Surgical site infections after posterior spinal fusion for neuromuscular scoliosis: a thirty-year experience at a single institution.

BACKGROUND

Surgical site infection is a serious complication of posterior spinal fusion for neuromuscular scoliosis, with a reported prevalence of 6% to 24%. A single-institution experience over a thirty-year period was reviewed to determine the prevalence of surgical site infection after posterior spinal fusion for neuromuscular scoliosis, and to identify patient and treatment-related risk factors.

METHODS

Our retrospective review included all patients treated with posterior spinal fusion (alone or in combination with an anterior procedure) for neuromuscular scoliosis from 1980 to 2009 and followed for a minimum of two years. Univariate and multivariate statistical analysis was performed to identify significant risk factors for occurrence of deep surgical site infection (p < 0.05).

RESULTS

The study included 428 patients with an average duration of follow-up of 4.9 years. The mean Cobb angle was 74.3°. Most (74%) were treated with posterior spinal fusion alone. Deep infection developed in forty-four patients (10.3%); 57% of the infections occurred within three months after the surgery and 73%, within twelve months. Nearly half (45%) of the infections were polymicrobial; 59% of the organisms were gram-positive and 41% were gram-negative. Implant removal was required in 58% of the patients. Surgical site infection was more frequent from 1980 to 1989 (20.3%) than it was from 1990 to 2009 (8.4%) (odds ratio [OR] = 2.8, p = 0.01 in univariate analysis). Surgical site infection was more common in patients with spina bifida (21.5%) than in those with other diagnoses (8.3%) (OR = 3.0, p = 0.001). Other patient factors associated with surgical site infection were a body mass index (BMI) of >25 kg/m(2) (OR = 2.4, p = 0.04) and incontinence (OR = 2.4, p = 0.009). Treatment factors associated with surgical site infection were inadequate prophylactic antibiotic dosing (cefazolin ≤ 20 mg/kg) (OR = 3.3, p = 0.0002), length of fusion (p = 0.002), pelvic fixation (OR = 2.4, p = 0.04), length of hospital stay (p = 0.005), and other complications (OR = 3.2, p = 0.0003). Drain output (p = 0.04) and lower hemoglobin levels (p = 0.008) were significantly associated with surgical site infection in patients with spina bifida, and drain use (superficial to the fascia) was protective in those without spina bifida (OR = 0.5, p = 0.046).

CONCLUSIONS

This study identified modifiable factors, especially antibiotic dosing and drain use, associated with surgical site infection in patients with neuromuscular scoliosis.