Neurospine.  2019 Jun;16(2):267-276. 10.14245/ns.1836268.134.

Independent Correlation of the C1–2 Cobb Angle With Patient-Reported Outcomes After Correcting Chronic Atlantoaxial Instability

Affiliations
  • 1Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Seoul, Korea. hayoon@yuhs.ac
  • 2Department of Spine Surgery, Changzheng Hospital, Second Military Medical University, Shanghai, China.
  • 3Department of Spine Surgery, Beijing Jishuitan Hospital, Peking University, Beijing, China. hedamd@vip.163.com
  • 4Department of Clinical Laboratory, Jiangxi Province Children's Hospital, Nanchang, China.
  • 5Department of Orthopedics, Zhabei Central Hospital of Jing'an District, Shanghai, China.
  • 6Department of Radiology, the First Affiliated Hospital of Nanchang University, Nanchang, China.

Abstract


OBJECTIVE
To investigate three-planar radiographic results and patient-reported outcomes (PROs) after correcting chronic atlantoaxial instability (AAI) by translaminar screw (TLS) and pedicle screw (PS) fixation, and to explore the potential association of atlantoaxial realignment with PRO improvements.
METHODS
Twenty-three patients who underwent C1 lateral mass screw (LMS)-C2 TLS and 29 who underwent C1 LMS-C2 PS with ≥ 2 years of follow-up were retrospectively analyzed. Three-planar (sagittal, coronal, and axial) radiographic parameters were measured. PROs including the Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score and the Short Form 36 Physical Component Summary (SF-36 PCS) were documented. Factors potentially associated with PROs were identified.
RESULTS
The radiographic parameters significantly changed postoperatively except the C1-2 midlines' intersection angle in the TLS group (p = 0.073) and posterior atlanto-dens interval in both groups (p = 0.283, p = 0.271, respectively). The difference in bilateral odontoid lateral mass interspaces at last follow-up was better corrected in the TLS group than in the PS group (p = 0.010). Postoperative PROs had significantly improved in both groups (all p < 0.05). Thereinto, NDI at last follow-up was significantly lower in the TLS group compared with PS group (p = 0.013). In addition, blood loss and operative time were obviously lesser in TLS group compared with PS group (p = 0.010, p = 0.004, respectively). Multivariable regression analysis revealed that a change in C1-2 Cobb angle was independently correlated to PROs improvement (NDI: β = -0.435, p = 0.003; JOA score: β = 0.111, p = 0.033; SF-36 PCS: β = 1.013, p = 0.024, respectively), also age ≤ 40 years was independently associated with NDI (β = 5.40, p = 0.002).
CONCLUSION
Three-planar AAI should be reconstructed by C1 LMS-C2 PS fixation, while sagittal or coronal AAI could be corrected by C1 LMS-C2 TLS fixation. PROs may improve after atlantoaxial reconstruction in patients with chronic AAI. The C1-2 Cobb angle is an independent predictor of PROs after correcting chronic AAI, as is age ≤ 40 years for postoperative NDI.

Keyword

Atlantoaxial instability; Patient-reported outcome measures; Radiographic parameters; Translaminar screw; Pedicle screws
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