Blake N Staub1, Renaud Lafage1, Han Jo Kim1, Christopher I Shaffrey2, Gregory M Mundis3, Richard Hostin4, Douglas Burton5, Lawrence Lenke6, Munish C Gupta7, Christopher Ames8, Eric Klineberg9, Shay Bess10, Frank Schwab1, Virginie Lafage1. 1. Spine Service, Hospital for Special Surgery, New York, New York. 2. Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia. 3. San Diego Center for Spinal Disorders, La Jolla, California. 4. Department of Orthopaedic Surgery, Baylor Scoliosis Center, Plano, Texas. 5. Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, Kansas. 6. Columbia University, New York, New York. 7. Washington University School of Medicine, St. Louis, Missouri. 8. Department of Neurosurgery, University of California, San Francisco, San Francisco, California. 9. Department of Orthopaedic Surgery, University of California, Davis, Sacramento, California; and. 10. Department of Orthopaedic Surgery, Rocky Mountain Hospital for Children, Denver, Colorado.
Abstract
OBJECTIVE: Numerous studies have attempted to delineate the normative value for T1S-CL (T1 slope minus cervical lordosis) as a marker for both cervical deformity and a goal for correction similar to how PI-LL (pelvic incidence-lumbar lordosis) mismatch informs decision making in thoracolumbar adult spinal deformity (ASD). The goal of this study was to define the relationship between T1 slope (T1S) and cervical lordosis (CL). METHODS: This is a retrospective review of a prospective database. Surgical ASD cases were initially analyzed. Analysis across the sagittal parameters was performed. Linear regression analysis based on T1S was used to provide a clinically applicable equation to predict CL. Findings were validated using the postoperative alignment of the ASD patients. Further validation was then performed using a second, normative database. The range of normal alignment associated with horizontal gaze was derived from a multilinear regression on data from asymptomatic patients. RESULTS: A total of 103 patients (mean age 54.7 years) were included. Analysis revealed a strong correlation between T1S and C0-7 lordosis (r = 0.886), C2-7 lordosis (r = 0.815), and C0-2 lordosis (r = 0.732). There was no significant correlation between T1S and T1S-CL. Linear regression analysis revealed that T1S-CL assumed a constant value of 16.5° (R2 = 0.664, standard error 2°). These findings were validated on the postoperative imaging (mean absolute error [MAE] 5.9°). The equation was then applied to the normative database (MAE 6.7° controlling for McGregor slope [MGS] between -5° and 15°). A multilinear regression between C2-7, T1S, and MGS demonstrated a range of T1S-CL between 14.5° and 26.5° was necessary to maintain horizontal gaze. CONCLUSIONS: Normative CL can be predicted via the formula CL = T1S - 16.5° ± 2°. This implies a threshold of deformity and aids in providing a goal for surgical correction. Just as pelvic incidence (PI) can be used to determine the ideal LL, T1S can be used to predict ideal CL. This formula also implies that a kyphotic cervical alignment is to be expected for individuals with a T1S < 16.5°.
OBJECTIVE: Numerous studies have attempted to delineate the normative value for T1S-CL (T1 slope minus cervical lordosis) as a marker for both cervical deformity and a goal for correction similar to how PI-LL (pelvic incidence-lumbar lordosis) mismatch informs decision making in thoracolumbar adult spinal deformity (ASD). The goal of this study was to define the relationship between T1 slope (T1S) and cervical lordosis (CL). METHODS: This is a retrospective review of a prospective database. Surgical ASD cases were initially analyzed. Analysis across the sagittal parameters was performed. Linear regression analysis based on T1S was used to provide a clinically applicable equation to predict CL. Findings were validated using the postoperative alignment of the ASDpatients. Further validation was then performed using a second, normative database. The range of normal alignment associated with horizontal gaze was derived from a multilinear regression on data from asymptomatic patients. RESULTS: A total of 103 patients (mean age 54.7 years) were included. Analysis revealed a strong correlation between T1S and C0-7 lordosis (r = 0.886), C2-7 lordosis (r = 0.815), and C0-2 lordosis (r = 0.732). There was no significant correlation between T1S and T1S-CL. Linear regression analysis revealed that T1S-CL assumed a constant value of 16.5° (R2 = 0.664, standard error 2°). These findings were validated on the postoperative imaging (mean absolute error [MAE] 5.9°). The equation was then applied to the normative database (MAE 6.7° controlling for McGregor slope [MGS] between -5° and 15°). A multilinear regression between C2-7, T1S, and MGS demonstrated a range of T1S-CL between 14.5° and 26.5° was necessary to maintain horizontal gaze. CONCLUSIONS: Normative CL can be predicted via the formula CL = T1S - 16.5° ± 2°. This implies a threshold of deformity and aids in providing a goal for surgical correction. Just as pelvic incidence (PI) can be used to determine the ideal LL, T1S can be used to predict ideal CL. This formula also implies that a kyphotic cervical alignment is to be expected for individuals with a T1S < 16.5°.
Authors: Peter Gust Passias; Haddy Alas; Nicholas Kummer; Peter Tretiakov; Bassel G Diebo; Renaud Lafage; Christopher P Ames; Breton Line; Eric O Klineberg; Douglas C Burton; Juan S Uribe; Han Jo Kim; Alan H Daniels; Shay Bess; Themistocles Protopsaltis; Gregory M Mundis; Christopher I Shaffrey; Frank J Schwab; Justin S Smith; Virginie Lafage Journal: J Craniovertebr Junction Spine Date: 2022-09-14
Authors: Haddy Alas; Peter Gust Passias; Bassel G Diebo; Avery E Brown; Katherine E Pierce; Cole Bortz; Renaud Lafage; Christopher P Ames; Breton Line; Eric O Klineberg; Douglas C Burton; Juan S Uribe; Han Jo Kim; Alan H Daniels; Shay Bess; Themistocles Protopsaltis; Gregory M Mundis; Christopher I Shaffrey; Frank J Schwab; Justin S Smith; Virginie Lafage Journal: J Craniovertebr Junction Spine Date: 2021-09-08