title: Prediction of incomplete decompression after cervical laminoplasty on magnetic resonance imaging: The modified K-line.
abstract: OBJECTIVE
  The original K-line was developed on plain radiograph to predict incomplete indirect decompression for the patients with ossification of the posterior longitudinal ligament. The current study modified the K-line on magnetic resonance imaging (MRI) to determine risk factors for incomplete decompression after laminoplasty and to provide a guide for predicting incomplete decompression after laminoplasty and making decisions regarding the surgical approach in patients with cervical spondylotic myelopathy (CSM).
  
  
  METHODS
  A retrospective review of 47 patients with CSM after laminoplasty was conducted. The modified K-line was defined as a line connecting both anterior points of the spinal cord at the level of the inferior vertebrae endplates of C2 and C7 on sagittal T1-weighted MR image. Quantitative analysis of the interval between the maximal anterior compression factor and the modified K-line (IAK) was performed to investigate the efficiency and practicality of this modified K-line. Data analysis involved logistic regression and Spearman rank correlation coefficient.
  
  
  RESULTS
  Thirteen patients (27.7%) had postoperative residual anterior compression of the spinal cord (ACS). Univariate logistic regression with backward stepwise procedure showed that only IAK (odds ratio: 0.301; 95% confidence interval: 0.134-0.673, P=0.003) was a significant risk factor for the occurrence of postoperative ACS. Incidence of ACS was 80% in patients with an IAK of less than 1.5mm and 96.2% in those whose IAK is 0mm.
  
  
  CONCLUSIONS
  The modified k-line can provide a guide for predicting poor clinical outcome after laminoplasty and making decisions regarding the surgical approach in patients with CSM.
authors.affiliation: Orthopedic Department of Changhai Hospital, Second Military Medical University, No. 168, Changhai Rd., Shanghai 200433, People's Republic of China; Department of Spine Surgery, The Second Hospital of Tangshan, Tangshan, Hebei 063000, People's Republic of China.
authors.forename: Lai-Qing
authors.initials: LQ
authors.lastname: Sun
authors.affiliation: Orthopedic Department of Changhai Hospital, Second Military Medical University, No. 168, Changhai Rd., Shanghai 200433, People's Republic of China. Electronic address: spine_liming@163.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Orthopedic Department of Changhai Hospital, Second Military Medical University, No. 168, Changhai Rd., Shanghai 200433, People's Republic of China; Department of Spine Surgery, The Second Hospital of Tangshan, Tangshan, Hebei 063000, People's Republic of China.
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging; D006801:Humans; D065406:Laminoplasty / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011379:Prognosis; D012189:Retrospective Studies; D013117:Spinal Cord Compression / Q000000981:diagnostic imaging*; D055009:Spondylosis / Q000601:surgery*
keywords: Anterior compression; Cervical spondylotic myelopathy; Laminoplasty; Modified K-line