title: Spontaneous Improvement of Compensatory Knee Flexion After Surgical Correction of Mismatch Between Pelvic Incidence and Lumbar Lordosis.
abstract: METHODS
  A retrospective study.
  
  
  OBJECTIVE
  The aim of this study was to investigate the correlation between pelvic incidence (PI) and lumbar lordosis (LL) mismatch and knee flexion during standing in patients with lumbar degenerative diseases and to examine the effects of surgical correction of the PI-LL mismatch on knee flexion.
  
  
  BACKGROUND
  Only several studies focused on knee flexion as a compensatory mechanism of the PI-LL mismatch. Little information is currently available on the effects of lumbar correction on knee flexion in patients with the PI-LL mismatch.
  
  
  METHODS
  A group of patients with lumbar degenerative diseases were divided into PI-LL match group (PI-LL ≤ 10°) and PI-LL mismatch group (PI-LL > 10°). A series of radiographic parameters and knee flexion angle (KFA) were compared between the two groups. The PI-LL mismatch group was further subdivided into operative and nonoperative group. The changes in KFA with PI-LL were examined.
  
  
  RESULTS
  The PI-LL mismatch group exhibited significantly greater sagittal vertical axis (SVA), pelvic tilt (PT) and KFA, and smaller LL, thoracic kyphosis (TK), and sacral slope than the PI-LL match group. PI-LL, LL, PI, SVA, and PT were significantly correlated with KFA in the PI-LL mismatch group. From baseline to 6-month follow-up, all variables were significantly different in the operative group with the exception of PI, although there was no significant difference in any variable in the nonoperative group. The magnitude of surgical correction in the PI-LL mismatch was significantly correlated with the degree of spontaneous changes in KFA, PT, and TK.
  
  
  CONCLUSIONS
  The PI-LL mismatch would contribute to compensatory knee flexion during standing in patients with lumbar degenerative disease. Surgical correction of the PI-LL mismatch could lead to a spontaneous improvement of compensatory knee flexion. The degree of improvement in knee flexion depends in part on the amount of correction in the PI-LL mismatch.
  
  
  METHODS
  3.
authors: Department of Orthopaedic Surgery, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors: Xiaofei
authors: X
authors: Cheng
authors: Department of Orthopaedic Surgery, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors: Feng
authors: F
authors: Zhang
authors: Department of Orthopaedic Surgery, PLA 306 Hospital, Beijing, China.
authors: Jigong
authors: J
authors: Wu
authors: Department of Orthopaedic Surgery, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors: Zhenan
authors: Z
authors: Zhu
authors: Department of Orthopaedic Surgery, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors: Kerong
authors: K
authors: Dai
authors: Department of Orthopaedic Surgery, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors: Jie
authors: J
authors: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D015994:Incidence; D007717:Knee / Q000503:physiopathology*; D007738:Kyphosis / Q000601:surgery*; D008141:Lordosis / Q000453:epidemiology* / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D020127:Recovery of Function / Q000502:physiology*; D012189:Retrospective Studies; D013904:Thoracic Vertebrae / Q000601:surgery*