Surgical Management of Kyphosis and Hyperlordosis in Children with Cerebral Palsy
Sagittal plane spinal deformities, excessive kyphosis or lordosis may occur in the child with cerebral palsy (CP) and may be seen either with or without scoliosis. These spinal deformities may cause difficulty with seating and/or pain, especially when the deformity is greater than 70 degrees. And hyperlordosis has also been reported to cause superior mesenteric artery syndrome. Pain and difficulty with seating are the most common indications for correcting sagittal plane spinal deformities in the child with CP. Mild and some moderate sagittal plane deformities can be treated by wheelchair modifications and bracing. Symptomatic moderate and severe deformity may require surgical treatment. More flexible kyphosis and hyperlordosis can be corrected by posterior spinal fusion and segmental instrumentation alone while rigid deformity may require posterior osteotomies (for kyphosis) or anterior discectomies (for hyperlordosis). Instrumentation and correction techniques vary from screw/rod constructs using distraction/compression correction to wire or screw/rod constructs using cantilever correction. Overall, natural history and surgical outcome studies focused solely on sagittal plane spinal deformities in the patient with CP are limited. Those authors that do measure functions report improvements in pain, sitting balance, head and neck control, breathing, and hand use. Patients with kyphosis undergoing spinal fusion with instrumentation are at risk for loss of proximal and/or distal fixation. Patients with hyperlordosis appear to be at greatest risk for postoperative complications.
KeywordsCerebral palsy Neuromuscular Kyphosis Hyperlordosis Sagittal plane Spinal deformity Spinal fusion
Sagittal plane spinal deformities, excessive kyphosis or lordosis may occur in the child with cerebral palsy (CP) and may be seen either with or without scoliosis. These spinal deformities may cause difficulty with seating and/or pain, especially when the deformity is greater than 70 degrees. And hyperlordosis has also been reported to cause superior mesenteric artery syndrome (Lipton et al. 2003; Karampalis and Tsirikos 2014). Pain and difficulty with seating are the most common indications for correcting sagittal plane spinal deformities. Separate surgical strategies are necessary to correct each deformity (Dabney et al. 2004). Similar to scoliosis, the surgical outcomes of corrective spine surgery in the CP child may be adversely affected by associated comorbidities in the CP child. Optimum medical management is therefore important to minimize adverse postoperative outcomes.
Similar to scoliosis in cerebral palsy, sagittal plane deformities are a consequence of muscle imbalance. Iliopsoas contracture can cause lumbar hyperlordosis, severe anterior pelvic tilting, and a horizontal sacrum. On the other hand, McCarthy et al. showed an association between loss of lumbar lordosis or even frank lumbar kyphosis with hamstring contracture that may cause a posteriorly tilted pelvis and a prominent vertically oriented sacrum (McCarthy and Betz 2000; Dabney 2018). Lumbar kyphosis can result in a greater weight-bearing load shifted on to the sacrum resulting in a sacral pressure sore. Truncal hypotonia and poor head control can initially result in postural thoracic kyphosis eventually resulting in a more rigid kyphosis over time. Currently, there is insufficient research to ascertain whether or not the severity of motor involvement is directly proportional to the severity of sagittal plane deformity in CP, although our clinical experience tells us that this is likely the case. Understanding whether or not quality of life is impacted by the sagittal plane spinal deformity should be the main determinant and rationale for treatment.
No current natural history studies exist for either kyphosis or hyperlordosis. On the other hand, the CP child’s life expectancy is largely dependent on the number of comorbidities. Accordingly, the surgeon must recognize if the sagittal plane spinal deformity is having a significant impact on the child’s quality of life or not. In addition, the number and severity of comorbidities may impact the surgical timing and perioperative risks associated with spinal surgery.
Patient Assessment and Preoperative Considerations
After a shared decision-making process between the medical care provider and the family to determine whether to proceed with surgery, all children with CP should have a detailed preoperative medical evaluation similar to that of scoliosis in the child with CP. The surgeon and interdisciplinary medical team must ensure that all associated comorbid conditions are optimized medically. Common comorbidities that exist include gastroesophageal reflux, aspiration pneumonia and reactive airway disease, poor nutrition, seizure disorders, and low bone mineral density and may be risk factors for postoperative complications (Lipton et al. 1999; Samdani et al. 2016; Nishnianidze et al. 2016). Risk factors should be identified preoperatively and comanaged medically (Rappaport et al. 2013a, b; Rappaport and Pressel 2008). The child with CP should also have a detailed neurological examination, including sensory and motor testing, the assessment of upper and lower extremity reflexes as well as abdominal reflexes. This helps to establish the child’s baseline neurological function and serves to assess for any undiagnosed intraspinal pathology such as tumor, tethered cord, or syringomyelia which may also occasionally occur in the child with CP.
The orthopedic preoperative assessment should evaluate sitting and/or standing ability, as well as coronal, sagittal, and rotational deformity of the pelvis. Also, flexibility of the spinal and pelvic deformity is very important to evaluate. The flexibility of kyphosis can be assessed by either physical and/or radiographic examination by placing the child in the supine position and placing a bolster directly under the apex of the kyphosis to determine how well the kyphosis corrects. The flexibility of a hyperlordosis is more difficult to assess, which, however, can be assessed by gently flexing both hips and thighs to the chest with the child in the supine position. Radiographs can also be taken in this position to evaluate flexibility. For better accuracy, the surgeon should position the patient for these radiographs in the x-ray suite instead of allocating them to the x-ray technician. The surgical treatment of more rigid versus stiffer sagittal plane deformities will be discussed later in the chapter.
The assessment for the coexistence of sagittal spinal deformity, hip flexion contracture, and/or adduction contracture is also important. This can be done by performing the Thomas Test, done by stabilizing the pelvis in a neutral position by flexing the opposite hip and assessing for hip flexion contracture on the opposite side. Alternatively, assessing for the presence of hip adduction contracture can be achieved by measuring the amount of abduction achieved with the pelvis in neutral obliquity. If these contractures are present, the parents should be advised that muscle releases may be needed 4–6 months after corrective spine surgery in order to balance infra-pelvic deformity. Also, assessment with an AP radiograph for the presence of hip subluxation should always be done in patients with spinal deformity.
The surgeon should also assess if the pelvis is part of the kyphosis (posterior pelvic tilt) or lordosis, anterior pelvic tilt in order to determine whether instrumentation and fusion to the pelvis will be necessary. In the nonambulatory patient with cerebral palsy (GMFCS VI and V), fusion to the pelvis is almost always necessary to prevent distal extension of the deformity especially when lumbar kyphosis or hyperlordosis are present. Also, patients with poor head control and/or thoracic kyphosis should be considered for instrumentation and fusion up to T1 or T2 to prevent a junctional kyphosis at the cervical-thoracic junction. Patients with very proximal kyphotic deformities may even require instrumentation and fusion into the lower cervical spine.
Another special high-risk group is children who develop severe lumbar lordosis following posterior dorsal rhizotomy for spasticity management. The lordosis component is often very stiff combined with a dense posterior surgical scar. Often the intrathecal nerve roots are also scarred. Correction with strong posterior stretching forces a center of rotation of deformity correction to be in the anterior aspect of the lumbar vertebra requiring large excursion of the nerve roots which will lead to nerve root nerve pain. It is strongly advised in the situation to first focus on anterior spinal shortening with large disk vertebral end plate wedge resections or vertebral body resection. This spinal shortening will allow lordosis correction without stretching the intrathecal neural elements.
The only treatment that can make a permanent impact on the correction of CP sagittal plane deformity is spinal instrumentation and fusion. The standard surgical procedure is a posterior spinal fusion with segmental instrumentation from T1 or T2 down to the sacrum if the pelvis is part of the deformity. The pelvis and lumbar spine is almost always involved in hyperlordosis. Even if the pelvis is not part of the deformity, in the nonambulatory patient (GMFCS level IV and V) or ambulatory patient with poor balance (GMFCS level III), the surgeon should strongly consider fusion to the pelvis to prevent late pelvic deformity (Dabney 2018).
In the past, the gold standard to instrument the correction of neuromuscular scoliosis was Luque rod instrumentation and sublaminar wires with Galveston instrumentation to the pelvis (Ferguson and Allen 1988). This was later improved upon with the Unit Rod (Surgical Treatment of Scoliosis due to Cerebral Palsy) or the cross-linkage of separate rods to prevent rod shift and rotation (Bell et al. 1989; Rinsky 1990; Dias et al. 1996; Sponseller et al. 2009; Peelle et al. 2006; Sink et al. 2003) However, this surgical approach has had mixed outcomes in managing hyperkyphosis and hyperlordosis (Lipton et al. 2003; Karampalis and Tsirikos 2014; Sink et al. 2003).
Medical/Anesthesia Considerations (Anesthesia for Cerebral Palsy Spine Fusion Surgery)
The general medical status of the CP child should be evaluated using a multidisciplinary approach prior to spinal fusion with instrumentation. These considerations are described in more detail in the scoliosis chapter (Medical Evaluation for Preoperative Surgical Planning in the Child with Cerebral Palsy). Increased perioperative morbidity, including increased blood loss, and postoperative infection are associated with increasing lumbar lordosis (Karampalis and Tsirikos 2014; Sponseller et al. 2010a; Sponseller et al. 2013; Jain et al. 2012). Our experience has also shown increased blood loss in patients with hyperlordosis.
Guidelines to prevent infection are described in the scoliosis section and should also be followed for the correction of sagittal plane deformity (Vitale et al. 2013) (Surgical Treatment of Scoliosis due to Cerebral Palsy). In addition, the utilization of tranexamic Acid (TXA) should be followed to reduce blood loss, especially in hyperlordotic deformity (Dhawale et al. 2012). Even with the use of TXA, the surgeon should take additional measures to prepare excessive blood loss when correcting hyperlordosis which include the availability of: typed and cross-matched blood (up to twice the patient’s blood volume), fresh-frozen plasma, and platelets (Brenn et al. 2004). The use of cell-saver blood should be considered. Vascular access through the use of a central line should also be considered in patients with poor peripheral access (Anesthesia for Cerebral Palsy Spine Fusion Surgery). In patients with poor nutrition, a central venous catheter can also be used for postoperative hyperalimentation. We place a central venous catheter in high-risk patients with severe sagittal plane deformity. The use of pedicle screws instead of sublaminar wires has also been reported to have lower blood loss in the correction of scoliosis in CP, and this may also be true in sagittal plane deformity as well (Fuhrhop et al. 2013).
The next important consideration in the correction of sagittal plane deformity in the child with CP is whether the child has low bone mineral density, especially prevalent in the child with CP with: greater motor involvement (GMFCS IV and V), patients on anticonvulsant medications, and patients who are nutritionally deprived (Sees et al. 2016). Adequate bone density is especially important during the cantilever correction of the sagittal plane deformity. These are highest at the apex in lordosis posteriorly and very high posteriorly at the distal- and proximal-most ends of the spine in kyphosis. In both the deformities, wire pull-out when wires are used or screw plowing when pedicle screws are used may occur when low bone mineral density is present. Any nonambulatory child with low-impact long bone fractures should be checked for low bone density using dual energy x-ray absorptiometry (DEXA scan). Intravenous pamidronate is recommended for the child with CP with bone density two or more Z-scores below the mean and with frequent fractures (Sees et al. 2016). Children on seizure medication should have preoperative calcium, phosphorous, and vitamin D levels measured (Managing Bone Fragility in the Child with CP).
The principles of spinal deformity correction for sagittal plane spinal deformity in CP are to: (1) correct coronal, sagittal, and transverse plane pelvic deformity with the sitting or standing surface as a reference plane. (2) Restore coronal and sagittal truncal balance in order to center the head over the trunk and pelvis and correct anatomic sagittal alignment of the trunk and pelvis (average sacral slope of approximately 40°, pelvic tilt 13°, and lumbar lordosis of 40–60°) (SW1 et al. 2013). Nonambulatory children with CP should be corrected to a slightly greater than anatomic lumbar lordosis to balance the child’s body weight over the posterior thigh muscle mass. This helps to prevent sacral decubitus ulcers from occurring. Ambulatory children with CP should have relatively equal lumbar lordosis and thoracic kyphosis in order to optimize standing balance. Suh and colleagues showed a significant difference between sagittal spinopelvic parameters in the CP child compared to normal control children and that these abnormal parameters may be related to the symptoms seen in CP children (SW1 et al. 2013). The correction of these parameters during spine surgery is therefore critically important in the child with primary sagittal plane deformity. (3) Maximize segmental fixation in the face of what is often osteoporotic bone and (4) minimize operative time since children with CP often have multiple comorbidities, excessive bleeding, and a greater risk for wound infection (Sponseller et al. 2010a; Sponseller et al. 2013; Jain et al. 2012).
When planning preoperatively for surgery, three technical questions deserve careful thought: (1) Should fusion include the pelvis? (2) Is there a rotational component to the spinal deformity that is affecting sitting or standing balance that will definitively require pedicle screw fixation over sublaminar wires? (3) Is there poor flexibility of the sagittal deformity that will warrant: preoperative or intraoperative traction, anterior release, concurrent posterior-only osteotomies, or total vertebral resection?
Current Preferred Surgical Treatment Methods (Spinal Procediure Atlas for Cerebral Palsy Deformities)
Fusion to the Pelvis
Only if the patient preoperatively has a level pelvis, a correct sagittal pelvic position, and adequate balance, should the surgeon consider ending the fusion and fixation more proximally at the L4 or L5 vertebrae. If fixation to the pelvis is not done, distal pedicle screw fixation in the lumbar spine at a minimum of four levels is recommended. In severe lumbar lordosis, pedicle screws should be considered at each level. Cantilever correction with fixation using pedicle screws or sublaminar wires to correct the remainder of the sagittal alignment can then be done to complete the thoracic spine correction. Hyperlordosis correction requires another corrective technique that will be described.
Lumbar and Thoracolumbar Kyphosis
Rigid Kyphotic and Hyperlordotic Deformities
Lipton et al. was the first to describe a series of 24 children with cerebral palsy with isolated sagittal plane spinal deformity (8 with hyperlordotic deformity, 14 with kyphotic deformity, and 2 with both) (Lipton et al. 2003). Each sagittal plane deformity underwent posterior spinal fusion and cantilever correction using Unit Rod instrumentation. The indications for surgery included back pain, seating problems despite wheelchair modifications, and two cases of superior mesenteric artery syndrome refractory to conservative treatment in children with hyperlordosis. In children with kyphotic deformity, the mean preoperative kyphosis of 93.8° was corrected to a mean postoperative kyphosis of 35.8°, while the mean preoperative hyperlordosis of 91.8° was corrected to a mean postoperative lordosis of 43.6° in children with hyperlordosis. Postoperatively, caregivers reported improvements in: sitting balance, head control, pain relief, and physical appearance. Both cases of superior mesenteric artery syndrome resolved after spinal deformity correction.
Karampalis and Tsirikos reported on 13 patients with lumbar hyperlordosis and lordoscoliosis who underwent posterior spinal fusion with instrumentation (Karampalis and Tsirikos 2014). The mean lumbar lordosis was corrected from 108° to 62° postoperatively. Sacral slope (horizontal sacral inclination) improved from 79° to 50°. Sagittal imbalance was improved from a mean of −8 cm to −1.8 cm. Preoperative lumbar lordosis and sacral slope had an increased risk of perioperative morbidity. Reduced lumbar lordosis and increased thoracic kyphosis were associated with improved sagittal balance at follow-up. Postoperative questionnaires at the final follow-up showed relief of severe preoperative back pain and improvements in physical appearance and function. There were also improvements in head control, breathing, and hand use (Dabney 2018).
Sink et al. looked at a retrospective case series of 24 patients with patients had preoperative kyphotic deformities (Sink et al. 2003). Preoperative thoracic, thoracolumbar, and lumbar kyphosis were risk factors for loss of proximal and distal sagittal fixation and therefore correction. The authors stated that increased forces at the proximal- and distal-most end (Galveston fixation) of the instrumentation during kyphosis correction resulted in the greatest potential for failure. They recommended reinforcing these ends with stronger fixation. We prefer to use the largest diameter pelvic screw fixation which in our experience is less likely to pull-out compared to the Unit Rod or Galveston fixation. Proximal loss of correction occurred in 11 patients who developed a junctional kyphosis. Securing fixation proximally with two wires, screws, or hooks provide a more secure proximal fixation.
Sagittal plane spinal deformities (kyphosis and hyperlordosis) are uncommon by themselves in cerebral palsy; however, when present can interfere with proper sitting and standing balance. Sagittal plane spinal deformity in conjunction with scoliosis is more common and must be treated surgically as a component of the scoliosis. Mild and some moderate sagittal plane deformities can be treated by wheelchair modifications and bracing. Symptomatic moderate and severe deformity may require surgical treatment. More flexible kyphosis and hyperlordosis can be corrected by posterior spinal fusion and segmental instrumentation alone while rigid deformity usually requires posterior osteotomies (for kyphosis) and/or anterior discectomies (for hyperlordosis). Instrumentation and correction techniques vary from screw/rod constructs using distraction/compression correction to wire or screw/rod constructs using cantilever correction. Overall, natural history and surgical outcome studies focused solely on sagittal plane spinal deformities in CP are limited. Those authors that do measure functions report improvements in pain, sitting balance, head and neck control, breathing, and hand use. Patients with kyphosis undergoing spinal fusion with instrumentation are at risk for loss of proximal and/or distal fixation. Patients with hyperlordosis appear to be at greatest risk for postoperative complications.
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