Scott R. Nodzo

Antimicrobial Susceptibility of Propionibacterium acnes Isolates from Shoulder Surgery

ABSTRACT Orthopedic surgeons at our institution have noticed an increase in the number of infections due to Propionibacterium acnes, especially following operations on the shoulder. We collected P. acnes isolates from our hospital microbiology laboratory for 1 year and performed antimicrobial susceptibility testing on 28 strains from the shoulder. Antibiotics with the lowest MIC values against P. acnes (MIC50 and MIC90) included penicillin G (0.006, 0.125), cephalothin (0.047 and 0.094), and ceftriaxone (0.016, 0.045), while others also showed activity. Strains resistant to clindamycin were noted.

Hemiarthroplasty of the distal humerus for acute and chronic complex intra-articular injuries

BACKGROUND Comminuted intra-articular distal humeral fractures represent a challenging upper extremity injury. This study reviews clinical and radiographic results in patients with distal humeral hemiarthroplasty (DHH). METHODS DHH with the Latitude prosthesis (Tornier, Saint-Ismier, France) was performed in 8 patients (mean age, 64 years; age range, 33-75 years) for unreconstructible fractures of the distal humerus or salvage of failed internal fixation. Clinical outcomes were assessed with the American Shoulder and Elbow Surgeons elbow instrument; Mayo Elbow Performance Index; and Disabilities of the Arm, Shoulder and Hand questionnaire at a mean of 36 months. Radiologic assessment included radiographs and computed tomography to evaluate olecranon wear and densitometry (dual-energy x-ray absorptiometry). Range of motion, pain, and elbow satisfaction were recorded, and descriptive statistics were used for analysis. RESULTS Seven patients were available to participate in the follow-up examination. Acute cases (5 patients) scored better than salvage cases (2 patients) on the Mayo Elbow Performance Score (80 points [range, 67-95 points] and 65 points [range, 50-80 points], respectively) and Disabilities of the Arm, Shoulder and Hand score (31 points [range, 2.5-68 points] and 39 points [range, 17-62 points], respectively). The mean arc of elbow flexion and extension was 96° (range, 70°-130°), with mean flexion of 120° (range, 90°-135°) and a mean extension loss of 19° (range, 5°-30°). The mean arc of forearm rotation was 160° (range, 140°-180°). Reoperation was required in 4 patients because of painful retained hardware. Five patients reported pain with activities of daily living. CONCLUSION DHH should be used with caution until such time as longer-term outcome studies are able to show the efficacy of this procedure.

Cathodic voltage-controlled electrical stimulation of titanium implants as treatment for methicillin-resistant Staphylococcus aureus periprosthetic infections

Effective treatment options are often limited for implant-associated orthopedic infections. In this study we evaluated the antimicrobial effects of applying cathodic voltage-controlled electrical stimulation (CVCES) of -1.8 V (vs. Ag/AgCl) to commercially pure titanium (cpTi) substrates with preformed biofilm-like structures of methicillin-resistant Staphylococcus aureus (MRSA). The in vitro studies showed that as compared to the open circuit potential (OCP) conditions, CVCES of -1.8 V for 1 h significantly reduced the colony-forming units (CFU) of MRSA enumerated from the cpTi by 97% (1.89 × 106 vs 6.45 × 104 CFU/ml) and from the surrounding solution by 92% (6.63 × 105 vs. 5.15 × 104 CFU/ml). The in vivo studies, utilizing a rodent periprosthetic infection model, showed that as compared to the OCP conditions, CVCES at -1.8 V for 1 h significantly reduced MRSA CFUs in the bone tissue by 87% (1.15 × 105 vs. 1.48 × 104 CFU/ml) and reduced CFU on the cpTi implant by 98% (5.48 × 104 vs 1.16 × 103 CFU/ml). The stimulation was not associated with histological changes in the host tissue surrounding the implant. As compared to the OCP conditions, the -1.8 V stimulation significantly increased the interfacial capacitance (18.93 vs. 98.25 μF/cm(2)) and decreased polarization resistance (868,250 vs. 108 Ω-cm(2)) of the cpTi. The antimicrobial effects are thought to be associated with these voltage-dependent electrochemical surface properties of the cpTi.

Short to midterm clinical and radiographic outcomes of the Salto total ankle prosthesis.

Background: Total ankle arthroplasty (TAA) has become an increasingly effective treatment option for tibiotalar arthritis. The purpose of this study was to evaluate the short to midterm clinical and radiographic outcomes of the Salto fixed bearing total ankle prosthesis. Methods: We retrospectively reviewed the radiographs and patient records of 74 consecutive patients with 75 TAA implants from January 2007 to April 2011. The average age was 60.6 years (range, 41-82) with 41 females and 33 males. The average clinical follow-up was 43 months (range, 24-73 months). Radiographs were reviewed for areas of radiolucency and cystic changes around the talar and tibial implants, as well as for implant migration using standardized tibal, talar, talocalcaneal, and tibial slope angular measurements. The validated Foot and Ankle Outcome Score (FAOS), Short Form-12 (SF-12), and Visual Analog Scale (VAS) were used as subjective patient outcome measures. Kaplan Meier (K-M) curves were created for implant survivorship with revision of components as an endpoint and for return to the operating room for any reason. Results: Total ankle survivorship was 98%. Thirteen patients returned to the operating room for any reason. There was 1 deep infection, and no ankles were converted to an arthrodesis. Average ankle dorsiflexion and plantarflexion improved from 4.3 ± 3.3 to 8.7 ± 5.6 degrees (P = .0008) and 24 ± 11 to 29 ± 7 degrees (P = .04), respectively. Patients showed significant improvements in all subscales of the FAOS (P < .0001). The physical component of the SF-12 significantly improved from 30 ± 8 to 41 ± 13 (P < .0001), but this was not observed with the mental component (52 ± 1 vs 53 ± 1, P = .55). The mean VAS for patient satisfaction was 9 (range, 2-10). Two patients had component migration (1 tibial and 1 talar component), neither of which required a revision procedure. Six ankles had a total of 9 radiolucent lines with a radiographically stable implant, and no patients had cystic changes. Conclusion: This is one of the first articles to report clinical and radiographic outcome data for the fixed bearing version of this prosthesis. We observed significant improvements in subjective outcome measures and range of motion with a 98% component survivorship at short to midterm follow-up. Longer follow-up will be necessary to determine the durability of this implant. Level of Evidence: Level IV, case series.

Conventional diagnostic challenges in periprosthetic joint infection.

Periprosthetic joint infection remains a clinical challenge with no benchmark for diagnosis. The diagnosis is based on many different clinical variables that may be difficult to interpret, especially in the setting of chronic systemic disease. Synovial fluid aspiration, diagnostic imaging, traditional culture, peripheral serum inflammatory markers, and intraoperative frozen sections each have their limitations but continue to be the mainstay for diagnosis of periprosthetic joint infection. As molecular- and biomarker-based technologies improve, the way we interpret and diagnose periprosthetic joint infection will ultimately change and may even improve diagnostic accuracy and turnaround time. Future research on this topic should be focused on improving diagnostic criteria for low-virulence organisms, improving interpretation of intraoperative frozen sections, and establishing improved synovial fluid and peripheral serum biomarker profiles for periprosthetic joint infection.

Predictive Modeling and Inflammatory Biomarkers in Rats With Lung Contusion and Gastric Aspiration

BACKGROUND This study uses statistical predictive modeling and hierarchical cluster analyses to examine inflammatory mediators and cells in bronchoalveolar lavage (BAL) as putative biomarkers in rats with blunt trauma lung contusion (LC), gastric aspiration (combined acid and small gastric food particles, CASP), or a combination of the two. METHODS Specific parameters assessed in the innate pulmonary inflammatory response were leukocytes, macrophages, and polymorphonuclear neutrophils (PMNs) in BAL; whole lung myeloperoxidase activity; and a series of cytokines or chemokines present in BAL at 5 or 24 hours after injury: tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, interferon-gamma, IL-10, macrophage inflammatory protein-2, cytokine-induced neutrophil chemoattractant-1, and monocyte chemoattractant protein-1. RESULTS Rats with LC, CASP, LC + CASP all had severe lung injury compared with uninjured controls based on decreased arterial oxygenation or increased BAL albumin at 5 or 24 hours postinsult. However, the injury groups had distinct overall patterns of inflammation that allowed them to be discriminated accurately by hierarchical cluster analysis (29 of 30 and 35 of 37 rats were correctly classified in hierarchical clusters at 5 and 24 hours, respectively). Moreover, predictive analyses based on an extension of standard receiver-operator characteristic methodology discriminated individual animals and groups with similar high accuracy based on a maximum of two inflammatory parameters per group (29 of 30 and 36 of 37 rats were correctly classified at 5 hours and 24 hours, respectively). CONCLUSIONS These results support the possibility that inflammatory biomarker profiles could be developed in the future to improve the diagnosis and management of trauma patients with unwitnessed (occult) gastric aspiration who have an increased risk of clinical acute lung injury or the acute respiratory distress syndrome.

MRI, Retrieval Analysis, and Histologic Evaluation of Adverse Local Tissue Reaction in Metal-on-Polyethylene Total Hip Arthroplasty

BACKGROUND The severity and location of adverse local tissue reaction (ALTR) seen in metal-on-polyethylene total hip arthroplasty (THA) is not well described. METHODS We retrospectively reviewed the records of patients who underwent a revision THA using our biomechanics database. We included all patients who underwent revision surgery for the diagnosis of ALTR with THA implants that had modularity solely at the head-neck junction and excluded patients with implant modularity at sites other than the head-neck junction. Magnetic resonance imaging (MRI) was evaluated by a fellowship-trained radiologist who specializes in evaluating metal artifact reducing MRI sequences to quantify the ALTR lesions. Histology was evaluated for findings of ALTR using the Campbell score. RESULTS We identified 11 patients in the database. Eight patients had an MRI ALTR grade of severe and 7 did based on the histology score. The mean synovial volume was 218,658 mm3 (range 23,461-451,435 mm3) with a mean maximal synovial thickness of 15.3 mm (range 3-34.3 mm). A disruptive infiltration of the abductors due to pseudocapsule invasion was seen in 67% of the patients with 3 not having abductor involvement. Mean preoperative cobalt and chromium levels were 5.4 ppb (range 1-12.3 ppb) and 1.1 ppb (range 0.6-2.4 ppb), respectively. CONCLUSION Patients with ALTR from head-neck junction corrosion in metal-on-polyethylene THA may present with large pseudotumors that have previously been under appreciated. Mean preoperative serum cobalt and chromium ion levels remained relatively low, and MRI was an effective way to characterize the size and location of these lesions.

Polypropylene mesh augmentation for complete quadriceps rupture after total knee arthroplasty.

INTRODUCTION Polypropylene mesh has previously been shown to be an effective treatment for failed patellar tendon repairs after total knee arthroplasty (TKA), but there have been few reports of this synthetic mesh used in complete quadriceps rupture after TKA. METHODS We retrospectively reviewed seven consecutive cases in six patients with complete quadriceps tears after TKA who had their quadriceps tendon repaired with suture and polypropylene mesh augmentation. All but two patients had previously failed primary suture repair. Patient outcomes were evaluated using the Knee Society Score. Standardized anterior-posterior (AP), lateral and merchant radiographs were evaluated preoperatively and at final follow-up. RESULTS Seven knees in six patients were evaluated with a mean follow-up of 34±10 (range 24 to 49months) months. There were only four clinical successes defined as an extensor lag less than 30°. Of the functioning knees at final follow-up (n=5) the overall extensor lag in this group did significantly improve from 50±13° to 20±15° (range 5 to 40°) (p=.01). Mean postoperative flexion at final follow-up was 115±8°. Mean Knee Society Score for function improved from 20±30 to 45±54 (p=.03) as did the mean Knee Society Score for pain (44±18 vs. 74±78, p=.02). DISCUSSION Polypropylene mesh offered limited postoperative functional results when used as an augment to the multiply operated knee that sustains a complete quadriceps rupture after TKA, but did allow for significant improvement in postoperative pain outcomes. LEVEL OF EVIDENCE IV.

Short Term Outcomes of a Hydroxyapatite Coated Metal Backed Patella

We retrospectively evaluated the records and radiographs of 101 knees with a hydroxyapatite coated metal backed patella (HAP) and 50 knees with a cemented polyethylene patella (CP) with minimum two year clinical follow up. There were no patellar revisions during the study period. Patients in both the HAP and CP groups had similar clinical outcomes at final follow-up. Forty-five percent of patients in the HAP group had 1-2mm areas of decreased trabecular bone density around the pegs, which were not observed in the CP group, and may represent stress shielding. This uncemented HAP component has satisfactory early clinical outcomes, but long-term follow up is necessary to determine the durability of this implant.

Success rates, characteristics, and costs of articulating antibiotic spacers for total knee periprosthetic joint infection

BACKGROUND The optimal type, characteristics, and success rates of articulating antibiotic spacers used during total knee arthroplasty (TKA) periprosthetic joint infection (PJI) have not been well defined in a single series. We sought to (1) determine the success rate for three unique spacer constructs and (2) evaluate any microbiological, surgical, or patient characteristics that would influence the success rate. METHODS We retrospectively reviewed patients who underwent a two-stage exchange for a TKA PJI with a prefabricated spacer (PREFAB), home-made mold (MOLD), or autoclaved femoral component (AUTOCL). Patient demographics, microbiology data, amount of antibiotic in each spacer construct, postoperative course, and infection cure outcomes were evaluated. RESULTS The success rate for being infection free at final follow-up without the need for further reoperation for infection was 82.7% in the PREFAB group, 88.4% in the MOLD group, and 79.4% in the AUTOCL group (p=0.54). There was no clear statistical link between raw quantities of vancomycin and aminoglycoside in the spacer and a successful outcome. The surgeons own intraoperatively created mold group had the lowest construct cost at a mean