Page 10 P H Y S I O T H E R A P Y JUNE, 1972 ANATOMICAL ASPECTS OF SOME VERTEBRAL ANOMALIES E. J. WOOD Lecturer in Physiotherapy, University o f Cape Town. During a course o f study in the Anatomy Department of the University of Cape Town under Professor Wells, speci­ mens of vertebral anomalies were worked on and I thought they would be of interest to physiotherapists as some of them must undoubtedly have given rise to symptoms of backache. As the causation of some of these conditions are develop­ mental a little background embryology is necessary to discussing the anomalies themselves. EMBRYOLOGY After differentiation of the cells of the embryo into the three layers of ectoderm, mesoderm and entoderm, and the formation of the neural tube for the spinal cord with the notochord (a structure running the length o f the embryo) lying beneath it, a condensation of mesodermal cells comes to lie beneath and lateral to the neural tube. These cells migrate around the tube to form the first template, as it were, o f the neural arch. Cells below the tube move medially and condense to form the pattern of the vertebral body, enclosing the notochord. Longitudinally this mass is marked off into segments of dense and less dense cell masses. mesoderm notochord Fig. 1. Diagramatic cross-section embryo showing migrating mesoderm. When the embryo is about five weeks old, these primitive mesenchymal cells, as they are now called, start to form cartilage. There is a pattern of chondrification which is closely allied to that of later ossification, with centres appearing in the body, one on either side of the neural arch and one for the lateral costal process on each side making five centres in all for each vertebra. Once the mesenchymal model has all been converted to cartilage the process of ossification commences with invasion o f the cartilage by blood vessels, the dying off of the cartilage and its replacement by bone. As stated before, the centres of ossification correspond to those of chondrification i.e. one for the body, two for each neural arch in the cervical and lumbar region and an additional two for the costal elements only in the thoracic region, C7 and sacral region. The ossification of the atlas and axis vertebrae are not discussed here. I s the thoracic region these costal elements ultimately form the ribs. In the sacrum they unite first to the transverse processes then the two unite to the body of the vertebra and finally they fuse longitudinally to form the lateral nfass of the sacrum. Much controversy surrounds the ossification centres of the costal elements, some authors stating that they occur in all vertebrae, and that the anterior part of the lateral process of the cervical vertebra has a separate centre o f ossification corresponding to the costal process in the thoracic region. The anatomical terminology for this part of the process is the costal element and seems to have derived either from an early concept of separate centres as stated above or because it corresponds to the same process in some reptiles. To add to the confusion, in the lumbar region the costal element is said to have fused to the transverse process to form the lateral process, but how much is costal process and how much transverse process is another matter for keen debate. General concensus o f opinion would seem to favour ossification centres for costal elements for thoracic, lower cervical, sacral and perhaps L5, while for descriptive purposes there remains an area by this name for each vertebra. The centres for the bodies appear first and then those for the neural arches and costal elements. By birth all centres of ossification are present and well established, with a layer of cartilage separating neural arch in the midline posteriorly, and neural arch from body on either side anteriorly. The transverse processes grow out from the neural arch as do the articular processes. v e r t e o r a at b ir t h e p ip h y s e s Fig. 2. Diagram of vertebra at birth and epiphyses at puberty. Fusion, i.e. complete bony bridging of the neural arches occurs progressively up to three years of age and fusion of the neural arches to the body occurs between 3 and 7 years. At puberty secondary ossification centres appear on the tips of the spinous processes, the transverse processes and on the inferior and superior surfaces of the body—here in the form of a peripheral ring of ossification. These secondary centres fuse to the main part of each vertebra at about 25 years of age. The sacrum is a little more involved with longitudinal fusing of costal elements to form the lateral mass and a merging of secondary centres to form the auricular epiphy­ seal plate for the sacro-iliac joint and the tubercles. The bodies also fuse from below upwards to form the mass of the SEGMENTATION AND FORMATION OF INTER­ VERTEBRAL DISC Longitudinally the original mesoderm mass shows succes­ sive areas of dense and less dense cells, giving a segmental pattern. A division occurs in the dense areas and they form cranial and caudal halves. Each vertebral body is made up of a cranial and a caudal part of two segments. The dense areas left become the intervertebral disc. v e rte b ral body Fig. 3. Diagram of formation of vertebral body from original mesoderm segments. It will be remembered that the cells forming the body surrounded the notochord and this structure regresses, remaining only in the centre of the intervertebral disc as the nucleus pulposus. This nucleus is at first a mucoid substance which is gradually replaced by fibro-cartilage, remaining semi-fluid in the young and thus freely adaptive to movement. In the middle-aged and elderly more replacement by fibro- cartilage renders it less adaptable and more susceptible to degeneration. iRe pr od uc ed b y Sa bi ne t G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) JUNE, 1972 P H Y S I O T H E R A P Y Page 11 The conversion of the mesenchymal cells surrounding the nucleus to fibro-cartilage forms the annulus fibrosus. Of interest is the fact that the nucleus pulposus lies more posteriorly than centrally, due to growth of the vertebral body anteriorly with the posterior part of the annulus therefore thin and weaker than the anterior part. Also, with the development of the cervical and lumbar curves, the disc becomes compressed posteriorly, further weakening the annulus as unsupported fibrous tissues, i.e. not in a bony matrix can withstand tensile force but not compression. These two factors predispose to injury and degeneration of the fibres of the annulus in this region. The Ilium With its three centres of ossification, this bone is formed from a condensation of mesenchyme. The superior part lies opposite vertebral segments 21-23, and moves down to lie opposite segment 25, making this vertebra the most usual sacral I, with 24 pre-sacral vertebrae formed by the well- known regions into seven cervical, twelve thoracic and five lumbar. LIGAMENTS These are well known, being divisible into: (a) Longitudinal group—anterior and posterior on bodies, attached to the intervertebral discs, and the supraspinous ligament attached along the tips of the spinous processes. (b) Intervertebral group—the ligamentum flavum uniting lamina to lamina anteriorly and being highly elastic is the most important of these. The spines and transverse processes are also united by interspinous and intertransverse ligaments, leaving only pedicles un-united to allow the passage of spinal nerves. (c) Articular capsules—surrounding the joints of the vertebral arches. (d) Lumbo-sacral region—the additional anterior, posterior and interosseous sacro-iliac ligaments stabilise the area. The tendency of L5 to be displaced forward on the sacrum due to the weight of the body and the backward angulation of the sacrum at this point is counteracted by the strong ilio-lumbar ligament running from the transverse processes of L5, to the iliac crest. MUSCLES These are numerous and rather complicated in their arrangement. They appear to form a deep group of small muscles more or less from vertebra to vertebra; an inter­ mediate group of longer muscles bridging 4-6 vertebra and a superficial group forming long columns successively up the back. From a functional point of view, the deep muscles would be fitted more for balance adjustment vertebra on vertebra, with the superficial group responsible for grosser movements of the trunk. The intermediate group could assist in both functions. The names and arrangements of these muscles can be found in any recognised textbook of anatomy. Of interest is recent work by Professor Trevor Jones showing a wedge of muscle, made up of successive laminae uniting the spitious .and transverse processes of the lumbar spine individually to the sacrum and iliac crest. This arrange­ ment further supports the vulnerable lumbo-sacral and sacro-iliac region. BONY ABNORMALITIES This term refers here to some developmental anomalies and functional conditions and not to gross pathological deformi­ ties. Levels of Incidence It would appear that where the character of the vertebra •s changing from one form to another, the likelihood of abnormality is greatest. Sacral I is the vertebra with the highest incidence o f abnormality with the other regional junctions of C l, C7 and T l, T12 and LI following with varying degrees of incidence. DEVELOPMENTAL ANOMALIES Spina Bifida Non-union of the neural arch posteriorly accounts for this condition. The cleft is usually through the middle of the process, the two sides being symmetrical. If the cleft is paramedian, the preponderence of bone tends to be on the right side. The incidence of this condition is said to be in the region of 1 ,2 % which although not high, is higher than most of the other conditions. This slight bony defect is of no great clinical significance but must weaken ligamentous support, particularly in the lumbo-sacral region. Where there is gross separation of the arches and herniation o f the cord and meninges, meningomyelocoel results with all its complications and problems. It is thought to be lack of initial chondrifi- cation and therefore no final ossification. Fig. 4. Drawing from specimens of spina bifida. Absence of Spinous Process This may be associated with the above condition or the neural arch may have fused but no spinous process formed. Once again ligamentous and muscular support is weakened. Cervical and Lumbar ribs C7 and LI occasionally have costal elements actually forming a small rib which may be completely separated from the vertebra by synovial joints or partly or completely fused to it. In the cervical region symptoms arise from stretching of the brachial plexus over this rib with perhaps vascular symptoms as well from stretching of the subclavian artery. Fig. 5. Drawing from specimen of cervical rib and diagramatic representation of kinking of subclavian artery and brachial plexus by the rib. Wedged and Hemivertebrae Although not common these two conditions lead to either a kyphosis or scoliosis. Wedging of the anterior body of the vertebra is the cause of the former and failure of one half of the body to develop causes the latter. This defect appears to be an early fault in the laying down of the mesodermal model. Foramina A foramen may be present in the lateral mass of SI or in L5 which appears to be rather akin to the transverse foramen for the vertebral artery in the cervical region. This is formed by a vascular anastomosis in the cartilage model causing rarefraction. Various abnormalities occur in the lateral process of the cervical vertebra with failure to form the complete foramen either anteriorly or posteriorly, or with narrowing of the foramen. This could cause vascular symptoms affecting the vertebral artery. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) Page 12 P H Y S I O T H E R A P Y JUNE, 1972 Abse nt A n t e r i o r A r c h o f th e A tl as In o n e s p e c i m e n c o m p l e t e f a i l u re o f t he a n t e r i o r a r c h o f th e A t l a s w as se en. T h e s p e c i m e n w a s o f a fi ve -y ea r-o ld ch il d a n d it is po ss ib le t h a t t h e r e w as h y p e r m o b i l i t y in t h e a r e a . T h e r e a l s o a p p e a r s t o be fa i l u re o f the p o s t e r i o r a r c h t o un it e a n d a d ef ec t in th e c o s t a l e l e m e n t s f o r m i n g t h e t r a n s v e r s e f o r a m e n a n t e r i o r l y . T h e f ai lu re o f t h e b o n e e l e m e n t s t o fuse t o f o r m th e c o m p l e t e b o n e is t h o u g h t t o be d u e t o th e n o r m a l c a r t i l a g e m o d e l no t be in g laid d o w n o r i g in a ll y in th e m e s o ­ d e r m a l m a s s o r t h a t a n a r e a o f c a r t i l a g e d e g e n e r a t e s bef ore oss ifi ca tio n c o u l d o c c u r . Fig. 6. D r a w i n g fr o m spec imen o f a b s en ce o f a n t e r i o r a r c h o f atl as . L u m b o - s a c r a l A b n o r m a l i ti e s W i t h t h e n o r m a l s t r a i n i m p o s e d o n t h is a r e a in w e i g h t ­ b e a r i n g in t h e e r e c t p o s i t i o n , a n y a b n o r m a l i t y w h i c h m a y f u r t h e r w e a k e n t h e a r e a is likely to c a u s e s t r a i n o n li g a m e n t s a n d sof t tissues a n d t o c a u s e r eac ti ve b o n y o u t g r o w t h s all o f w h i c h c o u l d c o n t r i b u t e t o s y m p t o m s o f b a c k a c h e . Level o f th e F u l c r a l V e r t e b r a an d As sim il at io n o f t he last P r e - s a c r a l V e r t e b r a T h e n o r m a l n u m b e r i n g o f v e r t e b r a e m a k e s T1 t h e 8th V e r t e b r a , LI t h e 2 0t h a n d S I t h e 25 th . T h e r e a r e t h u s t w e n t y - f o u r p r e - s a c r a l v e r t e b r a e w i t h th e 2 5t h b e i n g th e m o s t c r a n i a l a r t i c u l a t i n g w i t h the ili um a n d k n o w n as th e fu lcral v e r t e b r a . T h i s t e r m is n o t t o be c o n f u s e d w it h S2 w h e n r e f e rr i n g t o t h e a xi s o f t h e sa c ro - i l i a c j o i n t . H o w e v e r this p a t t e r n is n o t a l w a y s a d h e r e d to in d e v e l o p m e n t . W i t h the d e s c e n t o f t h e ili um a n d s u b s e q u e n t s e g m e n t a t i o n o f the m e s e n c h y m a l c o n d e n s a t i o n f o r m i n g t h e v e r t e b r a l c o l u m n t he fu lcr al v e r t e b r a m a y be th e 24 th o r 26 th , t h e ili um in thes e c as es h a v i n g m o v e d d o w n a f u r t h e r s e g m e n t o r n o t d e s c e n d e d f a r e n o u g h a s t h e ca s e m a y be. I f t h e 2 4t h v e r t e b r a is th e f u lc ra l v e r t e b r a t h e r e will o n l y be f o u r l u m b a r v e r t e b r a a n d t h e s a c r a l will h a v e six se g m e n t s , th is u p p e r se g m e n t m a y be c o m p l e t e l y fu sed t o t h e s a c r u m o r it m a y be p a r t l y fu sed by t h e l at er al m a s s e s w i t h th e n e u r a l a r c h still s e p a r a t e . It m a y p a r t i c i p a t e in t h e sa c ro - i l i a c j o i n t o r t he a u r i c u l a r s u r f a c e m a y still e x t e n d o n l y as f ar a s th e 2 5 th v e r t e b r a . I f i n c o m p l e t e l y i n c o r p o r a t e d in t h e sa cr o -i li ac j o i n t t h e r e is a t e n d e n c y f o r t h e la t e r a l m a s s t o b e c o m e s e c o n d a r i l y m o b i l i s e d . W h e r e th e f ul cr al v e r t e b r a is the 26t h t he first c o c c y g e a l s e g m e n t is of t e n fu sed t o t h e s a c r u m at t h e bas e g iv i n g a five piece s a c r u m r a t h e r t h a n a f o u r piece w h i c h is r a re ly se en. S o m e t i m e s a t r a n s i t i o n a l v e r t e b r a is seen wi th t h e last p r e s a c r a l v e r t e b r a c o m p l e t e l y fu sed o n o n e side t o th e s a c r u m a n d e x h i b i t i n g c o m p l e t e l y n o r m a l l u m b a r 5 o n th e o t h e r side. In d e v e l o p m e n t , l ack o f s e g m e n t a t i o n o f L5 f r o m SI lat er al m a s s in th e p r i m i t i v e m e s e n c h y m e m a y resu lt in a s i m i l a r a b n o r m a l i t y t o s o m e o f t h e a b o v e . T h e c a r t i l a g e laid d o w n f o llo w s t h e m e s e n c h y m a l p a t t e r n w it h L5 h a v i n g u n u s u a l l y l ar ge d o w n w a r d l a t e r a l pr oc es s es c o n t i n u o u s w i t h t h e co s t al e l e m e n t s f o r m i n g th e l at er al m a s s o f t he s a c r u m . Since os s ifi c at io n p r o c e e d s m o r e slo wl y a n d t h e a r e a is a l r e a d y u n d e r s t r a i n f r o m p o s t - n a t a l use, t h e c a r t i l a g e a t thi s p o i n t o f j u n c t i o n b r e a k s d o w n b e f o r e b e c o m i n g ossified a n d an a r t i c u l a t i o n is f o r m e d b e t w e e n t he l at er al p r o c e ss e s o f L5 a n d t h a t o f S I . W i t h c o n t i n u e d use th e s t r a i n o n this a r t i c u l a t i o n m a y c a u s e r eac ti ve b o n y p r o l i f e r a t i o n a n d in th e s p e c i m e n i l l u s t r a t e d on th e ri gh t e n c r o a c h m e n t o f th e a n t e r i o r • r- P l a t e 1. S p e c i m e n o f 4- piece s a c r u m with spi na bifida and l a s t p r e s a c r a l v er te br a l show ing en l ar g ed la t e r a l p ro ces se s with s e c o n d a r y joint f o r m a t i o n with l a t e r a l m a s s o f s a c r u m on th e left. i n t e r v e r t e b r a l f o r a m e n is likely t o h a v e c a u s e d p r e s s u r e o n L5 n er v e r o o t . T h e s p e c i m e n o n t h e left i ll u st r at es c o m p l e t e s p i n a bifida in th e s a c r u m as well. S ev er al o t h e r f a c t o r s m a y p r e d i s p o s e t o th i s a r t i c u l a t i o n o f L5 o n SI lat er al mas s. V a r i a t i o n s in th e L5 l at er al p r o ­ cesses c a n be seen f r o m t h e d i a g r a m w i t h t h e l o w er m o r e a n t e r i o r c o s t a l e l e m e n t b e c o m i n g la r g e r a n d p r o j e c t i n g m o r e in f er io r ly t h u s i n c r e a si n g th e l i k e l i h o o d o f it m e e t i n g the sa c r a l l a t e r a l m as s. A d d e d t o thi s is a f a c t o r i n t r o d u c e d by t h e an g l e f o r m e d b e t w e e n t h e b o d y o f t he s a c r u m a n d its l ate ra l m as s. I f th e la te r al m a s s e s incli ne u p w a r d s in r e l a t i o n t o t h e b o d y — the s a c r u m is s a id t o be h y p e r b a s a l — t h e po ss ib il ity o f a n a r t i c u l a ­ ti o n w i t h L5 in cr ea se s. I f th e m a s s e s a r e h o r i z o n t a l — h o m o - Fig. 7. D r a w i n g s fr o m sp ec im en s o f l u m b a r 5 v er te br a e sh owing differences in l a t e r a l proce ss es. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) JUNE, 1972 P H Y S I O T H E R A P Y Page 13 i P l at e 2. S p e c i m e n o f 5- piece s a c r u m , s e c o n d a r y mobi li sat io n o f lat er al m a s s with last p r e s a c r a l ve r t e b ra an d bony p ro l if er a­ tion en cr o ac h i n g on a n t e r i o r in t e r v e rt e b r a l f o r a m e n on left. o Fig. 8. D i a g r a m showing h y p e r b a sa l, h o m o b a s a l and hyp o b as al s a c ra . less. T h i s di f fe r en t s l o p e is t h o u g h t to be p a r t l y a s s o c i a t e d with the ilium a n d t h e final p o s i t i o n it a d o p t s in its de sc en t. Still a f u r t h e r f a c t o r in t h e f o r m a t i o n o f thi s a b n o r m a l i t y is f u n c t i o n a l w h e r e a sc o lio s is w i t h i n c r e a se d w ei g h t a n d a p p r o x i m a t i o n o n o n e sid e m a y u l t i m a t e l y c a u s e a s e c o n d a r y ar ti c u l a t i o n . S i m i la rl y d e g e n e r a t i o n o f t he L5 i n t e r v e r t e b r a l disc m a y c a u s e t h is v e r t e b r a t o set tle o n th e l at er al m a s s o f the s a c r u m i f its o w n l a t e r a l m a s s e s a r e a l r e a d y large a n d d o w n w a r d p r o j e c t i n g . Spondylolysis a n d S po nd yl ol ist hes is M u c h c o n f u s i o n a l w a y s se em s t o exis t in s t u d e n t s ’ m i n d s ov er t he se t w o c o n d i t i o n s . T h e f o r m e r re fe rs t o a def ect in th e l a m i n a o f t h e n e u r a l a r c h b e t w e e n t h e a r t i c u l a r pr oce ss es. T h e l at t er refers t o t h e s l i p p i n g f o r w a r d o f a v e r t e b r a o n th e o n e b el ow w i t h o r w i t h o u t a s p o n d y l o l y s i s b e i n g pr ese nt . T h e m e c h a n i c s o f t h e l u m b o s a c r a l j u n c t i o n w h e r e this c o n d i t i o n is m o s t c o m m o n , a r e well k n o w n t o th e p h y s i o ­ th e r a p i st . T h e t r a n s f e r e n c e o f th e w e i g h t o f t h e t r u n k b o r n e o n L5 t o t h e b a c k w a r d l y a n g l e d s a c r u m is a h a z a r d o u s p r o c e d u r e . T h e s p i n a l l i g a m e n t s p l a y t h e i r p a r t in sta bi li si ng the a r e a b u t r e q u i r e h e l p f r o m t he i l i o - l u m b a r l i g a m e n t P l a t e 3. S p ec i m en o f b i l a t e r a l spond ylo lys is o f la st p r e s a c r a l ve r t e b ra . h o l d i n g L5 later al p r o c e s s t o t h e iliac cr est . T h is li g a m e n t m a y be w e a k e n e d d u e t o a h y p o b a s a l s a c r u m l e n g t h e n i n g its c o u r s e o r a sm a ll p r o c e s s o n L5 a f f o r d i n g t o o little r o o m f o r a t t a c h m e n t f o r a l i g a m e n t o f a n y s t r e n g t h . C o n t i n u e d usa ge o f t h e a r e a ca u s e s f o r w a r d s t r a i n o f L5 o n SI un ti l a stress f r a c t u r e o c c u r s t h r o u g h the l a m i n a s e p a r a t i n g b o dy , pedicles a n d s u p e r i o r a r t i c u l a r pr o c e ss e s f r o m l a m i n a e , in f e r i o r a r t i c u l a r pr o ce ss es a n d s p i n o u s p r o ce ss . T h i s is sp o nd y l o l y s i s. T h e a n t e r i o r p o r t i o n is n o w free f r o m t h e l o c k i n g m e c h a n i s m o f th e i n f e r i o r p r o c e s s e s o v e r t he s u p e r i o r pr o c e ss e s o f the s a c r u m a n d c a n m o v e f o r w a r d c a r r y i n g th e rest o f t h e v e r t e b r a l c o l u m n w i t h it. T h i s is s p o n d y l o l i s t h e s i s . P r o b a b l y t h e m o s t c o m m o n c a u s e o f s p o n d y l o l i s t h e s i s w i t h o u t s p o n d y l o l y s i s is d e g e n e r a t i o n o f t h e a r t i c u l a r j o i n t s o f t h e v e r t e b r a l c o l u m n . If a d d e d to thi s th e p l a n e o f a r t i c u l a t i o n b e t w e e n L5 a n d SI is m o r e sa gi tt al t h a n f r o n t a l , t h e in f e r i o r pr o c e ss e s o f L5 slip t h r o u g h t he s u p e r i o r p r o ce ss es o f SI o n the m ed i al side a n d the w h o l e c o l u m n then m o v e s f o r w a r d o n t h e s a c r u m . T h e s p e c i m e n i l l u st r a t e d is a g o o d e x a m p l e o f this c o n d i t i o n , w i t h t h e l e n g t h e n e d a r t i c u ­ l a t i n g su r f a c e s o f t he i n f e ri o r a r t i c u l a r pr o c e ss e s well seen. P r o t e c t i v e b o n y o u t g r o w t h s o n t h e b o d y o f t h e s a c r u m a n d L5 t o try t o p r e v e n t th e f o r w a r d slide ar e a l s o e v id en t. O n e sp e c i m e n d e s c ri b e d in t h e l i t e r a tu r e s h o w e d s u c h gr o ss s l i p p i n g t h a t a b o n y ridg e h a d b e e n f o r m e d o n th e s a c r u m on w h i c h a t least o n e t h i rd o f th e b o d y o f L5 w a s re sting. In this i n s t a n c e it w a s t h o u g h t t o h a v e c a u s e d th e d e a t h o f a p a t i e n t by r u p t u r i n g t h e u t e r u s d u r i n g l a b o u r . L as t l y , if t h e pe d ic le o r l a m i n a e b e t w e e n th e a r t i c u l a r p r o c e s s e s is r a t h e r e l o n g a t e d a n d t h in , f o r w a r d s l i p p i n g is p o s s i b l e w i t h o u t a b r e a k in th e b o n e , t h o u g h this m a y o c c u r l at er w i t h i n c r e a se d s t r a i n . T h e d i se as e o s t e o g e n e s i s i m p e r ­ f ec ta in c h i l d r e n is o n e o f t h e c a u s e s o f t h e a b o v e . R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) Page 14 p h y s i o t h e r a p y JUNE, 1972 Plate 4. Specimen showing degenerative spondylolisthesis with bony proliferation on the bodies of L5 and SI. Fig. 9. Diagrams showing elongated pedicle and spondylolisthesis. Three instances o f spondylolisthesis in the cervical spine have been recorded, in conjunction with spina bifida. This raises the question whether there is a heriditary or congenital factor in the causation of spondylolysis. Heridi­ tary instances have been sited both in families and population groups and it is known to occur in conjunction with spina bifida. However it has not been seen in the new-born and has been recorded as having developed over a period o f years observing a spondylolisthesis first. It may be that the heriditary factor is due to the spina bifida and shallow articulating facets predisposing towards a weakness of ligamentous support of the area. With the strain of use, stress facture develops or L5 slips forward over the inadequate superior facets of SI. The theory that there are two ossi­ fication centres for the neural arch on either side and that spondylolysis is a failure of ossification of these two centres does not enjoy much support. However in the specimen illustrated the unilateral division of the laminae is not totally consistent with stress in the region which is more likely to cause a bilateral lesion. Furtherm ore the lamina on the interrupted side is very much thinner than on the uninterrupted side. It may be that some vascular deficiency was the cause of the faulty ossification here. Fig. 10. Drawing from specimen showing unilateral spondylolysis. Fig. 11. Drawing from specimen showing spurs in ligamentum flavum. Bony Spurs in the Ligamentum Flavum These bony spurs have been recorded by several authors and the illustration here is from a specimen in the University of Cape Town collection, which also shows1 absence of the spinous process. Bony outgrowths are seen on both the superior and inferior attachments of the ligamentum flavum. The most common site for these outgrowths is in the thoracic region where a dorsal curve already exists. As the function of this ligament is to check undue forward flexion it would seem that this is a reaction to strain in the area. Other anomalies which are seen tend to be at the transi­ tional levels o f vertebrae related to the characteristics of the articular processes. For example LI may exhibit the form of T12 articular processes. Increased or decreased mobility by one segment is not really remarkable. The deficiency in SI, superior articular facet has already been discussed in relation to spondylolisthesis. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) JUNE, 1972 P H Y S I O T H E R A P Y Page 15 SUMMARY The ossification of the vertebral column is briefly discussed with bony abnormalities following developmental phenomena being shown, such as spina bifida, cervical rib and various anomalies of the lumbo-sacral junction. Spondylolisthesis and spondylolysis is discussed with reference to causation from a stress fracture, degeneration of the joints of the vertebral arch and attenuated pedicles or pars inter-articularis. A note on the possibility of hereditary factors in this condition is added. Other minor anomalies such as transverse foramen deficiencies in the cervical spine, differences in the plane of articular facets and spurs in the ligamentum flavum are noted. One specimen of absence of the anterior arch of the’atlas is described. ACKNOWLEDGEMENTS I would like to express my most sincere thanks to Professor L. H. Wells for his help and patience in preparing this project and to Mr. D. J. Coetzee for his assistance with the specimens. I would also like to thank Miss Ann Levett from the University o f Cape Town Anatomy Department for her patience and co-operation in preparing the photographs. REFERENCES Bardeen, C. R. (1905). Development of Thoracic Vertebrae in Man. Am. J. Anat. Vol. 4; pp. 163; 265. Brannon, Col. Earl W. (1963). Cervical Rib Syndrome. J. Bone and Joint Surg. Vol. 45 A No. 5; pp. 977. Braus, H. (1921). Anatomie des Menschen, Bd 1. Breathnach, A. S. (1965). Frazer’s Anatomy o f the Human Skeleton. Dawley, Maj. J. (1971). Spondylolisthesis of the Cervical Spine. / . o f Neurosurgery. Vol. XXXIV No. 1; pp. 99. BACK EXERCISES IN PERSPECTIVE MRS. H. P. MAREE, B.Sc. Physiotherapy (Rand), Diploma in Phys. Ed. (National Teacher’s), Teacher’s Certificate in Physiotherapy, U.C.T. This article is not a learned discourse with references because this is a result of practical experience in several fields; among school children, Health Clinics (good and bad), gymnastic clubs, refresher courses for Physical Educa­ tion and Physiotherapy students and patients. The standard o f perfection of performance varies. It is obvious that the correct result, i.e. the result aimed at, depends upon accurate performance of the exercise and is not just a means of using up energy. The Olympic gymnast has this in common with the patient receiving exercise therapy. In general we are inclined to use our special techniques such as Proprioceptive Neuromuscular Facilitation, as accurately as our experience allows, but when we teach an active exercise we are less stringent in observing the rules of accurate performance. Whether the patient has previously been treated by mobilising techniques or manipulations, or has had exercises, the purpose of these treatments is lost if the patient himself cannot retain the correct alignment achieved during these treatments. It is well known that a mobile joint demonstrates aches and pains less frequently than a stiffer joint, but it is necessary to be able to adequately control the movements of such a joint. Back exercises are closely allied to abdominal and postural exercises, and must be considered in the same way as ‘Posture’ i.e. as static or dynamic. Starting positions are of utmost importance and should be as perfect as possible or the movement that follows will be of inferior quality and value. This is clearly demonstrated by the developmental sequence progressed from positions on the mat to standing and shows that purposive movement is superimposed upon a stable background. In no less a manner is this demonstrated by a Durbin, F. C. (1956). Spondylolisthesis of the Cervical Spine. J. B. and J. Surgery, Vol. 388. Fawcett, E. (1907). On the completion of ossification of the human sacrum. Anat. Anz. Band 30; pp. 414. Fraser, J. E. (1940). A Manual o f embryology. Hadley, Lee, A. The Spine. Hollinshead, W. H. (1969). Anatomy fo r Surgeons. Vol. 3. The Back and Limbs. Langman, J. (1969). Medical Embryology. Newman, P. H. (1963). The Etiology of Spondylolisthesis. J. B. and J. Surgery, Vol. 45B; pp. 39. Noback and Robertson. (1951). Sequences of appearance of ossification centres in the human skeleton during first 5 pre-natal months. Am. J. Anat. 89; p . 1. Perlman, R., Hawes, L. E. (1951). Cervical Spondylolisthesis. J. B. and J. Surgery, Vol. 33A, pp. 1012. Shore, L. R. (1931). Abnormalities of the Vertebral Column in a series o f skeletons o f bantu natives o f S.Africa. J. o f Anat., Vol. LXIV, Part II, pp. 206. (1931). A report on the nature of certain bony spurs arising from the dorsal arches of the thoracic vertebrae. J. o f Anat. Vol. LXV, Part III. (1929). A report on a specimen of spondylolisthesis found in the skeleton o f a bantu native of S.A. Br. J. o f Surg., Vol. XVI, No. 63. Steindler, A. (1955). Kinesiology. Trevor Jones, R. Personal communication. Trotter, M., and Petersen, R. (1966). Osteology, Section IV. Morris’ Human Anatomy. Editor, Anson-. Wells, L. H. (1963). Variation in the human vertebral column with particular reference to the lumbo-sacral junction. S.A.M .J., Vol. 37, pp. 60. (1963). Congenital deficiency of the vertebral pedicle. The Anat. Rec., Vol. 145, No. 2. gymnast, and to perfection in a gymnast of Olympic standard. An exactly correct starting position is necessary to the precision movement which follows. The extraordinary mobility of the gymnast’s joints is precisely controlled • throughout the movement by the strong and well-trained muscles of the trunk. There is no question o f which muscles are the most important in maintaining or performing the postures or movements. All the trunk muscles are of equal importance and co-operate with and support one another perfectly: the back muscles, the muscles of the posterior abdominal wall, and the abdominal corset, and the muscles of the hip joints and pectoral girdle. The area of the “ back” is both extensive and deep. “ Longtitudinally” it includes the area from the base of the skull to the insertion of the hip joint muscles into the femurs. The “ depth” is from ventral to dorsal surfaces. The controversy of back extension exercises as opposed to back flexion exercises is, in my opinion, merely a theoretical argument. The back muscles themselves are both deep and superficial, and the curve in the thoracic area is covered and controlled by groups of more superficial muscles in relation to the pectoral girdle. In the lumbar area one must consider the muscles of the abdominal corset, the hip flexors and the hamstrings in relation to the pelvic girdle. Although the ‘back’ may be divided into areas by the spinal curves, the function of the back must be considered as a whole, and hyperexten­ sion is undersirable because this is limited to the secondary curves, i.e. cervical and lumbar areas. The aim of “ back exercises” is to ensure the alignment of the back as a whole. This stabilising in the good postural position will ensure a more practical and harmonious balance through the back as a whole, and the correct balance of the pelvis over the lower limbs is thus ensured. Exercises done in isolated areas with the sole purpose of strengthening muscles, might well accentuate cervical or lumbar lordosis and malalignment of the bones and joints. Correct alignment of the trunk structure and the pectoral and pelvic girdles in relation to it. does not infer rigidity, but mobility of joints R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. )