title: C5 nerve palsy after posterior reconstruction surgery: predictive risk factors of the incidence and critical range of correction for kyphosis.
abstract: It has been reported that the incidence of post-operative segmental nerve palsy, such as C5 palsy, is higher in posterior reconstruction surgery than in conventional laminoplasty. Correction of kyphosis may be related to such a complication. The aim of this study was to elucidate the risk factors of the incidence of post-operative C5 palsy, and the critical range of sagittal realignment in posterior instrumentation surgery.
  
  
  
  Eighty-eight patients (mean age 64.0 years) were involved. The types of the disease were; 33 spondylosis with kyphosis, 27 rheumatoid arthritis, 17 athetoid cerebral palsy and 11 others. The patients were divided into two groups; Group P: patients with post-operative C5 palsy, and Group NP: patients without C5 palsy. The correction angle of kyphosis, and pre-operative diameter of C4/5 foramen on CT were evaluated between the two groups. Multivariate logistic regression analysis was used to determine the critical range of realignment and the risk factors affecting the incidence of post-operative C5 palsy.
  
  
  
  Seventeen (19.3 %) of the 88 patients developed C5 palsy. The correction angle of kyphosis in Group P (15.7°) was significantly larger than that in Group NP (4.5°). In Group P, pre-operative diameters of intervertebral foramen at C4/5 (3.2 mm) were significantly smaller than those in Group NP (4.1 mm). The multivariate analysis demonstrated that the risk factors were the correction angle and pre-operative diameter of the C4/5 intervertebral foramen. The logistic regression model showed a correction angle exceeding 20° was critical for developing the palsy when C4/5 foraminal diameter reaches 4.1 mm, and there is a higher risk when the C4/5 foraminal diameter is less than 2.7 mm regardless of any correction.
  
  
  
  This study has indicated the risk factors of post-operative C5 palsy and the critical range of realignment of the cervical spine after posterior instrumented surgery.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Takuto
authors.initials: T
authors.lastname: Kurakawa
authors.affiliation: Department of Orthopaedic Surgery, Kindai University Faculty of Medicine, 377-2, Ohnohigashi, Osaka-Sayama, Osaka, Japan. hiroshimiyamoto@hotmail.com.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyamoto
authors.affiliation: Department of Orthopaedic Surgery, Kobe Rosai Hospital, Kobe, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kaneyama
authors.affiliation: Department of Orthopaedic Surgery, Kobe Rosai Hospital, Kobe, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sumi
authors.affiliation: Department of Orthopaedic Surgery, National Hospital Organization Kobe Medical Center, Kobe, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Uno
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000601:surgery*; D002547:Cerebral Palsy / Q000150:complications / Q000601:surgery*; D002574:Cervical Vertebrae / Q000601:surgery*; D005260:Female; D006801:Humans; D015994:Incidence; D007738:Kyphosis / Q000150:complications / Q000601:surgery*; D065406:Laminoplasty / Q000379:methods; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods; D010523:Peripheral Nervous System Diseases / Q000453:epidemiology*; D011183:Postoperative Complications / Q000453:epidemiology*; D019651:Plastic Surgery Procedures / Q000379:methods; D012307:Risk Factors; D012720:Severity of Illness Index; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D055009:Spondylosis / Q000150:complications / Q000601:surgery*
keywords: C5 palsy; Cervical kyphosis; Foraminal stenosis; Instrumentation; Reconstruction; Surgery