Parathyroid hormone--a drug for orthopedic surgery?

Intermittent PTH Administration Increases Bone-Specific Blood Vessels and Surrounding Stromal Cells in Murine Long Bones

To verify whether PTH acts on bone-specific blood vessels and on cells surrounding these blood vessels, 6-week-old male mice were subjected to vehicle (control group) or hPTH [1-34] (20 µg/kg/day, PTH group) injections for 2 weeks. Femoral metaphyses were used for histochemical and immunohistochemical studies. In control metaphyses, endomucin-positive blood vessels were abundant, but αSMA-reactive blood vessels were scarce. In the PTH-administered mice, the lumen of endomucin-positive blood vessels was markedly enlarged. Moreover, many αSMA-positive cells were evident near the blood vessels, and seemed to derive from those vessels. These αSMA-positive cells neighboring the blood vessels showed features of mesenchymal stromal cells, such as immunopositivity for c-kit and tissue nonspecific alkaline phosphatase (TNALP). Thus, PTH administration increased the population of perivascular/stromal cells positive for αSMA and c-kit, which were likely committed to the osteoblastic lineage. To understand the cellular events that led to increased numbers and size of bone-specific blood vessels, we performed immunohistochemical studies for PTH/PTHrP receptor and VEGF. After PTH administration, PTH/PTHrP receptor, VEGF and its receptor flk-1 were consistently identified in both osteoblasts and blood vessels (endothelial cells and surrounding perivascular cells). Our findings suggest that exogenous PTH increases the number and size of bone-specific blood vessels while fostering perivascular/stromal cells positive for αSMA/TNALP/c-kit.

Present and future scope of recombinant parathyroid hormone therapy in orthopaedics

Parathyroid Hormone (PTH) has a significant role in calcium metabolism. Its intermittent administration has an anabolic effect on bone mineralization. Teriparatide (PTH 1-34), a recombinant form of parathyroid hormone, is useful in the treatment of osteoporosis, fracture healing, non-union, stress fracture, augmentation of implant fixation with bone, and chondroprotection in osteoarthritis. The present review article will elaborate on the potential approved uses of recombinant PTH in orthopedics and its evolving role in the management of fracture osteosynthesis and other common challenging bone pathologies.

Low acceptance of osteoanabolic therapy with parathyroid hormone in patients with fragility fracture of the pelvis in routine clinical practice: a retrospective observational cohort study

INTRODUCTION

A recent randomized controlled trial has reported full patient compliance and no adverse events from therapy with parathyroid hormone (PTH) for osteoporosis and accelerated healing of fragility fractures of the pelvis. The purpose of the presented study was to evaluate if similar results can be achieved with comprehensive PTH therapy in routine clinical practice. We hypothesised that patients' burden of PTH therapy is underestimated in the literature.

PATIENTS AND METHODS

Osteoanabolic PTH therapy was recommended to 79 patients suffering from an acute fragility fracture of the pelvis (FFP). Case finding, initiation of therapy and follow-up were performed by a fracture liaison service team. Primary outcome was PTH initiation rate. Secondary outcomes were implementation rate of alternative antiresorptive pharmaceutical therapy for osteoporosis and participation rate in a bone metabolic workup. Adverse events and effects potentially related to the therapy with bone-active drugs were documented as exploratory outcomes.

RESULTS

Osteoanabolic PTH therapy as suggested was accepted by 32%, whereas antiresorptive therapy was implemented in another 14% of the patients. DEXA scans were available in 38% of the patients (+ 27% when compared to baseline). A bone-specific laboratory analysis was done in 18 patients, uncovering 7 pathological findings. Two patients terminated PTH therapy early because of side effects.

CONCLUSION

The experiences with PTH therapy in FFP patients with respect to, implementation rate, frequency of side effects and of pathological findings in laboratory controls as reported from a previous RCT could not be reproduced in routine clinical practice.

Locally administrated single-dose teriparatide affects critical-size rabbit calvarial defects: A histological, histomorphometric and micro-CT study

OBJECTIVE

The aim of this study was to evaluate the effect of teriparatide (PTH 1-34, rhPTH) on a rabbit defect model with local xenogen grafts histomorphometrically and radiologically.

METHODS

For this purpose, two 10 mm diameter critical-size defects were created in the calvaria of 16 rabbits. In the control group, the defect area was filled with a xenogen graft, while in the teriparatide group (PTH 1-34), a xenogen graft combination with 20 mcg teriparatide was used. For both 4 - week and 8 - week study groups, new bone, residual graft, and soft tissue areas were evaluated as well as bone volume histomorphometrically and radiologically.

RESULTS

Histomorphometrically, there was a significant difference in new bone area values at the 8th week (p < 0.05), but there was no significant difference between the 4 - week values (p > 0.05). There was no statistically significant difference between the groups at both 4 and 8 weeks (p > 0.05). In the radiologically measured total bone volume values, PTH1-34 group values were found to be significantly higher for both 4 - and 8 - weeks values compared to the control groups (p < 0.05).

CONCLUSION

In this study, rhPTH, which is used locally in defect areas to be repaired with bone grafts, increases both new bone volume and total bone volume.

Effect of high-frequency loading and parathyroid hormone administration on peri-implant bone healing and osseointegration

The objective of this study is to examine the effect of low-magnitude, high-frequency (LMHF) loading, and anti-osteoporosis medications such as parathyroid hormone (PTH) and bisphosphonates on peri-implant bone healing in an osteoporosis model, and to assess their combined effects on these processes. Thirteen-week-old ovariectomized rats (n = 44) were divided into three groups: PTH, alendronate, and saline. After 3 weeks of drug administration, titanium implants were inserted into the tibiae. Each group was subdivided into two groups: with or without LMHF loading via whole-body vibration (50 Hz at 0.5 g, 15 min per day, 5 days per week). Rats were killed 4 weeks following implantation. Removal torque test, micro-CT analyses (relative gray (RG) value, water = 0, and implant = 100), and histomorphometric analyses (bone-to-implant contact (BIC) and peri-implant bone formation (bone volume/tissue volume (BV/TV))) were performed. Removal torque values and BIC were significantly differed by loading and drug administration (ANOVA). Post hoc analysis showed that PTH-treated groups were significantly higher than the other drug-treated groups. BV/TV was significantly enhanced by PTH administration. In cortical bone, RG values were significantly increased by loading. In trabecular bone, however, RG values were significantly increased by PTH administration. These findings suggest that LMHF loading and PTH can act locally and additively on the bone healing process, improving the condition of implant osseointegration.

Whole-body vibration and administration of a hormone used to treat osteoporosis can enhance bone healing at the site of a titanium implant. Toru Ogawa of Tohoku University Graduate School of Dentistry in Sendai, Japan, and colleagues gave anti-osteoporosis medications, either parathyroid hormone or the bisphosphonate drug alendronate, to female rat models of osteoporosis. After three weeks of drug administration or a saline control, the researchers inserted titanium implants into the rats’ leg bones. Half the rats were then exposed to whole-body vibration, which applies low-magnitude, high-frequency mechanical forces. A multitude of tests showed that parathyroid hormone improved bone healing at the implant more than alendronate or saline did. The vibrational stimulus further increased the healing. The findings suggest that these treatments could aid in oral bone healing for patients receiving dental implants.

Bone grafts and biomaterials substitutes for bone defect repair: A review

Bone grafts have been predominated used to treat bone defects, delayed union or non-union, and spinal fusion in orthopaedic clinically for a period of time, despite the emergency of synthetic bone graft substitutes. Nevertheless, the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies. Hence, the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important. To address this problem, addition of various growth factors, such as bone morphogenetic proteins (BMPs), parathyroid hormone (PTH) and platelet rich plasma (PRP), into structural allografts and synthetic substitutes have been considered. Although clinical applications of these factors have exhibited good bone formation, their further application was limited due to high cost and potential adverse side effects. Alternatively, bioinorganic ions such as magnesium, strontium and zinc are considered as alternative of osteogenic biological factors. Hence, this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

PTH 1-34 (teriparatide) may not improve healing in proximal humerus fractures. A randomized, controlled study of 40 patients

BACKGROUND AND PURPOSE

There is solid evidence from animal experiments that parathyroid hormone (PTH) improves fracture healing. So far, only 3 papers on PTH and fracture repair in humans have been published. They suggest that PTH may enhance fracture healing, but the results do not appear to justify specific clinical recommendations. This study was carried out to determine whether teriparatide enhances fracture healing of proximal humerus fractures.

PATIENTS AND METHODS

40 post-menopausal women with a proximal humerus fracture were randomized to either daily injections with 20 µg teriparatide (PTH 1-34 (Forteo)) for 4 weeks or control treatment. At randomization, the patients were asked to assess how their pain at rest and during activity (visual analog scale (VAS)) and also function (DASH score) had been prior to the fracture. At 7 weeks and again at 3 months, their current state was assessed and the tests were repeated, including radiographs. 2 radiologists performed a blind qualitative scoring of the callus at 7 weeks. Callus formation was arbitrarily classified as "normal" or "better".

RESULTS

39 patients completed the follow-up. The radiographic assessment showed a correct correlation, "better" in the teriparatide group and "normal" in the control group, in 21 of the 39 cases. There were no statistically significant differences in pain, in use of strong analgesics, or in function between the groups at the follow-up examinations.

INTERPRETATION

There were no radiographic signs of enhanced healing or improved clinical results in the group treated with teriparatide.

Treatment study of distal femur for parathyroid hormone (1-34) and β-tricalcium phosphate on bone formation in critical-sized defects in osteopenic rats

The objective of this study was to evaluate the effect of following combined treatment with parathyroid hormone (1-34) (PTH) and β-tricalcium phosphate (β-TCP) on local bone formation in a rat 3-mm critical-sized defect at the distal femur. Fourteen weeks were allowed to pass before defect surgery for the establishment of osteopenic animal models chronically fed a low-protein diet. All animals were randomly divided into four groups: group PTH; group β-TCP, group PTH + β-TCP, and a control group. All rats then underwent a surgical procedure to create bone defects in the bilateral distal femurs, and β-TCP was implanted into critical-sized defects for the groups designated as β-TCP and group PTH + β-TCP. After the defect operation, all animals from group PTH and group PTH + β-TCP received following subcutaneous injections with PTH (60 μg/kg, three times per week) until euthanasia at 4 and 8 weeks. The distal femurs and blood were collected for evaluation. The results of study showed the strongest effect on accelerating the local bone formation with treatment β-TCP and PTH at 4 weeks and 8 weeks. The results from our study demonstrate that a combination of PTH and β-TCP had an additive effect on local bone formation in osteopenic rats chronically fed a low-protein diet.

Treatment study of distal femur for parathyroid hormone (1-34) and β-tricalcium phosphate on bone formation in critical size defects in rats

The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34), a surgically implanted synthetic β-tricalcium phosphate bone biomaterial serving as a matrix to support new bone formation. Twelve weeks after bilateral ovariectomy, all rats underwent bone defect in the distal femurs, and β-tricalcium phosphate was implanted into critical sized defects. After defect operation, all animals were randomly divided into four groups and received following subcutaneous injections until death at four and eight weeks: sham rats (group ST); sham rats + parathyroid hormone, 30 µg/kg, three times a week (group SPT); OVX rats (group OT); and OVX rats + parathyroid hormone (group OPT). The distal femurs of rats were harvested for evaluation. The treatment group demonstrating the highest levels of new bone formation was the defects treated with parathyroid hormone as assessed by micro-computed tomography, biomechanical strength, and histological analysis for sham rats. Furthermore, parathyroid hormone showed a stronger effect on accelerating the degradation of β-tricalcium phosphate. Osteoporosis can limit the function of parathyroid hormone and/or β-tricalcium phosphate. The results from our study demonstrate that combination of parathyroid hormone and β-tricalcium phosphate brings better effect to bone tissue repair in non-osteoporosis and/or osteoporosis status.

Low dose PTH improves metaphyseal bone healing more when muscles are paralyzed

Stimulation of bone formation by PTH is related to mechanosensitivity. The response to PTH treatment in intact bone could therefore be blunted by unloading. We studied the effects of mechanical loading on the response to PTH treatment in bone healing. Most fractures occur in the metaphyses, therefor we used a model for metaphyseal bone injury. One hind leg of 20 male SD rats was unloaded via intramuscular botulinum toxin injections. Two weeks later, the proximal unloaded tibia had lost 78% of its trabecular contents. At this time-point, the rats received bilateral proximal tibiae screw implants. Ten of the 20 rats were given daily injections of 5 μg/kg PTH (1-34). After two weeks of healing, screw fixation was measured by pull-out, and microCT of the distal femur cancellous compartment was performed. Pull-out force provided an estimate for cancellous bone formation after trauma. PTH more than doubled the pull-out force in the unloaded limbs (from 14 to 30 N), but increased it by less than half in the loaded ones (from 30 to 44 N). In relative terms, PTH had a stronger effect on pull-out force in unloaded bone than in loaded bone (p=0.03). The results suggest that PTH treatment for stimulation of bone healing does not require simultaneous mechanical stimulation.

Accelerated fracture healing with teriparatide

Satisfactory healing of the osteoporotic fracture is critically important to functional recovery, morbidity, and quality of life. Some therapies for osteoporosis may affect the processes associated with bone repair. For example, bisphosphonates in experimental models are associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. For the osteoanabolic agent teriparatide, case reports and a randomized trial have produced mixed results, but they are consistent with a positive impact of teriparatide on fracture healing. Some of the agents currently being developed for osteoporosis, notably sclerostin and DKK1 antibodies have shown a beneficial effect on fracture healing. At this point, therefore, there is no evidence that osteoporosis therapies are detrimental to fracture healing with some promising experimental evidence for positive effects on healing, notably for those agents whose actions are primarily anabolic.

Annotation: parathyroid hormone and fracture healing

This annotation describes some early rat studies which conclude that parathyroid hormone (PTH) has more dramatic stimulatory effects on bone repair than on untraumatized bone. It also suggests, based on the effects of PTH on osteoblasts, that it is more likely to accelerate normal fracture healing than to prevent non-union. The only 2 controlled clinical trials that have been published are critically discussed. Although both are encouraging and appear to show acceleration of normal fracture healing, they have methodological shortcomings that preclude definitive conclusions.

Effect of bone morphogenetic protein-2, demineralized bone matrix and systemic parathyroid hormone (1-34) on local bone formation in a rat calvaria critical-size defect model

AIM

To determine the potential of recombinant human bone morphogenetic protein-2 (rhBMP-2) soak-loaded on to an absorbable collagen sponge (ACS) to induce local bone formation compared with the clinical reference demineralized bone matrix (DBM) and to investigate potential additive/synergistic effects of exogenous parathyroid hormone (PTH).

METHODS

Critical-size (8 mm), through-through calvaria osteotomy defects in 160 adult male Sprague-Dawley rats were randomized to receive one of eight interventions: rhBMP-2/ACS, DBM, ACS, or serve as controls (empty defects) combined or not with systemic PTH. Ten animals from each group were followed for 4 and 8 wks for radiographic and histometric analysis. Multivariable analysis was used to assess the effect of experimental intervention and healing time on local bone formation.

RESULTS

In the multivariable analysis, rhBMP-2/ACS exhibited significantly greater histologic bone formation than control (β ± SE: 54.76 ± 5.85, p < 0.001) and ACS (β ± SE: 9.14 ± 3.31, p = 0.007) whereas DBM showed significantly less bone formation than control (β ± SE: -32.32 ± 8.23, p < 0.001). Overall, PTH did not show a significant effect on bone formation (β ± SE: 2.72 ± 6.91, p = 0.70). No significant differences in histological defect closure were observed between 4 and 8 wks for all but the control group without PTH.

CONCLUSION

rhBMP-2/ACS significantly stimulates local bone formation whereas bone formation appears significantly limited by DBM. Systemic application of PTH provided no discernible additive/synergistic effects on local bone formation.

Serum intact-parathyroid hormone level following total knee arthroplasty

PURPOSE

To evaluate short-term parathyroid hormone (PTH) secretion following total knee arthroplasty (TKA).

METHODS

119 Caucasian postmenopausal women aged 49 to 81 (mean, 69.8) years who underwent TKA for end-stage knee osteoarthritis were included. Serum levels of intact-PTH, calcium, phosphorus, and creatinine were evaluated pre- and post-operatively (on days -1 and 7). Creatinine clearance was also calculated.

RESULTS

In 67 of the patients, serum intact-PTH levels decreased after TKA; this sample proportion was not significant (p=0.82). In 16 of the patients, such levels elevated abnormally (above normal range). In the remaining 36 patients, such levels elevated within the normal range. Therefore, the mean serum intact- PTH level of all patients increased slightly after TKA (45.4 vs. 45.3, p=0.162). The serum intact-PTH level did not correlate to body weight (r=-0.045, p=0.624), patient age (r=-0.061, p=0.508), serum creatinine level (r=0.084, p=0.366), and clearance of creatinine (r=-0.037, p=0.692).

CONCLUSION

In most postmenopausal women, the serum intact-PTH level decreased moderately following TKA, but in some, the level was abnormally elevated. This may interfere the prosthesis incorporation process.

Successful treatment of sternal fracture nonunion with teriparatide

SUMMARY

Fractures have a significant impact on the quality of life for the patient in addition to an enormous indirect cost in lost productivity for our economy. While majority of fractures heal uneventfully, some fail to heal even after many months resulting in nonunion.

INTRODUCTION

Sternal nonunions, although rare, are particularly onerous for the patient given the magnitude of impact on quality of life.

METHODS

Current treatment for fracture nonunions emphasizes various approaches to surgical fixation in addition to bone grafting. These treatments are aggressive and have a variety of drawbacks, rendering them suboptimal as a therapeutic approach.

CONCLUSION

Based on the success of teriparatide in animal studies to accelerate fracture healing, there is growing interest in using this drug in humans for the same purpose. We report a case of what we believe to be the first successful use of teriparatide in the healing of a sternal nonunion fracture.

PTH improves titanium implant fixation more than pamidronate or renutrition in osteopenic rats chronically fed a low protein diet

SUMMARY

We evaluated the effects of parathyroid hormone (PTH), pamidronate, or renutrition on osseointegration of titanium implants in the proximal tibia of rats subject to prolonged low-protein diets. PTH improved mechanical fixation, microarchitecture, and increased pull-out strength. Pamidronate or renutrition had lesser effects. PTH can thus improve implant osseointegration in protein-malnourished rats.

INTRODUCTION

Protein malnutrition impairs implant osseointegration in rats. PTH and pamidronate prevent deleterious effects of protein restriction introduced just prior to implantation. Whether these treatments improve osseointegration after chronic protein deprivation, i.e., in osteopenic bone at time of implantation, is unknown. We evaluated effects of PTH, pamidronate, or renutrition on resistance to pull-out of titanium rods implanted into the rat tibiae following isocaloric low-protein intake.

METHODS

Forty-one adult female rats received normal or isocaloric low-protein diets. Six weeks later, implants were surgically inserted into proximal tibiae. Following implantation, rats on low-protein diets were treated with PTH (1-34), pamidronate, saline vehicle, or normal protein diets, for another 8 weeks. Tibiae were removed for micro-computerised tomographic morphometry and evaluation of pull-out strength.

RESULTS

Pull-out strength decreased in rats on isocaloric low-protein diets compared with normal protein group (-33.4%). PTH increased pull-out strength in low-protein group, even compared to controls from the normal protein group. PTH and pamidronate increased bone volume/tissue volume, bone-to-implant contact, and trabecular thickness, whilst trabecular separation was reduced, with a shift to more plate-like bone surrounding the implants.

CONCLUSIONS

PTH reversed the deleterious effects of long-term protein undernutrition on mechanical fixation and bone microarchitecture and improved implant osseointegration more than pamidronate or renutrition, likely through changes to structure model index.

Teriparatide improves early callus formation in distal radial fractures

BACKGROUND

Teriparatide (parathyreoid hormone; PTH 1-34) increases skeletal mass in humans and improves fracture healing in animals. A recent randomized multicenter trial of nonoperated distal radial fractures showed a moderate shortening of the time to restoration of cortical continuity by treatment with 20 microg (low-dose) teriparatide per day, but not with 40 microg (high-dose). As radiographic cortical continuity appears late in the healing process, perhaps too late for clinical relevance, we studied the qualitative appearance of the callus 5 weeks after fracture.

METHODS

One third of the patients of the international trial were treated at Linköping University Hospital. The multicenter trial did not evaluate early callus formation. We therefore made a blinded qualitative scoring of the callus at 5 weeks in our 27 patients. Callus formation was arbitrarily classified as rich, intermediate, or poor.

RESULTS

9 patients were classified as rich (none had received placebo, 3 low-dose teriparatide, and 6 high-dose teriparatide). 9 patients were classified as intermediate (1 had received placebo, 5 low-dose, and 3 high-dose). 9 patients were classified as poor (7 had received placebo, 1 low-dose, and 1 high-dose) (p < 0.001).

INTERPRETATION

This is a post hoc subgroup analysis of an outcome variable, which was not in the official protocol. The results must therefore be interpreted with caution. However, in combination with the results of the larger trial, the data suggest that radiographic quality at an early time point might be a sensitive variable, perhaps better than time to cortical continuity. Moreover, teriparatide appeared to improve early callus formation in distal radial fractures.

Effect of systemic parathyroid hormone (1-34) and a beta-tricalcium phosphate biomaterial on local bone formation in a critical-size rat calvarial defect model

OBJECTIVE

The objective of this study was to evaluate local bone formation following systemic administration of parathyroid hormone (1-34) (PTH), a surgically implanted synthetic beta-tricalcium phosphate (beta-TCP) bone biomaterial serving as a matrix to support new bone formation.

MATERIALS AND METHODS

Critical-size, 8 mm, calvarial through-and-through osteotomy defects were surgically created in 100 adult male Sprague-Dawley rats. The animals were randomized into five groups of 20 animals each to receive one of the following treatments: PTH (15 microg PTH/kg/day; subcutaneously), PTH/beta-TCP, beta-TCP, or particulate human demineralized freeze-dried bone (DFDB), and sham-surgery controls. Ten animals/group were euthanized at 4 and 8 weeks post-surgery for radiographic and histometric analysis.

RESULTS

The histometric analysis showed that systemic PTH significantly enhanced local bone formation, bone fill averaging (+/-SE) 32.2+/-4.0% compared with PTH/beta-TCP (15.7+/-2.4%), beta-TCP (12.5+/-2.3%), DFDB (14.5+/-2.3%), and sham-surgery control (10.0+/-1.5%) at 4 weeks (p<0.014). Systemic PTH showed significantly enhanced bone formation (41.5+/-4.0%) compared with PTH/beta-TCP (22.4+/-3.0%), beta-TCP (21.3+/-4.4%), and with the sham-surgery control (23.8+/-4.2%) at 8 weeks (p<0.025). The DFDB group showed significantly increased bone formation from 4 (14.5+/-2.3%) to 8 weeks (32.0+/-3.2%) (p<0.006). The PTH/beta-TCP and beta-TCP groups both showed limited biomaterials resorption. The radiographic analysis was not diagnostic to distinguish local bone formation from the radiopaque beta-TCP biomaterial.

CONCLUSIONS

Systemic administration of PTH significantly stimulates local bone formation. Bone formation was significantly limited by the beta-TCP biomaterial.

Effect of intermittent systemic administration of recombinant parathyroid hormone (1-34) on mandibular fracture healing in rats

PURPOSE

To establish a rat mandibular fracture model and investigate the short- and long-term effects of recombinant parathyroid hormone (PTH 1-34) on mandibular fracture healing in rats.

MATERIALS AND METHODS

A controlled unilateral mandibular fracture was created surgically in 29 male Sprague-Dawley rats and then stabilized using an external fixation device. The rats were divided into 2 groups: 1 group received daily subcutaneous injections of 10 microg/kg of PTH(1-34) and 1 group served as the vehicle control. The rats were killed on postoperative days 7 and 21, and radiographic densitometry and histologic evaluation of new bone formation were performed.

RESULTS

A novel unilateral mandibular fracture model was established that has significant differences from previously published models, both in the location of the osteotomy site and in the rigid external stabilization device. The PTH(1-34) treated rats showed a statistically significant difference (P < .05) in callous formation compared with the control animals. Radiographic densitometry evaluation of the injury site revealed an increase in bone density, apparent at day 7 in the experimental group. Visual inspection of the histologic sections stained with Masson's trichrome blue showed an apparent increase in new bone formation at 21 days in the PTH-treated group compared with the control group.

CONCLUSIONS

Intermittent systemic administration of PTH(1-34) might enhance the healing of mandibular fractures in the early phase (7-day period). Long-term administration (21-day period) showed no statistically significant differences between the control and experimental group by radiographic densitometry.

Teriparatide for acceleration of fracture repair in humans: a prospective, randomized, double-blind study of 102 postmenopausal women with distal radial fractures

Animal experiments show a dramatic improvement in skeletal repair by teriparatide. We tested the hypothesis that recombinant teriparatide, at the 20 microg dose normally used for osteoporosis treatment or higher, would accelerate fracture repair in humans. Postmenopausal women (45 to 85 years of age) who had sustained a dorsally angulated distal radial fracture in need of closed reduction but no surgery were randomly assigned to 8 weeks of once-daily injections of placebo (n = 34) or teriparatide 20 microg (n = 34) or teriparatide 40 microg (n = 34) within 10 days of fracture. Hypotheses were tested sequentially, beginning with the teriparatide 40 microg versus placebo comparison, using a gatekeeping strategy. The estimated median time from fracture to first radiographic evidence of complete cortical bridging in three of four cortices was 9.1, 7.4, and 8.8 weeks for placebo and teriparatide 20 microg and 40 microg, respectively (overall p = .015). There was no significant difference between the teriparatide 40 microg versus placebo groups (p = .523). In post hoc analyses, there was no significant difference between teriparatide 40 microg versus 20 microg (p = .053); however, the time to healing was shorter in teriparatide 20 microg than placebo (p = .006). The primary hypothesis that teriparatide 40 microg would shorten the time to cortical bridging was not supported. The shortened time to healing for teriparatide 20 microg compared with placebo still may suggest that fracture repair can be accelerated by teriparatide, but this result should be interpreted with caution and warrants further study.

Strontium ranelate enhances callus strength more than PTH 1-34 in an osteoporotic rat model of fracture healing

Treatment of an underlying disease is often initiated after the occurrence of an osteoporotic fracture. Our aim was to investigate whether teriparatide (PTH 1-34) and strontium ranelate affect fracture healing in ovariectomized (OVX) rats when provided for the first time after the occurrence of an osteoporotic fracture. We combined the model of an OVX rat with a closed diaphyseal fracture. Sixty Sprague Dawley rats were randomly assigned to four groups. Fracture healing in OVX rats after treatment with pharmacological doses of strontium ranelate and PTH 1-34 was compared with OVX and sham-treated control groups. After 28 days, the femur was excised and scanned by micro computed tomography and the callus evaluated, after which biomechanical torsional testing was performed and torque and toughness until reaching the yield point were analyzed. Only treatment with strontium ranelate led to a significant increase in callus resistance compared to the OVX control rats, whereas both PTH 1-34 and strontium ranelate increased the bone volume/tissue volume ratio of the callus. The PTH 1-34-increased trabecular bone volume within the callus was even higher compared to sham. As for the callus tissue volume, the increase induced by strontium ranelate was significant, contrary to the changes induced by PTH. Callus in strontium ranelate-treated animals is more resistant to torsion compared with OVX control rats. To our knowledge, this is the first report of the enhancement of fracture healing by strontium ranelate. Because both treatments enhance bone and tissue volume within the callus, there may be a qualitative difference between the calluses of PTH 1-34- and strontium ranelate-treated OVX rats. The superior results obtained with strontium ranelate compared to PTH in terms of callus resistance could be the consequence of a better quality of the new bone formed within the callus.

Incidence of secondary hyperparathyroidism among postmenopausal women with end-stage knee osteoarthritis

PURPOSE

To evaluate the incidence of secondary hyperparathyroidism (SH) among postmenopausal women with end-stage knee osteoarthritis scheduled for total knee replacement (TKR).

METHODS

283 Caucasian postmenopausal women aged 49 to 81 (mean, 70) years with end-stage idiopathic knee osteoarthritis were scheduled to undergo primary TKR. They had been menopausal for 7 to 31 (mean, 19) years. Their preoperative serum levels of intact parathyroid hormone (I-PTH), calcium, phosphorus, creatinine, and the clearance of creatinine were evaluated.

RESULTS

100 patients had abnormally elevated serum I-PTH. The overall incidence of SH was 35%. Serum levels of calcium and phosphorus were elevated in 33 and 12 patients, respectively. The serum level of I-PTH correlated positively with patient age (r=0.158, p=0.008) and serum creatinine level (r=0.138, p=0.021) and negatively with clearance of creatinine (r= -0.169, p=0.004).

CONCLUSION

SH is common among elderly postmenopausal women and may affect bone healing and implant fixation. Preoperative screening/evaluation of the serum PTH level in postmenopausal women scheduled for TKR is recommended.

Can we improve fixation and outcomes in the treatment of femoral neck fractures? The use of pharmaceuticals

Femoral neck fracture rates are on the rise with an estimated 500,000 occurring annually by 2040. Despite the mainstay of open reduction and internal fixation, nonunion rates of up to 33% have been reported for displaced femoral neck fractures. Recently, increasing attention has been focused upon the role of osteobiologics to stimulate fracture repair. This article looks at the role of these anabolic compounds and discusses their potential future roles in augmenting the treatment of this condition.

Recombinant human parathyroid hormone (PTH 1-34) and low-intensity pulsed ultrasound have contrasting additive effects during fracture healing

Fracture healing is thought to be naturally optimized; however, recent evidence indicates that it may be manipulated to occur at a faster rate. This has implications for the duration of morbidity associated with bone injuries. Two interventions found to accelerate fracture healing processes are recombinant human parathyroid hormone [1-34] (PTH) and low-intensity pulsed ultrasound (LIPUS). This study aimed to investigate the individual and combined effects of PTH and LIPUS on fracture healing. Bilateral midshaft femur fractures were created in Sprague-Dawley rats, and the animals treated 7 days/week with PTH (10 microg/kg) or a vehicle solution. Each animal also had one fracture treated for 20 min/day with active-LIPUS (spatial-averaged, temporal-averaged intensity [I(SATA)]=100 mW/cm(2)) and the contralateral fracture treated with inactive-LIPUS (placebo). Femurs were harvested 35 days following injury to permit micro-computed tomography, mechanical property and histological assessments of the fracture calluses. There were no interactions between PTH and LIPUS indicating that their effects were additive rather than synergistic. These additive effects were contrasting with LIPUS primarily increasing total callus volume (TV) without influencing bone mineral content (BMC), and PTH having the opposite effect of increasing BMC without influencing TV. As a consequence of the effect of LIPUS on TV but not BMC, it decreased volumetric bone mineral density (vBMD) resulting in a less mature callus. The decreased maturity and persistence of cartilage at the fracture site when harvested offset any beneficial mechanical effects of the increased callus size with LIPUS. In contrast, the effect of PTH on callus BMC but not TV resulted in increased callus vBMD and a more mature callus. This resulted in PTH increasing fracture site mechanical strength and stiffness. These data suggest that PTH may have utility in the treatment of acute bone fractures, whereas LIPUS at an I(SATA) of 100 mW/cm(2) does not appear to be indicated in the management of closed, diaphyseal fractures.

Effect of alendronate and intermittent parathyroid hormone on implant fixation in ovariectomized rats

BACKGROUND

Intermittent administration of parathyroid hormone (PTH) leads to bone formation by increasing osteoblast numbers and activity levels. Animal studies have shown that intermittent PTH administration increases implant fixation in normal rats. The purpose of this study was to analyze the osseous incorporation of an implant in osteoporotic rats while treating them with intermittent PTH (1-34) or alendronate.

METHODS

A total of 36 ovariectomized (OVX) Wistar rats were randomized into three groups. Polymethylmethacrylate cement rods were implanted in one tibia in each rat. The three groups received daily PTH (60 mug/kg body weight [BW]), alendronate (200 mug/kg BW), or saline (0.5 ml/kg BW). A sham-ovariectomized group (n = 12) was treated with saline. After 2 weeks, the area around the implants was analyzed by histomorphometry for bone volume density (BVD) and implant bone contact. Bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry.

RESULTS

The BVD was higher in the specimens treated with PTH than in the other groups. PTH improved the BVD, BMD, and implant bone contact. Alendronate doubled the implant bone contact compared to the OVX and sham groups but did not improve BVD or BMD.

CONCLUSIONS

These findings confirm that intermittent PTH enhances implant fixation in osteoporotic bone. The clinical significance of these findings is that application of intermittent PTH may be beneficial for early implant fixation in fractures, nonunions, and prosthetic replacements when bone density is decreased.

Global burden of trauma: Need for effective fracture therapies

Orthopedic trauma care and fracture management have advanced significantly over the last 50 years. New developments in the biology and biomechanics of the musculoskeletal system, fixation devices, and soft tissue management have greatly influenced our ability to care for musculoskeletal injuries. Many therapies and treatment modalities have the potential to transform future orthopedic treatment by decreasing invasive procedures and providing shorter healing times. Promising results in experimental models have led to an increase in clinical application of these therapies in human subjects. However, for many modalities, precise clinical indications, timing, dosage, and mode of action still need to be clearly defined. In order to further develop fracture management strategies, predict outcomes and improve clinical application of newer technologies, further research studies are needed. Together with evolving new therapies, the strategies to improve fracture care should focus on cost effectiveness. This is a great opportunity for the global orthopedic community, in association with other stakeholders, to address the many barriers to the delivery of safe, timely, and effective care for patients with musculoskeletal injuries in developing countries.

Bisphosphonates can block the deterioration in implant fixation after withdrawal of intermittent doses of parathyroid hormone

We have examined the deterioration of implant fixation after withdrawal of parathyroid hormone (PTH) in rats. First, the pull-out force for stainless-steel screws in the proximal tibia was measured at different times after withdrawal. The stimulatory effect of PTH on fixation was lost after 16 days. We then studied whether bisphosphonates could block this withdrawal effect. Mechanical and histomorphometric measurements were conducted for five weeks after implantation. Subcutaneous injections were given daily. Specimens treated with either PTH or saline during the first two weeks showed no difference in the mechanical or histological results (pull-out force 76 N vs 81 N; bone volume density 19% vs 20%). Treatment with PTH for two weeks followed by pamidronate almost doubled the pull-out force (152 N; p < 0.001) and the bone volume density (37%; ANOVA, p < 0.001). Pamidronate alone did not have this effect (89 N and 25%, respectively). Thus, the deterioration can be blocked by bisphosphonates. The clinical implications are discussed.

Additive effects of PTH and bisphosphonates on the bone healing response to metaphyseal implants in rats

BACKGROUND

When PTH is used to increase the amount of bone in osteoporotic patients, combination with bisphosphonates is known to attenuate the response. This might be explained by the reduced number of remodeling sites after bisphosphonate treatment, which reduces the number of cells able to respond to PTH. However, in a repair situation after trauma, a large number of osteoblasts reside in the wound site. If their activity is no longer coupled to osteoclasts, decreased resorption by bisphosphonates and stimulation of osteoblastic activity by PTH should both (independently) increase bone formation. Thus, we hypothesized that in contrast to the case in osteoporosis treatment, PTH and bisphosphonates have an additive effect in situations involving bone regeneration.

MATERIAL AND METHODS

Stainless steel screws, either coated with biphosphonates or uncoated, were inserted in 46 rat tibias. This normally elicits a bone repair response, leading to a gradual increase in the strength of screw fixation. Half of the rats also received daily injections of teriparatide (PTH). Thus, there were 4 groups: control, bisphosphonate, PTH, and bisphosphonate plus PTH. Pull-out force and energy were measured after 2 weeks.

RESULTS

The combined treatment had the strongest effect. It doubled the pull-out force and tripled the pull-out energy, compared to untreated controls. Also, bisphosphonate or PTH alone increased the pull-out force and energy, although less. No treatment cross-dependency was observed.

INTERPRETATION

Because bisphosphonates mainly influence osteoclasts, and intermittent administration of PTH mainly influences osteoblasts, our findings indicate that to a large extent these cells work without coupling in this model. It appears that bisphosphonates are unlikely to attenuate the response to PTH during the formation of new bone.

Critical issues in translational and clinical research for the study of new technologies to enhance bone repair

Osteoporosis increases fracture risk, especially in metaphyseal bone. Fractures seriously impair function and quality of life and incur large direct and indirect costs. Although the prevention of fractures is certainly the option, a fast and uneventful healing process is optimal when fractures do occur. Many new therapeutic strategies have been developed to accelerate fracture-healing or to diminish the complication rate during the course of fracture-healing. However, widely accepted guidelines are needed to demonstrate the positive or negative interactions of bioactive substances, drugs, and other agents that are being used to promote fracture-healing. For each study design, the primary study goal should be indicated. Outcome variables should include both objective and subjective parameters. The guidelines should be harmonized between European and American regulatory authorities to ensure comparability of results of studies and to foster global harmonization of regulatory requirements.

Critical analysis of the evidence for current technologies in bone-healing and repair

Substances that enhance fracture-healing and bone regeneration have valuable clinical application and merit future research. Advances in these technologies will enhance our ability to heal fractures in a more effective and expedient manner. This review provides a brief description of the different techniques and technologies and their respective clinical utility. This paper also reviews the available literature on gene therapy, tissue engineering, growth factors, osteoconductive agents, and physical forces and assesses the evidence regarding the current status of these techniques of healing and regenerating bone. Only twenty-seven articles met our guidelines for studies containing Level-I evidence. We were able to determine that atrophic nonunions and pseudarthrosis led to poorer outcomes, and the results were uniformly poor irrespective of the technique used. Although the literature contains a large number of studies on the effects of different agents and modalities on bone repair and healing, it still is not clear how these agents work or in what circumstances they should be used. Many of the treatment modalities of interest are still at an experimental stage, so good evidence to support clinical practice is lacking. Additional multicenter, prospective randomized studies are needed to define the indications, specifications, dosage, limitations, and contraindications in the treatment of nonunions. Studies are also needed to address the full clinical feasibility of the role of each modality in fracture-healing and repair.

Local peroperative treatment with a bisphosphonate improves the fixation of total knee prostheses: a randomized, double-blind radiostereometric study of 50 patients

BACKGROUND

Postoperative migration of a joint prosthesis is related to the risk of late loosening. We have previously reported that oral treatment with clodronate reduced migration of the cemented NexGen total knee prosthesis during the first postoperative year, as measured by radiostereometry (RSA). Oral bisphosphonate treatment is sometimes unpleasant, and local treatment will enable higher local concentrations. We now report the results of local peroperative treatment with another bisphosphonate, ibandronate, with the same prosthesis.

METHODS

This is a double-blind, randomized study of 50 patients using RSA with maximal total point motion (MTPM) as primary effect variable. 1 mg ibandronate (1 mL) or 1 mL saline was applied to the tibial bone surface 1 min before cementation. RSA examination was done on the first postoperative day, and at 6, 12, and 24 months.

RESULTS

One ibandronate-treated patient died of unrelated causes, and 1 control patient refused to come for follow-up, leaving 24 patients in each group for analysis. There were no cases of aseptic loosening. By repeated measures ANOVA, migration (MTPM) was reduced by local application of ibandronate (p=0.006). The effect was most pronounced at 6 months, with a reduction from 0.45 to 0.32 mm (95% CI for reduction: 0.04-0.21 mm). At 12 months, the migration from the postoperative examination was reduced from 0.47 to 0.36 mm (95% CI for reduction: 0.02-0.20 mm). At 24 months, the reduction was from 0.47 to 0.40 mm (95% CI: -0.01-0.16 mm).

INTERPRETATION

This is the first study to show improvement of prosthesis fixation by local pharmacological treatment in humans. The treatment appears to be safe, cheap, and easy to perform. However, the improvement in postoperative stability was not greater than with systemic clodronate treatment.

Defective implant osseointegration under protein undernutrition: prevention by PTH or pamidronate

Protein deficiency is associated with impaired titanium osseointegration. We studied whether systemic treatment with PTH or pamidronate could influence the resistance to pull-out of titanium rods implanted into rats proximal tibia under normal and isocaloric low protein intake. PTH or pamidronate prevented the deleterious effects of protein undernutrition on bone microarchitecture close to the implant and on mechanical fixation. PTH even significantly improved implant osseointegration.

INTRODUCTION

Protein deficiency is highly prevalent among elderly patients hospitalized in orthopedic wards. Reduced protein intake impairs titanium osseointegration in rats. Whether stimulator of bone formation or inhibitor of bone resorption could improve implant osseointegration under protein deprivation is not known. We studied the effects of systemic treatment with PTH or pamidronate on the resistance to pull-out of titanium rods implanted into rats proximal tibia under normal and isocaloric low protein intake.

MATERIALS AND METHODS

We measured the resistance to pull-out 1-mm-diameter titanium rods implanted into the proximal tibias of 49 adult female rats receiving a normal or an isocaloric low protein diet. After 2 wk on either diet, the implants were inserted, and the rats received PTH(1-34), pamidronate or saline vehicle for 8 wk. The tibias were removed for microCT morphometry, followed by the evaluation of pull-out strength.

RESULTS

Pull-out strength was lower in rats fed an isocaloric low protein diet compared with rats fed a normal protein intake (-29%). PTH and pamidronate significantly increased pull-out strength in animals fed a normal or a low protein diet, the effect of PTH being of higher magnitude. The PTH- or pamidronate-mediated increase in pull-out strength was associated with significant increases of relative bone volume, bone-to-implant contact, and trabecular thickness, whereas trabecular spacing was reduced, in the vicinity of the implants.

CONCLUSIONS

We confirmed that isocaloric low protein intake impairs titanium implant osseointegration. PTH or pamidronate prevented the deleterious effects of protein undernutrition and even significantly improved the implant osseointegration. These results indicate that systemic administration of PTH or pamidronate could be considered for preventing uncemented arthroplasty loosening in protein undernourished patients.

Metabolic and endocrine abnormalities in patients with nonunions

OBJECTIVES

To determine whether patients with unexplained nonunions, patients with a history of multiple low-energy fractures with at least one progressing to a nonunion, and patients with a nonunion of a nondisplaced pubic rami or sacral ala fracture would have an underlying metabolic or endocrine abnormality that had not been previously diagnosed.

DESIGN

Case series.

SETTING

Tertiary referral center.

PATIENTS AND INTERVENTION

From a larger series of 683 consecutive patients with nonunion seen by us between January 1998 and December 2005, 37 patients were referred to 1 of 2 clinically practicing endocrinologists to undergo an evaluation for metabolic and endocrine abnormalities. The screening criteria were: 1) an unexplained nonunion that occurred despite adequate reduction and stabilization (and debridement in initially infected cases) without obvious technical error and without any other obvious etiology; 2) a history of multiple low-energy fractures with at least one progressing to a nonunion; or 3) a nonunion of a nondisplaced pubic rami or sacral ala fracture.

RESULTS

In all, 31 of the 37 patients (83.8%, 95% CI: 71.3% to 93.8%) who met our screening criteria had one or more new diagnoses of metabolic or endocrine abnormalities. The most common newly diagnosed abnormality was vitamin D deficiency (25 of 37 patients; 68%). Other newly diagnosed abnormalities included calcium imbalances, central hypogonadism, thyroid disorders, and parathyroid hormone disorders. All newly diagnosed abnormalities were treated medically. Eight patients who underwent no operative intervention following the diagnosis and treatment of a new metabolic or endocrine abnormality achieved bony union in an average of 7.6 months (range, 3 to 12 months) following their first visit to the endocrinologist.

CONCLUSIONS

Although our study does not prove a causal link between metabolic and endocrine abnormalities and either the development or healing of nonunions, 84% of the patients who met our screening criteria were found to have metabolic or endocrine abnormalities, and eight of our patients achieved bony union following medical treatment alone. All patients with nonunion who meet our screening criteria should be referred to an endocrinologist for evaluation because they are likely to have undiagnosed metabolic or endocrine abnormalities that may be interfering with bone healing.

Pharmacologic agents in fracture healing

Bone fractures are a known risk of athletic participation and can result in significant lost playing time. A variety of medications have been investigated in animal studies regarding their effects on fracture healing. Parathyroid hormone and the bisphosphonates may have future uses in the prevention and treatment of athletic-related stress fractures and acute fractures. Nonsteroidal anti-inflammatory drugs have been implicated in effecting fracture healing in some animal models, but little clinical evidence supports these findings. Large randomized clinical trials are needed to further delineate the role of these and other drugs and their effects on fracture healing.