Incorporation of vancomycin-supplemented bone allograftsRadiographical, histopathological and immunohistochemical study in pigs

Is two-stage revision surgery for infected hip arthroplasty worth the suffering, resources and results compared to one-stage?

PURPOSE

Periprosthetic joint infection (PJI) is the most serious complication of total hip arthroplasty. The treatment is usually revision in either 1 or 2 stages. This study analyses revision with impaction bone grafting for periprosthetic joint infection of the hip and compares 1- and 2-stage strategies.

PATIENTS AND METHODS

We reviewed 55 consecutive cases (54 patients) of revision arthroplasty for PJI carried out at our hospital between 2002 and 2016. Of these, 46 were 2-stage procedures. 21 had vancomycin mixed in with the bone graft, and all had gentamycin-containing bone cement. The total perioperative blood loss, duration of operation, and length of hospital stay were recorded. Clinical and radiological results were analysed for 48 hips at 2-16 years follow-up.

RESULTS

No PJI remained at follow-up. 3 patients (6%) had undergone revision for all causes. 1 had radiological signs of mechanical loosening but was not revised. 2-stage procedures had a significantly longer operating time (409 vs. 238 min) and hospital stay (34 vs. 13 days), greater blood loss (2764 vs. 1638 ml), and lower mean functional hip score (15.9 vs. 17.5) at follow-up than the one-stage procedures.

INTERPRETATION

Revision total hip arthroplasty for PJI with vancomycin-loaded impaction bone grafting is a safe method that achieves both the restoration of bone stock and resolution of the infection. This single-stage procedure could therefore be the new gold standard for treatment of non-complicated PJI in the hip.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 μm; loading 47 mg_VaH/g_PLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm³ w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Current Insights in the Application of Bone Grafts for Local Antibiotic Delivery in Bone Reconstruction Surgery

Introduction: Bone implant related infection is still one of the biggest challenges in bone and joint surgery. Antibiotic impregnated bone grafts seem to be promising in both treatment and prevention of these infections. However, great variance in methodology predominates this field of research. This paper gives an overview of the published literature.

Methods: The PRISMA-flowchart was used as protocol for article selection. Medline was searched and articles were selected in accordance with predetermined exclusion criteria.

Results: Forty-eight articles were included in the synthesis. Topics including bone graft type, manipulations of the graft, elution profile, bacterial inhibition, osteotoxicity, incorporation, special impregnation methods, clinical use and storage were investigated.

Therapeutically, high initial levels seem appropriate for biofilm eradication. A single stage procedure in the treatment of bone implant related infection seems feasible. Prophylactically, the literature indicates a reduction of postoperative infections when using antibiotic impregnated bone grafts.

Conclusion: Bone grafts are a suitable carrier for local antibiotic application both therapeutically and prophylactically.

[Use of antibiotics in bones : Prophylaxis and current treatment standards]

BACKGROUND

Treatment of bone infection is difficult due the systemic administration of antibiotics, which means that only low concentrations reach the inflamed bone tissue. Loss of bone stock is common in osteomyelitis and device associated infection. Local antibiotics are administered in several ways for prophylactic purposes and also for treatment of bone infection. We intend to show the options and limitations of clinical use of antibiotic-loaded bone grafts.

SUITABILITY

Bone grafts are a suitable carrier system for antibiotics. Bone grafts may be loaded with a variety of antimicrobial agents so that individual therapies may be carried out. Critical systemic side effects are unlikely even though extreme high drug concentrations are obtained locally, if the thresholds for loading with antibiotics are respected. Thus, antibiotic-loaded bone grafts are appropriate for prophylaxis and therapy as well. If processing is done in the operating theatre compliance to the legal rules must be respected.

RULES

Due to a lack of standardised procedures for loading, application and performance of the application of antibiotic-loaded bone grafts medical societies are being asked to initiate consensus meetings in order to issue recommendations or guidelines with respect to antibiotic-loaded bone grafts to establish reliable rules for surgeons using these devices.

Hydroxyapatite microporous bioceramics as vancomycin reservoir: Antibacterial efficiency and biocompatibility investigation

AbstarctInfections after bone reconstructive surgery are a real therapeutic and economic issue for the modern health care system. As the pathogen (most often Staphylococcus aureus) is able to develop a biofilm inside the bone, local delivery of antibiotics is of interest since high drug concentrations would be delivered directly at the target place. In this context, this study evaluated a porous hydroxyapatite implant as biocompatible bone substitute and vancomycin-delivery system to prevent post-operative infections. A simple method of impregnation with optimised conditions insured a high antibiotic loading (up to 2.3 ± 0.3 mg/m²), with a complete in vitro release obtained within 1-5 days. Additionally, the bacteriostatic and bactericidal effects of vancomycin were retained after loading on hydroxyapatite, as demonstrated after challenge with a Staphylococcus aureus strain. Regarding the biocompatibility, a wound healing assay of pre-osteoblastic MC3T3-E1 cells exposed to various concentrations of vancomycin revealed a dose-dependent reduction in cell migration for antibiotic concentrations higher than 1 mg/mL. Meanwhile, cells were able to proliferate normally on vancomycin-loaded scaffolds, although cell initial adhesion was seriously impaired for scaffolds loaded with 2.3 mg/m² Loaded scaffolds could be stored up to three months at room temperature without any degradation of the antibiotic. Together, these results demonstrate the efficacy of these hydroxyapatite bone substitutes for local delivery of vancomycin in the context of bone infection.

Polymer-controlled release of tobramycin from bone graft void filler

Despite clinical, material, and pharmaceutical advances, infection remains a major obstacle in total joint revision surgery. Successful solutions must extend beyond bulk biomaterial and device modifications, integrating locally delivered pharmaceuticals and physiological cues at the implant site, or within large bone defects with prominent avascular spaces. One approach involves coating clinically familiar allograft bone with an antibiotic-releasing rate-controlling polymer membrane for use as a matrix for local drug release in bone. The kinetics of drug release from this system can be tailored via alterations in the substrate or the polymeric coating. Drug-loaded polycaprolactone coating releases bioactive tobramycin from both cadaveric-sourced cancellous allograft fragments and synthetic hybrid coralline ceramic bone graft fragments with similar kinetics over a clinically relevant 6-week timeframe. However, micron-sized allograft particulate provides extended bioactive tobramycin release. Addition of porogen polyethylene glycol to the polymer coating formulation changes tobramycin release kinetics without significant impact on released antibiotic bioactivity. Incorporation of oil-microencapsulated tobramycin into the polymer coating did not significantly modify tobramycin release kinetics. In addition to releasing inhibitory concentrations of tobramycin, antibiotic-loaded allograft bone provides recognized beneficial osteoconductive potential, attractive for decreasing orthopedic surgical infections with improved filling of dead space and new bone formation.

Calcium carbonate powder containing gentamicin for mixing with bone grafts

Bone grafts are used for reconstructing bone defects caused by implant-associated complications, trauma, and tumors. Surgery with bone allografts is complex and time consuming; therefore, it is prone to a higher infection rate (2.0%-2.5%). In the case of site infection, systemically administered antibiotics cannot reach the infected bone graft. This study evaluated the use of resorbable bone graft substitute powder (HERAFILL; Heraeus Medical GmbH, Wehrheim, Germany) as a bone void-filling material as well as an antibiotic carrier for mixing with bone grafts. The antibiotic activity of the bone chips mixed with HERAFILL powder was measured by drug release tests and bacterial susceptibility with Bacillus subtilis, Staphylococcus epidermidis, and Staphylococcus aureus. HERAFILL powder was added to the bone chips (bone chips/HERAFILL; w/w = 1:1), mixed with a spatula, and vortexed for 1 minute. Gentamicin base release was evaluated in phosphate-buffered saline for up to 7 days using B subtilis bioassay. Antimicrobial efficacy was tested with S aureus and S epidermidis. The average amount of gentamicin base released from bone chips mixed with HERAFILL at 0 to 12 hours was 99.66 mg/mL. On day 7, the gentamicin base released 0.42 mg/mL. The elution released from bone chips mixed with HERAFILL promoted the formation of a zone of inhibition on S epidermidis and S aureus plates. This study confirmed the capacity of bone grafts to act as antibiotic carriers once mixed with HERAFILL powder. Bone chips mixed with HERAFILL showed efficacy against S aureus and S epidermidis.

Effect of freezing on the release rate of gentamicin palmitate and gentamicin sulfate from bone tissue

In this study we evaluated gentamicin palmitate salt and gentamicin sulfate salt mixed with bone chips after storage at -80°C. Different concentration rates of gentamicin sulfate and gentamicin palmitate were mixed with human bone chips and stored for 1-6 months at -80°C. Nonstored samples were used as control. The release of the antibiotics from the bone was carried out in phosphate-buffered saline. Antibiotic concentrations in the elutions were determined with microbiological agar diffusion assay using Bacillus subtilis. Susceptibility tests were carried out using Staphylococci strains. The rate of gentamicin base (GB) released from bone was similar for all gentamicin salts and all storage conditions. The elutions released were efficient on reducing S. aureus and S. epidermidis CFU during all storage time. In resume, the capacity of bone grafts to act as gentamicin carriers has been confirmed in this study. GS + GP showed equivalent efficacy against S. aureus and S. epidermidis compared with GS pure. The lower delivery rate of GS + GP, related to its affinity with fat tissue can be an advantage for longer release times, increasing the local protection against infections. Storage at -80°C does not interfere on the gentamicin salts activity used.

Gentamicin palmitate as a new antibiotic formulation for mixing with bone tissue and local release

During surgery with bone grafting, the impaction of bone tissue creates an avascular area where local circulation is disrupted. If infections arise, they may prevent systemically administered antibiotics from reaching the infected bone. In this study we evaluated gentamicin palmitate (GP) mixed with gentamicin sulfate (GS) as a coating for bone chips (BCh). The efficacy of the coated BCh was measured by gentamicin base release tests using B. subtilis, S. epidermidis and S. aureus. Gentamicin base release was evaluated in phosphate-buffered saline for up to 7 days using B. subtilis bioassay. Antimicrobial efficacy was tested with S. aureus and S. epidermidis. A significant difference on the release of gentamicin base between GS and GS + GP was observed. S. epidermidis are significantly more susceptible to GS + GP and GS than S. aureus. BCh can act as gentamicin carriers and showed efficacy against S. aureus and S. epidermidis.

Bone grafting and two-stage revision total hip arthroplasty

Periprosthetic deep infection in combination with substantial bone loss is one of the most challenging situations in revision hip surgery. We believe the effective management of these patients requires infection control as well as bone reconstruction. A review of our previously published studies on antibiotic loaded bone allografts is presented in this paper. These investigations provided us with information on the use of bone allografts in combination with antibiotics in cases of previous infection. Our protocol is based on removal of implants, meticulous debridement, parenteral antibiotic therapy and a second-stage reconstruction with vancomycin-supplemented bone allografts to treat an infected hip arthroplasty. We observed that vancomycin does not affect bone allograft incorporation at concentrations that are 300 times higher than the minimum inhibitory concentration for Staphylococcus aureus and Staphylococcus epidermidis. We also obtained adequate pharmacokinetics using these composites, with high local levels without renal impairment. This method has the capacity of acetabular and femoral bone stock restoration, with sound fixation and without increasing the rate of reinfection.

Effect of storage temperature on gentamicin release from antibiotic-coated bone chips

Freezing is the most common method for storing bones until use in skeletal reconstruction. However, the effect of freezing on antibiotic delivery from antibiotic-coated bone has not been evaluated. In this study, we compared antibiotic delivery in vitro from gentamicin-coated human bone stored at different temperatures. Bone chips obtained from human femur heads were chemically cleaned and mixed with gentamicin sulfate. Samples were stored for 4 months at -20 °C, 4 months at -80 °C, or evaluated immediately without freezing. Antibiotic release from the bone chips was measured using Bacillus subtilis as an indicator strain. Zones of inhibition and rates of gentamicin release were similar in all three groups. Storage at -20 and -80 °C for bone allografts has no effect on gentamicin release from chemically cleaned bone chips.

Antibiotic-impregnated bone grafts in orthopaedic and trauma surgery: a systematic review of the literature

There exist several options for local antibiotic therapy in orthopaedic and trauma surgery. Over the past years, the use of antibiotic-impregnated bone grafts (AIBGs) has become a popular procedure in the treatment of bone and joint infections. A major advantage of AIBGs involves the possibility of impregnation of various antibiotics depending on the sensitivity profile of the causative organism, whereas an additional surgery with removal of the antibiotic carrier is not necessary, as in the use of antibiotic-loaded bone cement. However, generalized conclusions cannot be clearly drawn from the existing literature due to differences of bone used, impregnation method, antibiotics, their doses, laboratory circumstances, or clinical indications. The present work reviews the literature regarding this topic and sheds some light onto the choice of bone and antibiotics, manufacturing details, and clinical experience.

Bone grafts as vancomycin carriers in local therapy of resistant infections

The level of an antibiotic capable of inhibiting the etiological agent at the site of infection is an essential prerequisite for successful antibiotic therapy. In some cases, locally applied antibiotics may compensate for limitations of systemic administration and shorten systemic therapy. We aimed at verifying to what extent vancomycin (Van) bound to ground bone grafts is usable in the treatment of serious infections. The levels of released Van significantly exceeded the Van minimum inhibitory concentration, which can suppress Van-sensitive staphylococci and Van intermediate Staphylococcus aureus, for the whole period of a 16-day measurement. Our results indicate that bone grafts can be used as Van carriers in therapy of osteomyelitis caused by Van-sensitive Staphylococcus strains.

Impregnation of bone chips with alendronate and cefazolin, combined with demineralized bone matrix: a bone chamber study in goats

Background

Bone grafts from bone banks might be mixed with bisphosphonates to inhibit the osteoclastic response. This inhibition prevents the osteoclasts to resorb the allograft bone before new bone has been formed by the osteoblasts, which might prevent instability. Since bisphosphonates may not only inhibit osteoclasts, but also osteoblasts and thus bone formation, we studied different bisphosphonate concentrations combined with allograft bone. We investigated whether locally applied alendronate has an optimum dose with respect to bone resorption and formation. Further, we questioned whether the addition of demineralized bone matrix (DBM), would stimulate bone formation. Finally, we studied the effect of high levels of antibiotics on bone allograft healing, since mixing allograft bone with antibiotics might reduce the infection risk.

Methods

25 goats received eight bone conduction chambers in the cortical bone of the proximal medial tibia. Five concentrations of alendronate (0, 0.5 mg/mL, 1 mg/mL, 2 mg/mL, and 10 mg/mL) were tested in combination with allograft bone and supplemented with cefazolin (200 μg/mL). Allograft not supplemented with alendronate and cefazolin served as control. In addition, allograft mixed with demineralized bone matrix, with and without alendronate, was tested. After 12 weeks, graft bone area and new bone area were determined with manual point counting.

Results

Graft resorption decreased significantly (p < 0.001) with increasing alendronate concentration. The area of new bone in the 1 mg/mL alendronate group was significantly (p = 0.002) higher when compared to the 10 mg/mL group. No differences could be observed between the group without alendronate, but with demineralized bone, and the control groups.

Conclusions

A dose-response relationship for local application of alendronate has been shown in this study. Most new bone was present at 1 mg/mL alendronate. Local application of cefazolin had no effect on bone remodelling.

Incidence of deep infection in aseptic revision THA using vancomycin-impregnated impacted bone allograft

The addition of antibiotic to cement is a frequent practice in aseptic revision hip surgery There is concern about adding vancomycin to cement due to potential effects on mechanical properties and prolonged elution of subtherapeutic levels antibiotic. Bone allografts can store and provide high levels of vancomycin to surrounding tissues. We analyzed the incidence of infection after one-stage aseptic revision hip reconstruction utilizing acetabular and/or femoral vancomycin-impregnated impacted bone allograft and a THA fixed with cement containing no antibiotic. We hypothesized that the infection rate may be similar to that reported in the literature following traditional impaction grafting using antibiotic loaded cement. Seventy five consecutive patients (80 hips) with a preoperative Merle D'Aubigné and Postel functional score averaging 4.8 points were followed up for a mean of 36 months (range 24 - 59 months). The incidence of infection was 1.25% (CI 95%=96.26-100%). A deep infection (thought to be haematognous in origin) occurred in 1 patient 2 years after the index surgery. The average postoperative Merle D´Aubigne score was 16.2 points. The last radiographic evaluation demonstrated a less than 5 mm acetabular migration and a less than 5 mm femoral subsidence in all cases. Vancomycin-supplemented allografts restored bone stock and provided sound fixation with a low incidence of infection. This incidence of deep sepsis is similar to that reported with antibiotic-loaded PMMA but without the reported mechanical and pharmacological disadvantages.

Recent advances in the use of serological bone formation markers to monitor callus development and fracture healing

The failure of an osseous fracture to heal, or the development of a nonunion, is common; however, current diagnostic measures lack the capability of early and reliable detection of such events. Analyses of radiographic imaging and clinical examination, in combination, remain the gold standard for diagnosis; however, these methods are not reliable for early detection. Delayed diagnosis of a nonunion is costly from both the patient and treatment standpoints. In response, repeated efforts have been made to identify bone metabolic markers as diagnostic or prognostic tools for monitoring bone healing. Thus far, the evidence regarding a correlation between the kinetics of most bone metabolic markers and nonunion is very limited. With the aim of classifying the role of biological pathways of bone metabolism and of understanding bone conditions in the development of osteoporosis, advances have been made in our knowledge of the molecular basis of bone remodeling, fracture healing, and its failure. Procollagen type I amino-terminal propeptide has been shown to be a reliable bone formation marker in osteoporosis therapy and its kinetics during fracture healing has been recently described. In this article, we suggest that procollagen type I amino-terminal propeptide presents a good opportunity for early detection of nonunion. We also review the role and potential of serum PINP, as well as other markers, as indications of fracture healing.

Impregnation of bone chips with antibiotics and storage of antibiotics at different temperatures: an in vitro study

Background

Allograft bone used in joint replacement surgery can additionally serve as a carrier for antibiotics and serve as a prophylaxis against infections. However, in vitro dose-response curves for bone chips impregnated with different kinds of antibiotics are not available. In addition, while it would be desirable to add the antibiotics to allograft bone chips before these are stored in a bone bank, the effects of different storage temperatures on antibiotics are unknown.

Methods

Five different antibiotics (cefazolin, clindamycin, linezolid, oxacillin, vancomycin) were stored, both as pills and as solutions, at -80°C, -20°C, 4°C, 20°C and 37°C; in addition, bone chips impregnated with cefazolin and vancomycin were stored at -80°C and -20°C. After 1 month, 6 months and 1 year, the activity of the antibiotics against Staphylococcus epidermidis was measured using an inoculated agar. The diameter of the S. epidermidis-free zone was taken as a measure of antibiotic activity.

In a separate experiment, in vitro dose-response curves were established for bone chips impregnated with cefazolin and vancomycin solutions at five different concentrations.

Finally, the maximum absorbed amounts of cefazolin and vancomycin were established by impregnating 1 g of bone chips with 5 ml of antibiotic solution.

Results

A decrease of the S. epidermidis-free zone was seen with oxacillin and cefazolin solutions stored at 37°C for 1 month, with vancomycin stored at 37°C for 6 months and with cefazolin and oxacillin solutions stored at 20°C for 6 months. The activity of the other antibiotic solutions, pills and impregnated bone chips was not affected by storage. The in vitro dose-response curves show that the free-zone diameter increases logarithmically with antibiotic concentration. The absorbed antibiotic amount of one gram bone chips was determined.

Conclusions

Storage of antibiotics in frozen form or storage of antibiotic pills at temperatures up to 37°C for 12 months does not affect their activity. However, storage of antibiotic solutions at temperatures above 20°C does affect the activity of some of the antibiotics investigated. The in vitro dose-response curve can be used to determine the optimal concentration(s) for local application. It provides the opportunity to determine the antibiotic content of bone chips, and thus the amount of antibiotics available locally after application.

Antibiotic-loaded allograft decreases the rate of acute deep wound infection after spinal fusion in cerebral palsy

STUDY DESIGN

A retrospective matched cohort study with control group.

OBJECTIVE

To compare the infection rate after posterior spinal fusion with unit rod instrumentation with or without gentamicin-impregnated allograft bone in children with cerebral palsy (CP).

SUMMARY OF BACKGROUND DATA

Previous studies evaluating wound infection rates after spinal fusion surgery in children with CP report an 8.7% to 10% wound infection rate. The concept of using antibiotic-loaded bone graft (AbBGF) to provide local antibiotics has been explored in high risk patients, such as those with osteomyelitis or infected joint arthroplasty. There have been no reports of using AbBGF prophylactically in spine surgery.

METHODS

After IRB approval, the medical records of 220 children with CP who underwent spinal fusion with unit rod instrumentation for a primary spinal deformity between January 2000 through December 2006 at a single institution were retrospectively reviewed. We evaluated the incidence of postoperative wound infection in patients with AbBGF and those without bone graft (BGF).

RESULTS

One hundred fifty-four patients received AbBGF during spinal fusion surgery and 6 patients (3.9%) developed a deep wound infection. Ten (15.2%) of the 66 patients without AbBGF developed a deep wound infection. The difference between groups was statistically different (P = 0.003). The mean age at surgery, preoperative Cobb angle, correction rate, operative time, and estimated blood loss were not statistically different between the 2 groups (P > 0.05). The length of hospital stay was decreased in the AbBGF group (P < 0.05).

CONCLUSION

The incidence of deep wound infection after spinal fusion in 220 children with CP scoliosis decreased from 15% to 4% with the use of prophylactic antibiotics in the corticocancellous allograft bone.

Viability of impacted bone allografts under metal mesh at the calcar in revision surgery of the hip

Metal meshes are used in revision surgery of the hip to contain impacted bone grafts in cases with cortical or calcar defects in order to provide rotational stability to the stem. However, the viability of bone allografts under these metal meshes has been uncertain. We describe the histological appearances of biopsies obtained from impacted bone allografts to the calcar contained by a metal mesh in two femoral reconstructions which needed further surgery at 24 and 33 months after the revision procedure. A line of osteoid and viable new bone was observed on the surface of necrotic trabeculae. Active bone marrow between these trabeculae showed necrotic areas in some medullary spaces with reparative fibrous tissue and isolated reactive lymphocytes. This is interpreted as reparative changes after revascularisation of the cancellous allografts. These pathological findings are similar to those reported in allografts contained by cortical host bone and support the hypothesis that incorporation of morcellised bone under metal meshes is not affected by these devices.

Vancomycin-supplemented cancellous bone allografts in hip revision surgery

We explored the role of vancomycin-supplemented cancellous bone allografts in hip revision surgery. We evaluated the incorporation of these allografts in 18 pigs' radiographs, histology, and immunohistochemistry. High-quality radiographs, histologic examination, and immunologic expression of metalloproteinase-13 and transforming growth factor-beta 2 indicated vancomycin did not considerably affect bone graft incorporation. Elution, bioactivity, and nephrotoxicity were subsequently tested in 20 patients who underwent hip reconstruction with this method. Local active bactericidal levels of vancomycin reached 1400.5 microg/mL (average 5-point level, 367.19 microg/mL). Vancomycin was present in urine until day 15 without any sign of nephrotoxicity. Clinical analysis was performed in 30 patients whose hips underwent reconstruction with vancomycin-supplemented cancellous bone allograft. At a minimum 2-year followup, infection control was attained in 29 of 30 patients (reinfection rate, 3.3%; 95% confidence interval, 0.08-17%) without evidence of graft resorption. Histologic observations performed in two patients whose hips were reconstructed with this technique were similar to the ones reported in nonsupplemented bone allografts. Our findings encourage the continued use of vancomycin-supplemented bone allografts in reconstructive orthopaedic surgery.

Acetabular reconstruction with impacted bone allografts and cemented acetabular components

We reviewed the clinical and radiological results of 131 patients who underwent acetabular revision for aseptic loosening with impacted bone allograft and a cemented acetabular component. The mean follow-up was 51.7 months (24 to 156).

The mean post-operative Merle D’Aubigné and Postel scores were 5.7 points (4 to 6) for pain, 5.2 (3 to 6) for gait and 4.5 (2 to 6) for mobility. Radiological evaluation revealed migration greater than 5 mm in four acetabular components. Radiological failure matched clinical failure. Asymptomatic radiolucent lines were observed in 31 of 426 areas assessed (7%). Further revision was required in six patients (4.5%), this was due to infection in three and mechanical failure in three. The survival rate for the reconstruction was 95.8% (95% confidence interval 92.3 to 99.1) overall, and 98%, excluding revision due to sepsis.

Our study, from an independent centre, has reproduced the results of the originators of the method.

The effect of demineralized bone matrix-calcium sulfate with vancomycin on calcaneal fracture healing and infection rates: a prospective study

BACKGROUND

Displaced intra-articular calcaneal fractures may have a central cancellous bone defect area. We hypothesized that human demineralized bone matrix (DBM) calcium sulfate (CaSO(4)) might act as a reasonable alternative to autograft in calcaneal fractures. When combined with antibiotic powder, this bone graft substitute also may act as a local antibiotic delivery device. This is the first clinical study evaluating bone healing and complications associated with DBM-calcium sulfate bone graft substitute in the treatment of displaced intra-articular calcaneal fractures with a central cancellous bone defect.

METHODS

Over a 29-month period, 33 displaced intra-articular calcaneal fractures with central cancellous defects were treated with open reduction and internal fixation (ORIF) and grafting with vancomycin/DBM-calcium sulfate bone graft substitute. Eleven fractures without bone defects were treated with ORIF only. Patient demographics, medical history, and CT fracture classification were recorded. Postoperatively, fractures were monitored every 2 weeks for healing and complications.

RESULTS

The mean time to union was 8.2 weeks in the grafted, while the control group mean time to union was 10.4 weeks (p = 0.0117). Wound problems occurred in five (15%) of the 33 patients with grafting, all in type III fractures with severe soft-tissue swelling, and included two minor wound healing delays, and three serious wound problems. At a mean followup time of 22.4 months, no DBM-calcium sulfate grafted calcaneus demonstrated evidence of osteomyelitis.

CONCLUSIONS

This is the first study examining human DBM-calcium sulfate bone graft substitute to treat displaced intra-articular calcaneal fractures. Based on these initial data, human DBM-calcium sulfate acted as an acceptable and safe autograft alternative in displaced intra-articular calcaneal fractures with moderate (5 cc to 10 cc) central cancellous bone defects.

Histology of vancomycin-supplemented impacted bone allografts in revision total hip arthroplasty

Vancomycin-supplemented allografts provide biological restoration of bone stock and sound fixation with a low incidence of re-infection. Experimental incorporation of these grafts is similar to allografts without vancomycin. However, the underlying biology remains unknown.

We report the first histological observations of vancomycin-supplemented impacted bone allografts in two reconstructions performed 14 and 20 months after revision surgery because of a periprosthetic fracture.

Areas of active bone remodelling (creeping substitution), as well as calcified bone trabeculae and graft particles embedded in dense fibrous tissue, were observed with osteoid and fibroconnective tissue surrounding polymethylmethacrylate particles.

These pathological findings are similar to those reported in allografts without vancomycin and support the hypothesis that high levels of vancomycin do not affect the incorporation of bone graft.

Cortical allograft as a vehicle for antibiotic delivery

BACKGROUND

Infection can be a devastating complication after implantation of a cortical bone allograft. The allograft could act as a vehicle for local antibiotic prophylaxis.

MATERIAL AND METHODS

We studied the release of antibiotics in vitro from cortical bone allografts impregnated with antibiotics for different periods of time. We also studied whether cortical allografts impregnated with antibiotics could eradicate Staphylococcus aureus from an experimentally infected graft in vivo. In the in vitro study, pieces of cortical bone were impregnated with netilmicin, vancomycin, ciprofloxacin and rifampicin for 1 h, 10 h and 100 h. The antibiotics were eluted into phosphate-buffered saline (PBS) for 7 days, with daily transfer of the bone into fresh PBS. In the in vivo study, cortical allografts impregnated with antibiotics were placed in rats intramuscularly. 10 microL of an S. aureus suspension (0.6 x 10(5) CFU) was placed in the intramedullary cavity. After 15 days, the allografts were removed and examined for bacterial growth.

RESULTS

The amount of antibiotics released in vitro was influenced by the time used for antibiotic impregnation of the bone. Allografts impregnated with netilmicin, vancomycin and rifampicin effectively eradicated perioperative contamination with S. aureus in vivo.

INTERPRETATION

This study shows that a cortical bone allograft would be an effective vehicle for local antibiotic delivery.

Vancomycin-supplemented impacted bone allografts in infected hip arthroplasty. Two-stage revision results

Bone allografts can store and release high levels of vancomycin. We present our results of a two-stage treatment for infected hip arthroplasty with acetabular and femoral impaction grafting using vancomycin-loaded allografts. We treated 29 patients (30 hips) by removal of the implants, meticulous debridement, parenteral antibiotic therapy and second-stage reconstruction using vancomycin-supplemented impacted bone allografts and a standard, cemented Charnley femoral component. The mean follow-up was 32.4 months (24 to 60). Infection control was obtained in 29 cases (re-infection rate of 3.3%; 95% confidence interval 0.08 to 17) without evidence of progressive radiolucent lines, demarcation or graft resorption. One patient had a further infection ten months after revision caused by a different pathogen. Associated post-operative complications were one traumatic periprosthetic fracture at 14 months, a single dislocation in two hips and four displacements of the greater trochanter. Vancomycin-supplemented allografts restored bone stock and provided sound fixation with a low incidence of further infection.