Prevalence of Poor Bone Quality in Women Undergoing Spinal Fusion Using Biomechanical-CT Analysis.
METHODS
Retrospective, cross-sectional analysis of vertebral bone quality in spine-fusion patients at a single medical center.


OBJECTIVE
To characterize the prevalence of osteoporosis and fragile bone strength in a spine-fusion population of women with an age range of 50 years to 70 years. Fragile bone strength is defined as the level of vertebral strength below which a patient is at as high a risk of future vertebral fracture as a patient having bone density-defined osteoporosis.


BACKGROUND
Poor bone quality--defined here as the presence of either osteoporosis or fragile bone strength--is a risk factor for spine-fusion patients that often goes undetected but can now be assessed preoperatively by additional postprocessing of computed tomography (CT) scans originally ordered for perioperative clinical assessment.


METHODS
Utilizing such perioperative CT scans for a cohort of 98 women (age range: 51-70 yr) about to undergo spine fusion, we retrospectively used a phantomless calibration technique and biomechanical-CT postprocessing analysis to measure vertebral trabecular bone mineral density (BMD) (in mg/cm³) and by nonlinear finite element analysis, vertebral compressive strength (in Newtons, N) in the L1 or L2 vertebra. Preestablished validated threshold values were used to define the presence of osteoporosis (trabecular BMD of 80 mg/cm³ or lower) and fragile bone strength (vertebral strength of 4500 N or lower).


RESULTS
Fourteen percent of the women tested positive for osteoporosis, 27% tested positive for fragile bone strength, and 29% were classified as having poor bone quality (either osteoporosis or fragile bone strength). Over this narrow age range, neither BMD nor vertebral strength were significantly correlated with age, weight, height, or body mass index (P values 0.14-0.97 for BMD; 0.13-0.51 for strength).


CONCLUSIONS
Poor bone quality appears to be common in women between ages 50 years and 70 years undergoing spinal fusion surgery.


METHODS
3.
*Department of Orthopedic Surgery, University of California, San Francisco, CA†O.N. Diagnostics, Berkeley, CA‡Departments of Mechanical Engineering and Bioengineering, University of California, Berkeley, CA.
Shane
S
Burch
Michael
M
Feldstein
Paul F
PF
Hoffmann
Tony M
TM
Keaveny
D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D015995:Prevalence; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*