Teriparatide increases the insertional torque of pedicle screws during fusion surgery in patients with postmenopausal osteoporosis

Clinical article

Full access

Object

The object of this study was to examine the efficacy of preoperative teriparatide treatment for increasing the insertional torque of pedicle screws during fusion surgery in postmenopausal women with osteoporosis.

Methods

Fusion surgery for the thoracic and/or lumbar spine was performed in 29 postmenopausal women with osteoporosis aged 65–82 years (mean 72.2 years). The patients were divided into 2 groups based on whether they were treated with teriparatide (n = 13) or not (n = 16) before the surgery. In the teriparatide-treated group, patients received preoperative teriparatide therapy as either a daily (20 μg/day, n = 7) or a weekly (56.5 μg/week, n = 6) injection for a mean of 61.4 days and a minimum of 31 days. During surgery, the insertional torque was measured in 212 screws inserted from T-7 to L-5 and compared between the 2 groups. The correlation between the insertional torque and the duration of preoperative teriparatide treatment was also investigated.

Results

The mean insertional torque value in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01). There was no significant difference between the daily and the weekly teriparatide groups with respect to mean insertional torque value (1.34 ± 0.50 Nm and 1.18 ± 0.43 Nm, respectively, p = 0.07). There was negligible correlation between insertional torque and duration of preoperative teriparatide treatment (r2 = 0.05, p < 0.01).

Conclusions

Teriparatide injections beginning at least 1 month prior to surgery were effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide treatment might be an option for maximizing the purchase of the pedicle screws to the bone at the time of fusion surgery.

Abbreviations used in this paper:BMD = bone mineral density; PINP = procollagen Type I N-propeptide; PTH = parathyroid hormone.

Object

The object of this study was to examine the efficacy of preoperative teriparatide treatment for increasing the insertional torque of pedicle screws during fusion surgery in postmenopausal women with osteoporosis.

Methods

Fusion surgery for the thoracic and/or lumbar spine was performed in 29 postmenopausal women with osteoporosis aged 65–82 years (mean 72.2 years). The patients were divided into 2 groups based on whether they were treated with teriparatide (n = 13) or not (n = 16) before the surgery. In the teriparatide-treated group, patients received preoperative teriparatide therapy as either a daily (20 μg/day, n = 7) or a weekly (56.5 μg/week, n = 6) injection for a mean of 61.4 days and a minimum of 31 days. During surgery, the insertional torque was measured in 212 screws inserted from T-7 to L-5 and compared between the 2 groups. The correlation between the insertional torque and the duration of preoperative teriparatide treatment was also investigated.

Results

The mean insertional torque value in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01). There was no significant difference between the daily and the weekly teriparatide groups with respect to mean insertional torque value (1.34 ± 0.50 Nm and 1.18 ± 0.43 Nm, respectively, p = 0.07). There was negligible correlation between insertional torque and duration of preoperative teriparatide treatment (r2 = 0.05, p < 0.01).

Conclusions

Teriparatide injections beginning at least 1 month prior to surgery were effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide treatment might be an option for maximizing the purchase of the pedicle screws to the bone at the time of fusion surgery.

Use of pedicle screws has become common in spinal surgery. Despite their clinical usefulness, they are associated with mechanical problems, such as implant breakage, screw loosening, and other related failures, sometimes requiring revision surgery. Loosening of pedicle screws is a common complication that can lead to pseudarthrosis, and it represents a major patient safety concern. The frequency of screw loosening reported in the literature varies from 0.6% to 27%.7,33,39,47 To decrease the frequency of screw loosening, several different concepts have been tried, including altering screw design.5,21,23,41 Screw augmentation, using bone cement or allograft, is reported to have biomechanical advantages.1,3,27,42,43 Still, fixation in the osteoporotic spine remains a difficult challenge, with a risk of failure by loosening or pullout of the pedicle screw. Osteoporosis is a very important risk factor because bone mineral density (BMD) is reported to be highly correlated with the stability of the pedicle screw.22,36 In the treatment of osteoporosis, bisphosphonates are the first-line medications for inhibiting osteoclast-mediated bone resorption, but recently intermittent administration of parathyroid hormone (PTH) has provided a new approach for the treatment of osteoporosis. Intermittently administered PTH is recognized to have potent anabolic effects on bone remodeling, and recombinant human PTH-(1–34) (teriparatide) has already been approved as a treatment for severe osteoporosis in the United States, Europe, and Japan.6,8,31,32

Treatment using teriparatide is associated with a significant increase of bone mass in the lumbar spine.14,26,28,44 We previously reported that teriparatide administered daily for 2 months before surgery reduced the incidence of pedicle screw loosening after instrumented lumbar fusion in postmenopausal women with osteoporosis, suggesting that teriparatide increased not only bone mass, but also the quality of the pedicle cortex.34 However, a clinical study of the effect of teriparatide on pedicle screw insertional torque in postmenopausal women with osteoporosis has not yet been reported. The purpose of the current prospective study was to examine the efficacy of preoperative teriparatide for affecting insertional torque of pedicle screws investigated during fusion surgery in postmenopausal women with osteoporosis.

Methods

Patients

The protocols for human procedures used in this study were approved by the ethics committee of Kitasato University. Twenty-nine postmenopausal women with osteoporosis (mean age [SD] 72.2 ± 4.7 years, range 65–82 years) underwent lumbar and/or thoracic fusion surgery at Kitasato University East Hospital between January 2012 and August 2013. Informed consent for participation in this study was obtained from each of the participants. Osteoporosis was diagnosed in all of the women based on Japanese criteria and preoperative BMD, which was examined in the lumbar spine, femoral neck, or calcaneus by dual-energy x-ray absorptiometry (DEXA).10,37,46 Patients who had previously undergone spinal surgery or were diagnosed with bone metastases or infections were excluded. Patients who used products for osteogenesis, osteoinduction, or osteoconduction, except for teriparatide were also excluded.

A summary of the patients' clinical and demographic characteristics is shown in Table 1. All patients underwent fusion surgery with pedicle screws using the CD Horizon Solera Spinal System (Medtronic).

TABLE 1:

Comparison of clinical and demographic characteristics of the patients*

CharacteristicGroup
Control (n = 16)Teriparatide (n = 13)
age in yrs (mean)71 ± 4.772 ± 5.4
baseline BMD in g/cm2 (mean)0.59 ± 0.060.55 ± 0.10
intact PINP in ng/ml (mean)48 ± 26.767 ± 43.4
TRACP5b in U/ml (mean)565 ± 261.7664 ± 349.4
no. of fusion levels (mean)2.3 ± 1.74.2 ± 2.0
diagnosis
 lumbar spinal stenosis85
 fracture64
 deformity24
surgical method
 PLIF/TLIF85
 vertebroplasty44
 posterior fusion42
 PSO2
duration of teriparatide Tx in days (mean)61 ± 26.3

Values represent number of cases unless otherwise indicated. Means are given with SDs. PLIF = posterior lumbar interbody fusion; PSO = pedicle subtraction osteotomy; TLIF = transforaminal lumbar interbody fusion; Tx = treatment.

The number of fused levels was significantly greater in the teriparatide group compared with controls (p = 0.01). There were no significant differences in the other factors.

Teriparatide Treatment and Marker Assessment

The 29 patients were divided into 2 groups based on a physician's prescription: 16 patients were allocated to a control group without medication for osteoporosis and the remaining 13 patients were allocated to a teriparatide treatment group. Patients in the teriparatide group were treated with a daily subcutaneous injection of 20 μg (n = 7, Eli Lilly) or a weekly subcutaneous injection of 56.5 μg (n = 6, Asahi Kasei Pharma Corporation). These 2 dosing regimens have received Ministry of Health, Labour and Welfare approval for severe osteoporosis in Japan. Patients decided which type of teriparatide to use after informed consent about usage rules, effectiveness based on evidence, complications, and cost. Patients who refused or were determined by a physician not to be appropriate candidates for treatment with teriparatide were allocated to the control group. Levels of intact procollagen Type I N-propeptide (PINP), which is regarded as a bone formation marker and is synthesized by osteoblasts, were measured before surgery in the control group and before the initiation of teriparatide treatment in the teriparatide group.40 Also, TRACP5b, which is regarded as a bone resorption marker and is secreted by osteoclasts into the circulation during bone resorption, was measured at the same time.15 Teriparatide was administered for at least 1 month before the surgery. We did not use other medications for osteoporosis before the surgery in any of the patients.

Insertional Torque Measurement

Insertional torque was measured using a calibrated torque wrench with a specially designed connector (Medtronic; Fig. 1). The insertional torque measurement was obtained when the screw shank was completely anchored into the entrance point in a total of 217 screws—90 screws in the control group and 127 screws in the teriparatide group—inserted from T-7 to L-5. Pedicle screws inserted at the S-1 level were excluded from the study because S-1 screws were inserted in tricortical purchase, which is a different insertional method from that used for the other levels. A total of 5 screws were excluded, 1 at T-11 and 2 at L-4 in the control group and 1 at L-3 and 1 at L-4 in the teriparatide group. These were excluded because the precise measurement of violation degree, which was assessed postoperatively by CT using Fu's grading system, was Grade III, which means the screw extended more than 2 mm beyond the cortex.9 The mean insertional torque was compared between the 2 groups using measurements obtained for a total of 212 screws. Also, insertional torque was compared among screws of different diameter and length in similar size. For this comparison, we divided the screws into 2 groups based on length (25–35 mm and 40–45 mm) and into 3 groups based on major diameter (3.5–4.0 mm, 4.5–5.5 mm, and 6.5–7.5 mm).

Fig. 1.
Fig. 1.

Insertional torque was measured using a calibrated torque wrench with a specially designed connector (Medtronic).

The correlation between insertional torque and duration of preoperative teriparatide treatment was investigated. This correlation was also investigated in the 2 subgroups: patients treated with once-daily teriparatide and those treated with once-weekly teriparatide.

Statistical Analysis

Statistical analysis was performed using JMP Pro version 9 (SAS Institute Inc.). The data are presented as the mean ± SD. The differences between the groups and the subgroups were calculated using analysis of variance and the chi-square test. The level of significance was set at p = 0.05.

Results

There were no significant differences between the control and teriparatide groups in the patients' ages at surgery or diagnosis, or in the surgical methods used (Table 1). There were no significant between-group differences in preoperative BMD and baseline levels of intact PINP and TRACP5b, indicating no difference in remodeling between the groups prior to teriparatide treatment. The mean number of fused levels was significantly greater in the teriparatide group (4.2 ± 2.0) compared with controls (2.3 ± 1.7), but the distribution of pedicle screws at each level did not differ significantly between the 2 groups (p = 0.94; Table 2). The mean duration of teriparatide treatment was 61 ± 26.3 days in the teriparatide group. The number of fused levels was not significantly different between the subgroups treated with daily and weekly teriparatide injections.

TABLE 2:

Distribution of pedicle screw insertion levels*

LevelControlTeriparatideTotal
T-7246
T-8246
T-9246
T-10448
T-1151015
T-1261218
L-1121426
L-281826
L-3141933
L-4181937
L-5141731
total87125212

Values represent numbers of pedicle screws. The distribution of pedicle screws at each level did not differ significantly between the 2 groups (p = 0.94).

The mean insertional torque in the teriparatide group (1.28 ± 0.42 Nm) was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01; Fig. 2). There was no significant difference in insertional torque between the daily (1.34 ± 0.50 Nm) and weekly (1.18 ± 0.43 Nm) teriparatide subgroups (p = 0.07).

Fig. 2.
Fig. 2.

The insertional torque in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group, which was 1.08 ± 0.52 Nm (p < 0.01). The data are presented as the mean ± SD. *p < 0.01.

Figure 3 upper shows the insertional torque values for screws stratified by length (25–35 vs 40–45 mm). In the teriparatide group, the mean torque value for the longer screws was significantly greater than that for the shorter screws (1.44 ± 0.56 vs 1.14 ± 0.38 Nm, respectively, p < 0.01). In the control group, there was no significant difference in torque between the 2 screw length categories. Insertional torque was significantly greater for both screw length categories in the teriparatide group compared with controls (p = 0.03 and p < 0.01, respectively). The insertional torque was also compared among screws of 3 different major diameter categories (Fig. 3 lower). In both patient groups, screws with a larger diameter showed greater insertional torque, but this effect was only statistically significant in the teriparatide group. For each diameter category, insertional torque was greater in the teriparatide group, but a significant difference was noted only for the largest diameter category, which was 6.5–7.5 mm (1.14 ± 0.63 Nm in the control group vs 1.49 ± 0.56 Nm in the teriparatide group, p < 0.01). Insertional torque and duration of preoperative teriparatide treatment showed negligible correlation (r2 = 0.05, p < 0.01; Fig. 4). Also, subgroup analysis showed negligible correlation between these two variables for both the daily and weekly treatment subgroups (r2 = 0.08, p < 0.01, and r2 = 0.03, p < 0.01, respectively).

Fig. 3.
Fig. 3.

Upper: Insertional torque of screws stratified by length. In the teriparatide group, the insertional torque of the longer screws was significantly greater than the torque of the shorter screws (1.44 ± 0.56 Nm vs 1.14 ± 0.38 Nm, *p < 0.01). In the control group, there was no significant difference between the 2 length categories. Insertional torque was significantly greater in the teriparatide group than the control group for both screw lengths (*p < 0.05 and **p < 0.01). Lower: Insertional torque was compared for screws in 3 different diameter categories (3.5–4.0 mm, 4.5–5.5 mm, and 6.5–7.5 mm). In both control and teriparatide groups, screws with a larger diameter had greater insertional torque. The between-group difference was statistically significant for the largest diameter category (1.14 ± 0.63 Nm vs 1.49 ± 0.56 Nm, *p < 0.01).

Fig. 4.
Fig. 4.

Scatter plots for insertional torque versus the duration of preoperative teriparatide treatment. Gray circles indicate once-daily teriparatide; white circles indicate once-weekly teriparatide. There was negligible correlation (r2 = 0.05, p < 0.01).

Discussion

In this study, postmenopausal women with osteoporosis underwent instrumented fusion surgery with or without receiving at least 1 month of preoperative teriparatide treatment. Daily or weekly subcutaneous injection of teriparatide significantly increased pedicle screw insertional torque during surgery compared with the values in patients who did not receive preoperative teriparatide therapy (controls). Our study provides the first insight into the possible effects of teriparatide treatment on the insertional torque of pedicle screws in patients with postmenopausal osteoporosis. Previous papers reported that the biomechanical pullout strength of pedicle screw fixation was in direct proportion to the torque at the time of screw insertion.4,35,50 Previous papers have also shown that insertional torque is significantly lower in patients with osteoporosis than in those without osteoporosis, with a negative relationship reported between insertional torque and the grade of osteoporosis.38

In Fig. 3, we compared insertional torque for screws of different lengths and different diameters. In previous reports, biomechanical strength of pedicle screws evaluated by pullout testing was closely linked with the screw's diameter and length.24,45 Based on these results, we compared insertional torque in 2 screw length categories and 3 diameter categories individually. Insertional torque did not differ significantly between the 2 length categories in the control group, but longer screws showed significantly greater insertional torque in the teriparatide group. Also, insertional torque was significantly greater in the teriparatide group than in controls for both screw length categories. These results indicate that teriparatide affects insertional torque regardless of screw length, but the effect is greater with longer screws. On the other hand, insertional torque was directly proportional to screw diameter in both groups, consistent with previous reports. Mean torque was greater in the teriparatide group for all diameters, but a statistically significant difference was noted only for the largest diameter category (6.5–7.5 mm). These results may depend on the difference of the area of the bone-screw interface; a smaller-diameter screw may have too small an interface to be affected by teriparatide within 1–4 months of treatment. These evaluations suggest that the insertional torque increases in screws that are longer and thicker, which have a more extensive screw-bone interface, an important factor for biomechanical strength of the pedicle screw.49

Bone mineral density is one of the important indicators used to evaluate the degree of osteoporosis, and pedicle screw pullout strength is highly correlated with BMD.13 The positive correlation between BMD and the insertional torque shown in previous studies suggests that preoperative assessment of BMD may be useful in determining the ultimate strength of screw fixation in patients in whom osteoporosis is suspected.2,20,22,29,35 Based on these previous papers, the insertional torque can be affected by osteoporosis treatments via increased BMD. In this study, we investigated BMD before treatment with teriparatide. There was no significant difference between the teriparatide treatment group and the control group, indicating that the severity of osteoporosis in the groups was similar.

Intermittent administration of PTH is reported to have potent anabolic effects on bone remodeling.25 Because this treatment increases bone mass and reduces the risk of osteoporotic vertebral fractures, teriparatide already has been approved as a treatment for severe osteoporosis in the United States, Europe, and Japan.32 The Japanese trial reported that injection of 56.5 μg teriparatide weekly for 72 weeks increased lumbar BMD by 6.4%,30 and injection of 20 μg once daily for 48 weeks increased lumbar BMD by 9.9%.26 On the other hand, a randomized trial performed in 168 centers in 9 countries reported that daily injection of 100 μg of teriparatide increased lumbar BMD by only 6.9% after 72 weeks.12 Intermittent administration of PTH is recognized to have potent anabolic effects on bone remodeling, but the optimum dosing interval is still controversial. In this study, we used 2 dosing regimens for teriparatide, daily injection of 20 μg or weekly injection of 56.5 μg; both are approved in Japan. Teriparatide was administered for a minimum of 31 days and a maximum of 117 days (mean 61.4 days). A change of BMD has never been reported with such short-term administration, and this treatment duration might be too short to result in a BMD increase. However, in addition to its effect on BMD, teriparatide has been reported to affect both cancellous and cortical structure in earlier stages of treatment.19 In cancellous bone, teriparatide is reported to increase bone volume and improve trabecular architecture via “intratrabecular tunneling,” which increases the number and connectivity of trabeculae.18,25 In cortical bone, teriparatide increases both cortical porosity and thickness at the same time, which maintains cortical bone strength.16,17,19 These structural changes have been confirmed at 6 months after teriparatide treatment using high-resolution CT,11 and could be induced earlier than a measurable increase of BMD, accounting for the increase of insertional torque found in this study following a mean duration of treatment of 61.4 days.

Our study has some limitations. First, the study was not a randomized controlled trial and the sample size was small, with limited treatment duration. In this study, treatment duration differed from patient to patient, and there was no correlation between insertional torque and treatment duration. A randomized controlled trial involving a larger number of patients or screws and longer treatment duration should be encouraged in the future. Second, preoperative BMD after teriparatide treatment was not evaluated. We only compared BMD between the 2 groups before teriparatide treatment, and there was no significant difference. The change in BMD after teriparatide treatment for less than 3 months has not been previously reported. Whether increased insertional torque could be predicted by pretreatment BMD prior to surgery is an important issue that is not addressed in this paper. Further evaluation with BMD monitoring is required. Third, in this study, we included patients receiving weekly and daily teriparatide treatment in as the same group for comparison with controls. There has not been any direct comparison with respect to BMD or prevalence of fractures between these 2 types of teriparatide treatment in previous clinical trials; significantly increased BMD and reduced fracture risk have been reported independently with longer-term administration,26,30–32,48 but insertional torque was never measured. In this study, we did not compare these 2 types of teriparatide treatment in detail because of the small number of patients and screws. But our results showed no significant difference between 2 groups with respect to insertional torque after short-term treatment. We believe that further studies should be carried out to investigate the use of teriparatide to identify its effectiveness for preoperative treatment of patients with postmenopausal osteoporosis undergoing fusion surgery.

Conclusions

Teriparatide treatment for at least 1 month prior to surgery was effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide therapy could be an option for maximizing the purchase of pedicle screws in the bone at the time of fusion surgery.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Inoue, Ohtori. Acquisition of data: Inoue, Ueno, Nakazawa, Imura, Saito. Analysis and interpretation of data: Inoue, Ueno, Saito, Uchida. Drafting the article: Inoue, Toyone, Takahira, Takaso. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Inoue. Statistical analysis: Inoue. Administrative/technical/material support: Uchida. Study supervision: Takaso.

References

  • 1

    Burval DJMcLain RFMilks RInceoglu S: Primary pedicle screw augmentation in osteoporotic lumbar vertebrae: biomechanical analysis of pedicle fixation strength. Spine (Phila Pa 1976) 32:107710832007

    • Search Google Scholar
    • Export Citation
  • 2

    Bühler DWBerlemann UOxland TRNolte LP: Moments and forces during pedicle screw insertion. In vitro and in vivo measurements. Spine (Phila Pa 1976) 23:122012281998

    • Search Google Scholar
    • Export Citation
  • 3

    Chrea BMalempati HCampbell JRKhan SChing RPLee MJ: Enhancing pedicle screw fixation in the lumbar spine utilizing allograft bone plug interference fixation. J Spinal Disord Tech [epub ahead of print]2013

    • Search Google Scholar
    • Export Citation
  • 4

    Daftari TKHorton WCHutton WC: Correlations between screw hole preparation, torque of insertion, and pullout strength for spinal screws. J Spinal Disord 7:1391451994

    • Search Google Scholar
    • Export Citation
  • 5

    DeCoster TAHeetderks DBDowney DJFerries JSJones W: Optimizing bone screw pullout force. J Orthop Trauma 4:1691741990

  • 6

    Dempster DWCosman FKurland ESZhou HNieves JWoelfert L: Effects of daily treatment with parathyroid hormone on bone microarchitecture and turnover in patients with osteoporosis: a paired biopsy study. J Bone Miner Res 16:184618532001

    • Search Google Scholar
    • Export Citation
  • 7

    Esses SISachs BLDreyzin V: Complications associated with the technique of pedicle screw fixation. A selected survey of ABS members. Spine (Phila Pa 1976) 18:223122391993

    • Search Google Scholar
    • Export Citation
  • 8

    Fisher JERogers MJHalasy JMLuckman SPHughes DEMasarachia PJ: Alendronate mechanism of action: geranylgeraniol, an intermediate in the mevalonate pathway, prevents inhibition of osteoclast formation, bone resorption, and kinase activation in vitro. Proc Natl Acad Sci U S A 96:1331381999

    • Search Google Scholar
    • Export Citation
  • 9

    Fu TSChen LHWong CBLai PLTsai TTNiu CC: Computer-assisted fluoroscopic navigation of pedicle screw insertion: an in vivo feasibility study. Acta Orthop Scand 75:7307352004

    • Search Google Scholar
    • Export Citation
  • 10

    Fukunaga MSone TOtsuka NTomomitsu TImai YNogami R: Bone mineral measurement in Japan. Ann Nucl Med 11:2752801997

  • 11

    Graeff CTimm WNickelsen TNFarrerons JMarín FBarker C: Monitoring teriparatide-associated changes in vertebral microstructure by high-resolution CT in vivo: results from the EUROFORS study. J Bone Miner Res 22:142614332007

    • Search Google Scholar
    • Export Citation
  • 12

    Greenspan SLBone HGEttinger MPHanley DALindsay RZanchetta JR: Effect of recombinant human parathyroid hormone (1-84) on vertebral fracture and bone mineral density in postmenopausal women with osteoporosis: a randomized trial. Ann Intern Med 146:3263392007

    • Search Google Scholar
    • Export Citation
  • 13

    Halvorson TLKelley LAThomas KAWhitecloud TS IIICook SD: Effects of bone mineral density on pedicle screw fixation. Spine (Phila Pa 1976) 19:241524201994

    • Search Google Scholar
    • Export Citation
  • 14

    Han SLWan SL: Effect of teriparatide on bone mineral density and fracture in postmenopausal osteoporosis: meta-analysis of randomised controlled trials. Int J Clin Pract 66:1992092012

    • Search Google Scholar
    • Export Citation
  • 15

    Hannon RAClowes JAEagleton ACAl Hadari AEastell RBlumsohn A: Clinical performance of immunoreactive tartrate-resistant acid phosphatase isoform 5b as a marker of bone resorption. Bone 34:1871942004

    • Search Google Scholar
    • Export Citation
  • 16

    Hodsman ABBauer DCDempster DWDian LHanley DAHarris ST: Parathyroid hormone and teriparatide for the treatment of osteoporosis: a review of the evidence and suggested guidelines for its use. Endocr Rev 26:6887032005

    • Search Google Scholar
    • Export Citation
  • 17

    Hodsman ABKisiel MAdachi JDFraher LJWatson PH: Histomorphometric evidence for increased bone turnover without change in cortical thickness or porosity after 2 years of cyclical hPTH(1-34) therapy in women with severe osteoporosis. Bone 27:3113182000

    • Search Google Scholar
    • Export Citation
  • 18

    Jerome CPBurr DBVan Bibber THock JMBrommage R: Treatment with human parathyroid hormone (1-34) for 18 months increases cancellous bone volume and improves trabecular architecture in ovariectomized cynomolgus monkeys (Macaca fascicularis). Bone 28:1501592001

    • Search Google Scholar
    • Export Citation
  • 19

    Jiang YZhao JJMitlak BHWang OGenant HKEriksen EF: Recombinant human parathyroid hormone (1-34) [teriparatide] improves both cortical and cancellous bone structure. J Bone Miner Res 18:193219412003

    • Search Google Scholar
    • Export Citation
  • 20

    Kuklo TRLehman RA Jr: Effect of various tapping diameters on insertion of thoracic pedicle screws: a biomechanical analysis. Spine (Phila Pa 1976) 28:206620712003

    • Search Google Scholar
    • Export Citation
  • 21

    Kwok AWFinkelstein JAWoodside THearn TCHu RW: Insertional torque and pull-out strengths of conical and cylindrical pedicle screws in cadaveric bone. Spine (Phila Pa 1976) 21:242924341996

    • Search Google Scholar
    • Export Citation
  • 22

    Lee JHLee JHPark JWShin YH: The insertional torque of a pedicle screw has a positive correlation with bone mineral density in posterior lumbar pedicle screw fixation. J Bone Joint Surg Br 94:93972012

    • Search Google Scholar
    • Export Citation
  • 23

    Liu DZhang YLei WWang CRXie QYLiao DF: Comparison of 2 kinds of pedicle screws in primary spinal instrumentation: biomechanical and interfacial evaluations in sheep vertebrae in vitro. J Spinal Disord Tech 27:E72E802014

    • Search Google Scholar
    • Export Citation
  • 24

    McLain RFFry MFMoseley TASharkey NA: Lumbar pedicle screw salvage: pullout testing of three different pedicle screw designs. J Spinal Disord 8:62681995

    • Search Google Scholar
    • Export Citation
  • 25

    Miller MABare SPRecker RRSmith SYFox J: Intratrabecular tunneling increases trabecular number throughout the skeleton of ovariectomized rhesus monkeys treated with parathyroid hormone 1-84. Bone 42:117511832008

    • Search Google Scholar
    • Export Citation
  • 26

    Miyauchi AMatsumoto TSugimoto TTsujimoto MWarner MRNakamura T: Effects of teriparatide on bone mineral density and bone turnover markers in Japanese subjects with osteoporosis at high risk of fracture in a 24-month clinical study: 12-month, randomized, placebo-controlled, double-blind and 12-month open-label phases. Bone 47:4935022010

    • Search Google Scholar
    • Export Citation
  • 27

    Moore DCMaitra RSFarjo LAGraziano GPGoldstein SA: Restoration of pedicle screw fixation with an in situ setting calcium phosphate cement. Spine (Phila Pa 1976) 22:169617051997

    • Search Google Scholar
    • Export Citation
  • 28

    Muschitz CKocijan RFahrleitner-Pammer ALung SResch H: Antiresorptives overlapping ongoing teriparatide treatment result in additional increases in bone mineral density. J Bone Miner Res 28:1962052013

    • Search Google Scholar
    • Export Citation
  • 29

    Myers BSBelmont PJ JrRichardson WJYu JRHarper KDNightingale RW: The role of imaging and in situ biomechanical testing in assessing pedicle screw pull-out strength. Spine (Phila Pa 1976) 21:196219681996

    • Search Google Scholar
    • Export Citation
  • 30

    Nakamura TSugimoto TNakano TKishimoto HIto MFukunaga M: Randomized Teriparatide [human parathyroid hormone (PTH) 1-34] Once-Weekly Efficacy Research (TOWER) trial for examining the reduction in new vertebral fractures in subjects with primary osteoporosis and high fracture risk. J Clin Endocrinol Metab 97:309731062012

    • Search Google Scholar
    • Export Citation
  • 31

    Nakamura TTsujimoto MHamaya ESowa HChen P: Consistency of fracture risk reduction in Japanese and Caucasian osteoporosis patients treated with teriparatide: a meta-analysis. J Bone Miner Metab 30:3213252012

    • Search Google Scholar
    • Export Citation
  • 32

    Neer RMArnaud CDZanchetta JRPrince RGaich GAReginster JY: Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med 344:143414412001

    • Search Google Scholar
    • Export Citation
  • 33

    Ohlin AKarlsson MDüppe HHasserius RRedlund-Johnell I: Complications after transpedicular stabilization of the spine. A survivorship analysis of 163 cases. Spine (Phila Pa 1976) 19:277427791994

    • Search Google Scholar
    • Export Citation
  • 34

    Ohtori SInoue GOrita SYamauchi KEguchi YOchiai N: Comparison of teriparatide and bisphosphonate treatment to reduce pedicle screw loosening after lumbar spinal fusion surgery in postmenopausal women with osteoporosis from a bone quality perspective. Spine (Phila Pa 1976) 38:E487E4922013

    • Search Google Scholar
    • Export Citation
  • 35

    Okuyama KAbe ESuzuki TTamura YChiba MSato K: Can insertional torque predict screw loosening and related failures? An in vivo study of pedicle screw fixation augmenting posterior lumbar interbody fusion. Spine (Phila Pa 1976) 25:8588642000

    • Search Google Scholar
    • Export Citation
  • 36

    Okuyama KAbe ESuzuki TTamura YChiba MSato K: Influence of bone mineral density on pedicle screw fixation: a study of pedicle screw fixation augmenting posterior lumbar interbody fusion in elderly patients. Spine J 1:4024072001

    • Search Google Scholar
    • Export Citation
  • 37

    Orimo HHayashi YFukunaga MSone TFujiwara SShiraki M: Diagnostic criteria for primary osteoporosis: year 2000 revision. J Bone Miner Metab 19:3313372001

    • Search Google Scholar
    • Export Citation
  • 38

    Ozawa TTakahashi KYamagata MOhtori SAoki YSaito T: Insertional torque of the lumbar pedicle screw during surgery. J Orthop Sci 10:1331362005

    • Search Google Scholar
    • Export Citation
  • 39

    Pihlajämaki HMyllynen PBöstman O: Complications of transpedicular lumbosacral fixation for non-traumatic disorders. J Bone Joint Surg Br 79:1831891997

    • Search Google Scholar
    • Export Citation
  • 40

    Recker RRMarin FIsh-Shalom SMöricke RHawkins FKapetanos G: Comparative effects of teriparatide and strontium ranelate on bone biopsies and biochemical markers of bone turnover in postmenopausal women with osteoporosis. J Bone Miner Res 24:135813682009

    • Search Google Scholar
    • Export Citation
  • 41

    Sandén BOlerud CPetrén-Mallmin MLarsson S: Hydroxyapatite coating improves fixation of pedicle screws. A clinical study. J Bone Joint Surg Br 84:3873912002

    • Search Google Scholar
    • Export Citation
  • 42

    Sarzier JSEvans AJCahill DW: Increased pedicle screw pullout strength with vertebroplasty augmentation in osteoporotic spines. J Neurosurg 96:3 Suppl3093122002

    • Search Google Scholar
    • Export Citation
  • 43

    Sawakami KYamazaki AIshikawa SIto TWatanabe KEndo N: Polymethylmethacrylate augmentation of pedicle screws increases the initial fixation in osteoporotic spine patients. J Spinal Disord Tech 25:E28E352012

    • Search Google Scholar
    • Export Citation
  • 44

    Schwarz PJorgensen NRMosekilde LVestergaard P: Effects of increasing age, dosage, and duration of PTH treatment on BMD increase—a meta-analysis. Calcif Tissue Int 90:1651732012

    • Search Google Scholar
    • Export Citation
  • 45

    Skinner RMaybee JTransfeldt EVenter RChalmers W: Experimental pullout testing and comparison of variables in transpedicular screw fixation. A biomechanical study. Spine (Phila Pa 1976) 15:1952011990

    • Search Google Scholar
    • Export Citation
  • 46

    Soen SFukunaga MSugimoto TSone TFujiwara SEndo N: Diagnostic criteria for primary osteoporosis: year 2012 revision. J Bone Miner Metab 31:2472572013

    • Search Google Scholar
    • Export Citation
  • 47

    Soini JLaine TPohjolainen THurri HAlaranta H: Spondylodesis augmented by transpedicular fixation in the treatment of olisthetic and degenerative conditions of the lumbar spine. Clin Orthop Relat Res 2971111161993

    • Search Google Scholar
    • Export Citation
  • 48

    Sugimoto TShiraki MNakano TKishimoto HIto MFukunaga M: Vertebral fracture risk after once-weekly teriparatide injections: follow-up study of Teriparatide Once-Weekly Efficacy Research (TOWER) trial. Curr Med Res Opin 29:1952032013

    • Search Google Scholar
    • Export Citation
  • 49

    Upasani VVFarnsworth CLTomlinson TChambers RCTsutsui SSlivka MA: Pedicle screw surface coatings improve fixation in nonfusion spinal constructs. Spine (Phila Pa 1976) 34:3353432009

    • Search Google Scholar
    • Export Citation
  • 50

    Zdeblick TAKunz DNCooke MEMcCabe R: Pedicle screw pullout strength. Correlation with insertional torque. Spine (Phila Pa 1976) 18:167316761993

    • Search Google Scholar
    • Export Citation

If the inline PDF is not rendering correctly, you can download the PDF file here.

Article Information

Address correspondence to: Gen Inoue, M.D., Ph.D., 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. email: ginoue@kitasato-u.ac.jp.

Please include this information when citing this paper: published online June 6, 2014; DOI: 10.3171/2014.5.SPINE13656.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Insertional torque was measured using a calibrated torque wrench with a specially designed connector (Medtronic).

  • View in gallery

    The insertional torque in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group, which was 1.08 ± 0.52 Nm (p < 0.01). The data are presented as the mean ± SD. *p < 0.01.

  • View in gallery

    Upper: Insertional torque of screws stratified by length. In the teriparatide group, the insertional torque of the longer screws was significantly greater than the torque of the shorter screws (1.44 ± 0.56 Nm vs 1.14 ± 0.38 Nm, *p < 0.01). In the control group, there was no significant difference between the 2 length categories. Insertional torque was significantly greater in the teriparatide group than the control group for both screw lengths (*p < 0.05 and **p < 0.01). Lower: Insertional torque was compared for screws in 3 different diameter categories (3.5–4.0 mm, 4.5–5.5 mm, and 6.5–7.5 mm). In both control and teriparatide groups, screws with a larger diameter had greater insertional torque. The between-group difference was statistically significant for the largest diameter category (1.14 ± 0.63 Nm vs 1.49 ± 0.56 Nm, *p < 0.01).

  • View in gallery

    Scatter plots for insertional torque versus the duration of preoperative teriparatide treatment. Gray circles indicate once-daily teriparatide; white circles indicate once-weekly teriparatide. There was negligible correlation (r2 = 0.05, p < 0.01).

References

  • 1

    Burval DJMcLain RFMilks RInceoglu S: Primary pedicle screw augmentation in osteoporotic lumbar vertebrae: biomechanical analysis of pedicle fixation strength. Spine (Phila Pa 1976) 32:107710832007

    • Search Google Scholar
    • Export Citation
  • 2

    Bühler DWBerlemann UOxland TRNolte LP: Moments and forces during pedicle screw insertion. In vitro and in vivo measurements. Spine (Phila Pa 1976) 23:122012281998

    • Search Google Scholar
    • Export Citation
  • 3

    Chrea BMalempati HCampbell JRKhan SChing RPLee MJ: Enhancing pedicle screw fixation in the lumbar spine utilizing allograft bone plug interference fixation. J Spinal Disord Tech [epub ahead of print]2013

    • Search Google Scholar
    • Export Citation
  • 4

    Daftari TKHorton WCHutton WC: Correlations between screw hole preparation, torque of insertion, and pullout strength for spinal screws. J Spinal Disord 7:1391451994

    • Search Google Scholar
    • Export Citation
  • 5

    DeCoster TAHeetderks DBDowney DJFerries JSJones W: Optimizing bone screw pullout force. J Orthop Trauma 4:1691741990

  • 6

    Dempster DWCosman FKurland ESZhou HNieves JWoelfert L: Effects of daily treatment with parathyroid hormone on bone microarchitecture and turnover in patients with osteoporosis: a paired biopsy study. J Bone Miner Res 16:184618532001

    • Search Google Scholar
    • Export Citation
  • 7

    Esses SISachs BLDreyzin V: Complications associated with the technique of pedicle screw fixation. A selected survey of ABS members. Spine (Phila Pa 1976) 18:223122391993

    • Search Google Scholar
    • Export Citation
  • 8

    Fisher JERogers MJHalasy JMLuckman SPHughes DEMasarachia PJ: Alendronate mechanism of action: geranylgeraniol, an intermediate in the mevalonate pathway, prevents inhibition of osteoclast formation, bone resorption, and kinase activation in vitro. Proc Natl Acad Sci U S A 96:1331381999

    • Search Google Scholar
    • Export Citation
  • 9

    Fu TSChen LHWong CBLai PLTsai TTNiu CC: Computer-assisted fluoroscopic navigation of pedicle screw insertion: an in vivo feasibility study. Acta Orthop Scand 75:7307352004

    • Search Google Scholar
    • Export Citation
  • 10

    Fukunaga MSone TOtsuka NTomomitsu TImai YNogami R: Bone mineral measurement in Japan. Ann Nucl Med 11:2752801997

  • 11

    Graeff CTimm WNickelsen TNFarrerons JMarín FBarker C: Monitoring teriparatide-associated changes in vertebral microstructure by high-resolution CT in vivo: results from the EUROFORS study. J Bone Miner Res 22:142614332007

    • Search Google Scholar
    • Export Citation
  • 12

    Greenspan SLBone HGEttinger MPHanley DALindsay RZanchetta JR: Effect of recombinant human parathyroid hormone (1-84) on vertebral fracture and bone mineral density in postmenopausal women with osteoporosis: a randomized trial. Ann Intern Med 146:3263392007

    • Search Google Scholar
    • Export Citation
  • 13

    Halvorson TLKelley LAThomas KAWhitecloud TS IIICook SD: Effects of bone mineral density on pedicle screw fixation. Spine (Phila Pa 1976) 19:241524201994

    • Search Google Scholar
    • Export Citation
  • 14

    Han SLWan SL: Effect of teriparatide on bone mineral density and fracture in postmenopausal osteoporosis: meta-analysis of randomised controlled trials. Int J Clin Pract 66:1992092012

    • Search Google Scholar
    • Export Citation
  • 15

    Hannon RAClowes JAEagleton ACAl Hadari AEastell RBlumsohn A: Clinical performance of immunoreactive tartrate-resistant acid phosphatase isoform 5b as a marker of bone resorption. Bone 34:1871942004

    • Search Google Scholar
    • Export Citation
  • 16

    Hodsman ABBauer DCDempster DWDian LHanley DAHarris ST: Parathyroid hormone and teriparatide for the treatment of osteoporosis: a review of the evidence and suggested guidelines for its use. Endocr Rev 26:6887032005

    • Search Google Scholar
    • Export Citation
  • 17

    Hodsman ABKisiel MAdachi JDFraher LJWatson PH: Histomorphometric evidence for increased bone turnover without change in cortical thickness or porosity after 2 years of cyclical hPTH(1-34) therapy in women with severe osteoporosis. Bone 27:3113182000

    • Search Google Scholar
    • Export Citation
  • 18

    Jerome CPBurr DBVan Bibber THock JMBrommage R: Treatment with human parathyroid hormone (1-34) for 18 months increases cancellous bone volume and improves trabecular architecture in ovariectomized cynomolgus monkeys (Macaca fascicularis). Bone 28:1501592001

    • Search Google Scholar
    • Export Citation
  • 19

    Jiang YZhao JJMitlak BHWang OGenant HKEriksen EF: Recombinant human parathyroid hormone (1-34) [teriparatide] improves both cortical and cancellous bone structure. J Bone Miner Res 18:193219412003

    • Search Google Scholar
    • Export Citation
  • 20

    Kuklo TRLehman RA Jr: Effect of various tapping diameters on insertion of thoracic pedicle screws: a biomechanical analysis. Spine (Phila Pa 1976) 28:206620712003

    • Search Google Scholar
    • Export Citation
  • 21

    Kwok AWFinkelstein JAWoodside THearn TCHu RW: Insertional torque and pull-out strengths of conical and cylindrical pedicle screws in cadaveric bone. Spine (Phila Pa 1976) 21:242924341996

    • Search Google Scholar
    • Export Citation
  • 22

    Lee JHLee JHPark JWShin YH: The insertional torque of a pedicle screw has a positive correlation with bone mineral density in posterior lumbar pedicle screw fixation. J Bone Joint Surg Br 94:93972012

    • Search Google Scholar
    • Export Citation
  • 23

    Liu DZhang YLei WWang CRXie QYLiao DF: Comparison of 2 kinds of pedicle screws in primary spinal instrumentation: biomechanical and interfacial evaluations in sheep vertebrae in vitro. J Spinal Disord Tech 27:E72E802014

    • Search Google Scholar
    • Export Citation
  • 24

    McLain RFFry MFMoseley TASharkey NA: Lumbar pedicle screw salvage: pullout testing of three different pedicle screw designs. J Spinal Disord 8:62681995

    • Search Google Scholar
    • Export Citation
  • 25

    Miller MABare SPRecker RRSmith SYFox J: Intratrabecular tunneling increases trabecular number throughout the skeleton of ovariectomized rhesus monkeys treated with parathyroid hormone 1-84. Bone 42:117511832008

    • Search Google Scholar
    • Export Citation
  • 26

    Miyauchi AMatsumoto TSugimoto TTsujimoto MWarner MRNakamura T: Effects of teriparatide on bone mineral density and bone turnover markers in Japanese subjects with osteoporosis at high risk of fracture in a 24-month clinical study: 12-month, randomized, placebo-controlled, double-blind and 12-month open-label phases. Bone 47:4935022010

    • Search Google Scholar
    • Export Citation
  • 27

    Moore DCMaitra RSFarjo LAGraziano GPGoldstein SA: Restoration of pedicle screw fixation with an in situ setting calcium phosphate cement. Spine (Phila Pa 1976) 22:169617051997

    • Search Google Scholar
    • Export Citation
  • 28

    Muschitz CKocijan RFahrleitner-Pammer ALung SResch H: Antiresorptives overlapping ongoing teriparatide treatment result in additional increases in bone mineral density. J Bone Miner Res 28:1962052013

    • Search Google Scholar
    • Export Citation
  • 29

    Myers BSBelmont PJ JrRichardson WJYu JRHarper KDNightingale RW: The role of imaging and in situ biomechanical testing in assessing pedicle screw pull-out strength. Spine (Phila Pa 1976) 21:196219681996

    • Search Google Scholar
    • Export Citation
  • 30

    Nakamura TSugimoto TNakano TKishimoto HIto MFukunaga M: Randomized Teriparatide [human parathyroid hormone (PTH) 1-34] Once-Weekly Efficacy Research (TOWER) trial for examining the reduction in new vertebral fractures in subjects with primary osteoporosis and high fracture risk. J Clin Endocrinol Metab 97:309731062012

    • Search Google Scholar
    • Export Citation
  • 31

    Nakamura TTsujimoto MHamaya ESowa HChen P: Consistency of fracture risk reduction in Japanese and Caucasian osteoporosis patients treated with teriparatide: a meta-analysis. J Bone Miner Metab 30:3213252012

    • Search Google Scholar
    • Export Citation
  • 32

    Neer RMArnaud CDZanchetta JRPrince RGaich GAReginster JY: Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med 344:143414412001

    • Search Google Scholar
    • Export Citation
  • 33

    Ohlin AKarlsson MDüppe HHasserius RRedlund-Johnell I: Complications after transpedicular stabilization of the spine. A survivorship analysis of 163 cases. Spine (Phila Pa 1976) 19:277427791994

    • Search Google Scholar
    • Export Citation
  • 34

    Ohtori SInoue GOrita SYamauchi KEguchi YOchiai N: Comparison of teriparatide and bisphosphonate treatment to reduce pedicle screw loosening after lumbar spinal fusion surgery in postmenopausal women with osteoporosis from a bone quality perspective. Spine (Phila Pa 1976) 38:E487E4922013

    • Search Google Scholar
    • Export Citation
  • 35

    Okuyama KAbe ESuzuki TTamura YChiba MSato K: Can insertional torque predict screw loosening and related failures? An in vivo study of pedicle screw fixation augmenting posterior lumbar interbody fusion. Spine (Phila Pa 1976) 25:8588642000

    • Search Google Scholar
    • Export Citation
  • 36

    Okuyama KAbe ESuzuki TTamura YChiba MSato K: Influence of bone mineral density on pedicle screw fixation: a study of pedicle screw fixation augmenting posterior lumbar interbody fusion in elderly patients. Spine J 1:4024072001

    • Search Google Scholar
    • Export Citation
  • 37

    Orimo HHayashi YFukunaga MSone TFujiwara SShiraki M: Diagnostic criteria for primary osteoporosis: year 2000 revision. J Bone Miner Metab 19:3313372001

    • Search Google Scholar
    • Export Citation
  • 38

    Ozawa TTakahashi KYamagata MOhtori SAoki YSaito T: Insertional torque of the lumbar pedicle screw during surgery. J Orthop Sci 10:1331362005

    • Search Google Scholar
    • Export Citation
  • 39

    Pihlajämaki HMyllynen PBöstman O: Complications of transpedicular lumbosacral fixation for non-traumatic disorders. J Bone Joint Surg Br 79:1831891997

    • Search Google Scholar
    • Export Citation
  • 40

    Recker RRMarin FIsh-Shalom SMöricke RHawkins FKapetanos G: Comparative effects of teriparatide and strontium ranelate on bone biopsies and biochemical markers of bone turnover in postmenopausal women with osteoporosis. J Bone Miner Res 24:135813682009

    • Search Google Scholar
    • Export Citation
  • 41

    Sandén BOlerud CPetrén-Mallmin MLarsson S: Hydroxyapatite coating improves fixation of pedicle screws. A clinical study. J Bone Joint Surg Br 84:3873912002

    • Search Google Scholar
    • Export Citation
  • 42

    Sarzier JSEvans AJCahill DW: Increased pedicle screw pullout strength with vertebroplasty augmentation in osteoporotic spines. J Neurosurg 96:3 Suppl3093122002

    • Search Google Scholar
    • Export Citation
  • 43

    Sawakami KYamazaki AIshikawa SIto TWatanabe KEndo N: Polymethylmethacrylate augmentation of pedicle screws increases the initial fixation in osteoporotic spine patients. J Spinal Disord Tech 25:E28E352012

    • Search Google Scholar
    • Export Citation
  • 44

    Schwarz PJorgensen NRMosekilde LVestergaard P: Effects of increasing age, dosage, and duration of PTH treatment on BMD increase—a meta-analysis. Calcif Tissue Int 90:1651732012

    • Search Google Scholar
    • Export Citation
  • 45

    Skinner RMaybee JTransfeldt EVenter RChalmers W: Experimental pullout testing and comparison of variables in transpedicular screw fixation. A biomechanical study. Spine (Phila Pa 1976) 15:1952011990

    • Search Google Scholar
    • Export Citation
  • 46

    Soen SFukunaga MSugimoto TSone TFujiwara SEndo N: Diagnostic criteria for primary osteoporosis: year 2012 revision. J Bone Miner Metab 31:2472572013

    • Search Google Scholar
    • Export Citation
  • 47

    Soini JLaine TPohjolainen THurri HAlaranta H: Spondylodesis augmented by transpedicular fixation in the treatment of olisthetic and degenerative conditions of the lumbar spine. Clin Orthop Relat Res 2971111161993

    • Search Google Scholar
    • Export Citation
  • 48

    Sugimoto TShiraki MNakano TKishimoto HIto MFukunaga M: Vertebral fracture risk after once-weekly teriparatide injections: follow-up study of Teriparatide Once-Weekly Efficacy Research (TOWER) trial. Curr Med Res Opin 29:1952032013

    • Search Google Scholar
    • Export Citation
  • 49

    Upasani VVFarnsworth CLTomlinson TChambers RCTsutsui SSlivka MA: Pedicle screw surface coatings improve fixation in nonfusion spinal constructs. Spine (Phila Pa 1976) 34:3353432009

    • Search Google Scholar
    • Export Citation
  • 50

    Zdeblick TAKunz DNCooke MEMcCabe R: Pedicle screw pullout strength. Correlation with insertional torque. Spine (Phila Pa 1976) 18:167316761993

    • Search Google Scholar
    • Export Citation

TrendMD

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 409 409 23
PDF Downloads 286 286 25
EPUB Downloads 0 0 0

PubMed

Google Scholar