Intervertebral Disc Calcification
`
`4. I . Introduction
`
`Although calcification of the nucleus pulposus is not a common pathological finding
`in intervertebral discs, it warrants discussion for a number of reasons.
`
`4.2. Complications
`
`the most
`First of all, it is one of the few causes of acute excruciating spinal pain,
`common being pathological fractures, acute inflammatory lesions, some tumours and
`the vascular catastrophe of dissecting aortic aneurysm.
`
`Secondly, paraplegia of sudden onset may complicate prolapse of calcified
`nuclear material into the thoracic spinal canal. This cause of paraplegia may go
`unrecognized if the calcified nuclear material is dispersed into the spinal canal where
`it may be difficult to see on plain X-rays. An erroneous diagnosis, such as acute
`ascending polyneuritis or vascular accident to the cord may then be made.
`
`is relatively
`it
`Thirdly, while Kohler and Zimmer (1968) have stated that
`common in adults, the belief is widespread that it is of little clinical significance.
`Indeed, Nachemson (1976) included intervertebral disc calcification in a list of
`radiological findings in the lumbar spine which, in his view, have no significance as
`causes of low back pain.
`
`Surgeons in consultant practice should beware of generalizations about disease
`processes which may lead them to think that certain pathological changes cannot be
`related to a patient’s symptoms.
`
`is clear that nucleus pulposus calcification may be associated with
`While it
`localized spinal pain of moderate severity and that the pain usually responds to
`simple conservative methods of treatment, it is equally clear that this disc disorder
`may have serious consequences for individual patients and that surgical operations
`
`
`145
`
`

`
`124 Intervertebral Disc Calcification
`
`4.3. Patterns in Children
`
`Clinical syndromes associated with nucleus pulposus calcification in children are well
`recognized, though rare. Bouts of acute painful wry neck or severe spinal pain of
`sudden onset, with fever, moderate elevation of the erythrocyte sedimentation rate
`and occasional increase in white cell counts, subside rapidly with rest. Typically,
`widespread calcification of variable density outlines the area of one or more of the
`
`Figure 4.1. A lateral X-ray of the thoraco—lumbar spine in a child aged 11, showing nucleus
`pulposus calcification at multiple levels. Note the straight lumbar spine due to muscle spasm
`
`Table 4.1
`
`
`
`Site
`
`Sex
`
`F
`M
`F
`F
`F
`
`L3/4
`T10/11
`T11/12
`L3/4
`L5/S1
`
`T9/10, T10/11
`F
`T12/Ll
`F
`L1/2
`F
`L4/5, L5/S1
`F
`Ll/2
`F
`L1/2
`M
`
`F T8/9
`
`
`146
`
`

`
`Patterns in Children
`
`125
`
`Figures 4.2. Antero—posterior (a) and lateral views (b) of the sacrum in a female aged 36,
`showing nucleus pulposus calcification in a rudimentary sacral intervertebral disc
`
`
`147
`
`

`
`lntervertebral Disc Calcification
`
`nuclei pulposi. This calcification usually disappears within a few weeks of its first
`recognition on the X-ray examination of the spine (Fig. 4.1).
`The natural history of symptomatic paediatric intervertebral disc calcification has
`been defined recently by Sonnabend et al. (1982), following a review of 35 papers on
`the subject. Most of these cases occur in the cervical discs. Trauma seems to play a
`part, at
`least as a precipitating factor.
`In children,
`the disorder
`is usually
`asymptomatic in the thoracic spine.
`In this review of 89 children with symptoms attributed to the lesion, the sex ratio
`boyszgirls was 1.5:1, but in 19 children who were asymptomatic, it was 0.5: 1.
`Crock (1982) reported twelve cases of intervertebral disc calcification in adults,
`ten of whom required surgical treatment for the relief of severe intractable pain, not
`responsive to conservative measures of treatment. Only two of these patients were
`males.
`
`The sites of disc calcification also differed markedly from that seen in children
`(Table 4.1).
`In dogs with disc calcification, involvement of the sacral intervertebral discs
`occurs in about 4 or 5%. Apparently not previously reported in man, I have observed
`a female patient with the condition in the first sacral intervertebral disc, where it has
`caused troublesome sacral pain for a number of years (Figs. 4.2a, b).
`
`4.4. Patterns in Adults
`
`The radiological appearances of calcific deposits in this series of twelve cases were
`classified into four groups.
`1. Small discrete irregularly opaque shadows within the nucleus pulposus lying
`nearer the posterior than the anterior boundary (Figs. 4.3 a, b, 4.4).
`2. Widespread calcification of variable density giving the nucleus pulposus a
`fluffy outline (Figs. 4.5, 4.6).
`3. Small discretely outlined zones of calcification lying adjacent to one vertebral
`end-plate but peripherally located in the nucleus pulposus (Figs. 4.7a, b).
`4. Discrete aggregates of densely calcified material confined to the area of the
`nucleus pulposus (Figs. 4.8a, b, 4.9, 4.10).
`Computerised tomography may provide valuable information on the spatial
`distribution of calcified disc tissue with particular reference to its relation to the
`spinal canal and its neural contents (Fig. 4.11).
`
`a) Clinical Features
`
`Examples of type 1 nucleus pulposus calcification are illustrated in Figs. 4.3a, b, 4.4.
`These patients, one female (Figs. 4.3 a, b) and the other male (Fig. 4.4), presented
`
`Figures 4.3a and b. Antero-posterior and lateral X-rays of the mid-dorsal spine in a female
`patient aged 60 showing type I nucleus pulposus calcification
`
`Figure 4.4. Lateral X-ray of the thoraco-lumbar junction in a male aged 56 years showing
`type I nucleus pulposus calcification. This X-ray appearance remained unchanged in eight
`
`
`148
`
`

`
`Patterns in Adults
`
`127
`
`
`149
`
`

`
`128 Intervertebral Disc Calcification
`
`
`150
`
`

`
`Patterns in Adults 129
`
`
`
`Figures 4.8 a and b. Lateral and antero-posterior radiographs of the thoracic spine in a
`female patient aged 47 years showing type 4 nucleus pulposus calcification at the T8/9 inter-
`vertebral disc level. The middle lobe of the right lung was adherent to this disc in the
`paravertebral gutter, the remainder of the pleural cavity being free of adhesions
`
`
`
`Figure 4.10
`
`Figure 4.9. A lateral radiograph of the thoracic spine showing type4 nucleus pulposus
`calcification at the T10/11 intervertebral disc space in a male patient aged 46
`
`Figure 4.10. A photograph of the calcium calculi removed at operation from the disc shown
`
`Figure 4.6. Lateral tomogram of the L4/5 and L5/S1 area of the spine in a female patient
`aged 45 years showing type2 nucleus pulposus calcification at L5/S1
`
`Figures 4.7. a Antero-posterior view of the lumbar spine in a female patient aged 54 years
`showing type3 nucleus pulposus calcification at the L3/4 level on the right side of the
`
`
`151
`
`

`
`130 Intervertebral Disc Calcification
`
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`Patterns in Adults
`
`131
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`

`
`132 Intel-vertebral Disc Calcification
`
`Figure 4.11. A computerised tomograph showing the pattern of calcification of disc tissues at
`the disc between the vertebrae T11/ 12, in a female, aged 49 years. The calcification (type 2)
`is shown extending postero—laterally into the spinal canal where it
`is
`related to the
`antero—lateral aspect of the spinal cord on the left side
`
`with spinal pain of sudden onset, localized respectively" to the mid-thoracic spine and
`to the upper lumbar zone. In both, symptoms were controlled promptly with simple
`measures including the use of spinal supports for some months. The radiological
`appearance of the calcification shown in Fig. 4.4 remained unchanged in X-rays
`taken at follow-up eight years later. There were no outstanding clinical features
`characterizing these cases.
`By contrast, more serious problems were seen in the ten patients whose details
`are shown in Table 4.2. Eventually all were treated surgically.
`In four of the patients in the surgical group, nucleus pulposus calcification was
`found in the mid— and ‘low lumbar discs. These patients presented with severe low
`back pain and paraspinal muscle spasm. One had a unilateral psoas muscle spasm
`preventing hip extension. The severity of the pain was such that family members
`complained bitterly that conservative treatment was ineffective, and they insisted that
`
`
`154
`
`

`
`Table 4.3. Patterns of nucleus pulposus calcification
`
`Patterns in Adults 133
`
`Female
`
`Male
`
`1
`3
`5
`1
`
`1
`—
`—
`1
`
`In the other six patients in the surgical group, nucleus pulposus calcifications
`were localized in the upper lumbar and lower thoracic discs. Again, the pain of which
`they complained was intense in character,
`localized in the upper lumbar and upper
`abdominal regions, and in the thoracic spine and radiating to one or both sides of the
`thoracic cage. Deep breathing, coughing and sneezing aggravated the pain.
`Paraspinal muscle spasm was also marked. One patient, the only male in the series,
`presented with low thoracic pain and weakness of his legs. There were no specific
`abnormal neurological findings in any of these patients.
`
`b) Pathological Findings
`
`There were two striking observations made at operation. One concerned the local
`inflammatory response apparently induced by the nucleus pulposus calcification in
`the region of affected discs. The other related to the appearance and texture of the
`calcified material removed.
`
`Within the spinal canal, in the retro-peritoneal space and between the parietal
`and visceral pleura, adhesions were found related to the affected discs. The most
`remarkable evidence of this pathology was seen in the right hemi-thorax (case 10)
`where well-formed filmy adhesions had to be divided between the visceral pleura of
`the middle lobe of the lung in the paravertebral gutter and the antero-lateral surface
`of the disc between T8 and T9,
`immediately adjacent to the nucleus pulposus
`calcification (Figs. 4.8a, b) on the right side of the disc space.
`The calcified material removed from the intervertebral discs at operation was
`either white in appearance, with the consistency of soft paste, or in the shape of
`irregular calculi, slightly yellowish in colour.
`Histological examination was carried out on tissue removed in five cases. In each
`case degenerative fibro-cartilage was found associated with calcification. Chemical
`analysis confirmed the presence of calcium in the tissues. No abnormal cartilaginous
`proliferation was found in any case, nor was there any evidence of specific
`inflammation.
`
`c) Surgical Treatment
`
`The types of operation carried out in the ten patients reported by Crock (1982), are
`set out in Table 4.2.
`
`
`155
`
`

`
`134 Intervertebral Disc Calcification
`
`made in this series of ten patients who underwent surgical operations for this
`problem.
`Nine out of ten of the patients were female and in eight out of the ten there was
`some history of trauma.
`Six of the patients had had some form of spinal surgery performed prior to the
`onset of their nucleus pulposus calcification.
`While the pathological changes induced within the disc itself include some
`features of non—specific inflammation, it is interesting to note the capacity of this
`lesion to induce non-specific inflammatory changes at the surface of an affected disc.
`Observations of retro-peritoneal fibrosis, perineural fibrosis in the spinal canal
`and localized pleural reactions have been reported in this series.
`The pain in certain cases of nucleus pulposus calcification is acute in onset,
`intense in character and frequently unrelieved by conservative measures.
`In
`particular, intra-disc injections of hydrocortisone appear to be ineffective, whereas in
`cases of acute supraspinatus tendonitis they often relieve patients of pain.
`Analysis of the findings in the ten patients presented in this chapter suggests that
`acute nucleus pulposus calcification deserves more serious consideration in clinical
`practice than is normally accorded to it.
`
`
`156
`
`

`
`Spondylolisthesis
`
`5.1. Planning of Treatment
`
`Spondylolisthesis is a condition in which one vertebral body slips forward on the one
`below it. Associated with the forward displacement of the vertebral body there is
`either a laminal defect or degenerative arthritis of the inferior laminal facet joints.
`The most common type of spondylolisthesis requiring surgical treatment is that
`seen with pseudarthroses in the lamina, so-called spondylolytic spondylolisthesis.
`Pseudarthroses occur in the pars interarticularis on each side. These take the form of
`asymmetrical false joints with false capsules and synovial linings in which osseous
`loose bodies may be found.
`In degenerative spondylolisthesis the slip of the vertebral body is associated with
`degenerative arthritis of the inferior facet joints of the lamina; this condition is seen
`most commonly in women after the menopause.
`Spondylolisthesis usually occurs at one level in the lumbar region, though rarely
`two or more adjacent levels may be involved (Fig. 5.1). Spondylolisthesis is one of
`the academic subjects that has appealed to orthopaedic surgeons for many years. It
`has been classified in various ways, five clinical groups being widely recognized:
`congenital, isthmic, degenerative, traumatic, and pathological.
`In this chapter, conservative treatment will not be discussed, beyond pointing
`out that many patients with this condition who present for the first
`time with
`symptoms will respond to a variety of conservative measures.
`Likewise, the academic aspects of this subject will not be dealt with in depth.
`Readers may refer to the published work of Newman, Wiltse, McNab, and Louis,
`listed in the short bibliography which is found at the end of this book.
`
`a) History
`
`Patients may develop a wide range of symptoms and signs, including: back pain,
`referred leg pain, a combination of back and leg pain, or in severe cases, evidence of
`
`
`157
`
`

`
`
`
`Spondylolisthesis
`
`
`
`__.__._.______....___........._..__.__..._.__:__.....__.._..._?.....__._._.ul
`
`Figure 5.1. A lateral radiograph of the lumbar spine of a woman aged 45 years showing
`spondylolytic spondylolisthesis, Grade 1, at L5/S1 with a normal intervertebral disc, and
`Grade 2 at L4/5 with disc resorption at that level. This patient only required conservative
`treatment for low back pain
`
`outlet may become obstructed during labour, rendering Caesarean section essential
`(Fig. 5.2).
`In practice, no single operation will necessarily produce a cure in patients with
`spondylolisthesis. Hence it
`is necessary to make a careful analysis of each case,
`attempting to introduce some rationale to the planning of treatment.
`In assessing individual patients with a View to selecting a particular type of
`operation for use in treatment, one must first
`take account of the outstanding
`features in the clinical history. Careful analysis of individual symptom patterns may
`indicate, for example,
`that decompression of the spinal canal alone may be the
`operation of choice. This will be the case where the patient’s dominant symptoms are
`bilateral buttock and leg pain.
`Where the symptom pattern combines the complaints of back and leg pain, then
`
`
`158
`
`

`
`
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`159
`
`

`
`
`
`Spondylolisthesis
`
`b) Physical Parameters
`
`Having considered the history, four physical parameters should be analyzed in each
`case before the definitive decision can be taken on the type of surgical procedure
`required.
`
`i) Role of Laminal Pseudarthroses in Symptom Production
`
`The first of these is the role of the laminal pseudarthroses in symptom production.
`The structure of the pseudarthroses varies considerably. Defects in the pars inter-
`
`Figures 5.3. a A lateral radiograph of the lower lumbar spine showing a spondylolytic defect
`in the lamina of L5. b Normal discograms at L3/4, L4/5 and L5/S1 in this case
`
`Figures 5.4. a A drawing to illustrate a spondylolytic defect in the lower of two laminae
`which are viewed obliquely. b An oblique radiograph of the lower lumbar spine showing a
`normal lamina with the pars interarticularis outlined in the middle of the photograph and the
`spondylolytic defect involving the lowest lamina shown on the film. Loose bodies in the
`pseudarthrosis are clearly visible
`
`Figures 5.5a—d. Photographs of loose laminae (“rattlers”) removed at operations from
`patients with spondylolytic spondylolisthesis. The specimens have been photographed from
`above except for b, which is a lateral photograph. In a, note the complex nature of the
`pseudarthroses with the loose body on the right side of the photograph. In b, the large
`pseudarthrosis is visible in profile and the inferior facet of the lamina is visible on the bottom
`
`
`160
`
`

`
`
`161
`
`

`
`140 Spondylolisthesis
`
`articularis are usually bilateral, though rarely symmetrical. They are often associated
`with bulky false joints from which recognizable synovial tissue may be extracted and
`in which a number of loose bodies may be found. These pseudarthroses are
`immediate posterior relations of the emerging nerve roots at
`the intervertebral
`foramina on both sides. Their obtrusions into the intervertebral foramina and nerve
`root canals may be the sole cause of referred leg pain in patients with spondylolytic
`spondylolisthesis, or in rare cases of spondylolysis (Figs. 5.3 a, b). In the usual case
`with bilateral laminal defects, the spinous process, lamina and the inferior articular
`processes remain as a single unit which is loose in the vertebral column. When the
`spinous process is grasped with an instrument during operation, this whole unit can
`be moved freely. It has been described as the “rattler”. Removal of the “rattler” is
`said to relieve nerve root pressure. However, if only the “rattler” is removed, the
`proximal portions of the pseudarthroses which remain attached to the pars inter-
`articularis on each side, leading up to the superior articular facets, remain in the
`spine. The related nerve roots cannot be seen throughout their courses unless these
`proximal segments of the pseudarthroses are also removed, thereby completing the
`nerve root decompressions. Simple removal of the “rattler”,
`therefore,
`is always
`inadequate (Figs. 5.4a, b, 5.5 a—d, 5.6).
`
`
`
`Figure 5.6. 1 and 2 show the relationship of the laminal pseudarthroses to the spinal nerves.
`The soft tissues such as ligamentum flavum, false capsule and synovium are not depicted. 3
`and 4 show the nerve root relations after removal of the “rattler” of spondylolysis, and the
`correct method of decompression (4) of the root canal and intervertebral foramen on the left
`side of the drawing
`
`ii) State of Discs Adjacent to Slip
`
`The second parameter to be considered concerns the state of discs adjacent to the
`vertebral slip, both above and below it. Discography may be an essential special
`investigation where the symptom pattern is characterized by a mixture of back and
`leg pain. For example, in the case of spondylolisthesis at L4/5, if the discograms at
`
`
`162
`
`

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`Spondylolisthesis
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`Figures 5.8. a A lateral radiograph of the lumbar spine of a man aged 45, showing Grade 2
`spondylolisthesis at L5/S1, with discograms at L2/3, L3/4 and L4/5. Post-traumatic disc
`disruptions are shown at each level, causing severe back pain. The patient had fallen from a
`height of 25 feet (8 metres). b A lateral tomogram of the same patient’s spine taken 9 months
`after an extensive multi-level posterior spinal fusion, which was planned after the discography
`shown in Fig. 5.8a
`
`disruptive disc lesions demonstrated by discography above the level of the spondylo-
`listhesis may help in planning the extent of a spinal fusion procedure (Figs. 5.8 a, b).
`Finally, in assessing the state of the discs in cases of spondylolisthesis where
`unilateral sciatica is a problem, lumbar myelography. is essential
`to exclude the
`diagnosis of disc prolapse, either at the level of the vertebral slip, or at some adjacent
`disc space.
`
`iii) Shape of Spinal Canal
`
`The third parameter to be considered is the shape of the spinal canal. When a patient
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`164
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`Planning of Treatment 143
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`Figures 5.9a and b. Antero-posterior and lateral radiographs of the lower lumbar spine in a
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`165
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`Spondylolisthesis
`
`myelography is essential if the symptoms include referred leg pain (Figs. 5.9a, b). In
`such cases, associated spinal canal stenosis may be found. Spinal fusion alone may
`then be contraindicated, concomitant decompression of the spinal canal being
`necessary.
`
`iv) Degree of Vertebral Slip
`
`The fourth parameter for consideration is the degree of vertebral slip. Increase in the
`degree of slip usually occurs gradually over a number of years, often in association
`with progressive narrowing of the related intervertebral disc (Figs. 5.10 a, b). In the
`
`Figures 5.10:: and b. Lateral radiographs of the lumbar spine in an adult showing in (a)
`spondylolytic spondylolisthesis Grade 1 at L5/S1 with a normal intervertebral disc. The same
`spine five years later (b) showing disc resorption and increase in slip to Grade 2
`
`presence of grade one or grade two spondylolisthesis, anterior interbody fusion may
`be satisfactory. However, this method should be reserved for thin patients who have
`had neither previous abdominal
`surgery, nor antecedent history of venous
`thrombosis. For cases with higher grades of slip, in which spinal fusion is being
`considered, standard methods of posterior fusion or inter—transverse-alar fusion may
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`146 Spondylolisthesis
`
`method calls for special training and even then its success rests on the surgeon having
`above-average skill.
`In recent years, attempts have been made to reduce higher grades of slip, either
`by manipulation under anaesthesia or by the use of femoral traction. Once reduced,
`anterior interbody fusion may be used, supplemented by one of a variety of devices
`now available for fixation, such as the plate and screws designed by Professor Louis
`of Marseilles, France. These manoeuvres are mentioned for the sake of completing
`the record of surgical measures in current use. If they are to be used at all, then the
`considerable attendant risk of these heroic efiorts must be thoroughly appreciated, with
`particular reference to cauda equina injuries.
`By contrast Bohlman and Cook (1982) have reported success by combining
`spinal canal decompression and in-situ posterior interbody fusion, using fibular grafts
`in two cases of spondyloptosis.
`In children, symptomatic spondylolisthesis may require surgical treatment and
`this should be undertaken early if there is any fear of increase in the degree of
`vertebral slip. Bilateral inter-transverse-alar fusion is usually effective.
`The operation for the removal of the “rattler” and decompression of the nerve
`root canals recommended by Gill and White (1965) can be recommended for use in
`adults whose symptoms are predominantly those of referred leg pain, which is usually
`bilateral. Following the Gill and White operation, some increase in vertebral slip may
`occur in a few patients. However, if back pain persists as a major problem, then
`spinal fusion may be required. The choice of method, be it inter-transverse-alar or
`anterior interbody fusion, will depend on the particular skills and preferences of the
`surgeon, bearing in mind that either method applied to this particular problem
`requires special training.
`While theoretically it may be desirable to perform spinal fusion and spinal canal
`and foraminal decompression operations simultaneously, this is not always possible.
`Furthermore, if the cases have been selected for surgical procedures according to the
`recommendations set out above, the results are usually good and the combined
`operations are then unnecessary.
`There will be a few patients who may continue to complain of referred leg pain
`after successful spinal fusion and, conversely, a few who will complain of back pain
`after relief of their leg pain (following spinal canal and foraminal decompression).
`These patients will require relevant secondary operations (Figs. 5.11a—c).
`The choice of treatment in patients with symptomatic degenerative spondylo-
`listhesis follows the same general lines outlined above. However, in this condition,
`spinal fusion alone is usually the operation of choice.
`
`5.2. Technique of Postero-Lateral
`Inter- Transverse-Alar Spinal Fusion
`
`a) Indications
`
`This operation has virtually replaced the older methods of posterior spinal fusion
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`168
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`Technique of Postero-lateral Inter-Transverse-Alar Spinal Fusion 147
`
`When the transverse processes are sturdy this method of spinal fusion can be
`recommended for the treatment of:
`
`1. spondylolisthesis, especially in children;
`lumbar spondylosis causing back pain;
`3. failed anterior interbody fusions.
`
`b) Preliminary Preparation
`
`Blood loss is often considerable so that transfusion facilities with three or four litres
`of blood must be available.
`The patient’s spinal X-rays must be displayed in the operating room.
`
`c) Positioning
`
`Patients should be placed prone on a suitable frame to avoid compression of the
`abdominal cavity (see pp. 106-107).
`
`d) Incisions
`
`In children a long mid-line incision is recommended, extending from L2 to the lower
`
`the laterally placed, parallel vertical incisions advocated by Wiltse
`In adults,
`(1978) are recommended (Figs. 5.12a—c).
`
`
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`a,
`
`Figures 5.12a—c. Drawings to illustrate the mid-line skin incision and the laterally placed
`incisions in the lumbo-dorsal
`fascia for the paraspinal sacro-spinalis splitting approach
`recommended by Wiltse
`
`e) Exposure of the Graft Bed
`
`If the mid-line incision is used, the paraspinal muscles are separated as described on
`pp. 110-113. Their dissection is carried laterally beyond the facet joints until the
`posterior surfaces of the transverse processes and the alae of the sacrum on both
`sides can be palpated. The bulky paraspinal muscle mass is then retracted backwards
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`169
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`148 Spondylolisthesis
`
`Figure 5.13. A photograph of a transverse section of a mid-lumbar vertebra, with the
`paraspinal muscles intact. The specimen has been cleared by the Spalteholz technique. Note
`the arrangements of the paraspinal muscles posteriorly, with a plane of cleavage clearly visible
`between the muscle bundles related to the posterior aspects of the transverse processes at
`their junctions with the superior articular facets. This is the plane of cleavage recommended
`for use in inter-transverse-alar fusions by Dr. L. Wiltse of Long Beach, California
`
`considerable during this stage of the operation and it is often difficult to see the
`transverse processes of L5 in the depth of the wound unless the paraspinal muscles
`have been separated from as high as the lamina of L2.
`less
`Using the lateral paraspinal muscle splitting incision of Wiltse (1978),
`extensive longitudinal dissection of these muscles is required to gain good exposure
`of the bony structures to be “fused”. Modified Gelpi retractors inserted between the
`separated muscle fibres aid in obtaining a clear view (Fig. 5.13).
`
`lumbar spine seen from behind to show the
`Figures 5.14. a A drawing of the lower
`intertransverse ligaments between L4, L5 and S1. On the right side note the preparation of
`the graft bed for an inter-transverse-alar fusion. The arrow indicates an upturned segment of
`bone cut from the ala of the sacrum and turned up towards the transverse process of L5. b A
`drawing to depict the preparation of the graft bed for an inter-transverse-alar fusion. Note the
`use of a curette to roughen the surface of the outer aspect of the superior facet of L5, leaving
`the capsule of the joint at
`that
`level. A chisel
`is shown turning up the flap of
`cortico-cancellous bone from the ala of the sacrum towards the transverse process of L5. c A
`photograph of a dissection of the lumbar spine viewed from the side, to show the siting of
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`170
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`171
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`Spondylolisthesis
`
`Preparation of the bed for the graft requires meticulous attention to detail. The
`intertransverse ligaments and muscles should be preserved. For fusions at L5/S1 level
`the capsules of the lumbo-sacral facet joints should be excised allowing access to the
`joint surfaces for excision of their articular cartilages and sub-chondral bone plates.
`The facet joint capsules between the superior facets of L5 and the inferior facets of
`L4 should be preserved intact. All remnants of soft tissues must be removed from the
`sacral alae, from the inferior facets of L5, from the lateral aspects of the partes
`interarticulares on both sides cephalad to the outer aspects of the superior facets of
`L5, from the outer aspects of the pedicles of L5 and the posterior surfaces of the
`transverse processes of L5.
`The exposed surfaces of the transverse processes of L5 should then be
`decorticated carefully, using a gouge and hammer or Leksell type rongeur. Then,
`with a stout curved curette the cortical bone on the outer sides of the L5 pedicles and
`superior facets of L5 should be broached to expose bleeding cancellous bone. The
`lateral aspect of the pars interarticularis of L5 lamina on both sides should also be
`roughened (Figs. 5.14a—c).
`Cortico-cancellous flaps cut from the postero—superior surface of the alae of the
`sacrum on both sides should be turned upwards to lie on the intertransverse
`ligaments, adjacent to the transverse processes of L5.
`
`f) Preparation of Graft Bone
`
`Autogenous grafts should be cut from the postero-lateral aspect of the iliac crest,
`access to this being obtained usually by undercutting the tissues between the
`lumbo-dorsal fascia and the iliac crest on one side.
`
`Thin strips of cortico—cancellous bone, with other slivers of cancellous bone can
`be obtained usually in sufficient bulk from one side of the pelvis.
`
`g) Placement of the Grafts
`
`Thin strips of cancellous graft should be packed into the facet joints of L5/S1—then
`other strips should be placed accurately along the length of the spine extending from
`the upper edges of the decorticated transverse processes, but below the level of the
`