H. Charles Vogely

Identification of orthopaedic infections using broad-range polymerase chain reaction and reverse line blot hybridization.

BACKGROUND Culture remains the gold standard in the diagnosis of bacterial infection, but molecular biological techniques have yielded promising results. In this study, we validated a combined polymerase chain reaction and reverse line blot hybridization protocol for identifying musculoskeletal infections. METHODS Samples were obtained from seventy-six patients undergoing orthopaedic surgery for various aseptic and septic indications. The diagnosis of infection was based on a review of all available clinical and culture data. In addition to routine culture for aerobic and anaerobic growth, samples were analyzed with a broad-range 16S rRNA polymerase chain reaction and subsequent reverse line blot hybridization with use of twenty-eight group, genus, and species-specific oligonucleotide probes. RESULTS An infection was diagnosed on the basis of patient data in thirty-one patients. All but one of the patients with a clinical diagnosis of infection had a positive result of the polymerase chain reaction-reverse line blot hybridization. Five of the forty-five patients in whom an infection was not suspected on the basis of patient data had at least one positive result of the polymerase chain reaction-reverse line blot hybridization. Cultures demonstrated microorganisms in twenty-five patients with an infection and in two patients in whom an infection was not suspected on the basis of the patient data. Staphylococcus aureus was the most common organism grown on culture. The species identified by the polymerase chain reaction-reverse line blot hybridization was in full accordance with that grown on culture in all but one patient. CONCLUSIONS Polymerase chain reaction-reverse line blot hybridization performed well in detecting and identifying the various bacterial species and was more sensitive than routine culture. It identified Staphylococcus aureus as the most frequently found microorganism. Five patients in whom an infection was not suspected on the basis of the patient data had a positive result of the polymerase chain reaction, which may have been caused by contamination of the samples. However, three of these patients had aseptic loosening of a total hip prosthesis, suggesting the presence of a low-grade bacterial infection that remained undetected by the culture but was detected by the polymerase chain reaction-reverse line blot hybridization. LEVEL OF EVIDENCE Diagnostic Level III.

In Vitro Release of Antibiotics from Commercial PMMA Beads and Articulating Hip Spacers

The efficacy and benefits of high-dose antibiotic cement spacers compared with beads in the treatment of an infected prosthesis have been shown. However, in clinical practice, commercial, low-dose antibiotic bone cement is often used. This study investigated the in vitro antibiotic release of hip spacers made from Refobacin-Palacos-R or Antibiotic-Simplex-P cement compared with Septopal beads. Antibiotic concentrations were measured during 6 weeks. All carriers showed a burst release, but spacers showed little additional release after the first week. Cumulative release was 27.5 +/- 2.3 mg for Palacos, 23.8 +/- 0.2 mg for Simplex, and 188.3 +/- 9.3 mg for Septopal (P < .001). Despite the efficacy of high-dose antibiotic bone cement spacers, we believe one should be cautious toward using low-dose antibiotic bone cement for spacers because this could result in an unsuccessful eradication of infection.

Incidence of low-grade infection in aseptic loosening of total hip arthroplasty

Purpose We investigated the hypothesis that many total hip arthroplasty revisions that are classified as aseptic are in fact low-grade infections missed with routine diagnostics. Methods In 7 Dutch hospitals, 176 consecutive patients with the preoperative diagnosis of aseptic loosening of their total hip arthroplasty were enrolled. During surgery, between 14 and 20 tissue samples were obtained for culture, pathology, and broad-range 16S rRNA PCR with reverse line blot hybridization. Patients were classified as either not being infected, suspected of having infection, or infected according to strict, predefined criteria. Each patient had a follow-up visit after 1 year. Results 7 patients were classified as infected, 4 of whom were not identified by routine culture. 15 additional patients were suspected of having infection. 20 of these 22 patients received a cemented prosthesis, fixated with antibiotic-loaded bone cement. All 22 patients received prophylactic systemic antibiotics. 7 of them reported complaints one year after surgery, but only one showed signs of early loosening. However, additional surgery was not performed in any of the patients. Interpretation Although the proportions were not as high as previously reported in the literature, between 4% and 13% of patients with the preoperative diagnosis of aseptic loosening were infected. However, as thorough debridement was performed during surgery and prophylactic antibiotics were used, the diagnosis of infection did not have any obvious clinical consequences, as most patients performed well at the 1-year follow-up. Whether this observation has implications for long-term implant survival remains to be seen.

Prophylaxis of infection and effects on osseointegration using a tobramycin-periapatite coating on titanium implants—An experimental study in the rabbit

No options are available for local antibiotic delivery from uncemented implants. By loading a porous titanium implant with a biomimetic HA‐coating (PeriApatite, PA) with antibiotics, we could obtain adequate local antibiotic concentrations and reduce infection susceptibility. This study investigated the efficacy of a tobramycin‐loaded PA‐coated titanium foam implant in preventing infection, as well as the effects on osseointegration. In 72 New Zealand White rabbits, an uncoated (Ti), PA‐coated (PA), or Tobramycin‐PA‐coated (PA‐tobra) titanium foam rod was implanted intramedullary in the left tibiae after contamination of the implant bed with none (control), 103, 104 or 105 CFU Staphylococcus aureus. PA‐tobra implants were loaded with 2.4 mg tobramycin. After 28 days analysis was done by bacteriology, histopathology and histomorphometry. Six percent of the contaminated PA‐tobra rabbits were infected, whereas this was 53 and 67% for PA and Ti, respectively (p < 0.001). Quantitative cultures were also significantly lower in the PA‐tobra group (p = 0.003). None of the control rabbits were infected. Histopathological and histomorphometrical scores were both better for the PA‐tobra group, although only significant compared to Ti. No significant differences were observed between PA and Ti rabbits. We conclude that the application of tobramycin to PA‐coated titanium foam implants appears to be an effective local antibiotic strategy for uncemented implants for infection prophylaxis and has a beneficial effect on implant fixation, which will result in improved long‐term implant survival.

No efficacy of silver bone cement in the prevention of methicillin-sensitive Staphylococcal infections in a rabbit contaminated implant bed model

Data from literature showed that a new type of metallic silver PMMA cement had good results in infection prophylaxis. This study investigated the in vivo efficacy of silver cement in the prevention of methicillin‐sensitive Staphylococcal infections, compared to plain and tobramycin‐containing cement. In 48 rabbits, 0.6% silver, 1% silver, plain, or tobramycin PMMA cement was injected into the femoral medullary canal after contamination with 105, 106, or 107 colony forming units (CFU) Staphylococcus aureus. After 14 days, bone was collected for bacteriology and histopathology. All plain and silver cement rabbits were infected, whereas only two tobra rabbits were infected (p < 0.001). The number of bacteria cultured (10logCFU) from bone adjacent to the cement, was 6.4 ± 0.3 and 6.1 ± 0.3 for the 0.6% and 1% silver rabbits. For the rabbits with plain and tobra cement, this was 6.2 ± 0.2 (p > 0.95) and 0.0 ± 0.0 (p < 0.001), respectively. Two tobra rabbits had a positive culture of a distal bone sample. Histological sections of plain, 0.6%, and 1% silver rabbits all showed signs of infection; these signs were absent in the tobra rabbits. Silver and plain cement were not effective in preventing infection, whereas tobra cement was effective. As silver cement predominantly exhibits an antimicrobial effect at the direct cement surface, this cement seems less useful in situations where there are bacteria present in surrounding tissues, like revision surgery. Whether silver cement has relevance in the prevention of bacterial colonization of cement remains to be determined.

Acquisition of high-level mupirocin resistance in CoNS following nasal decolonization with mupirocin

OBJECTIVES The association between mupirocin use and plasmid-based high-level resistance development mediated through mupA in CoNS has not been quantified. We determined acquisition of mupirocin resistance in Staphylococcus aureus and CoNS in surgery patients treated peri-operatively with mupirocin. PATIENTS AND METHODS Patients admitted for surgery were treated with nasal mupirocin ointment and chlorhexidine soap for 5 days, irrespective of S. aureus carrier status. Nasal swabs were obtained before decolonization (T1) and 4 days after surgery (T2) and were inoculated onto agars containing 8 mg/L mupirocin. Staphylococci were identified by MALDI-TOF MS and mupirocin resistance was confirmed by Etest. RESULTS Among 1578 surgical patients, 936 (59%) had nasal swabs obtained at T1 and T2; 192 (21%) patients carried mupirocin-resistant CoNS at T1 and 406 (43%) at T2 (P<0.001). Of 744 patients not colonized at T1, 277 acquired resistance (37%), corresponding to an acquisition rate of 7.4/100 patient days at risk. In all, 588 (97%) of 607 mupirocin-resistant CoNS had an MIC >256 mg/L (high level) and 381 of 383 (99.5%) were mupA positive. No acquisition of mupirocin resistance was observed in S. aureus. CONCLUSIONS Acquisition of mupirocin resistance following decolonization was widespread in CoNS and absent in S. aureus. As almost all isolates harboured the mupA gene, monitoring resistance development in S. aureus when decolonization strategies containing mupirocin are used is recommended.

Do Monoblock Cups Improve Survivorship, Decrease Wear, or Reduce Osteolysis in Uncemented Total Hip Arthroplasty?

BackgroundMonoblock acetabular components used in uncemented total hip arthroplasty (THA) have certain mechanical characteristics that potentially reduce acetabular osteolysis and polyethylene wear. However, the degree to which they achieve this goal is not well documented.Questions/purposesThe purpose of this study was to use a systematic review of controlled trials to test the hypothesis that monoblock cups have superior (1) polyethylene wear rate; (2) frequency of cup migration; (3) frequency of acetabular osteolysis; and (4) frequency of aseptic loosening compared with modular components used in uncemented THA.MethodsA systematic search was conducted in the Medline, Embase, and Cochrane electronic databases to assemble all controlled trials comparing monoblock with modular uncemented acetabular components in primary THA. Included studies were considered “best evidence” if the quality score was either ≥ 50% on the Cochrane Back Review Group checklist or ≥ 75% the Newcastle-Ottawa quality assessment scale. A total of seven publications met our inclusion criteria.ResultsBest evidence analysis showed no difference in polyethylene wear rate, the frequency of cup migration, and aseptic loosening between monoblock and modular acetabular components. No convincing evidence was found for the claim that lower frequencies of acetabular osteolysis are observed with the use of monoblock cups compared with modular uncemented cups.ConclusionsThe purported benefits of monoblock cups were not substantiated by this systematic review of controlled studies in that polyethylene wear rates and frequencies of cup failure and acetabular osteolysis were similar to those observed with modular implants. Other factors should therefore drive implant selection in cementless THA.Level of EvidenceLevel III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Missed low-grade infection in suspected aseptic loosening has no consequences for the survival of total hip arthroplasty

Background and purpose — Aseptic loosening and infection are 2 of the most common causes of revision of hip implants. Antibiotic prophylaxis reduces not only the rate of revision due to infection but also the rate of revision due to aseptic loosening. This suggests under-diagnosis of infections in patients with presumed aseptic loosening and indicates that current diagnostic tools are suboptimal. In a previous multicenter study on 176 patients undergoing revision of a total hip arthroplasty due to presumed aseptic loosening, optimized diagnostics revealed that 4–13% of the patients had a low-grade infection. These infections were not treated as such, and in the current follow-up study the effect on mid- to long-term implant survival was investigated. Patients and methods — Patients were sent a 2-part questionnaire. Part A requested information about possible re-revisions of their total hip arthroplasty. Part B consisted of 3 patient-related outcome measure questionnaires (EQ5D, Oxford hip score, and visual analog scale for pain). Additional information was retrieved from the medical records. The group of patients found to have a low-grade infection was compared to those with aseptic loosening. Results — 173 of 176 patients from the original study were included. In the follow-up time between the revision surgery and the current study (mean 7.5 years), 31 patients had died. No statistically significant difference in the number of re-revisions was found between the infection group (2 out of 21) and the aseptic loosening group (13 out of 152); nor was there any significant difference in the time to re-revision. Quality of life, function, and pain were similar between the groups, but only 99 (57%) of the patients returned part B. Interpretation — Under-diagnosis of low-grade infection in conjunction with presumed aseptic revision of total hip arthroplasty may not affect implant survival.

Real-time visual biofeedback to improve therapy compliance after total hip arthroplasty: A pilot randomized controlled trial

BACKGROUND Previous studies have shown limited therapy compliance in weight-bearing in patients following total hip arthroplasty. RESEARCH QUESTION The purpose of this pilot RCT is to determine the immediate and late effect of real-time, visual biofeedback on weight-bearing during rehabilitation after THA in elderly. METHODS 24 participants who underwent THA were randomized to either the control or the intervention group. The intervention group received real-time, visual biofeedback on weight-bearing during training with the physical therapist during hospitalization and at twelve weeks follow up. RESULTS Without biofeedback, therapy compliance was limited. Significant improvement in peak load was found in the intervention group in the early postoperative phase. In contrast to the control group, the peak load at twelve weeks was significantly higher in the intervention group compared to the pre-operative peak load, indicating a lasting effect of early biofeedback. Other gait parameters were not significantly different in the early postoperative phase. In the intervention group a longer walking distance was observed and the use of walking aids was reduced at twelve weeks. SIGNIFICANCE Biofeedback systems could be promising to improve outcomes and reduce costs in future rehabilitation programs after THA.

An uncemented iso-elastic monoblock acetabular component : Preliminary results

Little is known about the clinical application of highly cross-linked polyethylene (HXLPE) blended with vitamin E. This study evaluates an uncemented iso-elastic monoblock cup with vitamin E blended HXLPE. 112 patients were followed up for 2years. 95.5% completed the follow-up. The mean VAS score for patient satisfaction was 8.8 and the mean Harris Hip Score was 94.2. In 7 cases initial gaps behind the cup were observed, which disappeared completely during follow-up in 6 cases. The mean femoral head penetration rate was 0.055mm/year. No adverse reactions or abnormal mechanical behavior was observed with the short term use of vitamin E blended HXLPE. This study shows the promising performance of this cup and confirms the potential of vitamin E blended HXLPE.