Indications for Surgery
`
`233
`
`Figures 7.12a—c. a A lateral radiograph of the upper cervical spine in a woman aged 30 years,
`showing erosive changes in the region of the odontoid peg due to rheumatoid disease. b A ra-
`diograph of the same area of the spine in flexion, showing instability between C1 and C2 due to
`rheumatoid joint disease at that level. c A radiograph of the bones of the wrist and hand of the
`same patient showing the changes of juxta-articular osteoporosis in all the digital joints due to
`rheumatoid arthritis
`
`
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`234
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`Surgery of the Cervical Spine
`
`e) Infective Lesions
`
`Acute haematogenous osteomyelitis affecting the cervical spine may lead to acute or
`chronic compression of the spinal cord due to associated epidural abscess formation
`or to pathological subluxation of the vertebrae. Patients presenting with quadriple-
`gia need urgent investigation, appropriate surgical treatment being planned on the
`results of myelography or MRI. In the case illustrated in Chapter 8 (Figs. 8.4 a—c), it
`was on the basis of the myelographic findings that the decision was taken to perform
`a decompression laminectomy to drain the epidural abscess. Subsequently, the
`associated spinal deformity was treated conservatively, using skull
`traction in
`extension. Spontaneous interbody fusion followed, union occurring without signifi-
`cant residual spinal deformity.
`
`f) Tuberculous Infection
`
`This may cause gross deformity in the neck. Trans-oral fusion of C1/2 involving the
`facet joints on both sides of the odontoid may be required (Fig. 7.13).
`
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`

`Indications for Surgery
`
`235
`
`Figures 7.14 a, b. a A lateral radiograph of the cervical spine of a patient aged 40 years. Note the
`congenital fusions between the bodies of C5 and C6. Advanced degenerative changes have oc-
`curred at the disc between C6 and C7 with large osteophytes projecting posteriorly into the
`spinal canal. The disc between C4 and C5 appears normal in this view. b A lateral radiograph of
`the same spine in flexion showing instability at the C4/5 level
`
`
`Figure 7.13. A detailed view of the facet joint between C1 and C2 on the left side of the speci-
`men illustrated in Fig. 7.1. Note the relationships of the vertebral artery to this joint from which
`the bulk of the capsule has been excised. In the operation of trans-oral fusion of C1 and C2,
`grafts are inserted into this joint space after removal of the articular cartilage and sub—chondral
`bone plates. The lateral capsule of the joint should be carefully preserved to avoid damaging the
`vertebral artery on the lateral aspect of the joint
`
`
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`236
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`Surgery of the Cervical Spine
`
`More commonly, the disease affects lower cervical vertebrae where it is best
`treated by local debridement of carious tissue and anterior interbody fusion, see
`Chapter 8 (Figs. 8.12 a,b).
`
`g) C0ngem'talAbnormalities
`
`Congenital fusion of cervical vertebral bodies is relatively common. Severe degen-
`erative spondylosis is usually found in the adjacent vertebral segment below the
`fusion early in adult life. Occasionally vertebral instability will be found in the
`segment above or below the congenital fusion. Anterior cervical interbody fusions
`may be required for the treatment of either or both of these lesions (Figs. 7.14a,b).
`
`7.3. Cervical Discography
`
`The test is performed on the conscious patient with light sedation. The needles used
`for this investigation are smaller in calibre than those used in the lumbar spine
`(Fig. 7.15). They are usually inserted through the right side of the neck, anteriorly,
`by pushing the mid—1ine structures of the neck across to the left side with the
`
`1
`
`Figure 7.15. A photograph showing a gauge 25 “discogram needle” on the right of the picture
`with a gauge 22 “guide needle” alongside. On the left of the picture the stilettes are shown
`alongside their respective needles
`
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`Technique of Anterior Cervical Interbody Fusions
`
`237
`
`operator’s index finger. Control X-rays are taken in antero-posterior and lateral
`planes to ensure accurate placement of the tip of each “discogram needle” in the
`centre of the nuclear zones of the discs before dye is injected (see Chapter 2,
`pp. 66-69).
`'
`Spread of dye beyond the zone of the nucleus pulposus may occur into the
`unco-vertebral joint areas on both sides, while leakage backwards into the spinal
`canal (extra-thecal) may indicate a posterior disc disruption. Spread of dye results
`from incompetence of annular fibres and is not necessarily an indication of disc
`prolapse.
`The pain response provoked by injection of dye into the disc is not related to the
`volume injected or to the resultant increase in intra-discal pressure; rather, it is due
`to irritation, by the dye, of the sensitized pain fibres within the disrupted disc itself.
`Hence, the pattern of pain distribution is not strictly segmental and it does not follow
`the dermatomes in the upper limbs, as has been suggested by some writers. Use of
`cervical discography should be reserved for the investigation and demonstration of
`non-prolapsing disc disorders. By contrast, neither myelography nor C.T. scanning
`will help to identify the level of a disc with internal disruption. Those investigations
`find their proper application in the investigation of cases with disc pathology produc-
`ing space-occupying lesions in the vertebral canal.
`MRI, particularly with gadolinium enhancement, though useful, has not yet
`been found superior to discography in helping to confirm the diagnosis of post-
`traumatic internal disc disruption.
`
`7.4. Technique of Anterior Cervical Interbody
`Fusions
`
`a) Instruments
`
`Dowel cutting instruments permit these operations to be performed accurately at
`each attempt. Their use in most cases is preferred to the use of chisels or osteotomes
`for this reason and for the added safety afforded, during the operation, by the safety
`devices built into the design of Crock cutters. Photographs of essential instruments
`are found in Figs. 7.16—20 with descriptive legends outlining details of their assembly
`and use.
`
`b) Positioning
`
`Patients are placed supine on the operating table. A small wedge-shaped pillow
`should be placed under the shoulders, with a rolled towel supporting the hollow of
`the neck, the occiput resting in a rubber ring. The patient’s eyes should be protected
`and the anaesthetic tubes securely fixed to the patient’s forehead (Fig. 7.21).
`
`
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`
`Surgery of the Cervical Spine
`
`Figures 7.16 a, b
`
`
`252
`
`

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`Technique of Anterior Cervical Interbody Fusions
`
`239
`
`Figure 7.17
`
`Figure 7.18
`
`Figure 7.17. A photograph of two cervical retractors with smooth excavated ends designed to
`be held transversely across the anterior surfaces of the cervical intervertebral discs
`
`Figure 7.18. A photograph of the self-retaining retractor designed by Cloward for use in
`anterior cervical fusions
`
`
`
`Figures 7.16 a, b. a A photograph showing the Crock instruments used for dowel cutting in the
`operation of anterior cervical interbody fusion. On the right of the picture is a Hudson brace.
`Cutters of three sizes are shown. The starter centre pieces have been removed from each of
`these. On the right of the cutters is a pusher, which fits insidethe cutters and can be used to eject
`the starter centre pieces or graft bone. On the left of the cutters a pusher is shown with a tubular
`segment of metal measuring 12.5 mm in depth. When this “dummy” is slotted into the cutter it
`acts as a guard, preventing the cutter from penetrating deeper than 12.5 mm into the cervical
`vertebral bodies. Dummies are provided in three sizes, 10 mm, 12.5 mm and 15 mm, for use
`according to the vertebral dimensions in individual cases. On the left of the photograph, two
`tooled gouges are shown, which will fit into the cuts made into adjacent vertebral bodies. Their
`use is illustrated in Figs. 7.28 a—c. Note that the cutters have circular rings marking their outer
`surfaces, at intervals of 5 mm. Instruments manufactured exclusively by Thomson and Shelton
`Instrumentation Company, 6119 Danbury Lane, Dallas, TX 75214, U.S.A. b A photograph of
`guide sleeve with two prongs which penetrate the disc — allowing the cutter to be inserted
`without snagging surrounding soft tissues
`
`
`253
`
`

`

`240
`
`Surgery of the Cervical Spine
`
`
`
`Figure 7.19. A photograph showing fine, straight and forward-angled pituitary rongeurs suit-
`able for use during anterior cervical _interbody fusion operations, for removing remnants of
`vertebral end-plates and dis@ssu_e__fo_llowing curettage of the disc space
`
`
`
`Figure 7.20. A photograph of a Bayonet forceps with a fine tip, essential for use in cervical spine
`operations
`
`C) Incisions
`
`A right-sided hemi-collar incision can be used for approaches to any of the cervical
`discs, from that between C2 and C3 vertebrae to the lowest in the cervical spine. The
`use of longitudinal incisions may result in unsightly scars, though they may be
`necessary in special cases requiring multi-level spinal fusions.
`The platysma muscle is exposed by separating subcutaneous fat from its superfi-
`cial surface before the muscle is split in the line of its fibres. The encircling layer of
`deep cervical fascia is then incised along the anterior border of the sterno-mastoid
`muscle, allowing access to the space between the carotid sheath laterally and the
`rnid-line structures of the neck medially. Inserting the index finger into the space
`now created, the surgeon can palpate the front of the vertebral column. By moving
`the finger deliberately and carefully along the antero-lateral margin of the verte-
`brae, a plane of cleavage can usually be opened easily in the loose fascia between the
`carotid sheath and the mid-line structures of the neck over a distance sufficient to
`allow exposure of one, two or three of the cervical intervertebral discs.
`Most cervical fusions are performed at the levels of C4/S, C5/6 or C6/7. Having
`cleared the space as indicated, retractors may then be inserted, orientated trans-
`
`
`254
`
`

`

`Technique of Anterior Cervical Interbody Fusions
`
`241
`
`
`
`Figure 7.21. A photograph of a patient postured on the operating table for anterior cervical
`interbody fusion. Note the triangular-shaped pillow underneath the shoulders, the rolled towel
`(in black) under the neck, and the rubber ring on which the occiput rests. The endo—tracheal
`tube and the reinforced rubber airway adjacent to it are strapped to the patient’s face. Note the
`pad covering the eyes, to prevent pressure on the orbits during surgery. Assistants have been
`known to press on the eyes during the operation. Irreparable ocular damage has been reported
`from this cause. Note also the outline of the hemi-collar incision extending from the anterior
`border of the stemo—mastoid muscle to just behind the mid—line. Through this incision two or
`three cervical discs can be exposed. For exposure of the disc between C2 and C3 vertebral
`bodies, the incision needs to be placed in the sub-mandibular region, care being taken to avoid
`damaging the mandibular branch of the facial nerve. Note that both arms are by the patient’s
`side, to allow traction on the hands for lowering the shoulders while control X-rays are being
`taken during the operation
`
`versely and applied to the anterior aspect of one of the intervertebral discs. Up to
`this point the only major anatomical structures encountered will have been those
`already mentioned. Only occasionally will it be found necessary to ligate and divide
`an anterior cervical vein or some un-named venous tributary of the internal jugular
`vein. The superior thyroid vessels may be seen, but it is rarely necessary to ligate and
`divide them.
`
`The pre-vertebral fascia, that thin, filmy, opalescent membrane which sheaths
`the pre-vertebral muscles and the cervical column itself, is split longitudinally in the
`mid-line and the retractors re-positioned to give a clear view of the intervertebral
`discs and anterior aspects of the vertebral bodies. The medial edges of the right and
`left-sided longus colli muscles can be seen clearly and, using a fine bayonet forceps,
`the vessels related to the muscles at their attachments along the antero-lateral
`aspects of the vertebral bodies are coagulated with diathermy (Fig. 7.22). These
`muscular attachments are then separated from the vertebrae and discs, so that the
`cervical retractors may be replaced beneath their freed medial margins to expose the
`disc or discs to be removed. The risk of obstructing the carotid vessels during
`operation is thereby reduced, either with the use of the hand held retractors
`(Fig. 7.17) or with self retaining types (Fig. 7.18).
`
`
`255
`
`

`

`242
`
`Surgery of the Cervical Spine
`
`Figure 7.22. A photograph of a dissection of the anterior aspect of the cervical and upper
`thoracic spine of a female child aged 3 1/2 years, showing the origins and courses of arteries
`supplying the antero-lateral aspects of the vertebral bodies. The longus colli muscles have been
`removed from the left side of the specimen. The pre-vertebral fascia has also been removed but
`the anterior margin of the longus colli at its attachment to the antero-lateral aspects of the
`vertebral bodies on the right side is intact. Note the vertical chain of arterial anastomoses
`running along the margin of this muscular attachment, forming a parallel vascular channel with
`corresponding vessels on the left side of the vertebral column. (Dissected by Dr. H. Yoshizawa)
`[Reproduced from: Crock, H. V., Yoshizawa, H.: The Blood Supply of the Vertebral Column
`and Spinal Cord in Man. Wien—New York: Springer, 1977]
`
`
`256
`
`

`

`Technique of Anterior Cervical Interbody Fusions
`
`243
`
`d) The Thyroid Gland
`
`Before planning cervical discography and anterior cervical spine surgery in any
`patient, the surgeon should examine the patient’s thyroid gland. On three occasions
`in twenty-five years of practice, I have had patients in whom thyroidectomy has been
`required before satisfactory access to the anterior aspect of the cervical vertebral
`column was possible.
`
`e) Control X-Rays to Identify Individual Intervertebral Discs
`
`The use of a disposable needle with a Z bend in it, inserted into the disc, is recom-
`mended before lateral X-rays are taken. The needle serves the dual purpose of
`identifying the disc level and allowing the precise measurement of its antero-poste-
`rior width. (Fig. 7.23 a—c). Never remove the needle before the control X-ray has been
`exhibited in the operating room confirming the level of the disc to be removed.
`
`f) Preparation of the Dowel Cavity
`
`The relevant anatomy of the spine and the steps in this critical phase of the operation
`are illustrated in detail in Figs. 7.22-28. Once cutting instruments have been applied
`to the vertebral bodies the potential hazards of injuring the vertebral arteries or the
`neural structures in the spinal canal must be borne in mind (Figs. 7.1 a,b).
`Having made the preliminary cut across the disc space, the starter centre piece
`is removed from the cutter. The surgeon then selects the “safety dummy” of pre-
`determined size, by re-checking the antero-posterior measurements of the disc space
`and then personally assembles the cutter ready for use by inserting the “dummy”,
`which is held in place by the “pusher device”. Both the assistant surgeon and theatre
`sister should check the preparation of the cutter with the “dummy” and cross-check
`the disc space measurements before the surgeon re-inserts the cutter, after stage
`one, to commence the final preparation of the dowel cavity.
`Errors made at this stage could lead to catastrophic accidents during the opera-
`tion. The equipment illustrated in this chapter has been used by the author since
`1962 without any instance of spinal cord or cervical nerve root injury occurring up to
`the present time (1991).
`Having re-fitted the cutter into the preliminary circular slot cut during stage one
`(Fig. 7.25 a—c), it should be oscillated clockwise and counter-clockwise, avoiding any
`wobbling motion as the Hudson brace is being rotated. No force is to be exerted on
`the proximal end of the brace, other than that required to steady it with one hand,
`while the surgeon’s other hand holds the off-set control bar through which the
`oscillating motion is transmitted to the cutter.
`As the cutter advances slowly into the vertebral bodies and intervening disc
`tissue, the operator becomes aware of a grating sensation at its cutting end, from
`which an audible grating sound is emitted. The “dummy” inside the cutting cylinder
`will abut against the anterior surface of the disc and adjacent vertebral margins when
`the cutter has reached the depth that is determined by the length of the “dummy”
`(Fig. 7.26 a,b). Further penetration of the cutter into the vertebral bodies is thereby
`prevented. At this stage, the grating sensation ceases and the cutter spins smoothly
`
`
`257
`
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`

`244
`
`Surgery of the Cervical Spine
`
`Figures 7.23a—c. a A drawing to illustrate the use of a bent needle recommended by the author
`for use during control X-rays in the neck. A disposable 19 gauge needle is prepared by bending
`it in the jaws of an artery forceps. A right-angle bend is made near the tip and the measurement
`between the tip and the first right—angle bend taken. Usually 11.0—12.5 mm is satisfactory, de-
`pending on the size of the patient. b A drawing to depict the front of a cervical intervertebral
`disc with the needle in place for control X-ray during operation. c A drawing of the cervical
`spine shown from the side depicting the use of the bent needle for control X-ray. The right angle
`bend prevents penetration of the needle into the cervical canal, a potential risk if a straight
`needle is inserted. It has the added advantage of allowing precise measurement of the
`intervertebral disc space on the control X-ray
`
`4
`
`Figure 7.24. A drawing of a typical cervical vertebra
`
`with the ranges of measurements in millimetres of
`
`the transverse and antero-posterior diameters of the
`vertebral body and the antero-posterior diameter of
`the cervical canal
`
`
`258
`
`

`

`Technique of Anterior Cervical Interbody Fusions
`
`245
`
`Figures 7.25 a——c. a A drawing showing a starter centre piece at the top. Below it, the starter
`centre piece is shown in outline, assembled in the zero-size cutter. Note the circumferential
`markings on the cutter, each separated from the other by 5 mm. b A drawing of the cervical
`spine, viewed from the side, showing the cutter assembled on a Hudson brace with the starter
`centre piece in position and the pusher within the tube. The drawing depicts the method of
`commencing the preparation of a dowel cavity between the vertebrae of C5 and C6. c A
`drawing of the cervical spine viewed from in front, showing the outline of the cut in the mid—line
`between the vertebral bodies of C5 and C6, at the first stage of preparation of the dowel cavity
`
`
`259
`
`

`

`246
`
`Surgery of the Cervical Spine
`
`and silently. For added safety, while the cutter is being oscillated, the surgeon may
`check the measurement of its advancement by counting the rings on its outer
`mufiwe
`
`In the third stage of the preparation of the cervical dowel cavity a special tooled
`gouge is used to displace the fragments of vertebral bodies and intervertebral disc
`from the spine (Fig. 7.28 a). This has been manufactured specifically to fit accurately
`into the dowel cavity between the cut margins of the vertebral bodies, so that the
`central plug of disc attached to elliptical segments of the adjacent vertebrae can be
`levered out and removed. This instrument must be handled with caution, introduced
`without undue force as it is directed into the depth of the cut, so that it fits snugly
`into the vertebral body before a simple levering force is applied to snap off the
`ellipse of vertebral body, first on one side of the disc, then on the other. The gauge
`should not be rotated so that it lies transversely across the disc space. It will not then
`be effective in fracturing the ellipses of vertebral bone to which the disc is attached.
`It is designed specifically for use as described. It is usually possible to remove the plug
`of bone and intervening disc tissue in one piece.
`In cases of advanced spondylosis, where the opposing vertebral end—plates are
`sclerotic, being separated by thin unyielding remnants of disc tissue, it may be
`necessary to curette the remnants of the disc tissue from between the arcuate
`segments of vertebral bodies in order to create a gap in the intervertebral space into
`which these bony fragments can be displaced with the gouge. If the vertebral bone is
`extremely dense, one of the segments may need to be removed with a high speed
`drill, the other being removed then in the manner set out above.
`When the base of the dowel cavity has been exposed, brisk haemorrhage may
`occur from arteries and veins in the vertebral bodies. This is controlled easily by
`applying small quantities of bone wax to the cut surface of the vertebral bodies, only
`at the site of bleeding.
`
`
`
`Figures 7.26 a, b
`
`
`260
`
`

`

`Figure 7.27. A photograph of a dissection of the posterior aspect of the cervical and upper
`thoracic spine of a male aged 34 years. The posterior aspects of the vertebral bodies have been
`exposed and portions of the posterior longitudinal ligament have been removed from a number
`of vertebral bodies in the lower part of the specimen. In the upper part of the specimen on both
`sides, the origins of the anterior spinal canal branches of the vertebral arteries can be seen. In
`the neck, these vessels form the familiar arcuate arterial pattern on the anterior surface of the
`spinal canal which is found along its length. The vessels contribute to the intra-osseous arterial
`supply of the vertebral bodies, anastomosing with branches from the vascular chains demon-
`strated in Fig. 7.22 on the anterior aspect of the vertebral column. In the operation of anterior
`cervical interbody fusion the blood supply of the vertebral body remains largely intact, ensuring
`rapid vascularization of grafts
`
`
`
`Figures 7.26a,b. a A drawing to show the range of metal dummies available for insertion into
`the zero—size cutter, allowing the preparation of dowel cavities of pre—determined depth,
`depending on the depth of the disc space in individual patients. The depth of the space is
`checked at operation by control X-ray with the use of the bent needle as indicated in Figs.
`7.23a,b,c. At the bottom of the drawing, note the dummy assembled inside the cutters. b A
`drawing to depict the cutter in use, demonstrating the mechanism of safety protection provided
`by the 12.5 mm dummy which has been inserted after removal of the starter centre piece. Note
`also that the surgeon is able to count the rings on the outer side of the cutter, providing a double
`safety factor. (See pp 243 for a detailed description of the technique for cutting the dowel cavity)
`
`
`261
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`

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`
`Surgery of the Cervical Spine
`
`Figures 7.28a—c. a A drawing to show the method of use of the tooled gouge for removal of
`the plug of the vertebral bodies and disc following the use of the cutter as depicted in Figs.
`7.26a,b. b A drawing to illustrate the use of a fine curette (2 mm cup) for removal of the
`vertebral end-plate remnants shown in yellow, after the plug of disc tissue sandwiched between
`vertebral end-plate margins has been displaced with the gouge and removed with a straight
`pituitary rongeur. c A drawing depicting the use of the fine curette (2 mm cup) showing the
`prepared dowel cavity from in front with the curette removing remnants of vertebral end-plate
`cartilage and disc tissue in the region of the left—sided unco—vertebral joint. It is possible to
`remove virtually all disc tissue and vertebral end-plate remnants in this manner
`
`The fourth and final stage of preparation _of the intervcrtebral space now
`commences, leading up to the actual impaction of the bone graft, Vertebral end-
`plate cartilage. remnants are removed with a fine curette (1 or 2 mm cup), disc
`remnants attached, as illustrated in Figs. 7.28b,c. Care is taken to avoid damaging
`the vertebral arteries (Figs. 7.1 a, b).
`Longitudinal traction applied to the skull by the anaesthetist will result in
`opening up of the intervertebral space, allowing the surgeon to see the posterior
`longitudinal ligament in the depths of the dowel cavity. Through visible defects in
`this ligament in cases of sequestration of disc fragments into the cervical spinal canal,
`it is possible to remove the displaced disc tissue from the canal.
`Excision of osteophytic bars of bone from the anterior aspect of the cewical
`spinal canal may be required in cases of cervical myelopathy. Depending on the
`
`
`262
`
`

`

`
`
`Technique of Anterior Cervical Interbody Fusions
`
`249
`
`transverse width of the disc, two overlapping dowel cavities may be cut, allowing a
`wider exposure for this delicate, and potentially dangerous, task.
`The use of a high-speed drill with rounded diamond-tipped burrs is essential
`and facilities for good lighting, suction, irrigation and magnification are required. A
`small piece of plastic catheter should be fixed to the tip of the sucker to prevent it
`being damaged by the drill burr. Two or three vertebral levels are often involved and
`the decision needs to be made either to decompress and fuse individual levels or to
`excise intervening vertebral bodies and insert a strut graft (Fig. 7.29). In either case,
`the use of autogenous grafts cut from the iliac crest can be recommended. Fibular
`strut grafts are used by some authors but they are slow to vascularize.
`
`Figure 7.29. A lateral radiograph of the spine of the patient whose pre-operative films are
`illustrated in Figs. 7.4a,b. This patient had clinical evidence of cervical myelopathy with a
`spastic gait and weak upper extremities. Note the positioning of the interbody graft which is
`already incorporating. Note also that the large osteophyte has been excised completely from the
`front of the cervical vertebral column
`
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`Surgery of the Cervical Spine
`
`
`
`
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`Technique of Anterior Cervical Interbody Fusions
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`251
`
`The vertebral osteophytes which project into the cervical canal are often sur-
`prisingly hard and thick. They can be drilled to egg-shell thinness before being
`removed from the dural surface with fine angled curettes. Occasionally ossified
`remnants of the posterior longitudinal ligament are adherent to the dura. They
`should not be removed for fear of producing dural injury and CSF leakage, problems
`not easily dealt with in this location. Recovery of neurological function in many of
`these cases is often gratifying though, in severely disabled patients, degrees of
`recovery vary and may be delayed for upwards of two years after operation.
`Internal fixation is rarely indicated when strut grafts are used. However, special
`corsets or braces should be fitted (Figs. 7.30—32).
`
`Figure 7.31
`
`Figure 7.32
`
`Figure 7.31. A photograph of an adjustable cervical collar of the Zimmer type, which can
`provide effective immobilization following multi-level cervical fusions and which may be used
`later in C1/2 fusions following removal of halo jackets or Minerva jackets
`
`Figure 7.32. A photograph of a SOMI brace which provides an adjustable occipital support and
`an adjustable mental support fitted to a stemal plate. It is suspended over the shoulder and fixed
`firmly to the trunk with adjustable straps. On cine-radiography this has been shown to be one of
`the most effective devices for immobilizing the cervical spine. However, there are problems
`with its management as it tends to ride up when the patient lies in bed.
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`g) Graft Preparation
`
`i) Autogenous Grafts
`
`Autogenous grafts should be cut from the anterior third of the iliac crest. If only a
`single graft is required, this may be cut through a small vertical skin incision placed
`2 or 3 cm behind the anterior superior iliac spine, splitting the fibres of tensor fascia
`lata in the line of the skin cut. The cutting cylinder must be one size larger than that
`used to prepare the dowel cavity in the neck.
`Alternatively, using a short incision along the line of the inner margin of the
`anterior third of the iliac crest, a limited sub-periosteal exposure of the inner table of
`the iliac crest can be made, the cutter then being inserted to cut a bone plug
`extending from the inner to outer table of the ilium.
`When more than one graft is required, the skin incision should run parallel to
`the iliac crest about 1 cm below it. The fascia lata is cut 1 cm below its upper
`attachment to the iliac crest and the muscles of the outer table of the ilium stripped
`down sufficiently to allow easy access for removal of the desired number of grafts.
`During wound closure, a suction drain tube should be inserted. The sutures should
`be placed deeply into the muscle mass from within-out, allowing the fibres of the
`tensor fascia lata muscle to be pulled up towards its former site of attachment on the
`outer wall of the iliac crest. If the sutures approximate only the fascial coverings near
`the margins of the incision, a noticeably ugly defect results in the zone of attachment
`of the tensor fascia lata below the iliac crest.
`
`For rare indications, long strut grafts may be required to bridge multiple verte-
`bral levels, where, for example, a cervical kyphotic deformity is being corrected (Fig.
`7.11), or after excision of vertebral bodies for tumour or infection. Fibular grafts
`have been advocated for use in such circumstances. In my view, it is preferable to use
`long grafts cut from the ilium, to include both cortical surfaces, with cancellous bone
`between. These grafts will vascularize more rapidly than fibular grafts, the latter
`being useful only in exceptional circumstances.
`
`ii) Bone Graft Substitutes
`
`Ceramic dowels constructed of a “cancellous core” (pore size in excess of 100 u)
`capped on either end by dense “cortical” ceramic plates, have been used successfully
`in man‘ (Figs. 7.33,7.34).
`Titanium mesh implants have given rise to serious problems due to collapse,
`extrusion and fragmentation in some cases. They cannot therefore be confidently
`recommended for use in vertebral interbodyfusion operations either in the neck or
`other areas of the spine (Figs. 7.35, 7.36).
`
`Figure 7.33. A detailed lateral radiograph showing a “cortico—cancellous” ceramic dowel 6
`months after insertion.
`
`Figure 7.34. An axial CI‘ image showing a “cortico—cancellous” ceramic dowel covered
`anteriorly by a thin operculum of bone, well incorporated in the vertebral body
`
`‘ Manufactured by Kyocera Corporation, Kyoto, Japan.
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`Technique of Anterior Cervical Interbody Fusions
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`253
`
`Figure 7.33
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`‘
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`Figure 7.34
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`Surgery of the Cervical Spine
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`alum
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`M.»mouawwm
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`Technique of Anterior Cervical Interbody Fusions
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`255
`
`h) Graft Impaction
`
`The final critical manoeuvres required to seat the graft in the dowel cavity are
`illustrated in Figs. 7.37 a—d. Before insertion of the graft, the surgeon must always
`measure the depth of the dowel cavity and the depth of the graft. Great force is
`never required during their impaction. Soft tissues should be carefully retracted
`from the margins of the cavity and the neck should be gently elongated by traction
`applied to the skull before the graft is inserted.
`
`1') Wound Closure
`
`After the grafts have been inserted, a careful inspection should be made of the
`anterior aspect of the vertebrae; any bleeding points should be coagulated, espe-
`cially along the medial margins of the longus colli muscles.
`The neck wound may be closed, without drainage, except after multi-level
`fusions or in rare circumstances after associated thyroid surgery.
`
`
`
`Figure 7.36. A photograph of the fragmented titanium mesh graft removed from the cervical
`spine of the patient whose X-rays are shown in Figs. 35 a—c. Soft tissues stained an intense black
`colour were mingled with the titanium strands
`
`Figures 7.35 a—c. a A lateral X-ray of the cervical spine of a female patient aged 42 years
`showing a titanium mesh implant approximately 3 months after insertion. b Six months after
`insertion, the implant has collapsed and partially extruded anteriorly. The patient’s symptoms
`of neck pain and brachial