Aims

Limb salvage surgery (LSS) is the primary treatment option for primary bone malignancy. It involves the removal of bone and tissue, followed by reconstruction with endoprosthetic replacements (EPRs) to prevent amputation. Trabecular metal (TM) collars have been developed to encourage bone ingrowth (osseointegration (OI)) into EPRs. The primary aim of this study was to assess whether OI occurs when TM collars are used in EPRs for tumour.

Aims

The efficacy of saline irrigation for treatment of implant-associated infections is limited in the presence of porous metallic implants. This study evaluated the therapeutic efficacy of antibiotic doped bioceramic (vancomycin/tobramycin-doped polyvinyl alcohol composite (PVA-VAN/TOB-P)) after saline wash in a mouse infection model implanted with titanium cylinders.

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The aims of this study were to determine the success of a reconstruction algorithm used in major acetabular bone loss, and to further define the indications for custom-made implants in major acetabular bone loss.

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The mean age of patients undergoing total knee arthroplasty (TKA) has reduced with time. Younger patients have increased expectations following TKA. Aseptic loosening of the tibial component is the most common cause of failure of TKA in the UK. Interest in cementless TKA has re-emerged due to its encouraging results in the younger patient population. We review a large series of tantalum trabecular metal cementless implants in patients who are at the highest risk of revision surgery.

Aims

Dislocation remains a leading cause of failure following revision total hip arthroplasty (THA). While dual-mobility (DM) bearings have been shown to mitigate this risk, options are limited when retaining or implanting an uncemented shell without modular DM options. In these circumstances, a monoblock DM cup, designed for cementing, can be cemented into an uncemented acetabular shell. The goal of this study was to describe the implant survival, complications, and radiological outcomes of this construct.

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The aim of this study was to assess the clinical and radiological outcomes of an antiprotrusio acetabular cage (APC) when used in the surgical treatment of periacetabular bone metastases.

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Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia.

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We wanted to evaluate the effects of a bone anabolic agent (bone morphogenetic protein 2 (BMP-2)) on an anti-catabolic background (systemic or local zoledronate) on fixation of allografted revision implants.

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The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.

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Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system’s response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Pad4^-/- mice that display defects in peptidyl arginine deiminase 4 (PAD4), an essential protein required for NETs) or resolution (via DNase 1 treatment, an enzyme that degrades the cytotoxic DNA matrix) of NETs can prevent osseointegration failure and formation of peri-implant fibrotic tissue.

Aims

We present the clinical and radiological results at a minimum follow-up of 20 years using a second-generation uncemented total hip arthroplasty (THA). These results are compared to our previously published results using a first-generation hip arthroplasty followed for 20 years.

Aims. Although bone cement is the primary mode of fixation in total knee arthroplasty (TKA), cementless fixation is gaining interest as it has the potential of achieving lasting biological fixation. By 3D printing an implant, highly porous structures can be manufactured, promoting osseointegration into the implant to prevent aseptic loosening. This study compares the migration of cementless, 3D-printed TKA to cemented TKA of a similar design up to two years of follow-up using radiostereometric analysis (RSA) known for its ability to predict aseptic loosening. Methods. A total of 72 patients were randomized to either cementless 3D-printed or a cemented cruciate retaining TKA. RSA and clinical scores were evaluated at baseline and postoperatively at three, 12, and 24 months. A mixed model was used to analyze the repeated measurements. Results. The mean maximum total point motion (MTPM) at three, 12, and 24 months was 0.33 mm (95% confidence interval (CI) 0.25 to 0.42), 0.42 mm (95% CI 0.33 to 0.51), and 0.47 mm (95% CI 0.38 to 0.57) respectively in the cemented group, versus 0.52 mm (95% CI 0.43 to 0.63), 0.62 mm (95% CI 0.52 to 0.73), and 0.64 mm (95% CI 0.53 to 0.75) in the cementless group (p = 0.003). However, using three months as baseline, no difference in mean migration between groups was found (p = 0.497). Three implants in the cemented group showed a > 0.2 mm increase in MTPM between one and two years of follow-up. In the cementless group, one implant was revised due to pain and progressive migration, and one patient had a liner-exchange due to a deep infection. Conclusion. The cementless TKA migrated more than the cemented TKA in the first two-year period. This difference was mainly due to a higher initial migration of the cementless TKA in the first three postoperative months after which stabilization was observed in all but one malaligned and early revised TKA. Whether the biological fixation of the cementless implants will result in an increased long-term survivorship requires a longer follow-up. Cite this article: Bone Joint J 2020;102-B(8):1016–1024

Aims

The aim of this study was to compare the ability of tantalum, 3D porous titanium, antibiotic-loaded bone cement, and smooth titanium alloy to inhibit staphylococci in an in vitro environment, based on the evaluation of the zone of inhibition (ZOI). The hypothesis was that there would be no significant difference in the inhibition of methicillin-sensitive or methicillin-resistant Staphylococcus aureus (MSSA/MRSA) between the two groups.

Aims. The aims of this study were to compare the mean duration of antibiotic release and the mean zone of inhibition between vancomycin-loaded porous tantalum cylinders and antibiotic-loaded bone cement at intervals, and to evaluate potential intrinsic antimicrobial properties of tantalum in an in vitro medium environment against methicillin-sensitive Staphylococcus aureus (MSSA). Materials and Methods. Ten porous tantalum cylinders and ten cylinders of cement were used. The tantalum cylinders were impregnated with vancomycin, which was also added during preparation of the cylinders of cement. The cylinders were then placed on agar plates inoculated with MSSA. The diameter of the inhibition zone was measured each day, and the cylinders were transferred to a new inoculated plate. Inhibition zones were measured with a Vernier caliper and using an automated computed evaluation, and the intra- and interobserver reproducibility were measured. The mean inhibition zones between the two groups were compared with Wilcoxon’s test. Results. MSSA was inhibited for 12 days by the tantalum cylinders and for nine days by the cement cylinders. At day one, the mean zone of inhibition was 28.6 mm for the tantalum and 19.8 mm for the cement group (p < 0.001). At day ten, the mean zone of inhibition was 3.8 mm for the tantalum and 0 mm for the cement group (p < 0.001). The porous tantalum cylinders soaked only with phosphate buffered solution showed no zone of inhibition. Conclusion. Compared with cement, tantalum could release antibiotics for longer. Further studies should assess the advantages of using antibiotic-loaded porous tantalum implants at revision arthroplasty. Cite this article: Bone Joint J 2019;101-B:848–851

Aims. Our intention was to investigate if the highly porous biological fixation surfaces of a new 3D-printed total knee arthroplasty (TKA) achieved adequate fixation of the tibial and patellar components to the underlying bone. Patients and Methods. A total of 29 patients undergoing primary TKA consented to participate in this prospective cohort study. All patients received a highly porous tibial baseplate and metal-backed patella. Patient-reported outcomes measures were recorded and implant migration was assessed using radiostereometric analysis. Results. Patient function significantly improved by three months postoperatively (p < 0.001). Mean difference in maximum total point motion between 12 and 24 months was 0.021 mm (-0.265 to 0.572) for the tibial implant and 0.089 mm (-0.337 to 0.758) for the patellar implant. The rate of tibial and patellar migration was largest over the first six postoperative weeks, with no changes in mean tibia migration occurring after six months, and no changes in mean patellar migration occurring after six weeks. One patellar component showed a rapid rate of migration between 12 and 24 months. Conclusion. Biological fixation appears to occur reliably on the highly porous implant surface of the tibial baseplate and metal-backed patellar component. Rapid migration after 12 months was measured for one patellar component. Further investigation is required to assess the long-term stability of the 3D-printed components and to determine if the high-migrating components achieve fixation. Cite this article: Bone Joint J 2019;101-B(7 Supple C):40–47

Aims. The purpose of this study was to evaluate the biological fixation of a 3D printed porous implant, with and without different hydroxyapatite (HA) coatings, in a canine model. Materials and Methods. A canine transcortical model was used to evaluate the characteristics of bone ingrowth of Ti6Al4V cylindrical implants fabricated using laser rapid manufacturing (LRM). At four and 12 weeks post-implantation, we performed histological analysis and mechanical push-out testing on three groups of implants: a HA-free control (LRM), LRM with precipitated HA (LRM-PA), and LRM with plasma-sprayed HA (LRM-PSHA). Results. Substantial bone ingrowth was observed in all LRM implants, with and without HA, at both time periods. Bone ingrowth increased from 42% to 52% at four weeks, to 60% to 65% at 12 weeks. Mechanical tests indicated a minimum shear fixation strength of 20 MPa to 24 MPa at four weeks, and 34 MPa to 40 MPa at 12 weeks. There was no significant difference in the amount of bone ingrowth or in the shear strength between the three implant types at either time period. Conclusion. At four and 12 weeks, the 3D printed porous implants exhibited consistent bone ingrowth and high mechanical shear strength. Based on the results of this study, we confirmed the suitability of this novel new additive manufacturing porous material for biological fixation by bone ingrowth. Cite this article: Bone Joint J 2019;101-B(6 Supple B):62–67

Objectives

In order to address acetabular defects, porous metal revision acetabular components and augments have been developed, which require fixation to each other. The fixation technique that results in the smallest relative movement between the components, as well as its influence on the primary stability with the host bone, have not previously been determined.

Despite its intrinsic ability to regenerate form and function after injury, bone tissue can be challenged by a multitude of pathological conditions. While innovative approaches have helped to unravel the cascades of bone healing, this knowledge has so far not improved the clinical outcomes of bone defect treatment. Recent findings have allowed us to gain in-depth knowledge about the physiological conditions and biological principles of bone regeneration. Now it is time to transfer the lessons learned from bone healing to the challenging scenarios in defects and employ innovative technologies to enable biomaterial-based strategies for bone defect healing. This review aims to provide an overview on endogenous cascades of bone material formation and how these are transferred to new perspectives in biomaterial-driven approaches in bone regeneration.

Cite this article: T. Winkler, F. A. Sass, G. N. Duda, K. Schmidt-Bleek. A review of biomaterials in bone defect healing, remaining shortcomings and future opportunities for bone tissue engineering: The unsolved challenge. Bone Joint Res 2018;7:232–243. DOI: 10.1302/2046-3758.73.BJR-2017-0270.R1.

The development and pre-clinical evaluation of nano-texturised, biomimetic, surfaces of titanium (Ti) implants treated with titanium dioxide (TiO. 2. ) nanotube arrays is reviewed. In vitro and in vivo evaluations show that TiO. 2. nanotubes on Ti surfaces positively affect the osseointegration, cell differentiation, mineralisation, and anti-microbial properties. This surface treatment can be superimposed onto existing macro and micro porous Ti implants creating a surface texture that also interacts with cells at the nano level. Histology and mechanical pull-out testing of specimens in rabbits indicate that TiO. 2. nanotubes improves bone bonding nine-fold (p = 0.008). The rate of mineralisation associated with TiO. 2. nanotube surfaces is about three times that of non-treated Ti surfaces. In addition to improved osseointegration properties, TiO. 2. nanotubes reduce the initial adhesion and colonisation of Staphylococcus epidermidis. Collectively, the properties of Ti implant surfaces enhanced with TiO. 2. nanotubes show great promise. Cite this article: Bone Joint J 2018;100-B(1 Supple A):9–16

Aims. Reconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes. Patients and Methods. A search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction. . Results. A total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing’s sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34). . Conclusion. Both the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes. . Cite this article: Bone Joint J 2018;100-B(1 Supple A):22–30

Aims

The optimal method of tibial component fixation remains uncertain in total knee arthroplasty (TKA). Hydroxyapatite coatings have been applied to improve bone ingrowth in uncemented designs, but may only coat the directly accessible surface. As peri-apatite (PA) is solution deposited, this may increase the coverage of the implant surface and thereby fixation. We assessed the tibial component fixation of uncemented PA-coated TKAs versus cemented TKAs.

Aims

One method of femoral head preservation following avascular necrosis (AVN) is core decompression and insertion of a tantalum rod. However, there may be a high failure rate associated with this procedure. The purpose of this study was to document the clinical and radiological outcomes following total hip arthroplasty (THA) subsequent to failed tantalum rod insertion.

A common situation presenting to the orthopaedic surgeon today is a worn acetabular liner with substantial acetabular and pelvic osteolysis. The surgeon has many options for dealing with osteolytic defects. These include allograft, calcium based substitutes, demineralised bone matrix, or combinations of these options with or without addition of platelet rich plasma. To date there are no clinical studies to determine the efficacy of using bone-stimulating materials in osteolytic defects at the time of revision surgery and there are surprisingly few studies demonstrating the clinical efficacy of these treatment options. Even when radiographs appear to demonstrate incorporation of graft material CT studies have shown that incorporation is incomplete. The surgeon, in choosing a graft material for a surgical procedure must take into account the efficacy, safety, cost and convenience of that material.

Cite this article: Bone Joint J 2014;96-B (11 Suppl A):70–2.

A pelvic discontinuity occurs when the superior and inferior parts of the hemi-pelvis are no longer connected, which is difficult to manage when associated with a failed total hip replacement. Chronic pelvic discontinuity is found in 0.9% to 2.1% of hip revision cases with risk factors including severe pelvic bone loss, female gender, prior pelvic radiation and rheumatoid arthritis. Common treatment options include: pelvic plating with allograft, cage reconstruction, custom triflange implants, and porous tantalum implants with modular augments. The optimal technique is dependent upon the degree of the discontinuity, the amount of available bone stock and the likelihood of achieving stable healing between the two segments. A method of treating pelvic discontinuity using porous tantalum components with a distraction technique that achieves both initial stability and subsequent long-term biological fixation is described. Cite this article: Bone Joint J 2014;96-B(11 Suppl A):73–7

The conventional method for reconstructing acetabular bone loss at revision surgery includes using structural bone allograft. The disadvantages of this technique promoted the advent of metallic but biocompatible porous implants to fill bone defects enhancing initial and long-term stability of the acetabular component. This paper presents the indications, surgical technique and the outcome of using porous metal acetabular augments for reconstructing acetabular defects. . Cite this article: Bone Joint J 2013;95-B, Supple A:103–8

The August 2013 Research Roundup³⁶⁰ looks at: passive smoking and bone substitutes; platelet-rich plasma and osteogenesis; plantar fasciitis and platelet-rich plasma: a match made in heaven?; MRSA decolonisation decreases infection rates; gums, bisphosphonates and orthopaedics; PRAISE and partner violence; blunt impact and post-traumatic OA; and IDEAL research and implants

Stems improve the mechanical stability of tibial components in total knee replacement (TKR), but come at a cost of stress shielding along their length. Their advantages include resistance to shear, reduced tibial lift-off and increased stability by reducing micromotion. Longer stems may have disadvantages including stress shielding along the length of the stem with associated reduction in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic fracture and end-of-stem pain. These features make long stems unattractive in the primary TKR setting, but often desirable in revision surgery with bone loss and instability. In the revision scenario, stems are beneficial in order to convey structural stability to the construct and protect the reconstruction of bony defects. Cemented and uncemented long stemmed implants have different roles depending on the nature of the bone loss involved.

This review discusses the biomechanics of the design of tibial components and stems to inform the selection of the component and the technique of implantation.

Objectives. An experimental rabbit model was used to test the null hypothesis, that there is no difference in new bone formation around uncoated titanium discs compared with coated titanium discs when implanted into the muscles of rabbits. Methods. A total of three titanium discs with different surface and coating (1, porous coating; 2, porous coating + Bonemaster (Biomet); and 3, porous coating + plasma-sprayed hydroxyapatite) were implanted in 12 female rabbits. Six animals were killed after six weeks and the remaining six were killed after 12 weeks. The implants with surrounding tissues were embedded in methyl methacrylate and grinded sections were stained with Masson-Goldners trichrome and examined by light microscopy of coded sections. Results. Small amounts of bone were observed scattered along the surface of five of the 12 implants coated with porous titanium, and around one out of 12 porous coated surfaces with Bonemaster. No bone formation could be detected around porous coated implants with plasma-sprayed hydroxyapatite. Conclusion. Porous titanium coating is to some degree osteoinductive in muscles

Metallosis is a rare cause of failure after total knee replacement and has only previously been reported when there has been abnormal metal-on-metal contact. We describe 14 patients (15 knees) whose total knee replacement required revision for a new type of early failure caused by extensive metallosis. A modification of a cementless rotating platform implant, which had previously had excellent long-term survival, had been used in each case. The change was in the form of a new porous-beaded surface on the femoral component to induce cementless fixation, which had been used successfully in the fixation of acetabular and tibial components. This modification appeared to have resulted in metallosis due to abrasive two-body wear. The component has subsequently been recalled and is no longer in use. The presentation, investigation, and findings at revision are described and a possible aetiology and its implications are discussed.

Between November 1997 and December 2000 we performed 27 total hip replacements in 22 patients with high congenital dislocation of the hip using porous tantalum monoblock acetabular components implanted in the true acetabular bed. Clinical and radiological evaluation was performed at regular intervals for a mean of 10.2 years (8.5 to 12). The mean Harris Hip Score improved from 48.3 (15 to 65) pre-operatively to 89.5 (56 to 100) at the final follow-up. The mean Oxford Hip Score was 49.5 (35 to 59) pre-operatively and decreased to 21.2 (12 to 48) at one year and 15.2 (10 to 28) at final follow-up. Migration of the acetabular component was assessed with the EBRA software system. There was a mean migration of 0.68 mm (0.49 to 0.8) in the first year and a mean 0.89 mm (0.6 to 0.98) in the second year, after excluding one initial excessive migration. No revision was necessary for any reason, no acetabular component became loose, and no radiolucent lines were observed at the final follow-up.

The porous tantalum monoblock acetabular component is an implant offering adequate initial stability in conjunction with a modulus of elasticity and porosity close to that of cancellous bone. It favours bone ingrowth, leading to good mid-term results.

The management of osteonecrosis of the femoral head ranges from symptomatic therapy to total hip replacement. Conservative treatment is effective only in small, early-stage lesions. Free vascularised fibular grafting has provided more consistently successful results than any other joint-preserving method. It supports the collapsing subchondral plate by primary callus formation, reduces intra-osseous pressure, removes and replaces the necrotic segment, and adds viable cortical bone graft plus fresh cancellous graft, which has osseoinductive and osseoconductive potential. Factors predisposing to success are the aetiology, stage and size of the lesion. Furthermore, it is a hip-salvaging procedure in early pre-collapse stages, and a time-buying one when the femoral head has collapsed.

Carbonate-substituted hydroxyapatite (CHA) is more osteoconductive and more resorbable than hydroxyapatite (HA), but the underlying mode of its action is unclear. We hypothesised that increased resorption of the ceramic by osteoclasts might subsequently upregulate osteoblasts by a coupling mechanism, and sought to test this in a large animal model.

Defects were created in both the lateral femoral condyles of 12 adult sheep. Six were implanted with CHA granules bilaterally, and six with HA. Six of the animals in each group received the bisphosphonate zoledronate (0.05 mg/kg), which inhibits the function of osteoclasts, intra-operatively.

After six weeks bony ingrowth was greater in the CHA implants than in HA, but not in the animals given zoledronate. Functional osteoclasts are necessary for the enhanced osteoconduction seen in CHA compared with HA.

Between January 1998 and December 1998, 82 consecutive patients (86 hips) underwent total hip arthroplasty using a trabecular metal monoblock acetabular component. All patients had a clinical and radiological follow-up evaluation at six, 12 and 24 weeks, 12 months, and then annually thereafter. On the initial post-operative radiograph 25 hips had a gap between the outer surface of the component and the acetabular host bed which ranged from 1 to 5 mm. All patients were followed up clinically and radiologically for a mean of 7.3 years (7 to 7.5). The 25 hips with the 1 to 5 mm gaps were studied for component migration at two years using the Einzel-Bild-Roentgen-Analyse (EBRA) digital measurement method. At 24 weeks all the post-operative gaps were filled with bone and no acetabular component had migrated. The radiographic outcome of all 86 components showed no radiolucent lines and no evidence of lysis. No acetabular implant was revised. There were no dislocations or other complications. The bridging of the interface gaps (up to 5 mm) by the trabecular metal monoblock acetabular component indicates the strong osteoconductive, and possibly osteoinductive, properties of trabecular metal.

We describe the clinical and radiological results of 120 consecutive revision hip replacements in 107 patients, using the JRI Furlong hydroxyapatite-ceramic-coated femoral component. The mean age of the patients at operation was 71 years (36 to 92) and the mean length of follow-up 8.0 years (5.0 to 12.4). We included patients on whom previous revision hip surgery had taken place. The patients were independently reviewed and scored using the Harris hip score, the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and the Charnley modification of the Merle d’Aubigné and Postel score. Radiographs were assessed by three reviewers for the formation of new bone, osteolysis, osseointegration and radiolucent lines in each Gruen zone.

The mean Harris hip score was 85.8 (42 to 100) at the latest post-operative review. The mean WOMAC and Merle d’Aubigné and Postel scores were 34.5 and 14.8, respectively. The mean visual analogue score for pain (possible range 0 to 10) was 1.2 overall, but 0.5 specifically for mid-thigh pain. There were no revisions of the femoral component for aseptic loosening. There were four re-revisions, three for infection and one for recurrent dislocation. Radiological review of all the femoral components, including the four re-revisions showed stable bony ingrowth and no new radiolucent lines in any zone. Using revision or impending revision for aseptic loosening as an end-point, the cumulative survival of the femoral component at ten years was 100% (95% confidence interval 94 to 100). We present excellent medium- to long-term clinical, radiological and survivorship results with the fully hydroxyapatite-ceramic-coated femoral component in revision hip surgery.

The effect of zoledronic acid on bone ingrowth was examined in an animal model in which porous tantalum implants were placed bilaterally within the ulnae of seven dogs. Zoledronic acid in saline was administered via a single post-operative intravenous injection at a dose of 0.1 mg/kg. The ulnae were harvested six weeks after surgery. Undecalcified transverse histological sections of the implant-bone interfaces were imaged with backscattered scanning electron microscopy and the percentage of available pore space that was filled with new bone was calculated. The mean extent of bone ingrowth was 6.6% for the control implants and 12.2% for the zoledronic acid-treated implants, an absolute difference of 5.6% (95% confidence interval, 1.2 to 10.1) and a relative difference of 85% which was statistically significant. Individual islands of new bone formation within the implant pores were similar in number in both groups but were 69% larger in the zoledronic acid-treated group. The bisphosphonate zoledronic acid should be further investigated for use in accelerating or enhancing the biological fixation of implants to bone

In rabbits and goats, test implants with a porous surface of two layers of Tl-6A;-4V beads were examined at intervals for bond strength with bone. Half of the implants were coated with hydroxyapatite by plasma spray. The bonding strength with bone in the coated specimens was about four times greater than that of the uncoated specimens at two weeks, and twice as strong at six weeks. Twelve weeks after implantation, the strengths were similar. The hydroxyapatite coating of the beads provided earlier and stronger fixation.