Lumbar facet orientation in spondylolysis: a skeletal study.
ABSTRACT Orientation of the lumbar articular facets at the L1-L5 level was measured and analyzed.
To characterize the relationship between lumbar facet orientation and isthmic spondylolysis.
Whereas many studies have explored the relationship between facet orientation in the transverse plane and various spinal pathologies, there is insufficient data regarding this relationship and isthmic spondylolysis.
A 3-dimensional digitizer was used to measure the transverse orientation of the lumbar facet joints at the L1-L5 level in 115 male individuals with bilateral isthmic spondylolysis (at L5) and 120 age and sex-matched normal control subjects from the Hamann-Todd Human Osteological Collection (Cleveland Museum of Natural History, Cleveland, OH). Statistical analysis included paired t tests and analysis of variance.
In both isthmic spondylolysis and control groups, considerable shifts were noticed from sagittally oriented articular facets at L1 to frontally oriented facets at L5. The change in orientation was significantly greater (up to 13 degrees at L4) in the isthmic spondylolysis group (right inferior facets). Three of the 4 articular facets of L5 (right and left inferior and right superior) were significantly more frontally oriented in isthmic spondylolysis compared to the control group. A greater tendency of asymmetry in facet orientation was noticed in the isthmic spondylolysis group.
Individuals with more frontally oriented facets in the lower lumbar vertebrae incorporated with facet tropism are at a greater risk for developing isthmic spondylolysis at L5.
- [show abstract] [hide abstract]
ABSTRACT: Skeletons of ancient Canadian Eskimos subjected to arctic weathering presented an unusual opportunity for direct observation of all stages of spondylolysis. To explore early stages of incomplete lysis, a phenomenon difficult to observe radiographically. Although lumbar spondylolysis most often appears to be a stress fracture that may proceed to complete separation, its early stages have been difficult to visualize. Vertebrae were examined for even minute lytic defects in the general region of pars interarticularis and the results were correlated with age at death. Spondylolysis was found in 51 individuals, with 110 separate sites (sides) affected. At 34 of these sites, all but two in adolescents or young adults, the lysis was incomplete. Incomplete lysis affected the superior margin of the neural arch more often than the inferior margin, and the right side more often than the left. Spondylolysis first became recognizable as incomplete stress fractures during adolescence, with most progressing to complete lysis in young adulthood. New fractures continued to develop in young adults, but most healed by middle adulthood. After 45 years of age, the overall frequency of spondylolysis declined, indicating that even complete defects occasionally healed.Spine 12/1995; 20(21):2328-34. · 2.16 Impact Factor
Article: Spondylolysis: a critical review.[show abstract] [hide abstract]
ABSTRACT: To provide an understanding of the current concepts in the natural history, pathophysiology, diagnosis, and treatment of spondylolysis based on the available medical literature. Articles were selected for review by the following methods: (a) MEDLINE searches with review of abstracts to select relevant articles; (b) review of multiple textbooks considered likely to contain information on spondylolysis; (c) review of references in articles identified by (a) and (b). Over 125 articles were ultimately reviewed fully. Publications were selected for inclusion in this article on the basis of perceived scientific and historical merit, particularly as thought to be relevant to achieving the stated purpose of this review. As no controlled clinical trials were identified, this could not be used as an inclusion criterion. Isthmic spondylolysis is considered to represent a fatigue fracture of the pars interarticularis of the neural arch. There is a relatively high incidence of radiographically identified spondylolysis in the general population, but the vast majority of these lesions probably occur without associated symptoms. Symptomatic pars lesions appear to be particularly a clinical problem in adolescents, especially adolescent athletes. The optimal diagnostic and treatment algorithms are not well identified in the current literature. Multiple imaging studies may have a role in the diagnosis of a pars lesion, and treatment seems likely to require at least relative rest and physical rehabilitation with consideration of bracing or, rarely, surgical intervention depending on the clinical context.British Journal of Sports Medicine 01/2001; 34(6):415-22. · 3.67 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This study examined the role of facet joint morphology in the etiology of both degenerative spondylolisthesis and isthmic spondylolysis. To this end, the axial facet joint morphology of the lower lumbar spine in a normal population and in populations of patients with spinal stenosis or degenerative spondylolisthesis at L4-5 and in patients with isthmic spondylolysis at the L5 level were characterized. Computed tomographic scans were digitized, defining the axial morphology of the normal facet joint at five stations from proximal to distal within the joint. Assessments were made of facet joint orientation, transverse articular dimension, depth of the articular surface, and shape of the articular surface at levels L3-4, L4-5, and L5-S1. There was a gradually more coronal orientation from proximal to distal among the stations at each level, and a maximal transverse articular dimension at the level of the superior endplate of the caudad vertebra. Minimal error in the recording process at this level. In addition to the maximal joint dimension, made this level the most representative of the overall morphology and most useful for further studies. At the L4-5 level, a significantly more sagittal facet orientation was found in the degenerative spondylolisthesis group when compared to both the normal population and spinal stenosis groups (P < 0.01). At L5-S1, the only significant morphologic difference between the normal population and the patients with isthmic spondylolysis was reduced transverse articular dimension. These results support the hypothesis that patients developing degenerative spondylolisthesis are predisposed to this by a developmental sagittal orientation of the L4-5 facet joints.Spine 01/1993; 18(1):80-91. · 2.16 Impact Factor
SPINE Volume 32, Number 6, pp E176–E180
©2007, Lippincott Williams & Wilkins, Inc.
Youssef Maher Masharawi, PhD,*† Deborah Alperovitch-Najenson, PhD,*†
Nili Steinberg, MSc,†? Gali Dar, MSc,†¶ Smadar Peleg, PhD,† Bruce Rothschild, MD, PhD,‡
Khalil Salame, MD,§ and Israel Hershkovitz, PhD†
Study Design. Orientation of the lumbar articular fac-
ets at the L1–L5 level was measured and analyzed.
Objective. To characterize the relationship between
lumbar facet orientation and isthmic spondylolysis.
Summary of Background Data. Whereas many studies
have explored the relationship between facet orientation
in the transverse plane and various spinal pathologies,
there is insufficient data regarding this relationship and
Methods. A 3-dimensional digitizer was used to mea-
sure the transverse orientation of the lumbar facet joints
at the L1–L5 level in 115 male individuals with bilateral
isthmic spondylolysis (at L5) and 120 age and sex-
matched normal control subjects from the Hamann-Todd
Human Osteological Collection (Cleveland Museum of
Natural History, Cleveland, OH). Statistical analysis in-
cluded paired t tests and analysis of variance.
Results. In both isthmic spondylolysis and control
groups, considerable shifts were noticed from sagittally
oriented articular facets at L1 to frontally oriented facets
at L5. The change in orientation was significantly greater
(up to 13° at L4) in the isthmic spondylolysis group (right
inferior facets). Three of the 4 articular facets of L5 (right
and left inferior and right superior) were significantly
more frontally oriented in isthmic spondylolysis com-
pared to the control group. A greater tendency of asym-
metry in facet orientation was noticed in the isthmic spon-
Conclusion. Individuals with more frontally oriented
facets in the lower lumbar vertebrae incorporated with
facet tropism are at a greater risk for developing isthmic
spondylolysis at L5.
Key words: facet orientation, isthmic spondylolysis,
transverse facet angle, lumbar vertebra. Spine 2007;32:
Lumbar isthmic spondylolysis is a defect in the pars inter-
articularis separating the vertebral arch into ventral and
dorsal parts, either unilaterally or bilaterally.1,2Strong he-
sis are suggested as possible causative factors.3–5While
many studies have explored the relationship between facet
architecture (particularly facet orientation and tropism)
and degenerative spondylolisthesis,6–11there is a dearth of
knowledge regarding the relationship with isthmic spon-
dylolysis. Ward and Latimer4demonstrated that normal
those with isthmic spondylolysis. Grobler et al6reported
that individuals with isthmic spondylolysis manifest re-
duced transverse articular dimension.
The aim of the current study was to characterize the
relationship between articular facet orientations and
isthmic spondylolysis in the lumbar spine.
Measurement of the transverse facet angle of all lumbar verte-
brae (T1–L5) was taken from 120 adult male skeletons with
normal spines and 115 with isthmic spondylolysis at L5, lo-
cated at the Hamann-Todd Human Osteological Collection
(Cleveland Museum of Natural History, Cleveland, OH) (Fig-
ure 1). The Hamann-Todd Human collection comprises ap-
proximately 3000 human skeletons of Caucasian and African-
American origin, born between 1825 and 1910 (mostly of low
socioeconomic status). All lumbar spines with bilateral spon-
dylolysis at L5 were visually identified and isolated. The sepa-
rated section of the neural arch at L5 was reattached to its
original location using adhesive Plasticine. Spines with isthmic
spondylolysis were compared to normal spines, and randomly
selected to fit the demographic structure (e.g., gender, ethnic-
ity) and body physique (e.g., stature, weight) of the spondylol-
spondylolysis group was 47.9 (13.8) and for the control 49.1
(17.1) (P ? 0.20). To control for spinal shape, we excluded
from the analysis all individuals with spondylo-arthropathies
and suspected abnormal kyphotic or scoliotic spine: the pres-
ence of apophyseal abnormalities associated with more than 5°
of anterior wedging in each of 3 adjacent vertebrae established
Scheuermann disease12,13; the presence of more than 3° of lat-
eral wedging in each of 3 adjacent vertebrae defined scoliosis14;
and kyphoscoliosis was diagnosed when a combination of an-
terior and lateral wedging was found within the same
One of the authors (Y.M.M.) took direct measurements us-
ing a Microscribe 3-dimensional (3-D) apparatus (Immersion
Co., San Jose, CA). The Microscribe 3-D is designed to create
3-D X, Y, and Z coordinate data for anatomic landmarks on a
From the *Spinal Research Laboratory, Department of Physical Ther-
apy, The Stanley Steyer School of Health Professions, Sackler Faculty
of Medicine, Tel-Aviv University, Ramat Aviv, Israel; †Department of
Anatomy and Anthropology, Sackler Faculty of Medicine, Tel-Aviv
University, Ramat Aviv, Israel; ‡The Arthritis Center of Northeast
Ohio, Northeastern Ohio Universities College of Medicine, Youngs-
town, OH; §Department of Neurosurgery, Tel Aviv Sourasky Medical
Center, Tel Aviv, Israel; ¶Department of Physical Therapy, Faculty of
Social Welfare and Health Sciences, University of Haifa, Israel; and
?The Zinman College of Physical Education and Sports Sciences at the
Wingate Institute, Israel.
The manuscript submitted does not contain information about medical
No funds were received in support of this work. No benefits in any
form have been or will be received from a commercial party related
directly or indirectly to the subject of this manuscript.
Address correspondence and reprint requests to Youssef Maher
Masharawi, PhD, Physical Therapy, Anatomy and Anthropology, Tel-
Aviv University, University Campus, Lebanon St., Ramat Aviv, Tel-
Aviv, Israel 69978; E-mail: email@example.com
vertebra. A special metal device was used to stabilize properly
the vertebrae.15,16The vertebra was grasped and pressed to-
ward the body’s superior and inferior articular surface, subse-
quently turned 90° so that the articular body surfaces were
located laterally and the vertebral spinous process posteriorly,
After calibrating the XYZ coordinates of a fixed origin point to
0, 0, and 0, respectively, the telescopic stylus of the apparatus
was positioned at each of the defined anatomic landmarks on
the vertebrae. A foot pedal (connected to the Microscribe) was
then pressed, entering the data into a previously designed Excel
program (Microsoft, Corp., Redmond, WA), thus calculating
the defined measurements using inserted formulas. The posi-
tion resolution and accuracy of the apparatus as defined by the
manufacturer are 0.13 and 0.43 mm (mean values), respec-
Descriptive statistics were carried out for all measurements
in all vertebrae. Analysis of variance examined the differences
between spondylolytic and normal spines. Before this test, the
Kolmogorov-Smirnov test was used to check whether the data
were normally distributed. The intraclass correlation coeffi-
cient was employed to determine the intratester and intertester
reliability of the measurement (repeated measurements of 15
vertebrae). An intraclass correlation coefficient of ?0.75 was
considered good reproducibility, ?0.75 poor reproducibility.
One of the authors (Y.M.M.) assessed the intratester reliability
of the measurement taken. Measurements were taken twice
with a 3.5-day separation. Intertester reliability involved 2
testers (Y.M.M. and I.H.) who carried out the measurements
using the same method within a 20-minute period. Both testers
were blinded to the results of the measurements.
To estimate reliability of the adhesion procedure, the same
author (Y.M.M.) performed twice (at a weekly interval) the
attachment process. A second author (I.H.) subsequently took,
reassembled, and measured measurements again for the third
time. Calculating the Pearson correlation coefficients between
the angles obtained via the Microscribe-3-D apparatus and
those obtained with a goniometer tested the validity of the
The means and SDs of the transverse facet angle for all
lumbar vertebrae are presented in Table 1. The preva-
lence of spondylolysis in the Hamann-Todd Human
adult (?20 years) male sample (total 2374) was 4.6%.
No significant differences in spondylolysis prevalence
were found between the age cohorts (10-year interval),
varying from 2.2% to 7.6%. Females were excluded
from the current analysis due to small sample size (only 6
females out of 700 manifested isthmic spondylolysis).
Both the intratester and intertester reliability for all mea-
surements were very high: intratester 0.96 ? intraclass
correlation coefficient ?0.98 and intertester 0.82 ? in-
traclass correlation coefficient ?0.89. The adhesive pro-
cedure did not contribute to the variation of the traits
tween intraclass correlation coefficient ? 0.94 and intra-
class correlation coefficient ? 0.89, respectively). Valid-
ity was also high (r ? 0.98; P ? 0.0001). All P values for
the Kolmogorov-Smirnov test were greater than 0.05,
indicating normal distribution of all variables.
Figure 1. Illustrations and defini-
tions of transverse facet angle.
Table 1. Means of Facet Orientations in the Lumbar Region in Normal and Spondylolytic Spines
L1L2 L3 L4L5
Mean ? SD (mm)Mean ? SD (mm)Mean ? SD (mm)Mean ? SD (mm) Mean ? SD (mm)
Left superior transverse
Left inferior transverse
Right inferior transverse
29.0 ? 12.5
28.9 ? 16.7
27.1 ? 10.8
30.0 ? 17.6
23.7 ? 10.9
20.8 ? 12.6
22.9 ? 10.3
23.3 ? 15.9
27.5 ? 8.7
24.4 ? 11.7
28.9 ? 10.5
27.8 ? 15.3
36.1 ? 11.1
34.1 ? 13.3
36.9 ? 12.0
38.7 ? 14.2
47.1 ? 13.0
48.0 ? 15.3
41.9 ? 12.4
49.9 ? 19.04
24.6 ? 10.9
21.4 ? 16.3
25.9 ? 10.4
28.3 ? 12.1
27.0 ? 11.7
28.6 ? 14.3
30.0 ? 12.2
32.5 ? 18.1
37.5 ? 10.9
35.9 ? 14.2
38.9 ? 11.8
43.5 ? 16.2
44.8 ? 8.5
48.2 ? 15.5
45.5 ? 10.3
58.4 ? 14.2
45.3 ? 8.1
53.4 ? 11.4
47.7 ? 10.2
57.0 ? 5.0
Means in bold are significantly greater (P ? 0.05).
E177 Lumbar Facet Orientation in Spondylolysis•Masharawi et al
The transverse angles of both superior and inferior
articular facets increased from L1 to L5, in both isthmic
spondylolysis and normal groups (by 17° to 35°) (Table
1). This change caused a considerable shift in the orien-
tation of the articular facets, from a more sagittal orien-
tation to a more frontal one. The change in orientation
was significantly greater (up to 13° at L4) in the isthmic
spondylolysis group (right inferior facets) (Table 1). At
L5, 3 of the 4 articular facets (right and left inferior and
right superior) manifested a significantly greater frontal
orientation compared to the norm. The number of asym-
metrical facet orientation (i.e., facet tropism) in the lum-
bar spine doubled in the isthmic spondylolysis group
We demonstrate herein that compared to the norm, the
facets of the lower lumbar vertebrae in isthmic spondylol-
ysis are more frontally oriented (i.e., more pronounced on
the right inferior side). Lumbar facet orientation is com-
in association with pathologic conditions. In a normal
state, the sagittally oriented lumbar facets facilitate antero-
posterior movement (flexion and extension of spine) while
limiting axial rotation.17During flexion and extension, the
laris, increases from L1 to L5.18In pathologic conditions,
sagittally compared to the norm. In degenerative spon-
dylolisthesis, for example, the articular facet joints of the
lower lumbar vertebrae are more sagittally oriented than
the norm, thus facilitating their forward slippage (spon-
dylolisthesis), particularly in L5.6–11Similarly in isthmic
joint surface area during sagittal movements (both in flex-
ion and extension) (Figures 2, 3). If long enough or repeti-
tive force is applied on these reoriented joint surface areas,
fatigue fractures in the shape of isthmic spondylolysis can
occur.3,19–21It is essential to point out, however, that isth-
mic spondylolysis is multifactorial in nature, developing
during adolescent life, as indicated by the prevalence of
isthmic spondylolysis in the age cohorts and literature. As
such, the key point in understanding isthmic spondylolysis
is not “which comes first” but, rather, the interaction be-
tween the various factors associated with isthmic spon-
dylolysis during growth and development.
These factors may be grouped into 4 clusters: (1) an-
atomic, namely, size and shape of the vertebrae (e.g.,
interfacet width4); (2) developmental, congenital, or he-
reditary in nature (e.g., a congenital disturbance in ossi-
fication22,23); (3) spinal alignment (e.g., pelvic inci-
dence5); and (4) activity, stress intensity and movements
(e.g., gymnastic24,25). Although each cluster may inde-
pendently enhance mechanical stress on the lumbar ver-
tebra, leading to isthmic spondylolysis, it is the nature
and intensity of the interaction between the elements in
the 4 clusters that greatly intensify during growth and
will eventually determine if isthmic spondylolysis will
develop (Figure 4).
Why are the majority of spondylolytic cases found at
and L4? We believe that in isthmic spondylolysis pa-
tients, several factors work jointly to elevate the stress on
the pars interarticularis of L5. Kapandji17established
that the pronounced inclination of the superior surface
Table 2. Paired t Test for Left and Right Facet Asymmetry in Normal and Spondylolytic Lumbar Spines
MeasurementGroups L1L2L3 L4 L5
Lt ? Rt
Rt ? Lt
Rt ? Lt
Rt ? Lt
Rt ? Lt
Rt ? Lt
Rt ? Lt
Rt ? Lt
Lt ? Rt
? and ? ? significant difference exists (P ? 0.05).
Lt indicates left; NS, nonsignificant; Rt, right.
Figure 2. In the normal condition (A), the sagittaly oriented lumbar
facets facilitate flexion and extension of spine while limiting axial
rotation. In ISP (B), the more frontally oriented lumbar facets
results in a greater amount of joint surface area during sagittal
movements if long enough or repetitive, can end with fatigue
fractures in the shape of ISP at L5.
E178 Spine•Volume 32•Number 6•2007
This sliding mechanism is successfully counterbalanced
by the locking mechanism of the lumbosacral joint, ac-
tively by the muscles and passively by the shape of the
joint and attached ligaments. These 2 counteracting
forces (the sliding of L5 and counterforce of the lumbo-
sacrum region) act through a point located at the verte-
bral isthmus.17Excessive frontal orientation of the infe-
rior facets of L5 in isthmic spondylolysis patients (57° on
the right side and 56° on the left) tightly binds the verte-
joint), thereby minimizing forward displacement of the
vertebra and intensifying the accumulative stress on the
pars interarticularis (due to a larger contact area) (Figure
3). It should be noted that at L5, only in the left superior
facet, the transverse orientation was similar in both the
normal and spondylolysis group. This, however, reflects
a pathologic condition in the isthmic spondylolysis
group, as in the normal condition, right and left articular
facets differed (i.e., the left was frequently more frontally
oriented [47°] than the right [42°]). This asymmetry in
facet orientation may facilitate 3-D combined movement
in the normal lower lumbar spine.15Only in the patho-
logic condition (isthmic spondylolysis) were both facets
similarly oriented (48° and 49°).
Numerous researchers have debated the impact sacral
orientation (sacral inclination; pelvic incidence), me-
chanical, morphologic, and pathologic aspect of the
spine. Duval-Beaupere et al,26for example, found a
significant correlation between pelvic shape and sagit-
tal curves of the spine in a normal population. Labelle
et al5reported a significantly greater pelvic incidence,
sacral slope, pelvic tilt, and lumbar lordosis in spon-
dylolisthesis compared to the norm. These findings
support our mechanical interpretation of isthmic
It is hypothesized that during lumbar flexion, the
movement of L4 is greatly limited by the frontal orienta-
articular processes of L4–L5 (i.e., zygapophyseal joint)
remain in tight contact leading to increased mechanical
stress over the pars interarticularis region of L5 (Figure
3). During extension (i.e., lumbar hyperlordosis), the
compressive forces acting on the facet joints of L4–L5
(already intensified due to frontally oriented facets) from
1 side and the counter-reactive forces acting on the facet
joint of L5–S1 from the other side, intensify the shearing
force developing in the pars interarticularis of L5 (Figure
3). Additionally, since there is greater joint contact at
the L5–S1 joints in isthmic spondylolysis individuals
(due to more frontally oriented facets), the mechanical
necessity of the iliolumbar ligament to resist the ante-
rior sliding of L5 is diminished, thus further increasing
the mechanical stress on the bony restraints (the facets
and pars interarticularis region). This stress is proba-
bly further intensified during forced flexion and exten-
Figure 3. With the pronounced inclination of the sacrum, L5 tends
to slide forward. This sliding is counterbalanced by the locking
mechanism of the lumbo-sacral joint both actively by the muscles
and passively by the L4 “ISP morphological characteristics”, ex-
cessive frontal orientation of L5 and the attached ligaments. When
these forces act long enough or repetitively through the vertebral
isthmus, it can end with fatigue fractures in the shape of ISP at L5.
Figure 4. The external circle includes the four major factors as-
sociated with ISP (bold) and their components. These factors
independently or in combination account for the increased load on
the lower lumbar vertebrae and ultimately lead to increased stress
(second circle) at the pars interarticularis. During growth (third
circle) this stress is being further intensified (expressed as larger
arrows) and may ultimately lead to ISP (inner circle). In this model
the association between ISP and factors are not unilateral but
bilateral (as expressed by the bilateral arrows), indicating the lack
of “cause and effect” relationship. The circular format of the
model emphasis our concept that there is no dominant factor for
ISP (four categories), and that an interaction between the factors
E179 Lumbar Facet Orientation in Spondylolysis•Masharawi et al
sion of the spine. Finally, the greater tendency of tro-
pism in facet orientation at the L4–L5 zygapophyseal
joint in isthmic spondylolysis individuals compared to
the norm may create a torsional effect on the pars
interarticularis, giving the lysis its commonly seen
Excessive frontal orientation and tropism of the lower
lumbar facets are strongly associated with isthmic spon-
● Lower lumbar facets in isthmic spondylolysis are
more frontally oriented compared to the norm.
● At L5, 3 of the 4 articular facets manifest a sig-
nificantly greater frontal orientation compared to
● Asymmetry in lumbar facet orientation is a char-
acteristic in isthmic spondylolysis.
The authors would like to thank Prof. Bruce Latimer and
ural History, Cleveland, Ohio, for their support and as-
sistance in using the invaluable Hamman-Todd Osteo-
logical Collection; Mrs. Ana Bachar, Department of
Anatomy and Anthropology, Sackler Faculty of Medi-
cine, Tel-Aviv University, for her tremendous assistance
in preparing the figures; Mrs. Phyllis Curchack Korns-
pan for her editorial assistance.
Eskimo skeletons. Spine 1995;20:2328–34.
2. Standaert C, Herring S. Spondylolysis: A critical review. Br J Sports Med
3. Wiltse LL, Widell EH Jr, Jackson DW. Fatigue fractures the basic lesion in
isthmic spondylolisthesis. J Bone Joint Surg Am 1975;57:17–22.
4. Ward C, Latimer B. Human evolution and the development of spondylolysis.
5. Labelle H, Roussouly P, Berthonnaud E, et al. Spondylolisthesis, pelvic inci-
dence, and spinopelvic balance. Spine 2004;29:2049–54.
6. Grobler L, Robertson P, Novotny J, et al. Etiology of spondylolisthesis.
Assessment of the role played by lumbar facet joint morphology. Spine 1993;
7. Dai L. Orientation and tropism of lumbar facet joints in degenerative spon-
dylolisthesis. Int Orthop 2001;25:40–2.
8. Sato K, Wakamatsu E, Yoshizumi A, et al. The configuration of the laminas
and facet joints in degenerative spondylolisthesis. A clinicoradiologic study.
9. Cinotti G, Postacchini F, Fassari F, et al. Predisposing factors in degenerative
spondylolisthesis: A radiographic and CT study. Int Orthop 1997;21:337–42.
10. Kim N, Lee J. The relationship between isthmic and degenerative spondylolis-
thesis and the configuration of the lamina and facet joints. Eur Spine J 1995;4:
11. Nagaosa Y, Kikuchi S, Hasue M, et al. pathoanatomic mechanisms of de-
generative spondylolisthesis: A radiographic study. Spine 1998;23:1447–51.
12. Scoles P, Latimer B, DiGiovanni B, et al. Vertebral alterations in Scheuer-
mann’s kyphosis. Spine 1991;16:509–15.
13. Sorenson K. Scheuermann’s Juvenile Kyphosis. Clinical Appearances, Radi-
ology, Aetiology, and Prognosis. Copenhagen: Munksgaard; 1964.
14. Boachie-Adjei O, Lonner B. Spinal deformity. Pediatr Clin North Am 1996;
15. Masharawi Y, Rothschild B, Dar G, et al. Facet orientation in the thoraco-
lumbar spine: Three-dimensional anatomical and biomechanical analysis.
16. Masharawi Y, Rothschild B, Salame K, et al. Facet tropism and interfacet
shape in the thoraco-lumbar vertebrae: Characterization and biomechanical
interpretation. Spine 2005;30:E281–92.
17. Kapandji I. In: The Physiology of the Joints: the Trunk and the Vertebral
Column. London: Longman Group; 1972:9–168.
18. Dietrich M, Kurowski P. The importance of mechanical factors in the etiol-
spine. Spine 1985;10:532–42.
19. Ciullo J, Jackson D. Pars interarticularis stress reaction, spondylolysis, and
spondylolisthesis in gymnast. Clin Sports Med 1985;4:95–110.
protocol for non operative treatment. J Spinal Disord 1993;6:406–11.
21. Gerbino P, Micheli L. Back injuries in the young athlete. Clin Sports Med
22. Brocher I. Die pathogenesis der spondylolisthesis mit besonderer berucksich-
tigung ihrer beziehung zur unfallheilkunde. Langenbecks Arch Surg 1953;
23. Taillard W. Spondylolisthesis in children and adolescents. Acta Orthop
24. Congeni J, McCulloch J, Swanson K. Lumbar spondylolysis. A study of
natural progression in athletes. Am J Sports Med 1997;25:248–53.
25. Soler C, Calderon T. The prevalence of spondylolysis in the Spanish elite
athlete. Am J Sports Med 2000;28:57–62.
26. Duval-Beaupere G, Schmidt C, Cosson P. A barycentremetric study of the
sagittal shape of spine and pelvis: The conditions required for an economic
standing position. Ann Biomed Eng 1992;20:451–62.
E180 Spine•Volume 32•Number 6•2007