Complications in the Treatment of Neuromuscular Spine

Introduction

The treatment of pediatric patients with neuromuscular scoliosis is challenging and requires constant vigilance. These patients are more medically complex and have higher complication rates than their idiopathic counterparts. This chapter will focus on preoperative, intraoperative, and postoperative complications, as well as strategies for the prevention and treatment of these complications. Surgical site infection (SSI) is one of the most significant concerns in this population and will be the focus of the chapter. However, other complications, including pulmonary, neurologic, and implant-related, will also be discussed.

Preoperative Considerations and Preventative Strategies

Given the medical complexity of and high complication rates in neuromuscular scoliosis, it is critical to perform a thorough preoperative evaluation and risk assessment and to optimize medical comorbidities. Certain neuromuscular conditions, such as cerebral palsy (CP) and myelodysplasia, have been associated with increased risk of SSI as well as other medical complications. A proactive approach is necessary to help minimize risk and prevent issues in the intraoperative and postoperative period.

Preoperative clinical and radiographic examination should focus on muscle tone, joint stiffness, hip range of motion, pelvic obliquity, and walking capacity in addition to the other typical scoliosis evaluations (curve magnitude, sagittal balance, curve flexibility, etc.). Additional evaluation for these neuromuscular patients should include assessment of respiratory, cardiac, nutritional, urinary, gastrointestinal, and psychosocial status, as these can contribute to the development of postoperative complications. Specifically, a history of pneumonia and the presence of gastrostomy/gastrojejunostomy tube have been described as preoperative risk factors for respiratory complications after surgery in neuromuscular patients. Nutritional status may need to be optimized prior to surgery, and patients may require feeding in advance of surgery in order to achieve these nutritional goals. Prior studies have demonstrated a decreased rate of infection, shorter period of intubation, and shorter period of hospitalization in CP patients with optimized preoperative nutritional labs (albumin ≥3.5 mg) ; however, the data are conflicting, as more recent data do not demonstrate a correlation between preoperative labs and development of SSIs. Obesity has also been found to increase risk for postoperative SSI, wound dehiscence, urinary tract infection (UTI), and readmission. Urinary and bowel incontinence have been found to be associated with increased risk of SSI. Finally, a positive urine culture has been found to be an independent risk factor for the development of SSI and may require treatment of chronic UTI prior to surgical management.

A multidisciplinary, team-based approach begins preoperatively. Engagement of the local team early on is helpful; this team includes orthopedic surgeons, neurosurgeons, anesthesiologists, infectious disease specialists, operating room (OR) and floor nurses, medical services staff, complex care services staff, and the intensive care unit team. With regard to SSI, a national best practice guideline has been developed and addresses a few things that should be done preoperatively to mitigate risk ( Table 21.1 ).

The surgeon or surgeons should create a plan ahead of time and execute the plan mindfully and safely. Managing expectations in the clinic before surgery and seeing the patient and family at the preoperative visit helps the surgeon understand the family’s expectations and the family better understand complications if they do occur. In general, the goals of surgery in this population are to preserve function, facilitate daily care, improve sitting ability, and alleviate pain.

Intraoperative Strategies to Reduce Infections and Complications

In general, intraoperative optimization revolves around a team-based, systematic approach. Use of a spine team has been linked to a significant decline in SSIs, as well as OR time, length of surgery, allogenic blood transfusion volume, and unplanned stage procedures. Mentors are also part of the team, and one should not be afraid to leverage them if needed, by asking them to review the plan ahead of time and/or calling them into the room intraoperatively. This serves as a benefit and learning experience to both the mentee and mentor. Be honest with assistants in the OR, perform the procedure safely, and do not rush. Creating a system and routine assists in creating a safe methodology and reduces uncertainty, making both the surgeon and other OR staff more comfortable. It is helpful to have patient checklists, which have been shown to lead to a lower rate of complications.

There are numerous risk factors for infection in neuromuscular scoliosis patients and steps that can be taken to minimize these risks. However, there is a limited amount of high level evidence on this topic overall. Longer operative time, particularly if greater than 6 hours, is associated with increased infection risk. Instrumentation to the pelvis, more levels fused, and longer hospital stay are associated with increased risk of infection.

Perhaps one of the most critical aspects for reducing SSI includes antibiotic considerations. Appropriate dosing and compliance of antibiotics, which needs to occur within 1 hour of incision, redosing when necessary, and stopping within 24 hours lead to decreased infections. In the setting of fecal and urinary incontinence, prophylactic administration of antibiotics with gram-negative coverage has also been advocated for. Blood loss and need for intraoperative transfusions have been associated with SSI risk. As such, antifibrinolytics are important to decrease perioperative blood loss and transfusion requirements. The recommended tranexamic acid dosing is 30 mg/kg + 10 mg/kg/h.

In terms of skin preparation, chlorhexidine-alcohol has been shown to be superior to povidone-iodine in preventing superficial and deep SSIs in gastrointestinal, gynecologic, thoracic, and urologic surgery, although the application of this to spine surgery is unclear. With regard to instrumentation, an increased bacterial burden is required to colonize titanium compared to other metals. For intraoperative irrigation, povidone-iodine is superior to saline alone.

Additionally, intrawound antibiotics have been shown to reduce infection rate in neuromuscular patients. There is some evidence based on a systematic review that intrawound vancomycin can mitigate risk, and this approach has also been shown to reduce SSIs in vitro. Vancomycin powder does not appear to cause significant changes in creatinine or systemic vancomycin level in children or to induce adverse reactions. Although proven to be effective in early-onset scoliosis and vertical expandible prosthetic titanium rib, there is less literature to support its benefit in children undergoing posterior spinal fusion. The risk of using intrawound vancomycin powder is the creation of drug-resistant organisms, particularly gram-negative and polymicrobial infections. Use of gentamicin has also been shown to decrease deep infections after posterior spinal fusion in children with CP.

Other intraoperative decisions, specifically bone grafting material and use of a postoperative drain, have less compelling evidence with regard to reduction in SSIs. The data on usefulness of allograft in reducing or increasing risk of infection are variable. Sponseller et al. demonstrated that allograft may be linked to increased risk of infection ; however, more recent studies have found a decreased rate of SSI in CP patients with gentamicin-infused allograft and no difference in SSI with ceramic bone graft substitute as compared to autograft. Additionally, there is conflicting evidence on the relationship between drain use and infection, although the majority of studies indicate that there is no difference.

During closure, it is important to take care of the soft tissues. Using plastic multilayered closure in neuromuscular patients has been shown to decrease postoperative wound complications.

Following a protocol can help reduce SSIs in these patients. A protocol consisting of multidisciplinary conference, bowel prep, preoperative methicillin-resistant Staphylococcus aureus screen and decolonization, time limits on positioning and surgery, minimization of shift and staff changes, antibiotic (gram-positive and gram-negative) adherence, and topical vancomycin and betadine has been shown to help reduce deep SSIs. As in the preoperative process, using the Best Practice Guidelines as a starting point, an institution-specific pathway can be created to standardize intraoperative techniques.

Neuromonitoring plays a crucial role in this patient population. Discussion of goals with the anesthesiologist and neurophysiologist including mean arterial pressure (MAP), blood loss, and surgical plan should be performed. Also, having a true understanding of preoperative function in this population is very important. Keep the team engaged in a nonthreatening environment with constant communication between anesthesia and the monitoring team. Encourage progress reports and news of events. For many events, there is a prelude, and acting during the prelude may avoid the actual event. Keep the room updated on maneuvers. Keep the MAP up, aiming for greater than 65 mmHg. Be prepared for when a neurologic event happens. It will happen at some point in a surgeon’s career, and having a checklist and protocol for the team ensures the appropriate response. Stay calm, take control, use the team, talk to mentors if needed, and be cognizant that the procedure may need to be stopped.

Different diseases and pathologies can influence the utility and efficacy of intraoperative neuromonitoring. For patients with seizure disorders, CP, or developmental delay, the quality of the signals depends on the cortex. Signals are degraded in those with poor or atrophic cortical tissue, previous stroke, and hydrocephalus. Seizure medications can suppress the cortex. The result is poor somatosensory-evoked potentials (SSEP) and poor or nonexistent transcranial electrical motor-evoked potentials (TcMEPs). Higher stimulation is needed for younger patients. Cranial stimulation in this cohort is generally felt to be safe, as there are only sparse reports of worsened seizures. In patients with myopathies, there are typically no issues with SSEPs, but TcMEPs can be variable. Spinal muscular atrophy patients usually do not have problems with SSEPs or TcMEPs. In muscular dystrophy, SSEPs are unaffected, but TcMEPs can be absent in advanced stages in affected muscle groups. Patients with myelodysplasia or spina bifida can have lower extremity partial paralysis, making SSEPs and TcMEPs often unobtainable. However, neuromonitoring is worthwhile even if there are no lower extremity SSEPs or TcMEPs, because there can still be upper extremity injury associated with positioning, and this acts as an indirect monitor of cortical function.

Intraoperative halo-femoral traction (HFT) can be a helpful technique that is best indicated for patients with pelvic obliquity to assist in correcting the obliquity before implants. The halo portion helps with head positioning and pressure. A threaded Kirschner wire in the femur levels the hemipelvis. Therefore, half the bodyweight is split between the halo and femur. The goal is to create a level pelvis while putting less stress on the often osteoporotic bone with implants alone. In patients with nonambulatory neuromuscular scoliosis, intraoperative HFT has been shown to significantly improve pelvic obliquity correction with no traction-related complication.

Complications will inevitably happen, but the important thing is to learn from them and know how to move on. Be aware of the impact that complications may have on life outside the hospital and on the next case. Nevertheless, do not ignore complications. Aggressively address them and be honest and share experiences so that everyone can learn and improve from them.