Peter G Passias1, Cole Bortz, Katherine E Pierce, Nicholas Kummer, Renaud Lafage, Bassel G Diebo, Breton G Line, Virginie Lafage, Douglas C Burton, Eric O Klineberg, Han Jo Kim, Alan H Daniels, Gregory M Mundis, Themistocles S Protopsaltis, Robert K Eastlack, Daniel M Sciubba, Shay Bess, Frank J Schwab, Christopher I Shaffrey, Justin S Smith, Christopher P Ames. 1. Department of Orthopedics, NYU Langone Orthopedic Hospital, New York, NY, USA Department of Orthopedics, Hospital for Special Surgery, New York, NY, USA Department of Orthopedic Surgery, SUNY Downstate Medical Center, Brooklyn, NY, USA Department of Orthopaedic Surgery, Rocky Mountain Scoliosis and Spine, Denver, CO Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, KS, USA Department of Orthopedic Surgery, University of California, Davis, Davis, CA, USA Department of Orthopaedic Surgery, Warren Alpert School of Medicine, Brown University, Providence, RI, USA San Diego Center for Spinal Disorders, La Jolla, CA, USA Division of Orthopaedic Surgery, Scripps Clinic, La Jolla, CA, USA Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Neurosurgery, University of Virginia, Charlottesville, VA, USA Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA.
Abstract
STUDY DESIGN: Retrospective cohort study of a prospective cervical deformity (CD) database. OBJECTIVE: Identify factors associated with Distal Junctional Kyphosis (DJK); assess differences across DJK types. SUMMARY OF BACKGROUND DATA: DJK may develop as compensation for mal-correction of sagittal deformity in the thoracic curve. There is limited understanding of DJK drivers, especially for different DJK types. METHODS: Included: patients with pre- and postoperative clinical/radiographic data. Excluded: patients with previous fusion to L5 or below. DJK was defined per surgeon note or DJK angle (kyphosis from LIV to LIV-2)<-10°, and pre- to postoperative change in DJK angle by<-10°. Age-specific target LL-TK alignment was calculated as published. Offset from target LL-TK was correlated to DJK magnitude and inclination. DJK types: severe (DJK<-20°), progressive (DJK increase>4.4°), symptomatic (reoperation or published disability thresholds of NDI ≥ 24 or mJOA≤14). Random forest identified factors associated with DJK. Means comparison tests assessed differences. RESULTS: Included: 136 CD patients (61 ± 10yrs, 61%F). DJK rate was 30%. Postop offset from ideal LL-TK correlated with greater DJK angle (r = 0.428) and inclination of the distal end of the fusion construct (r = 0.244, both p < 0.02). Seven of the top 15 factors associated with DJK were radiographic, four surgical, and four clinical. Breakdown by type: severe (22%), progressive (24%), symptomatic (61%). Symptomatic had more posterior osteotomies than asymptomatic (p = 0.018). Severe had worse NDI and upper-cervical deformity (CL, C2 slope, C0-C2), as well as more posterior osteotomies than non-severe (all p < 0.01). Progressive had greater malalignment both globally and in the cervical spine (all p < 0.03) than static. Each type had varying associated factors. CONCLUSION: Offset from age-specific alignment is associated with greater DJK and more anterior distal construct inclination, suggesting DJK may develop due to inappropriate realignment. Preoperative clinical and radiographic factors are associated with symptomatic and progressive DJK, suggesting the need for preoperative risk stratification.Level of Evidence: 3.
STUDY DESIGN: Retrospective cohort study of a prospective cervical deformity (CD) database. OBJECTIVE: Identify factors associated with Distal Junctional Kyphosis (DJK); assess differences across DJK types. SUMMARY OF BACKGROUND DATA: DJK may develop as compensation for mal-correction of sagittal deformity in the thoracic curve. There is limited understanding of DJK drivers, especially for different DJK types. METHODS: Included: patients with pre- and postoperative clinical/radiographic data. Excluded: patients with previous fusion to L5 or below. DJK was defined per surgeon note or DJK angle (kyphosis from LIV to LIV-2)<-10°, and pre- to postoperative change in DJK angle by<-10°. Age-specific target LL-TK alignment was calculated as published. Offset from target LL-TK was correlated to DJK magnitude and inclination. DJK types: severe (DJK<-20°), progressive (DJK increase>4.4°), symptomatic (reoperation or published disability thresholds of NDI ≥ 24 or mJOA≤14). Random forest identified factors associated with DJK. Means comparison tests assessed differences. RESULTS: Included: 136 CD patients (61 ± 10yrs, 61%F). DJK rate was 30%. Postop offset from ideal LL-TK correlated with greater DJK angle (r = 0.428) and inclination of the distal end of the fusion construct (r = 0.244, both p < 0.02). Seven of the top 15 factors associated with DJK were radiographic, four surgical, and four clinical. Breakdown by type: severe (22%), progressive (24%), symptomatic (61%). Symptomatic had more posterior osteotomies than asymptomatic (p = 0.018). Severe had worse NDI and upper-cervical deformity (CL, C2 slope, C0-C2), as well as more posterior osteotomies than non-severe (all p < 0.01). Progressive had greater malalignment both globally and in the cervical spine (all p < 0.03) than static. Each type had varying associated factors. CONCLUSION: Offset from age-specific alignment is associated with greater DJK and more anterior distal construct inclination, suggesting DJK may develop due to inappropriate realignment. Preoperative clinical and radiographic factors are associated with symptomatic and progressive DJK, suggesting the need for preoperative risk stratification.Level of Evidence: 3.