RESULTADOS DEL TRABAJO DE CAMPO
2. EVALUACION AREA ESTRUCTURA Y PROCESOS
2.1. LOS PROCESOS
This technique is not commonly used. It offers the ability, by means of a minimal access approach, to correct scoliosis with the use of a thoracoscope.
This leaves the patient with four 2 cm cuts overlying the ribs laterally, which certainly gives a good cosmetic result. This technique has a steep and long learning curve with extended operating times in the initial phase. Some concerns remain with regard to the degree of correction obtained and the success of fusion with this approach.
POSTOPERATIVE CARE AND INSTRUCTIONS
• Neurovascular observations and analgesia are used as needed.
• Oral intake begins with clear fluids and signs of ileus are watched for.
• Postoperative haemoglobin and renal function levels are checked.
• The chest drain is removed when 24-hour drainage is satisfactory, e.g. <125 mL.
• The patient can sit to any angle and mobilize as pain allows.
• Postoperative chest and spine X-rays are taken.
• Some surgeons fit their patients with a custom-moulded thoracolumbar orthosis for up to 6 months postoperatively. This requires casting a few days after surgery, once the patient can stand for 10–15 minutes.
• Neurological injury – in patients waking up with complete motor and sensory loss the hardware should be removed immediately, with adequate blood pressure maintained, and steroids should be considered. Patients in whom root compression/injury is suspected should
Caudal epidural 37
POSTOPERATIVE INSTRUCTIONS
The patient can be discharged on the day of surgery, once they can pass urine postoperatively.
An outpatient review of the result of the epidural is arranged in 4–6 weeks.
LUMBAR
DECOMPRESSION/FIXATION/FUSION PREOPERATIVE PLANNING
The area of spinal fusion is controversial and a discussion of all the arguments for and against its use in spinal practice is beyond the scope of this chapter. It is fair, however, to state that there is no
SURGICAL TECHNIQUE Landmarks
The insertion point for the caudal needle lies at the most superior margin of the gluteal cleft and is felt as a ‘defect’ or opening in the sacrum, the sacral hiatus.
Procedure
Fluoroscopy is used in a lateral position to check the needle position, and 5 mL of Omnipaque 300, mixed with an equal volume of saline, is inserted and an epidurogram taken (Fig. 4.8). Once the needle is seen to be in a good position, the local anaesthetic mixed with steroid is injected.
Figure 4.8 An epidurogram from a caudal epidural
ideal solution for back pain and most procedures with or without fusion are performed for leg symptoms. Fusion is needed in cases of instability or where decompression is likely to cause instability in the long term.
Indications
• Spondylolisthesis
• Lumbar spinal trauma
• Spinal stenosis associated with instability or degenerative disc disease
• Degenerative deformities.
Contraindications
• Smoking (may lead to non-union)
• When the patient’s expectations are not in line with the surgeon’s views
• Waddell’s abnormal illness behaviours, e.g.
widespread non-anatomical pain, pain on axial compression or rotation, straight leg raise which improves with distraction and general over-reaction to pain
• Back pain is the main symptom (proceed with caution).
Operative planning
• A full history and examination is taken from the patient. Specifically, symptoms of spinal stenosis, nerve root compression, involvement of bladder and bowels are enquired about
• Plain X-rays are taken to exclude deformity and fracture, and to use as a baseline for levels intraoperatively
Consent and risks
• Nerve injury: 1 per cent
• Cauda equina injury: 0.1 per cent
• Infection: 1–2 per cent
• DVT/pulmonary embolism: 1 per cent
• Improvement in symptoms: 85 per cent for leg pain; no change 10 per cent; worsening 5 per cent
• Non-union: 5 per cent
• Dural tear
• An MRI scan is ordered preoperatively. Blood tests may be indicated preoperatively to exclude infection where discitis is suspected.
Scans should be reviewed with the patient. All forms of conservative treatment must be exhausted before spinal fusion is considered.
The patient’s expectations must be managed in order to achieve the best result. It is sensible for the surgeon to meet the patient several times pre operatively.
• An anaesthetic assessment may be needed preoperatively. A cell saver should be considered for extensive fusions and if deformity correction is to be performed, spinal cord monitoring should be undertaken
Anaesthesia and positioning
The patient should be preferably positioned prone and on a Montreal mattress or Jackson frame. The mattress has a central cut-out, allowing the abdomen to be free during the operation. This may well contribute to limiting blood loss. If fusion is not planned the spine can be flexed to facilitate the decompression. The arms are placed on arm boards with the shoulders at 90°. It is important to check that there is no pressure on the eyes or the ulnar nerves at the elbow and that the shoulders are safely positioned.
Anaesthetic is general, postoperative pain relief can be augmented with an intraoperative epidural and the catheter can be left in postoperatively.
Hypotensive anaesthesia is useful in reducing intraoperative blood loss.
SURGICAL TECHNIQUE Landmarks
For a guide to surface anatomy please see Figure 4.9 – note that the thoracic levels relate to the scapula and thus will change if the arms are not by the sides. In addition, the level of the top of the iliac crests varies from the L3/4 disc to the L4/5 disc, especially with transitional lumbosacral vertebrae, and correlation with plain X-rays is important. X-ray guidance can be used at the start of the operation to mark levels and, once a level is confirmed, it is possible to count up or down on the spinous processes.
Lumbar decompression/fixation/fusion 39
Soft tissue is stripped off the spine laterally until the transverse process is clearly seen. A Holman retractor can be placed over the lateral edge of the transverse process to aid in retraction.
The pedicle in the lumbar spine corresponds to the junction of the transverse process, superior facet and the pars. The superior facet can be removed to aid visualization of the pedicle entry point as long as this is not at the top level of the fusion. Bleeding must be controlled at all times.
Procedure
Once dissection is complete, it is important to use X-ray guidance to mark the correct level. This can be done by means of a marker on a spinous process or pedicle.
Once the level is identified, screws can be inserted as necessary. Screws are inserted at the confluence of the pars, transverse process and facet (see Fig. 4.11, p. 36). Following screw insertion, rods can be inserted and distraction or compression applied as needed. Following instrumentation, decompression can be undertaken if required.
There are many ways of performing this procedure, and the authors’ preference is to use a burr and an osteotome to remove the lamina.
Nerve roots are then explored and an undercutting facetectomy can be performed using an osteotome or up-cutting punch. It is important that nerves are decompressed both in the lateral recesses and out through the foramen. The foramen can be enlarged by applying distraction through the screw construct.
Dural breach occurs in up to 5 per cent of procedures and can be repaired using 5-0 Prolene suture by means of an interrupted or continuous technique. Other options include blood, fascia or fat patches, dural ‘glues’ or membranes designed to seal dural leaks, such as DuraGen.
The wound is closed in layers. If a dural leak has
Structures at risk
• Dura
• Nerve root
Incision
Following adequate positioning of the patient and level identification, a midline longitudinal incision is made.
Dissection
Subcutaneous tissues, fat and fascia are incised in line with the skin. Haemostasis is obtained. A Cobb retractor is used to put the paraspinal musculature under tension. Diathermy is then used to resect the musculature off the posterior vertebra. On an initial first pass the muscles are dissected from the spinous processes and laminae onto the medial border of the facets. It is important not to damage the facet joints and while performing a fusion, the superior facet joint in the fusion should be protected and not violated.
The wound is packed on each side and deeper retractors inserted. When performing an instru -mented fusion it is important that the pedicle entry points are clearly seen. In the lumbar spine this involves the visualization of the pars, and the junction of the transverse process and the facet.
T3
T7
L4 S2
Figure 4.9 Anatomical levels in the lumbar spine
Operative planning
An MRI scan is performed prior to surgery. Plain X-rays are useful in assessing transition levels in the lumbar sacral spine. Symptoms should be reviewed prior to surgery, as there is a good chance that the patient will have improved since last being seen in clinic.
Anaesthesia and positioning
General anaesthesia is used. Hypotension during the anaesthesia procedure is useful as this may reduce epidural bleeding. The patient can be positioned in one of several ways, and the authors’
preference is to position the patient in the knees to chest position (Fig. 4.10). This position is initially difficult to master but has the advantage of opening the interspinous spaces and allowing easier access to the disc in question. The patient’s knees are moved so they are under the patient’s abdomen and a box is placed underneath the chest. Side supports are used to stabilize the patient. A bar is placed behind the patient’s buttocks to support the trunk. Positioning of the patient on a Montreal mattress, a Wilson frame or a Jackson table is also acceptable.
In the knees to chest position it is important to adequately pad the patient’s pressure points including ulna nerves, shoulders, knees and feet.
The eyes must be free of obstruction.
SURGICAL TECHNIQUE Landmarks
The authors prefer to mark the level pre- and intraoperatively. A needle is placed in the prepared skin at the point which it is estimated that the target level sits. A cross-table lateral X-ray
• Epidural haematoma
• Dural tear: 5 per cent
• Infection: 1–2 per cent
• Wrong level surgery: <1 per cent
• Cauda equina: 0.01 per cent
• Ongoing pain
• Post-discectomy instability leading to back pain
• Blindness occurred it is advisable to either not insert a drain
or if a drain is inserted to have it on free drainage to encourage the leak to seal. Maintain the patient supine for 24–48 hours following the operation to encourage healing of the tear and to avoid the complication of lowpressure headache. Mobiliza -tion should not begin until the patient can sit without headache.
POSTOPERATIVE CARE AND INSTRUCTIONS
Neurovascular observations are undertaken, and drains, if used, are removed at 24 hours. The patient may mobilize as able and can sit to any angle (if there is no dural leak). Analgesia, postoperative bloods and X-rays are recom mended.
RECOMMENDED REFERENCE
Malter AD, McNeney B, Loeser JD, et al. 5-year reoperation rates after different types of lumbar spine surgery. Spine 1998;23:814–20.