Bone gentamicin concentration after intra-articular injection or regional intravenous perfusion in the horse

Local antibiotic delivery via intra-articular catheter infusion for the treatment of periprosthetic joint infection: a systematic review

INTRODUCTION

There is an increasing interest in the use of intra-articular (IA) antibiotic infusion as a stand-alone or adjuvant therapy to standard revision surgery for periprosthetic joint infection (PJI). The objective of this systematic review is to evaluate the evidence with respect to this up-and-coming treatment modality.

METHODS

A systematic review of studies published until April 2023 was conducted using PubMed, Embase, MEDLINE and Cochrane databases. Quality assessment was performed with the National Institute of Health quality assessment tool. Inclusion criteria were adult patients (≥ 18 years) with a mean follow-up of ≥ 11 months and a score ≥ 6 on the National Institute of Health quality assessment tool. Primary outcome was eradication of infection.

RESULTS

15 articles, encompassing 631 PJIs in 626 patients, were included in the final analysis, all level IV case series. The majority was treated with single-stage revision with adjuvant IA antibiotic infusion (79.1%). The remaining PJIs were treated with stand-alone IA antibiotic infusion (12.2%), DAIR (debridement, antibiotics and implant retention) with adjuvant IA antibiotic infusion (5.7%) or two-stage revision with adjuvant IA antibiotic infusion (3.0%). Mean duration of IA antibiotic infusion was 19 days (range 3-50). An overall failure rate of approximately 11% was found. In total 117 complications occurred, 71 were non-catheter-related and 46 were catheter-related. The most common catheter-related complications were premature loss of the catheter (18/46) and elevated blood urea nitrogen (BUN) and creatinine levels (12/46).

CONCLUSIONS

Due to the lack of comparative studies the (added) benefit of IA antibiotic infusion in the treatment of PJI remains uncertain. Based on the current evidence, we would advise against using it as a stand-alone treatment. A prospective randomized controlled trial using a well-described infusion protocol is needed to see if the potential benefits justify the increased costs and potential complications of this treatment modality.

Concentration of cephalothin in body fluids and tissue samples of Thoroughbred horses

Cephalothin (CET) concentrations in body fluids (plasma, synovial fluid, pleural fluid, peritoneal fluid, and aqueous humor) and tissue samples (bone, lung, jejunum, hoof, and subcutaneous tissue) were investigated to consider the treatment of infectious diseases in horses. CET 22 mg/kg body weight was intravenously administered to 12 horses. Samples were collected from four different horses at 1, 3, and 5 hr after administration. The CET concentration in body fluids other than aqueous humor was maintained above the MIC₉₀ values of Streptococcus zooepidemicus and Staphylococcus aureus until 5 hr, but it was not maintained above that of S. aureus in bone. CET (22 mg/kg twice a day) is effective for septic arthritis, pleuritis, and peritonitis caused by gram-positive bacteria but ineffective for osteomyelitis.

Effective Treatment of Single-Stage Revision Using Intra-Articular Antibiotic Infusion for Polymicrobial Periprosthetic Joint Infection

BACKGROUND

The treatment of polymicrobial periprosthetic joint infection (PJI) confronted distinct challenges. No reports have assessed the efficacy of local antibiotic delivery combined with 1-stage exchange in polymicrobial PJI.

METHODS

Between January 2013 and December 2018, we retrospectively analyzed the data of 126 patients, including 19 polymicrobial PJIs and 107 monomicrobial PJIs, who underwent single-stage revision using intra-articular antibiotic infusion. The risk factors, microbiology, infection control rate, and clinical outcomes were compared between the 2 groups.

RESULTS

Higher body mass index, presence of a sinus tract, and prior revisions were the risk factors for polymicrobial PJI. Isolation of Staphylococcus epidermidis, Streptococcus, Enterococcus, and Gram-negative pathogens was highly associated with polymicrobial PJI. Of the 19 polymicrobial PJIs, only 2 patients occurred infection recurrence, which is similar with the result of 6 of 107 patients in the monomicrobial PJI (P = .225). The Harris Hip Score of the polymicrobial group showed no difference from that of the monomicrobial group (78 vs 80; P = .181). Nevertheless, the polymicrobial group exhibited inferior Hospital for Special Surgery knee score relative to the monomicrobial group (77 vs 79; P = .017).

CONCLUSION

With rational and targeted use of antibiotics, single-stage revision can effectively control polymicrobial infections, and achieve favorable outcomes similar to that in monomicrobial patients. However, this regimen is still needed to be further confirmed, especially in the infections with different microbial species simultaneously. Additionally, obese patients with a sinus tract and those who had prior revisions had a greater risk of polymicrobial PJI.

Intra-articular administration of antibiotics in horses: Justifications, risks, reconsideration of use and outcomes

Antibiotics have been injected intra-articularly by equine veterinarians for decades, either prophylactically when other drugs are administered for osteoarthritis or therapeutically to treat septic arthritis. This route of administration has also more recently gained attention in human orthopaedic clinical practice, particularly as an alternative to systemic antibiotic administration to treat infections following prosthetic arthroplasty. While the rationale for injecting antibiotics intra-articularly has been largely focused on achieving high local drug concentrations, there has been relatively little focus on pharmacokinetic parameters of antibiotics administered by this route, or on the potential for local toxicity. The increasing incidence of antibiotic resistance in veterinary and human medicine prompts reconsideration of off-label antibiotic usage and evaluation of evidence-based dosing strategies. The purpose of this review was to summarise the current literature describing intra-articular antibiotic usage, including specific studies where pharmacokinetics, potential safety and toxicity have been evaluated. This review will advance practitioners' understanding of the use of intra-articularly administered antibiotics, including the overall pros and cons of the approach.

Orthopedic Infections-Clinical Applications of Intravenous Regional Limb Perfusion in the Field

For the equine veterinarian, orthopedic emergencies are a common occurrence in clinical practice, with traumatic wounds of the distal limb and penetrating injuries of the hoof being some of the most common medical conditions to affect horses. Intravenous regional limb perfusion is a technique widely used for the treatment of orthopedic infections in horses. The objectives of this review are to discuss some of the clinical applications for this treatment modality in the field and to review the technique for the practitioner.

Evaluation of Intra-Articular Amikacin Administration in an Equine Non-inflammatory Joint Model to Identify Effective Bactericidal Concentrations While Minimizing Cytotoxicity

Septic arthritis causes significant morbidity and mortality in veterinary and human clinical practice and is increasingly complicated by multidrug-resistant infections. Intra-articular (IA) antibiotic administration achieves high local drug concentrations but is considered off-label usage, and appropriate doses have not been defined. Using an equine joint model, we investigated the effects of amikacin injected at three different doses (500, 125, and 31.25 mg) on the immune and cartilage responses in tibiotarsal joints. Synovial fluid (SF) was sampled at multiple time points over 24 h, the cell counts determined, and amikacin concentrations measured by liquid chromatography-mass spectrometry. Cytokine concentrations and collagen degradation products in SF were measured by ELISA and multiplex immunoassays. The mean amikacin concentrations in SF were greater than or equal to the minimum inhibitory concentration (MIC) (0.004 mg/ml) for most common equine joint pathogens at all time points tested to 24 h for all three amikacin doses evaluated. The inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) increased significantly in SF in the highest amikacin dose group, despite the fact that increases in SF cell counts were not observed. Similarly, the biomarkers of cartilage type II collagen cleavage (C2C and C12C) were increased in SF following amikacin injection. Mechanistically, we further demonstrated using in vitro studies that chondrocytes and synoviocytes killed by exposure to amikacin underwent apoptotic cell death and were phagocytosed by macrophages in a non-inflammatory process resembling efferocytosis. Neutrophils and T cells were susceptible to amikacin cytotoxicity at clinically relevant doses, which may result in blunting of cellular inflammatory responses in SF and account for the lack of increase in total nucleated cell counts following amikacin injection. In summary, decisions on whether to inject cytotoxic antibiotics such as aminoglycosides intra-articularly and what doses to use should take into account the potential harm that antibiotics may cause and consider lower doses than those previously reported in equine practice.

Susceptibility of canine chondrocytes and synoviocytes to antibiotic cytotoxicity in vitro

OBJECTIVE

To evaluate relative cytotoxicity of antibiotics to normal canine joint tissues in vitro.

STUDY DESIGN

Experimental in vitro study.

SAMPLE POPULATION

Chondrocytes and synoviocytes (three dogs); cartilage explants (three dogs); six dogs total.

METHODS

Chondrocytes and synoviocytes from normal femoropatellar joints of three dogs were plated on 24-well plates (50 000 cells/cm² , triplicate, 48 hours) and exposed to antibiotics (ampicillin sulbactam, vancomycin, cefazolin, ceftazidime, amikacin, enrofloxacin; 0.39-25 mg/mL, 24 hours). Viability was assessed by using trypan blue dye exclusion. Antibiotic concentrations at which 50% cell death occurred (half-maximal inhibitory concentration) were determined to rank antibiotics for relative cytotoxicity. Occurrence of caspase-3 expression after antibiotic exposure was assessed as an indication of apoptosis induction. Cartilage explants from three different dogs were minced and exposed to antibiotics (amikacin, ceftazidime, cefazolin, enrofloxacin; 5 mg/mL, 72 hours). Live/dead staining was performed, and fluorescence was visualized by using confocal microscopy. Percentage of live vs dead cells was quantitated.

RESULTS

Viability of chondrocytes and synoviocytes decreased with increasing antibiotic concentrations. Half-maximal inhibitory concentrations were determined for synoviocytes (vancomycin 13.77, ampicillin sulbactam 3.07, amikacin 2.26, ceftazidime 1.62, cefazolin 1.48, enrofloxacin 1.25 mg/mL) and chondrocytes (vancomycin 8.65, ampicillin sulbactam 8.63, ceftazidime 3.16, amikacin 2.74, cefazolin 1.67, enrofloxacin 0.78 mg/mL). Caspase-3 expression was upregulated, providing evidence that apoptotic pathways were active in cell death.

CONCLUSION

Half-maximal inhibitory concentration data provided evidence of lower toxicity of vancomycin and ampicillin sulbactam to joint tissues in vitro.

CLINICAL SIGNIFICANCE

These results provide evidence to justify future in vitro work with osteoarthritic joint tissues and in vivo clinical trials to evaluate safety and efficacy of intra-articular antibiotics to treat dogs with septic arthritis.

Cumulative antibiogram and multidrug-resistant organisms in a regional equine referral hospital

Prudent use of antimicrobials is paramount to slow the development of resistance and for successful treatment. The use of cumulative antibiograms will allow evidence-based antimicrobial selection with consideration of local resistance patterns. We generated a "first-isolate-per-patient" cumulative antibiogram for a regional equine referral hospital. Bacterial organisms cultured from horses between 2011 and 2018, sample origin, antimicrobial susceptibilities, and multidrug-resistant (MDR) status were tabulated. Of 1,176 samples, 50% were culture positive. Overall, 93 of 374 (25%) were MDR. Of the MDR isolates, 11 (12%) were susceptible to high-importance antimicrobials only (as defined by the Australian Strategic and Technical Advisory Group on antimicrobial resistance). β-hemolytic streptococci were uniformly susceptible to penicillin (76 of 76); 17 of 20 (85%) non-β-hemolytic Streptococcus spp. were susceptible to penicillin. Despite veterinary-specific challenges in constructing an antibiogram, our study provides an exemplar of the clinical utility of regional-, farm-, or hospital-specific cumulative antibiograms for evidence-based empirical antimicrobial selection by veterinarians prior to susceptibility result availability.

Use of in vitro assays to identify antibiotics that are cytotoxic to normal equine chondrocytes and synovial cells

BACKGROUND

Intra-articular (IA) antibiotic usage is prevalent in equine practice. However, recent emergence of antimicrobial resistance prompts re-evaluation of antibiotic selection, particularly when used prophylactically. Furthermore, many commonly used antibiotics exert direct cytotoxicity to equine cells, and appropriate IA doses have not been defined.

OBJECTIVES

To screen antibiotics in vitro as an initial assessment of cytotoxicity against normal equine joint cells in monolayer culture and explant tissues.

STUDY DESIGN

In vitro experimental study.

METHODS

Chondrocytes and synovial cells were harvested from three horses and plated on 24-well plates (100 000 cells/wells in triplicate) for 48 hours prior to addition of antibiotics. Joint cells were exposed to antibiotics (n = 15) at various doses (25-0.39 mg/mL in complete DMEM media) for 24 hours and viability was assessed by trypan blue dye exclusion. The half maximal inhibitory concentration (IC50) was determined for each antibiotic. Cartilage explants were obtained from 3 horses, minced and exposed to antibiotics (n = 5) for 72 hours. Live/dead staining was performed, and fluorescence was visualised using Olympus IX83 spinning disk confocal microscope. Percentage of live vs dead cells was quantified.

RESULTS

Antibiotics from different antimicrobial classes expressed dose-dependent but variable cytotoxicity to equine joint cells in vitro. Aminoglycosides and doxycycline had the lowest IC50 (most toxic). Ampicillin sulbactam, imipenem, tobramycin, ceftiofur sodium and amoxicillin had IC50 > 25 mg/mL for at least one cell line, representing potentially less cytotoxic alternatives.

MAIN LIMITATIONS

Further studies are necessary to extrapolate these in vitro data results to the in vivo joint environment.

CONCLUSIONS

Targeted IA antibiotic therapy would involve selection of the safest antibiotics (highest IC50) with efficacy based on bacterial culture/sensitivity. Antimicrobial selection and evidence-based dosing may minimise damage to native articular cartilage and synovial cells and development of antimicrobial resistance when IA antibiotics are used in equine practice.

Bacterial osteomyelitis in veterinary orthopaedics: Pathophysiology, clinical presentation and advances in treatment across multiple species

Bacterial osteomyelitis in veterinary patients can be challenging to diagnose and treat, given limited therapeutic options and reported success rates. Osteomyelitis is frequently associated with surgical implant devices, including those required to optimise stability and healing of fractures. However, management of osteomyelitis sometimes necessitates the removal of these surgical implant devices in order to eradicate infection or limit implant-related osteolysis. The goal of this article is to provide a general and species-specific review of bacterial osteomyelitis in a selection of domestic veterinary species, including cats, dogs, horses, cattle and camelids, with a focus on classification, clinical presentation, aetiologic agents, and common therapeutic interventions reported in the literature. New treatment options emerging from research and human medicine will be also discussed, as they also apply to current or future care of veterinary patients with osteomyelitis.

Septic Arthritis, Physitis, and Osteomyelitis in Foals

Despite differences in etiology and diagnostics, the mainstay of therapy in the foal is similar to the adult: local lavage and/or debridement and local antimicrobial therapy. When musculoskeletal infection is concurrent with neonatal sepsis, the prognosis for survival is fair. When musculoskeletal infection is the primary problem, the prognosis is fair to good for survival of synovial, bony, and physeal infections with appropriate and aggressive local therapy. Recent literature may indicate that prognosis for survival and potential athleticism in foals that are treated expediently with local therapies and are without comorbidities may be more favorable than has been previously indicated.

Effects of regional limb perfusion volume on concentrations of amikacin sulfate in synovial and interstitial fluid samples from anesthetized horses

OBJECTIVE To evaluate the effect of volume of IV regional limb perfusion (IVRLP) on amikacin concentrations in synovial and interstitial fluid of horses. ANIMALS 8 healthy adult horses. PROCEDURES Each forelimb was randomly assigned to receive IVRLP with 4 mL of amikacin sulfate solution (250 mg/mL) plus 56 mL (total volume, 60 mL) or 6 mL (total volume, 10 mL) of lactated Ringer solution. Horses were anesthetized, and baseline synovial and interstitial fluid samples were collected. A tourniquet was placed, and the assigned treatment was administered via the lateral palmar digital vein. Venous blood pressure in the distal portion of the limb was recorded. Additional synovial fluid samples were collected 30 minutes (just before tourniquet removal) and 24 hours after IVRLP began; additional interstitial fluid samples were collected 6 and 24 hours after IVRLP began. RESULTS 30 minutes after IVRLP began, mean amikacin concentration in synovial fluid was significantly greater for the large-volume (459 μg/mL) versus small-volume (70 μg/mL) treatment. Six hours after IVRLP, mean concentration in interstitial fluid was greater for the large-volume (723 μg/mL) versus small-volume (21 μg/mL) treatment. Peak venous blood pressure after large-volume IVRLP was significantly higher than after small-volume IVRLP, with no difference between treatments in time required for pressure to return to baseline. CONCLUSIONS AND CLINICAL RELEVANCE Study findings suggested that large-volume IVRLP would deliver more amikacin to metacarpophalangeal joints of horses than would small-volume IVRLP, without a clinically relevant effect on local venous blood pressure, potentially increasing treatment efficacy.

Intra-articular infusion

Bactericidal levels of antibiotics are difficult to achieve in infected total joint arthroplasty when intravenous antibiotics or antibiotic-loaded cement spacers are used, but intra-articular (IA) delivery of antibiotics has been effective in several studies. This paper describes a protocol for IA delivery of antibiotics in infected knee arthroplasty, and summarises the results of a pharmacokinetic study and two clinical follow-up studies of especially difficult groups: methicillin-resistant Staphylococcus aureus and failed two-stage revision. In the pharmacokinetic study, the mean synovial vancomycin peak level was 9242 (3956 to 32 150; sd 7608 μg/mL) among the 11 patients studied. Serum trough level ranged from 4.2 to 25.2 μg/mL (mean, 12.3 μg/mL; average of 9.6% of the joint trough value), which exceeded minimal inhibitory concentration. The success rate exceeded 95% in the two clinical groups. IA delivery of antibiotics is shown to be safe and effective, and is now the first option for treatment of infected total joint arthroplasty in our institution.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):31–6.

Evaluation of intravenous regional perfusion with amphotericin B and dimethylsulfoxide to treat horses for pythiosis of a limb

BACKGROUND

Treatment for horses with pythiosis of a limb is challenging. This study aims to evaluate the effects of administering amphotericin B in a 10 % solution of dimethylsulfoxide by intravenous regional limb perfusion (IRLP) to treat horses for cutaneous pythiosis of a limb.

RESULTS

All 15 of the horses treated had complete resolutions of their lesion between 6 to 9 weeks after a single IRLP treatment. No complications were observed at the site of venipuncture for IRLP. Before initiation of treatment, there was anemia and marked leucocytosis which resolved following treatment. Serum biochemistry showed no significant changes.

CONCLUSIONS

IRLP administration of amphotericin B in a 10 % DMSO solution was easily performed, relatively inexpensive and an effective treatment for treating horses for pythiosis of a limb and resolved the infection with no complications.

Evaluation of regional limb perfusion with chloramphenicol using the saphenous or cephalic vein in standing horses

Regional limb perfusion (RLP) significantly decreases morbidity and mortality associated with distal limb injuries in horses. There is an urgent need for finding additional effective antimicrobial drugs for use in RLP. In this study, we tested the pharmacokinetics (PK) of chloramphenicol in RLP. Eight horses participated in the study, which was approved by the University Animal Care and Use Committee. The cephalic and the saphenous veins were used to perfuse the limbs. Synovial samples were collected from the metacarpo/metatarsophalangeal (MCP/MTP) joint. The Friedman Test was applied for assessing change in PK concentration over time, for all time points. The Wilcoxon Signed Ranks Test was used to test the difference between PK concentration in joint & serum as well as concentration in joint vs. MIC. The comparison of measurements between measurements taken on hind vs. front legs was carried out using the Mann-Whitney Test. A P-value of 5% or less was considered statistically significant. After RLP, the concentration of chloramphenicol in the synovial fluid of the MCP/MTP joint using either the cephalic or the saphenous vein was initially far above the minimal inhibitory concentration (MIC) of most susceptible pathogens and remained above the MIC for approximately 6 h. The results indicate that performing RLP using the cephalic and saphenous veins enables reaching concentrations of chloramphenicol in the MCP/MTP joint that are well above the MIC of most susceptible pathogens. The chloramphenicol concentrations achieved in the synovial fluid of the MCP/MTP joint in the current study were between 1.5 (MTP) and 7 (MCP) times the MIC of MRSA in horses. These results are encouraging since MRSA infections are becoming far more common, causing considerable morbidity. To the best of our knowledge, this is the first study to evaluate the pharmacokinetics of chloramphenicol following RLP in the horse and the results are positive.

Clinical use of antimicrobial regional limb perfusion in horses: 174 cases (1999-2009)

OBJECTIVE

To describe the clinical use of regional limb perfusion with antimicrobials (A-RLP), complications, and outcome in a large series of patients.

DESIGN

Retrospective case series.

ANIMALS

174 horses.

PROCEDURES

Medical records of horses treated with A-RLP between 1999 and 2009 were reviewed. Signalment, primary complaint, horse use, etiology, duration of clinical signs, previous treatment, structures involved, concurrent conditions, A-RLP characteristics, additional treatments, complications, and outcome were recorded. At long-term follow-up, 2 outcomes were investigated: survival rate and return to previous use at the same or higher level. Univariate and multivariate logistic regression analyses were conducted.

RESULTS

Group 1 (96 horses) included septic synovitis. Group 2 (50 horses) included extrasynovial lacerations (23 horses) and fresh, minimally contaminated intrasynovial lacerations without evidence of established synovial infection (27 horses). Group 3 (28 horses) included miscellaneous other conditions. Only minor complications were reported in 12.26% of horses that received IV (n = 155) and 33% of horses that received intraosseous (27) A-RLP. Horses with septic synovitis had a lower survival rate (53.43%) than did horses with lacerations (91.89%). Within group 2, no significant differences in short- or long-term outcomes were found between horses with extrasynovial and fresh, minimally contaminated intrasynovial lacerations. For the horses returning to previous use, 80% of horses with septic synovitis and 72.72% of horses with lacerations were performing at the same or higher level at the time of follow-up.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of the present study indicated that A-RLP is a safe technique with minimal adverse effects. The IV route presented fewer complications than intraosseous injection. Horses with infection of synovial structures had a lower survival rate than did those with acute, minimally contaminated intrasynovial lacerations. The latter had a similar prognosis for horses with extrasynovial lacerations treated with A-RLP.

Indwelling cephalic or saphenous vein catheter use for regional limb perfusion in 44 horses with synovial injury involving the distal aspect of the limb

OBJECTIVE

To describe indwelling cephalic or saphenous vein catheter use for intravenous regional limb perfusion (ID-IV-RLP) to treat horses with synovial injury (contamination/infection) of the distal aspect of the limb.

STUDY DESIGN

Retrospective case series.

ANIMALS

Horses (n = 44; 45 limbs) treated with proximal ID-IV-RLP.

METHODS

Horses had ID-IV-RLP using a cephalic (21 limbs) or saphenous (24 limbs) vein. Amikacin was the most frequently used antibiotic. Number of perfusions ranged from 3 to 21 (median 7). A cast was applied to 14 injured limbs (1 tube cast, 1 full-limb cast, 2 foot casts, and 10 half-limb casts).

RESULTS

Synovial sepsis of the distal portion of 87% of limbs (39) resolved, and 61% of horses returned to soundness. Catheter-related complications occurred in 27% of the limbs but were not significantly associated with outcome. Presence of osteomyelitis was significantly associated with a poor outcome.

CONCLUSIONS

ID-IV-RLP using the cephalic or saphenous vein is an alternative to traditional RLP. An indwelling catheter provided prolonged venous access and facilitated successive perfusions.

Osteomyelitis of the patella in eight foals

OBJECTIVE

To describe the characteristics of osteomyelitis lesions of the patella and to report short- and long-term outcome after treatment in 8 foals.

STUDY DESIGN

Retrospective case series.

ANIMALS

Foals (n = 8).

METHODS

Medical records (2003-2007) and radiographs of foals that had osteomyelitis of the patella were reviewed. Inclusion criteria included clinical, radiographic, and surgical findings consistent with osteomyelitis of the patella, and a long-term follow-up of >15 months. Information acquired included signalment, hematologic and serum biochemical profile results, clinical and radiographic signs, surgical technique and perioperative treatment. Follow-up radiographs were evaluated and outcome was determined from veterinary examination, race records, and telephone questionnaire.

RESULTS

Six foals survived long term (15 months-4 years); all had intralesional and systemic antimicrobial therapy, along with synovial lavage and antimicrobial medication. All were sound and achieved either yearling sales (n=3), show hunter or racing (2). Two foals died in the short term from renal failure and suppurative peritonitis secondary to cecal perforation, 1 remaining lame with suppurative osteonecrosis confirmed at necropsy. This foal was not administered intralesional antimicrobial therapy.

CONCLUSIONS

Prompt medical and surgical therapy for osteomyelitis of the patella can result in a good prognosis for soundness and a potential athletic career. Concurrent septicemia or other systemic perinatal disease can result in prolonged therapy and delayed recovery.

Reinfected revised TKA resolves with an aggressive protocol and antibiotic infusion

BACKGROUND

Revision of failed two-stage revision TKA for infection is challenging, and amputation often is the only alternative.

QUESTIONS/PURPOSES

We asked whether reinfection after two-stage revision for infection could be controlled with an aggressive revision protocol and intraarticular antibiotic infusion.

METHODS

We retrospectively reviewed 18 patients (12 women, six men) who underwent revision for failed reimplantation between January 1999 and January 2008. Mean time from revision for infection to rerevision for reinfection was 5 months (range, 1-18 months). All knees were treated with an individualized protocol that included aggressive exposure, extensive débridement, uncemented components, closure with muscle flaps (seven knees) and other plastic surgery procedures (three knees), and direct antibiotic infusion through Hickman catheters for 6 weeks. Ten knees had one-stage revision; five had débridement, cement spacer, and revision surgery 3 to 4 months later; and three had extensive soft tissue reconstruction before revision surgery. The minimum followup was 2.3 years (mean, 6.1 years; range, 2.3-12.0 years).

RESULTS

The mean Knee Society scores improved from 33 preoperatively to 76. Seventeen of the 18 had control of infection and achieved durable fixation and a closed wound. One patient had recurrent infection 13 months after one-stage revision, was revised, and remained asymptomatic 28 months postoperatively after redébridement and vancomycin infusion for 6 weeks. In one patient, soft tissue closure was not obtained and the patient required amputation.

CONCLUSIONS

Extensile exposure, débridement, and soft tissue flaps for closure combined with uncemented fixation of revision implants and antibiotic infusion into the knee controlled reinfection after revision TKA.

Effect of experimentally induced synovitis on amikacin concentrations after intravenous regional limb perfusion

OBJECTIVES

To determine the effects of experimentally induced synovitis of the radiocarpal joint on the intra-articular pharmacokinetics and pharmacodynamics of amikacin after intravenous regional limb perfusion (IVRLP).

STUDY DESIGN

Randomized crossover experimental design.

ANIMALS

Adult horses (n = 8).

METHODS

Horses were randomly assigned into 2 trials: synovitis and no-synovitis. Radiocarpal joint synovitis was induced with lipopolysaccharide 6 hours before IVRLP. IVRLP (5-mg/kg amikacin qs 60 mL) was performed with a pneumatic tourniquet under general anesthesia. Synovial fluid was obtained before and 0.5, 1, 3, 5, 12, 24, 48 hours after IVRLP. Amikacin concentrations at each time point and pharmacokinetic values were compared between synovitis and no-synovitis trials with Student's t-test.

RESULTS

Amikacin synovial fluid concentrations indicated suspected tourniquet failure on 3 occasions (2 synovitis, 1 no-synovitis) on 3 different horses. Data from both trials in these 3 horses were excluded from further analysis. Observed time to maximal concentration (T(max); mean ± SD = 54 ± 13.42 min) was reached earlier in synovitis joints (5/5, 30 min) than in no-synovitis joints (1/5, 30 min and 4/5, 1 h; P = .0476) (P = .0161). Mean observed maximal concentration (C(max)) was higher in synovitis joints (144.48 ± 43.17 μg/mL) than in no-synovitis joints (60.02 ± 28.81 μg/mL; P = .0301). The recommended C(max): minimum inhibitory concentration ratio of 8 was achieved in 3/5 of the successfully perfused joints with induced synovitis, but this ratio was not achieved in any of the clinically normal joints.

CONCLUSION

Synovitis of the radiocarpal joint resulted in an earlier observed T(max) and higher observed C(max) of intra-articular amikacin after IVRLP compared with normal joints.

Methicillin-resistant Staphylococcus aureus in TKA treated with revision and direct intra-articular antibiotic infusion

BACKGROUND

Resistant organisms are difficult to eradicate in infected total knee arthroplasty. While most surgeons use antibiotic-impregnated cement in these revisions, the delivery of the drug in adequate doses is limited in penetration and duration. Direct infusion is an alternate technique.

QUESTIONS/PURPOSES

We asked whether single-stage revision and direct antibiotic infusion for infected TKA would control infection in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections.

METHODS

We retrospectively reviewed 18 patients (18 knees) with MRSA with one-stage revision protocol that included débridement, uncemented revision of total knee components, and intraarticular infusion of 500 mg vancomycin via Hickman catheter once or twice daily for 6 weeks; we used no intravenous antibiotics after the first 24 hours. We monitored serum vancomycin levels to maintain levels between 3 and 10 microg/mL. Minimum followup was 27 months (range, 27–75 months). Mean followup was 62 months, (range, 27–96 months).

RESULTS

Infection was controlled at last followup in all but one patient with a recurrence of the MRSA. The patient was reoperated at 5 months; a necrotic bone fragment was removed, the knee was débrided and revised, and the antibiotic infusion protocol readministered. The patient remained free of infection 42 months postoperatively. At 2-year followup, the mean Knee Society score was 83. We observed no radiographic evidence of implant migration.

CONCLUSIONS

One-stage revision and 6 weeks of intraarticular vancomycin administration controlled infection in MRSA infected TKA with no apparent complications.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Efficacy of three tourniquet types for intravenous antimicrobial regional limb perfusion in standing horses

OBJECTIVE

To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN]).

ANIMALS

Horses (n=9).

METHODS

Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was obtained 0.5 hour after perfusion. Amikacin concentration in the synovial fluid was detected using fluorescence polarization immunoassay.

RESULTS

Mean synovial concentrations of amikacin in the PN (mean 236 μg/mL; range 23-913 μg/mL) and WR (mean 64.2 μg/mL; range 7-315 μg/mL) were significantly higher (P=.000 and .032, respectively) than the NR tourniquet (mean 2.1 μg/mL; range 0.9-3.3 μg/mL).

CONCLUSIONS

The PN tourniquet resulted in the highest synovial fluid amikacin concentrations in all horses, although administration with PN and WR tourniquets achieved adequate amikacin concentrations. NR tourniquet is ineffective and should not be used for RLP above the carpus in the standing horse.

Antimicrobial delivery by intrasynovial catheterisation with systemic administration for equine synovial trauma and sepsis

OBJECTIVE

To present the technique for intra-articular catheter placement and report the clinical outcomes of 38 cases of equine synovial trauma and/or infection treated with broad-spectrum antimicrobials administered via an intrasynovial catheter (ISC).

DESIGN

Retrospective study.

PROCEDURE

Medical records of 38 horses treated for synovial trauma and sepsis with frequent antimicrobial administration through an ISC from 1995 to 2008 were reviewed. Follow-up information was obtained via clinical re-evaluation or telephone contact with the owners.

RESULTS

The majority of horses (84%) received amikacin and Timentin(R) four times daily. In addition, synovial lavage through the ISC was carried out in 27 horses (71%). Only radiological evidence of osteolysis had a significant negative impact on both lameness at the time of hospital discharge and the long-term outcome. In total, 92% of horses treated with frequent antimicrobial administration through an ISC had clinical resolution of infection. Catheter obstruction occurred in three cases, necessitating replacement or removal, and two synovial fistulae developed at sites of open drainage. The majority of horses treated had a favourable outcome, with 86% being at least pasture sound and 43% returned to riding.

CONCLUSION

Septic synovial structures treated with frequent antimicrobial administration through an ISC had a good prognosis for survival and 43% returned to riding, which is consistent with the results of other studies. The use of a simple ISC should be considered when broad-spectrum intrasynovial antimicrobial administration and lavage of a septic synovial structure are indicated.

New antimicrobials, systemic distribution, and local methods of antimicrobial delivery in horses

The local delivery of antimicrobials is a valuable therapeutic tool with a low morbidity, is practical to use, and is well tolerated by horses. Clinically, its use has allowed equine practitioners to achieve better results when treating musculoskeletal infections, and it represents an extremely useful tool in the practitioner's armamentarium against these types of infections. The technique is indicated to combat orthopedic infections involving bones, joints, physes, tendon sheaths, and foot tissues. Optimal treatment must include other approaches, such as systemic antimicrobial therapy and surgical debridement and lavage, and monitoring of the clinical progression of the patient can help to determine the ideal protocol for each patient.