Does obesity affect outcomes after decompressive surgery for lumbar spinal stenosis? A multicenter observational registry-based study

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1 Does obesity affect outcomes after decompressive surgery for lumbar spinal stenosis? A multicenter observational registry-based study Charalampis Giannadakis, Ulf S. Nerland, Ole Solheim, Asgeir S. Jakola, Michel Gulati, Clemens Weber, Øystein P. Nygaard, Tore K. Solberg, Sasha Gulati

2 Objective To evaluate the association between obesity and outcomes at one year after laminectomy or microdecompression for lumbar spinal stenosis (LSS).

3 Methods The primary outcome measure was the Oswestry disability index (ODI). Obesity was defined as bodymass index (BMI) 30. Prospective data were retrieved from the Norwegian Registry for Spine Surgery (NORspine).

4 Results The improvement in ODI was 17.5 points in nonobese and 14.3 points in obese patients (p=0.007). Obese patients were less likely to achieve a minimal clinically important difference in ODI (defined as 8 points improvement) than non-obese patients (62.2 vs 70.3%, p=0.013). Obesity was identified as a negative predictor for ODI improvement in a multiple regression analysis (p<0.001). There was no difference in complication rates (10.4% vs 10.8%, p=0.84).

5 Conclusions Both non-obese and obese patients report considerable clinical improvement one year after surgery for LSS, but improvement was less in obese patients. Obese patients were less likely to achieve a minimal clinically important difference. Read more: Giannadakis C, Nerland US, Solheim O, Jakola AS, Gulati M, Weber C, Nygaard OP, Solberg TK, Gulati S: Does Obesity Affect Outcomes After Decompressive Surgery for Lumbar Spinal Stenosis? A Multicenter, Observational, Registry-Based Study. World Neurosurg, Published online: June 19, 2015

6 Figure and Tables Figure 1. Study enrollment and follow-up 2745 Patients were screened 1272 were ineligible: 879 had other surgical procedures 258 without information about BMI 135 with other reasons 1473 were eligible (100%) 1120 non-obese (76.0%) 353 obese (24.0%) 1191 with complete 12 month follow-up with ODI (80.9%) 908 non-obese 283 obese

7 Table 1. Demographic characteristics, coexisting illnesses, and measures of health status for both groups (n=1473) Variable Non-obese (BMI<30) Obese (BMI 30) P-value Mean age yr Body-mass index <0.001 Attended college no. (%) 325 (29.0) 65 (18.4) <0.001 Daily tobacco smoking no. (%) 291 (26.4) 70 (20.0) Diabetes mellitus no. (%) 64 (5.7) 44 (12.5) <0.001 Deformity (spondylolisthesis and/or scoliosis) no. (%) 131 (11.7) 31 (8.8) ASA grade >2 224 (20.0) 94 (26.6) Preoperative ODI The bodymass index is the weight in kilograms divided by the square of the height in meters. *American Society of Anesthesiologists (ASA) grade. Grade I-V. Grade V is worst indicating lifethreating condition **Oswestry Disability Index (ODI) ranges from 0-100, lower scores indicating less severe symptoms

8 Table 2. Primary and secondary patient reported outcomes at one year Variable Non-Obese (n=1120) Obese(n=353) Difference (95% CI) P-value ODI change ( ) Back pain NRS change ( ) Leg pain NRS change ( ) 0.001

9 Table 3. Surgical treatments, complications, and events Variable Non-Obese Obese Difference (95% P- (n=1120) (n=353) CI) value Surgical procedure -Microdecompression no. (%) 756 (67.5) 209 (59.2) -Laminectomy no. (%) 364 (32.5) 144 (40.8) Operation time (minutes) Single-level microdecompression (-17.0, -3.8) Two-level microdecompression (-19.4, 3.1) Single-level laminectomy (-18.8, 4.5) Two-level laminectomy (-23.9, -1.6) Days in hospital no. - Single-level microdecompression (-0.3, 0.5) Two-level microdecompression (-0.8, 0.9) Single-level laminectomy (-1.3, 0.2) Two-level laminectomy (-0.5, 1.0) Any complication no. (%) 117 (10.4) 38 (10.8) Perioperative complications no. (%) 39 (3.5) 19 (5.4) Dural tear or spinal fluid leak 32 (2.9) 16 (4.5) Nerve injury 1 (0.1) 2 (0.6) Blood replacement or postoperative hematoma 4 (0.4) 1 (0.3) 1.00 Complications within 3 months no. (%) 82 (7.3) 23 (6.5) Wound infection 30 (2.7) 10 (2.8) Urinary tract infection 49 (4.4) 10 (2.8) 0.217

10 Table 4. Multiple regression analysis with difference in ODI at one year as the dependent variable Variable Parameter 95% P-value estimate Confidence Interval Smoker , 2.2 < Oswestry score 21-40, pre-surgery , 14.7 < Oswestry score 41-60, pre-surgery , 22.7 < Oswestry score > 61, pre-surgery , 37.0 <0.001 Deformity , *Body Mass Index kg/m , *Body Mass Index >= 35 kg/m , 5.4 <0.001 Microdecompression , A negative score means a worsening of ODI score 12 months after surgery. + Reference: Oswestry score < 21, pre-surgery. *Reference: Body Mass Index < 25 kg/m 2.

11 Disclosure information The Norwegian Registry for Spine Surgery (NORspine) receives funding from the University of Northern Norway and Norwegian health authorities. This study received a grant (Grant for Quality Improvement and Patient Safety) from the Norwegian Medical Association ( The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript. We report no conflicts of interest.