We developed a novel silorane-based biomaterial (SBB) for use as an orthopedic cement. SBB is comprised of non-toxic silicon-based monomers, undergoes non-exothermic polymerization, and has weight-bearing strength required of orthopedic cements. We sought to compare the antibiotic release kinetics of this new cement to that of commercially available PMMA bone cement. We also evaluated each material's inherent propensity to support the attachment of bacteria under both static and dynamic conditions. One gram of either rifampin or vancomycin was added to 40g batches of PMMA and SBB. Pellets were individually soaked in PBS. Eluate was collected and tested daily for 14 days using HPLC. Compressive strength and modulus were tested over 21 days. Bioassays were used to confirm the bioactivity of the antibiotics eluted. We measured the growth and maturation of staphylococcus aureus (SA) biofilm on the surface of both PMMA and SBB disks over the course of 72 hours in a static well plate and in a dynamic biofilm reactor (CDC Biofilm Reactor). N=4 at 24, 48, and 72 hours. A luminescent strain of SA (Xen 29) was employed allowing imaging of bacteria on the discs. SBB eluted higher concentrations of vancomycin than did PMMA over the course of 14 days (p<0.001). A significant 55.1% greater day 1 elution was observed from SBB. Silorane cement was able to deliver rifampin in clinically favorable concentrations over 14 days. On the contrary, PMMA was unable to deliver rifampin past day 1. The incorporation of rifampin into PMMA severely reduced its mechanical strength (p<0.001) and modulus (p<0.001). Surface bacterial radiance of PMMA specimens was significantly greater than that of SBB specimens at all time points (p<0.05). The novel silorane-based cement demonstrated superior antibiotic release and, even without antibiotic incorporation, demonstrated an innate inhabitation to bacterial attachment and biofilm

Aims. Poly(methyl methacrylate) (PMMA)-based bone cements are the industry standard in orthopaedics. PMMA cement has inherent disadvantages, which has led to the development and evaluation of a novel silorane-based biomaterial (SBB) for use as an orthopaedic cement. In this study we test both elution and mechanical properties of both PMMA and SBB, with and without antibiotic loading. Methods. For each cement (PMMA or SBB), three formulations were prepared (rifampin-added, vancomycin-added, and control) and made into pellets (6 mm × 12 mm) for testing. Antibiotic elution into phosphate-buffered saline was measured over 14 days. Compressive strength and modulus of all cement pellets were tested over 14 days. Results. The SBB cement was able to deliver rifampin over 14 days, while PMMA was unable to do so. SBB released more vancomycin overall than did PMMA. The mechanical properties of PMMA were significantly reduced upon rifampin incorporation, while there was no effect to the SBB cement. Vancomycin incorporation had no effect on the strength of either cement. Conclusion. SBB was found to be superior in terms of rifampin and vancomycin elution. Additionally, the incorporation of these antibiotics into SBB did not reduce the strength of the resultant SBB cement composite whereas rifampin substantially attenuates the strength of PMMA. Thus, SBB emerges as a potential weight-bearing alternative to PMMA for the local delivery of antibiotics. Cite this article: Bone Joint Res 2021;10(4):277–284

Introduction Polymethylmethacrylate (PMMA) has been widely used in orthopaedic procedures for fixation of joint replacements or enhancing the fixation of implants. However, the use of PMMA has been associated with cardiovascular deterioration and even death. More recently, PMMA has also been used for augmenting osteoporotic vertebral bodies which have fractured or are at risk of fracture. The main complication is PMMA leakage into adjacent structures. Transient hypotension and fatal fat embolism (FE) have also been reported. The pathomechanism of cardiovascular deterioration after the injection of PMMA (i.e. FE) remains a highly controversial subject. The exact role of PMMA in the development of FE remains unclear. The aim of the present study was to elucidate the acute effects of injecting PMMA compared with bone wax into vertebral bodies on the cardiovascular system using an established animal model for vertebroplasty (VP) (Aebli, N, et al. Spine. 2002). Methods In 8 skeletally mature mixed-bred ewes (2–4 years) 6.0ml PMMA (CMW3-Depuy) or bone wax (Bone Wax, Ethicon) were injected unilaterally, through an open approach into the L1 & L2 pedicles. Blood pressure, heart rate, and cardiac output were measured. Results The major difference between the cardiovascular response of the PMMA and that of the bone wax group was the recovery in Pulmonary Artery Pressure (PAP) and Pulmonary Vascular Resistance (PVR). Three minutes post-injection, PAP had fully recovered to baseline values in the wax group. However in the PMMA group, PAP had only recovered by 52% after 3 min and fully recovered after 10 min. Discussion The augmentation of vertebral bodies resulted in transient cardiovascular changes regardless of the material used. However, the recovery of PAP and PVR values took significantly longer with the PMMA group. The peak response was a result of pulmonary vasoconstriction triggered by a reflex reaction to the embolisation of bone marrow particles or by vasoactive cytokines. The peak response was therefore mainly associated with the increase in intraosseous pressure during the augmentation causing release of bone marrow contents into the and not the cement monomer. The cement monomer however plays a role in the cardiovascular complications during FE. The delayed recovery of PAP and PVR in the PMMA group may be due to a vasoconstriction effect of the cement monomer on the pulmonary vascular system. Potentially serious cardiovascular complications may occur during VP regardless of the material used. The injection of PMMA may cause prolonged pulmonary hypertension during vertebro- and also arthroplasty. Continuous invasive cardiovascular monitoring may be required in patients with impaired cardiovascular and pulmonary function

Thermal damage to bone related to the exothermic polymerisation of bone cement (PMMA) remains a concern. A series of studies were conducted to examine PMMA bone interface during cemented arthroplasty. In vitro and in vivo temperature distributions were performed in the laboratory and human and animal surgery. In vivo (10 patients) measurements of cement temperature during cementing of BHR femoral prosthesis using thermocouples. Intra-operative measurement of cement temperature in BHR in the presence of femoral head cysts was examined in patients. The BHR femoral heads were sectioned to assess cement mantle as well as position of thermocouples. An additional study was performed in sheep with PMMA implanted into cancellous defects. Thermocouples were used to monitor temperature in the cement as well as adjacent bone. Histology and CT was used to assess any thermal damage. The exothermic reaction of PMMA during polymerization does indeed result in an increase in temperature at the interface with bone. The in vivo study recorded a maximum temperature of 49.12C for approximately three minutes in the cancellous bone underneath the BHR prosthesis. This exposure is probably not sufficient to cause significant injury to the femoral head. The maximum temperature of the cement on the surface of the bone was 54.12C, whereas the maximum recorded in the cement in the mixing bowl was 110.2C. In the presence of artificial cysts within the bone, however, temperatures generated within the larger cysts, and even at the bone-cement interface of these cysts, reached levels greater than those previously shown to be harmful to bone. This occurred in one case even in the 1 cc cyst. Routine histology revealed a fibrous layer at the cement bone interface in the sheep study. Fluorescent microscopy demonstrated bone label uptake adjacent to the defect site. Histology did not reveal thermal necrosis in the defects in terms of bony necrosis. CT data was used to measure the amount of PMMA placed into each defect. This analysis revealed a range of volumes that did not seem to influence the histology. The heat of cement polymerisation in resurfacing as performed in our study is not sufficient to cause necrosis. This may reflect the ability of the body to rapidly conduct heat away by acting as a heat sink. The temperature-conducting properties of the metal prosthesis are also likely to be important

Introduction. Temporary use of antibiotic-impregnated polymethylmethacrylate (PMMA) bone cement spacers in two-stage revisions is considered to be standard of care for patients with a chronic infection of a joint replacement. Spacers should be wear resistant and load-bearing to avoid prolonged immobilisation of the patient and to reduce morbidity. Most cement spacers contain barium sulphate or zirconium dioxide as radio-opaque substrate. Both are quite hard materials that may negatively influence the wear behaviour of the spacer. Calcium carbonate is another radio-opaque substrate with lower hardness potentially increasing the wear resistance of the spacer materials. The purpose of the study was to compare a prototype PMMA knee spacer (calcium carbonate loaded) with a commercially available spacer (containing barium sulphate) regarding the wear performance and particle release in a knee wear simulator. Material and Methods. Spacer K (TECRES, Italy) was used as barium sulphate (10%) containing spacer material. A prototype material (Heraeaus Medical, Germany) with 15% calcium carbonate was compared. Both were gentamicin impregnated, ready-made for clinical application (preformed) and consist of a tibial and a femoral component. Force-controlled simulation was carried out on an AMTI knee simulator. The test parameters were in accordance to ISO 14243–1 with a 50% reduced axial force (partial weight bearing). Tests were carried out at 37 °C in closed chambers filled with calf serum. Tests were run for 500,000 cycles at a frequency of 1 Hz. For wear analysis, gravimetric wear measurements according to ISO 14243–2 and wear particle analysis according to ASTM F1877–05 were performed. Results. Fig. 1 presents the results of the gravimetric wear measurements. For the Spacer K cement a mean articular wear mass of 375.53±161.22 mg was determined after 500.000 cycles (femoral components: 149.55±17.30 mg, tibial components: 225.98±153.01 mg). The prototype cement showed lower mean total wear of 136.32±37.58 mg (femoral components: 74.32±33.83 mg, tibial components: 61.99±15.74 mg). However, a statistically significant lower wear rate was only seen for the femoral components (p=0,027). In Fig. 2 isolated PMMA wear particles are shown and the morphological characteristics are given in Tab. 1. Discussion and conclusion. The prototype material showed better wear performance in terms of gravimetric wear and particle release. Thus calcium carbonate seems to be a promising material as radio-opaque substrate in PMMA spacers. Nevertheless, the wear amount released from both spacer materials is much higher as compared to conventional total knee replacements with polyethylene inserts. In this context biological reactions against PMMA particles and an increased release of cytokines have been reported in vitro [1] and furthermore, the promotion of osteolysis has been shown in vivo in the presence of PMMA particles [2]. As a clinical consequence we suggest excessive debridement during removal of the cement spacer components to reduce the risk of third body wear for the final joint replacement. Beside the wear performance further studies are essential to prove the mechanical stability and the antibiotic release kinetics for the prototype cement

Introduction and Aims: Polymethylmethacrylate (PMMA) has been widely used in orthopaedic surgery including more recently vertebroplasty. The reported rate of complications following vertebroplasty is low and mainly related to PMMA leakage. The aim of this study was to elucidate the acute cardiovascular effects of PMMA or bone wax in a vertebroplasty animal model. Method: Eight skeletally mature sheep were used and PMMA or bone wax were injected unilaterally into L1 and L2 at 10-minute intervals. Arterial, central venous, pulmonary artery and left ventricular pressures were recorded using Statham pressure transducers and Swan Ganz catheters were used for monitoring cardiac output. Results: Augmentation resulted in a two-phase response regardless of which material was used. First the mean arterial blood pressures started to drop after approximately two seconds. Secondly the pulmonary artery pressure and central venous pressure increased after approximately 11 seconds, whereas cardiac output and left ventricular pressure decreased. There was no significant change in heart rate for both groups. There was a significant difference (p< 0.05) in the pulmonary artery pressure values in the PMMA group compared to the basal values at one, three and five minutes, whereas in the wax group the pulmonary artery pressure recovered within three minutes. Conclusion: Augmentation resulted in a two-phase cardiovascular response regardless of which material was used. Peak responses were similar for both groups, but pulmonary artery pressure and cardiac output recovered quicker in the wax group. The late recovery of pulmonary artery pressure and cardiac output in the PMMA group may be due to a vasoconstriction effect of the cement monomer

Aims: PMMA is currently used as grouting agent of arthroprostheses and for filling of bone cavities after bone curettage. It is moreover used as a carrier of antibiotics in the local treatment of bone infections and it has been proposed as a carrier of antiblastic drugs in the local treatment of bone metastases. The aim of this study is to analyse the biological properties and compressive strenght of PMMA-Methotrexate mixture to be used for the local treatment of bone metastases. Methods: Cylinders of PMMA containing Methotrexate in different concentrations were manufactured according to ASTM F-451. Cylinders of PMMA were used as control. The porosity of the cylinders was characterised by SEM. Drug elution rate in saline solution was measured by HPLC. The biological activity of Methotrexate was analysed on human breast cancer cells using MTT test at different time (from 5 minutes to 30 days). Compressive tests was performed in conformity to ASTM F-451 on PMMA- Methotrexate samples and control as-made and after 30 days of aging in saline. Results: SEM analysis showed the presence of granules of Methotrexate on the surface of as-made cylinders that can be readily released from PMMA cylinders. The release occurred in large amount within 24 hours after immersion. We observed a relative release rate is more sustained in samples containing the drug in lower concentration. Also the biological activity was time dependent: cell death decreased progressively from 60% at 24 hours to 10% at 30 days. Compressive tests showed no statistical differences between PMMA cylinders containing Methotrexate and controls before and after aging in saline. Conclusions: The results show that PMMA-Metho-trexate may be considered an interesting option in the treatment of bone metastases because cement allows mechanical resistance after bone curettage or resection and Methotrexate improves locally anticancer activity

The pathogenesis of aseptic loosening of total joint prostheses is not clearly understood. Two features are associated with loosened prostheses, namely, particulate debris and movement of the implant. While numerous studies have evaluated the cellular response to particulate biomaterials, few have investigated the influence of movement of the implant on the biological response to particles. Our aim was therefore to test the hypothesis that excessive mechanical stimulation of the periprosthetic tissues induces an inflammatory response and that the addition of particulate biomaterials intensifies this. We allocated 66 adult Beagle dogs to four groups as follows: stable implants with (I) and without (II) particulate polymethylmethacrylate (PMMA) and moving implants with (III) and without (IV) particulate PMMA. They were then evaluated at 2, 4, 6, 12 and 24 weeks. The stable implants were well tolerated and a thin, fibrous membrane of connective tissue was observed. There was evidence of positive staining in some cells for interleukin-6 (IL-6). Addition of particulate PMMA around the stable implants resulted in an increase in the fibroblastic response and positive staining for IL-6 and tumour necrosis factor-alpha (TNF-α). By contrast, movement of the implant resulted in an immediate inflammatory response characterised by large numbers of histiocytes and cytokine staining for IL-1ß, TNF-α and IL-6. Introduction of particulate PMMA aggravated this response. Animals with particulate PMMA and movement of the implant have an intense inflammatory response associated with accelerated bone loss. Our results indicate that the initiation of the inflammatory response to biomaterial particles was much slower than that to gross mechanical instability. Furthermore, when there was both particulate debris and movement, there was an amplification of the adverse tissue response as evidenced by the presence of osteolysis and increases in the presence of inflammatory cells and their associated cytokines

Antibiotic-loaded PMMA spacers are used with increased frequency in two-stage revision arthroplasty. The release of aminoglycosides and vancomycin, the most commonly used antibiotics, is prompt, and concentrations are inhibitory. The release kinetic from PMMA bone cement shows a biphasic profile, consisting in an initially high and rapid drug release followed by a slower but sustained phase. However, this general profile of drug release kinetics from PMMA spacers in vitro may have great variability in terms of drug amount, modality, and duration of elution. Initial drug concentration, cement surface area and porosity are essential and well-known factors in determining the drug release. Moreover, viscosity, vacuum-preparation and the different technical characteristics of commercially available spacers are additional factors of variability. Industrial preformed spacers are considered superior to custom-made devices because of uniform mixing and standardized procedures. Spacers produced by different manufacturers vary in their mechanical properties and antibiotic elution characteristics. Small changes in the formulation of a bone cement can also affect these properties. Similar bone cements produced by various brands release different amount of drugs. Gentamicin diffuses from Palacos in a larger amount and for a longer period than from Simplex and CMV. Spacers produced in France (Synicem™) and in Argentina (Subiton™) elute less total amount of gentamicin than those produced in Italy (Spacer G™) and show a delayed peak drug release. The low initial release of antibiotic can contribute to unsatisfactory antimicrobial effect and to the risk of selection of resistant bacteria. Some spacers release gentamicin for longtime (months), while others release antibiotic for only two weeks. In the last years an evolution of PMMA spacers production occurred and modifications in the polimerization process of cement can increase cement porosity and antibiotic elution from spacers. The current commercial preformed spacers for 10 days elution (Spacer G™, prepared with Cemex HP) release more gentamicin (34.1 mg) than previous models, which were prepared with Cemex SP (16.4 mg). Furthermore, they maintain a high elution rate (1.4–1.6 mg/day after one month). The combination of Gentamicin and Vancomycin mantains an elution pharmacokinetic profile that is superimposable to that of Gentamicin and Vancomycin alone, with synergistic effects against multiresistant bacteria in prosthetic infection site. In conclusion, the antibiotic release from PMMA spacers of various brands is not equivalent. The old elution data are no longer valid for new preparations. Consequently, this additional factor of variability should be considered in clinical practice and literature data utilisation

Introduction. Antibiotic loaded polymethyle methacrylate spacers are commonly used in the management of septic hip replacements. Aim. The aim of this study was to determine wear patterns on the articulating surfaces of these spacers, as well as to determine the extent of PMMA particulate debris generation. Method. We took tissue specimens around the acetabulae in 12 cases at the time of the second stage procedure for septic total hip revisions. These were subjected to histological analysis to determine the extent of PMMA particulate debris contamination. We also performed a basic explant retrieval analysis of the articulating surfaces of the PMMA spacers to determine any specific wear patterns. Results. We found numerous PMMA particles in the acetabular soft tissues biopsied. The particle concentration was highest in the area of the acetabular fovea. We could also demonstrate specific wear patterns on the spacers that could be correlated with the generally mismatched articulating couple between the spacer and the bony acetabulum. We could also demonstrate some boney destruction present in the acetabulum with long-term spacer use. Conclusions. We concluded that significant amounts of PMMA particulate debris are generated by these articulating antibiotic spacers. The total volume of this debris may be determined by specific wear patterns on the spacers’ surfaces. We recommend a thorough debridement to decrease the PMMA particle load generated. Consideration in respect of the bearing surface implanted after the explantation of the PMMA spacer should take into account the effect of the debris on the bearing surfaces. We also make recommendations in respect of the design of these PMMA spacers

Two-stage exchange revision is the gold standard in treating an infected total hip arthroplasty. The new emerging gold standard appears to be using an antibiotic impregnated spacer made from polymethylmeta-crylate (PMMA) bone cement between two stages. However, a consensus has not been reached on the antibiotic to use in the cement and its dose. Vancomycin an aminoglycoside is widely used for this purpose in the PMMA cement in doses such as 3 to 9 gr per 40 gr polymer powder. The purpose of this study was to see if Vancomycin is as effective in safer low doses of 1 gr per 40 gr polymer powder.Between 1997 and 2002, twenty-six patients were treated for an infected hip arthroplasty with a two-stage exchange arthroplasty using a Vancomycin impregnated polymethylmetacrylate (PMMA) bone cement spacer. During the first stage all prosthetic material was removed and after debridement, irrigation an articulating spacer was made from PMMA cement (Surgical Simplex, Howmedica, Rutherford, NJ, USA). One gram of Vancomycin HCl (Vancomycin, Eli Lilly, USA) powder was added to each 40 gr polymer powder prior to curing the cement. After the first stage parenteral antibiotics were administered for six weeks. When erythrocyte sedimentation rate and the CRP returned to a normal level, the patient underwent the second stage were a cementless prosthesis was inserted. Intra-operative cultures and frozen sections obtained during the second stage were negative in all patients indicating successful treatment of the infection. Mean follow up after the second stage was 36 (range 24 to 74) months. Two patients had a reinfection after four months. These two patients were infected with gram-negative micro-organisms. This gave us a 92 percent infection eradication rate at 3 years. None of the patients suffered from Vancomycin related side effects.In this study we used a lower dose (1 gr per 40 gr polymer powder) of Vancomycin in the PMMA spacer instead of the commonly used 3 to 9 gr per 40 gr polymer powder. The reason for this was our concerns for nephrotoxicity and allergic reactions frequently associated with use of Vancomycin. Antibiotics are used in cement spacers as a disinfecting agent and sterilizer of dead spaces. As Vancomycin is highly effective when used in PMMA due to its elution dynamics and thermostability we believed it would be effective even in low doses. In all patients the infection appeared to be cured after the first stage. This was demonstrated with negative intraoperative cultures and frozen sections. However, we had two reinfections in patients that initially were infected with gram-negative organism, which Vancomycin is not as effective. Despite this we were able to sterilize the infected hip with a low dose approach in the first stage. Vancomycin is effective in low dose when used in PMMA cement spacers for infected total hip arthroplasties. This approach will decrease potential serious side effects of Vancomycin

Study Design: Comparative, prospective follow-up study. Objective: Comparison of outcome between patients treated with Percutaneous VertebroPlasty (PVP) using low viscosity PolyMethylMetAcrylate (PMMA) bone cement and patients treated with PVP using medium viscosity PMMA bone cement. Summary of background data. Viscosity is the characterizing parameter of PMMA bone cement, currently the standard augmentation material in PVP, and influences interdigitation and cement distribution inside the vertebral body, injected volume and extravasation, thereby affecting the clinical outcome of PVP. In PVP, low, medium and high viscosity PMMA bone cements are used interchangeably. However, effect of viscosity of cement on clinical outcome in patients with Osteoporotic Vertebral Compression Fractures (OVCFs) has not yet been explicit subject of investigation. Methods: Follow-up was conducted using a 0–10 Pain Intensity Numerical Rating Scale (PI-NRS) and the Short Form 36 (SF-36) Quality of Life (QoL) questionnaire before PVP and at 7 days (PI-NRS only), 1 month, 3 months and 12 months after PVP. Cement leakage was analyzed on direct post-operative CT-scanning. Injected cement volume was measured using a calibrated DICOM-viewer and the degree of interdigitation was assessed. At six and 52 weeks and at suspicion, patients were analyzed for the incidence of new fractures. Results: Thirty consecutive patients received PVP using low viscosity PMMA bone cement (OsteoPal-V. ®. ) for 62 OVCFs, followed by 34 patients who received PVP using medium viscosity PMMA bone cement (Disc-O-Tech. ®. ) for 67 OVCFs. Baseline characteristics were comparable between groups. Viscosity qualification was stated by the manufacturer. results regarding PI-NRS and SF-36 were comparable between both groups. Postoperative comparison of injected cement volume, degree of interdigitation, proportion of bipedicular procedures, incidence of new vertebral fractures and complications revealed no substantial differences between both groups. In the low viscosity group a significantly greater proportion of vertebrae showed cement extravastion (81,0% versus 71,6%, p = 0,029). Multiple logistic analysis revealed no definitive predictive factors for the occurrence of cement leakage (yes/ no) (Odds Ratio [95% CI], P):. Severity (acc to Genant et al): 1.82 [0,69 – 4.89], 0.229. Fracture Type (Genant et al): 1.22 [0.64 – 2.32], 0.550. Injected Volume: 0.98 [0.76 – 1.27], 0.875. Spinal Region: 0.87 [0.48 – 1.55], 0.628. Cement Viscosity: 0.42 [0.16 – 1.10], 0.076. Conclusion: No major differences in clinical outcome after PVP in OVCFs using low and medium viscosity PMMA bone cement were found. Viscosity of PMMA bone cement is likely to influence cement extravastion, although this could not be confirmed

Introduction: Patients with spinal metastases often have patterns of disease requiring both an anterior and posterior surgical decompression and stabilisation. Subtotal spondylectomy and circumferential stabilisation can be safely performed via a single posterior transpedicular approach. Polymethyl-methacrylate bone cement (PMMA) has been widely used in spinal column reconstruction with mixed results. PMMA is a potential means for local drug delivery in the prevention of locally recurrent disease. The biomechanical characteristics of anterior reconstruction using PMMA have not been adequately evaluated. Purpose: To evaluate the stability of an anterior cement construct following total spondylectomy and to compare this reconstruction against alternative stabilisation techniques. Methods: Ten fresh-frozen human cadaveric spines (T9-L3) were used. After intact analysis, a total spondylectomy was performed at T12. Three potential reconstruction techniques were tested for their ability to restore stiffness to the specimen: (1) multi-level posterior pedicle screw instrumentation from T10-L2 {MP1} [Depuy Acromed], (2) anterior instrumentation [ATL Z-plate II™, Medtronic, Sofamor Danek Instruments] and rib graft at T11-L1 with multi-level posterior instrumentation from T10-L2 {AMPI}, and (3) anterior cement [Simplex P] and pins construct (T12) with multi-level posterior instrumentation from T10-L2 {CMPI}. Each of the three potential reconstruction techniques was tested on each specimen in random order. Non-destructive testing was performed under load control. The specimen was positioned vertically for axial compression and torsion testing, and horizontal for flexion/extension and lateral bending tests. A customised jig was manufactured for this latter purpose. Results: Only circumferential stabilisation techniques (AMPI, CMPI) restored stiffness to a level equivalent or higher to that of the intact spine in all loading modes (p< 0.05). CMPI provided more stability to the specimen than AMPI in compression and flexion testing (p< 0.05). Posterior instrumentation alone (MPI) did not restore stiffness to the intact level in compression and flexion testing (p< 0.005). Conclusions: Circumferential reconstruction using an anterior cement construct provides equal or more stability than the intact spine in all testing modes. Posterior stabilisation alone is an inadequate method of reconstruction following total spondylectomy. PMMA has the advantage over traditional anterior reconstruction techniques in that it can be inserted using a single posterior approach and offers the potential value of local drug delivery

Purpose: This study investigates the synergistic use of fusidic acid with vancomycin, and linezolid in poly-methylmethacrylate (PMMA) cement for the treatment of orthopedic MRSA and MRSE infections. Alone, Vancomycin is typically eluted in limited quantities from cement. The purpose of this study was to. combine FA and Vancomycin, and Linezolid alone in PMMA cement and characterize antibiotic elution, and. to improve drug release using polyethylene glycol (PEG) and NaCl in PMMA cement. Method: Standardized 1g pellets of Palacos cement were manufactured containing Vancomycin and FA or Linezolid at increasing concentrations in three batches: without additive, with increasing concentrations of PEG, and with increasing concentrations of NaCl. The pellets were incubated in phosphate buffered saline and sampled at regular intervals. Drug analysis was performed with high pressure liquid chromatograpy. Results: Total drug release at 2.5% loading of Vancomycin alone was 0.84% and of FA was 2.35%. Linezolid showed comparable release profiles. Vancomycin and FA combined yeilded Vancomycin release of 6.2% and FA of 8.4%. The addition of 30% PEG increased release of Vancomycin and Fusidic Acid by six-fold. The addition of 18% NaCl increased total Vancomycin release by 11-fold but had no effect on FA release. Conclusion: Linezolid, Vancomycin and FA can be combined in PMMA and have favorable release profiles. The addition of PEG and NaCl dramatically increases the release of antibiotics, with the exception of FA and NaCl. These strategies may be useful in the management of MRSA/MRSE infections

Introduction: morcelized defatted bone-Bank graft (MOD-B) has been employed in 249 patients for different diseases in Rizzoli Institute from 1998 to 2002. 82 hip revisions, 51 spine fusions, 50 osteolitic bone cavities, 47 non-unions). Good results obtained with MOD-B have been the reason for different researches of his properties like an antibiotic carrier and, in the same time, a particular new bone graft. Material and Methods:. MOD-B with antibiotic powder and PMMA Cylinders (A-MB-C) have been placed in saline solution and plasma for 4 weeks, compared with cylinders made with PMMA and antibiotic. The mechanical resistance of A-MB-C to compressive test has been performed subsequently. About biocompatibility, A-MB-C were implanted in sheep’s Ilium. After 3 moths an histologic evaluation has been performed. Results:. The MOD-B + antibiotic + PMMA have released the higher quantity of antibiotic for all the 4 weeks. The A-MB-C resistance has been of 13.6 MPa, the same resistance of cancellous bone in the man’s femur. The histological result with a fluoroscopic microscope has been an osteogenesis in the full section of the cylinders. Conclusions: morcelized defatted bone-Bank graft is an important opportunity to restore bone loss lesions but, with a septic situation, it is not so easy obtain good results. A very important goal would be to have a graft with good antibiotic deliver system, good mechanical compressive strength and the potential capacity to become new living bone

Pain is the main symptom of acetabular osteolysis and is frequently associated with pathologic fractures. Surgical procedures requiring an aggressive approach, and as a consequence high morbidity, are rarely indicated. The minimally invasive approach may be effective in treating tumours and is capable of reducing the mechanical pain. PMMA has been widely used in neoplastic and spinal surgery as a bone filler because of its mechanical and biologic behaviours. Recently percutaneous injection of PMMA was proposed for the treatment of neoplastic acetabular osteolysis. The technique was tested in four patients affected by secondary ostheolytic lesions. The patients were evaluated clinically (HHS, Womac, SF-12) and radiographically (X-ray and CT) at 18 months. All the patients demonstrated a durable and significant improvement in terms of pain and restoration of function. The radiographic examinations (X-ray and CT) confirm these results. Complications (temporary increase in pain and fever) were only observed in one patient. The preliminary results demonstrate the reliability and effectiveness of this procedure. Clinical results showed a significant reduction in pain and the capability of restoring function. The indications can be extended also to the acetabular lesion at a distance from the weight-bearing zone, reducing pain and the risk of pathologic fractures. The technique was demonstrated to be effective and showed only minor and self-resolving complications. It is useful in patients in whom major surgery is contraindicated and clinical improvement is necessary to improve the quality of life

The use of PMMA cement vertebroplasty for the treatment of severe disabling focal back pain as a result of osteoporotic compression fractures is well established. However clinical experience of this treatment is limited in New Zealand. This study reports a technique and indications for this treatment and early clinical results. A prospective study of eight cases of severe disabling focal back pain due to osteoporotic compression fractures was undertaken. These were treated with percutaneous transpedicle vertebroplasty. The patient’s pain was assessed before and after the treatment using a visual analogue pain scale. All eight patients reported an improvement in pain immediately and at one month following the procedure. A sustained improvement in pain followed the vertebroplasty. This is consistent with other case reports in the literature although in this study the response appears to be less dramatic than that reported in other series

Introduction. Radio-opaque additives for Orthopaedic Bone Cement, like BaSO4 or ZrO2, are now routinely used because of the valuable help in identifying cement location around an implant on the x-ray films. A new bone cement formulation was devised with the aim to improve the reparative response of bone tissue surrounding a cemented implant, soon after the operation: a 6% NaF 6% BaSO4 preparation “Fluoride Bone Cement©” (Tecres, I) was tested in-vivo versus a 9% BaSO4 preparation “CemexRX©” (Tecres, I). NaF stimulating action towards bone repair is prompt by the formation of fluoroapatite and the stimulation of osteoblast differentiation. NaF-added cement acts like a “drug-release device” for fluoride ions.

Materials & Methods. Eighteen outbred male New Zealand White rabbits of approximately 3,2 kg of weight have been used. They were divided into six groups of three units. Gropus A1, A2, A3 were implanted with cement without fluoride “CemexRX©” while groups B1, B2, B3 had “Fluoride Bone Cement©”. Retrieval occurred after 17 days (A1, B1); 33 days (A2, B2); 60 days (A3, B3). The surgical implantation site selected was the distal femural canal (meta-epiphyseal region). The canal in the right femur was filled with cement while the canal in the left femur was used as a surgical control (“sham” operation). Sections of 100 micron of thickness were taken by a rotating diamond-saw microtome (Leitz Wetzlar) and analyzed by polarized light and ultra-violet fluorescence microscopy (Nikon Miscroscope). One hundred and twenty sections were obtained for each femur.

Results. Calcein green fluorescent labelling showed that no real endosteal osteogenic response was evidenced the day after surgery, for both cement preparations, while periosteal response was normal. This was the consequence of the biological insult of the intramedullary polymerization of the cement. Xylenol orange showed that all the contra-lateral femurs (“sham”) had a normal endosteal and periosteal osteogenesis at all times. Both cement preparations continued to show a limited end-osteal response after 17 days and a slow recovery after 33 days, with better pictures in favour of NaF cement. After 60 days recovery in endosteal osteogenesis was adequate but, again, NaF cement showed the highst number of good pictures.

Conclusions. Adding NaF promoted the better recovery in endosteal osteogenic response observed in comparison with NaF-free cement. To differentiate the biological response it was essential to compare a high number of sections (120) in comparable locations, in a contralateral “sham” operated control in the very same animal. This procedure, costly and demanding, seems to be a right methodological approach.

Aims

Two-stage exchange revision total hip arthroplasty (THA) performed in case of periprosthetic joint infection (PJI) has been considered for many years as being the gold standard for the treatment of chronic infection. However, over the past decade, there have been concerns about its safety and its effectiveness. The purposes of our study were to investigate our practice, collecting the overall spacer complications, and then to analyze their risk factors.

Knee sepsis following TKR can have devastating consequences for patient as well as surgeon. A two stage revision is a well accepted technique in TKR sepsis with the introduction of a temporary antibiotic cement spacer being the most popular procedure although irrigation techniques are popular in SA.

From a total of 111 revisions TKR from my practice 26 (23%) were 2 stage revisions for joint sepsis following TKR. 3 cases were early, 10 intermediate and 13 late onset sepsis cases. Most common organism was S. Aureus (7/26) and S. Epidermidis (7/26) although numerous other organisms were seen.

In all cases a two stage revision with a Palacos R cements spacer plus parenteral antibiotics were used. Prosthesis used for revision was primary knee prosthesis in 8 cases and revision (stemmed) prosthesis in 18 cases. Follow up range from 13 years to 6 months (average 6.8 years) with only one case of recurrent sepsis (3.8%) which went on to an arthrodesis. Time from debridement and spacer placement to revision TKR varied from 3 weeks to 10 months (average 2.1 months).

This paper shows that meticulous debridement followed by standard antibiotic cement spacer technique with additional parenteral antibiotics is indeed the gold standard approach without necessitating additional irrigation techniques.