Although bone morphogenetic protein 2 (BMP-2) has been FDA-approved for spinal fusion for decades, its disadvantages of promoting osteoclast-based bone resorption and suboptimal carrier (absorbable collagen sponge) leading to premature release of the protein limit its clinical applications. Our recent study showed an excellent effect on bone regeneration when BMP-2 and zoledronic acid (ZA) were co-delivered based on a calcium sulphate/hydroxyapatite (CaS/HA) scaffold in a rat critical-size femoral defect model. Therefore, the aim of this study was to evaluate whether local application of BMP-2 and ZA released from a CaS/HA scaffold is favorable for spinal fusion. We hypothesized that CaS/HA mediated controlled co-delivery of rhBMP-2 and ZA could show an improved effect in spinal fusion over BMP-2 alone. 120, 8-week-old male Wistar rats (protocol no. 25-5131/474/38) were randomly divided into six groups in this study (CaS/HA, CaS/HA + BMP-2, CaS/HA + systemic ZA, CaS/HA + local ZA, CaS/HA + BMP-2 + systemic ZA, CaS/HA + BMP-2 + local ZA). A posterolateral spinal fusion at L4 to L5 was performed bilaterally by implanting group-dependent scaffolds. At 3 weeks and 6 weeks, 10 animals per group were euthanized for µCT, histological staining, or mechanical testing. µCT and histological results showed that the CaS/HA + BMP-2 + local ZA group significantly promoted bone regeneration than other treated groups. Biomechanical testing showed breaking force in CaS/HA + BMP + local ZA group was significantly higher than other groups at 6 weeks. In conclusion, the CaS/HA-based biomaterial functionalized with bioactive molecules rhBMP-2 and ZA enhanced bone formation and concomitant spinal fusion outcome

Acknowledgements: Many thanks to Ulrike Heide, Anna-Maria Placht (assistance with surgeries) as well as Suzanne Manthey & Annett Wenke (histology).

A number of techniques have been developed to improve the immediate mechanical anchorage of implants for enhancing implant longevity. This issue becomes even more relevant in patients with osteoporosis who have fragile bone. We have previously shown that a dynamic hip screw (DHS) can be augmented with a calcium sulphate/hydroxyapatite (CaS/HA) based injectable biomaterial to increase the immediate mechanical anchorage of the DHS system to saw bones with a 400% increase in peak extraction force compared to un-augmented DHS. The results were also at par with bone cement (PMMA). The aim of this study was to investigate the effect of CaS/HA augmentation on the integration of a different fracture fixation device (gamma nail lag-screw) with osteoporotic saw bones.

Osteoporotic saw bones (bone volume fraction = 15%) were instrumented with a gamma nail without augmentation (n=8) or augmented (n=8) with a CaS/HA biomaterial (Cerament BVF, Bonesupport AB, Sweden) using a newly developed augmentation method described earlier. The lag-screws from both groups were then pulled out at a displacement rate of 0.5 mm/s until failure. Peak extraction force was recorded for each specimen along with photographs of the screws post-extraction. A non-parametric t-test was used to compare the two groups.

CaS/HA augmentation of the lag-screw led to a 650% increase in the peak extraction force compared with the controls (p<0.01). Photographs of the augmented samples shows failure of the saw-bones further away from the implant-bone interface indicating a protective effect of the CaS/HA material.

We present a novel method to enhance the immediate mechanical anchorage of a lag-screw to osteoporotic bone and it is also envisaged that CaS/HA augmentation combined with systemic bisphosphonate treatment can lead to new bone formation and aid in the reduction of implant failures and re-operations.

Majority of osteoporosis related fractures are treated surgically using metallic fixation devices. Anchorage of fixation devices is sometimes challenging due to poor osteoporotic bone quality that can lead to failure of the fracture fixation.

Using a rat osteoporosis model, we employed neutron tomography and histology to study the biological effects of implant augmentation using an isothermally setting calcium sulphate/hydroxyapatite (CaS/HA) biomaterial with synthetic HA particles as recruiting moiety for systemically administered bisphosphonates. Using an osteoporotic sawbones model, we then provide a standardized method for the delivery of the CaS/HA biomaterial at the bone-implant interface for improved mechanical anchorage of a lag-screw commonly used for hip fracture fixation. As a proof-of-concept, the method was then verified in donated femoral heads and in patients with osteoporosis undergoing hip fracture fixation.

We show that placing HA particles around a stainless-steel screw in-vivo, systemically administered bisphosphonates could be targeted towards the implant, yielding significantly higher peri-implant bone formation compared to un-augmented controls. In the sawbones model, CaS/HA based lag-screw augmentation led to significant increase (up to 4 times) in peak extraction force with CaS/HA performing at par with PMMA. Micro-CT imaging of the CaS/HA augmented lag-screws in cadaver femoral heads verified that the entire length of the lag-screw threads and the surrounding bone was covered with the CaS/HA material. X-ray images from fracture fixation surgery indicated that the CaS/HA material could be applied at the lag-screw-bone interface without exerting any additional pressure or risk of venous vascular leakage.: We present a new method for augmentation of lag-screws in fragile bone. It is envisaged that this methodcould potentially reduce the risk of fracture fixation failure especially when HA seeking “bone active” drugs are used systemically.

There is a lack of carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotic for Staphylococcus aureus deep bone infections (DBIs). RIF is also associated with systemic side effects, and known for causing rapid development of antibiotic resistance when given as monotherapy. We evaluated a clinically usedbi-phasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN). It was hypothesized that this combined approach could provide improved biofilm eradication and prevent the development of RIF resistance.

Methods: 1) Biofilm eradication: Using a modified crystal violet staining biofilm quantification method, the antibiotics released at different time points (Day 1, 3, 7, 14, 21, 28 and 35) from the hemispherical pellets of CaS/HA(500 mg)-VAN (24.57 mg) / GEN (10.35 mg) composites with or without RIF (8.11 mg) were tested for their ability to disrupt the preformed 48-h old biofilms of S. aureus ATCC 25923, and S. aureus clinical strain P-3 in 96-well microtitre plate. For each tested group of antibiotic fractions, five separate wells were used (n=5). 2) Testing for resistance development: Similar to the method mentioned above the 48-h biofilm embeded bacteria exposed to antibiotic fractions from different time points continuously for 7 days. The biofilms remained were then tested for RIF resistant strains of bacteria.

Overall, there was clear antibiofilm biofilm activity observed with CaS/HA-VAN/GEN+RIF combinations compared with CaS/HA-VAN/GEN alone. The S. aureus strains developed resistance to RIF when biofilms were subjected to CaS/HA-RIF alone but not with combinations of CaS/HA-VAN/GEN+RIF

Enhanced antibiofilm effects without development of RIF resistance indicates that biphasic CaS/HA loaded with VAN or GEN could be used as a carrier for RIF for additional local delivery in clinically demanding DBIs.

Acknowledgement: We deeply acknowledge the Royal Fysiographic Society of Lund, Landshövding Per Westlings Minnesfond and the Stina and Gunnar Wiberg fond for financial support.

Aims

There is a lack of biomaterial-based carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotics for bone infections. RIF is also known for causing rapid development of antibiotic resistance when given as monotherapy. This in vitro study evaluated a clinically used biphasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN).

Targeted delivery of drugs is a major challenge in diseases such as infections and tumors. The aim of this study was to demonstrate that hydroxyapatite (HA) particles can act as a recruiting moiety for various bioactive molecules and as a proof-of-concept demonstrate that the affinity of drugs to hydroxyapatite can exert a biological effect. A bisphosphonate, zoledronic acid (ZA), was used as a model drug. Experiment 1 (ZA seeks HA): Calcium sulphate (CaS)/hydroxyapatite (HA) biomaterial pellets (diameter¸=5 mm, height=2 mm) were implanted in the abdominal muscle pouch of rats. After 2-weeks of implantation, a sub-cutaneous injection of 14C-ZA (0.1 mg/kg) was given. 24 h later, the animals were sacrificed and the uptake of ZA determined in the pellets using scintillation counting. Experiment 2 (Systemically administered ZA seeks HA and exerts a biological effect): A fenestrated implant was filled with the CaS/HA biomaterial and inserted in the proximal tibia of rats. 2-weeks post-op, a subcutaneous injection of ZA (0.1 mg/kg) was given. Animals were sacrificed at 6-weeks post-op. Empty implant was used as a control. Peri-implant bone formation was evaluated using different techniques such as micro-CT, mechanical testing and histology. Welch's t-test was used for mechanical testing and Mann-Whitney U test for micro-CT data analysis. Experiment 1: Uptake of radioactive ZA in the CaS/HA biomaterial was confirmed. Almost no ZA was present in the surrounding muscle. These results show high specific binding between systemically administered ZA and synthetic particulate HA. Experiment 2: Significantly higher peri-implant bone was measured using micro-CT in the group wherein the implant contained the CaS/HA biomaterial and ZA was administered systemically (This study presents a method for biomodulating HA in situ by different bioactive molecules. The approach of implanting a biomaterial capable of recruiting systemically given drugs and thereby activate the material is novel and may present a possibility to treat bone infections or tumors.

Bone is a dynamic tissue with a quarter of the trabecular and a fifth of the cortical bone being replaced continuously each year in a complex process that continues throughout an individual’s lifetime. Bone has an important role in homeostasis of minerals with non-stoichiometric hydroxyapatite bone mineral forming the inorganic phase of bone. Due to its crystal structure and chemistry, hydroxyapatite (HA) and related apatites have a remarkable ability to bind molecules. This review article describes the accretion of trace elements in bone mineral giving a historical perspective. Implanted HA particles of synthetic origin have proved to be an efficient recruiting moiety for systemically circulating drugs which can locally biomodulate the material and lead to a therapeutic effect. Bone mineral and apatite however also act as a waste dump for trace elements and drugs, which significantly affects the environment and human health.

Cite this article: Bone Joint Res 2020;9(10):709–718.

Metaphyseal fracture healing is important in joint-adjacent fractures and appears to differ from diaphyseal healing. We recently found that a biomaterial delivering bone morphogenic protein-2 (BMP-2) and zoledronic acid (ZA) healed the metaphyseal bone in a tibial defect but failed closing the cortical defect. In this study we added a BMP-2 soaked collagen membrane to study cortical healing from the muscle tissue surrounding the bone. We used SD rats and a 4.5 mm metaphyseal circular tibial defect. In group 1 (G1), a porous gelatin-calcium sulphate-hydroxyapatite (GCH) biomaterial containing rhBMP-2 and ZA was used to fill the defect (GCH+5 μg BMP-2+10 μg ZA). In group 2 (G2), we used a collagen membrane (2 μg BMP-2) to cover the GCH filled defect (GCH+3μg BMP+10 μg ZA). Group 3 (G3) was an empty control. Animals were sacrificed after 8-weeks and bone regeneration was evaluated with micro-CT and histology. In both G1 (P<0.001) and G2 (p<0.001) a significantly higher mineralized volume was found in the defect compared to empty G3. In G2 higher mineralized volume was found in the cortical region compared to both G1 (p<0.01) and G3 (p<0.001) as seen via micro-CT. Histologically, G1 and G2 showed islands of trabecular bone in the defect peripherally but only G2 showed cortical healing. G3 was empty in the middle but showed healed cortex. In conclusion, GCH can be used to deliver BMP-2 and ZA to promote metaphyseal bone growth. A membrane (CM) doped with low dose BMP-2 improved cortical regeneration.

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions.

Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2.

Background

The doses of local rhBMP-2 in commercially available materials are high with known drawbacks such as inflammation and premature bone resorption. The latter can be prevented by adding bisphosphonates like zoledronic acid (ZA) but systemic ZA has side effects and patient adherence to treatment is low. In a recent study, we have shown that local co-delivery of rhBMP-2 and ZA via a calcium sulphate/hydroxyapatite (CS-HA) biomaterial can be used to regenerate both cortical and trabecular bone in a rat model of metaphyseal bone defect. Even low doses of local ZA in the biomaterial showed promising results and increased bone formation within the defect compared to the controls. A step before clinical translation of the local treatment regimen is to evaluate the in-vivo release kinetics of these additives and thus in this study, we aimed to investigate the in-vivo pharmacokinetics of rhBMP-2 and ZA from the CS-HA biomaterial in a rat abdominal muscle pouch model over a period of 4-weeks.

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.

To demonstrate the role of an antibiotic containing bone substitute, native bone active proteins and muscle transforming into bone.

Recurrent osteomyelitis was eradicated and filled with a gentamycin eluting bone substitute (Cerament™l G) consisting of sulphate and apatite phases and covered by a muscle flap.

A chronic, longstanding, fistulating osteomyelitis was operated with radical eradication and filling of the cavity with gentamycin eluting bone substitute. At one year, the patient had no leg pain and a healed wound. Significant bone was also seen in the overlaying muscle, at one month post-op disappearing after 6-months. Local delivery of gentamycin had a protective effect on bone formation.

Bone substitute with gentamycin leads to differentiation of mesenchymal cells into bone in-vitro.

Introduction: Distal radial fractures are common and sometimes surgery is necessary. The volar locking plate has become the standard solution in the last years in many hospitals but the method is unproven scientifically. In this series we have retrospectively followed our early cases of volar plates.

Patients and Material: We identified all 68 patients (44 women and 9 men) at Lund University Hospital undergoing surgery using the TriMed^® volar fixed-angle plate for distal radius fracture between January 2006 and December 2007. The mean age was 57 years (20–84). The patients were contacted by mail and sent a Quick-DASH, a validated outcome questionnaire. Eleven patients were excluded according to the protocol due to having another concomitant or bilateral fractures or other complicating conditions like stroke or hemiparesis or psychiatric disorder. 53 of the remaining 57 patients completed the Quick-DASH and plotted their subjective function, pain at rest and at activity as well as the cosmetic appearance on a 0–100 mm visual analogue scale (VAS). 50 patients came to the hospital for an additional radiogram and measurement of the range of motion (goniometer) and grip strength (JAMAR).

Results: Quick-DASH median was 4,5 (range 0–80), and mean 14. Seventeen (32%) of the patients had zero for VAS at rest. Ten (19%) had a DASH value of more than 30 implicating a less than satisfying result. Range of motion in de fractured wrists were 91% of the non-fractured and the grip strngth 82% of the contralateral.

Discussion: In the present study the patients regained near full function in their fractured wrists after the operation with the volar locking plate. The ROM of the fractured wrists was 91% of the ROM of the non-fractured wrists, whereas the grip strength of the fractured wrists was 82% compared to the contralateral side. These data are excellent and similar both to previous own results as well as other published studies.

The results of the Quick-DASH questionnaire, representing the subjective perception of the outcome, indicate that the patients are satisfied. Seventeen of the 53 patients scored zero on the DASH, suggesting a full recovery without any sequelae. In the population the median value is 2,5 (Abramo 2008). Ten of the patients had a DASH score over 30, indicating substantial subjective limitations in the daily life. Interestingly, there appears to be little or no correlation between high DASH scores and impaired ROM or grip strength. However, we noted that patients with high DASH scores also tended to score high in the VAS-question regarding subjective pain at activity. It was further noted that the patients with a DASH over 30 had a delay between injury and operation for a mean of 10,3 days (1–19 days) between injury and operation, compared to the patients with a DASH score below 30 who had a mean of 5,6 days (2–16 days) delay.

Purpose: The management of Dorsal Fracture Dislocations of the PIP joint is challenging, especially for the unstable ones. Complications are common and often lead to functional disability. Many treatment methods have been described in the past, illustrating that no optimal solution has been found. In the Hemi-Hamate autograft technique, introduced by Hastings in 1999, a reconstruction of the volar lip joint surface and stabilization of the joint is achieved. This autograft can be seen as a model of a non vascularised bone-cartilage composite graft. The purpose of the present retrospective study was to evaluate the long term results of the hemi-hamate autograft technique in unstable PIP fracture-dorsal dislocations with special reference to posttraumatic degenerative arthritis common in non vascularized joint transfers.

Materials and Methods: We report the results of 9 patients operated between November 2002 and March 2008 and with a minimum follow up of 26 months. The mean follow-up time was 56 months. There were 6 men and 3 women with a mean age at operation of 45 years (23–66). All fractures were unstable with comminution of the volar lip. In 3 patients the dominant hand was involved. The middle finger was injured in 4 patients, the ring finger in 4 and the little finger in 1 patient. All patients were treated with the operation technique described by Hastings and reanalyzed by Williams. The volar base of middle phalanx was debrided and reconstructed by a pre-sized autograft harvested from the dorsal side of the homolateral hamatum, and fixed with mini screws. A standard rehabilitation program was used postoperatively. Clinical (ROM, grip strength), radiographic and subjective outcomes (VAS) were examined in all patients.

Results: At the last follow up, the injured finger had an average active ROM at the MCP joints of 97o (90o–115o) at the PIP 69 o (45 o –95 o) and at the DIP 59 o (30 o –90 o). The extension lag in the PIP joints were mean 10 o (0 o –30 o). Grip strength of the injured hand was mean 89% of the uninjured contralateral side. On radiographs, severe arthritis in the treated PIP was found in 2 of 9 patients. Another 2 patients had degenerative arthritis in several PIP. The average subjective score of patient’s satisfaction was 85 (20–100) in a scale 0–100 (100 best).

Conclusions: The Hemi-Hamate autograft technique is a technically demanding operation but an alternative to arthrodesis or primary joint arthroplasty in the treatment of Fracture-Dorsal Dislocations of PIP joint. Our results are good and comparable to previously reported results (Williams 2001). Some deterioration will occur regarding joint osteoarthritis but a high degree of subjective patient satisfaction was found. Further studies and methods to decrease the osteoarthritis would be preferential.

Introduction: The choice of whether to use absorbable or non-absorbable suture in the closure of wounds following hand or upper limb surgery is usually surgeon dependent. In our unit both continuous absorbable subcutaneous suture and interrupted non-absorbable suture are utilised. The use of absorbable sutures offers a potential advantage to the patient and clinician in not requiring a clinic appointment for suture removal. The quality and aesthetic appearance of hand and upper limb surgical scars are of great importance to patients. Few studies have compared the aesthetic appearance of scars following the use of absorbable and non-absorbable suture in hand and upper limb surgical wound closure.

Method: 50 consecutive patients having undergone day case hand surgery between August 2007 and May 2008 with absorbable suture wound closure were identified along with 50 consecutive patients over the same time period who underwent non-absorbable wound closure. Each was sent a questionnaire comprising a visual analogue scale (VAS) for wound satisfaction, a validated 6 point patient scar assessment tool and the short version of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH).

Results: 100 patients were contacted by post and 70 responses were received (37 absorbable, 33 non-absorbable). Both groups had undergone a similar spectrum of procedures including carpal tunnel decompression, Dupuytrens fasciectomy, excision of lesions and trigger finger release. Age, sex and QuickDASH scores were not significantly different between groups. Mean VAS was not significantly different between groups (Non-absorbable group 82.4 (95% CI 74.7–90.2) Absorbable group 80.4 (95% CI 71.9–89.0)). No significant difference was found between groups in terms of pain, itching, scar colour, stiffness, thickness or irregularity.

Conclusion: No significant difference in aesthetic appearance of scars exists following the closure of hand and upper limb wounds with either absorbable or non-absorbable suture. Either suture material can be used with confidence with respect to aesthetic outcome.

The influence of the mechanical environment on tissue differentiation has been widely investigated. However many questions remain about the actual process and the parameters that govern it. It has been proposed that tissue differentiation is driven by a biophysical stimulus which is a combination of fluid flow and octahedral shear strain. In order to further investigate the influence of the mechanical environment on tissue differentiation we have tested this hypothesis within a mechanically controlled bone chamber.

The bone chamber consists of a titanium cylinder with two bone ingrowth openings at one end which allow tissue to grow in from the subcortical cancellous bone. It is equipped with a piston protruding into the chamber for the application of a known pressure to the ingrowth tissue.

A 3D poroelastic finite element model of the inside of the bone chamber was developed. To model the dispersal of the various cell populations inside the tissue a lattice was created within each finite element, representing a space for both the cell and extracellular matrix. The differentiation process was ruled by fluid flow and shear strain. The change in tissue phenotype was implemented through a change in mechanical properties. Loading conditions corresponded to those applied during conducted experiments

High fluid flow and shear strain at the top and bottom of the chamber favoured tissue differentiation towards fibrous tissue. In the middle region, bone formed. A cartilage layer between the bone and the fibrous tissue was predicted, which is qualitatively in agreement with the experiments.

Although acceptable simulation/experiment comparison is achieved, in reality great variation is found in experiments, whereas our simulations are deterministic. It is clear that deterministic simulations can not capture the nature of tissue differentiation in this chamber. Nonetheless, tissue differentiation algorithms based on fluid/strain stimuli and using lattice models for biological activity are a promising tool in their ability to predict tissue differentiation inside a mechanically-controlled bone chamber.