Konstantinos Anagnostakos

Antibiotic-impregnated PMMA hip spacers: Current status.

The infection rate after primary hip arthroplasty lies at 1–2%. In the past few years, a two-stage protocol with the implantation of an antibiotic-loaded spacer has become a popular procedure in the treatment of infected hip joint arthroplasties. In this review, we pay special attention to the elution characteristics of the spacers, their mechanical stability and the clinical response. We conclude that hip spacers are an effective method in the treatment of hip joint infections, with success rates of over 90%.

Elution of gentamicin and vancomycin from polymethylmethacrylate beads and hip spacers in vivo

Background and purpose Late infections after total hip arthroplasty are still a problem. Treatment procedures include resection arthroplasty with implantation of antibiotic-loaded beads or implantation of an antibiotic-impreganted spacer. However, little is known about antibiotic elution from bone cement beyond the first 2–3 postoperative days in humans. Methods 17 hip spacers (80g PMMA, 1g gentamicin, and 4 g vancomycin) and 11 chains (40 g PMMA, 0.5 g gentamicin, and 2 g vancomycin) in 28 patients were studied. The release of both agents was measured in the drainage fluid on a daily basis. The drains were left in situ until less than 50 mL was produced per day. The elution of both antibiotics was determined by fluorescence polarization immunoassay. Systemic antibiotics were given postoperatively according to antibiogram. If possible, no gentamicin or vancomycin was given. Results Peak mean concentrations from beads and spacers were reached for gentamicin (1,160 (12–371) µg/mL and 21 (0.7–39) µg/mL, respectively) and for vancomycin (80 (21–198) µg/mL and 37 (3.3–72) µg/mL) on day 1. The last concentrations to be determined were 3.7 µg/mL gentamicin and 23 µg/mL vancomycin in the beads group after 13 days, and 1.9 µg/mL gentamicin and 6.6 µg/mL vancomycin in the spacer group after 7 days. Between the fifth and seventh day, an intermittent increase in elution of vancomycin from both beads and spacers and of gentamicin from spacers was noticed. No renal or hepatic dysfunction was observed. Interpretation Beads showed higher elution characteristics in vivo than the spacers due to their larger surface area; however, a great amount of inter-subject variability was seen for both beads and spacers. The inferior elution properties of spacers emphasize the importance of additional systemic antibiotics for this treatment procedure during the postoperative period. Future studies should clarify whether the dose of antibiotics or length of antibiotic therapy may be reduced in the case of bead implantation, without jeopardizing the control of infection.

Nonoperative management of adhesive capsulitis of the shoulder: Oral cortisone application versus intra-articular cortisone injections

HYPOTHESIS Oral and intra-articular injections of cortisone will lead to significant improvement and comparable results in the treatment of adhesive capsulitis of the shoulder. MATERIALS AND METHODS In a prospective randomized evaluation, 40 patients with idiopathic adhesive capsulitis of the shoulder were treated with an oral corticoid treatment regimen or 3 intra-articular injections of corticosteroids. Follow-up was after 4, 8, and 12 weeks, and 6 and 12 months. For the clinical evaluation, the Constant-Murley (CM) score, the Simple Shoulder Test (SST) and visual analog scales (VAS) for pain, function, and satisfaction were used. RESULTS In the patients treated with oral glucocorticoids, significant improvements were found for the CM score (P < .0001), SST (P=.035), VAS (P < .0001), and range of motion (P < .05) at the 4-week follow-up. The patients treated with an intra-articular glucocorticoid injection series also significantly improved in the CM score (P < .0001), SST (P < .0001), the VAS (P < .0001), and range of motion (P < .05) after 4 weeks. These results were confirmed at all other follow-up visits. Superior results were found for intra-articular injections in range of motion, CM score, SST, and patient satisfaction (P < .05). Differences in the VAS for pain and function were not significant (P > .05). DISCUSSION The use of cortisone in the treatment of idiopathic shoulder adhesive capsulitis leads to fast pain relief and improves range of motion. Intra-articular injections of glucocorticoids showed superior results in objective shoulder scores, range of motion, and patient satisfaction compared with a short course of oral corticosteroids.

Persistence of bacterial growth on antibiotic-loaded beads: Is it actually a problem?

Background and purpose Implantation of antibiotic-loaded beads is used for orthopedic infections. However, recent in vitro reports have emphasized that bacteria can persist on—or even colonize—antibiotic-impregnated bone cement. We therefore assessed whether bacterial adherence and growth could be determined on gentami-cin- and gentamicin-vancomycin-loaded beads that had been removed after eradication of infection. Material and methods We bacteriologically examined 18 chains of antibiotic-loaded beads (11 gentami-cin-loaded, 7 gentamicin-vancomycin-loaded) that had been implanted because of orthopedic infections. Among the causative agents, Staphylococcus epidermidis, Staph-ylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) were the most frequent organisms identified. Results In 4 cases (3 with S. epidermidis and one with MRSA), we found that there was persistence of bacterial growth on the beads. S. epidermidis strains persisted only on gentamicin-loaded beads, while MRSA could grow on gentamicin-vancomycin-impregnated cement. In one case, the emergence of a gentamicin-resistant S. epidermidis strain was observed despite the fact that preoperative samples of S. epidermidis from this patient had been susceptible to the antibiotic. Interpretation Persistence of bacterial growth on bone cement remains a hazardous problem in orthopedic surgery. Adherence of bacteria to cement can lead to emergence of bacterial resistance to antibiotics and might result in clinical recurrence of infection.

Enhancement of antibiotic elution from acrylic bone cement

Antibiotic-loaded acrylic bone cement is a well-established tool in the prophylaxis and treatment of orthopedic infections. Numerous studies about its pharmacokinetic properties have demonstrated that only a small part of the incorporated antibiotic amounts can be released, mostly over the first 8-10 weeks. Therefore, in the past 10 years, several attempts have been made for enhancement of the drug elution from bone cement. This article reviews this experience and pays special attention on biantibiotic combinations, additives other than antimicrobial agents, as well as the effect of ultrasound on the antibiotic elution characteristics.

Rupture of the anterior tibial tendon: three clinical cases, anatomical study, and literature review.

Background: We report three cases of anterior tibial tendon ruptures and the results of an anatomical study in regard to the tendons insertion site and a literature review. Methods: Three patients were referred to our hospital with anterior tibial tendon ruptures. In the anatomical study, 53 feet were dissected, looking in particular for variants of the bony insertion of the tendon. Results: Two patients had surgical treatment (one primary repair and one semimembranosus tendon graft) and one conservative treatment. After a mean followup of 14 weeks all patients had satisfactory outcomes. In the anatomical study, we noted three different insertion sites: in 36 feet the tendon inserted into the medial side of the cuneiform and the base of the first metatarsal bone and in 13 feet only into the medial side of the cuneiform bone. In the remaining four feet the tendon inserted into the cuneiform and the first metatarsal bone, but an additional tendon was noted taking its origin from the anterior tibial tendon near its insertion into the medial cuneiform and attaching to the proximal part of the first metatarsal. Conclusions: According to literature, surgical repair is the treatment of choice for acute ruptures and for patients with high activity levels. For chronic ruptures and patients with low demands, conservative management may lead to an equally good outcome. Knowledge of the anatomy in this region may be helpful for diagnosis and for the interpretation of intraoperative findings and choosing the most appropriate surgical procedure.

Fungal periprosthetic hip and knee joint infections clinical experience with a 2-stage treatment protocol.

Fungal periprosthetic joint infections are a rare entity in orthopedic surgery, and there exist no guidelines according to which these infections can be successfully managed. Between 2004 and 2009, 7 patients with fungal periprosthetic joint infections (4 total hip arthroplasties and 3 total knee arthroplasties) have been treated with a 2-stage protocol and implantation of antibiotic-loaded cement spacers. Most of the infection was caused by Candida species. Systemic antifungal agents were administered for 6 weeks in 6 cases and 6 months in 1 case. The mean spacer implantation time was 12 weeks. At a mean follow-up of 28 months (5-70 months), no persistence of infection or reinfection could be observed. A 2-stage treatment protocol with implantation of an antibiotic-loaded cement spacer is an efficient option in the treatment of fungal periprosthetic infections.

In Vivo and In Vitro Studies of Antibiotic Release from and Bacterial Growth Inhibition by Antibiotic-Impregnated Polymethylmethacrylate Hip Spacers

ABSTRACT The antimicrobial properties and the elution characteristics of gentamicin-vancomycin-loaded hip spacers were studied in vivo and in vitro. Vancomycin elution was greater than gentamicin elution. The antibiotic concentrations in vivo were less than those in vitro. Not dependent on implantation duration, growth inhibition by spacers in vitro was observed for 2 weeks. The reason for protracted wound healing cannot be insufficient antibiotic release.

Antimicrobial properties and elution kinetics of linezolid-loaded hip spacers in vitro

Bacterial adhesion to and -persistence on antibiotic-loaded bone cement is an increasing problem. New antibiotics with good antimicrobial and pharmacokinetic properties (e.g. linezolid) may be the solution to this problem; however, few data concerning linezolid-loaded acrylic cement are currently available. Ten gentamicin-linezolid-loaded hip spacers (1 g gentamicin/2.4 g linezolid/80 g PMMA; five spacers including a metallic endoskeleton, five with no metallic components) were tested in vitro against a strain of methicillin-resistant Staphylococcus aureus with regard to antibiotic release and bacteria growth inhibition. Daily, the antibiotic elution was determined by high liquid performance chromatography (linezolid) and fluorescence polarization immunoassay (gentamicin), the bacteria growth inhibition photometrically at 546 nm. All spacers demonstrated growth inhibition for 8 days. Peak average concentrations were reached for both agents on day 1 (gentamicin-35.10 mug/mL [24.10-52.52], linezolid-36.28 mug/mL [22.87-71.76]). After 8 days, 0.97% [0.93-1.05%] of the initial amount of linezolid and 3.13% [2.85-3.31%] of gentamicin were meanly released from spacers containing a metallic endoskeleton. In those containing of simple cement these values were 1.22% [0.91-1.59%] and 2.67% [2.12-2.73%], respectively. Linezolid demonstrated acceptable elution kinetics from bone cement; however, further experimental research and animal studies should clarify any possible side effect of linezolid-loaded cement media before definitive use in the clinical practice.

Three-Dimensional Evaluation of the Cyclic Loading Behavior of Different Rotator Cuff Reconstructions

PURPOSE To perform a biomechanical comparison of single-row rotator cuff repairs with modified suture configurations versus double-row repairs using radiostereometric analysis (RSA). METHODS The infraspinatus tendon and the humerus of 40 porcine cadaveric shoulders were marked with tantalum beads and placed in an RSA calibration cage that allows for calculation of 3-dimensional positions of the tantalum markers. The intact tendon was cyclically loaded (50 cycles/20 N). After sharp dissection of the infraspinatus from the bone, the repairs were made by use of 3 single-row (modified Mason-Allen, double mattress, inclined mattress) and 2 double-row (modified Mason-Allen, suture bridge) configurations. The reconstructions were cyclically loaded for 50 cycles (10 N to 40, 60, 80, and 100 N). Displacements under cyclic loading were quantified in the anteroposterior (x), craniocaudal (y), and mediolateral (z) direction. The craniocaudal measurements were compared with the results of a video extensometer. RESULTS Cyclic loading of the intact tendon showed a mean displacement of 0.06 +/- 0.08 mm at the x-level, 0.16 +/- 0.18 mm at the y-level, and 0.19 +/- 0.28 mm at the z-level. High correlations between the RSA and the video extensometer measurements were found (0.87). Comparison of rotator cuff repairs showed significant differences in gap formation at 40, 60, 80, and 100 N in the craniocaudal plane (P < .0001) and the mediolateral plane (P <or= .05), with the double-row Mason-Allen repair providing the lowest gap formation of all tested configurations. However, these results were not statistically significant compared with the single-row double-mattress repair. No significant differences were measured at the anteroposterior level (P > .05). CONCLUSIONS Single-row repairs using modified Mason-Allen or double-mattress repair were able to achieve biomechanical results comparable to double-row repairs as measured by RSA and digital video. CLINICAL RELEVANCE Single-row repairs, using modified suture configurations, were able to decrease implant costs compared with double-row repairs, by achieving comparable results. Furthermore, RSA gives additional information on the applied forces acting on the rotator cuff repair in 3 different planes, which may help to decrease the rerupture rate of rotator cuff reconstructions.