Effect of daily parathyroid hormone (1–34) on lumbar fusion in a rat model

Background contextDespite numerous studies evaluating the anabolic effects of intermittent administration of parathyroid hormone (PTH) on bone, there are no published studies examining its effect on spinal fusion outcomes.PurposeTo determine the effect of daily injection of human recombinant PTH(1–34) on posterolateral lumbar fusions in a rat model.Study designProspective, case-controlled, preclinical animal study.Outcome measuresManual palpation and serum osteocalcin.MethodsSingle-level, intertransverse process spinal fusions were performed with iliac crest autograft in 56 Sprague-Dawley rats. Animals received daily injections of placebo or PTH(1–34). At 6 weeks, fusion masses were assessed by manual palpation. Serum osteocalcin levels were assessed in a subset of the animals.ResultsManual palpation revealed the control group to have a fusion rate of 37% (10/27) and the PTH(1–34)-treated group to have a fusion rate of 52% (15/29). Mean serum osteocalcin levels were 59.8 and 88.6 ng/L for the control and PTH(1–34) groups, respectively.ConclusionsThere was a trend towards greater fusion rate in the PTH(1–34) group as compared with the placebo group. Further, PTH(1–34) administration was associated with a significant increase in osteocalcin levels. Certainly, further investigations are warranted, as an injectable agent capable of increasing fusion rates would be of great clinical value.