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Morphometry of human lumbar apophyseal joints. A novel technique
M W Swanepoel1, L M Adams, J E Smeathers
1School of Mechanical Engineering, University of the Witwatersrand, Wits, Republic of South Africa. MSWAN@Hertz.mech.Wits.ac.ZA
Study Design:
The anatomy of cadaveric lumbar apophyseal joints was examined as part of a study of possible correlations between lumbar apophyseal morphology, arthrosis, and cartilage thickness and stiffness.
Objectives:
To establish the morphometry of human upper lumbar apophyseal joints using an objective technique.
Summary Of Background Data:
The apophyseal joints of 30 unfixed lumbar motion segments, all from different cadavers (24 male, five female, and one unknown, mean age 35 years, range 16-78 years) were exposed by dissection and disarticulation. Twenty-five motion segments were L1-L2, three were L2-L3, and two were L3-L4. The extent of fibrillation and linear dimensions of 29 of these specimens were examined, whereas the vertebrae and joints of 22 of them (18 being L1-L2) were cast in araldite resin.
Methods:
The casts of the vertebrae were sectioned cephalocaudally at 1-mm intervals. Image processing of photographic slides of the sections established the orientations and dimensions of the lumbar apophyseal joints and their shapes using Fourier analysis.
Results:
Apophyseal joint surface area was 158 +/- 43 mm2, cephalocaudal length 15.2 +/- 2.7 mm, and straight line length between anterior and posterior borders was 13.2 +/- 1.9 mm. The joints were orientated at 62.5 +/- 11.8 degrees to the coronal plane. Average maximum depth of concavity was 1.8 +/- 0.7 mm. The posterior edges of two joint pairs twisted inward toward the midsagittal plane in a cephalocaudal direction; thus, some apophyseal joints bear part of the axial spinal load. The right inferior surfaces were more elongated cephalocaudally (but not longer) than their contralateral partners. Inferior apophyses were significantly more elongated cephalocaudally (but not longer) than their ipsilateral articulating superior surfaces.
Conclusions:
In theory, Fourier analysis of joint surfaces was objective, but it dictated the criterion by which joints were grouped; care must be exercised so that measurement methods do not categorize joints artificially. "Symmetry" is too subjective to be applied to contralateral apophyseal joints; correlation coefficients should be quoted for areas and orientations. The morphology of contralateral lumbar apophyseal joint pairs was significantly correlated in all respects, as was the morphology of articulating lumbar apophyseal surfaces.