Remodeling potentials of biphasic calcium phosphate granules in open wedge high tibial osteotomy

Improvement of absorbability, osteoconductivity, and strength of a β-tricalcium phosphate spacer for opening wedge high tibial osteotomy: clinical evaluations with 106 patients

BACKGROUND

An ideal synthetic spacer for medial opening wedge high tibial osteotomy (MOWHTO) has not yet been developed. The authors have developed a new β-tricalcium phosphate (β-TCP) spacer with 60% porosity (N-CP60) by modifying the micro- and macro-pore structures of a conventional β-TCP spacer (CP60) that is widely used in clinical practice. The purpose of this study was to compare the absorbability, osteoconductivity, and in vivo strength of the N-CP60 spacer with those of the CP60 spacer, when used in MOWHTO.

METHODS

First, the porosity, diameter distribution of macro- and micropores, and compressive strength of each β-TCP block were examined using methodology of biomaterial science. Secondly, a clinical study was performed using a total of 106 patients (106 knees) with MOWHTO, who were followed up for 18 months after surgery. In these knees, the N-CP60 and CP-60 spacers were implanted into 49 tibias and 57 tibias, respectively. The absorbability and osteoconductivity were radiologically evaluated by measuring the area of the implanted spacer remaining unabsorbed and assessing with the Hemert's score, respectively. The incidence of cracking in the implanted spacers was determined using computed radiography. Statistical comparisons were made with non-parametric tests. The significance level was set at p = 0.05.

RESULTS

The N-CP60 and CP60 blocks had almost the same porosity (mean, 61.0% and 58.7%, respectively). The diameter of macropores was significantly larger (p < 0.0001) in the N-CP60 block than in the CP60 block, while the diameter of micropores was significantly smaller (p = 0.019) in the N-CP60 block. The ultimate strength of the N-CP60 block (median, 36.8 MPa) was significantly greater (p < 0.01) than that of the CP60 block (31.6 MPa). As for the clinical evaluations, the absorption rate of the N-CP60 spacer at 18 months after implantation (mean, 48.0%) was significantly greater (p < 0.001) than that of the CP60 spacer (29.0%). The osteoconductivity of the N-CP60 spacer was slightly but significantly higher (p = 0.0408) than that of the CP60 spacer only in zone 1. The incidence of in vivo cracking of the posteriorly located N-CP60 spacer at one month (mean, 75.5%) was significantly lower (p = 0.0035) than that of the CP60 spacer (91.2%).

CONCLUSIONS

The absorbability, osteoconductivity, and compressive strength of the new N-CP60 spacer were significantly improved by modifying the macro- and micro-pore structures, compared with the conventional CP60 spacer. The N-CP60 spacer is more clinically useful than the CP60 spacer.

TRIAL REGISTRATION NUMBER

H29-0002.

Use of biphasic calcium phosphate versus demineralized bone matrix: retrospective clinical and CT analysis of posterolateral fusion results

PURPOSE

Bone graft extenders have been developed to prevent donor site morbidity associated with iliac crest bone graft, but few studies compared the efficacy of various substitutes. Our purpose was to determine fusion rate and clinical outcome in patients undergoing lumbar arthrodesis using demineralized bone matrix (DBM) and biphasic calcium phosphate (BCP).

METHODS

Patients with degenerative spondylolisthesis undergoing one-level or two-level arthrodesis of lumbar spine were retrospectively reviewed. Two treatment groups placed either BCP or DBM, in addition to local autograft in lumbar posterolateral space. Three-dimensional CT exam and dynamic flexion-extension radiographs at postoperative 2-year were assessed for posterolateral fusion status and pain scale and Oswestry Disability Index (ODI) for clinical outcome.

RESULTS

Of the 148 patients reviewed (including 23 in one- and 58 patients in two-level in BCP group, and 47 in one- and 20 patients in two-level in DBM group), no significant differences were found in terms of age, sex, BMI, smoking, diabetes, steroids, number of level fused, non-union rate or revision surgery between BCP and DBM groups. Significantly improved pain scale of back and leg and ODI were found in both groups postoperatively without group difference. We found a comparable fusion rate in one-level surgery (100% versus 93.6%) and a superior fusion rate of BCP group in two-level surgery (98.3% versus 80.0%, p = 0.01).

CONCLUSION

Being a bone graft extender without osteoinductive property, with local autograft, BCP is comparable to DBM for one- and superior for two-level fusion. No significant difference was found in clinical outcomes.

Effectiveness of bone substitute materials in opening wedge high tibial osteotomy: a systematic review and meta-analysis

BACKGROUND

A meta-analysis of eligible studies was performed to evaluate the effectiveness of bone substitute materials (BSMs) in opening wedge high tibial osteotomy (OWHTO) for knee osteoarthritis.

METHODS

A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). A comprehensive literature search was performed, and studies comparing BSM with bone graft (BG) and without bone graft (WG) were included. The Cochrane risk of bias tool (version 1.0) and Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool were used to assess the risk of bias for randomized controlled trials (RCTs) and non-randomized studies (NRSs), respectively. The outcomes measured were the osteotomy gap size, the occurrence rates of non-union and lateral hinge fractures, knee functional score, infection and the Visual Analogue Scale (VAS). The quality of evidences was evaluated by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) Working Group system.

RESULTS

Five RCTs and eight NRS including 769 participants were included in our meta-analysis. The BSM group had a larger osteotomy gap size than the control group (MD: 0.41 mm, 95% confidence interval (CI): [0.06, 0.76], p=.02, I2=0%), with a significant difference. No significant difference was found between BSM and control group in main analysis in terms of bone non-union, but with a higher non-union rate when BSM combined with long locking plate was used. No significant differences were found in other outcome measures except for VAS from NRS subgroup. The quality of evidence for outcomes was low.

CONCLUSIONS

BSM combined with locking plate techniques offers a safe and efficient alternative option in OWHTO for osteotomy gap larger than 10 mm, but be aware of the possibility of bone non-union. Given the inherent heterogeneity and low quality of the included studies, future well-designed RCTs are essential to verify the findings.KEY MESSAGEThe treatment of the osteotomy gap is still controversial.BSM combined with a locking plate offers a safe and efficient alternative option for OWHTO with an over 10 mm of osteotomy gap over 10 mm.Due to the inherent heterogeneity and low quality of the included studies, the results should be cautiously interpreted in clinical practice.

Core-Shell Structured Porous Calcium Phosphate Bioceramic Spheres for Enhanced Bone Regeneration

Adequate new bone regeneration in bone defects has always been a challenge as it requires excellent and efficient osteogenesis. Calcium phosphate (CaP) bioceramics, including hydroxyapatite (HA) and biphasic calcium phosphates (BCPs), have been extensively used in clinical bone defect filling due to their good osteoinductivity and biodegradability. Here, for the first time, we designed and fabricated two porous CaP bioceramic granules with core-shell structures, named in accordance with their composition as BCP@HA and HA@BCP (core@shell). The spherical shape and the porous structure of these granules were achieved by the calcium alginate gel molding technology combined with a H₂O₂ foaming process. These granules could be stacked to build a porous structure with a porosity of 65-70% and a micropore size distribution between 150 and 450 μm, which is reported to be good for new bone ingrowth. In vitro experiments confirmed that HA@BCP bioceramic granules could promote the proliferation and osteogenic ability when cocultured with bone marrow mesenchymal stem cells, while inhibiting the differentiation of RAW264.7 cells into osteoclasts. In vivo, 12 weeks of implantation in a critical-sized femoral bone defect animal model showed a higher bone volume fraction and bone mineral density in the HA@BCP group than in the BCP@HA or pure HA or BCP groups. From histological analysis, we discovered that the new bone tissue in the HA@BCP group was invading from the surface to the inside of the granules, and most of the bioceramic phase was replaced by the new bone. A higher degree of vascularization at the defect region repaired by HA@BCP was revealed by 3D microvascular perfusion angiography in terms of a higher vessel volume fraction. The current study demonstrated that the core-shell structured HA@BCP bioceramic granules could be a promising candidate for bone defect repair.

Comparative Analysis of Serial Union Patterns After Opening-Wedge High Tibial Osteotomy with and without Bone-Void Fillers

BACKGROUND

Opening-wedge high tibial osteotomy produces opening gaps; however, there is little consensus on bone graft necessity and the material that would produce a superior union. The purposes of the present study were (1) to compare the serial union patterns associated with various bone-void fillers, (2) to determine whether bone-void filler is necessary to achieve bone union of the opening gap, and (3) to determine whether bone union is different according to the correction degree during opening-wedge high tibial osteotomy.

METHODS

In this retrospective study, 97 knees were randomly assigned to treatment with hydroxyapatite chip bone (Group A), allogenic chip bone (Group B), or no bone graft (Group C) and were analyzed after a minimum 1-year follow-up. To compare the bone union pattern, the area of callus filling located at the most medial side on an anteroposterior radiograph of the knee was recorded, and a modified van Hemert scoring system was used in the mediolaterally divided 5 zones. The correlations between the correction degree and bone union scores were evaluated.

RESULTS

There were no significant differences in the extent of mediolateral bone-healing at 6 weeks or 3 months postoperatively (p = 0.172 and p = 0.228). However, Group C showed more prominent progression of the gap filling to the medial side compared with Groups A and B at 6 months postoperatively (p = 0.002). Group C showed slow progression of bone union up to 6 weeks but surpassed the other groups at 6 months. The union pattern was not different between Groups A and B, and the correction degree was not correlated with bone union beyond 3 months postoperatively.

CONCLUSIONS

Despite the different gap-healing patterns, opening-wedge high tibial osteotomy without bone graft achieved bone union comparable with allogenic and synthetic graft materials. Group C (no bone graft) showed slower progression of bone union but surpassed the other groups at around 6 months. Based on the union pattern, there was no difference depending on the correction degree and the use of bone-void fillers.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Faster bone union progression and less sclerosis at the osteotomy margin after medial opening-wedge high tibial osteotomy using highly porous β-tricalcium phosphate granules versus allogeneic bone chips: A matched case-control study

BACKGROUND

This study compared bone union progression using highly porous (80% porosity) β-tricalcium phosphate (β-TCP) granules or allogeneic bone chips in the gap created by medial opening-wedge high tibial osteotomy (MOWHTO).

METHODS

The study population consisted of 54 patients who received MOWHTO with locking plate fixation: 27 patients using highly porous β-TCP granules, and 27 age- and sex-matched patients using allogeneic bone chips. Bone union progression was evaluated 1, 3, 6, and 12 months postoperatively. The presence of radiographic sclerosis at the osteotomy margin was also assessed.

RESULTS

Among all patients, the highest degree of bone union observed 12 months postoperatively was grade 4. As postoperative time passed, bone union progression of highly porous β-TCP granules increased linearly and was statistically significant compared with that of cancellous allogeneic bone chips (P = 0.014). The presence of radiographic sclerosis at the osteotomy margin was significantly less common in the β-TCP group than in the allograft group (P = 0.003) and was the strongest predictor of delayed progress of bone union (odds ratio = 6.16, P = 0.006).

CONCLUSIONS

Patients who underwent MOWHTO using highly porous β-TCP granules had faster new bone remodeling, less radiographic sclerosis at the osteotomy margin, and no inferior clinical outcome compared with allogeneic bone chips, as determined at the 1-year follow up. The presence of radiographic sclerosis at the osteotomy margin in patients undergoing MOWHTO using allogeneic bone or synthetic bone substitute may indicate delayed progress of bone union.

Mid-term CT assessment of bone healing after nanohydroxyapatite augmentation in open-wedge high tibial osteotomy

BACKGROUND

The aim of the present study was to confirm the effectiveness of adding nanohydroxyapatite (NHA) to a heterologous bone graft in open-wedge high tibial osteotomy (OWHTO) by measuring the bone density via multislice computed tomography (CT) of the tibial osteotomy gap in a mid-term follow-up (five years).

METHODS

Twenty-six patients undergoing OWHTO were randomly assigned to two groups: a pure graft group (Group A), in which the osteotomy gap was filled with only heterologous bone graft, and an NHA group (Group B), in which the osteotomy gap was filled with heterologous bone graft and NHA. CT was performed within one week of the operation, after two months, after 12 months and after five years. CT volume acquired in Hounsfield units (HU) was measured on three planes.

RESULTS

The normal bone density was 110.2 ± 11.7 HU. The value of mean density at five years in Group A was 296.8 ± 81.8 HU, while in Group B, it was 202.2 ± 45.1 HU, showing a density more similar to normal bone and greater bone uniformity inside the osteotomy. The difference between the two groups was statistically significant (p < 0.05). Furthermore, both groups showed excellent mid-term clinical outcomes without significant differences.

CONCLUSIONS

This study revealed that absorbability and bone formation at the osteotomy site in the NHA group was significantly higher as compared with the pure graft group at five years postoperatively.

The outcome of biphasic calcium phosphate bone substitute in a medial opening wedge high tibial osteotomy

BACKGROUND

Our objective was to assess clinical and radiological findings following a medial opening wedge high tibial osteotomy using a biphasic calcium phosphate (BCP) synthetic bone substitute, designed as a wedge with two differing zones of density. The in-vivo behaviour of this type of bone substitute over time is currently unknown.

HYPOTHESIS

Our hypothesis was that BCP synthetic bone would facilitate bone union and undergo replacement with host bone over the study period.

PATIENTS AND METHODS

Fifteen sequential patients were followed prospectively for minimum 4-years post-operatively. All patients were evaluated clinically using patient reported outcome measures and radiologically to evaluate alignment with maintenance of the osteotomy correction, and bone union with expected BCP dissolution.

RESULTS

All patients had good clinical scores with no reported complications at 4 years. In all cases there were radiographic findings of bone union with consolidation and no loss of correction. However the graft remained densely radiopaque at final follow-up.

DISCUSSIONS

This study demonstrates that a BCP graft in combination with a locking plate for a medial opening wedge HTO allows early weight-bearing, maintains correction and provides good clinical outcomes. Whilst higher densities of BCP are strong, they do not resorb fully, remaining radiographically visible. This may have implications for the performance of a future knee arthroplasty and caution should therefore be taken.

Lateral hinge fracture delays healing of the osteotomy gap in opening wedge high tibial osteotomy with a beta-tricalcium phosphate block

BACKGROUND

The purpose of this study was to investigate the healing process of synthetic bone grafts in opening wedge high tibial osteotomy (OWHTO) and to identify the factors that affect bone healing in OWHTO. It was hypothesized that lateral hinge fracture (LHF) is associated with delayed bone healing after OWHTO with synthetic bone grafting.

METHODS

The subjects included 350 knees of 283 patients who underwent OWHTO using two wedged blocks of beta-tricalcium phosphate (β-TCP) with 60% porosity. The healing of the osteotomy gap using a radiologic rating system for OWHTO with synthetic bone grafts and the presence of an LHF were assessed up to postoperative 24 months.

RESULTS

LHFs were found in 49 knees (14%). The osteotomy gap showed slower progression of radiographic healing with an LHF than without an LHF (P < .05). In the knees with LHFs, initial radiographic change in the osteotomy gap was observed almost at the same time as healing of the LHF. Multivariate logistic regression analysis identified LHF as the factor preventing the progression of bone healing (OR = 46.78, P < .05).

CONCLUSIONS

LHF is associated with delayed bone healing after OWHTO with synthetic bone grafting.

Comparable bone union progression after opening wedge high tibial osteotomy using allogenous bone chip or tri-calcium phosphate granule: a prospective randomized controlled trial

PURPOSE

The purpose of this study is to compare the progression rate of bone union and clinical outcomes of opening wedge high tibial osteotomy (OWHTO) using allogenous bone chip or tri-calcium phosphate (TCP) granule as bone graft materials. The hypothesis was that the bone union progression in OWHTOs using TCP granule grafts would be comparable to that of OWHTOs using allogenous bone chip grafts.

METHODS

Between 2011 and 2013, 54 patients who had undergone OWHTO for genu varum and osteoarthritis were randomized to one of the two groups at five centres. TCP granule was used to fill the defect in 27 patients and lyophilized allogenous bone chip was used in the other 27 patients. The degree of bone union was classified on a five-point scale and evaluated using plain radiographs of the knee at 6 weeks, 3 months, 6 months, and 12 months postoperatively. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, pain Visual Analogue Scale (VAS) score and complications were also evaluated.

RESULTS

The highest degree of bone union observed at 6 and 12 months postoperatively was grade 4, and the number of cases of union progression at each time-point was not significantly different between the two groups (p > 0.05). WOMAC and pain VAS scores also showed no differences between the two groups. No complications were observed during the 12-month period following OWHTO in either group.

CONCLUSION

OWHTO using TCP granule bone substitute showed similar bone union rates and clinical outcomes compared to allogenous bone chip grafts. TCP granule can be used as bone substitutes instead of allogenous bone chip grafts in OWHTO.

LEVEL OF EVIDENCE

Level 1.

Honeycomb blocks composed of carbonate apatite, β-tricalcium phosphate, and hydroxyapatite for bone regeneration: effects of composition on biological responses

Synthetic scaffolds exhibiting bone repair ability equal to that of autogenous bone are required in the fields of orthopedics and dentistry. A suitable synthetic bone graft substitute should induce osteogenic differentiation of mesenchymal stem cells, osteogenesis, and angiogenesis. In this study, three types of honeycomb blocks (HCBs), composed of hydroxyapatite (HAp), β-tricalcium phosphate (TCP), and carbonate apatite (CO3Ap), were fabricated, and the effects of HCB composition on bone formation and maturation were investigated. The HC structure was selected to promote cell penetration and tissue ingrowth. HAp and β-TCP HCBs were fabricated by extrusion molding followed by sintering. The CO3Ap HCBs were fabricated by extrusion molding followed by sintering and dissolution-precipitation reactions. These HCBs had similar macroporous structures: all harbored uniformly distributed macropores (∼160 ​μm) that were regularly arrayed and penetrated the blocks unidirectionally. Moreover, the volumes of macropores were nearly equal (∼0.15 ​cm3/g). The compressive strengths of CO3Ap, HAp, and β-TCP HCBs were 22.8 ​± ​3.5, 34.2 ​± ​3.3, and 24.4 ​± ​2.4 ​MPa, respectively. Owing to the honeycomb-type macroporous structure, the compressive strengths of these HCBs were higher than those of commercial scaffolds with intricate three-dimensional or unidirectional macroporous structure. Notably, bone maturation was markedly faster in CO3Ap HCB grafting than in β-TCP and HAp HCB grafting, and the mature bone area percentages for CO3Ap HCBs at postsurgery weeks 4 and 12 were 14.3- and 4.3-fold higher and 7.5- and 1.4-fold higher than those for HAp and β-TCP HCBs, respectively. The differences in bone maturation and formation were probably caused by the disparity in concentrations of calcium ions surrounding the HCBs, which were dictated by the inherent material resorption behavior and mechanism; generally, CO3Ap is resorbed only by osteoclastic resorption, HAp is not resorbed, and β-TCP is rapidly dissolved even in the absence of osteoclasts. Besides the composition, the microporous structure of HC struts, inevitably generated during the formation of HCBs of various compositions, may contribute to the differences in bone maturation and formation.

Graft materials provide greater static strength to medial opening wedge high tibial osteotomy than when no graft is included

Background

The purpose of this study was to compare the stability of medial opening-wedge high tibial osteotomy (MOWHTO) with and without different graft materials. Good clinical and radiological outcomes have been demonstrated when either using or not using graft materials during MOWHTO. Variations in the biomechanical properties of different graft types, regarding the stability they provide a MOWHTO, have not been previously investigated.

Methods

A 10 mm biplanar MOWHTO was performed on 15 artificial sawbone tibiae, which were fixed using the Activmotion 2 plate. Five bones had OSferion60 wedges (synthetic group), five had allograft bone wedges (allograft group), and five had no wedges (control group) inserted into the osteotomy gap. Static compression was applied axially to each specimen until failure of the osteotomy. Ultimate load, horizontal and vertical displacements were measured and used to calculate construct stiffness and valgus malrotation of the tibial head.

Results

The synthetic group failed at 6.3 kN, followed by the allograft group (6 kN), and the control group (4.5 kN). The most valgus malrotation of the tibial head was observed in the allograft group (2.6°). The synthetic group showed the highest stiffness at the medial side of the tibial head (9.54 kN·mm^− 1), but the lowest stiffness at the lateral side (1.59 kN·mm^-1). The allograft group showed high stiffness on the medial side of the tibial head (7.54 kN·mm^− 1) as well as the highest stiffness on the lateral side (2.18 kN·mm^− 1).

Conclusions

The use of graft materials in MOWHTO results in superior material properties compared to the use of no graft. The static strength of MOWHTO is highest when synthetic grafts are inserted into the osteotomy gap. Allograft wedges provide higher mechanical strength to a MOWHTO than when no graft used. In comparison to the synthetic grafts, allograft wedges result in the stiffness of the osteotomy being more similar at the medial and lateral cortices.

A Retrospective Comparison of Union Rates After Open Wedge High Tibial Osteotomies With and Without Synthetic Bone Grafts (Hydroxyapatite and β-tricalciumphosphate) at 2 Years

PURPOSE

To evaluate the clinical and radiological results of no bone graft (NBG) after opening wedge high tibial osteotomy (OWHTO) with a locking plate and to compare the bone union rate between the synthetic bone graft (SBG) group and the NBG group after OWHTO using serial radiographs.

METHODS

From 2012 to 2015, OWHTOs were performed with SBG or without bone graft using long locking plates. Inclusion criteria were: (1) OWHTO for disease of the medial compartment with varus deformity, and (2) minimum 2-year follow-up and radiographs taken serially to 2 years. Exclusion criteria were: (1) follow-up period <2 years (n = 8) or (2) absence of at least 1 radiograph taken at each follow-up point (n = 14). We retrospectively reviewed radiographs taken preoperatively and at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperatively. Groups comprised those filled with a synthetic bone [hydroxyapatite (HA) and β-tricalciumphosphate (TCP), n=33, SBG group] or without a bone graft (n = 38, NBG group). We compared bone union rate between the 2 groups by measuring the union zone from zone 1 to zone 5 in serial radiographs using Fisher's exact test.

RESULTS

OWHTO was performed in a total of 93 knees and 71 knees were included in this study. Both groups showed good clinical and radiological results without correction loss at 2 years. The entire NBG group and 93.9% of the SBG group showed union over zone 3 at 2 years. However, the NBG group showed significantly more incorporation than the SBG group at 6 months (P = .006), 1 year (P = .0003), and 2 years (P = .0003).

CONCLUSIONS

Union without correction loss was obtained after OWHTO without bone graft. The NBG group showed significantly more incorporation than the SBG group (HA and β-TCP) within 2 years.

LEVEL OF EVIDENCE

Level IV, case series.

Mesenchymal stem cells and porous β-tricalcium phosphate composites prepared through stem cell screen-enrich-combine(-biomaterials) circulating system for the repair of critical size bone defects in goat tibia

BACKGROUND

Efficacious bone substitute is essential for the treatment of a critical size bone defect. Currently, the bone substitutes commonly used in clinical practice lack osteogenic capacity and the therapeutic efficacy is not ideal. Herein, a novel stem cell screen-enrich-combine(-biomaterials) circulating system (SECCS) was introduced to provide the substitutes with osteogenic ability. The stem cell screening, enrichment, and recombination with substitutes could be integrated during the surgical operation. Using SECCS, the bioactive mesenchymal stem cells (MSCs) and porous β-tricalcium phosphate (β-TCP) composites (MSCs/β-TCP) were rapidly prepared for critical size bone defect repair and validated in goat models of critical size tibia defects.

METHODS

Twelve goats with right hind limb tibia defects of 30 mm were randomly divided into two groups: six (the experimental group) were treated with MSCs/β-TCP prepared by SECCS and the other six goats (the control group) were treated with pure porous β-TCP. The repair effect was assessed by x-ray, computed tomography (CT), micro-CT, histology and histomorphology 6 months after the operation. In addition, the enrichment efficacy of MSCs and the characteristics of the MSCs/β-TCP prepared by SECCS were evaluated.

RESULTS

The SECCS could compound about 81.3 ± 3.0% of the MSCs in bone marrow to the porous β-TCP without affecting the cell viability. The average number of MSCs for retransplantation was 27,655.0 ± 5011.6 for each goat from the experimental group. In vitro, satisfactory biocompatibility of the MSCs/β-TCP was performed, with the MSCs spreading adequately, proliferating actively, and retaining the osteogenic potential. In vivo, the defect repair by MSCs/β-TCP with good medullary cavity recanalization and cortical remodeling was significantly superior to that of pure porous β-TCP.

CONCLUSIONS

The MSCs/β-TCP prepared through SECCS demonstrated significant therapeutic efficacy in goat models of critical size bone defect. This provides a novel therapeutic strategy for critical size bone defects caused by severe injury, infection, and bone tumor resection with a high profile of safety, effectiveness, simplicity, and ease.

Gap healing after medial open-wedge high tibial osteotomy using injectable beta-tricalcium phosphate

PURPOSE

The study aim was to evaluate gap healing after medial open-wedge high tibial osteotomy (MOWHTO) using novel injectable beta-tricalcium phosphate (β-TCP) as gap filler. We also aimed to evaluate radiographic and clinical outcome of MOWHTO using injectable β-TCP.

METHODS

Consecutive 28 patients underwent MOWHTO using anatomical locking plate fixation, and β-TCP was injected as gap filler. Serial radiographs and computed tomography were taken at postoperative 3 and 12 months, and gap healing was assessed. Lower extremity alignment was measured on radiographs, and clinical outcome was evaluated by determining International Knee Documentation Committee, Western Ontario and McMaster Universities Arthritis Index, and visual analogue scales for pain scores.

RESULTS

Progress of bone union was found on plain radiographs, and the mean ratio (β-TCP/host bone) of computed tomography attenuation values significantly changed from postoperative 3 months to 12 months, which indicates maturation of β-TCP. The average mechanical femoro-tibial angle changed from 4.1° varus (preoperative) to 4.8° valgus (3 months) and maintained until 12 months (4.3° valgus). All clinical outcome scores were significantly improved and no significant complication occurred.

CONCLUSION

Using injectable β-TCP as gap filler for MOWHTO resulted in satisfactory gap healing without complication. Radiographic and clinical results were satisfactory. The injectable β-TCP can be a safe and effective option for gap filling after MOWHTO.

Hydoxyapatite/beta-tricalcium phosphate biphasic ceramics as regenerative material for the repair of complex bone defects

Bone is a composite material composed of collagen and calcium phosphate (CaP) mineral. The collagen gives bone its flexibility while the inorganic material gives bone its resilience. The CaP in bone is similar in composition and structure to the mineral hydroxyapatite (HA) and is bioactive, osteoinductive and osteoconductive. Therefore synthetic versions of bone apatite (BA) have been developed to address the demand for autologous bone graft substitutes. Synthetic HA (s-HA) are stiff and strong, but brittle. These lack of physical attributes limit the use of synthetic apatites in situations where no physical loading of the apatite occurs. s-HA chemical properties differ from BA and thus change the physical and mechanical properties of the material. Consequently, s-HA is more chemically stable than BA and thus its resorption rate is slower than the rate of bone regeneration. One solution to this problem is to introduce a faster resorbing CaP, such as β-tricalcium phosphate (β-TCP), when synthesizing the material creating a biphasic (s-HA and β-TCP) formulation of calcium phosphate (BCP). The focus of this review is to introduce the major differences between BCP and biological apatites and how material scientists have overcome the inadequacies of the synthetic counterparts. Examples of BCP performance in vitro and in vivo following structural and chemical modifications are provided as well as novel ultrastructural data. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2493-2512, 2018.

ß-TCP bone substitutes in tibial plateau depression fractures

BACKGROUND

The use of beta-tricalciumphospate (ß-TCP, Cerasorb®) ceramics as an alternative for autologous bone-grafting has been outlined previously, however with no study focusing on both clinical and histological outcomes of ß-TCP application in patients with multi-fragment tibial plateau fractures. The aim of this study was to analyze the long-term results of ß-TCP in patients with tibial plateau fractures.

METHODS

52 patients were included in this study. All patients underwent open surgery with ß-TCP block or granulate application. After a mean follow-up of 36months (14-64months), the patients were reviewed. Radiography and computed-tomography were performed, while the Rasmussen score was obtained for clinical outcome. Furthermore, seven patients underwent biopsy during hardware removal, which was subsequently analyzed by histology and backscattered electron microscopy (BSEM).

RESULTS

An excellent reduction with two millimeters or less of residual incongruity was achieved in 83% of the patients. At follow-up, no further changes occurred and no nonunions were observed. Functional outcome was good to excellent in 82%. Four patients underwent revision surgery due to reasons unrelated to the bone substitute material. Histologic analyses indicated that new bone was built around the ß-TCP-grafts, however a complete resorption of ß-TCP was not observed.

DISCUSSION

ß-TCP combined with internal fixation represents an effective and safe treatment of tibial plateau depression fractures with good functional recovery. While its osteoconductivity seems to be successful, the biological degradation and replacement of ß-TCP is less pronounced in humans than previous animal studies have indicated.

Autologous Osteophyte Grafting for Open-Wedge High Tibial Osteotomy

Osteophytes are physiological bony outgrowths that develop at the margins of the articular surfaces during the progression of osteoarthritis; they are associated with active endochondral bone formation processes and expressions of various growth factors. We believe they could be a source of bone grafts as a result of a potentially strong osteoinductive effect. Moreover, osteophytes can be easily harvested by arthroscopy in patients undergoing open-wedge high tibial osteotomy (OW-HTO) for medial unicompartmental knee osteoarthritis. Therefore, we have been using osteophyte autografts for osteotomy gaps in OW-HTO with positive preliminary results indicating rapid bone healing of osteotomy sites. In this technical note, we introduce a technique for harvesting autologous osteophytes by arthroscopy and implanting them into the gap formed after OW-HTO. We expect that autologous osteophyte grafting can be a useful method for accelerating bone union and therefore enabling weight bearing from an early stage after surgery, which will lead to an early return to social activities.

Is Bone Grafting Necessary in Opening Wedge High Tibial Osteotomy? A Meta-Analysis of Radiological Outcomes

Purpose

Bone grafting in opening wedge high tibial osteotomy (OWHTO) is still controversial. The purpose of this study is to compare the radiological outcomes of OWHTO with bone graft (autogenous, allogenous, and synthetic bone graft) and those without bone graft.

Materials and Methods

PubMed, MEDLINE, EMBASE and Cochrane Register of Studies databases were searched using specific inclusion and exclusion criteria for radiological studies involving OWHTO with bone graft and without bone graft groups. All reported delayed union, nonunion and correction loss were analyzed. Data were searched from the time period of January 2000 through July 2014. In addition, a modified Coleman methodology score (CMS) system was used to assess the methodological quality of the included studies.

Results

Twenty-five studies with a mean CMS value of 77 (range, 61 to 85 score) were included. In total, 1,841 patients underwent OWHTO using 4 different procedures for bone graft: autobone graft (n=352), allobone graft (n=547), synthetic bone graft (n=541) and no bone graft (n=401). There was a similar tendency for delayed union, nonunion and correction loss rate among the osteotomy space filling methods.

Conclusions

The meta-analysis showed there was a similar tendency for radiological union and correction maintenance among patients undergoing OWHTO regardless of the type of bone in all of the studies. However, the currently available evidence is not sufficient to strongly support the superiority of OWHTO with bone graft to OWHTO without bone graft.

The Effect of Alendronate Loaded Biphasic Calcium Phosphate Scaffolds on Bone Regeneration in a Rat Tibial Defect Model

This study investigated the effect of alendronate (Aln) released from biphasic calcium phosphate (BCP) scaffolds. We evaluated the in vitro osteogenic differentiation of Aln/BCP scaffolds using MG-63 cells and the in vivo bone regenerative capability of Aln/BCP scaffolds using a rat tibial defect model with radiography, micro-computed tomography (CT), and histological examination. In vitro studies included the surface morphology of BCP and Aln-loaded BCP scaffolds visualized using field-emission scanning electron microscope, release kinetics of Aln from BCP scaffolds, alkaline phosphatase (ALP) activity, calcium deposition, and gene expression. The in vitro studies showed that sustained release of Aln from the BCP scaffolds consisted of porous microstructures, and revealed that MG-63 cells cultured on Aln-loaded BCP scaffolds showed significantly increased ALP activity, calcium deposition, and gene expression compared to cells cultured on BCP scaffolds. The in vivo studies using radiograph and histology examination revealed abundant callus formation and bone maturation at the site in the Aln/BCP groups compared to the control group. However, solid bony bridge formation was not observed at plain radiographs until 8 weeks. Micro-CT analysis revealed that bone mineral density and bone formation volume were increased over time in an Aln concentration-dependent manner. These results suggested that Aln/BCP scaffolds have the potential for controlling the release of Aln and enhance bone formation and mineralization.

Beta-tricalcium phosphate shows superior absorption rate and osteoconductivity compared to hydroxyapatite in open-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clinically and radiologically compare the utility, osteoconductivity, and absorbability of hydroxyapatite (HAp) and beta-tricalcium phosphate (TCP) spacers in medial open-wedge high tibial osteotomy (HTO).

METHODS

Thirty-eight patients underwent medial open-wedge HTO with a locking plate. In the first 19 knees, a HAp spacer was implanted in the opening space (HAp group). In the remaining 19 knees, a TCP spacer was implanted in the same manner (TCP group). All patients underwent clinical and radiological examinations before surgery and at 18 months after surgery.

RESULTS

Concerning the background factors, there were no statistical differences between the two groups. Post-operatively, the knee score significantly improved in each group. Concerning the post-operative knee alignment and clinical outcome, there was no statistical difference in each parameter between the two groups. Regarding the osteoconductivity, the modified van Hemert's score of the TCP group was significantly higher (p = 0.0009) than that of the HAp group in the most medial osteotomy zone. The absorption rate was significantly greater in the TCP group than in the HAp group (p = 0.00039).

CONCLUSIONS

The present study demonstrated that a TCP spacer was significantly superior to a HAp spacer concerning osteoconductivity and absorbability at 18 months after medial open-wedge HTO.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Scaffold-based regeneration of skeletal tissues to meet clinical challenges

The management and reconstruction of damaged or diseased skeletal tissues have remained a significant global healthcare challenge. The limited efficacy of conventional treatment strategies for large bone, cartilage and osteochondral defects has inspired the development of scaffold-based tissue engineering solutions, with the aim of achieving complete biological and functional restoration of the affected tissue in the presence of a supporting matrix. Nevertheless, significant regulatory hurdles have rendered the clinical translation of novel scaffold designs to be an inefficient process, mainly due to the difficulties of arriving at a simple, reproducible and effective solution that does not rely on the incorporation of cells and/or bioactive molecules. In the context of the current clinical situation and recent research advances, this review will discuss scaffold-based strategies for the regeneration of skeletal tissues, with focus on the contribution of bioactive ceramic scaffolds and silk fibroin, and combinations thereof, towards the development of clinically viable solutions.

Biphasic, triphasic and multiphasic calcium orthophosphates

Biphasic, triphasic and multiphasic (polyphasic) calcium orthophosphates have been sought as biomaterials for reconstruction of bone defects in maxillofacial, dental and orthopedic applications. In general, this concept is determined by advantageous balances of more stable (frequently hydroxyapatite) and more resorbable (typically tricalcium orthophosphates) phases of calcium orthophosphates, while the optimum ratios depend on the particular applications. Therefore, all currently known biphasic, triphasic and multiphasic formulations of calcium orthophosphate bioceramics are sparingly soluble in water and, thus, after being implanted they are gradually resorbed inside the body, releasing calcium and orthophosphate ions into the biological medium and, hence, seeding new bone formation. The available formulations have already demonstrated proven biocompatibility, osteoconductivity, safety and predictability in vitro, in vivo, as well as in clinical models. More recently, in vitro and in vivo studies have shown that some of them might possess osteoinductive properties. Hence, in the field of tissue engineering biphasic, triphasic and multiphasic calcium orthophosphates represent promising biomaterials to construct various scaffolds capable of carrying and/or modulating the behavior of cells. Furthermore, such scaffolds are also suitable for drug delivery applications. This review summarizes the available information on biphasic, triphasic and multiphasic calcium orthophosphates, including their biomedical applications. New formulations are also proposed.

Biphasic calcium phosphate bioceramics for orthopaedic reconstructions: clinical outcomes

BCP are considered the most promising biomaterials for bone reconstruction. This study aims at analyzing the outcomes of patients who received BCP as bone substitutes in orthopaedic surgeries. Sixty-six patients were categorized according to the etiology and morphology of the bone defects and received scores after clinical and radiographic evaluations. The final results corresponded to the combination of both parameters and varied from 5 (excellent result) to 2 or lower (poor result). Most of the patients who presented cavitary defects or bone losses due to prosthesis placement or revision, osteotomies, or arthrodesis showed good results, and some of them excellent results. However, patients with segmental defects equal or larger than 3 cm in length were classified as moderate results. This study established clinical parameters where the BCP alone can successfully support the osteogenic process and where the association with other tissue engineering strategies may be considered.

Radiographic healing with hemispherical allogeneic femoral head bone grafting for opening-wedge high tibial osteotomy

PURPOSE

The aim of this study was to investigate the remodeling process after hemispherical femoral head allograft grafting in opening-wedge high tibial osteotomy with a plate and screw.

METHODS

The study group included 105 knees in 92 women and 7 knees in 7 men from January 2007 through December 2007. The radiographic bone remodeling process was determined by use of a modification of the radiologic rating system described previously by van Hemert et al. in 4 groups: group A, 7-mm plate correction; group B, 9-mm plate correction; group C, 11-mm plate correction; and group D, 13-mm plate correction.

RESULTS

The postoperative femorotibial angle and tibial slope were not significantly changed at latest follow-up in comparison to immediate postoperative status. The mean follow-up period was 25.4 months (range, 18 to 30 months). In all groups radiologic bone healing higher than phase 3 was successfully achieved between 3 and 6 months. The healing process slowed with increasing correction angle.

CONCLUSIONS

A hemispherical femoral head allograft is a good alternative osseous graft material when patients are selected appropriately with the following criteria: body mass index lower than 40, no symptomatic osteoarthritis of the patellofemoral joint and lateral compartment, no systemic inflammatory arthritis, no history of fracture or previous open surgery to the lower limb, and no flexion contracture.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

β-TCP versus autologous bone for repair of alveolar clefts in a goat model

OBJECTIVE

The aim of this study in goats was to test the hypothesis that a novel synthetic bone substitute beta tricalcium phosphate (β-TCP) can work as well as autologous bone harvested from the iliac crest for grafting and repair of alveolar clefts.

DESIGN

Ten adult Dutch milk goats (Capra hircus) were used in a split-mouth study design.

MAIN OUTCOME MEASURES

Volumetric histologic assessment of new bone formation and radiographic measurement of orthodontic movement of teeth in a formerly created alveolar cleft.

CONCLUSIONS

The synthetic bone substitute β-TCP was shown to result in bone healing similar to that of iliac crest bone. The surgical, orthodontic, and histologic results now warrant the testing of β-TCP in the human cleft situation.

In vitro: osteoclastic activity studies on surfaces of 3D printed calcium phosphate scaffolds

Various biomaterials have been developed for the use as bone substitutes for bone defects. To optimize their integration and functionality, they should be adapted to the individual defect. Rapid prototyping is a manufacturing method to tailor materials to the 3D geometry of the defect. Especially 3D printing allows the manufacture of implants, the shape of which can be designed to fit the bone defect using anatomical information obtained from the patient. 3D printing of calcium phosphates, which are well established as bone substitutes, involves a sintering step after gluing the granules together by a binder liquid. In this study, we analyzed if and how these 3D printed calcium phosphate surfaces can be resorbed by osteoclast-like cells. On 3D printed scaffold surfaces consisting of pure HA and β-TCP as well as a biphasic mixture of HA and TCP the osteoclastic cell differentiation was studied. In this regard, cell proliferation, differentiation, and activation were analyzed with the monocytic cell line RAW 264.7. The results show that osteoclast-like cells were able to resorb calcium phosphate surfaces consisting of granules. Furthermore, biphasic calcium phosphate ceramics exhibit, because of their osteoclastic activation ability, the most promising surface properties to serve as 3D printed bone substitute scaffolds.