Renaud Lafage1, Frank Schwab1, Jonathan Elysee1, Justin S Smith2, Basel Sheikh Alshabab1, Peter Passias3, Eric Klineberg4, Han Jo Kim1, Christopher Shaffrey5, Douglas Burton6, Munish Gupta7, Gregory M Mundis8, Christopher Ames9, Shay Bess10, Virginie Lafage1. 1. Spine Service, Hospital for Special Surgery, New York, NY, USA. 2. Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, VA, USA. 3. Department of Orthopaedics, NYU Langone Orthopedic Hospital, New York, NY, USA. 4. Department of Orthopaedic Surgery, University of California, Davis, Sacramento, CA, USA. 5. Department of Neurosurgery, Duke University Medical Center, Durham, NC, USA. 6. Department of Orthopaedics, University of Kansas Medical Center, Kansas City, KS, USA. 7. Department of Orthopaedics, Washington University, St Louis, MO, USA. 8. Scripps Clinic, San Diego, CA, USA. 9. Department of Neurological Surgery, University of California, San Francisco, School of Medicine, San Francisco, CA, USA. 10. Denver International Spine Center, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, CO, USA.
Abstract
STUDY DESIGN: Retrospective cohort study. OBJECTIVES: Establish simultaneous focal and regional corrective guidelines accounting for reciprocal global and pelvic compensation. METHODS: 433 ASD patients (mean age 62.9 yrs, 81.3% F) who underwent corrective realignment (minimum L1-pelvis) were included. Sagittal parameters, and segmental and regional Cobb angles were assessed pre and post-op. Virtual postoperative alignment was generated by combining post-op alignment of the fused spine with the pre-op alignment on the unfused thoracic kyphosis and the pre-op pelvic retroversion. Regression models were then generated to predict the relative impact of segmental (L4-L5) and regional (L1-L4) corrections on PT, SVA (virtual), and TPA. RESULTS: Baseline analysis revealed distal (L4-S1) lordosis of 33 ± 15°, flat proximal (L1-L4) lordosis (1.7 ± 17°), and segmental kyphosis from L2-L3 to T10-T11. Post-op, there was no mean change in distal lordosis (L5-S1 decreased by 2°, and L4-L5 increased by 2°), while the more proximal lordosis increased by 18 ± 16°. Regression formulas revealed that Δ10° in distal lordosis resulted in Δ10° in TPA, associated with Δ100 mm in SVA or Δ3° in PT; Δ10° in proximal lordosis yielded Δ5° in TPA associated with Δ50 mm in SVA; and finally Δ10° in thoraco-lumbar junction yielded Δ2.5° in TPA associated with Δ25 mm in SVA and no impact on PT correction. CONCLUSIONS: Overall impact of lumbar lordosis restoration is critically determined by location of correction. Distal correction leads to a greater impact on global alignment and pelvic retroversion. More specifically, it can be assumed that 1° L4-S1 lordosis correction produces 1° change in TPA / 10 mm change in SVA and 0.5° in PT.
STUDY DESIGN: Retrospective cohort study. OBJECTIVES: Establish simultaneous focal and regional corrective guidelines accounting for reciprocal global and pelvic compensation. METHODS: 433 ASD patients (mean age 62.9 yrs, 81.3% F) who underwent corrective realignment (minimum L1-pelvis) were included. Sagittal parameters, and segmental and regional Cobb angles were assessed pre and post-op. Virtual postoperative alignment was generated by combining post-op alignment of the fused spine with the pre-op alignment on the unfused thoracic kyphosis and the pre-op pelvic retroversion. Regression models were then generated to predict the relative impact of segmental (L4-L5) and regional (L1-L4) corrections on PT, SVA (virtual), and TPA. RESULTS: Baseline analysis revealed distal (L4-S1) lordosis of 33 ± 15°, flat proximal (L1-L4) lordosis (1.7 ± 17°), and segmental kyphosis from L2-L3 to T10-T11. Post-op, there was no mean change in distal lordosis (L5-S1 decreased by 2°, and L4-L5 increased by 2°), while the more proximal lordosis increased by 18 ± 16°. Regression formulas revealed that Δ10° in distal lordosis resulted in Δ10° in TPA, associated with Δ100 mm in SVA or Δ3° in PT; Δ10° in proximal lordosis yielded Δ5° in TPA associated with Δ50 mm in SVA; and finally Δ10° in thoraco-lumbar junction yielded Δ2.5° in TPA associated with Δ25 mm in SVA and no impact on PT correction. CONCLUSIONS: Overall impact of lumbar lordosis restoration is critically determined by location of correction. Distal correction leads to a greater impact on global alignment and pelvic retroversion. More specifically, it can be assumed that 1° L4-S1 lordosis correction produces 1° change in TPA / 10 mm change in SVA and 0.5° in PT.