Commentary on: Ohtori, Seiji.,Inoue, Gen.,Orita, Sumihisa.,Yamauchi, Kazuyo.,Eguchi, Yawara.,Ochiai, Nobuyasu., et al: Teriparatide accelerates lumbar posterolateral fusion in women with postmenopausal osteoporosis: prospective study.. Spine 37(23): E1464 - E1468, 2012

BNI Neurosurgery, MD1

1Department of Neurosurgery, Barrow Neurological Institute

Keywords: fusion, spine surgery, hormone receptor, lumbar spine, spinal fusion

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     This is a randomized double-blinded prospective clinical trial evaluating the efficacy of teriparatide injections in aiding bone fusion after single or two level posterolateral fusion in woman with ostereoporosis.
     This is a randomized double-blinded prospective clinical trial comparing daily injections with teriparatide versus bisphosphanates in a group of women with established diagnoses of osteoporosis. All women underwent single or two level posterolateral fusion with local harvested bone graft. Evidence of fusion was evaluated at 3, 6, 9, and 12 months after surgery with xrays as well as CTs at 6 and 12 months. 
     Patients were women diagnosed with lumbar spondylolisthesis as well as post-menopausal osteoporosis. Patients were excluded if they had prior surgeries, as well as evidence of infection and vertebral fractures. 
     Overall patient demographics, characteristics, and levels fused between those who were treated with teriparatide and bisphosphanate was similar. The most striking outcome was that patients treated with teriparatide showed a statistically significant larger proportion of bilateral fusion masses. However, there was no statistically significant difference between unilaterally fused masses.
     The authors chose to utilize risedronate as a control instead of no pharmacologic treatment in order to simulate “real life” environments where many women with osteroporosis are on bisphosphonate therapy. Previous basic science work citated by the authors show that bisphosphonates may actually increased fusion rates in mice, suggested that any results seen in this study might be magnified if they authors had utilized a control group not on any other pharmacologic therapy. 
     There is a significant critique of their statistical method in Table 2. When comparing the number of fused constructs, the authors chose to use the chi-squared test twice to compare patients with bilateral fusion masses and unilateral fusion masses. However, since all patients were part of a common population (teriparatide treated), the authors should have utilized a rank-sum test with a two way comparison to compare overall whether patients with teriparatid or risedronate showed higher levels of fusion. Or they should have just performed a single t-test comparing total number of segments fused regardless of it being bilateral or unilateral to draw an overall effect.
     It would be useful for the authors to give information on the common side effects of teriparatide versus risedronate as well as the costs of either for additional cost-benefit analysis. 


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B. Neurosurgery ()