Spinal compensation patterns in dropped head syndrome according to prone-position cervical extension performance

Area of Science:

• Orthopedics
• Spinal Surgery
• Neuromuscular Disorders

Background:

• Dropped Head Syndrome (DHS) results from cervical extensor muscle (CEM) weakness, causing global imbalance.
• The precise link between CEM weakness and sagittal spinal alignment in DHS is not fully understood.

Purpose of the Study:

• To investigate the correlation between CEM weakness and global spinal posture in DHS patients.
• To clarify how varying degrees of CEM weakness influence spinal alignment parameters.

Main Methods:

• A cohort of 159 DHS patients was analyzed.
• CEM strength was assessed via cervical extension performance, classifying patients into Mild (MMT≥3) and Severe (MMT<3) DHS.
• Standing whole-body radiography was used to measure sagittal spinal alignment.

Main Results:

• Both Mild and Severe DHS groups showed positive correlations between chin-brow vertical angle (CBVA), cervical sagittal vertical axis (C-SVA), and thoracic kyphosis (TK).
• In Mild DHS, T1 slope (T1S) correlated positively with TK but not pelvic tilt (PT).
• In Severe DHS, T1S positively correlated with both TK and PT.

Conclusions:

• CEM weakness demonstrably affects global sagittal spinal posture in DHS.
• In severe CEM weakness (MMT<3), compensatory mechanisms shift from thoraco-lumbar segments to pelvic posterior tilt to manage head imbalance.