Femoral impaction grafting in revision hip arthroplasty with irradiated bone

Bone morphogenic protein-2 use in revision total hip arthroplasty with acetabular defects

INTRODUCTION

The restoration of acetabular bone stock during revision hip arthroplasty remains a challenge. There have been no clinical series reporting the efficacy of bone morphogenic protein-2 (rhBMP-2) in the revision hip setting.

METHODS

We retrospectively reviewed the radiographs and records of 15 patients who received rhBMP-2 mixed with allograft bone chips (+BMP), and 14 who received allograft bone chips alone (-BMP) for their acetabular defect during revision total hip arthroplasty with a mean two-year follow up. Radiographs were evaluated for acetabular defect size, superior cup migration, and changes in the lateral cup abduction angle. Modified Harris hip scores were used for evaluation of clinical outcomes.

RESULTS

Patients in the +BMP group compared to the -BMP group had significantly larger amounts of cancellous bone chips used (72.1 ± 35.5 cc vs. 38.6 ± 14.1 cc; p = 0.003). Mean rhBMP-2 used per case was 7.4 ± 3.1 mg in the +BMP group. Three patients in the -BMP group had cup migration which was not observed in the +BMP group. Mean Harris hip scores (HHS) improved post-operatively in both groups (40.1 ± 20.9 to 71.9 ± 19, p < .0001). No local adverse reaction was noted in the +BMP group.

CONCLUSION

rhBMP-2 had modest clinical benefit in the setting of revision THA. Cost of this synthetic biologic versus the added clinical benefit should be carefully considered when being used in the revision hip setting.

Femoral impaction bone grafting in revision hip arthroplasty

Aims

Femoral impaction bone grafting was first developed in 1987 using morselised cancellous bone graft impacted into the femoral canal in combination with a cemented, tapered, polished stem. We describe the evolution of this technique and instrumentation since that time.

Patients and Methods

Between 1987 and 2005, 705 revision total hip arthroplasties (56 bilateral) were performed with femoral impaction grafting using a cemented femoral stem. All surviving patients were prospectively followed for a mean of 14.7 years (9.8 to 28.3) with no loss to follow-up. By the time of the final review, 404 patients had died.

Results

There were 76 further revisions (10.8%) involving the stem; seven for aseptic loosening, 23 for periprosthetic fracture, 24 for infection, one for malposition, one for fracture of the stem and 19 cement-in-cement exchanges of the stem during acetabular revision. The 20-year survival rate for the entire series was 98.8% (95% confidence interval (CI) 97.8 to 99.8) with aseptic loosening as the endpoint, and 87.7% (95% CI 82.8 to 92.6) for revision for any reason. Survival improved with the evolution of the technique, although this was not statistically significant due to the overall low rate of further revision.

Conclusion

This is the largest series of revision total hip arthroplasties with femoral impaction grafting, and the results support the continued use of this technique. Cite this article: Bone Joint J 2016;98-B:1611–19.

Clinical trial and in-vitro study comparing the efficacy of treating bony lesions with allografts versus synthetic or highly-processed xenogeneic bone grafts

Background

Our study aim was to compare allogeneic cancellous bone (ACB) and synthetic or highly-processed xenogeneic bone substitutes (SBS) in the treatment of skeletal defects in orthopedic surgery.

Methods

232 patients treated for bony lesions with ACB (n = 116) or SBS (n = 116) within a 10-year time period were included in this case–control study. Furthermore, both materials were seeded with human osteoblasts (hOB, n = 10) and analyzed by histology, for viability (AlamarBlue®) and protein expression activity (Luminex®).

Results

The complication rate was 14.2 %, proportion of defects without bony healing 3.6 %; neither outcome parameter differed comparing the intervention groups. Failed consolidation correlated with an increase in complications (p < 0.03). The rate of complications was further highly significant in association with the location of use (p < 0.001), but did not depend on age, ASA risk classification, BMI, smoking behavior or type of insurance. However, those factors did significantly influence the bony healing rate (p < 0.02). Complication and consolidation rates were independent of gender and the filling substances employed within the different locations. Histological examination revealed similar bone structures, whereas cell remnants were apparent only in the allografts. Both materials were biocompatible in-vitro, and seeded with human osteoblasts. The cells remained vital over the 3-week culture period and produced microscopically typical bone matrix. We observed initially increased expression of osteocalcin, osteopontin, and osteoprotegerin as well as leptin and adiponectin secretion declining after 1 week, especially in the ACB group.

Conclusion

Although both investigated materials appeared to be similarly suitable for the treatment of skeletal lesions in-vivo and in-vitro, outcome was decisively influenced by other factors such as the site of use or epidemiological parameters.

Supercharging irradiated allografts with mesenchymal stem cells improves acetabular bone grafting in revision arthroplasty

PURPOSE

The procedure of bone allografting associated with a reinforcement device is widely used for acetabulum revision. However in absence of biologic fixation of the allograft, failure of the reconstruction may occur. We made the hypothesis that it would be possible to load these grafts with bone marrow derived mesenchymal stem cells (MSC) to rescue the osteogenic capacity of an allogenic dead bone and therefore enhance incorporation of allografts with the host bone and decrease the number of failures related to the allograft.

METHOD

We identified 60 patients who had undergone acetabular component revision for aseptic failure of cemented implants associated with massive periacetabular osteolysis and Paprosky type 3A or 3B classification (without pelvic discontinuity) between 1996 and 2001. The study group of 30 patients received MSCs in the allograft and at the host graft junction. The average total number of MSCs received by each patient was 195,000 cells (range 86,000-254,000 cells). The control group of 30 patients had no MSCs in the allograft. Patients were matched for the size of periacetabular osteolysis (Paprosky type 3A or 3B). We compared the evolution of the allografts and evaluated cup migration and revision of the hips as end points at a minimum of 12 years or until failure.

RESULT

Better radiographic graft union rates and less allograft resorption were observed with allografts loaded with stem cells. Allograft resorption was significantly decreased in the group with allograft loaded with MSCs (1.2 cm(2) -range 0-2.3 cm(2)-of resorption on radiographs in the group with MSCs; versus 6 cm(2), range 2.1-8.5 cm(2) in the group without MSCs). The rate of mechanical failure was highest (p = 0.01) among the 30 patients with allograft without stem cells (9/30; 30 %) compared with no failures for patients with allograft loaded with stem cells. Revision of the cup was necessary in nine patients in the control group. No revision was performed in the 30 patients of the study group with MSCs.

CONCLUSION

For acetabular defect reconstruction, loading the allograft with MSCs has resulted in a lower rate of failure as compared with allograft without MSCs.

Stem micromotion after femoral impaction grafting using irradiated allograft bone: a time zero in vitro study

BACKGROUND

A gamma irradiation dose of 15kGy has been shown to adequately sterilise allograft bone, commonly used in femoral impaction bone grafting to treat bone loss at revision hip replacement, without significantly affecting its mechanical properties. The objective of this study was to evaluate whether use of 15kGy irradiated bone affects the initial mechanical stability of the femoral stem prosthesis, as determined by micromotion in a comprehensive testing apparatus, in a clinically relevant time zero in vitro model of revision hip replacement.

METHODS

Morselised ovine bone was nonirradiated (control), or irradiated at 15kGy or 60kGy. For each dose, six ovine femurs were implanted with a cemented polished taper stem following femoral impaction bone grafting. Using testing apparatus that reproduces stem loading, stems were cyclically loaded and triaxial micromotion of the stem relative to the bone was measured at the proximal and distal stem regions using non-contact laser transducers and linear variable differential transformers.

FINDINGS

There were no significant differences in proximal or distal stem micromotion between groups for all directions (p≤0.80), apart for significantly greater distal stem medial-lateral micromotion in the 60kGy group compared to the 15kGy group (P=0.03), and near-significance in the anterior-posterior direction (P=0.08, power=0.85).

INTERPRETATION

Using a clinically relevant model and loading apparatus, irradiation of bone at 15kGy does not affect initial femoral stem stability following femoral impaction bone grafting.

A customised collared polished stem may reduce the complication rate of impaction grafting in revision hip surgery: a 12-year follow-up study

We describe the results of 81 consecutive revision total hip replacements with impaction grafting in 79 patients using a collared polished chrome-cobalt stem, customised in length according to the extent of distal bone loss. Our hypothesis was that the features of this stem would reduce the rate of femoral fracture and subsidence of the stem. The mean follow-up was 12 years (8 to 15). No intra-operative fracture or significant subsidence occurred. Only one patient suffered a post-operative diaphyseal fracture, which was associated with a fall. All but one femur showed incorporation of the graft. No revision for aseptic loosening was recorded. The rate of survival of the femoral component at 12 years, using further femoral revision as the endpoint, was 100% (95% confidence interval (CI) 95.9 to 100), and at nine years using re-operation for any reason as the endpoint, was 94.6% (95% CI 92.0 to 97.2). These results suggest that a customised cemented polished stem individually adapted to the extent of bone loss and with a collar may reduce subsidence and the rate of fracture while maintaining the durability of the fixation.

Acetabular impaction grafting in total hip replacement

BACKGROUND AND PURPOSE

Acetabular impaction grafting has been shown to be very effective, but concerns regarding its suitability for larger defects have been highlighted. We report the use of this technique in a large cohort of patients, and address possible limitations of the technique.

METHODS

We investigated a consecutive group of 339 cases of impaction grafting of the cup with morcellised impacted allograft bone for survivorship and mechanisms for early failure.

RESULTS

Kaplan Meier survival was 89.1% (95% CI 83.2 to 95.0%) at 5.8 years for revision for any reason, and 91.6% (95% CI 85.9 to 97.3%) for revision for aseptic loosening of the cup. Of the 15 cases revised for aseptic cup loosening, nine were large rim mesh reconstructions, two were fractured Kerboull-Postel plates, two were migrating cages, one was a medial wall mesh failure and one had been treated by impaction alone.

INTERPRETATION

In our series, results were disappointing where a large rim mesh or significant reconstruction was required. In light of these results, our technique has changed in that we now use predominantly larger chips of purely cancellous bone, 8-10 mm3 in size, to fill the cavity and larger diameter cups to better fill the aperture of the reconstructed acetabulum. In addition we now make greater use of i) implants made of a highly porous in-growth surface to constrain allograft chips and ii) bulk allografts combined with cages and morcellised chips in cases with very large segmental and cavitary defects.

Bioactive and osteoinductive bone graft substitutes: definitions, facts and myths

The use of artificial bone grafts has been developed over recent years and is expected to increase further, for some indications even replacing the gold standard, autograft, in trauma and reconstructive surgery. However, the effectiveness of these materials is still a subject of debate, mostly because of unclear definitions or limited market surveillance. In this overview several facts and myths regarding bone-graft substitutes are summarized.

Intra-operative washing of morcellised bone allograft with pulse lavage: how effective is it in reducing blood and marrow content?

The use of unprocessed bone carries a risk of transmission of blood borne diseases. Although models of infectivity are unproven, a theoretical risk of transmission of variant Creutzfeld-Jakob Disease, a human prion disease, exists as probable blood borne transmission has been reported in three cases. The aim of our study was to determine the effectiveness of standard operating theatre pulse lavage in removing protein, fat and double stranded Deoxyribonucleic acid (dsDNA) from morcellised bone allograft. Twelve donated femoral heads were divided into halves and milled into bone chips. One half of the bone chips were washed with pulse lavage, whereas, the other half acted as control. In order to determine the amount of protein, fat and dsDNA present in the washed and unwashed samples, a validated multistep washing protocol was used. Using the validated technique, simple intra-operative washing of morcellised unprocessed bone allograft removed a significant amount of the protein (70.5%, range: 39.5-85%), fat (95.2%, range: 87.8-98.8%) and DNA (68.4%, range: 31.4-93.1%) content. Intra-operative washing of morcellised bone allograft with pulse lavage may thereby reduce the theoretical risk of prion and other blood borne disease transmission. Combined with the known improved mechanical characteristics of washed allograft, we would recommend pulse lavage as a routine part of bone allograft preparation.

Reduced femoral component subsidence with improved impaction grafting at revision hip arthroplasty

BACKGROUND

Despite stem subsidence being a major complication of femoral impaction bone grafting in cemented revision hip arthroplasty, few studies have distinguished subsidence at the prosthesis-cement interface from that at the cement-bone interface. It is unknown how technique developments intended to improve the procedure influence stability of the stem.

QUESTIONS/PURPOSES

We used a sensitive technique to measure subsidence of a cemented polished collarless double-taper stem at each interface after femoral impaction grafting and compared subsidence, radiographic loosening, complications, and reoperations over three series of hips defined by technique developments.

PATIENTS AND METHODS

Three series were defined: Series 1 (n = 23, irradiated allograft), Series 2 (n = 12, double-washed, size-profiled graft, nonirradiated bone, long stems as required), and Series 3 (n = 21, modular tamps). Stem subsidence was analyzed with Ein Bild Röntgen Analyse software. Radiographic loosening, complications, and reoperations were also determined.

RESULTS

The median subsidence at 12 months for Series 1, 2, and 3 were 2.1, 0.5, and 0.7 mm at the prosthesis-cement interface and 1.3, 0.1, and 0.1 mm at the cement-bone interface. There were two postoperative Vancouver B periprosthetic fractures in Series 1, four hips were revised for loosening in Series 1, and there were no fractures or loosening in Series 2 and 3 at minimum 2 years' followup. There were no surviving hips radiographically classified as possibly or probably loose.

CONCLUSIONS

Evolution in techniques of femoral impaction grafting in this study were associated with reduced subsidence of the stem at both the prosthesis-cement interface and cement-bone interface when compared to the original series. Concurrent with reduced stem subsidence was the absence of periprosthetic fracture, radiographic loosening, and complications requiring rerevision.

Influence of cement penetration and graft density on stem stability in impaction allografting: a finite element study

BACKGROUND

Excessive stem migration is often problematic after impaction allografting. The mechanisms responsible for migration are not known, but achieving a dense graft bed has traditionally been believed to be essential for stem stability. When the stem is cemented into the allograft bed, however, the graft becomes infiltrated with bone cement. Extensive cement penetration into the graft has been observed in previous studies, resulting in regions of cement-endosteum contact.

METHODS

This study explored the effects of graft density and cement penetration on stem motion using a finite element model that was validated against experimental data.

FINDINGS

Cement penetration has a considerable stabilizing effect on stem motion, whereas graft density is important only when there is no cement-endosteum contact. Stem migration can be attributed primarily to slippage at the endosteum and stem-cement interfaces rather than to shear failure within the graft.

INTERPRETATION

Partial cement penetration to the endosteum increases the likelihood of meeting clinical requirements of early implant stability, particularly when a dense graft bed cannot be achieved.

Fresh-frozen vs. irradiated allograft bone in orthopaedic reconstructive surgery

The use of allograft bone is increasingly common in orthopaedic reconstruction procedures. The optimal method of preparation of allograft bone is subject of great debate. Proponents of fresh-frozen graft cite improved biological and biomechanical characteristics relative to irradiated material, whereas fear of bacterial or viral transmission warrants some to favour irradiated graft. Careful review of the literature is necessary to appreciate the influence of processing techniques on bone quality. Whereas limited clinical trials are available to govern the selection of appropriate bone graft, this review presents the argument favouring the use of fresh-frozen bone allograft as compared to irradiated bone.

Processed versus fresh frozen bone for impaction bone grafting in revision hip arthroplasty

BACKGROUND

Impaction grafting is a technique to restore bone loss both in the femur and the acetabulum during revision hip arthroplasty surgery. Initially impaction grafting was undertaken using fresh frozen femoral head allografts that were milled to create morselized bone pieces that could be impacted to create a neo-cancellous bone bed prior to cementation of the new implant. Results of medium and long term outcome studies have shown variable results using this technique. Currently both processed and non-processed allograft bone are used and the purpose of this review was to analyse the evidence for both.

OBJECTIVES

To determine the clinical effectiveness of processed (freeze dried or irradiated) bone in comparison to fresh frozen (unprocessed) bone.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1985 to 2008), EMBASE (1985 to 2008), CINAHL(1985 to 2008) and the National Research Register. Additional sources were also searched. Handsearching of relevant journals and conference abstracts was also undertaken. Searches were complete to 31 August 2008.

SELECTION CRITERIA

Randomised controlled trials that compared different types of bone for impaction grafting.

DATA COLLECTION AND ANALYSIS

Three hundred and sixty references were identified from the searches. Following detailed eligibility screening, three hundred and fifty nine references did not meet the eligibility criteria. Further details are required about one trial in order to determine it's eligibility.

MAIN RESULTS

No trials were identified that met the criteria for inclusion in the review.

AUTHORS' CONCLUSIONS

Good quality randomised controlled trials are required in this area so that a surgeon's choice of bone graft can be informed by evidence rather than personal preference.

Use of irradiated bone graft for impaction grafting in acetabular revision surgery: a review of fifty consecutive cases

Impaction bone grafting is a useful technique in the armament of a revision hip surgeon. Traditionally fresh frozen allograft has been used for this technique. However there are concerns about the transmission of viral proteins and prions through this form of allograft. As a result irradiated bone graft has been favoured in some centres. There is no long term series describing the results of impaction bone grafting using irradiated bone. This paper reviews a consecutive series of 50 cases of acetabular revision surgery performed between 1995 and 2001 and followed up over a mean period of 45 months. The preoperative bone defect was graded by the Paprosky classification. There were 2 cases of type 1a, 9 type 2a, 15 type 2b, 7 type 2c, 10 type 3a and 7 type 3b. All cases were followed up clinically and radiologically. Case notes were reviewed for primary prosthesis, operative details and reason for revision. The radiographs were evaluated for signs of bone incorporation, remodelling, loosening and migration of the acetabular component. There were 5 cases of aseptic loosening at the end of the follow up period. One patient had recurrent dislocation and was revised. 20 cases (40%) showed changes suggestive of bone incorporation, while only 3 cases (6%) showed remodelling. Clinically a good or excellent outcome with absence of pain was achieved in 35 patients (70%). The results suggested that acetabular impaction bone grafting using irradiated bone graft is comparable to fresh frozen allograft. The low percentage of remodelling remains a concern and warrants further studies.

Allograft and bone morphogenetic proteins: an overview

Allograft is frequently used in orthopaedic and trauma surgery. On top of safety issues its biological activity is limited also due to processing. Consequently, the combination of allograft with osteoinductive substances may increase its effectiveness and decrease failure rates. In particular Bone Morphogenetic Proteins (BMPs) seem to be a promising partner for clinical applications. This overview focuses on the combined application of allograft/BMPs. Current points of view from available literature are summarized.

The effect of preoperative planning and impaction grafting surgical technique on intraoperative and postoperative complication rate for femoral revision patients with moderate to severe bone loss mean 4.7-year results

This study reports the results of 41 revision hips, implanted by a single surgeon using impaction grafting (mean follow-up, 4.7 years). All hips had Paprosky scores of III or IV. Harris hip scores improved from 43 to 82. There was 1 intraoperative and 2 postoperative fractures. A single stem was revised during the study. Radiographic review showed the 40 unrevised stems to be stable, and graft incorporation was seen in at least 1 zone in 100% of the femurs. There was no stem subsidence greater than 2.5 mm. The results of this study demonstrate that preoperative planning and a surgical technique, which emphasizes femoral support and vigorous impaction grafting, resulted in an acceptable incidence of complications.

Extensively porous-coated stems for femoral revision: a choice for all seasons

We reviewed the outcome of 905 femoral revisions performed at our institution between June 1980 and August 2006 using extensively porous-coated, cylindrical stems. A total of 20 femoral rerevisions were identified, including 12 for aseptic loosening, 4 for infection, 3 for stem fracture, and 1 in conjunction with a periprosthetic femur fracture. All stem rerevisions occurred within the first 10 years after surgery. Kaplan-Meier survivorship, using stem rerevision for any reason as an end point, was 97.5% +/- 1.3% (95% confidence intervals) at 5 years, declined to 95.9% +/- 1.9% at 10 years, and remained constant thereafter. With long-term follow-up, extensively porous-coated, cylindrical stems used for femoral revision continue to demonstrate excellent survivorship.

A hydroxyapatite graft substitute reduces subsidence in a femoral impaction grafting model

Synthetic bone graft substitutes have been developed for impaction grafting revision hip surgery in response to concerns about the availability and potential infection risk of allograft. We performed an in vitro experiment to determine whether a synthetic porous hydroxyapatite material might improve resistance to cumulative subsidence and cyclic (elastic) movement on loading. We impacted different ratios of hydroxyapatite and allograft (0%, 50%, 70%, and 90% hydroxyapatite) into composite femoral models (eight per group) and implanted tapered, polished stems with cement. Models were loaded for 18,000 cycles on a servohydraulic materials testing machine. Migration of the femoral prostheses and the distal cement was determined using radiostereometric analysis, and cyclic movement was measured mechanically by the testing machine. Hydroxyapatite decreased overall subsidence and subsidence at the prosthesis-cement interface, but there was no difference at the cement-femur interface. This decrease may have occurred because the hydroxyapatite-containing graft was more rigid, or because it resulted in a thicker cement mantle. Cyclic prosthesis movement also was lower with hydroxyapatite. While the biologic response to porous hydroxyapatite remains to be determined, its mechanical properties appear promising.

Irradiation has no effect on the incorporation of impacted morselized bone: a bone chamber study in goats

BACKGROUND

Gamma irradiation has been widely used for sterilization of bone allografts. However, gamma irradiation alters proteins. This is favorable when it reduces immunogenicity, but is undesirable when osteoinductive proteins are damaged. Although the effect of gamma irradiation on BMPs has been studied, the effect of irradiation on the process of incorporation of morselized bone chips remains unclear. We studied the effects of sterilization by gamma irradiation on the incorporation of impacted morselized allografts.

METHODS

Bone chambers with impacted allografts, rinsed impacted allografts, allografts that were rinsed and subsequently irradiated, and an empty control were implanted in proximal medial tibiae of goats. Incorporation was evaluated using histology and histomorphometry.

RESULTS

Histology revealed evidence of bone graft incorporation, which proceeded in a similar way in unprocessed, rinsed, and both rinsed and irradiated bone grafts. After 12 weeks, no difference in bone and tissue ingrowth was found between the unprocessed, the rinsed, and the rinsed and subsequently irradiated allografts. The amount of unresorbed graft remnant was highest in the unprocessed bone grafts.

INTERPRETATION

We conclude that sterilization with gamma irradiation does not influence the incorporation of impacted rinsed bone allografts.

Graft incorporation after acetabular and femoral impaction grafting with washed irradiated allograft and autologous marrow

Rates of around 40% incorporation have been described when chips of irradiated cancellous allograft with retained fat were impacted with the Exeter technique. We report the results of acetabular and femoral impaction bone grafting during revision hip arthroplasty using washed irradiated allograft with autologous marrow. Eighty-five consecutive patients underwent acetabular and or femoral revision arthroplasty. Evidence of graft cortication and trabeculation was recorded on successive postoperative radiographs, over a mean period of 44 months. Ninety-six percent (49/51) and 90% (53/59) of patients showed incorporation in acetabular and femoral grafts, respectively. This was usually apparent by 6 months postoperatively. We conclude that the addition of autologous marrow to irradiated bone allograft during impaction grafting is a cheap and highly effective way of achieving graft incorporation.

In vitro monitoring of hoop strains during impaction grafting of the femur

A test was designed to monitor hoop strains around the proximal femur during impaction grafting. Four electrical resistance strain gauges were attached to Sawbone femurs just below the level of the lesser trochanter. Experimentation with these femoral models included the use of a device called an "impactometer", which delivered controllable impaction energies. Test material used was ovine morsellised bone graft prepared from sheep femoral condyles. Instruments used were "X-change" revision instruments from the Exeter hip system. Maximum strains occurred at the medial and lateral cortices and there were lesser strains on anterior and posterior cortices. These findings raise questions about the quality of impaction anterior and posterior to the femoral stem. At the medial and lateral gauges significant differences in levels of strain were recorded at the three different levels of impaction. An individual hoop strain was found to have three components: peak, rapid drop and slow drop. The strain level did not drop back to the starting point at the end of the drop phase but dropped only halfway back to the starting level. This resulted in a rise in strain levels in a stepladder pattern. Strains continued to rise significantly when the impaction process was continued beyond the endpoint of impaction. Early recognition of the endpoint of impaction can save the weak femoral bone from unnecessary high levels of hoop strain.

Incidence of infection with the use of non-irradiated morcellised allograft bone washed at the time of revision arthroplasty of the hip

Implantation of allograft bone is an integral part of revision surgery of the hip. One major concern with its use is the risk of transmission of infective agents. There are a number of methods of processing allograft bone in order to reduce this risk. One method requires washing the tissue using pulsed irrigation immediately before implantation. We report the incidence of deep bacterial infection in 138 patients (144 revision hip arthroplasties) who had undergone implantation of allograft bone. The bone used was fresh-frozen, non-irradiated and pulse-washed with normal saline before implantation. The deep infection rate at a minimum follow-up of one year was 0.7%. This method of processing appears to be associated with a very low risk of allograft-related bacterial infection.

A laboratory simulation for morselized bone graft fusion: apparent modulus under operatively based femoral impaction kinetics

The purpose of this study was to determine the apparent modulus changes accompanying a novel procedure for simulating in situ fusion of morselized cancellous bone femoral impaction grafts. An experienced surgeon's habitual intra-operative impaction grafting protocol was first quantified in human cadaver femurs, using a customized impulse force hammer. A corresponding standardized impaction procedure was then defined, and was used to prepare impaction grafts in axisymmetric metallic fixturing designed to replicate the nominal geometry of femoral canal confinement. Impaction graft fusion was simulated by mixing morselized cancellous bone with an amine-based epoxy adhesive before the impaction, then allowing the mixture to fuse after the impaction (J. Biomech. 34 (2001) 811). Force/deflection behavior of the unfused and fused impaction grafts was measured for both the (tapered) proximal and (untapered) distal portions of the grafts. Apparent modulus was then calculated from force/deflection stiffness. The impaction graft fusion simulation increased apparent modulus by an order of magnitude over the unfused state, for mixture parameters appropriate to have the fused graft apparent modulus be comparable to the compressive modulus of intact femoral cancellous bone.

No effect of platelet-rich plasma with frozen or processed bone allograft around noncemented implants

We compared processed morselized bone allograft with fresh-frozen bone graft around noncemented titanium implants. Also, the influence of platelet-rich plasma (PRP) in combination with bone allograft was evaluated. Analysis was based on implant fixation and histomorphometry. PRP was prepared by isolating the buffy coat from autologous blood samples. Bone allograft was used fresh-frozen or processed by defatting, freeze drying, and irradiation. Cylindrical hydroxyapatite-coated titanium implants were inserted bilaterally in the femoral condyles of eight dogs. Each implant was surrounded by a 2.5-mm concentric gap, which was filled randomly according to the four treatment groups--group 1: fresh-frozen bone allograft; group 2: processed bone allograft; group 3: fresh-frozen bone allograft + PRP; group 4: processed bone allograft + PRP. Histological and mechanical evaluation demonstrated no influence of bone allograft processing. Even though the level of platelet in PRP was 7.7 times that found in whole blood, we found no improvement of bone formation or implant fixation by adding PRP.