Effect of sagittal alignment on kinematic changes and degree of disc degeneration in the lumbar spine: an analysis using positional MRI.
METHODS
Retrospective analysis using positional MRI.


OBJECTIVE
To determine the effects of total sagittal lordosis on spinal kinematics and degree of disc degeneration in the lumbar spine.


BACKGROUND
Changes in sagittal lordosis alter the load on the spine and may affect spinal mobility. There is increasing recognition of the clinical impact that sagittal alignment has on back pain, especially its possible role in accelerating adjacent segment degeneration after spinal fusion. However, its relationship to segmental mobility and degeneration of the lumbar spine has yet to be determined.


METHODS
Four hundred and thirty patients who had low back pain with or without leg pain (241 males and 189 females) with a mean age of 42.98 years (range, 16-85 years) were included. Total sagittal lordosis (T12-S1) was divided into three groups; Group A: Straight or Kyphosis (<20°, n = 84), Group B: Normal lordosis (20-50°, n = 294), and Group C: Hyperlordosis (>50°, n = 52). The degree of disc degeneration was graded using midsagittal T2-weighted MR images. Segmental mobility, including translational motion and angular variation, was measured using positional MRI. Their relationship with total segmental lordosis was identified.


RESULTS
When compared with group B, the segmental motion in group C tended to be lower at the border of lordosis and higher at the apex of lordosis, with a significant difference in angular motion at L2-L3. The contrary finding was identified in group A, which had a higher segmental motion at border segments and lower motion at apical segments of lordosis, with significant difference of translational motion at L3-L4 and angular motion at L1-L2. Apical segments contributed more, whereas border segments contributed less to the total angular mobility in more lordotic spines. The opposite was seen in more kyphotic spines. Disc degeneration tended to be greater at all levels in group C, and at L1-L2 and L5-S1 in group A.


CONCLUSIONS
Changes in sagittal alignment may lead to kinematic changes in the lumbar spine. This may subsequently influence load bearing and the distribution of disc degeneration at each level. Sagittal alignment, disc degeneration, and segmental mobility likely have a reciprocal influence on one another.
Department of Orthopaedics, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
Gun
G
Keorochana
Cyrus E
CE
Taghavi
Kwang-Bok
KB
Lee
Jeong Hyun
JH
Yoo
Jen-Chung
JC
Liao
Zhiqiang
Z
Fei
Jeffrey C
JC
Wang
D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D018450:Disease Progression; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000209:etiology / Q000503:physiopathology*; D008141:Lordosis / Q000150:complications / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D055009:Spondylosis / Q000209:etiology / Q000503:physiopathology*; D055815:Young Adult