+2, fracture of UIV or UIV+1, or need for proximal extension of fusion. TL-APJF= failures between T7-L2; UT-APJK = failures betweenT1-6. APJF etiology defined as fracture (FX), soft tissue failure (ST), or UIV fixation failure (UFF). Demographic, operative and radiographic parameters were evaluated.

Results: 63 patients, mean age 65 years (range 14-81), mean fusion levels 9.1 (range 4-17), met inclusion criteria. TL-APJF were older, had fewer fusion levels, and greater change in lumbar lordosis (LL) vs. UT-APJF (p<0.05; Table). Preop to postop changes in UIV/UIV+2 angle, sagittal vertical axis (SVA), pelvic incidence (PI), and pelvic tilt (PT) were similar TL-APJF vs. UT-APJF (table). FX was most common failure mode in TL-APJF, ST was most common in UT-APJF (p<0.05; table). FX were older than ST (69.2 vs. 58.4, respectively; p<0.05). Change in UIV/UIV+2, SVA, PI, PT and LL were similar between FX and ST. Time of APJF onset and body mass index (BMI) was similar TL-APJF vs. UT-APJF and FX vs. ST.

Conclusion: APJF following spinal deformity surgery is a heterogeneous complication. Discrete considerations include level of UIV and mode of failure. Older patients and constructs with UIV in the TL spine most commonly fail via vertebral fracture while younger patients and constructs with UIV in the UT spine fail through soft tissue. Further research is needed to delineate effective preventative measures.