Impaction grafting of the acetabulum with a mixture of frozen, ground irradiated bone graft and porous synthetic bone substitute (Apapore 60)

An Observational Prospective Clinical Study for the Evaluation of a Collagen-Hydroxyapatite Composite Scaffold in Hip Revision Surgery

One of the greatest challenges of hip revision surgery is the need to restore extensive bone loss by creating a stable reconstruction with long-term durability. The present observational, investigator-initiated prospective study was carried out to evaluate the clinical and radiological results of the use of a commercial biomimetic collagen-hydroxyapatite composite biomaterial (RegenOss) applied in hip revision surgery. Thirty-three patients who underwent hip revision were included in this study, and 29 received up to 2 years of follow-up. The acetabulum was reconstructed using an uncemented hemispherical shell both with or without an iliac fixation stem. Functional recovery was assessed according to the Harris Hip Score (HHS) at the pre-hospitalisation check-up, and at 6-, 12-, and 24-month follow-ups. Radiological evaluation consisting of X-ray analyses (6, 12, and 24 month follow-ups) and CT scan exams (within 10 weeks post-surgery and at 12-month follow-up) were performed to evaluate the reduction in bone defect and new bone regeneration. All the patients reported a complete recovery and a considerable improvement in functional outcome assessed by the HHS, which was significantly higher at all the follow-ups than at pre-hospitalisation. Moreover, radiological assessments revealed good scaffold integration. Overall, collected data suggest that RegenOss is a valid and safe alternative to restoring acetabular bone loss in revision hip arthroplasty.

Uncemented Cups and Impaction Bone Grafting for Acetabular Bone Loss in Revision Hip Arthroplasty: A Review of Rationale, Indications, and Outcomes

Total hip arthroplasty (THA) is increasingly performed in young patients and the number of revisions is estimated to rise over time. Acetabular osteolysis and bone loss are frequently encountered during revision and may be classified and treated in different ways. Impaction bone grafting (IBG) with morselized allograft offers a viable option. IBG was introduced over 40 years ago in combination with cemented cups, and is also used with uncemented cups. The impacted bone chips act as a void filler to restore bone stock; once incorporated they are substituted by host bone. Surgery entails assessment of the defect, acetabular preparation, preparation of the morselized graft, impaction of the graft, and cup implantation. Satisfactory medium- and long-term results have now been reported in most studies. With the advent of high-porosity cups, indications have been extended, enhancing the potential of IBG, in which primary stability of the cup to the host bone is essential for a successful procedure. Synthetic bone substitutes have also been used in combination with allogenic grafts and may extend the original technique for which long-term studies are warranted.

Minimum 10 years clinical and radiological outcomes of acetabular revisions of total hip arthroplasties with tricalcium phosphate/hydroxyapatite bone graft substitute

BACKGROUND

Aseptic loosening is the most frequent indication for revision of total hip arthroplasty. Revision arthroplasty of acetabular component is a challenge for every surgeon because they have to simultaneously deal with the reconstruction of bone defects, adequate implant geometry and stable fixation. Allografts are the most frequently used materials in reconstruction of bone loss during revision surgeries. Because of an increasing number of revision hip arthroplasties and poor availability of allografts, we decided to use bone graft substitutes in acetabular revisions.

METHODS

Between September 2005 and January 2010, 44 revision arthroplasties in 43 patients were performed with the use of bone graft substitutes for acetabular defect reconstruction in revision of total hip arthroplasty. Acetabular bone defects were classified according to Paprosky. Seventeen hips were classified as IIA, 3 hips IIB, 3 hips IIC, 10 hips IIIA and 11 hips IIIB. Acetabular bone defects were reconstructed with tricalcium phosphate/hydroxyapatite bone graft substitute - BoneSave. Clinical and radiological examination was performed after 3 months, 1 year and then annually. Harris hip score was used for clinical evaluation. Survival analysis was performed with Kaplan-Meier method with aseptic loosening as the definition of endpoint.

RESULTS

The average follow-up period is 12 (range from 10 to 15) years. During the follow-up, three patients died after 24 months because of causes not related to surgery. None of the patients was lost to follow-up. The evaluation of clinical results revealed an increase in pre-operative HHS from average 38.3 (range 25 to 55) points to average 86.3 (range 45 to 95) points at the most recent follow-up. Radiographic evaluation showed the migration of one revision cage 12 months after surgery. Revision arthroplasty performed after 14 months revealed the partial incorporation of bone graft substitute. There were not any cases of loosening of revision acetabular cup at the most recent follow up examination in the remaining 39 patients. Bone graft substitute was not absorbed in all of these patients. The survival after 10 years amounted to 97.56%.

CONCLUSION

Bone graft substitute Bone Save may be suitable for acetabular revision surgery, however preoperative bone defect is critical for success and determining of a surgical technique, so this is multifactorial in this challenge surgery.

Synthetic Bone Grafting in Aseptic Loosening of Acetabular Cup: Good Clinical and Radiological Outcomes in Contained Bone Defects at Medium-Term Follow Up

Restoring bone loss is one of the major challenges when facing hip revision surgery. To eliminate the risk of disease transmission and antigenicity of allografts and donor-morbidity of autografts, the use of synthetic bioceramics has become popular in the last decade. Our study investigated the effectiveness of impaction bone grafting (IBG) of contained acetabular defects (Paprosky 2 and 3a) using a porous ceramic-based hydroxyapatite bone substitute (Engipore, provided by Finceramica Faenza S.p.A., Faenza, Italy) mixed with a low percentage of autologous bone (obtained from reaming when available). We retrospectively assessed 36 patients who underwent acetabular revision using IBG using a porous ceramic-based hydroxyapatite bone substitute with cementless implants with a mean follow-up of 4.4 years. We evaluated, at regular intervals, patients clinically (using the Hip Harris Score and Oxford Score) and radiologically to evaluate the rate of incorporation of the graft, the presence of radiolucent lines or migrations of the cup. Clinical scores significantly improved (WOMAC improved from 49.7–67.30, and the HSS from 56–89). The rate of implants’ survival was 100% at our medium follow-up (4.4 years). We reported five cases of minor migration of the cup, and radiolucent lines were visible in seven patients at the last-follow up. The graft was well-incorporated in all patients. The results presented in this study suggest the HA bone substitute is an effective and safe bone graft when facing hip revision surgery; thus, longer follow-up studies are required.

Long-term results of acetabular reconstruction using irradiated allograft bone

AIMS

The management of acetabular defects at the time of revision hip arthroplasty surgery is a challenge. This study presents the results of a long-term follow-up study of the use of irradiated allograft bone in acetabular reconstruction.

PATIENTS AND METHODS

Between 1990 and 2000, 123 hips in 110 patients underwent acetabular reconstruction for aseptic loosening, using impaction bone grafting with frozen, irradiated, and morsellized femoral heads and a cemented acetabular component. A total of 55 men and 55 women with a mean age of 64.3 years (26 to 97) at the time of revision surgery are included in this study.

RESULTS

At a mean follow-up of 16.9 years, there had been 23 revisions (18.7%), including ten for infection, eight for aseptic loosening, and three for dislocation. Of the 66 surviving hips (58 patients) that could be reassessed, 50 hips (42 patients; 75.6%) were still functioning satisfactorily. Union of the graft had occurred in all hips with a surviving implant. Survival analysis for all indications was 80.6% at 15 years (55 patients at risk, 95% confidence interval (CI) 71.1 to 87.2) and 73.7% at 20 years (eight patients at risk, 95% CI 61.6 to 82.5).

CONCLUSION

Acetabular reconstruction using frozen, irradiated, and morsellized allograft bone and a cemented acetabular component is an effective method of treatment. It gives satisfactory long-term results and is comparable to other types of reconstruction. Cite this article: Bone Joint J 2018;100-B:1449-54.

Increased differentiation and production of extracellular matrix components of primary human osteoblasts after cocultivation with endothelial cells: A quantitative proteomics approach

Coculturing of bone-forming and blood vessel-forming cells is a strategy aimed at increasing vascularity of implanted bone constructs in tissue-engineering applications. We previously described that the coculture of primary human osteoblasts (hOBs) and human umbilical vein endothelial cells (HUVECs) improves the differentiation of both cell types, leading to the formation of functional blood vessels and enhanced bone regeneration. The objective of this study was to further delineate the multifaceted interactions between both cell types. To investigate the proteome of hOBs after cocultivation with HUVECs we used stable isotope labeling by amino acids in cell culture, revealing 49 significantly upregulated, and 54 significantly downregulated proteins. Amongst the highest regulated proteins, we found the proteins important for osteoblast differentiation, cellular adhesion, and extracellular matrix function, notably: connective tissue growth factor, desmoplakin, galectin-3, and cyclin-dependent kinase 6. The findings were confirmed by enzyme-linked immunosorbent assays. We also investigated whether the mRNA transcripts correlate with the changes in protein levels by quantitative real-time reverse transcription polymerase chain reaction. In addition, the data was compared to our previous microarray analysis of hOB transcriptome. Taken together, this in-depth analysis delivers reliable data suggesting the importance of coculturing of hOBs and HUVECs in tissue engineering.

11-Year Mean Follow-Up of Acetabular Impaction Grafting With a Mixture of Bone Graft and Hydroxyapatite Porous Synthetic Bone Substitute

BACKGROUND

We report an 11-year mean follow-up of the effectiveness of bone impaction grafting with bone and hydroxyapatite (HA) for large, uncontained acetabular defects in primary and revision hip surgeries.

METHODS

Over 5 years, 47 total hip arthroplasties with uncontained acetabular deficiencies were performed by augmentation using an impaction graft with 50:50 mixture of freeze-dried bone allograft and HA. Ten were primary total hip arthroplasties and 37 revision procedures. X-rays were taken postoperatively, 6 weeks, 3 months, and then annually to assess incorporation of the graft, radiolucent lines, resorption, or migration of components. Functional outcomes were assessed by annual pain and function parts of the Harris Hip Score.

RESULTS

At a mean follow-up of 10 years, the survivorship was 100%. All patients were accounted for; 6 had died. The Harris Hip Score for pain improved from 9 and 17 (primaries and revisions, respectively) to 39 and 41. For function, there was an improvement from 20 and 19 to 32 (both groups). There were lucent lines in 8 cases, 3 cups had minor/stable migration, and one cup had significant migration (>15 mm). Graft incorporation had occurred in 20 hips.

CONCLUSION

This is the longest survivorship of bone impaction grafting with morcellised bone and HA substitute. Although 11-year survivorship, function and pain are excellent, radiological findings of lysis in 8 and migration in 4 cases may be of concern for the immediate future and will need close monitoring. Even in these cases, revision may be easier because of restoration of bone stock.

Risk factors for failure of revision total hip arthroplasty using a Kerboull-type acetabular reinforcement device

Background

The present study aimed to identify the risk factors associated with revision total hip arthroplasty (THA) failure using a Kerboull-type (KT) plate.

Methods

We analyzed 77 revision THAs using cemented acetabular components with a KT plate for aseptic loosening between May 2000 and March 2012. We examined the association of bone graft type, acetabular bone defects, age at the time of surgery, preoperative Japanese Orthopaedic Association (JOA) score, postoperative JOA hip score, and body mass index, with radiographic failure as the outcome.

Results

The 7.4-year radiographic failure survival rate was 81.6%. The survival rate was significantly different between the beta-tricalcium phosphate (β-TCP) group and the bulk allograft group (p = 0.019). The survival curves were also significantly different between the β-TCP group and bulk allograft group (p = 0.036). American Academy of Orthopaedic Surgeons type IV was significantly associated with radiographic failure (odds ratio [OR]: 15.5, 95% confidence interval [CI]: 1.4–175.4; p = 0.032).

Conclusions

The midterm outcomes of revision THA indicate that type of bone graft and bone defect size may affect radiographic survival rate when using a KT plate.

Bone grafts, bone graft extenders, substitutes and enhancers for acetabular reconstruction in revision total hip arthroplasty

Acetabular bone loss is a relevant concern for surgeons dealing with a failed total hip arthroplasty.

Since the femoral head is no longer available, allografts represent the first choice for most reconstructive solutions, either as a structural buttress or impacted bone chips.

Even though fresh-frozen bone is firmly recommended for structural grafts, freeze-dried and/or irradiated bone may be used alternatively for impaction grafting. Indeed, there are some papers on freeze-dried or irradiated bone impaction grafting, but their number is limited, as is the number of cases.

Xenografts do not represent a viable option based on the poor available evidence but bioactive bioceramics such as hydroxyapatite and biphasic calcium phosphates are suitable bone graft extenders or even substitutes for acetabular impaction grafting.

Bone-marrow-derived mesenchymal stem cells and demineralised bone matrix seem to act as reliable bone graft enhancers, i.e. adjuvant therapies able to improve the biological performance of standard bone grafts or substitutes. Among these therapies, platelet-rich plasma and bone morphogenetic proteins need to be investigated further before any recommendations can be made.

Cite this article: EFORT Open Rev 2016;1:431-439. DOI:10.1302/2058-5241.160025

Bone grafts and their substitutes

The continual cycle of bone formation and resorption is carried out by osteoblasts, osteocytes, and osteoclasts under the direction of the bone-signaling pathway. In certain situations the host cycle of bone repair is insufficient and requires the assistance of bone grafts and their substitutes. The fundamental properties of a bone graft are osteoconduction, osteoinduction, osteogenesis, and structural support. Options for bone grafting include autogenous and allograft bone and the various isolated or combined substitutes of calcium sulphate, calcium phosphate, tricalcium phosphate, and coralline hydroxyapatite. Not all bone grafts will have the same properties. As a result, understanding the requirements of the clinical situation and specific properties of the various types of bone grafts is necessary to identify the ideal graft. We present a review of the bone repair process and properties of bone grafts and their substitutes to help guide the clinician in the decision making process.

Trabecular Metal Use in Paprosky Type 2 and 3 Acetabular Defects: 5-Year Follow-Up

BACKGROUND

The reconstructive challenge of achieving a stable acetabulum in revision total hip arthroplasties in the presence of major osteolytic lesions has led to debate about the most appropriate surgical strategy to minimize implant-related failures. Trabecular metal (TM) implants have become popular but ongoing surveillance of their performance is required.

METHODS

We reviewed the clinical and radiological outcome of a consecutive series of 52 patients (55 hips) who had undergone revision total hip arthroplasty for Paprosky type 2 or 3 acetabular defects with TM revision acetabular shells between 2002 and 2008.

RESULTS

Four implant failures occurred (2 infections and 2 dislocations). Eleven patients from this cohort died (representing 12 hips) before the 5-year follow-up period giving us a follow-up of 78.2%. Implant survival at 5 years was 92% (95% confidence interval: 80.2%-96.9%). There were no cases of radiological loosening. The mean Oxford hip score was 34 (range, 5-48) at a mean follow-up of 63 months (range, 34-105 months).

CONCLUSIONS

We conclude that the use of TM revision shells for complex acetabular reconstruction yields satisfactory results.

The use of calcium carbonate beads containing gentamicin in the second stage septic revision of total knee arthroplasty reduces reinfection rate

BACKGROUND

The aim of the study was to analyze effectiveness and safety of packing the medullary canal of the tibia and femur with Herafill (Heraeus Medical GmbH, Wehrheim, Germany), a void filler and antibiotic carrier, during second stage revision total knee arthroplasty (TKA) for periprosthetic joint infection (PJI).

METHODS

Two groups were formed of 28 consecutive patients during second stage revision TKA, comparable for gender and age. The study group received Herafill, while the control group did not. The average follow-up was 52 months (minimum 36 months).

RESULTS

No reinfections were observed in the study group, while five were seen in the control group. No other differences were observed between the study and control groups, including mean clinical KSS (Knee Society score) (67.4 and 68.4 points, respectively) and functional score (72.5 and 70.5 points respectively). No side effects related to the use of Herafill beads were noted.

CONCLUSIONS

Herafill packed into the tibial and femoral intramedullary canal during second stage of septic revision TKA is a reliable bone substitute, may reduce recurrence of infection and incorporates well with host bone. However, results after PJI treatment are less than optimal measured by KSSs as compared to patients who do not require revision.

The revision acetabulum – allograft and bone substitutes

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.

Influence of thermodisinfection and duration of cryopreservation at different temperatures on pull out strength of cancellous bone

Thermodisinfection of human femoral heads from living donors harvested during hip joint replacement is an established processing procedure. This study was designed to examine the influence of heat sterilization on pull out strength of cancellous bone and storage at different temperatures up to 2 years since we had previously studied the storage of unprocessed cancellous bone. Porcine cancellous bone resembling human bone structure was obtained from 140 proximal humerus of 6-8 months old piglets. Pull out strength of screws after thermodisinfection was compared with unprocessed cancellous bone and tested immediately and after 6, 12 and 24 months of storage at -20 and -80 °C. A three-way ANOVA was performed and significance level was 5 %. The thermodisinfected bone showed a pull out force of 2729 N (1657-3568 N). The reduction of pull out strength compared with unprocessed bone over all periods of storage was 276 N on average with 95 % confidence interval ranging from 166 N to 389 N (p < 0.0001). Different freezing temperatures did not influence this mechanic property within 24 months storage and showed no difference compared with fresh frozen bone. Thermodisinfection of cancellous bone preserves tensile strength necessary for clinical purposes. The storage at -20 °C for at least 2 years did not show relevant decrease of pull out strength compared with -80 °C without difference between thermodisinfected and fresh frozen bone. The increase of the storage temperature to -20 °C for at least 2 years should be considered.

Impaction grafting of the acetabulum with ceramic bone graft substitute: high survivorship in 43 patients with a mean follow-up period of 4 years

BACKGROUND AND PURPOSE

Loss of bone stock remains a challenge in revision hip surgery. Grafting with allograft is well established, but there are problems with availability, cost, infection, antigenicity, reproducibility, and stability of the created construct. BoneSave is a biphasic porous ceramic consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite. In vitro and in vivo studies, including its use mixed with allograft, have shown good results in impaction grafting. This is the first reported series of its use alone in impaction grafting of the acetabulum.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single centre. All patients received uncemented acetabular components. They were followed up radiographically, together with self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Mean follow-up was 4 years. 5 patients died during follow-up, with their constructs in situ. The survivorship of the acetabular component was 98% (95% CI: 85-100) at 7 years. 1 acetabular component was revised for infection and there was 1 radiographic acetabular failure. The median OHS was 36 (6-48), the median SF12 PCS was 36 (14-57), the median SAPS was 75 (0-100), and the median SF12 MCS was 50 (23-64). The graft material had incorporated in all 3 zones of the acetabulum in 33 out of 37 cases with complete radiographic follow-up.

INTERPRETATION

Medium-term results show that BoneSave alone is a reliable material for impaction grafting of contained defects in the acetabulum at revision surgery.

Impaction grafting of the acetabulum with ceramic bone graft substitute mixed with femoral head allograft: high survivorship in 43 patients with a median follow-up of 7 years: a follow-up report

BACKGROUND AND PURPOSE

Restoration of bone stock at revision hip surgery remains a challenge. Alternative graft materials with suitable mechanical properties for impaction grafting have been sought due to issues with infection, antigenicity, cost, and availability of allograft. We have previously presented good short-term results of the use of BoneSave, a biphasic porous ceramic bone graft substitute, consisting of sintered 80% tricalcium phosphate and 20% hydroxyapatite, in a 50:50 mix with femoral head allograft. We now present the medium-term results.

METHODS

We conducted a retrospective review of a cohort of 43 consecutive patients undergoing impaction grafting of contained acetabular defects by multiple surgeons at a single center. 34 patients received uncemented acetabular components and 9 received cemented components. Patients were followed up radiographically and with the self-reported satisfaction scale (SAPS), Oxford hip score (OHS), and the Short-Form 12 (SF12) health survey. Kaplan-Meier survivorship analysis was performed with revision of the acetabular component, revision of any part of the construct, and reoperation as endpoints.

RESULTS

The fate of all cases was known. Median follow-up of the surviving patients was 80 (69-106) months. 15 patients died during the follow-up period, 14 with their construct in situ. The survivorship of the grafted acetabulum and acetabular component was 94% (95% CI: 99-78) at 7 years. 1 patient had been revised for aseptic loosening of the acetabulum and 1 for deep infection. The mean OHS was 31 (SD 12), the mean SF12 physical-component score (PCS) was 38 (SD 13), the median SAPS was 83 (0-100), and the median SF12 mental-component score (MCS) was 55 (23-65). The graft material became incorporated in all 3 zones of the acetabulum in 23 out of 24 cases that had complete radiographic follow-up.

INTERPRETATION

These medium-term results show that BoneSave is a reliable material for impaction grafting of the acetabulum when used in conjunction with femoral head allograft.

Bone graft substitutes currently available in orthopaedic practice: the evidence for their use

We reviewed 59 bone graft substitutes marketed by 17 companies currently available for implantation in the United Kingdom, with the aim of assessing the peer-reviewed literature to facilitate informed decision-making regarding their use in clinical practice. After critical analysis of the literature, only 22 products (37%) had any clinical data. Norian SRS (Synthes), Vitoss (Orthovita), Cortoss (Orthovita) and Alpha-BSM (Etex) had Level I evidence. We question the need for so many different products, especially with limited published clinical evidence for their efficacy, and conclude that there is a considerable need for further prospective randomised trials to facilitate informed decision-making with regard to the use of current and future bone graft substitutes in clinical practice.

The Burch-Schneider cage: 9-year survival in Paprosky type 3 acetabular defects. Clinical and radiological follow-up

Revision hip arthroplasty in cases with severe acetabular deficiency represents a technical challenge. The aim of this study was to determine: 1. The 9-year survival of the Burch Schneider anti-protrusio cage (BS-APC) in severe acetabular defects. 2. The migration of the cage and correlation of this with functional outcome. 3. The anticipated functional outcome users can expect in a district general hospital setting in the management of severe acetabular defects. A single-surgeon consecutive series of 30 complex acetabular reconstructions using the BS-APC was retrospectively reviewed. Clinical and radiological follow up at 5-9 years was obtained. Survival was established with revisions and further surgery as different end-points. A radiological analysis using ein bilt roentgen analyse (EBRA) was performed. At a mean follow-up of 85 months (range: 64-118) 26 patients (87%) were alive. Nine-year survival was 95% for revision of BS-APC as an end-point and 92% with any cause of further surgery as an end-point. The mean Oxford Hip Score was 34.5 and UCLA activity score was 4.4. All cases demonstrated evidence of significant migration, but no screws were found to be broken. There was no correlation between cup migration and Oxford hip score (p=0.07). Our non-specialist centre experience suggests the BS-APC should not be dismissed as a reconstruction option in the most severe acetabular defects.

Supercritical CO2 fluid-foaming of polymers to increase porosity: a method to improve the mechanical and biocompatibility characteristics for use as a potential alternative to allografts in impaction bone grafting?

Disease transmission, availability and cost of allografts have resulted in significant efforts to find an alternative for use in impaction bone grafting (IBG). Recent studies identified two polymers with both structural strength and biocompatibility characteristics as potential replacements. The aim of this study was to assess whether increasing the polymer porosity further enhanced the mechanical and cellular compatibility characteristics for use as an osteogenic biomaterial alternative to allografts in IBG. Solid and porous poly(DL-lactide) (P(DL)LA) and poly(DL-lactide-co-glycolide) (P(DL)LGA) scaffolds were produced via melt processing and supercritical CO(2) foaming, and the differences characterized using scanning electron microscopy (SEM). Mechanical testing included milling and impaction, with comparisons made using a shear testing rig as well as a novel agitation test for cohesion. Cellular compatibility tests for cell number, viability, and osteogenic differentiation using WST-1 assays, fluorostaining, and ALP assays were determined following 14 day culture with skeletal stem cells. SEM showed excellent porosity throughout both of the supercritical-foam-produced polymer scaffolds, with pores between 50 and 200 μm. Shear testing showed that the porous polymers exceeded the shear strength of allograft controls (P<0.001). Agitation testing showed greater cohesion between the particles of the porous polymers (P<0.05). Cellular studies showed increased cell number, viability, and osteogenic differentiation on the porous polymers compared to solid block polymers (P<0.05). The use of supercritical CO(2) to generate porous polymeric biodegradable scaffolds significantly improves the cellular compatibility and cohesion observed compared to non-porous counterparts, without substantial loss of mechanical shear strength. These improved characteristics are critical for clinical translation as a potential osteogenic composite for use in IBG.

Improving initial acetabular component stability in revision total hip arthroplasty calcium phosphate cement vs reverse reamed cancellous allograft

A reproducible retroacetabular defect was created bilaterally in 9 cadaver pelves. The defects were filled with either an injectable, bioresorbable, calcium phosphate cement, or reverse-reamed cancellous allograft. An uncemented acetabular shell was impacted, followed by the placement of an appropriate liner. The pelves were then sectioned, and each half was loaded in a material testing machine to simulate walking on the construct over a several week period. The cement-filled defects lasted a greater number of cycles before failure and had greater cup stability and stiffness. The use of resorbable bone void filler for retroacetabular defects shows promise in this biomechanical analysis. Long-term clinical follow-up is warranted to track osseointegration of the implant and restoration of bone stock between this and other clinically accepted surgical techniques.

A preclinical study of stem subsidence and graft incorporation after femoral impaction grafting using porous hydroxyapatite as a bone graft extender

This preclinical in vivo screening study compared bone graft incorporation and stem subsidence in cemented hemiarthroplasty after femoral impaction bone grafting with either morselized allograft bone (n = 5, control group) or a 1:1 mix of allograft and porous hydroxyapatite ceramics (HA) granules (n = 5, HA group). At 14 weeks, there was excellent bone graft incorporation by bone, and the stems were well fixed in both groups. The median subsidence at the cement-bone interface, measured using radiostereometric analysis, was 0.14 and 0.93 mm in the control and HA groups, respectively. The comparable histologic results between groups and good stem fixation in this study support the conduct of a larger scale investigation of the use of porous HA in femoral impaction bone grafting at revision hip arthroplasty.

Bone graft substitutes in hip revision surgery: a comprehensive overview

INTRODUCTION

Total hip replacement is increasingly used to treat diseased and damaged joints. With time, some joint replacements may require revision, mainly because of instability and mechanical loosening, and this is of particularly significance to younger patients. A major problem in revision surgery is the loss of bone stock and the consequent difficulty in reconstructing a stable joint. Loss of bone stock has been widely treated using bone autografts and allografts but supplies are limited. Use of bone graft substitutes in combination with, or as a substitute for, human bone is a possible alternative.

AIM

To identify empirical studies of bone graft substitutes in hip revision surgery.

METHODS

Systematic review based on Cochrane and MOOSE methods. We searched MEDLINE and EMBASE to December 2010 with terms relating to hip replacement and bone graft substitutes, and checked key citations in ISI Web of Science and reference lists. We considered all human studies irrespective of study design.

RESULTS

Searches identified 397 articles. Screening of abstracts and full text articles identified 7 studies reporting outcomes of bone-graft substitute combined with autograft or allograft, and 6 studies reporting outcomes of bone graft substitute exclusively. One economic evaluation compared costs of femoral head banking with costs of bone graft substitutes. No randomised controlled trials evaluating bone graft substitute effectiveness were identified. Studies generally included small numbers of patients with a follow up too short to assess outcomes relating to implant survival. However, excepting those based on glass ceramic, ceramic bone graft substitutes show promise as an alternative to use of exclusive autograft or allograft. In the case of calcium phosphate ceramic bone graft substitute, potential cost savings were evident.

CONCLUSION

With increased allograft shortage, bone graft substitutes will be required in hip revision surgery. However, appropriately designed randomised controlled trials are required to compare use of existing and new bone graft substitutes with established practice. As well as prosthesis related outcomes, studies should explore the patient experience of revision hip replacement with bone graft substitute material.

The use of bone-graft substitutes in large bone defects: any specific needs?

INTRODUCTION

The gold standard for restoring bone defects is still considered to be autologous bone grafting. However, clinical benefits are not guaranteed and donor-site complications and morbidity is not infrequent. Research is on-going for the development of alternative bone substitutes of both biological and synthetic origin. The purpose of this study was to evaluate the type of materials used and their efficacy for the treatment of large bone defects in traumatology and orthopaedic surgery.

MATERIALS AND METHOD

A literature review was carried out of Embase and PubMed databases. Inclusion criteria were articles in English language focusing on the use of bone substitutes in trauma and orthopaedic surgery for the treatment of bone defects and included details on the structural, biological or biomechanical properties of the pure product. Furthermore, based on two clinical challenges, fracture non-union and impaction grafting we elaborated on the use of polytherapy for large bone defects as guided by the diamond concept.

RESULTS

All the products indicated in this manuscript possess osteoconductive activities but have different resorption times and biomechanical properties. Bone graft substitute materials are used for a wide range of clinical applications even when the level of clinical evidence is low. The size and location of the defect and the local biological and mechanical environment as well as the biomechanical characteristics of the material determine the type of device that can be implanted in a bone defect.

CONCLUSION

Proper assessment of the biological and mechanical environment and accurate patient selection are necessary to judge the extent of therapy the injury warrants. A sound understanding of various aspects of biomaterial properties and their relation and influence towards bone healing is of utmost importance. We suggest the application of polytherapy for the treatment of large bone defects and advocate the use of the diamond concept as a guideline.

Impaction bone grafting

In revision total hip replacement, bone loss can be managed by impacting porous bone chips. In order to guarantee sufficient mechanical strength, the bone chips have to be compacted. The aim of this study was to determine in an in vitro simulation whether the use of a pneumatic hammer leads to higher primary stability than manual impaction. Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. From these measurements bulk density, contact stiffness, impaction hardness and penetration resistance were calculated for different durations of impaction.

We found that the pneumatic method reached higher values of impaction hardness, contact stiffness and bulk density suggesting an increase in stability of the implant. No significant differences were found between the two different methods concerning the penetration resistance. The pneumatic method might reduce the risk of fracture in vivo, as force peaks are smaller and applied for a shorter period. Results from manual impaction showed higher variability and depend much on the experience of the surgeon. The pneumatic hammer is a suitable tool to standardise the impaction process.

The use of scaffolds in musculoskeletal tissue engineering

The use of bioengineering scaffolds remains an integral part of the tissue engineering concept. A significant amount of basic science and clinical research has been focused on the regeneration of musculoskeletal tissues including bone, articular cartilage, meniscus, ligament and tendon. This review aims to provide the reader with a summary of the principals of using material scaffolds in musculoskeletal tissue engineering applications and how these materials may eventually come to be incorporated in clinical practice.

Effect of vibration on the shear strength of impacted bone graft in revision hip surgery

We developed a method of applying vibration to the impaction bone grafting process and assessed its effect on the mechanical properties of the impacted graft. Washed morsellised bovine femoral heads were impacted into shear test rings. A range of frequencies of vibration was tested, as measured using an accelerometer housed in a vibration chamber. Each shear test was repeated at four different normal loads to generate stress-strain curves. The Mohr-Coulomb failure envelope from which shear strength and interlocking values are derived was plotted for each test. The experiments were repeated with the addition of blood in order to replicate a saturated environment.

Graft impacted with the addition of vibration at all frequencies showed improved shear strength when compared with impaction without vibration, with 60 Hz giving the largest effect. Under saturated conditions the addition of vibration was detrimental to the shear strength of the aggregate. The civil-engineering principles of particulate settlement and interlocking also apply to impaction bone grafting. Although previous studies have shown that vibration may be beneficial in impaction bone grafting on the femoral side, our study suggests that the same is not true in acetabular revision.

Large acetabular defects can be managed with cementless revision components

BACKGROUND

Optimal techniques for acetabular revision in the setting of major pelvic osteolysis have not been established. Bilobed components, structural grafts, and reinforcement cages have demonstrated 10-24% midterm failure rates. While cementless hemispherical components have been utilized to treat large acetabular defects, most reports have not focused specifically on patients with extensive deficiencies.

QUESTIONS/PURPOSES

We report midterm clinical scores, component revisions, and complications following focal bone grafting and cementless acetabular revision in cases with major periacetabular osteolysis.

METHODS

We identified 30 patients (32 hips) who underwent cementless acetabular revision to treat massive acetabular bone loss at an average followup of 53 months. We excluded three patients lost to followup and two patients who died prior to minimum 24 month followup. Harris Hip Scores were assessed before and after surgery. Postoperative radiographs were evaluated for graft incorporation and component migration. Component revision and component migration are reported as failures.

RESULTS

Mean Harris Hip Score improved from 52.5 (range, 17.7-90.7) to 87.3 (range, 25.3-100) points. Three hips (9%) were revised for aseptic loosening. Three components (10.7%) demonstrated radiographic migration, but were not revised. Complete graft incorporation was seen in 17 cases (68%). There were five major complications (14%).

CONCLUSIONS

Cementless acetabular fixation and bone grafting result in clinical scores and survivorship comparable to other options at midterm followup, with potential for biological fixation.

LEVEL OF EVIDENCE

Level IV, clinical research study. See the Guidelines for Authors for a complete description of levels of evidence.