Cervical sagittal balance: a biomechanical perspective can help clinical practice

Area of Science:

• Orthopedics
• Spine Biomechanics
• Cervical Spine Surgery

Background:

• Cervical sagittal malalignment significantly impacts spinal mechanics and patient outcomes.
• Understanding the biomechanical consequences of malalignment is crucial for effective clinical management.

Purpose of the Study:

• To investigate the influence of cervical sagittal malalignment on cervical spine mechanics.
• To analyze the kinematic and kinetic responses to variations in C2-C7 Sagittal Vertical Alignment (SVA) and T1-Slope.

Main Methods:

• Ex vivo biomechanical laboratory model using human cervical spine specimens.
• Controlled variations in C2-C7 SVA and T1-Slope to simulate clinically relevant malaligned profiles.
• Maintenance of horizontal gaze to isolate the effects of sagittal imbalance.

Main Results:

• Increased C2-C7 SVA led to lower cervical flexion and suboccipital hyperextension to maintain horizontal gaze.
• Increased C2-C7 SVA expanded lower cervical neural foraminal areas, while increased T1-Slope reduced them.
• Forward head posture (FHP) was identified as a compensatory mechanism for radicular symptoms, involving muscle shortening and altered cervical spine kinematics.

Conclusions:

• Cervical sagittal malalignment significantly alters cervical spine biomechanics.
• Findings provide insights into the pathomechanics of forward head posture and its relation to neural foraminal dimensions.
• Consideration of cervical sagittal imbalance is vital for surgical planning, particularly in adjacent segment disease after fusion.