Association Between Cervical Sagittal Alignment and Subaxial Paraspinal Muscle Parameters.

Study Design: Retrospective review of prospectively collected data.
Objective: The authors aim to investigate the association between muscle functional group characteristics and sagittal alignment parameters in patients undergoing anterior cervical discectomy and fusion.
Summary of Background Data: The relationship between the morphology of cervical paraspinal muscles and sagittal alignment is not well understood.
Materials and Methods: Patients with preoperative cervical magnetic resonance imaging and cervical spine lateral radiographs in standing position who underwent anterior cervical discectomy and fusion between 2015 and 2018 were reviewed. Radiographic alignment parameters included C2 to 7 lordosis, C2 to 7 sagittal vertical axis (SVA), C2 slope, neck tilt, T1 slope, and thoracic inlet angle. Muscles from C3 to C7 were categorized into four functional groups: sternocleidomastoid group, anterior group, posteromedial group, and posterolateral group (PL). A custom-written Matlab software was used to assess the functional cross-sectional area (fCSA) and percent fat infiltration (FI) for all groups. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index.
Results: A total of 172 patients were included. Regression analyses demonstrated that a greater C2 to 7 SVA was significantly associated with a greater FI of the anterior group from C3 to C5 and with a higher fCSA of the PL group at C3 to C4, and C6 to 7. A larger C2 slope was significantly correlated with a greater FI of the anterior group at C3 to C4 and a higher fCSA of the PL group from C3 to C5.
Conclusion: This work proposes new insights into the complex interaction between sagittal alignment and cervical paraspinal muscles by emphasizing the importance of these muscles in sagittal alignment. The authors hypothesize that with cervical degeneration, the stabilizing function of the anterior muscles decreases, which may result in an increase in the compensatory mechanism of the PL muscles. Consequently, there may be a corresponding increase in the C2 to C7 SVA and a larger C2 slope.
Competing Interests: S.A.A. reports royalties from Ortho Development, Corp.; private investments for Vestia Ventures MiRUS Investment, LLC, IVY II, LLC, ISPH II, LLC, ISPH 3, LLC, HS2, LLC, HSS ASC Development Network, LLC, and Centinel Spine (Vbros Venture Partners V); consulting fee from Depuy Synthes Products Inc., Clariance Inc., Kuros Biosciences AG, Ortho Development Corp., Medical Device Business Service Inc.; speaking and teaching arrangements of DePuy Synthes Products Inc.; membership of scientific advisory board of Depuy Synthes Products Inc., Clariance Inc., and Kuros Biosciences AG; Medical Device Business Service Inc. and trips/travel of Medical Device Business; research support from Spinal Kinetics Inc., outside the submitted work. C.F.P. reports royalties from NuVasive Inc. Accelus; ownership interest for 4WEB Medical/4WEB Inc.; Healthpoint Capital Partners, LP; ISPH II LLC; ISPH 3 Holdings LLC; Ivy Healthcare Capital Partners LLC; Medical Device Partners II LLC; Medical Device Partners III LLC; Orthobond Corporation; Spine Biopharma LLC; Tissue Differentiation Intelligence LLC; VBVP VI LLC; VBVP X LLC; Woven Orthopedics Technologies; consulting fees from 4WEB Medical/4WEB Inc., DePuy Synthes, NuVasive Inc., Spine Biopharma LLC, and Synexis LLC, Accelus; membership of scientific advisory board/other office of Healthpoint Capital Partners, Medical Device Partners II LLC, Orthobond Corporation, Spine Biopharma LLC, and Woven Orthopedic Technologies; and research support from 4WEB Medical/4WEB Inc., Mallinckrodt Pharmaceuticals, Camber Spine, and Centinel Spine, outside the submitted work. G.F.P. reports royalties from Lanx Inc., and Ortho Development Corp.; private investments for BCIMD; and stock ownership of Healthpoint Capital Partners, LP, outside the submitted work. H.A.P. reports research support from Kuros Biosciences AG and Expanding Innovations Inc.; and fellowship support from NuVasive Inc. and Kuros Biosciences BV, outside the submitted work. The remaining authors report no conflicts of interest.
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