title: Optimum pelvic incidence minus lumbar lordosis value can be determined by individual pelvic incidence.
abstract: Adult spinal deformity (ASD) classification showing that ideal pelvic incidence minus lumbar lordosis (PI-LL) value is within 10° has been received widely. But no study has focused on the optimum level of PI-LL value that reflects wide variety in PI among patients. This study was conducted to determine the optimum PI-LL value specific to an individual's PI in postoperative ASD patients.
  
  
  
  48 postoperative ASD patients were recruited. Spino-pelvic parameters and Oswestry Disability Index (ODI) were measured at the final follow-up. Factors associated with good clinical results were determined by stepwise multiple regression model using the ODI. The patients with ODI under the 75th percentile cutoff were designated into the "good" health related quality of life (HRQOL) group. In this group, the relationship between the PI-LL and PI was assessed by regression analysis.
  
  
  
  Multiple regression analysis revealed PI-LL as significant parameters associated with ODI. Thirty-six patients with an ODI <22 points (75th percentile cutoff) were categorized into a good HRQOL group, and linear regression models demonstrated the following equation: PI-LL = 0.41PI-11.12 (r = 0.45, P = 0.0059).
  
  
  
  On the basis of this equation, in the patients with a PI = 50°, the PI-LL is 9°. Whereas in those with a PI = 30°, the optimum PI-LL is calculated to be as low as 1°. In those with a PI = 80°, PI-LL is estimated at 22°. Consequently, an optimum PI-LL is inconsistent in that it depends on the individual PI.
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan. inami3104@me.com.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Inami
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moridaira
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan.
authors.forename: Daisaku
authors.initials: D
authors.lastname: Takeuchi
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan.
authors.forename: Yo
authors.initials: Y
authors.lastname: Shiba
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nohara
authors.affiliation: Department of Orthopaedic Surgery, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi, 321-0293, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Taneichi
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008141:Lordosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010384:Pelvic Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000473:pathology; D011184:Postoperative Period; D011788:Quality of Life; D011859:Radiography; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Adult spinal deformity; Lumbar lordosis; Pelvic incidence; Sagittal alignment