rounded, firm or fluctuant protrusions are found with stretched but intact annular
`fibres and, when incised at operation, only a small quantity of disc tissue may escape
`and be removed, leaving in the disc a defect which admits neither curettes nor disc
`rongeurs easily. The consistency of such discs is often described as rubbery. Some
`degenerative annular fibres are usually found with the extruded nuclear tissue in
`
`Pathology
`
`107
`
`Figures 3.2 a—c. Intra-spongeous disc herniation with fracture of the vertebral body margin and
`sequestration of disc fragments into the spinal canal. a Lateral radiograph. A large bony frag-
`ment separated from the posterior-inferior margin of the 4th lumbar vertebral body. It projects
`into the spinal canal. b Antero-posterior view. The L4/5 disc space is narrowed and tilted. There
`is a defect in the central zone of the vertebral end-plate area of the 4th vertebral body. Below
`this, two bony fragments can be identified. These findings were confirmed at operation.
`c Drawing of the position of these fragments. (Courtesy of Mr. K. Mills)
`
`Figure 3.1. A drawing depicting various types of disc prolapses which may be encountered in
`the lumbar region. a A sequestrated disc with fragments migrating distally from its origin at the
`L4/5 interspace. b “A shoulder” prolapse related to the S1 nerve root at its take off point from
`the dural sac. c A central disc prolapse. d An axillary prolapse. e An extra-foraminal prolapse.
`f The common sub—rhizal prolapse. g An intra-foraminal prolapse
`
`
`124
`
`
`
`

`
`108 Disc Prolapses
`
`Extrusion of variable quantities of disc tissue (1.1—13.5 g) into the spinal canal
`may be seen when gross degenerative changes have occurred in the disc as a whole.
`The description of “sequestrated disc fragments” is then applied. The components of
`such fragments may include nuclear, annular and end-plate material.
`'
`Between these two extremes, a variety of pathological changes may be noted.
`Incomplete sequestration may be associated with marked peri-neural fibrosis, a
`finding related to physico-chemical changes in the disc (Nachemson, 1969). Calcified
`nuclear tissue may herniate, or calcification may occur in prolapsed tissue leading
`occasionally to erosion of the dural sac (Blikra, 1969).
`A sequestrated fragment may migrate to another level from the disc of its
`origin, leaving a clearly defined oval defect in the posterior annulus (Fig. 3.1).
`Sequestrated disc tissue may present posterior to the dural sac (Hooper, 1973).
`Rarely, disc tissue may prolapse into the vertebral bodies and re-enter the
`spinal canal, pushing ahead of it a small fragment of vertebral end-plate bone and
`cartilage (Figs. 3.2 a—c).
`In a sub—rhizal prolapse, the disc fragment lies anterior to the affected nerve
`root, and this usually causes severe pain with objective motor and sensory signs
`distally, in the part of the limb supplied by the compressed nerve root.
`Prolapses situated between the dural sac and the nerve root sheath, axillary
`prolapses, or these lying on the outer side of the nerve root sheath, para-rhizal
`prolapses, may produce symptoms of severe sciatica without abnormal objective
`physical signs.
`Centrally placed prolapses or a large migrating sequestrated fragment in the
`spinal canal may give rise to physical signs including bowel or bladder dysfunction
`and neurological signs or symptoms which vary from day to day in one leg or the
`
`Figures 3.3 a,b. MR images with gadolinium enhancement showing marked oedema and ve-
`nous engorgement at L4/5 with an organised left sided sub—rhizal disc prolapse
`
`
`125
`
`
`
`

`
`other. In the lumbar region, cauda equina claudication with the onset of buttock or
`leg pains after walking short distances may also be found (Verbiest, 1955).
`In considering this pathology, the clinician should always give some thought to
`the shape and size of the patient’s spinal canal (Figs. 3.3 a,b).
`
`Investigations
`
`109
`
`3.3. Clinical Features
`
`The classic features of lumbar scoliosis, depression of one or more reflexes in the
`affected limb, muscle weakness or wasting, gross limitation of straight leg raising and
`the finding of areas of impaired sensation over affected dermatomes are all well known.
`Perhaps less well appreciated is the reported observation that the pattern of
`pain radiation into the leg does not differ appreciably in L4/5 and L5/S1 disc lesions.
`In fact, clinical signs caused by lumbar disc prolapses may be misleading. Brown and
`Pont (1963) observed in a review of 570 patients that the ankle jerk may be absent in
`cases of prolapse at L4/5 or at L3/4. They found that sensory changes in the foot
`were more accurate aids in diagnosis than were changes in the leg as a whole.
`In eliciting the physical sign of limitation of straight leg raising as an index of
`sciatic nerve irritation, attempts to lift the leg quickly from the extended position,
`with the patient supine, frequently evoke such a painful response that the straight leg
`can be raised only a few degrees from the examination couch. On the other hand, if
`the knee and hip are cautiously flexed and the knee then extended slowly with the
`examiner’s thumb in the popliteal fossa exerting some pressure on the terminal
`branches of the sciatic nerve, and these manoeuvres are combined with dorsi-flexion
`of the foot, even minor degrees of sciatic nerve irritation can be appreciated. This is
`commonly known as Lasegue’s sign. A patient with convincing sciatica is unable to
`sit upright with both knees fully extended. In the presence of sciatic irritation he will
`automatically flex the hip and knee on the affected side when attempting to adopt
`this posture. This has been described as the “bath-tub sign” by Pennybacker (1959).
`Changes in the clinical features referred to above are all important in assessing
`the progress or failure of recovery of sciatica due to disc prolapse. Of particular
`importance is the severity of pain, especially when it reaches a level which consist-
`ently disturbs sleep at night.
`
`3.4. Investigations
`
`a) Plain X-Rays
`
`These X-rays always provide essential information on the bony anatomy of the
`vertebral column particularly in regard to the arrangement of laminae and the site of
`the lumbo-sacral junction. They are also important for the exclusion of other lesions
`such as spondylosis which may cause confusion in diagnosis. Usually they do not
`provide any useful guide to the site of prolapse.
`
`b) MRI
`
`This is already established as the investigation of choice in the diagnosis of lumbar and
`thoracic disc prolapses. In the cervical spine it is often useful, but CT radiculography
`is more accurate in helping to localize smaller and laterally situated disc prolapses.
`
`
`126
`
`
`
`

`
`Figure 3.4. Coronal reconstruction of a lumbar MRI showing vascular stasis affecting the right
`sided lower lumbar nerve root due to a disc prolapse related to the take off point of this nerve
`root with surrounding oedema spreading centrally
`
`Figures 3.5 a,b. Coronal reconstructions of MR images showing: a an intra-foraminal
`herniation at L5/S1 affecting the right sided L5 nerve root with b marked intra-canalicular
`vascular stasis
`
`
`127
`
`
`
`

`
`Used with gadolinium enhancement it gives accurate definitions of foraminal,
`extra-foraminal, intra-canalicular and sequestrated disc prolapses and shows the
`amazing extent of root oedema or vascular engorgement that occurs adjacent to
`many of these lesions (Figs. 3.3—3.11).
`
`Investigations
`
`111
`
`Figure 3.6. MRI — coronal
`reconstruction showing an
`intra-foraminal prolapse at
`L3/4
`
`Figures 3.7a,b. Coronal reconstructions of MR images showing: 2 sequestration of the L4/5
`disc with b an intra—forarninal sequestration and surrounding oedema
`
`
`128
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`
`
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`
`Figure 3.10. An axial MR image showing an extra—foraminal prolapse in the lumbar region
`
`
`130
`
`
`
`

`
`114 Disc Prolapses
`
`Figure 3.11. A mid-sagittal T2 weighted MR image showing a large thoracic disc prolapse
`projecting on to the dural sac and indenting the spinal cord
`
`
`131
`
`
`
`

`
`Investigations
`
`115
`
`c) Myelography
`
`The introduction of water soluble myelographic media such as Metrizamide or
`Omnipaque in recent years has greatly enhanced the accuracy of diagnosis of disc
`prolapses, particularly in combination with CT examination.
`When MRI and CT examinations are not available, myelography should be
`used as a routine pre-operative investigation in cases of suspected disc prolapse. It
`is invaluable in the investigation of any atypical case and is especially useful in
`cases of suspected disc prolapse where there is advanced spondylosis shown on the
`plain x-rays, or in the presence of bony anomalies such as lumbar sacralisation.
`In these cases it will aid in the diagnosis of associated spinal canal stenosis
`(Fig. 3.12 a,b), or it may help to identify the level of origin of a disc sequestrum and
`its distribution in the spinal canal (Figs. 3.13-3.15).
`
`Figures 3.12a,b. Disc prolapse into a congenital narrow lumbar canal. A 62 year-old man
`(weight 110 kg) lifted a bag of oement, flexing and rotating his spine. He developed back pain
`and severe bilateral leg pain; these symptoms were relieved following excision of a small disc
`fragment and bilateral nerve root canal decompression laminectomy. a Lateral and b antero—
`posterior radiographs of the lumbar myelogram, showing gross obstruction of the iofendylate
`column. Note the symmetrical indentation at the upper end of the lower iofendylate column in
`(b) (marker), suggesting the association of true spinal stenosis. (Courtesy of Mr. B. Davie)
`
`
`132
`
`
`
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`133
`
`
`
`

`
`Investigations
`
`117
`
`Figures 3.14a,b. a A right-sided, slightly oblique view of a radiculogram in a 27 year old male
`showing a large central and right sided filling defect at L5/S 1. This represented a massive disc
`sequestration stemming from the L5/S 1 disc and extending distally in to the sacral spinal canal
`between the S 1 and the S2 nerve roots. h A photograph of the specimen removed at operation.
`This consisted of mixed elements of disc tissue including vertebral end~plate cartilage
`
`
`134
`
`
`
`

`
`118 Disc Prolapses
`
`Figures 3.15a-d. Massive disc sequestration following twisting of the lumbar spine treated by
`disc excision and posterior interbody fusion. A 53 year-old male jeweller suffered from intermit-
`tent back pain for 13 years. While using a powered floor-standing machine, he twisted his spine
`and suddenly developed severe left-sided sciatica. a and b Antero-posterior and lateral radio-
`graphs of the lumbar myelogram, showing a large filling defect at the L4/5 disc space. c The
`sequestrated disc fragments removed at operation. d Lateral radiograph taken after operation
`showing the restored normal outline of the dural sac. Bone grafts are seen between the vertebral
`bodies of L4 and L5; they were inserted through the spinal canal following disc excision
`
`
`135
`
`
`
`

`
`Investigations
`
`119
`
`d) C. S.F Examination
`
`Some authors recommend routine examination of the C.S.F. in the investigation of
`disc lesions, to test its dynamics and contents (Mercer and Duthie, 1964), while‘
`others with extensive experience in the management of spinal conditions rarely do
`so (Armstrong, 1965; Northfield and Osmond-Clarke, 1967).
`The normal protein content of C.S.F. lies between 15 and 40 mg/ml (Bickerstaff,
`1973). In lumbar disc prolapses rises up to 100 mg/ml may be seen, with figures as
`high as 1,000 mg/ml in the presence of marked spinal block. However, many would
`hold the view that changes in the protein content are rarely of practical use in
`diagnosis. Johnson (1972) discusses the mechanisms of absorption of C.S.F. and
`states: “It appears that a subsidiary pathway is via the large spinal veins around the
`emerging nerve roots”. Abnormalities of serum albumin may be found in collagen
`diseases, those changes being reflected in the C.S.F. with the appearance of abnor-
`mal albumins, “para—albumins”, in it. With advances in the understanding of C.S.F.
`physiology, it is logical that surgeons should make greater use of more recent
`biochemical techniques of analysis of this fluid, especially in some of the non-
`prolapsing varieties of disc lesions discussed in this chapter. Whenever myelography
`is undertaken, a sample of C.S.F. should be obtained for cytological and chemical
`testing.
`
`e) Discography
`
`This investigation is rarely indicated as an aid to the diagnosis of disc prolapses. In
`atypical cases of severe sciatica with minimal abnormal physical signs and normal
`myelographic findings, a discogram may help to clarify the diagnosis ( Wilson and
`McCarty, 1969).
`In combination with CT examination foraminal and extra-
`foraminal disc prolapses at unusual sites can be identified.
`
`f) Im‘ra—0sse0us Spinal Venography
`
`Intra—osseous spinal venography has not been used widely in the English-speaking
`world. German observers claim that when it is used with tomography it is just as
`reliable as myelography in the diagnosis of lumbar disc protrusion and prolapse. The
`special value of this procedure is noted in acute cases of massive rnidline prolapses
`involving the cauda equina (Vogelsang, 1970). MRI with gadolinium enhancement
`has rendered this investigation almost obsolete (see Chapter 2).
`
`g) Electrodiagrzostic Tests
`
`Technical and interpretative difficulties in the use of electromyography have been
`described by Simpson (1972).
`
`
`136
`
`
`
`

`
`120 Disc Prolapses
`
`3.5. Indications for Surgical Treatment
`
`Absolute indications for operations are:
`
`a) Major neurological deficits, such as: Acute cauda equina compression due to
`massive disc sequestration or the prolapse of a small fragment of disc tissue into
`an abnormally small lumbar spinal canal; paraparesis due to thoracic disc pro-
`lapse, brachial paresis or quadriparesis due to cervical disc prolapse.
`b) Persistent or recurrent pain, with or without abnormal physical signs, in the
`extremities. This is the most common indication for surgery after an adequate
`trial of conservative treatment in cases of lumbar or cervical disc lesions.
`c) Progressive neurological deficits, such as paraparesis, foot drop or quadri-
`paresis.
`d) Persistent spinal deformity, such as lumbar scoliosis or marked lumbar flexion
`deformity which may be found in certain cases of lumbar disc prolapse or spinal
`tumour.
`
`3.6. Treatment for Lumbar Disc Prolapses
`
`a) Discussion
`
`i) Surgery
`
`In the lumbar region, a limited unilateral inter-laminar approach may suffice for the
`removal of discrete small rubbery disc prolapses, but it can only be recommended in
`young people. Where disc sequestration has occurred or in cases where rather
`desiccated disc tissue is found, more extensive intra-disc space curettage should be
`carried out and at the same time a careful bilateral nerve root canal decompression
`perfonned. Such a procedure performed at the time of laminectomy for disc frag-
`ment excision reduces the late problems of recurrent nerve root irritation that may
`arise from nerve root canal stenosis on one or both sides, resulting from secondary
`disc space narrowing. In these circumstances, there is little justification for extending
`the operation to include posterior spinal fusion (Spurling, 1949). Indeed, the failure
`rate is high, graft resorption being very common when inter-laminar fusion has been
`attempted after exploration of the spinal canal. In addition, late spinal canal stenosis
`may lead to recurrent symptoms which are difficult to manage. Postero—lateral inter-
`transverse fusion is more reliable in these circumstances if spinal fusion seems
`warranted because of gross vertebral instability (Watkins, 1959).
`From the point of view of the relief of sciatic pain, recent long term reviews
`indicate that “laminectomy” alone will produce good results (Jackson, 1971; Naylor,
`1974), variations in the actual technique of laminectomy exerting little effect on the
`outcome.
`
`Where most of the disc remnants are removed in some cases of massive disc
`sequestration, gross vertebral instability can occur. Posterior interbody spinal fusion
`performed through the spinal canal, either by the technique described by Cloward
`(1952) or that recommended by Wiltberger and Abbott (1958), offers a solution to a
`difficult problem (Fig. 3.15 d).
`
`
`137
`
`
`
`

`
`Treatment for Lumbar Disc Prolapses
`
`121
`
`Numerous reviews analyzing the results of various forms of treatment for disc
`prolapse and spondylosis in the lumbar region are available. Basically it is impossible
`to compare series published by different authors for two reasons: firstly, because
`indications for operation vary so widely; secondly, because the operative techniques '
`and pathological findings described are also variable.
`
`Authors everywhere agree on a number of matters:
`
`— compensation patients always respond more slowly to treatment than do private
`patients;
`the results of simple disc fragment excision for frank disc prolapse are good in
`more than 80% of cases;
`prolonged paralysis before operation may not recover completely following it;
`and
`
`paralysis seen for the first time after operation usually recovers rapidly and
`completely.
`
`Cervical disc prolapses can be treated almost exclusively by anterior disc excision
`thereby avoiding the more painful procedure of posterior exploration of the cervical
`canal.
`
`Thoracic disc prolapses are rare. They are usually found between T9 and T12
`vertebrae though upper thoracic lesions do occur. MRI has increased the rate and
`accuracy of their diagnosis (Fig. 3.11).
`
`ii) Chymopapain
`
`Intra-discal injection of chymopapain (Disease), a proteolytic enzyme, was intro-
`duced into clinical practice in 1963 for the treatment of disc prolapse (Smith and
`Brown, 1967). Clinical diagnosis is confirmed by discography, following which the
`enzyme preparation is injected through the discogram needle.
`' Biochemists have been sceptical of its use because of the difficulty of standardi-
`zation of the enzyme preparations and the potential for damage of tissues other than
`nucleus pulposus, should it escape from the intervertebral disc space (Lowther,
`1972). Chymopapain, nonetheless, found its way into quite wide use especially in
`some parts of the U.S.A. and Canada. The difficulties in assessing its efficacy in
`treatment have been highlighted by MacNab (1973), because there is no general
`agreement on clinical syndromes presented by a disc herniation. He quotes the
`following results assembled from a nationwide review undertaken by Lyman Smith
`in 1972: in 2,557 patients there was marked irnprovernent in 1,769 (70%), slight
`improvement in 340 (13%) and no improvement in 448 cases (17%).
`Although chemonucleolysis is no longer widely used in North America even by
`its former most ardent proponents, persistent interest in this method of treatment
`has led to the establishment of a Society for Intradiscal Therapy.
`A number of controversies continue to provoke deb ate. Anaphylaxis, the major
`life threatening complication has attracted most attention, leading to developments
`such as prophylactic skin testing and medication regimes. Arguments about the
`administration of chymopapain under general anaesthesia or under neuroleptic an-
`algesia appear to have been resolved in favour of the latter method. Attitudes to the
`use of discography have swung between two absolutes, either contraindication or
`indispensability. The real danger with the use of discography appears to be the over
`
`
`138
`
`
`
`

`
`122 Disc Prolapses
`
`diagnosis of disc prolapses bearing in mind that leakage of dye into the spinal canal is
`not necessarily an indication of the presence of a disc prolapse into the spinal canal.
`Discography. is essential before the injection of any neucleolytic agent into the
`intervertebral discs for one reason only; ifthe discography gives rise to venography of
`the epidural veins, then this should constitute an absolute contra-indication to the
`injection of chymopapain, which may then find its way into the epidural venous
`system and produce major neurological complications such as paraplegia, quadriple-
`gia, or sub-arachnoid haemorrhage.
`Chymopapain is still widely used in Europe particularly in France, Belgium and
`Germany. In the recent monograph Focus on Chemonucleolysis, Bonneville (1988),
`the complications of neucleolysis are discussed and the statement made on page 105
`“The paraparetic and paraplegic syndromes are only found in the North American
`series”. This suggests an immunity on the part of Europeans to these complications.
`This statement is difficult to accept on a scientific basis, particularly when the real
`mechanism of the causation of these complications has remained unexplained.
`
`b) Technique for Surgery
`
`i) Pre-Operative Preparation
`
`These routines are set out in Chapter 10. X—rays of the patient’s spine should always
`be available in the operating theatre.
`
`ii) Anaesthesia
`
`General anaesthesia with muscular relaxation and mechanical ventilation is most
`
`commonly employed. Cardiac monitoring is recommended.
`
`Positioning
`
`Of all the factors which may be critical to the success of this operation, none is more
`important than the position in which the patient is placed before operation com-
`mences. A variety of suitable postures is shown in the following illustrations
`(Figs. 3.16-3.19).
`
`Prone Position
`
`The most versatile and easily managed is the prone position. A supporting sponge
`rubber U—piece is simple to construct and inexpensive. The right arm is shown
`dependent and supported on a well-padded arm rest which is suspended below the
`level of the table. Ulnar neuritis may occur unless the arm is carefully postured in
`this way. The left arm may rest by the patient’s side. The table is angled in the centre.
`The surgeon’s assistant and other observers will have unobstructed views of proce-
`dures throughout the course of the operation. The entire range of surgical manoeu-
`vres that may be required for the execution of even the most complex operation,
`including trans-dural excision of prolapsed disc tissue, can be accomplished in com-
`fort and without undue constraints on the duration of the operation.
`
`
`139
`
`
`
`

`
`Treatment for Lumbar Disc Pi-olapses
`
`123
`
`Figure 3.17. The posturing of the patient on this “U”-piece. The right arm is shown dependent
`and suppoxted on a well-padded arm rest which is suspendedlbelow the level of the table. Ulnar
`neuritis may occur unless the arm is carefully postured in this way. The left arm may rest by the
`patient’s side. The table is angled in the centre
`
`
`140
`
`
`
`

`
`124 Disc Prolapses
`
`Kneeling Position
`
`In this position, with the use of a simple frame to support the buttocks, excellent
`operating conditions are provided. Use of this posture can only be recommended for
`operations of short duration. Alternatively, the patient may be placed in this posi-
`tion with pillows under the chest so that the abdomen is unsupported. A pillow is
`placed under the patient’s feet and a restraining strap across the legs, though venous
`obstruction in the lower limbs is then likely to occur. The table is angled. The major
`objections to the use of this particular posture revolve around the difficulties of
`setting the patient in position and of dealing with emergencies, which may require
`the patient to be turned rapidly into a supine position. Particular attention should be
`paid to the ulnar nerves in this position.
`
`Lateral Position
`
`The use of this position can be recommended in special circumstances, for example,
`when the patient is extremely obese or when there are special chest problems which
`may complicate anaesthesia. A pillow should be placed between the patient’s legs, a
`restraining strap crossing the iliac crest, and a Sandbag placed above the dependent
`iliac crest. The table is angled in the centre. There are objections to the routine use of
`this position: (i) the assistant surgeon is rarely comfortable and has a restricted View
`of the operation field; (ii) lighting of the wound area may be difficult; (iii) haemor-
`rhage control is often more difficult to obtain as is access to the nerve root canal on
`_ the dependent side of the spine.
`
`Figure 3.18l A drawing depicting the kneeling position. A simple frame is used to support the
`buttocks
`
`
`141
`
`
`
`

`
`Treatment for Lumbar Disc Prolapses
`
`125
`
`Figure 3.19. The lateral position. The use of this position can be recommended in special
`circumstances, for example, when the patient is extremely obese or when there are special chest
`problems which may complicate anaesthesia. Note the pillow between the patient’ s legs, the
`restraining strap crossing the iliac crest, the sandbag placed above the dependent iliac crest. The
`table is angled in the centre. There are objections to the routine use of this position: 1. the
`assistant surgeon is rarely comfortable and has a restricted view of the operative field; 2. lighting
`of the wound area may be difficult; 3. haemorrhage control is often more difficult to obtain, as
`is access to the nerve root canal on the dependent side of the spine
`
`iv) Instruments (Figs. 3.20-3.21)
`
`The recommended essential special instruments and disposable supplies are listed
`below:
`
`Self-retaining retractors.
`Fine sucker.
`
`Bayonet forceps.
`Long-handled carrier for size 11 or 15 blade scalpel.
`Watson-Cheyne probe.
`_
`Nerve root retractor, such as a Scaglietti probe (10 inches—25 cm long).
`A range of bone rongeurs,
`A range of pituitary-type rongeurs, straight, angled outwards at 45 degrees and
`at 90 degrees with cutting tips of varying dimensions.
`. Hammer.
`. Fine osteotomes and chisels.
`
`. Ring curettes.
`. 6/0 suture material on fine cutting needles with a fine needle holder.
`. Patties and haemostatic gauze or sponge materials.
`. Bone wax.
`
`. Bi-polar coagulator.
`
`
`142
`
`
`
`

`
`126 Disc Prolapses
`
`Figure 3.20. A photograph showing the modified Gelpi retractors, which are recommended for
`use in almost any situation where the spinal canal is to be explored
`
`Figure 3.21. A photograph of straight and angled pituitary rougeurs which should be available
`in various shaft lengths and cup sizes for use in the surgery of disc prolapses
`
`
`143
`
`
`
`

`
`Treatment for Lumbar Disc Pi-olapses
`
`127
`
`Before the skin incision is made the surgeon should once again inspect the patient’s
`X-rays, paying attention to vertebral anomalies, such as spina bifida occulta and
`sacralization and noting certain lesions such as spondylolisthesis or isolated disc
`resorption. The level of the planned exposure of the spine should be noted.
`Radiographs of the lumbar spine taken in the operating theatre are often of
`poor quality and cannot, therefore, be relied upon to identify a particular spinal
`
`v) Incision
`
`The skin incision is made in the mid-line or slightly to the right or left of the
`spinous processes, extending longitudinally a short distance above and below the
`vertebral interspace to be explored. It is deepened at once through the subcutaneous
`fat layer to the level of the lumbo-dorsal fascia. In extremely obese patients the
`depth of the subcutaneous fat
`layer between the skin and the lumbo-dorsal
`aponeurosis over the lumbo—sacral area may be 12 cm or more. In such cases this
`fatty tissue should be carefully handled, avoiding excessive burning with the coagu-
`lating diathermy (see “Wound Closure”, pp. 144, 145).
`
`vi) Separation of the Paraspinal Muscles
`
`An incision is made in the lumbo-dorsal aponeurosis on one side of the tip of the
`spinous process approximately 5 mm from the mid-line using the cutting current
`diathermy passed through a suitable blade-shaped end. The lumbo-dorsal
`aponeurosis is a thin shining silvery membrane, the fibres of which are orientated
`largely transversely. 'I‘l1is structure acts as an extensor mechanism in lumbar spinal
`movement through its attachments to the powerful latissimus dorsi and abdominal
`wall muscles (Fig. 3.22).
`Immediately beneath it are the silvery vertically orientated fibres of the sacro-
`spinalis aponeurosis (Fig. 3.23). The incision continues proximally and distally adja-
`cent to the sides of the spinous processes and parallel to the interspinous ligaments.
`Some bleeding will occur at this stage from posterior branches of the lumbar arteries
`related to the middle of the side of each spinous process. The muscle mass may be
`retracted with a closed dissecting forceps placed into the depth of the space, so that
`the diathermy blade may cut the musculo—tendinous attachments from the inferior
`surfaces of the spinous processes and laminal margins and from the interspinous
`ligaments near-their bases. Throughout this procedure the smoke generated by the
`diathermy cutting tip may be evacuated with a sucker.
`,
`The muscle mass is next separated from the outer surface of each lamina using
`an appropriate elevator such as the Cobb, taking care to preserve the periosteum of
`the lamina. This manoeuvre should be carried out cautiously and sub—periosteal dis— ’
`section avoided as this inflicts unnecessary damage to the laminal blood supply.
`Following the use of the muscle elevator which raises the paraspinal muscles later-
`ally to the level of the apophyseal joint capsule, which should be carefully preserved,
`further bleeding may be encountered from posterior branches of the lumbar arteries
`and veins in this area. Bleeding is readily controlled following insertion of cotton
`Raytec swabs, (bearing X—ray markers), packed into the depths of the wound along
`its length. When these are removed later, a few individual bleeding vessels may need
`to be coagulated with diathermy.
`
`
`144
`
`
`
`

`
`I28 Disc Prolapses
`
`If necessary the same approach is then repeated on the opposite side -of the
`spinous processes, preserving the inters‘pinous ligaments until the‘ paraspinal muscle
`inafilmsbemifinnmrwsemnamdfnmiHwrvofofmesmnmcmnm.ConmLRawec
`swabs are again inserted and a sell’-retaining retractor oflhe surgeons’s choice is
`then prepared for insertion. When a small unilateral disc prolapse is to be removed.
`special re tractors, are available which will permit cxp,osure.ol" the intcrlaminar space
`on one side only. These vary from speculum shaped instruments to rctractors with
`one narrow blade coupled with a probe—like limb. These are advocated by surgeonis
`who practise miem-cliseectoiny or so called minimal intervention surgery.
`
`Figure 3.22
`
`
`145
`
`
`
`

`
`Treatment for Lmnbnr Disc Prolapscs
`
`I29
`
`Figunrc. 3.23. A pliotogruph of 21 tlissection.'c'>l' the |_tin1l.n)-s£l't;m| shine seen from behind. In the
`lo\\'ei_'3.l_ialf of the specimen ‘on the left side. the intact th0ra'co-lumlvar Fascia is set-2:1 with its
`shining silver fibres orientated largely l.1'ansve'1sely. Above t'l1'i.¢‘; "the pumspinal muscles have
`been rcnwved. On the right side the c'ut etlge of Lhc tl1o1'2ico-lunibzir fascia is visible. Beiidiitli
`U1is.lhin membrane the vertically orientated ziponeurolic fibr'é's ofithc sz'ic1'nspina'lis muscles can
`be seen. [Reproduced with per'mis"sion tiftlie editor John
`Ni-'xnn l'rom: Spin-.11 Stenusis. 1). 2l,
`Lumlun: l3d\va1'L| Arnold. I991]
`
`Figure 3.22. A photogrupli of :1 dissection ofilie muscles of the back to show the large tria_ngulm-
`shaped luinlm—c|m'sal aponcurosis. the apex 0|‘ which extencls up towarcls to the I11ic|-ll1(_n"uci"c
`spine. the base (it which lies '.1cro:s.s‘ the iliac e_i'es'is i1_1l'erierly. The Flllt1ChlTlCI1l.‘€ ol‘ the latissimus
`dorsi and zibclominul muscles to its lateral edge gm laoth-sides cam be seen. (Photogrnpliccl with
`the permission of the Dean of the Faculty of Medicine l’mfe_ss0r Graham Ryan in Ilu:-University
`0|’ Melbourne)
`
`
`146
`
`
`
`

`
`130 Disc Prolapses
`
`Unless the technique described is followed carefully, considerable blood loss
`may occur, even during this preliminary stage of the approach to the disc prolapse
`(Figs. 324,325). Presuming both sides of an intervertebral disc space are to be
`exposed the cotton Raytec swabs are removed from the lower end of the wound on
`either side of the