6 Predicting Complications: When to Operate or Not
Abstract
Spinal deformities, including scoliosis and severe sagittal deformities, are common in patients with neuromuscular conditions, yet the indications for surgical intervention can be controversial. Patients with cerebral palsy, muscle diseases, and myelomeningocele often have impairments of major organ systems including cardiac, pulmonary, genitourinary, and gastrointestinal systems. Their fragile medical condition and the high rates of reported complications in this group of patients, coupled with the paucity of data on the impact of interventions on quality of life, make decision making particularly challenging. This ethical dilemma is presented in this chapter. Also, this chapter discusses the various neuromuscular conditions commonly occurring in patients with spinal deformities. The risk assessment is coupled with information on complication rates. Some guidelines are provided to mitigate risks, and medical thresholds are provided when the risks may be too high to embark on surgery.
6.1 Introduction
The general principle of the Hippocratic Oath suggests that physicians should withhold treatments that are likely to produce harm to the patient. This dictum is highly relevant for many patients with neuromuscular spinal deformities such as kyphosis and scoliosis. This group of patients includes those with cerebral palsy (CP), muscle diseases, and myelomeningocele as well as a range of genetic syndromes. Many of these patients are totally dependent on a parent or other caregiver for all their daily needs including hygiene and feeding. Furthermore, the patients often have multiple comorbid conditions including intellectual disabilities, joint contractures, seizure disorders, oral-motor dysfunction requiring supplemental tube feedings or gastrostomies, cardiac disease (especially in the muscular dystrophy group), and pulmonary deficits of a restrictive and/or obstructive nature. Furthermore, the spinal deformities are progressive and difficult to control with nonoperative methods, yet the impact of surgical interventions on overall quality of life has only recently been investigated.
Surgical correction may involve anterior, posterior, or combined approaches with intraoperative or preoperative traction depending on the configuration and magnitude of the spinal deformity. Whichever surgical techniques are chosen, the complication rate still remains highest in this category of patient because of the previously mentioned comorbid conditions, magnitude of the deformities, and poor bone quality. The existing medical literature clearly defines the high rate and severity of complications (between 25 and 75%), 1 yet absolute contraindications to surgical correction are not well documented or defined. Thus, the relative contraindications of surgery are subjective at best. The decision to perform the surgery and the ability to correct these challenging deformities should be carefully weighed based on the patient’s medical condition (and the natural history thereof), associated comorbidities, curve characteristics, surgeon’s experience, and the resources available at the treating institution.
This chapter will review presurgical risk assessment in patients with neuromuscular conditions undergoing spinal correction surgery. The first goal of the chapter is to provide parameter thresholds to consider in determining if spinal reconstructive surgery should be done, keeping in mind that the prime goal of our intervention is to improve the patient’s quality of life, which essentially means avoiding a complication that leaves the patient in a worse condition than they were preoperatively. Table 6‑1 lists medical parameters that should make the surgeon particularly wary of surgical interventions. When these conditions are present, the patient is much more likely to have a serious complication.
The second goal of the chapter is to provide guidelines for decision making used by the authors. Our role as physicians is to educate patients and their families as best as we can with incomplete data on risks, benefits, and alternatives to empower them to share in the choice for their child. Families vary in their willingness to assume risk or to accept intensive interventions for a modicum of perceived benefit for their child. Before undertaking life-threatening surgery, the surgeon and care team must forge a collaborative partnership with the family. In pediatric neuromuscular spinal deformity, the process of informed consent is as potentially complex as the procedure itself.
6.2 Risk Assessment
6.2.1 Multidisciplinary Input
The medical complexity and variety of pediatric patients with spinal deformities secondary to neuromuscular disorders necessitates that multiple medical specialists get involved in the presurgical examination and analysis. These specialists collaborate to define the risks of the proposed spine surgery and the interventions needed to mitigate those risks. The spine surgeon should not be expected to understand and acquire all of the multisystem medical data alone. Most hospital systems, including the authors’, have standardized care pathways for preoperative, intraoperative, and postoperative management. Table 6‑2 lists some elements that are a standard part of our pathway. Chapter 1 addresses preoperative assessment more fully. Ideally, the team of specialists can assist not only in the assessment and care, but also in the counseling and decision making. For complex cases, a multidisciplinary preoperative case conference or e-mail communications can facilitate decision making.
6.2.2 Disease-Specific Risk
Cerebral Palsy
CP, the leading cause of physical disability in childhood, is a static encephalopathy occurring in the developing, immature brain producing a range of motor, cognitive, and neurological deficits. The Gross Motor Function Classification System (GMFCS) is an international classification system, with five categories, developed to differentiate patients by their ability to move. 3 Those in class 4 or 5 require assistance to move, underscoring their poor muscle function and the severity of their neuromuscular impairment. The literature related to “complication rates for spinal deformity surgery” is heavily weighted toward patients with CP because of the high prevalence of CP among neuromuscular conditions and the high incidence of spinal deformities in this group. 4 Despite the static nature of the brain lesion, these same patients in GMFCS 4 and 5 have the highest incidence of spinal deformities, approaching 50%, due to the absence of trunk balance and the presence of excessive high or low muscle tone. 5 Furthermore, the majority of these patients, particularly those in GMFCS level 5, have other significant medical disabilities including seizures, oral motor dysfunction, and reactive airway disease to name a few. 6 , 7 Not unexpectedly, given these conditions, surgical complication rates after spine surgery are 25 to 50% in patients with CP compared to rates of 1 to 3% in idiopathic scoliosis. 8 Also the more severe and complex curves in these patients (Cobb > 90 degrees) require a longer total operative time and result in an increased total blood loss, all resulting in a propensity for major complications. 8 Furthermore, the complications encountered in some of these patients can be potentially life-threatening. 9 The rate of mortality ranges from 1 to 4% in some recent series. 9 , 10 , 11 , 12 Where patient/parent satisfaction with treatment has been assessed, the occurrence of a complication requiring prolonged hospital stay, reoperation, or death results in dissatisfaction with the intervention. 13
When taken on whole, surgical intervention for patients with spinal deformity does lead to improved scores on the CPCHILD (Caregiver Priorities and Child Health Index of Life with Disabilities) questionnaire, a validated HRQL (Health-Related Quality of Life) instrument. 14 The major area of improvement was in the “Transfer & Basic Mobility” domain, and on average no domain saw deterioration. 14 , 15 Unfortunately, despite the positive change reported from surgery, the lack of randomization casts some doubt on the relevance of these outcomes. 16
Muscle Diseases
Of patients with muscle disease, those with Duchenne’s muscular dystrophy (DMD) account for the largest prevalence; thus, we have the most information on spinal deformity surgery in this group. DMD is a progressive muscle disease caused by an X-linked recessive gene, altering a structural protein, dystrophin, critical for muscle function. The disease progression involves cardiac and pulmonary function with cardiomyopathy and, most commonly, respiratory failure as the main causes of death. Spinal deformities occur in virtually all patients with DMD after their disease progresses to the point they are no longer ambulatory. 17 The popular use of steroids has markedly altered the natural history of spinal deformity in DMD in that spinal deformities are occurring at a later age and with less severity. 17 , 18 , 19 However, reduced life expectancy and progressive cardiopulmonary decline are still inevitable, even if spinal surgery is performed. 20 However, the purported benefits from spinal surgery include improved sitting tolerance, 21 ease of nursing requirement, and less pain. The effect of spinal stabilization on pulmonary function, motor function, and survival is controversial, in large part because there are no clinical trials or randomized studies on this question. The Cochrane review published by Cheuk et al 22 reported the controversial results. Some studies report deterioration of pulmonary function and no improvement in life expectancy, 17 , 18 while others found improved outcomes compared with those not treated with spinal surgery. 23 Furthermore, the trunk lengthening and mobility loss following spinal fusion can impede upper extremity function. 23
A recent prospective, observational report by Suk et al 24 compared 32 patients selecting nonsurgical treatment to 45 surgically treated patients with DMD using functional tests (modified Rancho scale and manual muscle test), a validated HRQL questionnaire (the Muscular Dystrophy Spine Questionnaire) and pulmonary function tests (PFTs). The authors found that surgical patients, as expected, had better radiographic alignment and significantly higher scores on the MDSQ, which was only given at final follow-up. There was no difference in strength or pulmonary function, but the rate of decline in PFTs was less in the surgically treated group. Based on these outcomes, the authors concluded that surgical intervention was beneficial.
In addition to these uncertain outcomes from spinal surgery, we know that complications from surgery can occur in up to 44% (20–68%) of cases, 25 , 26 and include cardiac arrest, massive bleeding, spinal cord injury, pneumonia, wound dehiscence, infections, severe ileus, pseudarthrosis, pain, and difficulty with hand-to-mouth functions, 22 and these complications generally increase with curve severity.
Thus, the general treatment philosophy for patients with flaccid muscular dystrophies has not changed drastically since the publication of the classic report by Kurz et al, 27 suggesting that surgery should be done early, before a decline in forced vital capacity (FVC) of less than 40% (Table 6‑1). A clear change from that era is the use of glucocorticoids in DMD, which has resulted in longer survival and a slower rate of spine deformity progression. 17 Consequently, in the present era, spine surgery in DMD is deferred until scoliosis is greater than 40 degrees, 18 , 28 though agreement on a threshold Cobb angle has not been reached. Also, advancements in ICU (intensive care unit) care including the use of bilevel positive airway pressure (BiPap) and aggressive pulmonary therapies and mobilization have made survival from surgery more likely even if the FVC is less than 40%; clearly the risks are much higher as pulmonary function declines. Thus, multiple factors need to be considered with families as one discusses the question of surgical or nonsurgical treatment.
The authors begin the assessment by inquiring about the occurrence of back pain and looking at the sitting balance. The past history of pulmonary illness and hospitalizations is considered along with the serial PFTs. Then the sitting sagittal and coronal radiographs are considered. The presence of scoliosis with pelvic obliquity seems to be most associated with back and buttock pain and poor sitting posture. Patients with these characteristics tend to benefit most from spinal surgery.
Myelomeningocele
Myelomeningocele, a complex congenital spinal anomaly, results from a neural tube defect during the first 4 weeks of gestation. Spinal deformity (kyphosis and scoliosis) in patients with myelomeningocele is common with greater than 80% eventually developing significant spinal deformity. 29 , 30 However, many patients with myelomeningocele and spinal deformity do have functional capacities for performing activities of daily living, such as eating and dressing, and they often can independently transfer or propel themselves in a wheelchair. These functional capabilities set this group apart from those children with DMD or CP in whom functional capacity is severely restricted. Thus, functional decline as a result of spinal fusion is a relevant consideration in patients with myelomeningocele. The aims of spinal deformity surgery in patients with myelomeningocele are to stop progression (as many times the deformity occurs at a young age) and to improve sitting alignment. 31 Often the pelvic obliquity or gibbus deformity can lead to areas of pressure concentration and ulceration so that a secondary goal may be to alleviate these skin problems.
The dilemma created with the surgical approach is the high complication rate, which is related to the ubiquitous association with other medical impairments. Comorbid conditions in patients with myelomeningocele include intellectual impairments (although many have normal IQ), hydrocephalus requiring shunting, and tethering of the spinal cord or progressive Chiari malformations. Insensate skin, latex allergy, renal anomalies, bacterial colonization of the urinary tract, bowel and bladder incontinence, and lower extremity malalignment are other factors that often require evaluation and impact spinal surgery decisions. 29 These patients may also display a reduced FVC with the average cited at 59% of predicted, and the impaired pulmonary function may be independent of severity of scoliosis. 32
Singh et al 33 analyzed the anesthetic concerns and perioperative complications in patients with myelomeningocele. This retrospective review of 135 cases shows a high incidence of intraoperative cardiac and respiratory problems in 15.6 and 11.1% of cases, respectively, including two cases (1.5%) of cardiac arrest. They also reported a high incidence of other anomalies to be considered including hydrocephalus (67.4% of cases), Chiari II malformation (58.4% of cases), and renal anomalies (9% of cases). This study highlights the importance of a thorough preoperative evaluation and treatment of associated Chiari malformation and/or hydrocephalus prior to spinal surgery to avoid major surgical complications. Mortality in these patients is often related to acute elevation of the intracranial pressure with hydrocephalus, or shunt insufficiency with herniation. 31 , 34 The importance of confirming the patency of shunt prior to deformity correction cannot be overemphasized. 31 , 33 Another study 35 analyzed the risk factors for sudden death in these patients. Six patients, all of whom were young women, had experienced sudden death in this series. In multivariate analysis of 106 patients, this study reported female sex, sleep apnea, and midbrain elongation 15 mm or greater on magnetic resonance (MR) imaging to be of significantly higher risk of sudden death. 35 Careful attention should be paid to the evaluation and treatment of associated anomalies, especially hydrocephalus and shunt status as well as sleep apnea.
Poor skin coverage, high frequency of bacteremias, and absence of protective sensation collectively lead to high surgical rate of complications, such as pseudarthrosis, implant failure, and infection. 35 Instrumentation problems, such as broken rods or displacement of anchors, were seen in 29% of all patients. Furthermore, the poor skin coverage over the original myelomeningocele, coupled with a lack of protective sensation, leads frequently to wound breakdown and implant infections. Management of infection, especially for the commonly associated gram negative organism, is fraught with difficulty and can lead to renal damage in patients who have compromised renal function. Nevertheless, positive urine culture and poor nutritional status are known to be strongly correlated with high risk of surgical site infection, and their correction before surgery is highly recommended. 36
Thus, the surgical correction of deformities in patients with myelomeningocele is a high-risk undertaking, and outcomes of studies with quality-of-life metrics suggest that improvement is difficult to achieve. Wai et al developed a valid and reliable questionnaire to evaluate the impact of spinal deformity on patients with meningomyelocele. 37 , 38 Studies have found little association between the presence of spinal deformity and functional capacity. 23 , 38 , 39 Of greater concern was the finding of Schoenmakers et al 40 showing that function can be lost following spinal surgery including the ability to perform transfers or to perform catheterizations. These adverse outcomes have called into question the advisability of performing surgery on patients with myelomeningocele unless sitting or skin problems are particularly recalcitrant to management through nonsurgical means such as adjusting the seating system.
The authors tend to avoid surgery except in cases where a gibbus deformity can be managed with a vertebral column resection and relatively short fusion. The gibbus deformity is frequently associated with repeated skin breakdown, severe hip flexion contractures, and obstruction of diaphragm excursion. For patients having a balanced scoliosis, surgery is not recommended.
Related posts:
1 Preoperative Evaluation and Optimization
2 Nonoperative Management
3 Surgical Indications in Neuromuscular Scoliosis
4 Intraoperative Issues: Anesthesia, Neuromonitoring, Estimated Blood Loss
5 Unique Challenges with Scoliosis and Dislocated Hips
17 Comparison of Unit Rods with Modular Constructs in Cerebral Palsy
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