Kyphoscoliosis may be congenital, associated with neuromuscular disorders (e.g. muscular dystrophies, neurofibromatosis, poliomyelitis or cerebral palsy) or idiopathic. Idiopathic kyphoscoliosis is much more common in females than males (ratio of 4:1) and accounts for 80% of all cases of kyphoscoliosis.
Progressive kyphoscoliosis is almost invariably accompanied by progressive symptoms and signs of restrictive pulmonary disease, and ultimately, if left uncorrected, it leads to pulmonary hypertension and death.
Severe uncorrected kyphoscoliosis is extremely uncommon in the UK, and most women presenting to the antenatal clinic will either have mild deformity or will have had corrective orthopaedic surgery.
Problems and special considerations
Although kyphoscoliosis in pregnant women is likely to be idiopathic, alternative causes are important to eliminate. Neurofibromatosis is associated with other serious complications (intracranial tumours, congenital heart disease), and familial dysautonomia, characterised by massive swings in blood pressure and generalised autonomic dysfunction, is associated with kyphoscoliosis in 90% of cases. If kyphoscoliosis is associated with neuromuscular disease, respiratory function may be compromised by the underlying disorder in addition to the structural abnormality.
The bony pelvis is normal in women with idiopathic scoliosis, and there is no increase in the incidence of malpresentation or prolonged labour; caesarean delivery should be reserved for obstetric indications. However, if spinal instrumentation extends near the lumbosacral junction, this may impair sacral movement and interfere with descent of the fetus within the pelvis.
Women who have had corrective surgery have two major sources of potential morbidity: firstly residual cardiorespiratory disease, and secondly limited access to the thoracolumbar spine.
Management options
Antenatal assessment is important, and access to previous medical records, x-ray films and magnetic resonance imaging scans, where available, should be sought as early as possible in the pregnancy. Respiratory function tests can readily be performed on an outpatient basis and may be repeated later in the pregnancy to assess any deterioration. It has been suggested that correction of scoliosis improves respiratory function, whereas in women with uncorrected scoliosis, cardiorespiratory function is likely to deteriorate further as a result of pregnancy. Increased cardiorespiratory demand, coupled with reduced functional residual capacity and the inability to increase minute ventilation because of restrictive lung disease, may lead to respiratory compromise.
In women with corrected scoliosis, the major problem for the anaesthetist is provision of regional analgesia and anaesthesia. The most common means of correction of kyphoscoliosis is with Harrington rods or with the newer adaptations, Luque and Cotrel-Dubousset instrumentation. Each technique involves metal instrumentation and bone grafting. Thoracoplasty is sometimes also offered as an additional surgical procedure in order to reduce the rib ‘hump’ that affects some patients. This is also used to obtain bone grafts from the ribs instead of the pelvis. Although preservation of the L5/S1 interspace is a cardinal orthopaedic rule, instrumentation and grafting may extend down to L4/5 in up to 20% of cases. The level of skin scar is a poor guide to the level of fixation, and therefore operation notes and/or imaging results are extremely helpful during antenatal assessment. If there is no pre-pregnancy imaging available, and there is doubt about the extent of instrumentation of the lumbar spine, relevant radiography may be performed during the third trimester of pregnancy. Assessment and written documentation of any existing neurological deficit and any pre-existing back pain is important.
Successful insertion of both epidural and spinal needles is well described in women with Harrington rod fixation, but women should be warned that the procedure may be technically difficult. Neuraxial techniques are unlikely to be successful at the site of fixation owing to the presence of metalwork, bone graft material and scar tissue; insertion above or below is recommended. False loss of resistance has been described, and the risk of accidental dural puncture is increased. There is an increased risk of patchy analgesia or anaesthesia with epidural techniques, thought to be caused by epidural adhesions and scarring following disruption of the ligamentum flavum.
Because of the potential problems of epidural analgesia and anaesthesia, spinal techniques may offer significant advantages. Spinal needle insertion at the L5/S1 interspace is more likely to be successful, even in very low fusions. There is a definite endpoint, which overcomes the problem of false loss of resistance, and deliberate dural puncture with an appropriate needle avoids the risks of accidental dural puncture with an epidural needle. Spread of local anaesthetic within the cerebrospinal fluid is unlikely to be affected by previous surgery, and therefore anaesthesia for operative delivery is more reliable with spinal than with epidural techniques. There are theoretical reasons to recommend continuous spinal catheter analgesia for labour as an alternative to epidural analgesia, depending on local expertise and familiarity with the technique.
In cases of uncorrected scoliosis, technical difficulty and an increased incidence of complications should be anticipated for neuraxial techniques; however, a review of patients with scoliosis having neuraxial anaesthesia found that patients with uncorrected scoliosis were more likely to have a successful block than those who had had corrective surgery (79% versus 69%). The anaesthetist should consider that vertebral rotation is likely to be present, making identification of anatomical landmarks and location of the epidural/subarachnoid space more challenging. A paramedian approach may be more successful. Those experienced in the use of ultrasound for neuraxial techniques may find it to be a useful adjunct. Once the correct space is reached, scoliosis may cause pooling and affect spread of local anaesthetic.
It is important to discuss in advance alternative methods of analgesia such as Entonox and patient-controlled intravenous opioids, and the potential need for general anaesthesia in case regional techniques fail. If general anaesthesia is required, the airway may be more difficult due to fixed deformity or reduced mobility of the spine, and care should be given to positioning and padding of pressure points. Combined spinal-epidural techniques are advisable in women with an anticipated difficult airway in whom a regional technique is undertaken.
Key points
• Although at least 80% of kyphoscoliosis is idiopathic, association with other diseases such as neurofibromatosis and familial dysautonomia should not be forgotten.
• Uncorrected progressive kyphoscoliosis leads to severe restrictive pulmonary disease and pulmonary hypertension.
• The major anaesthetic problem in pregnant women with corrected kyphoscoliosis is provision of regional anaesthesia and analgesia. Spinal techniques offer several advantages over epidural.
• Lumbar fusions are unlikely to involve the L5/S1 interspace.
• Radiography of the lumbar spine may be performed during the third trimester to aid management of regional analgesia.
Further reading
Ko JY, Leffert L. Clinical implications of neuraxial anesthesia in the parturient with scoliosis. Anesth Analg 2009; 109: 1930-4.
Smith PS, Wilson RC, Robinson AP, Lyons GR. Regional blockade for delivery in women with scoliosis or previous spinal surgery. Int J Obstet Anesth 2003; 12: 17-22.