Lumbar facet anatomy changes in spondylolysis: a comparative skeletal study.
Opinions differ as to the exact mechanism responsible for spondylolysis (SP) and whether individuals with specific morphological characteristics of the lumbar vertebral neural arch are predisposed to SP. The aim of our study was to reveal the association between SP and the architecture of lumbar articular facets and the inter-facet region.


METHODS
Using a Microscribe three-dimensional apparatus (Immersion Co., San Jose, CA, USA), length, width and depth of all articular facets and all inter-facet distances in the lumbar spine (L1-L5) were measured. From the Hamann-Todd Human Osteological Collection (Cleveland Museum of Natural History, OH, USA) 120 normal male skeletons with lumbar spines in the control group and 115 with bilateral SP at L5 were selected. Analysis of variance was employed to examine the differences between spondylolytic and normal spines.


RESULTS
Three profound differences between SP and the norm appeared: (1) in individuals with SP, the size and shape of L4's neural arch had significantly greater inter-facet widths, significantly shorter inter-facet heights and significantly shorter and narrower articular facets; (2) only in the L4 vertebra in individuals with SP was the inferior inter-facet width greater in size than the superior inter-facet width of the vertebra below (L5) (38.7 mm versus 40 mm); (3) in all lumbar vertebrae, the right inferior articular facets in individuals with SP were flatter compared to the control group.


CONCLUSIONS
Individuals with L4 "SP" characteristics are at a greater risk of developing fatigue fractures in the form of spondylolysis at L5.
Masharawi
Youssef
Y
Spinal Research Laboratory, Physical Therapy, The Stanley Steyer School of Health Professions, Sackler Faculty of Medicine, Tel-Aviv University, P.O. Box 39040, 69978 Tel-Aviv, Israel. yossefm@post.tau.ac.il
Dar
Gali
G
Peleg
Smadar
S
Steinberg
Nili
N
Alperovitch-Najenson
Dvora
D
Salame
Khalil
K
Hershkovitz
Israel
I
D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D013169:Spondylolysis / Q000453:epidemiology / Q000473:pathology*; D021801:Zygapophyseal Joint / Q000473:pathology*