Bone impaction grafting of the femur is associated with more complications when segmental defects are present. The effect of segmental defect repair on initial stem stability was studied in an in vitro study with fresh frozen goat femora. A standardized medial segmental defect was reconstructed using a cortical strut or a metal mesh. As controls we used intact femora and femora with a non-reconstructed defect. In all four groups impacted bone grafting was performed in combination with a cemented Exeter stem. Each group contained five femora. Reconstructions were dynamically loaded up to 1500N. Migration was measured with Roentgen Stereo-photogrammetric Analysis. All cases with a non-reconstructed segmental defect failed into excessive varus rotation. None of the femora with a reconstructed defect failed. Cortical struts and metal meshes were equally effective in creating a stable stem construction (varus rotation 2.89±2.27 and 2.27±0.57, respectively). Reconstructions with a metal mesh were more reproducible, although the obtained stability was significantly lower (p< 0.01) when compared to impaction grafting in an intact femur (varus rotation 0.58±0.36). Besides, structural grafts may negatively influence the revascularization of the underlying impacted grafts in contrast to an open wire mesh. So, an in vivo study of 12 goats was done. A standardized medial wall defect was reconstructed with a strut or a mesh in six goats per group. In all femora impaction grafting was performed in combination with a cemented Exeter stem. After six weeks the femora were harvested. A high rate of peri-prosthetic fractures was found (43% and 29% for the strut and mesh groups, respectively). Histological and micro-radiological examination showed different revascularization patterns for both reconstruction techniques. In the strut group revascularized graft was found at the edges of the defect. In the mesh group fibrous tissue and blood vessels penetrated through the mesh and a superficial zone of revascularized grafts was found. Segmental defect reconstruction with a strut reduced the amount of revascularized grafts medially behind the strut (p=0.004). This may interfere with the stability of the stem in the first period after surgery and the incorporation of the impacted grafts on the long-term. We would recommend segmental defect reconstruction with a mesh. A regime of unloading and long-stem prostheses should be used, irrespective of the reconstruction technique

Purpose: One of the most difficult challenges for orthopaedic surgeons is the management of bone loss resulting in a segmental bone defect. Segmental bone defects are ubiquitously difficult to treat, require multi-phase surgery and have frequent complications. A promising new strategy involves combining tissue engineering techniques with the delivery of biologically active proteins to facilitate bone regeneration. The purpose of this study is twofold:. First, to investigate whether a cylindrical, biodegradable load-bearing scaffold, stabilized with an intramedullary (IM) nail, will facilitate early weight bearing in a critical sized canine defect model. The second objective is to investigate if rhBMP-2, transported by the biodegradable carrier, will enhance bone formation and healing across a critical sized canine defect. Method: A critical size defect of 3 cm was created in the canine tibia by osteotomy. A cylindrical, biodegradable scaffold of (poly) propylene fumarate was inserted into the defect and the tibia was stabilized with a locked intramedullary nail. Half of the scaffolds were impregnated with 300μg rhBMP-2 and half remained as controls. The animals were allowed immediate weight bearing post-operatively. X-rays were obtained post-operatively and at weeks 1, 2, 3, 6, 12, 18, and 24. X-rays were assessed for loss of height, integrity of the scaffold, and presence of bridging callous formation. Results: The animals that received scaffolds treated with rhBMP-2 showed abundant callus formation on X-ray. Partial bridging callus formation in this group was seen at 3 weeks. Complete bridging callus (bridging on 4 cortices) was observed by 6 weeks. These specimens maintained height of the defect and overall length of the tibia. Controls demonstrated minimal callus formation at all time points. By 3 weeks significant loss of defect height was observed. By 6 weeks failure of hardware (breakage of interlocking screws and/or screw loosening) was evident. Conclusion: This study shows that biodegradable scaffolds, treated with rhBMP-2 and implanted in a critical sized defect facilitate bridging callus formation and healing across the defect. This data indicates that biodegradable scaffolds made of (poly) propylene fumarate are suitable carriers for rhBMP-2 while providing initial structural support for weight bearing

It has been shown that mesenchymal stem cells (MSCs) and BMP are involved in bone formation. The aim of the study was to evaluate the osteogenic potential of human bone marrow (hBM), human expanded MSC (hexp-MSC), BMP-7, and hexp-MSC plus BMP-7, to treat a rat femoral segmental defect.

Sprague-Dawley (SD) and athymic rats (Nu) were used. SD rats where used in order to define surgical technique. Nu rats groups consisted of: G1-autoclaved bone and human bone marrow (hMNC); G2-bone and hexp-MSC; G3-bone with BMP-7 only; and G4-bone and hexp-MSC with BMP-7. A plate was attached to the femoral diaphysis with two cerclage wires. Then a 6-mm femoral gap was made and filled with a different graft. At regular intervals, the femoral defect was evaluated with radiographs, using a modified six-grade Cook classification.

At 8 weeks G1 showed non-visible new bone formation; G2 minimal new disorganised bone; G3 disorganised new bone bridging the graft to host at both ends; and G4 significant new bone and graft remodelling. Histological analysis confirmed these results.

Our results showed that although the osteogenic activity may be improved by hMSC (G2) as well as by BMP-7 (G3), the association hexp-MSC plus BMP-7(G4) produced graft osteointegration at 8 weeks after surgery. This may have a remarkable impact on future orthopaedics surgery strategies.

We sought to establish whether fibroblasts transfected ex vivo could be delivered via gelfoam impregnated with a solution of transfected cells to achieve local transgene expression in a fracture site.

A 10 millimeter segmental bone defect was created after 12 mm periosteal excision and plated in the middle one third of each rabbit tibia. Dermal tissues were obtained and fibroblasts were cultured with DMEM. Fibroblasts were labeled with CMTMR and 5x106 labeled fibroblasts in 1ml PBS with 1x1 cm? Impregnated gelfoam was placed into the fracture gap (n=2). Twenty four hours after cell injection, the rabbits were killed and specimens were harvested from the fractured leg. Using SuperFect (Qiagen Inc), the primary fibroblasts were transfected with pcDNA-VEGF which was generated with the full length coding sequence of the human VEGF gene. A convenient reporter gene, Efficiency Green Fluorescent Protein (EGFP), was used for monitoring transfection of VEGF by fluorescence intensity. Experimental rabbits received 5.0 X 106 VEGF transfected cells in 1 ml PBS via gelfoam at the fracture sites. The animals were sacrificed at seven days (n=4), fourteen days (n=4) and twenty-one days (n=4) post surgery and the fracture site specimens were collected for analysis.

The fluorescently labeled cells with CMTMR were found at the fracture site and surrounding tissues. It was demonstrated that the labeled cells were delivered into the fracture gap, bone marrow and muscle surrounding a segmental defect in the rabbit. In the VEGF group, visualised VEGF immunostaining (brown) was shown in the fracture site around the Gelfoam; as well VEGF was distributed at sites of endochondral ossification. Visible bone formation was shown: VEGF promoted new bone formation by VonKossa staining (dark) and produced numerous vessels by CD31 positive staining (brownish black). The VEGF protein was detected in and around the fracture by ELISA.

This data encourages the further development of genetic approaches using cell based VEGF gene transfer without viral vectors to promote fracture healing.

Introduction/Background: This study was designed to determine the osteoinductive capacity of rhBMP-2 in a non-critical size femoral defect in normal rats and rats with diabetes mellitus (DM). It was hypothesized that DM would result in impaired bone regeneration in the femoral non-critical size defects due to reduced bone formation and local delivery of rhBMP-2 would accelerate non-DM healing and normalize impaired bone healing in DM rats to the levels of Non-DM bone healing.

Materials/Methods: A total of 80 BB Wistar rats were used in the project. A 3mm defect was created during surgery and stabilized with a polyimide plate and either a 0.05cc/11μg dose of rhBMP-2 or buffer in a collagen sponge was implanted into the defect. Microradiographs were taken on the day of sacrifice and processing of samples for PECAM-1 immunohistochemistry, histomorphometry, and mechanical testing was performed.

Results: Both Non-DM and DM groups treated with rhBMP-2 demonstrated significantly higher radiographic scoring, total new bone formation, BV quantification, and mechanical testing parameters compared to those treated with buffer at all timepoints with no significance noted between Non-DM and DM groups treated with rhBMP-2.

Discussion/Conclusions: This study reveals decreased amount of new bone formation in DM animals compared to Non-DM animals, showing the detrimental effects of DM upon bone healing. A single application of rhBMP-2 resulted in new bone formation in DM animals similar to Non-DM animals, suggesting a critical role for rhBMP-2 in ameliorating the deleterious effects of DM on bone regeneration and formation.

Besides these groups 15 more DM rats were used for PECAM-1 staining for angiogenesis (7 with 1 loss at a 3 week time point) and mechanical testing (8 at a 9 week time point).

Purpose: Extracortical bone bridging and ingrowth have been shown to reduce stresses on the stem and cement mantle of tumor endoprostheses. The purpose of this study was to assess the effect of bone morphogenetic protein 7 (BMP-7) delivered by Peri-Apatiteâ (PA, Stryker Orthopaedics) hydroxyapatite coating on porous segmental replacement prostheses.

Method: Eighteen mature mongrel canines were implanted with unilateral segmental replacement prostheses made of a cobalt-chromium (Co-Cr) alloy and coated with two layers of sintered Co-Cr alloy beads (diameter 600 to 800mm). The control group consisted of a plain porous coated segmental prosthesis without any PA coating. Group 2 consisted of a PA-coated segmental prosthesis coated with buffer solution. Group three consisted of a PA-coated segmental prosthesis loaded with rhBMP-7 (Stryker Biotech) in a buffer solution carrier. Group 1 had the implant only. Group 2 had the buffer solution evenly applied to the porous coat and group 3 had 2.9 mg of BMP-7 in liquid buffer solution evenly applied. The canines were allowed to fully bear weight without restrictions. The femurs were retrieved at twelve weeks for radiographic and histologic analysis.

Results: Gross and radiographic data of the retrieved specimens showed that all six PA-coated implants augmented with BMP-7 had complete bone bridging; only one of the PA-coated implants and only two of the plain porous implants were completely bridged. There was a greater percentage of bone apposition for the BMP-7 augmented PA-coated group compared to both the plain (p=0.0026) and the PA-coated (p=0.0001). There was no difference in bone formation or bone apposition between the plain and PA-coated groups. Histology revealed greater depth of bone ingrowth in the BMP-7 augmented PA-coated group as compared to the plain (p< 0.0001) and the PA-coated (p< 0.0001) groups. There was also significantly greater bone apposition in the BMP-7 augmented PA coated groups as compared to the plain (p=0.0014) and PA-coated (p=0.0067) groups. There was no significant difference in depth of bone ingrowth or bone apposition between the plain and PA-coated groups.

Conclusion: BMP-7 when used to augment PA-coated prostheses in a canine segmental defect model can significantly improve extracortical bone bridging and bone ingrowth. PA-coated implants may be considered to deliver the exogenous biological growth factors.

Introduction. Segmental bone defect is a challenging problem. We report our experience of bone transport by hexapod external fixator in patients with segmental defects if the tibia. Method. We report herein 15 patients with segmental bone defect of tibia who completed their treatment protocol. All patients were treated had bone transport with Taylor Spatial Frame from 2012 to 2017. All were treated by the senior author NH. Parameters measured included age, sex, diabetes, smoking, diagnosis, method of fixation prior to treatment use of a free flap, bone defect size, frame-time, external fixation index. Results. Mean age at the time of frame application was 42.7 years. Mean follow-up after frame removal was 23.7 months. Three were diabetic, one smoked and one quit smoking during treatment. Seven had Gustilo-Anderson 3B (47%) and 5 Gustilo-Anderson 3A (33%) open fractures. Three (20%) had closed fractures. Nine (60%) had internal fixation with plate in eight and IM nail in one. Ten patients (67%) had soft tissue defect that required a free flap in seven, local flap in two and skin graft in one. Mean transport was 62 mm. Mean external fixator time and latency were 350.1 and 12 days, respectively. Mean External fixator, distraction and maturation indices were 2.1, 0.52 and 1.43 month per centimeter, respectively. Ten Extra- procedures were required in 7 patients. There were no docking site procedures, non-union of regenerate, adjunctive stabilization after frame removal, recurrence of bone infection and recurrence of deformity. Conclusions. Segmental resection and transport by TSF is an effective method to achieve length, alignment and eradicate infection. Although our cohort had longer external fixator indices than similar studies, the complication rate was low

The Masquelet or induced membrane technique (IMT) is a two-stage surgical procedure used for the treatment of segmental bone defects. In this technique, the defect is first filled with a polymethyl methacrylate (PMMA) spacer, which triggers the formation of a membrane that will encapsulate the defect. During the second surgery, the spacer is carefully removed and replaced by autologous bone graft while preserving the membrane. This membrane is vascularized, contains growth factors, and provides mechanical stability to the graft, all of which are assumed to prevent graft resorption and promote bone healing.

The technique is gaining in popularity and several variations have been introduced in the clinical practice. For instance, orthopaedic surgeons now often include antibiotics in the spacer to treat or prevent infection. However, the consequences of this approach on the properties of the induce membrane are not fully understood. Accordingly, in a small animal model, this study aimed to determine the impact on the induced membrane of impregnating spacers with antibiotics frequently used in the IMT.

We surgically created a five-mm segmental defect in the right femur of 25 adult male Sprague Dawley rats. The bone was stabilized with a plate and screws before filling the defect with a PMMA spacer. Animals were divided into five equal groups according to the type and dose of antibiotics impregnated in the spacer: A) no antibiotic (control), B) low-dose tobramycin (1.2 g/40 g of PMMA), C) low-dose vancomycin (1 g/40 g of PMMA), D) high-dose tobramycin (3.6 g/40 g of PMMA), E) high-dose vancomycin (3 g/40 g of PMMA). The animals were euthanized three weeks after surgery and the induced membranes were collected and divided for analysis. We assessed the expression of selected genes (Alpl, Ctgf, Runx2, Tgfb1, Vegfa) within the membrane by quantitative real-time PCR. Moreover, frozen sections of the specimens were used to quantify vascularity by immunohistochemistry (CD31 antigen), proliferative cells by immunofluorescence (Ki-67 antigen), and membrane thickness. Microscopic images of the entire tissue sections were taken and analyzed using FIJI software. Finally, we measured the concentration of vascular endothelial growth factor (VEGF) in the membranes by ELISA.

No significant difference was found among the groups regarding the expression of genes related to osteogenesis (Alpl, Runx2), angiogenesis (Vegfa), or synthesis of extracellular matrix (Ctgf, Tgfb1) (n = four or five). Similarly, the density of proliferative cells and blood vessels within the membrane, as well as the membrane thickness, did not vary substantially between the control, low-dose, or high-dose antibiotic groups (n = four or five). The concentration of VEGF was also not significantly influenced by the treatment received (n = four or five).

The addition of tobramycin or vancomycin to the spacer, at the defined low and high doses, does not significantly alter the bioactive characteristics of the membrane. These results suggest that orthopaedic surgeons could use antibiotic-impregnated spacers for the IMT without compromising the induced membrane and potentially bone healing.

Objectives

The biomembrane (induced membrane) formed around polymethylmethacrylate (PMMA) spacers has value in clinical applications for bone defect reconstruction. Few studies have evaluated its cellular, molecular or stem cell features. Our objective was to characterise induced membrane morphology, molecular features and osteogenic stem cell characteristics.

Purpose

Angiogenesis and osteogenesis are essential for bone growth, fracture repair, and bone remodeling. VEGF has an important role in bone repair by promoting angiogenesis and osteogenesis. In our previous study, endothelial progenitor cells (EPCs) promoted bone healing in a rat segmental bone defect as confirmed by radiological, histological and microCT evaluations (Atesok, Li, Schemitsch 2010); EPC treatment of fractures resulted in a significantly higher strength by biomechanical examination (Li, Schemitsch 2010). In addition, cell-based VEGF gene transfer has been effective in the treatment of segmental bone defects in a rabbit model (Li, Schemitsch et al 2009); Purpose of this study: Evaluation of VEGF gene expression after EPC local therapy for a rat segmental bone defect.

Purpose: The purpose of this study was to compare the effects of two types of stem/progenitor cells on the healing of critical sized bone defects in a rat model. Endothelial Progenitor Cells (EPCs), a novel cell type with previously demonstrated effects on angiogenesis in animal models of vascular disease, were compared to both a control group of no cell therapy, and a treatment group of Mesenchymal Stem Cells (MSCs). The hypothesis was that EPCs would demonstrate both superior bone healing and angiogenesis, when compared to the control group and MSC group.

Method: EPCs and MSCs were isolated from the bone marrow of syngeneic rats by differential culture and grown ex vivo for 10 days. Subsequently the cells were harvested, seeded on a gelfoam scaffold, and implanted into a 5mm segmental defect in a rat femur that had been stabilized with a plate and screws. Bone healing was assessed radiographically and by microCT. Angiogenesis was assessed by histology and physiologically, using laser doppler to assess blood flow in the bone and soft tissues. All animal protocols were approved by and performed in accordance with the St. Michael’s Hospital Animal Care Committee. ANOVA was used to test for significant differences between the groups, and a p-value of < 0.05 was considered statistically significant.

Results: The EPC (n=14) group demonstrated radiographic evidence of healing of the bone defect as early as 2 weeks, and all specimens were radiographically healed at 6 weeks. Both the control group (n=14) and the MSC group (n=14) showed no radiographic evidence of healing at 10 weeks. MicroCT comparison of the EPC group versus the control group showed significantly greater bone volume and density at the defect site (p< 0.001). More blood vessel formation was observed in the EPC group versus the control group on histology at 2 weeks. Laser Doppler assessment showed significantly more soft tissue and bone blood flow at 2 and 3 weeks in the EPC group versus the control group (p=0.021).

Conclusion: The results of this study demonstrate that EPCs are effective as cell-based therapy for healing critical sized bone defects in a rat model. In this model EPCs demonstrated superiority to MSCs with regard to bone healing. In addition, EPCs demonstrated superior angiogenesis over controls in a rat model of fracture healing. These results strongly suggest that EPCs are effective for therapeutic angiogenesis and osteogenesis in fracture healing. There is a clinical need for effective strategies in the management of traumatic bone defects and nonunions. Investigation into the use of MSCs as an effective alternative to autologous bone grafting has failed to translate into clinical use. It is possible that EPCs are more effective at the regeneration of bone in segmental defects because of their synergistic effect on angiogenesis and osteogenesis. Further research into EPC based therapies for fracture healing is warranted.

Impaction grafting is an excellent option for acetabular revision. It is technique specific and very popular in England and the Netherlands and to some degree in other European centers. The long term published results are excellent. It is, however, technique dependent and the best results are for contained cavitary defects. If the defect is segmental and can be contained by a single mesh and impaction grafting, the results are still quite good. If, however, there is a larger segmental defect of greater than 50% of the acetabulum or a pelvic discontinuity, other options should be considered. Segmental defects of 25–50% can be managed by minor column (shelf) or figure of 7 structural allografts with good long term results. Porous metal augments are now a good option with promising early to mid-term results. Segmental defects of greater than 50% require a structural graft or porous augment usually protected by a cage. If there is an associated pelvic discontinuity then a cup cage is a better solution. An important question is does impaction grafting facilitate rerevision surgery? There is no evidence to support this but some histological studies of impacted allograft would suggest that it may. On the other hand there are papers that show that structural allografts do restore bone stock for further revision surgery. Also the results of impaction grafting are best in the hands of surgeons comfortable with using cement on the acetabular side, and one of the reasons why this technique is not as popular in North America

Objectives. Long bone defects often require surgical intervention for functional restoration. The ‘gold standard’ treatment is autologous bone graft (ABG), usually from the patient’s iliac crest. However, autograft is plagued by complications including limited supply, donor site morbidity, and the need for an additional surgery. Thus, alternative therapies are being actively investigated. Autologous bone marrow (BM) is considered as a candidate due to the presence of both endogenous reparative cells and growth factors. We aimed to compare the therapeutic potentials of autologous bone marrow aspirate (BMA) and ABG, which has not previously been done. Methods. We compared the efficacy of coagulated autologous BMA and ABG for the repair of ulnar defects in New Zealand White rabbits. Segmental defects (14 mm) were filled with autologous clotted BM or morcellized autograft, and healing was assessed four and 12 weeks postoperatively. Harvested ulnas were subjected to radiological, micro-CT, histological, and mechanical analyses. Results. Comparable results were obtained with autologous BMA clot and ABG, except for the quantification of new bone by micro-CT. Significantly more bone was found in the ABG-treated ulnar defects than in those treated with autologous BMA clot. This is possibly due to the remnants of necrotic autograft fragments that persisted within the healing defects at week 12 post-surgery. Conclusion. As similar treatment outcomes were achieved by the two strategies, the preferred treatment would be one that is associated with a lower risk of complications. Hence, these results demonstrate that coagulated BMA can be considered as an alternative autogenous therapy for long bone healing. Cite this article: Z. X. H. Lim, B. Rai, T. C. Tan, A. K. Ramruttun, J. H. Hui, V. Nurcombe, S. H. Teoh, S. M. Cool. Autologous bone marrow clot as an alternative to autograft for bone defect healing. Bone Joint Res 2019;8:107–117. DOI: 10.1302/2046-3758.83.BJR-2018-0096.R1

Background:. Segmental defects of long bones are notoriously demanding and difficult to treat. We evaluate nine cases where the Masquelet induced membrane technique to substitute bone loss has been used. We discuss the method compared to other types of bone reconstruction and share our tips and tricks to reduce treatment time and improve patient comfort. Method:. Eight patients (nine injuries) operated between 2011 and 2014 were included. Four were infected. Outcome was time-to weight-bearing, consolidation, complications, bone grafting. Results:. All patients were weight bearing fully after 270 days. Mean time to weight bearing was 225 days. Time to full weight bearing was shorter in patients where nails were used to stabilize the construct: median 115 (range 0–268) compared to plates: median 244 (range 219–271). All but two cases went on to full consolidation. Three cases needed grafting, one was misaligned. There were no amputations, no persistent infections, and no implant failures. Discussion:. The induced membrane technique is a relevant alternative to traditional bone substitution in select cases, yet somewhat unpredictable in its course and prolonged immobilisation is often required. Conclusion:. Nailing seems to improve the outcome by reducing treatment time and volume of bone graft needed and should be considered when feasible

Segmental defects of the acetabulum are often encountered in revision surgery. Many times these can be handled with hemispherical cups. However when larger defects are encountered particularly involving the dome and/or posterior wall structural support for the cup is often needed. In the past structural allograft was used but for the last 12 years at our institution trabecular metal augments have been used in the place of structural allograft in all cases. This talk will focus on technique and mid-term results using augments in association with an uncemented revision shell. The technique can be broken down into 6 steps outlined below: 1. Exposure, 2. Reaming, 3. Trialing, 4. Augment Inserted, 5. Cup Insertion/Stabilization, 6. Trial Reduction/Liner Cementation. A recent study was undertaken to assess the mid-term results of this technique. We prospectively followed the first 56 patients in whom these augments were utilised in combination with a trabecular metal acetabular component in our unit. Details of this study will be presented. The median follow up of the surviving patients was 110 months (range 88–128 months). Survivorship of the augments at 10 years was 92.2% (95% CI: 97.0–80.5%). In one case the augment was revised for infection and in 3 for loosening. In 1 of the revised cases there was a pre-operative pelvic discontinuity, the other 2 discontinuities in the series were not revised and remain asymptomatic. Conclusions. The results of the acetabular trabecular metal augments continue to be encouraging in the medium to long term with low rates of revision or loosening in this complex group of patients

Nonunions and segmental bone defects associated with infection are challenging problems faced by the orthopaedic surgeon. Antibiotic cement-coated (ACC) interlocking nails, prepared in the operating theatre using nails and materials generally available, can be used to treat these conditions. Two different types of moulds can be used (reusable or disposable). Materials and Methods: The infected nonunion/segmental bone defect was treated by débridement followed by ACC nailing in 52 patients (12 female, 40 male, age range 16–86 years). Other procedures for deformity correction, bone defect etc were carried out simultaneously as indicated. Infected nonunion was seen in 34 patients, 1 was an acute fracture after external fixator. Segmental defect in the bone of 1 to 30 cm was seen in 17 patients. Anatomical sites included Femur (13), Tibia (11), Knee (12) and ankle (16). Results: Limb salvage was achieved in 96% and amputation in 2 patients. Bony union was achieved in 41 of 49 patients (84%). In 3 patients (15%), control of infection was achieved with stable nonunion (1 patient) and stable nonunion with cement spacer (2 patients). Control of infection was achieved in 85%. Single procedure achieved this goal in 73%. Cement nail de-bonding occurred during removal in 9 patients and during insertion in 1 patient. The average follow-up was 16 months (1 to 60 m). Conclusion: Dual goals of control of infection as well as stability to promote union can be achieved using this technique. Although useful for all infected nonunions, this technique is particularly useful for patients who are not ideal candidates for external fixators or those who do not want an external fixator

The goals of revision arthroplasty of the hip are to restore the anatomy and achieve stable fixation for new acetabular and femoral components. It is important to restore bone stock, thereby creating an environment for stable fixation for the new components. The bone defects encountered in revision arthroplasty of the hip can be classified either as contained (cavitary) or uncontained (segmental). Contained defects on both the acetabular and femoral sides can be addressed by morselised bone graft that is compacted into the defect. Severe uncontained defects are more of a problem particularly on the acetabular side where bypass fixation such as distal fixation on the femoral side is not really an alternative. Most authors agree that the use of morselised allograft bone for contained defects is the treatment of choice as long as stable fixation of the acetabular component can be achieved and there is a reasonable amount of contact with bleeding host bone for eventual ingrowth and stabilisation of the cup. On the femoral side, contained defects can be addressed with impaction grafting for very young patients or bypass fixation in the diaphysis of the femur using more extensively coated femoral components or taper devices. Segmental defects on the acetabular side have been addressed with structural allografts for the past 15 to 20 years. These are indicated in younger individuals with Type 3A defects. Structural grafts are unsuccessful in Type 3B defects. Alternatives to the structural allografts are now being utilised with shorter but encouraging results in most multiply operated hips with bone loss. New porous metals such as trabecular metal (tantalum), which has a high porosity similar to trabecular bone and also has a high coefficient of friction, provide excellent initial stability. The porosity provides a very favorable environment for bone ingrowth and bone graft remodeling. Porous metal acetabular components are now more commonly used when there is limited contact with bleeding host bone. Porous metal augments of all sizes are being used instead of structural allografts in most situations. On the femoral side, metaphyseal bone loss, whether contained or uncontained, is most often addressed by diaphyseal fixation with long porous or tapered implants, modular if necessary. Distal fixation requires at least 4 centimeters of diaphyseal bone and in Type IV femurs, a choice must be made between a mega prosthesis or a proximal femoral allograft. The proximal femoral allograft can restore bone stock for future surgery in younger patients. The mega prosthesis which is more appropriate in the older population may require total femoral replacement if there is not enough diaphyseal bone for distal fixation with cement. Cortical struts are used for circumferential diaphyseal bone defects to stabilise proximal femoral allografts, to bypass stress risers and to serve as a biological plate for stabilising peri-prosthetic fractures

Purpose. Traditionally, the gold standard for bone grafting has been either autografts or allografts. Whilst autografts are still widely used, drawbacks such as donor site morbidity are shifting the market rapidly toward the use of orthobiologic bone graft substitutes. This study investigated the in vivo performance of a novel (W02008096334) collagen-hydroxyapatite (CHA) bone graft substitute material as an osteoinductive tissue engineering scaffold. This highly porous CHA scaffold offers significantly increased mechanical strength over collagen-only scaffolds while still exhibiting an extremely high porosity (≈ 99%), and an osteoinductive hydroxyapatite phase [1]. This study assessed the ability of the CHA scaffolds to heal critical-sized (15 mm) long bone segmental defects in vivo, as a viable alternative to autologous bone grafts. Method. Collagen-HA (CHA) composite scaffolds were fabricated based on a previously-described freeze-drying technique [1]. After freeze-drying, these scaffolds were subjected to a dehydrothermal treatment and subsequently chemically crosslinked using EDAC. In vivo performance was assessed using a critical size segmental radial defect (15 mm) introduced into 16 young adult New Zealand White Rabbits under Irish Government license. Animals were divided into three groups; (i) an empty defect group (negative control), (ii) an autogenous bone graft group (positive control) and (iii) a CHA scaffold group (CHA). Segmental defect healing in all animals was assessed using plain X-Ray analysis, at four time-points (0, 6, 12 and 16 weeks). MicroCT and histological analysis were carried out at week 16. Results. Empty defect groups at all time points resulted in non-union of the segmental defect bone ends. Autogenous bone graft groups exhibited good filling of the segmental defect with extensive callus formation but even after 16 weeks showed poor remodelling. Although autogenous bone graft groups showed evidence of mineralized tissue within the defect, tissue healing appeared relatively uncontrolled (Figure 1a). CHA scaffold groups exhibited extensive bone healing as early as 6 weeks. By week 16, CHA defects showed complete bridging across the entire defect (figures 1b, 2b, 3b, 4b), development of a continuous marrow cavity (Figures 2b, 3b, 4b) and evidence of remodelling. Conclusion. The results of this study provide clear evidence that Collagen-HA scaffolds, can perform at least as well as autogenous bone grafts. This study provides strong evidence that after a relatively short time in vivo, CHA scaffolds can result in a more complete and homogenous bone healing response and have the potential to offer improved bone tissue formation above that of autogenous bone. More importantly, this study provides strong evidence that the use of low stiffness, organic, biodegradable scaffolds in fully load-bearing defects is not only successful but arguably produces significantly improved results when compared with the current Gold Standard, autogenous bone grafting

Aims

This study was designed to characterize the recurrence incidence and risk factors of antibiotic-loaded cement spacer (ALCS) for definitive bone defect treatment in limb osteomyelitis.

Introduction. Segmental defects of the femur present a major problem during revision hip arthroplasty. In particular, calcar segmental defects may compromise initial and long-tem femoral stem stability. Objective. The objective of the present study is to assess mid-term clinical and radiographic follow-up results at least two years after femoral revision comprising reconstruction for calcar segmental defect using metal wire mesh and impacted morcellised allograft. Methods. We performed 26 femoral revisions with calcar reconstruction in 24 patients between 2002 and 2010. The average age was 69.7 years, and the average follow-up period was 5 years and 1 month. All surgeries were performed using a cemented polished collarless tapered stem. The segmental calcar defect was reconstructed with metal wire mesh with doubled stainless wires. Large sized morcellised cancellous allograft was tightly impacted into the cavity between the phantom stem and the metal wire mesh. Nineteen hips were reconstructed with impaction bone grafting of the femur, and 7 hips with cement-in-cement technique except for the reconstructed calcar region.ã�� For clinical assessment, Merle d'Aubigné and Postel hip scores were recorded. For radiological assessment, antero-posterior hip radiographs were analyzed pre-operatively, and post-operatively at one month, 6 months and every 6 months thereafter. Clear lines around the femoral component using Gruen zone classification, stem subsidence in cement mantle, and change of stem axis were recorded. Kaplan-Meier survival analyses were performed with any re-operation of the femoral component or aseptic loosening as end points. In one case, the histological appearance of a biopsy specimen of the most proximal part of the reconstructed calcar, which was obtained at a later surgery for infection at 4 years after the revision, is described. Results. For clinical assessment, the mean Merle d'Aubigné and Postel hip scores improved from 10.4 points before the operation to 14.7 points at the final follow-up. For radiological assessment, no clear lines at the cement-bone interface and no stem axis changes were detected. Twenty-five of 26 hips showed less than 2 mm of stem subsidence at the final follow-up and one hip showed 2.2 mm stem subsidence. Both hips of one female patient underwent a one stage stem exchange because of an infection that occurred 48 months after revision. No cases showed aseptic loosening up to and including the last follow-up. The Kaplan-Meier survival analysis revealed that the survival rate at five years after revision was 88.0% with any type of re-operation on the femoral side as the endpoint and 100% with aseptic stem loosening as the endpoint, respectively. A biopsy specimen taken from the most proximal part of the reconstructed calcar region at 4 years after surgery in the infected case showed almost complete regeneration of viable bone with normal marrow spaces with partially formed granulation tissue. Conclusion. Reconstruction using metal wire mesh and tightly impacted morcellised allograft is a favorable method for the correction a calcar segmental defect. The procedure is simple and reliable, achieving initial and mid-term stem stability even for femurs with a complete calcar defect