Purpose of study: Evaluate our surgical site infection (SSI) rate in scoliosis surgery against nationally agreed standards, examine local practices to limit SSI and compare metalwork survivorship in the presence of infection.

Methods and Results : Retrospective analysis of patients undergoing instrumented correction of scoliosis with or without fusion between September 2003 and January 2009. Clinical and laboratory records of 134 patients (age range 10 months to 22 years) were examined for any evidence of SSI. There were 14 (10.4%) SSI cases, of which 8 (5.9%) were clinically significant deep SSIs, which is slightly higher than a pooled SSI rate of 2.2% from a meta-analysis of infection in spinal surgery (range 1.2 to 8.5%)1. Half of our deep SSIs occurred in neuromuscular scoliosis corrections with the most prevalent pathogen being E. Coli (28%) overall. All deep SSI patients underwent surgical debridement and iv antibiotics and we were able to retain the metalwork in all early (within 21 days) SSIs (6 of 8) but in neither late SSI (588 and 814 days). No single common variable was identified from our data-set as a risk factor for SSI although high staff numbers in theatre was noted. Infection rate increased toward the end of our series which coincided with a change in antibiotic prophylaxis protocol and paradoxically with a move to a laminar flow theatre.

Conclusion : Our SSI rate in scoliosis surgery was not significantly higher than previously published pooled rates. No single common variable was identified as risk factor for SSI. An empirical return to previous antibiotic prophylaxis could be recommended along with limiting staff numbers and movements within the operating theatre.

Ethics approval: Audit/service standard in trust

Conflict of Interest Statement: None

Study Design/Objectives: A pilot study to predict thoracolumbar kyphosis progression secondary to fracture in non-operatively treated patients.

Summary of Background Data: Progressive saggital plane deformity can cause persistent pain after thoracolumbar vertebral fractures. Little data exists to suggest at what interval after the index injury the patient attains a low risk of developing further angular deformity in non-operatively treated patients.

Methods: Supine and erect radiographs were assessed and the degree of fracture kyphosis was determined using an Oxford Cobbometer. The fracture kyphosis was recorded for each follow up appointment along with time after the fracture. A time/data analysis was performed using the Blyth-Still-Casella exact interval.

Results: This study included 22 patients (13 male, 9 female) with average age 67.2 years (range, 14–87 years). The average length of follow up was 11.5 months (range, 5.3–19.9 months) and the average number of radiographs taken within this period was 4 (range, 2–6). The change in fracture kyphosis was plotted against time following fracture. Based on 15 patients with data extending to 200 days follow up, it was observed that the rate of change in fracture kyphosis between two time points of 100 and 150 days predicted the trend in kyphosis progression until the end of follow up in 14 out of the 15 patients. This observed rate of 14/15 (0.93) has a 95% confidence interval of 0.7 to 0.99 (Blyth-Still-Casella exact interval).

Conclusions: The standing lateral radiograph of patients with conservatively treated thoracolumbar fractures at 3 and 4.5 months post injury can be used to predict fracture kyphosis progression. Using this protocol, patients can be safely discharged earlier from outpatient follow up reducing radiological exposure.

Objectives: Ex vivo biomechanical study to compare the properties of isolated, fractured, vertebral bodies after treatment by kyphoplasty with one of two bone tamps: a balloon bone tamp (Kyphon®) or an expandable polymer bone tamp (SKyBone®).

Methods: Simulated compression fractures were created in 21 vertebral bodies (L3–5) harvested from red deer (sp. elaphus. elaphus), with initial strength and stiffness determined concurrently. Deer spine was selected as an alternative to human cadaveric spine due to its availability and its very similar bone density and morphological profile. Vertebral bodies were assigned to one of three groups: (1) unaugmented (control); (2) kyphoplasty using a balloon bone tamp (BBT); and (3) kyphoplasty using a polymer bone tamp (PBT). The kyphoplasty treatment consisted of deploying the bone tamp biped-icularly, then filling the created voids with standardised low viscosity cement. All vertebrae were then recom-pressed to determine their augmented strength and stiffness. Data was analysed using one-way analysis of variance test and paired samples T-Test.

Result: Following fracture and subsequent kyphoplasty augmentation, the median strength of the BBT group was 6.71kN (± 2.71) vs 7.36kN (± 3.43) in the PBT group. Median stiffness in the balloon bone tamp group was 1.885 kN/mm (± 0.340) compared with 1.882 kN/ mm (± 0.868). Augmented strength tended to be greater in the PBT group than for BBT group, but this difference was not significantly different (p> .8). Significantly greater strength was obtained after kyphoplasty using BBT or PBT, compared with control group (p=.001 and .04, respectively). BBT and PBT groups were not statistically different for augmented stiffness (p=.4). Both BBT and PBT groups have greater augmented stiffness as compared to the control group (p=.007 and .005, respectively).

Conclusions: The use of a polymer bone tamp creates similar augmented vertebral body strength and stiffness as compared with the widely used balloon bone tamp in a deer spine model. Similar results would be expected in human spine and consequently the polymer bone tamp may be used as an alternative bone tamp for kyphoplasty.

We performed a biomechanical study to compare the augmentation of isolated fractured vertebral bodies using two different bone tamps. Compression fractures were created in 21 vertebral bodies harvested from red deer after determining their initial strength and stiffness, which was then assessed after standardised bipedicular vertebral augmentation using a balloon or an expandable polymer bone tamp.

The median strength and stiffness of the balloon bone tamp group was 6.71 kN (sd 2.71) and 1.885 kN/mm (sd 0.340), respectively, versus 7.36 kN (sd 3.43) and 1.882 kN/mm (sd 0.868) in the polymer bone tamp group. The strength and stiffness tended to be greater in the polymer bone tamp group than in the balloon bone tamp group, but this difference was not statistically significant (strength p > 0.8, and stiffness p = 0.4).