22 Complications in Surgery for Spinal Deformity

Many pitfalls are encountered in surgery for spinal deformity. The procedures are physiologically demanding for the patient and technically challenging for the surgeon. Not surprisingly, complications accompany this complex endeavor.

The variety of complications encountered in spine surgery and catalogued in the literature is extensive, and ranges from insignificant to severe.1–3 Pulmonary complications predominate, accounting for more than 50% of the morbidity associated with anterior approaches to the thoracic and the thoracoabdominal spine.4 Other reported complications include great-vessel injuries, retroperitoneal hematoma and fibrosis, ureteral injury, chylous-fluid leakage, and spinal-cord injury, to name but a few.5 Added to this are isolated reports of unusual complications such as splenic injuries, empyema, bronchopleural fistula, chylothorax, and chyloperitoneum.6–8 However, the incidence of major complications in surgery for spinal deformity is low, with death occurring in 0.3% of cases, paraplegia in 0.2%, and deep wound infection in 0.6%.9

Reported rates of morbidity for spine surgery in the adult population range from 18 to 86%.3,10,11 Anderson and co-workers12 have reported low rates of morbidity in their adult populations, citing nonidiopathic scoliosis, mental retardation, anterior spinal procedures, hypoxemia, and obstructive pulmonary disease as common denominators in the development of complications. In the pediatric population, morbidity from spinal procedures is reported to range from 10 to 74%.13,14

Idiopathic and acquired spinal deformity and congenital anomalies of the spine are the typical indications for spine surgery in the pediatric population. Degenerative disease of the discs, infections, trauma, degenerative deformities, and tumors are the typical indications for spinal surgery in adults.10,15–21 The difference in pathology directly affects the surgical exposures for these two groups of patients. Pediatric patients typically require longer exposures to provide access to extensive deformities, whereas exposures in adults may be more focal. Naunheim et al15 reported 4.5 vertebral segments exposed per patient and McElvein et al10 reported ~5 vertebral segments exposed per patient in a mixed population of patients who were primarily adults with a mean age of 40 years. Janik and co-workers22 reported 8.2 vertebrae exposed per patient in a primarily pediatric population. Patients with neuromuscular pathologies required slightly larger incisions, with an average exposure of 9.6 vertebral segments. In the adult population, from 21 to 26% of patients will require a thoracoabdominal approach with incision of the diaphragm.4,10,12 In the pediatric population, from 58 to 82% of patients were found to require thoracoabdominal exposure.22,23 Patients with syndromic conditions (e.g., neuromuscular disease, Ehlers-Danlos syndrome, etc.) often require longer incisions than are typical, even in the pediatric population. Series of both adult and pediatric patients typically record a higher incidence of complications for thoracic and thoracoabdominal approaches than for retroperitoneal or transperitoneal lumbar approaches.

Grossfeld and coworker’s review of 550 pediatric patients undergoing a total of 599 spinal procedures documents 45 major complications ( Table 22.1 ) for a rate of major complications of 7.5%.24 These complications included reintubation for pneumonia and respiratory distress, chylous effusion requiring chest tube drainage, paralysis, and death. Major complications were seen more often in patients older than 14 years of age (10.4%) than in those younger than 14 years (5.7%). Boys had a significantly higher complication rate of 11.7% than did girls, for whom the rate of complications was 4.7%. The combined effect of gender and age resulted in a greater complication rate of 15.5% among boys older than 14 years than among boys younger than 14 years, for whom the rate of complications was 8.1%. Girls had a complication rate of 5.3%. Major complications were more frequently seen in patients with kyphosis (16.3%) than in patients with scoliosis (4.2%). A major complication rate of 17.8% occurred in surgery for curves >100 degrees, as compared with complication rates of 6.8% and 5.2%, respectively, in surgery for moderate and small curves. Anterior-only procedures had a 9.7% major complication rate as compared with a 6.3% rate for combined anterior–posterior procedures and a rate of 7.3% for staged anterior–posterior procedures. Detachment of the diaphragm did not seem to increase the rate of major complications. However, as documented in other series, thoracotomy either alone or as part of a thoracoabdominal procedure is associated with a significantly higher rate of major complications of 8.2% versus 1.5% for anterior spinal surgery without thoracotomy. In both pediatric and adult populations, pre-existing pulmonary disease increases the complication rate. Patients with pulmonary function of <40% of predicted values had a major complication rate of 14.8%, compared with 9% for patients with pulmonary function values of ≥40% of the predicted values.

Grossfeld and colleagues24 also cited 193 minor complications in 145 surgical procedures for spinal deformity, or a rate of 32.6% ( Table 22.2 ) Ileus, atelectasis, superior mesenteric artery syndrome, and pleural effusions were considered minor complications. Minor complications were more frequent in patients older than 14 years of age (41.7%) than in younger patients (26%). Gender did not significantly affect the rate of minor complications, with males (36%) and females (30.3%) having roughly equivalent rates. When age and gender were combined, boys older than 14 years typically had a higher rate of minor complications (49.1%) than did younger boys or girls in either group (23.6% and 36.8%, respectively). The rate of minor complications did not appear to be related to the type of spinal pathology, although patients with curves >100 degrees had higher minor-complication rates (45.2%) than did patients with curves of moderate size (34.7%) or small curves (27%). Minor complications were seen more often in patients with a marginal preoperative pulmonary vital capacity (59.2%) than in patients with a vital capacity >40% of the predicted value. Minor complications were seen more often in patients with staged anterior–posterior procedures (38%) than in combined anterior–posterior procedures (22%) or anterior procedures alone (33.9%). The minor-complication rate was not affected by thoracotomy or by detachment of the diaphragm.24

Abbreviation: SIADH, syndrome of inappropriate secretion of antidiuretic hormone

The theme that older patients experience more complications than younger ones is reinforced by Faciszewski and colleagues’ study of 1152 adult patients9 in which patients over the age of 60 years had a greater risk for complications, of 1.96 than for patients younger than 40 years. In Naunheim and coworkers’ study,15 patients under 39 years of age fared statistically better with fewer complications than did patients older than 60 years. Patients with more than two comorbidities have a higher risk of complications than do those with fewer than two comorbidities.9 When cancer or osteomyelitis is the underlying pathology requiring surgery, there is a significantly greater risk of both operative morbidity (30%) and mortality (8.2%).15,21 For patients undergoing a combined anterior–posterior procedure, the odds of complications occurring increase by a factor of 1.61 over that for patients undergoing a staged, anterior, or posterior procedure. Patients undergoing thoracotomy are at greater risk for having a complication by a factor of 1.6 over that for patients undergoing surgery via a retroperitoneal approach. Unlike Grossfeld et al’s24 review of a pediatric population undergoing spine surgery, Faciszewski et al’s9 review of an adult population suggests that the risk of a complication is greater for an adult female than for an adult male by a factor of 1.3.

McDonnell et al25 reviewed 447 adolescent and adult patients undergoing anterior spinal surgery of the thoracic, thoracolumbar, and lumbar spine to determine the incidence of perioperative complications. Diagnostic groups included idiopathic, neuromuscular, and congenital scoliosis; kyphosis; fracture, trauma, or both; anterior revision surgery; tumor; vertebral osteomyelitis; and discitis. One hundred forty complications occurred in McDonnell and colleagues’ 447 patients, for a complication rate of 31%. There were 60 major complications and 120 minor complications. The most common major complication was related to pulmonary function. The most common minor complication was genitourinary. Forty-seven patients (11%) had at least one major complication. At least one minor complication was identified in 109 patients (24%). Sixteen patients (4%) had both major and minor complications. Seven patients (2%) had more than one major complication and twelve patients (3%) had more than one minor complication. Two deaths occurred in this series of patients, resulting in a 0.4% mortality rate. Both deaths were the result of major postoperative pulmonary complications. There were no intraoperative deaths. Adolescents had the lowest complication rate ( Table 22.3 ), And patients over 60 years of age had a higher risk of complications. Patients with neuromuscular scoliosis, tumor, and infection had the highest overall complication rates ( Table 22.4 ).

In contrast to the findings in most other series, McDonnell and colleagues25 report a higher complication rate for same-day combined anterior/posterior procedures than for staged procedures.23,24,26 Also contrasting with the findings in other series was the lack of a statistical difference in the complication rate among patients undergoing thoracic, thoracolumbar, and lumbar anterior approaches. When patients were compared with respect to blood loss, no statistical difference in complication rate could be attributed to the loss of <500 mL, 500 to 1000 mL, 1000 to 1500 mL, or more than 1500 mL However, if considered as a continuous variable, blood loss >520 mL was an important factor in predicting increasing complication rates. There was also a significant correlation between the amount of blood lost and the duration of surgery, but again there was no specific correlation between the duration of surgery and increasing complication rate.25

Abbreviation: AIS, adolescent idiopathic scoliosis

The most comprehensive data for prospective complications of surgery for adolescent idiopathic scoliosis (AIS) comes from the Harms Study Group (HSG) database of 1800 patients. The “gold standard” data among these are prospective data, approved by institutional review boards, for consecutive patients. These data about complications are compiled cumulatively and inclusively in Table 22.5 . The data are grouped according to complications associated with anterior and posterior spinal procedures in Tables 22.6 and 22.7 , and are subdivided into major and minor complications in anterior ( Tables 22.8 and Table 22.9 ) and posterior ( Tables 22.10 and Table 22.11 ) spinal procedures for idiopathic scoliosis. Complications of instrumentation (3.17%) and pseudarthrosis (2.1%) were the most common major complications associated with anterior spinal surgery ( Table 22.8 ). Pulmonary complications (50%) and complications associated with instrumentation (14.25%) were the most common minor complications ( Table 22.9 ). For posterior procedures, instrumentation (1.61%) and wound complications (1.24%) were the most common major complications ( Table 22.11 ). The most common minor complications associated with posterior procedures were medical (12.86%) and pulmonary (9.42%) ( Table 22.10 ).

Abbreviations: DVT, deep-vein thrombosis; LLE, left lower extremity; PE, pulmonary embolism; SCI, spinal-cord ischemia; SMA, superior mesenteric artery; SSEP, somatosensory evoked potential; tcMEP, transcortical muscle evoked potential; UTI, urinary tract infection

Abbreviations: DVT, deep-vein thrombosis; LLE, left lower extremity; PE, pulmonary embolism; SCI, spinal-cord injury; SMA, superior mesenteric artery; SSEP; somatosensory evoked potential; tcMEP, transcortical muscle evoked potential; UTI, urinary tract infection