New bone formation around porous hydroxyapatite wedge implanted in opening wedge high tibial osteotomy in patients with osteoarthritis

A Comparative Study of HA/DBM Compounds Derived from Bovine and Porcine for Bone Regeneration

This comparative study investigated the tissue regeneration and inflammatory response induced by xenografts comprised of hydroxyapatite (HA) and demineralized bone matrix (DBM) extracted from porcine (P) and bovine (B) sources. First, extraction of HA and DBM was independently conducted, followed by chemical and morphological characterization. Second, mixtures of HA/DBM were prepared in 50/50 and 60/40 concentrations, and the chemical, morphological, and mechanical properties were evaluated. A rat calvarial defect model was used to evaluate the tissue regeneration and inflammatory responses at 3 and 6 months. The commercial allograft DBM Puros® was used as a clinical reference. Different variables related to tissue regeneration were evaluated, including tissue thickness regeneration (%), amount of regenerated bone area (%), and amount of regenerated collagen area (%). The inflammatory response was evaluated by quantifying the blood vessel area. Overall, tissue regeneration from porcine grafts was superior to bovine. After 3 months of implantation, the tissue thickness regeneration in the 50/50P compound and the commercial DBM was significantly higher (~99%) than in the bovine materials (~23%). The 50/50P and DBM produced higher tissue regeneration than the naturally healed controls. Similar trends were observed for the regenerated bone and collagen areas. The blood vessel area was correlated with tissue regeneration in the first 3 months of evaluation. After 6 months of implantation, HA/DBM compounds showed less regenerated collagen than the DBM-only xenografts. In addition, all animal-derived xenografts improved tissue regeneration compared with the naturally healed defects. No clinical complications associated with any implanted compound were noted.

Efficacy of bone grafting materials in preserving the alveolar ridge in a canine model

Preservation of the alveolar ridge after tooth extraction is an essential component for ideal implant positioning. Furthermore, preservation of bone around the implant after implant placement is an essential component for implant treatment. We aimed to evaluate the efficacy of bone grafting materials in preserving the alveolar ridge after implant placement. Implants were placed in regenerated bone without grafting material or with beta-tricalcium phosphate, bovine bone substitute, or carbonate apatite transplantation. In all groups, the bone healed and the implants were successfully placed within the bone. No significant differences in insertion torque and implant stability quotient values were found. The amount of bone around the implant 5 weeks after implant placement was significantly reduced in the bovine bone substitute group; however, implants placed in regenerated bone achieved sufficient initial fixation and osseointegration.

Biocompatible Customized 3D Bone Scaffolds Treated with CRFP, an Osteogenic Peptide

BACKGROUND

Currently used synthetic bone graft substitutes (BGS) are either too weak to bear the principal load or if metallic, they can support loading, but can lead to stress shielding and are unable to integrate fully. In this study, we developed biocompatible, 3D printed scaffolds derived from µCT images of the bone that can overcome these issues and support the growth of osteoblasts.

METHODS

Cylindrical scaffolds were fabricated with acrylonitrile butadiene styrene (ABS) and Stratasys^® MED 610 (MED610) materials. The 3D-printed scaffolds were seeded with Mus musculus calvaria cells (MC3T3). After the cells attained confluence, osteogenesis was induced with and without the addition of calcitonin receptor fragment peptide (CRFP) and the bone matrix production was analyzed. Mechanical compression testing was carried out to measure compressive strength, stiffness, and elastic modulus.

RESULTS

For the ABS scaffolds, there was a 9.8% increase in compressive strength (p < 0.05) in the scaffolds with no pre-coating and the treatment with CRFP, compared to non-treated scaffolds. Similarly, MED610 scaffolds treated with CRFP showed an 11.9% (polylysine pre-coating) and a 20% (no pre-coating) increase (p < 0.01) in compressive strength compared to non-treated scaffolds.

CONCLUSIONS

MED610 scaffolds are excellent BGS as they support osteoblast growth and show enhanced bone growth with enhanced compressive strength when augmented with CRFP.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Porous Biphasic Calcium Phosphate for Biomedical Application

Excellent osteoconductivity and resorbability achieved when porous bioceramics have highsurface area that providing fast bone ingrowth. Porous samples were fabricated by using biphasic calcium phosphate BCP (achieved from HA heat treated at 850 oC) with 10 and 20 wt% of ovalbumin binder powder and mixture of carrot fibers and ovalbumin powders (1:1) then dried at 60oC and fired at 1300 oC. Structural, physical and mechanical properties of the prepared porous bioceramic were determined involved X-ray diffraction, Fourier transform infrared spectroscopy FTIR, apparent porosity, water absorption, apparent solid density and compressive strength. The results of X-ray and FTIR showed that the heat treatment of HA was succeeded in forming biphasic calcium phosphate. The apparent porosity values increased with increasing of the binder and carrot fibers content and the growths density of bacteria on bioceramics are less than natural bone. The effect of pathogenic bacteria (Pseudomonas & Staphylococcus) that cause pollution on porous calcium phosphate and natural bone (Albino mice) has been studied.

Synergistic use of biomaterials and licensed therapeutics to manipulate bone remodelling and promote non-union fracture repair

Disrupted bone metabolism can lead to delayed fracture healing or non-union, often requiring intervention to correct. Although the current clinical gold standard bone graft implants and commercial bone graft substitutes are effective, they possess inherent drawbacks and are limited in their therapeutic capacity for delayed union and non-union repair. Research into advanced biomaterials and therapeutic biomolecules has shown great potential for driving bone regeneration, although few have achieved commercial success or clinical translation. There are a number of therapeutics, which influence bone remodelling, currently licensed for clinical use. Providing an alternative local delivery context for these therapies, can enhance their efficacy and is an emerging trend in bone regenerative therapeutic strategies. This review aims to provide an overview of how biomaterial design has advanced from currently available commercial bone graft substitutes to accommodate previously licensed therapeutics that target local bone restoration and healing in a synergistic manner, and the challenges faced in progressing this research towards clinical reality.

[Management principle and clinical suggestions of osteotomy gap of opening wedge high tibial osteotomy]

OBJECTIVE

To summarize the management principle and clinical suggestions of the osteotomy gap of opening wedge high tibial osteotomy (OWHTO).

METHODS

The related literature of the osteotomy gap of OWHTO in recent years was reviewed, summarized, and analyzed.

RESULTS

Delayed union and non-union of the osteotomy gap are main complications of OWHTO. Tomofix plate, as locking steel plate, has the characteristics of angular stability and can better maintain the stability of the osteotomy gap, promote bone healing, and avoid loss of correction. There are some treatment options for the osteotomy gap site, such as, without bone, autologous bone graft, allogeneic bone graft, bone substitute materials graft, and augment factor graft to enhance bone healing. When the osteotomy gap is less than 10 mm, it achieves a good outcome without bone graft. For the obesity, lateral hinge fracture, large osteotomy gap, or correction angle more than 10°, the bone graft should be considered. In cases whose osteotomy gap is nonunion or delayed union, the autologous bone graft is still the gold standard. When the osteotomy gap repaired with the allogeneic bone graft, it is better to choose fragmented cancellous or wedge-shaped cancellous bone, combining with the locking plate technology, also can achieve better bone union. The bone substitute material of calcium-phosphorus is used in the osteotomy gap, which has the characteristics of excellent bone conduction, good biocompatibility, and resorption, combining with the locking plate technology, which can also achieve better bone union in the osteotomy gap. The augment factors enhance the bone healing of the osteotomy gap of OWHTO is still questionable. The bone union of the osteotomy gap is also related to the size of the osteotomy gap and whether the lateral hinge is broken or not.

CONCLUSION

No matter what type of materials for the osteotomy gap, OWHTO can improve the function and relieve pain for knee osteoarthritis. More randomized controlled trials are needed to provide evidence for clinical decision to determine which treatment option is better for the osteotomy gap of OWHTO.

Treatment of Infected Tibial Non-Unions with Ilizarov Technique: A Case Series

Background: The Ilizarov external fixation technique has been widely used for the treatment of long-bone infected non-unions. After surgical infected bone resection, to allow filling of the remaining bone gap, biomaterials with antibacterial properties could be used. The aim of this study was to report outcomes of infected tibial non-unions treated using the Ilizarov technique and antibacterial bioactive glass. Methods: Between April 2009 and December 2014, 26 patients with infected tibial non-unions were treated with the Ilizarov technique and possible use of the bioactive glass, S53P4. The Association for the Study and Application of Methods of Ilizarov (ASAMI) criteria, a clinical and radiographic evaluating tool, was used for assessing the sample. Results: The average age at the start of treatment was 51 years. The mean follow-up time was 113 weeks. According to the ASAMI Functional Scoring System, 10 excellent (38.5%) cases and 12 good (46.1%) values were recorded. According to the ASAMI Radiological System, they were excellent in 16 (61.5%) cases and good in nine (34.6%). Conclusions: Treatment of infected tibial non-unions using the Ilizarov technique was effective in bone segment regeneration. To fill the remaining bone gap, additional bioactive glass S53P4 could be used, allowing a decrease in re-interventions and minimizing complications.

Treatment of Infected Tibial Non-Unions with Ilizarov Technique: A Case Series

Background: The Ilizarov external fixation technique has been widely used for the treatment of long-bone infected non-unions. After surgical infected bone resection, to allow filling of the remaining bone gap, biomaterials with antibacterial properties could be used. The aim of this study was to report outcomes of infected tibial non-unions treated using the Ilizarov technique and antibacterial bioactive glass. Methods: Between April 2009 and December 2014, 26 patients with infected tibial non-unions were treated with the Ilizarov technique and possible use of the bioactive glass, S53P4. The Association for the Study and Application of Methods of Ilizarov (ASAMI) criteria, a clinical and radiographic evaluating tool, was used for assessing the sample. Results: The average age at the start of treatment was 51 years. The mean follow-up time was 113 weeks. According to the ASAMI Functional Scoring System, 10 excellent (38.5%) cases and 12 good (46.1%) values were recorded. According to the ASAMI Radiological System, they were excellent in 16 (61.5%) cases and good in nine (34.6%). Conclusions: Treatment of infected tibial non-unions using the Ilizarov technique was effective in bone segment regeneration. To fill the remaining bone gap, additional bioactive glass S53P4 could be used, allowing a decrease in re-interventions and minimizing complications.

Development of biodegradable bioactive glass ceramics by DLP printed containing EPCs/BMSCs for bone tissue engineering of rabbit mandible defects

Bioactive glass ceramics have excellent biocompatibility and osteoconductivity; and can form direct chemical bonds with human bones; thus, these ceramic are considered as "Smart" materials. In this study, we develop a new type of bioactive glass ceramic (AP40mod) as a scaffold containing Endothelial progenitor cells (EPCs) and Mesenchymal stem cells (BMSCs) to repair critical-sized bone defects in rabbit mandibles. For in vitro experiments: AP40mod was prepared by Dgital light processing (DLP) system and the optimal ratio of EPCs/BMSCs was screened by analyzing cell proliferation and ALP activity, as well as the influence of genes related to osteogenesis and angiogenesis by direct inoculation into scaffolds. The scaffold showed suitable mechanical properties, with a Bending strength 52.7 MPa and a good biological activity. Additionally, when EPCs/BMSCs ratio were combined at a ratio of 2:1 with AP40mod, the ALP activity, osteogenesis and angiogenesis were significantly increased. For in vivo experiments: application of AP40mod/EPCs/BMSCs (after 7 days of in vitro spin culture) to repair and reconstruct critical-sized mandible defect in rabbit showed that all scaffolds were successfully accurately implanted into the defect area. As revealed by macroscopically and CT at the end of 9 months, defects in the AP40mod/EPCs/BMSCs group were nearly completely covered by normal bone and the degradation rate was 29.9% compared to 20.1% in the AP40mod group by the 3D reconstruction. As revealed by HE and Masson staining analyses, newly formed blood vessels, bone marrow and collagen maturity were significantly increased in the AP40mod/EPCs/BMSCs group compared to those in the AP40mod group. We directly inoculated cells on the novel material to screen for the best inoculation ratio. It is concluded that the AP40mod combination of EPCs/BMSCs is a promising approach for repairing and reconstructing large load bearing bone defect.

Nanomaterials for bone tissue regeneration: updates and future perspectives

Joint replacement and bone reconstructive surgeries are on the rise globally. Current strategies for implants and bone regeneration are associated with poor integration and healing resulting in repeated surgeries. A multidisciplinary approach involving basic biological sciences, tissue engineering, regenerative medicine and clinical research is required to overcome this problem. Considering the nanostructured nature of bone, expertise and resources available through recent advancements in nanobiotechnology enable researchers to design and fabricate devices and drug delivery systems at the nanoscale to be more compatible with the bone tissue environment. The focus of this review is to present the recent progress made in the rationale and design of nanomaterials for tissue engineering and drug delivery relevant to bone regeneration.

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

Bone grafts and bone substitutes for opening-wedge osteotomies of the knee: a systematic review

PURPOSE

To establish the rate of use of various void fillers in the setting of opening-wedge osteotomy around the knee, the types of fixation used, and the rates of delayed union or nonunion related to these variables. In addition, this review addressed short-term to midterm outcomes and complication rates associated with such procedures.

METHODS

The electronic databases Medline, Embase, and PubMed were searched using the methodology for systematic review as recommended by the Cochrane Collaboration. The search terms used were as follows: knee, osteotomy, knee joint, bone grafting, opening osteotomy, opening wedge, tibial osteotomy, femoral osteotomy, and bone substitute. We screened 1,383 articles and applied exclusion criteria. Fifty-six articles were included.

RESULTS

We included 3,033 cases of osteotomy in 2,910 patients. The mean age of patients was 50 years, with a mean follow-up period of 42 months. Male patients comprised 52% of patients. The mean alignment change was 10.8°, shifting the mechanical axis to 5.1° valgus. Delayed union/nonunion rates were 2.6%, 4.6%, and 4.5% for autograft, allograft bone, and synthetic bone substitutes, respectively (P = .03). Delayed union/nonunion rates were significantly lower for autograft compared with allograft (P = .03) and for autograft and allograft compared with synthetic bone substitutes (P < .0001). Non-locking plates (n = 2,148) had a rate of delayed union/nonunion of 3.7% and a mean loss of correction over time of 0.5°. Locking plates (n = 681) had a rate of delayed union/nonunion of 2.6% and a loss of correction of 2.3°. All mean knee outcome scores improved, and an overall complication rate of 14% was found.

CONCLUSIONS

Opening-wedge osteotomy had good short-term to midterm outcomes with acceptable complication rates. The lowest rates of delayed union/nonunion were in autograft bone-filled osteotomies. Plate type does not appear to affect osteotomy union or loss of correction.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I to IV studies.

Hydroxyapatite-coated sillicone rubber enhanced cell adhesion and it may be through the interaction of EF1β and γ-actin

Silicone rubber (SR) is a common soft tissue filler material used in plastic surgery. However, it presents a poor surface for cellular adhesion and suffers from poor biocompatibility. In contrast, hydroxyapatite (HA), a prominent component of animal bone and teeth, can promote improved cell compatibility, but HA is an unsuitable filler material because of the brittleness in mechanism. In this study, using a simple and economical method, two sizes of HA was applied to coat on SR to counteract the poor biocompatibility of SR. Surface and mechanical properties of SR and HA/SRs confirmed that coating with HA changes the surface topology and material properties. Analysis of cell proliferation and adhesion as well as measurement of the expression levels of adhesion related molecules indicated that HA-coated SR significantly increased cell compatibility. Furthermore, mass spectrometry proved that the biocompatibility improvement may be related to elongation factor 1-beta (EF1β)/γ-actin adjusted cytoskeletal rearrangement.

Novel unidirectional porous hydroxyapatite used as a bone substitute for open wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clinically and radiologically evaluate the availability, osteoconductivity, and resorption of a novel unidirectional porous hydroxyapatite (UDPHAp) used as an artificial substitute for open wedge high tibial osteotomy (OWHTO). Our hypothesis was that UDPHAp is a safe and useful bone substitute for OWHTO.

MATERIALS AND METHODS

Seven patients (2 men and 5 women aged 34-72years) who underwent OWHTO and were followed up for more than 12months were retrospectively studied. After the osteotomy, the gap created was filled with UDPHAp(REGENOS® Kuraray Co.Ltd). Radiography and computed tomography(CT) were performed, and gap healing was assessed postoperatively. The Japanese Orthopaedic Association (JOA) knee score was determined pre- and post-operatively for clinical evaluation.

RESULTS

Neither gross displacement nor collapse of the UDPHAp block graft was observed within 12 months after surgery. Both radiographs and CT showed attenuation of lucency and increasing sclerosis over time. JOA score improved from 71.2 (65-80) to 95.8 (85-100).

CONCLUSIONS

Short term results for OWHTO using UDPHAp was satisfactory. Clinical improvement of JOA scores were seen, besides osteogenesis was progressing in and around the artificial bone grafts.

The outcome of bone substitute wedges in medial opening high tibial osteotomy

BACKGROUND

Opening wedge high tibial osteotomy often requires bone grafting to improve the union rate and avoid instability at the osteotomy site. Autograft and allograft have both been associated with complications and the use of bone substitute wedges has been advocated to improve the outcome. This study investigated the clinical, radiological and histological outcomes of using biphasic calcium phosphate ceramic (Triosite) wedges in opening wedge high tibial osteotomy and determined whether the presence of the graft would compromise the satisfactory conversion to a total knee replacement.

METHODS

A consecutive cohort underwent radiological review to determine whether the osteotomy healed and the correction was maintained. Biopsies were performed on those undergoing second procedures. All patients converted to total knee arthroplasty were assessed separately as to any surgical complications attributed to the Triosite wedge.

RESULTS

There were 36 osteotomies in 33 patients with a minimum of 4 years follow up. All osteotomies healed. There was an average 90 (5-14) of correction, which was maintained. Histological assessment of 17 cases confirmed adequate bone replacement of the Triosite although some areas of tricalcium phosphate remained visible. Conversion to a total knee arthroplasty occurred in 11 cases with no complications.

CONCLUSION

Biphasic calcium phosphate ceramic wedges (Triosite) can be reliably used in opening wedge high tibial osteotomy with a low incidence of complications and satisfactory conversion to total knee arthroplasty.

Bovine xenograft locking Puddu plate versus tricalcium phosphate spacer non-locking Puddu plate in opening-wedge high tibial osteotomy: a prospective double-cohort study

PURPOSE

The aim of the study was to compare clinical and radiographic outcomes of opening-wedge high tibial osteotomy (HTO) augmented with either xenograft or tricalcium phosphate spacer for the management of medial compartment osteoarthritis (OA) with genu varum.

METHODS

Between 2004 and 2007, we prospectively enrolled 52 patients with medial compartment knee OA who underwent opening-wedge HTO fixed with locking Puddu plate and xenograft (n = 26) or non-locking Puddu plate and tricalcium phosphate spacer (n = 26). The alignment of the lower limb was assessed by measuring the hip-knee-ankle (HKA) angle. Clinical outcomes were assessed with the Knee Society Score, Western Ontario and McMaster Universities Osteoarthritis Index, SF-36 and European Quality of Life-5 Dimensions scale. All patients were followed up at six weeks and at three, six, 12 and 24 months post-operatively. Clinical outcomes were assessed preoperatively and at 24 months post-operatively.

RESULTS

All clinical scores improved significantly in both groups after surgery, without any significant difference between the two groups. Immediately after surgery, the HKA angle went from 9.1 ± 5.2° in varus to 3.1 ± 4.8° in valgus (P = 0.01) in the xenograft group, and from 8.5 ± 5.9° in varus to 3.4 ± 4.2° in valgus (P = 0.01) in the tricalcium phosphate group. At the last follow-up, the tricalcium phosphate group showed a significant loss of correction (P = 0.03).

CONCLUSIONS

HTO performed with xenograft locking plate and tricalcium phosphate non-locking plate constructs showed good clinical outcomes. However, the xenograft locking plate construct is superior to the tricalcium phosphate spacer non-locking plate to prevent the loss of correction in the middle term.

Patellofemoral alignment and anterior knee pain after closing- and opening-wedge valgus high tibial osteotomy

PURPOSE

The purpose of this study was to compare the clinical and radiographic outcomes of opening- and closing-wedge valgus high tibial osteotomy (HTO) for the treatment of medial unicompartmental knee osteoarthritis with a minimum follow-up of 3 years, with a focus on patellofemoral alignment and anterior knee pain.

METHODS

We performed a retrospective comparison of 50 patients who underwent closing-wedge HTO and 50 patients who underwent opening-wedge HTO for isolated medial joint arthritis of the knee with varus deformity. All patients were evaluated and the 2 study groups were compared after a minimum follow-up of 3 years with a focus on patellofemoral alignment, patellofemoral osteoarthritis, and anterior knee pain while climbing stairs.

RESULTS

Patellar alignment (patellar tilt and lateral patellar displacement) was not significantly different in the 2 groups either preoperatively or at follow-up. Furthermore, there were no significant differences in the extent of patellofemoral arthritis and incidence of anterior knee pain at follow-up between the 2 groups. In addition, no significant intergroup difference was found in terms of the incidence of anterior knee pain (28% in closing-wedge group and 32% in opening-wedge group at follow-up).

CONCLUSIONS

The results of closing- and opening-wedge valgus HTO were not found to be significantly different with respect to patellar alignment, osteoarthritis of the patellofemoral joint, or anterior knee pain.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Production of nanoparticles from natural hydroxylapatite by laser ablation

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism.

High tibial osteotomy using polycaprolactone-tricalcium phosphate polymer wedge in a micro pig model

Medial open-wedge high tibial osteotomy has been gaining popularity in recent years, but adequate supporting material is required in the osteotomy gap for early weight-bearing and rapid union. The purpose of this study was to investigate whether the implantation of a polycaprolactone-tricalcium phosphate composite scaffold wedge would enhance healing of the osteotomy in a micro pig model. We carried out open-wedge high tibial osteotomies in 12 micro pigs aged from 12 to 16 months. A scaffold wedge was inserted into six of the osteotomies while the other six were left open. Bone healing was evaluated after three and six months using plain radiographs, CT scans, measurement of the bone mineral density and histological examination.

Complete bone union was obtained at six months in both groups. There was no collapse at the osteotomy site, loss of correction or failure of fixation in either group. Staining with haematoxylin and eosin demonstrated that there was infiltration of new bone tissue into the macropores and along the periphery of the implanted scaffold in the scaffold group. The CT scans and measurement of the bone mineral density showed that at six months specimens in the scaffold group had a higher bone mineral density than in the control group, although the implantation of the polycaprolactone-tricalcium phosphate composite scaffold wedge did not enhance healing of the osteotomy.

An improved collagen scaffold for skeletal regeneration

Bone repair and regeneration is one of the most extensively studied areas in the field of tissue engineering. All of the current tissue engineering approaches to create bone focus on intramembranous ossification, ignoring the other mechanism of bone formation, endochondral ossification. We propose to create a transient cartilage template in vitro, which could serve as an intermediate for bone formation by the endochondral mechanism once implanted in vivo. The goals of the study are (1) to prepare and characterize type I collagen sponges as a scaffold for the cartilage template, and (2) to establish a method of culturing chondrocytes in type I collagen sponges and induce cell maturation. Collagen sponges were generated from a 1% solution of type I collagen using a freeze/dry technique followed by UV light crosslinking. Chondrocytes isolated from two locations in chick embryo sterna were cultured in these sponges and treated with retinoic acid to induce chondrocyte maturation and extracellular matrix deposition. Material strength testing as well as microscopic and biochemical analyzes were conducted to evaluate the properties of sponges and cell behavior during the culture period. We found that our collagen sponges presented improved stiffness and supported chondrocyte attachment and proliferation. Cells underwent maturation, depositing an abundant extracellular matrix throughout the scaffold, expressing high levels of type X collagen, type I collagen and alkaline phosphatase. These results demonstrate that we have created a transient cartilage template with potential to direct endochondral bone formation after implantation.

Calcium phosphate cement enhances primary stability of open-wedge high-tibial osteotomies

We investigated if injectable calcium phosphate cement improves primary stability in open-wedge high-tibial osteotomy. A 10 mm open-wedge osteotomy was performed on eight pairs of preserved cadaver tibiae and seven pairs of composite (Sawbone) left tibiae. Osteosynthesis was performed with the Dynafix plate system. The gap resulting from surgery either was filled with 15 g injectable calcium phosphate cement in half the bones or was left untreated. The composite tibiae were loaded at a ramp speed of 20 mm/min up to 20 kN. The cadaver tibiae were exposed to 100 cycles with a maximum compressive force of 2,250 N. After 100 cycles of loading with 2,250 N, the final loaded displacement was 1.2 mm for the cadaver tibiae treated with injectable calcium phosphate cement as compared with 3.6 mm for the empty defects (P = 0.028). All the seven empty defect composite specimens failed prior to 20 kN (median 2.8 kN) as compared with five of the injectable calcium phosphate cement specimens (median 17 kN) (P = 0.005). The injection of injectable calcium phosphate cement following open-wedge osteotomy of the proximal tibia increases the initial stability of the bone as measured by load-to-failure and displacement after cyclic loading. Clinical studies are ongoing to investigate whether injectable calcium phosphate cement also has clinical advantage on wedge healing and stability.

Modified biplanar open-wedge high tibial osteotomy with rigid locking plate to treat varus knee

OBJECTIVE

To introduce and characterize the modified biplanar opening high tibial osteotomy with rigid fixation to treat varus knee in young and active patients.

METHODS

Between June 2001 to July 2008, 18 patients with monocompartmental degeneration of the knee combined with a varus malalignment of the leg had the modified biplanar opening high tibial osteotomy and the osteotomy was fixed with the locking plates (Locking Compression Plate System). The mean varus deformity before operation was 11.5 degrees (5 degrees approximately 19 degrees ) and no degenerative changes were found in other departments. Stability of the knee was normal in 15 patients, but ruptures in anterior cruciate ligaments or lateral collateral ligament were presented in the remaining 3 patients. Preoperative symptom was mainly limited in the pain of medial compartment. The preoperative and follow-up data for the range of motion and Lysholm score were determined. Subjective satisfactory examination was also applied to the patients for the operation they selected.

RESULTS

All of the patients were followed up with an average of 32.5 months (12 approximately 82 months). There was no ununion or delayed union in this group during the follow-up period. No complications like broken plate, nerve injury, or blood vessel injury occurred. The postoperative average corrected degree was 9.5 degrees (5.5 degrees approximately18 degrees ). No degenerations developed in the three departments of the knee. The Lysholm scores before and after surgery were 42.5 and 77.5, respectively (P<0.01). The overall fineness rate was 83.3%. The subjective satisfactory survey demonstrated that about 83.3% patients showed satisfactory on the operation. There was no obvious difference in the range of motion before and after operation, but significant changes were found in the Lysholm score and varus degree from preoperative to follow-up.

CONCLUSION

Proximal opening high tibial osteotomy performed in conjunction with the special rigid locking plate yielded good results for symptomatic genu varum. This new classic technique can be effectively applied to the medial compartment degeneration of the knee in active young patients.

In vivo study on hydroxyapatite scaffolds with trabecular architecture for bone repair

The objective of this research was to investigate the bone formation and angio-conductive potential of hydroxyapatite (HA) scaffolds closely matched to trabecular bone in a canine segmental defect after 3 and 12 weeks post implantation. Histomorphometric comparisons were made between naturally forming trabecular bone (control) and defects implanted with scaffolds fabricated with micro-size (M-HA) and nano-size HA (N-HA) ceramic surfaces. Scaffold architecture was similar to trabecular bone formed in control defects at 3 weeks. No significant differences were identified between the two HA scaffolds; however, significant bone in-growth was observed by 12 weeks with 43.9 +/- 4.1% and 50.4 +/- 8.8% of the cross-sectional area filled with mineralized bone in M-HA and N-HA scaffolds, respectively. Partially organized, lamellar collagen fibrils were identified by birefringence under cross-polarized light at both 3 and 12 weeks post implantation. Substantial blood vessel infiltration was identified in the scaffolds and compared with the distribution and diameter of vessels in the surrounding cortical bone. Vessels were less numerous but significantly larger than native cortical Haversian and Volkmann canals reflecting the scaffold architecture where open spaces allowed interconnected channels of bone to form. This study demonstrated the potential of trabecular bone modeled, highly porous and interconnected, HA scaffolds for regenerative orthopedics.

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

INTRODUCTION

Biphasic calcium phosphate (BCP) has proved to be an effective bone substitute, but it's effectiveness and remodeling potential in open wedge high tibial osteotomy (OWHTO) has not been analyzed yet. This study sought to evaluate the bone healing and remodeling potentials of BCP granules using a radiographic rating system in biplanar OWHTO.

MATERIALS AND METHODS

Fifteen patients (15 knees) underwent biplanar OWHTO. Bone gaps were filled with BCP granules. For radiographic evaluation, remodeling was divided into four phases. Phase 1 was accepted as rounded osteotomy sites, with clear distinction between BCP and bone, phase 2 was accepted as whitened osteotomy sites, with distinction between BCP and bone still visible, phase 3 was accepted as distinction between BCP and bone not visible and cloudy bone formation and phase 4 was accepted as full reformation of BCP granules (4A-BCP visible, 4B-disappearence of BCP) with no sign of osteotomy. Bone union was confirmed with clinical (full weight bearing without pain) and radiographic evaluation (cortical bridging callus on radiographs and phase 3 or greater remodeling). The time to full remodeling and the starting point of the consolidation on anteroposterior radiographs were noted. Complications were also noted at each clinical follow-up.

RESULTS

Mean follow-up was 27.2 months. The mean age was 55.8 years. At clinical follow-up, there were no wound healing problems, no loss of corrections, no infections, and no complications. All osteotomies successfully healed. According to the radiologic classification system, at the 6th week, 73.3% (11/15) of patients were in phase 1 and the remaining 26.7% (4/15) were in phase 2. At 12-month follow-up, 46.7 (7/15) of the patients were still in phase 3. After 2 years, all radiographs showed to be in phase 4A. Radiographic union was noted to progress from lateral to medial and finally central.

CONCLUSIONS

BCP can be successfully used as a bone substitute. The radiographic remodeling and consolidation process of BCP was found to be different from that of beta-tricalcium phosphate. In our patients with more than 2 years of follow-up, BCP granules did not completely remodel. As a result, this clinical study demonstrated that calcium phosphate granules containing hydroxyapatite had a long period of "creeping substitution" that lasts longer than 2 years.

Stability of medial opening wedge high tibial osteotomy: a failure analysis

Medial opening wedge high tibial osteotmy (HTO) is often used to treat varus gonarthrosis in young, active, highly demanding patients, although it has many pitfalls, which were evaluated in a consecutive cohort of patients. A retrospective analysis of a consecutive series of 45 patients with 49 medial opening HTO for varus gonarthrosis using a spacer plate (Puddu I, Arthrex, USA) were included. A Chi square test was used to study the effect between the wedge size and complications. Complications occurred in 22 knees (45%). There was no significant difference between groups for individual complications; however, when combined, there were significantly more complications in the >10 mm wedge group (Chi square p = 0.05). The overall complication rate in this series was 45%. The majority were related to intrinsic instability at the osteotomy site (24%) and surgical technique (20%). The evaluated spacer provided inadequate stability.

Do we need synthetic osteotomy augmentation materials for opening-wedge high tibial osteotomy

High tibial osteotomy (HTO) is an increasing popular method to treat unicompartimental osteoarthritis of the knee in younger, active patients. In so doing one tries to delay the need for total or unicompartimental joint replacement. The augmentation of HTO opening gaps with supporting material is discussed controversially, especially after the introduction of locking plates, which contribute to the decline of the non-union rate. Currently, we do not recommend synthetic augmentation, when using locking plates in HTO with opening angles less than 10 degrees . In our recent randomized study we could histologically and radiologically demonstrate the complete rebuilding of lamelliform bone in patients without synthetic augmentation, whilst bony ingrowth into the hydroxyapatite/tricalcium phosphate (HA/TCP) wedge of augmented osteotomies just slowly progressed. In contrast to unaugmented osteotomies, there was no advantage in using HA/TCP wedges or the combination of HA/TCP wedges and platelet rich plasma (PRP) as supporting material after 12 months. In osteotomies where an opening angle bigger than 7.5 degrees is chosen, rigid locking plates should be used. In our opinion, autologous iliac crest graft should be used in the high-risk patients (obese, smoker, opening angle bigger than 10 degrees ). Whether synthetic augmentation combined with PRP is equal or even superior to autologous iliac crest graft in openings bigger than 10 degrees has not been proven yet.

Resorbability of rigid beta-tricalcium phosphate wedges in open-wedge high tibial osteotomy: a retrospective radiological study

The open-wedge high tibial osteotomy (OWHTO) is a well accepted treatment modality for patients with osteoarthritis of the medial compartment associated with genu varum. To fill in the osteotomy gap 30% macroporosity rigid beta-tricalcium phosphate (beta-TCP) is frequently used as a stable resorbable bone substitute. However, the resorbability of these beta-TCP wedges is not known. The aim of this study was to investigate this. Twenty-one OWHTO procedures in seventeen patients were performed with the use of 30% macroporosity rigid beta-TCP wedges. The osteotomies were fixed using an angle-stable locking plate. Conventional AP and lateral radiographs were examined in order to assess the resorbability of the 30% macroporosity rigid beta-TCP wedges as a function of time. A radiological classification system consisting of five phases was used to monitor the resorption of the 30% macroporosity rigid beta-TCP wedges. The mean duration of follow-up was 62 months (+/-23 range of 28-99). In all 21 cases, remnants of the 30% macroporosity rigid beta-TCP wedges were still present at maximum follow-up. Although the boundaries between 30% macroporosity rigid beta-TCP wedges and bone remained slightly visible, all osteotomies were completely consolidated and full osseointegration took place. In 16 out of 21 knees the fixation system was removed after a mean duration of 32 months (+/-19 range of 6-62). In six out of 21 knees a conversion to a knee arthroplasty was performed after a mean duration of 56 months (+/-18 range of 37-82). The OWHTO did not interfere with the placement of knee prostheses. Complete resorption of 30% macroporosity rigid beta-TCP wedges did not take place up to 8 years after operation.

Opening wedge high tibial osteotomy using 3D biomodelling Bonelike macroporous structures: case report

Two synthetic calcium phosphates in porous wedge shape, Bonelike and a commercial HA/beta-TCP biphasic material, were used as an alternative to bone autografts and allografts in the treatment of medial compartment osteoarthritis of varus knees. The structure of Bonelike has a 3D architecture that is computer controlled, and a composition that mimics the mineral composition of natural bone. The HA/beta-TCP biphasic material used as a control material in this study was prepared using conventional foaming based methods. No signs of inflammatory reactions were observed post-operatively for both materials. After 4 months signs of fusion at the osteotomy site and good integration of the implanted wedges were observed, showing good mechanical resistance. Concerning the final correction attained, the left knee revealed a satisfactory valgus of 10 degrees , but the right one only had a final value of 6 degrees . The clinical evaluation using International Knee Score (IKS) showed good outcome in all parameters with complete range of motion in both knees and climbing stairs without crutches with only slight pain.

Effects of trabecular calcium phosphate scaffolds on stress signaling in osteoblast precursor cells

The objective of this research was to investigate stress-signaling patterns in response to two-dimensional (2-D) and three-dimensional (3-D) calcium phosphate (CP) materials using human embryonic palatal mesenchyme cells (HEPM, CRL-1486, ATCC, Manassas, VA), an osteoblast precursor cell line. Control discs and scaffolds were fabricated from hydroxyapatite and beta tri-CP ceramics. Phospho-specific antibody cell-based ELISA technique was utilized on members of the mitogen-activated protein kinase cascade including; the extracellular signal-regulated kinases (ERK1/2), p38, c-Jun N-terminal kinase (JNK), and the anti-apoptosis mediator protein kinase B (AKT). Quantification of these signals was evaluated during the early attachment phase of osteoblast precursor cells. In this study, it was observed that 3-D CP scaffolds significantly activated the stress mediators p38 and JNK but not ERK1/2. This signal trend was matched with an up-regulation in AKT, suggesting the ability of cells to manage high stress signals in response to 3-D CP architecture and that 3-D CP scaffolds are necessary for studies simulating a natural trabecular bone organization. The absence of these signals in 2-D CP surfaces indicated the importance of local architecture conditions on cell stress response. It was concluded from this study that osteoblast precursor cells cultured in 3-D CP scaffolds experience greater stress-signaling patterns when compared to 2-D CP surfaces.

Histological and scanning electron microscopy analyses of bone/implant interface using the novel Bonelike synthetic bone graft

Synthetic bone grafts provide an alternative to autografts and allografts. Bonelike is a patented synthetic bone graft that mimics the mineral composition of bone. The aim of the present work was to assess the biological behavior of Bonelike graft in humans, before using the material in orthopedic applications of bone regeneration, for example, in opening wedge high tibial osteotomies for medial knee osteoarthritis. Bonelike granules were implanted in cortical bone of 11 patients undergoing osteotomies, and new bone formation, osteoconductive properties, and resorption characteristics of the granules were analyzed. The granules ranged from 500 to 1000 microm and were implanted in the lateral aspect of the tibia. The patients' mean age was 59 years (range 48 to 70 years); there were eight women and three men, all suffering from medial compartment osteoarthritis of the knee. At surgery, a 1 x 1 x 1-cm cortical defect was created 3 cm distal to the entry point of the screws, in line with the long axis of tibia. The implanted Bonelike graft sample was extracted for analysis during removal of the metallic prosthesis after implantation times of 6, 9, and 12 months. Radiological follow-up, scanning electron microscopy, histological analysis, and histomorphometric measurements were conducted on the retrieved samples to assess bone regeneration in the defect area. Osteoconductive capacity was demonstrated by extensive mature bone formation around the implanted granules and high levels of percentage bone-to-graft contact (from 67-84%). Bonelike acted as an excellent bioactive scaffold, allowing the migration, proliferation, and differentiation of bone cells on its surface, and therefore regeneration of the defects was achieved in a rapid, controlled manner. Our results suggest that Bonelike graft is an excellent candidate for orthopedic applications where rapid new bone formation is a fundamental requirement.

Dome-shaped high tibial osteotomy: a long-term follow-up study

BACKGROUND

High tibial osteotomy (HTO) is a well-established treatment for unicompartmental gonarthrosis of the knee, but its durability and complications remain controversial. We previously introduced a novel dome-shaped HTO, and the long-term follow-up results using this technique are analyzed in this study.

METHODS

We treated 25 varus knees in 22 patients with medial gonarthrosis, using a specially designed calibrated cutting jig along with rigid external fixation and early joint motion postoperatively. A total of 16 patients (19 knees) completed the study protocol and were followed up for 13-16 years (mean, 15 years).

RESULTS

The surgery attempted to obtain 8 degrees valgus; the actual postoperative alignment averaged 12.4 degrees valgus, which decreased significantly to 7.8 degrees valgus after 5 years. The outcome as assessed by the Hospital for Special Surgery knee score was excellent or good in 18 knees at 5 years postoperatively, and in 13 knees at the final follow-up, showing a significant deterioration with time. Loss of correction with time was not correlated with the postoperative alignment achieved: at 5 years, loss greater than 2 degrees was found in 12 knees, but their mean corrected angle (11.8 degrees valgus) was not significantly different from that of the others (13.3 degrees valgus). Nor was the loss of correction correlated with the knee scores. The mean amount of joint motion after surgery did not change significantly with time: 124 degrees preoperatively and 114 degrees at the final follow-up. The patellar position also did not change from preoperative values during postoperative follow-up: mean Insall-Salvati index was 0.88 before and 0.90 5 years after surgery, neither showing patella baja.

CONCLUSION

Dome-shaped HTO is a durable time-buying procedure for patients with unicompartmental medial gonarthrosis, and can avoid subsequent development of patella baja that may complicate further prosthetic arthroplasty.

Anterior opening wedge osteotomy of the proximal tibia for anterior knee pain in idiopathic hyperextension knees

We analysed 20 patients with 24 knees affected by idiopathic genu recurvatum who were treated with an anterior opening wedge osteotomy of the proximal tibia because of anterior knee pain. We managed to attain full satisfaction in 83% of the patients with a mean follow-up of 7.4 years. The mean Hospital for Special Surgery score was 90.3 (range 70.5-99.5), and the mean Knee Society score score was 94.6 (70-100) for function and 87.7 (47-100) for pain. The mean Western Ontario and McMaster University Osteoarthritis Index score for knee function was 87.5 (42-100), for stiffness 82.8 (25-100) and for pain 87.3 (55-100). Radiographs showed a significant increase in posterior tibial slope of 9.4 deg and a significant decrease of patellar height according to the Blackburne-Peel method of 0.16 postoperatively. No cases of non-union, deep infection or compartment syndrome were seen. No osteoarthritic changes in the lateral or medial knee compartment were found with more than 5 years' follow-up in 16 patients with 19 affected knees. Three out of the four dissatisfied patients had a patella infera which led to patellofemoral complaints. One patient in the study underwent a secondary superior displacement of the patella with excellent results. We conclude that in a selected group of patients with idiopathic genu recurvatum and anterior knee pain an opening wedge osteotomy of the proximal tibia can be beneficial.

Biomechanical investigation of different internal fixations in medial opening-wedge high tibial osteotomy

BACKGROUND

The medial opening-wedge osteotomy for treatment of varus gonarthritis has become very popular in recent years. Different implants for internal fixation after the osteotomy have been created. It is still unclear, which principle of internal fixation (angle stable or non-angle-stable plate with or without spacer) has the best biomechanical properties. The aim of this study was to determine the biomechanical properties of different fixation techniques in medial opening-wedge high tibial osteotomy in a porcine bone model.

METHODS

A 10-mm high tibial opening-wedge osteotomy was performed and stabilized with plates of similar dimensions but different functional principle (conventional plate, angle stable plate with or without spacer). Biomechanical properties (stiffness, displacement within the osteotomy space and load at failure) were evaluated under axial load.

RESULTS

Plates which contain a spacer had a significantly higher stiffness at a load at 1000 N (p < 0.05). This correlates with a significantly reduced deformation within the osteotomy space. The strength at failure was not different between the groups. The use of a spacer in a conventional plate produces fractures of the lateral tibial cortex. In angle stable plates and plates containing spacers, the failure was caused by fractures of the lateral tibia surface, the fibula or by displacement within the tibio-fibular joint. The failure was caused primarily by implant insufficiency in plates without spacers.

CONCLUSIONS

In a model with comparable conditions, implants which contain a spacer have superior biomechanical properties. Angle stable plates may prevent fractures of the lateral cortex after opening-wedge osteotomy.

Mechanism of bone incorporation of β-TCP bone substitute in open wedge tibial osteotomy in patients

A histological study was performed of bone biopsies from 16 patients (17 biopsies) treated with open wedge high tibial osteotomies for medial knee osteoarthritis. The open wedge osteotomies were filled with a wedge of osteoconductive beta tricalcium phosphate (beta-TCP) ceramic bone replacement. At the time of removal of the fixation material, core biopsies of the area where the beta-TCP was located were taken at different follow-up periods (6-25 months). beta-TCP resorption, bone ingrowth and bone remodelling were studied. We hypothesized that the incorporation and remodelling process occurs similarly as in animals. Histology showed a good resorption of the beta-TCP with complete incorporation and remodelling into new bone. The different phases as described in animal studies were found. A correlation was found between histological findings and radiological assessment. In conclusion, beta-TCP appeared to be a bone replacement material with optimal biocompatibility, resorption characteristics and bone conduction properties for the clinical use.

Biomechanical stability of high tibial opening wedge osteotomy: internal fixation versus external fixation

PURPOSE

The goal of our study was to evaluate stability of internal fixation with a plate compared to external fixation in an opening wedge high tibial osteotomy model. Significance. To our knowledge, this is the only study to compare internal plate to external fixation in an opening wedge osteotomy model. The design of this cadaver study limits its direct application to clinical practice.

MATERIAL AND METHOD

In each of the six pairs of fresh-frozen human cadaver knees one specimen was randomly assigned to internal plate fixation while the other was stabilized with an external fixation. The osteosynthesis plate incorporated a 12.5mm block that distracted the medial tibial cortices. Each knee was loaded on a mechanical testing machine to 700 N for 10,000 cycles to simulate immediate full weight bearing in a walking individual.

SUMMARY OF RESULTS

The internal plate osteosynthesis provided significantly greater stiffness and smaller loss of correction (1.60mm) than the external fixation (3.22 mm) under cyclic loading condition (P<0.05). For static loading, the mean value of stiffness resulting in failure for the internal plate and external fixation, were respectively, 938 N/mm and 459 N/mm. Load to failure also showed two times greater stiffness in the plate osteosynthesis group. No hardware failure was observed in either construct.

DISCUSSION AND CONCLUSION

Plate fixation was superior to external fixation in maintaining correction. However, progressive adjustment of the distraction with the external fixator allows precise "fine-tuning" during the healing process that is not possible with internal fixation.

Laser surface modification of hydroxyapatite and glass-reinforced hydroxyapatite

Surface treatment of materials with excimer laser radiation often results in the formation of a rough columnar or cone-shaped surface topography, which leads to a considerable increase in the surface area. As a result, the search for a non-porous bioactive material with adequate mechanical properties and a high surface to volume ratio, similar to porous materials, which could be used for drug delivery in the treatment of periodontitis, justified assessing excimer laser surface treatment to promote controlled roughning of hydroxyapatite (HA) and glass-reinforced hydroxyapatite (GR-HA). A KrF excimer laser with 248 nm radiation wavelength and 30 ns pulse duration was used for surface modification. The laser treatment was carried out in air, using wide ranges of radiation fluence and number of laser pulses. In order to identify the physico-chemical changes induced by the laser treatment and the column formation mechanisms in these materials, the treated surfaces were characterised by laser profilometry, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infra-red spectroscopy (FTIR). Laser processing induced the formation of a surface topography consisting of cone-shaped features. The constitution of the surface layer was also modified, as revealed by FTIR, XPS and XRD. This work has shown that laser surface modification increases the surface area of HA and GR-HA and is a promising technique to increase the reactivity and drug delivery capability of both materials.

Neuartiges Knochenaufbaumaterial auf Kalziumphosphatbasis

BACKGROUND

Up to now hydroxyapatite (HA) and beta-tricalciumphosphate (beta-TCP) ceramics have been routinely sintered at temperatures between 1100 degrees and 1500 degrees C. Our new calcium ceramic is fabricated by a sol-gel process at 200 degrees C. The aim of this investigation was to test the biodegradation of and the induction of bone formation by this material.

MATERIAL AND METHODS

Eighteen 1-year-old Goettingen minipigs were divided into three groups. Critical size defects (>5 cm(3)) in the mandible were treated differently in all three animals (group 1: filling with 40% beta-TCP plus 60% HA, group 2: pure HA was applied, group 3 served as controls: only gelatinous material was given). Macroscopic and microscopic investigations of the former defects were made 8 months postoperatively. RESULTS. In groups 1 and 2 biodegradation of more than 93% of the new calcium phosphate formula was found 8 months postoperatively and considered to be very good. No difference was observed between pure HA (group 2) and the combination of HA and beta-TCP (group 1). In both groups complete bone formation was seen macroscopically in the former defects. In the control group only incomplete bone formation with 48.4% of the defect area was noted. This difference was significant ( p<0.001).

DISCUSSION

The new calcium phosphate formula made by a sol-gel method at 120 degrees C seems to be suitable for filling bone defects and is of interest for orthopedic surgery, traumatology, craniomaxillofacial surgery, and dentistry.

Effect of ball milling on the processing of bone substitutes with calcium phosphate powders

Decreasing the microscale morphology of synthetic bone substitutes is of primary importance in order to enhance the morphology of the surface of the material, which is directly in contact with osteoconductive cells when it is implanted in bone. The aim of this study was to investigate the influence of ball milling of slurries on the microscale morphology of hydroxyapatite and tricalcium phosphate bone substitutes and the influence on their processing. Ball milling appeared to be a successful method in order to raise the sintering reactivity of the powders, that is, to decrease the sintering temperature and microstructural morphology of the material. However, it was demonstrated that ball milling had a great influence on dispersion, which became very difficult under long milling times because of dissolution of the calcium phosphate powders. Due to dissolution, ionic species were generated in the slurry and interfered with the dispersing agent. Moreover a reprecipitation process occurred simultaneously, and large particles of the most stable phase (HAP) formed. The presence of such large particles generated stress gradients and cracks in the material during the sintering stage.

Primary stability of various implants in tibial opening wedge osteotomy: a biomechanical study

High tibial osteotomy (HTO) is an established method for treating varus gonarthrosis. The opening wedge HTO has some advantages over the lateral closed wedge technique. In this biomechanical study various systems of internal fixation of medial HTO were compared using an animal cadaver model (lower leg specimens from 1-year-old female domestic pigs). The first osteotomy (10 degrees ) was carried out and stabilized with a C-plate, an Arthrex spacer plate, or an AO tibial plate with or without bone graft. The resistance to axial stress was tested in a mechanical testing machine. Under lower axial stress (25, 50, 75, 100 N) the axial displacement between the various specimens did not show any significant differences. Under maximal axial force, the specimen fixed with the C-plate ( Fmax 2042 N) showed significantly better stability than the Arthrex plate ( Fmax 1687 N); P < 0.05. The AO plate ( Fmax 1612 N without bone graft and Fmax 1583 N with bone graft) showed the lowest axial exposure to stress. Moreover, the influence of the osteotomy angle (7.5 degrees, 10 degrees, 12.5 degrees, 15 degrees ) on axial stress resistance ( Fmax 2548, 2090, 1975, and 1740, respectively) was evaluated, and a direct correlation was found ( R = 0.794, P < 0.05).

Medial opening-wedge high tibial osteotomy with use of porous hydroxyapatite to treat medial compartment osteoarthritis of the knee

BACKGROUND

The aims of this study were to investigate the results of opening-wedge high tibial valgus osteotomy in patients with medial compartment osteoarthritis of the knee and to examine the usefulness of hydroxyapatite wedges as the supporting material.

METHODS

Medial opening-wedge osteotomy was performed in twenty-one osteoarthritic knees in eighteen patients who had a mean age of 66.6 years. The mean duration of follow-up was 78.6 months. A medial transverse osteotomy was performed proximal to the tibial tuberosity, with the most lateral 10% of the tibia left intact. The medial side of the osteotomy site was opened to the desired angle of correction. Two hydroxyapatite wedges of the same size (5.0, 7.5, or 10.0 mm) were inserted into the opened osteotomy site along with bone grafts, and the fragments were fixed with two plates. The angle of correction could be adjusted by altering the direction of wedge insertion. The goal was to achieve a final standing alignment of 10 degrees of anatomical valgus angulation.

RESULTS

All patients had pain relief and improvement in walking ability after the osteotomy. The mean knee and function scores of the American Knee Society were 60.2 +/- 5.3 and 48.1 +/- 10.4 points, respectively, before the osteotomy and 94.3 +/- 7.3 and 93.1 +/- 9.8 points, respectively, at the time of the final follow-up. Limb alignment, expressed as the standing femorotibial angle, was corrected from 180 degrees +/- 2.9 degrees preoperatively to 169.7 degrees +/- 3.7 degrees (10.3 degrees of anatomical valgus angulation) at the time of the latest follow-up. There were no cases of recurrence of varus deformity or collapse of the hydroxyapatite wedges.

CONCLUSIONS

After a mean duration of follow-up of 6.6 years, we found that the medial opening-wedge osteotomy of the proximal part of the tibia provided satisfactory clinical results for patients with osteoarthritis of the knee. Use of the porous hydroxyapatite wedges resulted in no collapse or subsidence at the osteotomy site.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series [no, or historical, control group]). See p. 2 for complete description of levels of evidence.