Adjuvant Teriparatide Therapy Targeting Osteoporotic Spine: The Significance of Long-Term Administration from the Perspective of Cortical Bone Histomorphometry

<p>Introduction: Teriparatide (TPTD) is expected to be an adjuvant therapy, targeting the patients with osteoporotic spine because of its strong bone formation promoting action from an early stage. From the viewpoint of cancellous bone histomorphometry, we reported that at least 3 months of preoperative administration is desirable to provide a more substantial anabolic effect from the early postoperative stage. Alternatively, cortical bone makes a significant biomechanical contribution to vertebral body strength in the osteoporotic spine. The aim of this study was to examine the effect of TPTD administration on cortical bone with respect to bone histomorphometry and to elucidate the significance of the administration period in patients with osteoporosis.</p><p>Methods: Thirty-nine patients with spinal fusion and osteoporosis, who consented to undergo iliac biopsy, were allocated to the following treatment groups: TPTD neoadjuvant therapy, TPTD group (n = 32) and no neoadjuvant therapy, NTC group (n = 7). Patients in the TPTD group were categorized into subgroups based on preoperative TPTD administration periods as follows: 1 month (n = 6), 2 months (n = 7), 3 months (n = 7), 4 months (n = 6), and 6 months (n = 6). All patients were double labeled with tetracycline preoperatively. Iliac biopsy was performed during spinal fusion surgery. Histomorphometric analyses were performed on nondecalcified, thinsliced specimens. Specimens were classified based on the TPTD administration period and subsequently compared with those in the NTC group.</p><p>Results: P1NP and TRACP5b were significantly increased in the TPTD group compared to the NTC group at the time of biopsy (144.7±78.3 vs. 67.42±25.6; p = 0.0017 and 586.3±292.0 vs. 368.1±147.3; p = 0.0233, respectively). There was a difference between endocortical and periosteal surfaces. In the endocortical, mineralizing surface (MS/BS) reached a peak at 3 months of the administration, with a 2.3-fold increase relative to that in the NTC group. In periosteal, MS/BS finally reached a significant level at 6 months (p = 0.0446). The value 4.4% was nearly equal to the result of 24 months administration study reported in a previous study.</p><p>Conclusions: Anabolic bone response in the endocortical was similar to cancellous bone. However, in periosteal, anabolic response became to a plateau at 6 months of the administration. In other words, 6 months or more is desirable to rebuild cortical bone. To maximize the effect of TPTD on biomechanical strength, we suggest continuing the administration for 24 months.</p>