Obese patients who undergo minimally invasive surgery (MIS) for adult spinal deformity (ASD) have less correction of their deformity, worse quality-of-life outcomes, more implant complications and infections, and an increased rate of revision surgery compared with their non-obese counterparts, although both groups benefit from surgery.
These are the key findings from a recent study—the results of which were published by Khoi Than (Duke University Medical Center, Durham, USA) et al in the Journal of Neurosurgery: Spine—which also indicated that, as such, appropriate counselling should be provided to obese patients.
The impact of obesity on clinical outcomes and radiographic correction following MIS for ASD “is poorly understood” say the researchers, who add that the aim of the study was to determine the role, if any, that obesity has on radiographic correction and health-related quality-of-life measures in MIS for ASD.
This was a retrospective review of data from a prospectively collected multicentre database. Patient inclusion criteria were as follows: age ≥18 years and coronal Cobb angle ≥20°, pelvic incidence–lumbar lordosis mismatch ≥10°, or sagittal vertical axis (SVA) >5cm. A group of patients with body mass index (BMI) <30 kg/m2 was the control cohort; BMI ≥30 kg/m2 was used to define obesity.
Obesity cohorts were categorised into BMI 30–34.99 and BMI ≥35 groups, and all patients had at least one year of follow-up. Preoperative and postoperative health-related quality-of-life measures and radiographic parameters, as well as complications, were compared via statistical analysis.
There were a total of 106 patients available for analysis (69 in the control group, 17 in the BMI 30–34.99 group, and 20 in the BMI ≥35 group). The average BMI was 25.24 kg/m2 for the control group versus 32.46 kg/m2 (p<0.001) and 39.5 kg/m2 (p<0.001) for the two obese groups.
Preoperatively, the BMI 30–34.99 group had significantly more prior spine surgery (70.6% vs. 42%, p= 0.04) and worse preoperative numeric rating scale leg scores (7.71 vs. 5.08, p=0.001). Postoperatively, the BMI 30–34.99 cohort had worse Oswestry Disability Index scores (33.86 vs. 23.55, p=0.028), greater improvement in numeric rating scale leg scores (−4.88 vs. −2.71, p=0.012), and worse SVA (51.34 vs. 26.98, p=0.042) at one year postoperatively.
Preoperatively, the BMI ≥35 cohort had significantly worse frailty (4.5 vs. 3.27, p=0.001), Oswestry Disability Index scores (52.9 vs. 44.83, p=0.017), and T1 pelvic angle (26.82 vs. 20.71, p=0.038). Postoperatively, after controlling for differences in frailty, the BMI ≥35 cohort had significantly less improvement in their Scoliosis Research Society–22 outcomes questionnaire scores (0.603 vs. 1.05, p=0.025), higher SVA (64.71 vs. 25.33, p=0.015) and T1 pelvic angle (22.76 vs. 15.48, p=0.029), and less change in maximum Cobb angle (−3.93 vs. −10.71, p=0.034) at one year.
The BMI 30–34.99 cohort had significantly more infections (11.8% vs. 0%, p=0.004), while the BMI ≥35 cohort had significantly more implant complications (30% vs. 11.8%, p=0.014) and revision surgery within 90 days (5% vs. 1.4%, p=0.034).