Using the United States Nationwide Inpatient Sample, we identified national trends in revision spinal fusion along with a comprehensive comparison of comorbidities, inpatient complications and surgical factors of revision spinal fusion compared to primary spinal fusion.

In 2009, there were 410 158 primary spinal fusion discharges and 22 128 revision spinal fusion discharges. Between 2002 and 2009, primary fusion increased at a higher rate compared with revision fusion (56.4% vs 51.0%; p < 0.001). In 2009, the mean length of stay and hospital charges were higher for revision fusion discharges than for primary fusion discharges (4.2 days vs 3.8 days, p < 0.001; USD $91 909 vs. $87 161, p < 0.001). In 2009, recombinant human bone morphogenetic protein (BMP) was used more in revision fusion than in primary fusion (39.6% vs 27.6%, p < 0.001), whereas interbody devices were used less in revision fusion (41.8% vs 56.6%, p < 0.001).

In the multivariable logistic regression model for all spinal fusions, depression (odds ratio (OR) 1.53, p < 0.001), psychotic disorders (OR 1.49, p < 0.001), deficiency anaemias (OR 1.35, p < 0.001) and smoking (OR 1.10, p = 0.006) had a greater chance of occurrence in revision spinal fusion discharges than in primary fusion discharges, adjusting for other variables. In terms of complications, after adjusting for all significant comorbidities, this study found that dural tears (OR 1.41; p < 0.001) and surgical site infections (OR 3.40; p < 0.001) had a greater chance of occurrence in revision spinal fusion discharges than in primary fusion discharges (p < 0.001). A p-value < 0.01 was considered significant in all final analyses.

Cite this article: Bone Joint J 2014;96-B:807–16.

Mesenchymal stem-cell based therapies have been proposed as novel treatments for intervertebral disc degeneration, a prevalent and disabling condition associated with back pain. The development of these treatment strategies, however, has been hindered by the incomplete understanding of the human nucleus pulposus phenotype and by an inaccurate interpretation and translation of animal to human research. This review summarises recent work characterising the nucleus pulposus phenotype in different animal models and in humans and integrates their findings with the anatomical and physiological differences between these species. Understanding this phenotype is paramount to guarantee that implanted cells restore the native functions of the intervertebral disc.

Cite this article: Bone Joint Res 2013;2:169–78.