Nano-Hydroxyapatite Bone Substitute Functionalized with Bone Active Molecules for Enhanced Cranial Bone Regeneration

The aim of this study was to synthesize and characterize a nano-hydroxyapatite (nHAP) and calcium sulfate bone substitute (NC) for cranioplasty. The NC was functionalized with low concentrations of bone morphogenetic protein-2 (BMP-2) and zoledronic acid (ZA) and characterized both in vitro and in vivo. In vitro studies included MTT, ALP assays, and fluorescent staining of Saos-2 (human osteoblasts) and MC3T3-E1 (murine preosteoblasts) cells cultured on NC. An in vivo study divided 20 male Wistar rats into four groups: control (defect only), NC, NC + ZA, and NC + ZA + rhBMP-2. The materials were implanted in an 8.5 mm critical size defect in the calvarium for 12 weeks. Micro-CT quantitative analysis was carried out in vivo at 8 weeks and ex vivo after 12 weeks. Mineralization was highest in the NC + ZA + rhBMP-2 group (13.0 ± 2.8 mm³) compared to the NC + ZA group (9.0 ± 3.2 mm³), NC group (6.4 ± 1.9 mm³), and control group (3.4 ± 1.0 mm³) after 12 weeks. Histological and spectroscopic analysis of the defect site provided a qualitative confirmation of neo-bone, which was in agreement with the micro-CT results. In conclusion, NC can be used as a carrier for bioactive molecules, and functionalization with rhBMP-2 and ZA in low doses enhances bone regeneration.

Do osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration? Investigating the efficacy of BMP-7 and zoledronate treatment of diaphyseal fractures in an open fracture osteoporotic rat model

Osteoporotic fractures may pose a challenge for skeletal regeneration. This study investigates if pharmaceutical interventions such as bone morphogenetic protein 7 (BMP-7) alone or in combination with Zoledronate have equivalent efficacy in osteoporotic bone? Our findings suggest they do and that an osteoporotic bone environment may increase sensitivity to BMP-7.

INTRODUCTION

Osteoporosis is thought to contribute to delayed or impaired bone healing. Bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA) has proven effective in augmenting the regenerative response in healthy young male rats. Yet their comparative efficacy in an osteoporotic bone environment is unknown. Our study aimed to answer the following questions using the ovariectomized (OVX) rat model of osteoporosis: Do osteoporotic fractures pose a greater challenge for skeletal regeneration? Are interventions with BMP-7-alone or combined with ZA of equivalent efficacy in osteoporotic bone?

METHODS

Sham operations (n = 33) or ovariectomies (n = 34) were performed in 12-week-old female Sprague-Dawley rats. Mid-diaphyseal open femoral osteotomies were created at 24 weeks of age and the rats allocated to either (i) untreated, (ii) BMP-7-only or (iii) BMP-7 + ZA treatment groups. At 6 weeks post-osteotomy, fracture healing was evaluated by radiography, μCT and 3-point bending mechanical tests.

RESULTS

Cumulatively, radiological, micro-structural and mechanical measures were equivalent in both healthy and osteoporotic environments. A reduced response to BMP-7-alone was observed in healthy rats that may be age/gender- or protocol/fracture-model dependent. Conversely, the BMP-7-only treated OVX group attained 100 % union in addition to significantly increased measures of mineralized bone volume, total callus volume, peak force and absorbed energy relative to untreated OVX fractures.

CONCLUSIONS

Our findings refute the hypothesis that osteoporotic fractures constitute a greater recalcitrant challenge for skeletal regeneration. Furthermore, our results suggest that an oestrogen-deficient environment may in fact cause an increased sensitivity to BMP-7.

Muscle as an osteoinductive niche for local bone formation with the use of a biphasic calcium sulphate/hydroxyapatite biomaterial

Objectives

We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells.

Materials and Methods

We seeded mouse skeletal muscle cells C2C12 on the hydroxyapatite/calcium sulphate biomaterial and the phenotype of the cells was analysed. To mimic surgical conditions with leakage of extra cellular matrix (ECM) proteins and growth factors, we cultured rat bone cells ROS 17/2.8 in a bioreactor and harvested the secreted proteins. The secretome was added to rat muscle cells L6. The phenotype of the muscle cells after treatment with the media was assessed using immunostaining and light microscopy.

Results

C2C12 cells differentiated into osteoblast-like cells expressing prominent bone markers after seeding on the biomaterial. The conditioned media of the ROS 17/2.8 contained bone morphogenetic protein-2 (BMP-2 8.4 ng/mg, standard deviation (sd) 0.8) and BMP-7 (50.6 ng/mg, sd 2.2). In vitro, this secretome induced differentiation of skeletal muscle cells L6 towards an osteogenic lineage.

Conclusion

Extra cellular matrix proteins and growth factors leaking from a bone cavity, along with a ceramic biomaterial, can synergistically enhance the process of ectopic ossification. The overlaying muscle acts as an osteoinductive niche, and provides the required cells for bone formation.

Cite this article: D. B. Raina, A. Gupta, M. M. Petersen, W. Hettwer, M. McNally, M. Tägil, M-H. Zheng, A. Kumar, L. Lidgren. Muscle as an osteoinductive niche for local bone formation with the use of a biphasic calcium sulphate/hydroxyapatite biomaterial. Bone Joint Res 2016;5:500–511. DOI: 10.1302/2046-3758.510.BJR-2016-0133.R1.

Avanta Versus Swanson Silicone Implants in the MCP Joint—A Prospective, Randomized Comparison of 30 Patients Followed for 2 Years

The results of Swanson and Avanta metacarpophalangeal joint arthroplasties in rheumatoid patients were compared in a prospective, randomized study of 30 patients (120 implants). At 2-year follow-up, grip strength was measured, hand function was assessed with the Sollerman test and the subjective outcome was determined with visual analogue scores. With both implants ulnar deviation and flexion deformities decreased, and there was no difference between the groups. The increase in range of motion was 7° greater with Avanta implants than with Swanson implants. Grip strength and hand function were unaltered but the visual analogue scales showed decreased pain levels and subjective improvements in hand function, grip strength and cosmesis. Twenty-four of 30 patients were satisfied. Fracture of the silicone spacer occurred with 12 Avanta (20%) and eight Swanson implants (13%), with a higher fracture frequency in men.

Tissue reaction and material biodegradation of a calcium sulfate/apatite biphasic bone substitute in rat muscle

Background/Objective

A biphasic ceramic bone substitute consisting of calcium sulfate and hydroxyapatite has been reported to give good clinical outcome regarding bone regeneration and may serve as a carrier for antibiotics in the treatment of bone infections. Often, the overlying muscle is in direct contact with the synthetic graft. The dissolving bone substitute induces inflammation, which may be harmful to the surrounding soft and muscle tissue. The aim of the present study was to evaluate the surrounding soft tissue reaction and the biodegradation of the biphasic bone substitute.

Methods

Rods (3 mm × 6 mm) were cast and implanted in the rat abdominal rectus muscle. The rods were either soaked or not soaked in autologous bone marrow before insertion to induce bone formation. Thirty-two rats underwent bilateral operation. After 6 weeks and 12 weeks, the bone substitute material and the surrounding muscle were harvested. The right rod was evaluated by histology to study tissue reaction and the left rod was analysed with micro-computed tomography and scanning electron microscopy to study bone substitute degradation.

Results

The muscle tissue around the material was similar at 6 weeks and 12 weeks, with or without prior treatment with bone marrow. The remaining material showed close contact with the muscle, and blood vessels penetrated the material in both groups. Wide bundles of collagen were embedded around the apatite particles, more at the 12-week time point. No bone formation was found, either at 6 weeks or 12 weeks, and scanning electron microscopy showed that the calcium sulfate phase was resorbed after 6 weeks with the calcium phosphate phase remaining intact. Micro-computed tomography showed significantly more hydroxyapatite at 6 weeks than after 12 weeks.

Conclusion

Calcium sulfate hydroxyapatite bone substitute can be used as a carrier for antibiotics or other drugs, without adverse reaction due to the fast resorption of the calcium sulfate. No bone formation was seen despite treating the bone substitute with autologous bone marrow.

Study of in Vitro and in Vivo Bone Formation in Composite Cryogels and the Influence of Electrical Stimulation

This work studies osteoinduction and bone conduction in polyvinyl alcohol-tetraethylorthosilicate-alginate-calcium oxide (PTAC) biocomposite cryogels along with the synergistic effect of electrical stimulation. In vitro osteoinduction of C2C12 myoblast towards osteogenic lineage is demonstrated through alkaline phosphatase assay, scanning electron microscopy and energy dispersive X-ray spectroscopy. These results were followed by in vivo implantation studies of PTAC biocomposite cryogel scaffolds in the bone conduction chamber model depicting bone formation after 24 days based on immunohistological staining for osteogenic markers, i.e., collagen type I (Col I), osteocalcin (OCN), osteopontin (OPN) and bone sialoprotein (BSP). Further, osteogenic differentiation of murine mesenchymal stem cells was studied with and without electrical stimulation. The q-PCR analysis shows that the electrically stimulated cryogels exhibit ~ 6 folds higher collagen type I and ~ 10 folds higher osteopontin mRNA level, in comparison to the unstimulated cryogels. Thus, PTAC biocomposite cryogels present osteoinductive and osteoconductive properties during in vitro and in vivo studies and support osteogenic differentiation of mesenchymal stem cells under the influence of electrical stimulation.

Characterising bone material composition and structure in the ovariectomized (OVX) rat model of osteoporosis

The ovariectomized (OVX) rat model is well established in investigations of osteoporosis and osteoporotic therapies. Advent of techniques such as Fourier-transform infrared (FTIR) spectroscopy and small angle X-ray scattering (SAXS) facilitate characterization of bone composition and mineral structure, respectively, which are key determinants of bone strength. Limited publications exist on the implementation of these techniques in the OVX rat model. At 12 weeks of age, female Sprague-Dawley rats were either sham-operated (n = 6) or ovariectomized (n = 6) and sacrificed 18 weeks later. L2 lumbar vertebrae and proximal tibiae were assessed by µCT, FTIR and SAXS. Presence of extensive trabecular deterioration in the µCT data confirmed the onset of osteoporosis. FTIR compositional parameters were determined including measures of degree of mineralization, crystallinity, collagen maturity and acid phosphate content. Mineral crystal thickness was determined from the SAXS data using two approaches available in literature. Compositionally, a decline in the heterogeneity of acid phosphate content was observed while measures of crystallinity and collagen maturity remained unaltered. Using an iterative curve fitting method, OVX-induced increases in the mineral crystal thickness of 3.8 and 7.8 % (p < 0.05) were noted in the trabecular of the vertebra and tibia, respectively. In conclusion, implementation of FTIR and SAXS techniques in the OVX rat model, identified no significant compositional changes while substantiating thickening of the mineral crystals as a general structural feature of OVX-induced osteoporosis in rats.

Cell factory-derived bioactive molecules with polymeric cryogel scaffold enhance the repair of subchondral cartilage defect in rabbits

We have explored the potential of cell factory-derived bioactive molecules, isolated from conditioned media of primary goat chondrocytes, for the repair of subchondral cartilage defects. Enzyme-linked immunosorbent assay (ELISA) confirms the presence of transforming growth factor-β1 in an isolated protein fraction (12.56 ± 1.15 ng/mg protein fraction). These bioactive molecules were used alone or with chitosan-agarose-gelatin cryogel scaffolds, with and without chondrocytes, to check whether combined approaches further enhance cartilage repair. To evaluate this, an in vivo study was conducted on New Zealand rabbits in which a subchondral defect (4.5 mm wide × 4.5 mm deep) was surgically created. Starting after the operation, bioactive molecules were injected at the defect site at regular intervals of 14 days. Histopathological analysis showed that rabbits treated with bioactive molecules alone had cartilage regeneration after 4 weeks. However, rabbits treated with bioactive molecules along with scaffolds, with or without cells, showed cartilage formation after 3 weeks; 6 weeks after surgery, the cartilage regenerated in rabbits treated with either bioactive molecules alone or in combinations showed morphological similarities to native cartilage. No systemic cytotoxicity or inflammatory response was induced by any of the treatments. Further, ELISA was done to determine systemic toxicity, which showed no difference in concentration of tumour necrosis factor-α in blood serum, before or after surgery. In conclusion, intra-articular injection with bioactive molecules alone may be used for the repair of subchondral cartilage defects, and bioactive molecules along with chondrocyte-seeded scaffolds further enhance the repair. Copyright © 2015 John Wiley & Sons, Ltd.

Arthroscopically diagnosed scapholunate ligament injuries associated with distal radial fractures: a 13- to 15-year follow-up

PURPOSE

To evaluate the natural history of untreated complete or partial scapholunate (SL) ligament tears associated with displaced distal radius fractures.

METHODS

Between 1995 and 1997, 51 consecutive patients aged < 60 years with displaced distal radius fractures were examined arthroscopically to assess for concomitant soft tissue injuries. Thirty-two of 51 patients had an SL ligament tear, 10 had a complete tear (Lindau grade 3), and 22 had a partial tear (Lindau grades 1 and 2). Thirty-two patients had AO type-C fractures, 3 had type-B fractures, and 16 had type-A fractures. In 2010, 47 of the 51 patients were still alive, and they were invited for an interview, clinical examination, and radiography.

RESULTS

Thirty-eight of the 51 original patients participated in the long-term follow-up. Mean grip strength was 83% relative to the contralateral hand in patients with a complete tear, as compared with 92% in patients with partial or no SL tears (nonsignificant). Median Disabilities of the Arm, Shoulder, and Hand questionnaire score was 2 (range, 0‒55) for complete SL tears, compared with 9 (range, 0‒70) for the others (nonsignificant). No differences were found regarding visual analog scale pain or wrist motion/forearm rotation. None of the patients developed a static SL dissociation or a SL advanced collapse wrist.

CONCLUSIONS

No major differences were found in the subjective, objective, or radiographic outcome after a complete (grade 3) or partial (grade 1 or 2) SL untreated tear associated with displaced distal radius fracture. It should be noted that none of the patients had a grade 4 SL tear, which may have a different outcome.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

The masquelet induced membrane technique with BMP and a synthetic scaffold can heal a rat femoral critical size defect

Long bone defects can be managed by the induced membrane technique together with autologous bone graft. However, graft harvest is associated with donor site morbidity. This study investigates if a tricalcium phosphate hydroxyapatite scaffold can be used alone or in combination with bone active drugs to improve healing. Sprague Dawley rats (n = 40) were randomized into four groups. (A) scaffold, (B) BMP-7, (C) BMP-7 + scaffold, and (D) BMP-7 + scaffold + systemic bisphosphonate at 2 weeks. Locked femoral nailing was followed by 6 mm segment removal and implantation of an epoxy spacer. At 4 weeks, the spacers were removed and the defects grafted. Eleven weeks later, the bones were explanted for evaluation with radiography, manual assessment, micro-CT, histology, and Fourier Transform Infrared spectroscopy (FTIR). Isolated scaffolds (A) did not heal any defects, whereas the other treatments led to healing in 7/10 (B), 10/10 (C), and 9/10 (D) rats. Group D had greater volume of highly mineralized bone (p < 0.01) and higher bone volume fraction (p < 0.01) compared to all other groups. A synthetic scaffold + BMP-7 combined with a bisphosphonate improved the callus properties in a rat femoral critical size defect, compared to both BMP-7 and scaffold alone or the two combined.

Characterizing the composition of bone formed during fracture healing using scanning electron microscopy techniques

About 5-10% of all bone fractures suffer from delayed healing, which may lead to non-union. Bone morphogenetic proteins (BMPs) can be used to induce differentiation of osteoblasts and enhance the formation of the bony callus, and bisphosphonates help to retain the newly formed callus. The aim of this study was to investigate if scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) can identify differences in the mineral composition of the newly formed bone compared to cortical bone from a non-fractured control. Moreover, we investigate whether the use of BMPs and bisphosphonates-alone or combined-may have an effect on bone mineralization and composition. Twelve male Sprague-Dawley rats at 9 weeks of age were randomly divided into four groups and treated with (A) saline, (B) BMP-7, (C) bisphosphonates (Zoledronate), and (D) BMP-7 + Zoledronate. The rats were sacrificed after 6 weeks. All samples were imaged using SEM and chemically analyzed with EDS to quantify the amount of C, N, Ca, P, O, Na, and Mg. The Ca/P ratio was the primary outcome. In the fractured samples, two areas of interest were chosen for chemical analysis with EDS: the callus and the cortical bone. In the non-fractured samples, only the cortex was analyzed. Our results showed that the element composition varied to a small extent between the callus and the cortical bone in the fractured bones. However, the Ca/P ratio did not differ significantly, suggesting that the mineralization at all sites is similar 6 weeks post-fracture in this rat model.

Ten years' experience with a pyrocarbon prosthesis replacing the proximal interphalangeal joint. A prospective clinical and radiographic follow-up

We prospectively assessed the subjective, objective, and radiographic results at 1, 2, and 5 years in 65 patients who had pyrocarbon proximal interphalangeal prostheses inserted between 2001 and 2010. Further operations were done on 10 of the 89 joints (four for prosthetic extraction and arthrodesis, two for component changes, and four for soft tissue procedures). At 1 year, the visual analogue scale score for pain at rest had improved to 0 cm from a pre-operative 4 cm, pain at activity from 6 to 1.8 cm, and Disability of the Arm, Shoulder and Hand score from 40 to 25. Range of movement and grip strength were unchanged. At 5 years, 31 joints (21 patients) had a complete radiographic follow-up. Seven proximal and 12 distal components showing zones of osteolysis at 1 year had stabilized and were inert or integrated at 5 years. Three proximal and three distal components had osteolytic zones at 5 years. Forty-seven of 59 patients were pain-free at rest at 1 year, and 19 of 21 at 5 years. No late revisions or loosening occurred.

The composite of hydroxyapatite and calcium sulphate: a review of preclinical evaluation and clinical applications

Recent publications have shown that the combination of α-calcium sulfate hemihydrate, the densest form of hydrates and hydroxyapatite (HA) particles gives good clinical outcome in various applications. It has large potential as bone substitute since the material transforms to bone throughout the entire volume and not only by creeping substitution, from the surface toward the inside. Release of important proteins for osteogenesis has been observed around implanted material and is speculated to be due to fast dissolution of the calcium sulfate phase in combination with the osteoconductive and bioactive nature of HA. In diabetic foot infection, the osteoconductive HA/calcium sulfate material has been successfully used loaded with antibiotics and since it is injectable, the application is minimally invasive, easy and precise. It is a bone substitute for the future.

Influence of systemic bisphosphonate treatment on mechanical properties of BMP-induced calluses in a rat fracture model: comparison of three-point bending and twisting test

The combination of autograft, BMP and bisphosphonate has been shown to produce strong calluses. In this study, without autograft we investigate the effect of bisphosphonate treatment on BMP-induced calluses, both in bending and in rotation. Sprague-Dawley rats (n = 42) underwent femoral osteotomy and BMP-7 treatment. At 2 weeks an injection of saline or bisphosphonate was administered. The animals were sacrificed after 6 weeks. Both femurs were tested in either three-point bending or twisting. All femurs healed. BMP + bisphosphonate-treatment led to larger calluses (p < 0.05) and in three-point bending, higher ultimate force (p < 0.01) and greater stiffness (p < 0.05) than BMP alone. The BMP + bisphosphonate group was nearly 60% stronger than controls, while the BMP group did not reach the strength (p < 0.05) nor stiffness (p < 0.01) of the controls. In the twisting test, similar trends were found but less pronounced. Three-point bending produced transverse callus associated fractures, whereas the twisting test produced spiral fractures, located in the structurally weaker distal femur. BMP + bisphosphonate-treatment produces calluses that are mechanically superior to calluses induced by BMP alone, when tested both in three-point bending and in twisting. For the mechanical evaluation of pharmacologically enhanced calluses with breaking strengths exceeding the native bone, the bending test is recommended.

Evaluation of composition and mineral structure of callus tissue in rat femoral fracture

Callus formation is a critical step for successful fracture healing. Little is known about the molecular composition and mineral structure of the newly formed tissue in the callus. The aim was to evaluate the feasibility of small angle x-ray scattering (SAXS) to assess mineral structure of callus and cortical bone and if it could provide complementary information with the compositional analyses from Fourier transform infrared (FTIR) microspectroscopy. Femurs of 12 male Sprague-Dawley rats at 9 weeks of age were fractured and fixed with an intramedullary 1.1 mm K-wire. Fractures were treated with the combinations of bone morphogenetic protein-7 and/or zoledronate. Rats were sacrificed after 6 weeks and both femurs were prepared for FTIR and SAXS analysis. Significant differences were found in the molecular composition and mineral structure between the fracture callus, fracture cortex, and control cortex. The degree of mineralization, collagen maturity, and degree of orientation of the mineral plates were lower in the callus tissue than in the cortices. The results indicate the feasibility of SAXS in the investigation of mineral structure of bone fracture callus and provide complementary information with the composition analyzed with FTIR. Moreover, this study contributes to the limited FTIR and SAXS data in the field.

Investigating the synergistic efficacy of BMP-7 and zoledronate on bone allografts using an open rat osteotomy model

Bone grafts are well-established in the treatment of fracture non-unions but union is still not always achieved. Harvesting autograft is associated with donor site morbidity and the available amount of bone is limited. Allograft is more easily obtained and available in greater quantities but lacks the osteoinductive characteristics of autograft. We have previously shown a synergistic effect of bone morphogenetic protein (BMP-7), systemic bisphosphonates and autograft. In the present study we hypothesized that the combination of allograft+BMP-7+systemic ZA is more effective than autograft alone, which is currently the most frequently used aid in augmenting fracture and non-union healing. Femoral osteotomies were performed on 82 male Sprague Dawley rats and fixed with intramedullary K-wires. The rats were randomized into 7 groups: (i) saline, (ii) autograft, (iii) allograft, (iv) allograft+BMP-7, (v) autograft+zoledronate (ZA), (vi) allograft+ZA and (vii) allograft+BMP-7+ZA. Autografts were harvested from the contralateral tibia. Allografts were obtained from donor rats and frozen. BMP-7 was administered locally in the form of a putty placed circumferentially around the osteotomy. At 2 weeks, the rats were injected with a single dose of either saline or ZA. The rats were sacrificed at 6 weeks and the femurs were evaluated using radiography, histology, μCT and three-point bending tests. Complete radiological healing was seen in all rats in the BMP-7 groups. The callus volume was larger and the calluses were denser with allograft+BMP-7+ZA than in all other groups (μCT, p<0.001). Mechanical testing yielded a substantially higher peak force with the allograft+BMP-7+ZA combination than all other groups (p<0.01, p<0.001). This was further reinforced in the 59% increase in the peak force observed in the osteotomized femurs of the allograft+BMP-7+ZA group compared to the control femurs (p<0.01), whereas significant decreases of 22-27% were observed in the saline or bone-graft alone groups (p<0.01, p<0.05). Thus our results suggest that allograft combined with the anabolic effect of BMP-7 and the anti-catabolic effect of zoledronate is more efficient than autograft alone.

The natural course of spontaneous osteonecrosis of the knee (SPONK): a 1- to 27-year follow-up of 40 patients

BACKGROUND AND PURPOSE

Spontaneous osteonecrosis of the knee (SPONK) is a painful lesion in the elderly, frequently leading to osteoarthritis and subsequent knee surgery. We evaluated the natural course and long-term consequences of SPONK in terms of need for major knee surgery.

METHODS

Between 1982 and 1988, 40 consecutive patients were diagnosed with SPONK. The short-term outcome has been reported previously (1991). After 1-7 years, 10 patients had a good radiographic outcome and 30 were considered failures, developing osteoarthritis. In 2012, all 40 of the patients were matched with the Swedish Knee Arthroplasty Register (SKAR) and their medical records were reviewed to evaluate the long-term need for major knee surgery.

RESULTS

At the 2012 review, 33 of the 40 patients had died. The mean follow-up time from diagnosis to surgery, death, or end of study was 9 (1-27) years. 17 of 40 patients had had major knee surgery with either arthroplasty (15) or osteotomy (2). All operated patients but 1 were in the radiographic failure group and had developed osteoarthritis in the study from 1991. 6 of 7 patients with large lesions (> 40% of the AP radiographic view of the condyle) at the time of the diagnosis were operated. None of the 10 patients with a lesion of less than 20% were ever operated.

INTERPRETATION

It appears that the size of the osteonecrotic lesion can be used to predict the outcome. Patients showing early signs of osteoarthritis or with a large osteonecrosis have a high risk of later major knee surgery.

The effect of a biphasic injectable bone substitute on the interface strength in a rabbit knee prosthesis model

Background

In joint prosthetic surgery, various methods are used to provide implant stability. We used an injectable bone substitute, composed of calcium sulfate/hydroxyapatite, as bone defect filler to stabilize a tibia prosthesis in an experimental rabbit model. The aim of the study was to investigate and compare the stability of prosthetic fixation with and without the use of an injectable bone substitute.

Methods

Sixteen rabbits were used and the tibia prostheses were implanted bilaterally, one side with the prosthesis alone and the other side with the prosthesis and calcium sulfate/hydroxyapatite (Cerament™). The rabbits were randomly divided into two groups and euthanized after 6 and 12 weeks, respectively. The prosthesis was extracted measuring the pull-out force in an Instron tester, and the bone surrounding the former prosthesis site was analyzed by histology, histomorphometry, and micro-computed tomography.

Results

At 6 weeks no difference in maximum pull-out force was found between the prostheses fixed with or without Cerament™. At 12 weeks the maximum pull-out force for the prostheses with Cerament™ was significantly higher than that for the prostheses without Cerament™ (p = 0.04). The maximum pull-out force at 12 weeks was significantly higher than that at 6 weeks for the prostheses fixed with Cerament™ (p = 0.03) but not for the prostheses without.

Conclusion

We conclude that early prosthesis-bone interface strength is not influenced by a bone substitute. However, during remodeling, the bone substitute might provide improved mechanical support for the prosthesis. The results support further studies of the use of injectable calcium sulfate/hydroxyapatite in fixation of prosthetic joint implants.

Augmentation of autologous bone graft by a combination of bone morphogenic protein and bisphosphonate increased both callus volume and strength

BACKGROUND AND PURPOSE

Bone morphogenic proteins (BMPs) can be used in non-unions to replace autograft. BMPs induce osteoblasts and (less well known) also osteoclasts, which can in turn be controlled by a bisphosphonate. In the present study, our aim was to improve the biological effect of autologous bone graft by adding an anabolic BMP, with or without bisphosphonates, in an open-fracture model prone to non-union.

METHODS

Rat femurs were osteotomized and fixed with an intramedullary K-wire. Autograft was placed at the osteotomy, mixed with either saline or BMP-7. After 2 weeks, the rats had a single injection of saline or of a bisphosphonate (zoledronate). The rats were killed after 6 weeks and the femurs were evaluated by radiography, micro-CT, histology, and 3-point bending test.

RESULTS

All fractures healed. The callus volume was doubled in the BMP-treated femurs (p < 0.01) and increased almost 4-fold in the femurs treated with both BMP and systemic zoledronate (p < 0.01) compared to autograft. In mechanical testing, the autograft group reached approximately half the strength of the contralateral, non-osteotomized femur (p < 0.001). By adding BMP to the autograft, the strength was doubled (p < 0.001) and with both BMP and systemic zoledronate, the strength was increased 4-fold (p < 0.001) compared to autograft alone.

INTERPRETATION

The combination of BMP and bisphosphonate as an adjunct to autograft is superior to autograft alone or combined with BMP. The combination may prove valuable in the treatment of non-unions.

Local treatment of a bone graft by soaking in zoledronic acid inhibits bone resorption and bone formation. A bone chamber study in rats

Background

Bone grafts are frequently used in orthopaedic surgery. Graft remodelling is advantageous but can occur too quickly, and premature bone resorption might lead to decreased mechanical integrity of the graft. Bisphosphonates delay osteoclastic bone resorption but may also impair formation of new bone. We hypothesize that these effects are dose dependent. In the present study we evaluate different ways of applying bisphosphonates locally to the graft in a bone chamber model, and compare that with systemic treatment.

Methods

Cancellous bone grafts were placed in titanium chambers and implanted in the tibia of 50 male rats, randomly divided into five groups. The first group served as negative control and the grafts were rinsed in saline before implantation. In the second and third groups, the grafts were soaked in a zoledronic acid solution (0.5 mg/ml) for 5 seconds and 10 minutes respectively before being rinsed in saline. In the fourth group, 8 μL of zoledronic acid solution (0.5 mg/ml) was pipetted onto the freeze-dried grafts without rinsing. The fifth group served as positive control and the rats were given zoledronic acid (0.1 mg/kg) systemically as a single injection two weeks after surgery. The grafts were harvested at 6 weeks and analysed with histomorphometry, evaluating the ingrowth distance of new bone into the graft as an equivalent to the anabolic osteoblast effect and the amount (bone volume/total volume; BV/TV) of remaining bone in the remodelled graft as equivalent to the catabolic osteoclast effect.

Results

In all chambers, almost the entire graft had been revascularized but only partly remodelled at harvest. The ingrowth distance of new bone into the graft was lower in grafts soaked in zoledronic acid for 10 minutes compared to control (p = 0.007). In all groups receiving zoledronic acid, the BV/TV was higher compared to control.

Conclusions

This study found a strong inhibitory effect on bone resorption by bisphosphonates but also a limited inhibition of the ingrowth of new bone. Local treatment at surgery resulted in stronger inhibition of both resorption and bone formation compared to systemic treatment.

Treatment of spontaneous osteonecrosis of the knee (SPONK) by a bisphosphonate

BACKGROUND AND PURPOSE

Primary spontaneous osteonecrosis of the knee is a painful lesion in the elderly without any known cause. The onset of pain is usually acute. The prognosis is poor with high frequency of osteoarthritis, joint surface collapse, and subsequent knee surgery. In the present study, we determined whether bisphosphonates can prevent the joint surface collapse by delaying the post-necrotic remodeling.

PATIENTS AND METHODS

Between 2006 and 2009, 17 consecutive patients (mean age 68 years) with clinical and radiographic signs of knee osteonecrosis were identified and given alendronate, 70 mg perorally, once a week for a minimum of 6 months. The patients were followed clinically, radiographically, and by MRI.

RESULTS

10 of the 17 patients did not develop osteoarthritis (group A), 4 patients developed mild osteoarthritis but no knee joint surface collapse (group B), and 3 patients had a joint surface collapse (group C). 2 of the 3 patients in group C-as compared to none in the other groups-stopped medication prematurely, due to side effects.

INTERPRETATION

Compared to a previous, untreated series of osteonecrosis patients at our hospital, the clinical results in the present series appeared better. 59% of the patients had a complete radiographic recovery, as compared to 25% in the original study. 12% were failures regarding need to undergo surgery when bisphosphonates were given, as compared to 32% in the previous untreated series. An anticatabolic drug delaying the remodeling might be an effective treatment in osteonecrosis of the knee but further (preferably randomized) studies are necessary.

Individualized outcome measures of daily activities are sensitive tools for evaluating hand surgery in rheumatic diseases

OBJECTIVES

To explore the ability of six outcome measures to capture clinically important changes in patients with rheumatic diseases undergoing hand surgery and to study predictors of changes in activity performance in different patient and surgery strata.

METHODS

A total of 172 patients (median age 59 years, disease duration 18 years) were stratified into subgroups: diagnosis, age, general function, type of surgery. Performance of daily activities and satisfaction were assessed by the Canadian Occupational Performance Measure (COPM). Clinically important improvement was defined as a two-step improvement in COPM. Hand function was assessed by reference to grip strength (Grippit), pinch strength (pinch gauge), hand pain (visual analogue scale) and grip ability (Grip Ability Test). Responsiveness was calculated as effect size (ES) at 6-month follow-up compared with baseline.

RESULTS

Clinically important improvement was reached by 25-69% depending on outcome measure and type of surgery. Improvement was smaller in patients with multiple simultaneous procedures. Regardless of diagnosis, age, general function and type of surgery, patients improved significantly in all measures, with the largest changes in COPM(performance) and COPM(satisfaction) (ES 0.7-1.9). The ES of pain ranged from 0.2 to 0.7, Grippit from 0.1 to 0.5 and pinch gauge from 0.4 to 0.8. Hand pain was the only significant predictor of clinically important improvement of COPM(performance): odds ratio 0.71, 95% CI 0.51, 0.98 (P = 0.041).

CONCLUSION

COPM was the most sensitive instrument to capture clinically important improvement, and hand pain was a significant predictor of improvement, irrespective of diagnosis, age, general functional level and type of surgery.