Extended Release of Bupivacaine from Temperature-responsive Hydrogels Provides Multi-day Analgesia for Postoperative Pain.

OBJECTIVE: A local anesthetic that provides analgesia lasting at least three days could significantly improve postoperative pain management. This study evaluated the analgesic efficacy and safety of an extended-release formulation of bupivacaine based on the injectable hydrogel carrier poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylamide-co-Jeffamine M-1000 acrylamide) (PNDJ). METHODS: The efficacy of PNDJ containing 4% bupivacaine (SBG004) given by peri-incisional subcutaneous injection (SBG004 SC) or wound filling instillation (SBG004 WF) was evaluated compared to saline, liposomal bupivacaine, bupivacaine collagen sponge, bupivacaine-meloxicam polyorthoester, and bupivacaine HCl in a porcine skin and muscle incision model. Mechanical allodynia was assessed by withdrawal from application of von Frey filaments, and local tolerance was evaluated by histology. Bupivacaine pharmacokinetics for SBG004 SC were measured in rabbits (16.5 mg bupivacaine/kg). RESULTS: Animals demonstrated less mechanical allodynia at incisions receiving SBG004 SC for up to 96 hours postoperatively. Incisions treated with SBG004 SC tolerated more force without a withdrawal indicative of pain compared to saline for 96 hours, and compared to SBG004 WF and all active controls at 24, 48, and 72 hours except bupivacaine-meloxicam polyorthoester at 72 hours. By 49 days, SBG004 was histologically absent and was replaced with granulation tissue infiltrated with immune cells in some areas. In rabbits, Cmax was 41.6 ± 9.7 ng/mL with t1/2 82.0 ± 35.8 hours (mean ± SD). CONCLUSIONS: Peri-incisional SBG004 SC provided extended release of bupivacaine sufficient to reduce sensation of incisional pain for 96 hours, in vivo bupivacaine delivery for at least 7 days, and a favorable local and systemic toxicity profile.

Mortality Rate Increase in Elderly Patients With Hip Fractures Presenting During the COVID-19 Pandemic to a Hospital in the United States Epicenter: Minimum 30-day Follow Up Comparative Study.

The purpose of this study was to compare mortality and complication rates among geriatric patients who sustained a hip fracture before the coronavirus disease (COVID-19) pandemic began to those who presented during the peak of the pandemic. Patients greater than or equal to 50 years of age who presented with a diagnosis of hip fracture from March 16, 2020 to May 1, 2020 were compared with a historical control group who presented between December 1, 2019 and January 16, 2020. Minimum follow up was 30 days. The primary outcome was a 30-day mortality rate. Thirty-day mortality was significantly different between groups, with no deaths of 24 patients in the pre-COVID-19 cohort versus six deaths of 23 patients (26.1%) in the COVID-19 cohort (chi-squared test, p-value = 0.02). The study concluded that the COVID-19 pandemic increased mortality risk for geriatric hip fracture patients. (Journal of Surgical Orthopaedic Advances 32(4):232-237, 2023).

Rotator Cuff Repair With Acromioplasty Is Associated With an Increased Rate of Revision and Subsequent Procedures.

Purpose: To evaluate the mid-term rate of revision arthroscopic rotator cuff repair as well as ipsilateral shoulder reoperations after index rotator cuff repair performed with or without acromioplasty in the United States. Methods: The Medicare Standard Analytic File, which encompasses the entire Medicare billing and payment data, was queried between 2005 and 2014. Patients undergoing arthroscopic rotator cuff repair were identified and stratified based on whether ipsilateral acromioplasty was concurrently performed using Current Procedural Terminology codes. Groups were matched by age, sex, year of index procedure, and Elixhauser index at a 2:1 ratio. Primary end point was defined as undergoing a repeat ipsilateral shoulder surgery related to the rotator cuff at 5 years of follow-up. Kaplan-Meier survival curves were constructed, and the 2 groups were compared using the log-rank test. Results: After matching, 54,209 shoulders in the rotator cuff repair with acromioplasty group and 26,448 shoulders in the rotator cuff repair without acromioplasty group were identified. Shoulders undergoing concurrent acromioplasty at index rotator cuff repair had a significantly increased rate of repeat ipsilateral cuff repair at 5 years postoperatively (8.5% vs 6.8%, P < .001). Similarly, there was an increased rate of reoperation of all types to the ipsilateral shoulder in cases where concurrent acromioplasty was performed (9.6% vs 9.1%, P < .001). Conclusions: Using a large, national database, concurrent acromioplasty at the time of rotator cuff tear was found to be associated with both an increase rate of overall subsequent procedures and revision rotator cuff repair. Level of Evidence: III, retrospective comparative study.

Incidental Pulmonary Nodules Found on Shoulder Arthroplasty Preoperative CT Scans.

With current emphasis on preoperative templating of anatomical and reverse shoulder arthroplasty (aTSA and rTSA, respectively), patients often receive thin slice (<1.0 mm) computerized tomography (CT) scans of the operative shoulder, which includes about two-thirds of the ipsilateral lung. The purpose of this study is to evaluate the prevalence and management of incidentally detected pulmonary nodules on preoperative CT scans for shoulder arthroplasty. In this single-center retrospective study, we queried records of aTSA and rTSA patients from 2015 to 2020 who received preoperative CT imaging of the shoulder. Compared to patients with negative CT findings, there were significantly more females (63.8% vs. 46.4%; P = .011), COPD (13.0% vs. 4.7%; P = .015), and asthma (18.8% vs. 6.9%; P = .003) among the patients with incidental nodules on CT. Binary logistic regression confirmed that female sex (odds ratio = 2.00; 95% CI = 1.04 to 3.88; P = .037), COPD history (OR = 3.02; 95% CI = 1.05 to 8.65; P = .040), and asthma history (OR = 3.17; 95% CI = 1.30 to 7.77; P = .011) were significantly associated with an incidental nodule finding. Incidental pulmonary nodules found on shoulder arthroplasty preoperative CT scans are often low risk in size with low risk of malignancy, and do not require further workup. This study may provide guidance to orthopedic surgeons on how to manage patients with incidental pulmonary nodules to increase chances of early cancer detection, avoid unnecessary referrals, reduce potentially harmful radiation exposure of serial CT scans, and improve cost efficiency.

Local antimicrobial delivery from temperature-responsive hydrogels reduces incidence of intra-abdominal infection in rats.

The objective of this study was to evaluate local antimicrobial delivery from temperature-responsive hydrogels for preventing infection in a rat model of intra-abdominal infection (IAI), and to determine whether delivery of tobramycin and vancomycin in combination is effective against IAI pathogens. Rats received intraperitoneal inoculation of E. coli, rat cecal contents, or cecal contents supplemented with E. coli, and received either no treatment, subcutaneous cefoxitin, or local delivery from hydrogels containing vancomycin, tobramycin, or both antimicrobials. Only the hydrogel with tobramycin and vancomycin significantly increased the infection free-rate compared to no treatment for all inocula (E. coli: 13/17, p < 0.0001; cecal contents: 11/17, p = 0.0013; cecal contents + E. coli: 15/19, p < 0.0001). Additionally, tobramycin and vancomycin displayed no synergy or antagonism against clinical isolates in vitro. Local delivery of tobramycin and vancomycin from temperature-responsive hydrogels provides broad coverage and high antimicrobial concentrations for several hours that may be effective for preventing IAIs.

PNJ scaffolds promote microenvironmental regulation of glioblastoma stem-like cell enrichment and radioresistance.

Glioblastoma (GBM) brain tumors contain a subpopulation of self-renewing multipotent Glioblastoma stem-like cells (GSCs) that are believed to drive the near inevitable recurrence of GBM. We previously engineered temperature responsive scaffolds based on the polymer poly(N-isopropylacrylamide-co-Jeffamine M-1000 acrylamide) (PNJ) for the purpose of enriching GSCs in vitro from patient-derived samples. Here, we used PNJ scaffolds to study microenvironmental regulation of self-renewal and radiation response in patient-derived GSCs representing classical and proneural subtypes. GSC self-renewal was regulated by the composition of PNJ scaffolds and varied with cell type. PNJ scaffolds protected against radiation-induced cell death, particularly in conditions that also promoted GSC self-renewal. Additionally, cells cultured in PNJ scaffolds exhibited increased expression of the transcription factor HIF2α, which was not observed in neurosphere culture, providing a potential mechanistic basis for differences in radio-resistance. Differences in PNJ regulation of HIF2α in irradiated and untreated conditions also offered evidence of stem plasticity. These data show PNJ scaffolds provide a unique biomaterial for evaluating dynamic microenvironmental regulation of GSC self-renewal, radioresistance, and stem plasticity.

In vivo evaluation of temperature-responsive antimicrobial-loaded PNIPAAm hydrogels for prevention of surgical site infection.

Surgical site infections (SSIs) are a persistent clinical challenge. Local antimicrobial delivery may reduce the risk of SSI by increasing drug concentrations and distribution in vulnerable surgical sites compared to what is achieved using systemic antimicrobial prophylaxis alone. In this work, we describe a comprehensive in vivo evaluation of the safety and efficacy of poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylamide-co-Jeffamine M-1000 acrylamide) [PNDJ], an injectable temperature-responsive hydrogel carrier for antimicrobial delivery in surgical sites. Biodistribution data indicate that PNDJ is primarily cleared via the liver and kidneys following drug delivery. Antimicrobial-loaded PNDJ was generally well-tolerated locally and systemically when applied in bone, muscle, articulating joints, and intraperitoneal space, although mild renal toxicity consistent with the released antimicrobials was identified at high doses in rats. Dosing of PNDJ at bone-implant interfaces did not affect normal tissue healing and function of orthopedic implants in a transcortical plug model in rabbits and in canine total hip arthroplasty. Finally, PNDJ was effective at preventing recurrence of implant-associated MSSA and MRSA osteomyelitis in rabbits, showing a trend toward outperforming commercially available antimicrobial-loaded bone cement and systemic antimicrobial administration. These studies indicate that antimicrobial-loaded PNDJ hydrogels are well-tolerated and could reduce incidence of SSI in a variety of surgical procedures.

Medial Ulnar Collateral Ligament Repair With Internal Brace Augmentation: Results in 40 Consecutive Patients.

BACKGROUND: Medial ulnar collateral ligament (MUCL) repair has been proven to be effective in nonprofessional overhead-throwing athletes, with faster and higher rates of return to play (RTP) than the more traditional Tommy John reconstruction. Biomechanical studies and clinical data suggest that MUCL repair augmented with a collagen-coated internal brace may be an effective treatment option in this patient population. PURPOSE: To evaluate the functional outcomes of young nonprofessional athletes who underwent MUCL repair with internal brace augmentation for medial elbow instability. The hypothesis was that these patients will have high rates of RTP and improved functional outcomes. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Nonprofessional overhead athletes treated with MUCL repair with internal brace augmentation between 2015 and 2017 were prospectively evaluated for a minimum of 1 year. Preoperatively, all patients had evidence of medial elbow pain caused by MUCL insufficiency, as confirmed by signal changes on magnetic resonance imaging and valgus instability on arthroscopic examination. These findings did not allow them to participate in their chosen sport or profession, and each patient had failed nonoperative treatment. Postoperative outcomes were evaluated using the Overhead Athlete Shoulder and Elbow Score of the Kerlan-Jobe Orthopaedic Clinic. Complications were recorded and detailed. RESULTS: A total of 40 nonprofessional overhead athletes were included in this study (35 men and 5 women; mean age, 17.8 years [range, 14-28 years]). The mean follow-up time was 23.8 months (range, 12-44 months). The mean postoperative Kerlan-Jobe Orthopaedic Clinic score was 92.6 (range, 64-100). Overall, 37 athletes (92.5%) returned to play or profession at the same level or higher at a mean time of 6.9 months (range, 2-12 months). Three patients did not RTP: 1 was limited by a concomitant medical diagnosis, and the other 2 chose not to resume athletics after the procedure but remained symptom free. CONCLUSION: In the nonprofessional athlete, primary MUCL repair with internal brace augmentation is a viable alternative to traditional repair techniques or reconstruction, allowing for a rapid RTP and promising functional outcomes.

Using machine learning methods to predict nonhome discharge after elective total shoulder arthroplasty.

BACKGROUND: Machine learning has shown potential in accurately predicting outcomes after orthopedic surgery, thereby allowing for improved patient selection, risk stratification, and preoperative planning. This study sought to develop machine learning models to predict nonhome discharge after total shoulder arthroplasty (TSA). METHODS: The American College of Surgeons National Surgical Quality Improvement Program database was queried for patients who underwent elective TSA from 2012 to 2018. Boosted decision tree and artificial neural networks (ANN) machine learning models were developed to predict non-home discharge and 30-day postoperative complications. Model performance was measured using the area under the receiver operating characteristic curve (AUC) and overall accuracy (%). Multivariate binary logistic regression analyses were used to identify variables that were significantly associated with the predicted outcomes. RESULTS: There were 21,544 elective TSA cases identified in the National Surgical Quality Improvement Program registry from 2012 to 2018 that met inclusion criteria. Multivariate logistic regression identified several variables associated with increased risk of nonhome discharge including female sex (odds ratio [OR] = 2.83; 95% confidence interval [CI] = 2.53-3.17; P < .001), age older than 70 years (OR = 3.19; 95% CI = 2.86-3.57; P < .001), American Society of Anesthesiologists classification 3 or greater (OR = 2.70; 95% CI = 2.41-2.03; P < .001), prolonged operative time (OR = 1.38; 95% CI = 1.20-1.58; P < .001), as well as history of diabetes (OR = 1.56; 95% CI = 1.38-1.75; P < .001), chronic obstructive pulmonary disease (OR = 1.71; 95% CI = 1.46-2.01; P < .001), congestive heart failure (OR = 2.65; 95% CI = 1.72-4.01; P < .001), hypertension (OR = 1.35; 95% CI = 1.20-1.52; P = .004), dialysis (OR = 3.58; 95% CI = 2.01-6.39; P = .002), wound infection (OR = 5.67; 95% CI = 3.46-9.29; P < .001), steroid use (OR = 1.43; 95% CI = 1.18-1.74; P = .010), and bleeding disorder (OR = 1.84; 95% CI = 1.45-2.34; P < .001). The boosted decision tree model for predicting nonhome discharge had an AUC of 0.788 and an overall accuracy of 90.3%. The ANN model for predicting nonhome discharge had an AUC of 0.851 and an overall accuracy of 89.9%. For predicting the occurrence of 1 or more postoperative complications, the boosted decision tree model had an AUC of 0.795 and an overall accuracy of 95.5%. The ANN model yielded an AUC of 0.788 and an overall accuracy of 92.5%. CONCLUSIONS: Both the boosted decision tree and ANN models performed well in predicting nonhome discharge with similar overall accuracy, but the ANN had higher discriminative ability. Based on the findings of this study, machine learning has the potential to accurately predict nonhome discharge after elective TSA. Surgeons can use such tools to guide patient expectations and to improve preoperative discharge planning, with the ultimate goal of decreasing hospital length of stay and improving cost-efficiency.

Association between shoulder coracoacromial arch morphology and anterior instability of the shoulder.

BACKGROUND: Glenohumeral instability is a common condition of the shoulder. Glenoid bone loss and humeral head bone loss are well recognized as risk factors for recurrent instability. There are few studies in the literature that examine the role of coracoacromial arch anatomy in the pathogenesis of glenohumeral instability. Previous reports found an association between posterior acromial coverage (PAC) and posterior instability. We hypothesize that coracoacromial arch anatomy is related to anterior shoulder instability. METHODS: In this retrospective cohort study, 50 patients with unidirectional anterior shoulder instability were matched to a control group of 50 glenohumeral arthritis patients without any history of shoulder instability. Radiographic measurements of the coracoacromial arch anatomy were made: shoulder arch angle, scapular Y angle, anterior coracoid tilt (ACT), posterior acromial tilt, anterior acromial coverage angle, PAC angle, coracoid height, posterior acromial height, and critical shoulder angle were determined using standard lateral scapular and anteroposterior radiographs. RESULTS: Logistic regression analyses found a significant association between the presence of anterior instability and flatter coracoacromial arch angles (mean, 124.1°) vs. the arthritis control group (mean, 120.6°) (odds ratios [OR] = 1.113; 95% confidence interval [CI] = 1.039-1.191; P = .002). There was a significant association between anterior instability and ACT (OR = 1.144; 95% CI = 1.053-1.243; P = .001), whereas a negative association was found between anterior instability and PAC (OR = 0.909; 95% CI = 0.853-0.969; P = .004) and posterior acromial tilt (OR = 0.878; 95% CI = 0.773-0.998; P = .046). Lower critical shoulder angle values were associated with the arthritis group (28.2° vs. 33.9°) (OR = 1.555; 95% CI = 1.202-2.012; P = .001). CONCLUSIONS: Shoulder coracoacromial arch morphology may play a role in the stability of the shoulder joint and development of recurrent anterior instability. Shoulders with a decreased shoulder arch angle, a less contained and flatter coracoacromial arch and larger ACT, were associated with anterior instability. This study identifies the shoulder coracoacromial arch angle and anterior coracoid tile angles as risk factors for anterior shoulder instability. Our findings suggest that measuring these angles may help orthopedic surgeons understand the risk of anterior instability and analyze risk factors to improve clinical decision making.

Replacing Barley and Soybean Meal With By-products, in a Pasture Based Diet, Alters Daily Methane Output and the Rumen Microbial Community in vitro Using the Rumen Simulation Technique (RUSITEC).

Plant based by-products (BP) produced from food and bioethanol industries are human inedible, but can be recycled into the global food chain by ruminant livestock. However, limited data is available on the methanogenesis potential associated with supplementing a solely BP formulated concentrate to a pastoral based diet. Therefore the objective of this in vitro study was to investigate the effects of BP inclusion rate (in a formulated concentrate) to a pasture based diet on dietary digestibility, rumen fermentation patterns, methane production and the prokaryotic microbial community composition. Diets consisted of perennial ryegrass and one of two supplementary concentrates, formulated to be isonitrogenous (16% CP) and isoenergetic (12.0 MJ/ME/kg), containing either 35% BP, barley and soybean meal (BP35) or 95% BP (BP95) offered on a 50:50 basis, however, starch, NDF and fat content varied. The BPs, included in equal proportions on a DM basis, were soyhulls, palm kernel expeller and maize dried distillers grains. The BP35 diet had greater (P < 0.05) digestibility of the chemical constituents DM, OM, CP, NDF, ADF. Greater total VFA production was seen in the BP35 diet (P < 0.05). Daily methane production (mmol/day; +22.7%) and methane output per unit of total organic matter digested (MPOMD; +20.8%) were greatest in the BP35 diet (P < 0.01). Dietary treatment influenced microbial composition (PERMANOVA; P = 0.023) with a greater relative abundance of Firmicutes (adj P < 0.01) observed in the BP35. The Firmicutes:Bacteroidetes ratio was significantly reduced in the BP95 diet (P < 0.01). The relative proportions of Proteobacteria (adj P < 0.01), Succinivibrionaceae (adj P < 0.03) and Succinivibrio (adj P = 0.053) increased in the BP95 diet. The abundance of Proteobacteria was found to be negatively associated with daily methane production (rs, -0.71; P < 0.01) and MPOMD (rs, -0.65; P < 0.01). Within Proteobacteria, the relationship of methane production was maintained with the mean abundance of Succinivibrio (rs, -0.69; P < 0.01). The abundance of the Firmicutes phyla was found to be positively correlated with both daily methane production (rs, 0.79; P < 0.001) and MPOMD (rs, 0.75; P < 0.01). Based on in vitro rumen simulation data, supplementation of an exclusively BP formulated concentrate was shown to reduce daily methane output by promoting a favorable alteration to the rumen prokaryotic community.

Complete 180-Degree Dislocation of a Rotating Platform after Closed Reduction for Mobile Bearing Spinout.

Rotating-platform total knee arthroplasty was designed to help decrease backside polyethylene wear and allow maximal conformity between the femoral and tibial components, but there have been multiple reports of dislocation and spinout of these implants. There are 4 case reports in the literature of knee dislocations with 180° rotation of the platform, 3 of which occurred during relocation attempts. This is only the second case in a posterior-stabilized mobile-bearing device. We present a case of complete 180° dislocation of a rotating platform after closed reduction in a posterior-stabilized total knee arthroplasty, with subsequent conversion to hinge knee arthroplasty.

Double Row-Equivalent PASTA Repair Technique.

Articular surface partial rotator cuff tendon tears are a common source of shoulder pain and dysfunction, and there is no consensus regarding the optimal arthroscopic treatment. Commonly accepted techniques, such as transtendinous repair or tear takedown with primary repair, may violate healthy tendon tissue and increase the suture anchor density. In this note, we describe an outside-in double row-equivalent technique for repair of partial articular-sided rotator cuff tears. A medial row of inverted horizontal mattress stitches is placed percutaneously using spinal needles to shuttle partially absorbable braided sutures into the joint. The technique may incorporate a soft tissue biceps tenodesis into the rotator cuff with a second, oblique medial row mattress stitch. Suture limbs are retrieved and tied in the subacromial space and then secured to a lateral anchor. The result is a side-to-side double row-equivalent rotator cuff repair, anatomically reproducing the footprint of the rotator cuff without removing healthy tissue. We believe this is an efficient and reproducible technique that preserves intact bursal tissue, limits implant costs, and produces reliable healing in partial articular-sided tears of the rotator cuff.

Temperature-responsive PNDJ hydrogels provide high and sustained antimicrobial concentrations in surgical sites.

Local antimicrobial delivery is a promising strategy for improving treatment of deep surgical site infections (SSIs) by eradicating bacteria that remain in the wound or around its margins after surgical debridement. Eradication of biofilm bacteria can require sustained exposure to high antimicrobial concentrations (we estimate 100-1000 µg/mL sustained for 24 h) which are far in excess of what can be provided by systemic administration. We have previously reported the development of temperature-responsive hydrogels based on poly(N-isopropylacrylamide-co-dimethylbutyrolactone acrylate-co-Jeffamine M-1000 acrylamide) (PNDJ) that provide sustained antimicrobial release in vitro and are effective in treating a rabbit model of osteomyelitis when instilled after surgical debridement. In this work, we sought to measure in vivo antimicrobial release from PNDJ hydrogels and the antimicrobial concentrations provided in adjacent tissues. PNDJ hydrogels containing tobramycin and vancomycin were administered in four dosing sites in rabbits (intramedullary in the femoral canal, soft tissue defect in the quadriceps, intramuscular injection in the hamstrings, and intra-articular injection in the knee). Gel and tissue were collected up to 72 h after dosing and drug levels were analyzed. In vivo antimicrobial release (43-95% after 72 h) was markedly faster than in vitro release. Drug levels varied significantly depending on the dosing site but not between polymer formulations tested. Notably, total antimicrobial concentrations in adjacent tissue in all dosing sites were sustained at estimated biofilm-eradicating levels for at least 24 h (461-3161 µg/mL at 24 h). These results suggest that antimicrobial-loaded PNDJ hydrogels are promising for improving the treatment of biofilm-based SSIs.

Determination of Tobramycin and Vancomycin Exposure Required to Eradicate Biofilms on Muscle and Bone Tissue In Vitro.

Background: Bacterial biofilms cause chronic orthopaedic infections. Surgical debridement to remove biofilm can be ineffective without adjuvant local antimicrobials because undetected biofilm fragments may remain in the wound and reestablish the infection if untreated. However, the concentrations and duration of antimicrobial exposure necessary to eradicate bacteria from clinical biofilms remain largely undefined. In this study, we determined the minimum biofilm eradication concentration (MBEC) of tobramycin and vancomycin for bacterial biofilms grown on bone and muscle in vitro. Methods: Biofilms of pathogens found in musculoskeletal infections (S. aureus, S. epidermidis, E. faecalis, P. aeruginosa, and E. coli) were established for 72 hr on rabbit muscle and bone specimens in vitro and characterized by SEM imaging and CFU counts. Biofilm-covered tissue specimens were exposed to serial log2 dilutions (4000-31.25 µg/mL) of tobramycin, vancomycin, or a 1:1 combination of both drugs for 6, 24, or 72 hr. Tissues were subcultured following antimicrobial exposure to determine bacterial survival. The breakpoint concentration with no surviving bacteria was defined as the MBEC for each pathogen-antimicrobial-exposure time combination. Results: All tested pathogens formed biofilm on tissue. Tobramycin/vancomycin (1:1) was the most effective antimicrobial regimen with MBEC on muscle (10/10 pathogens) or bone (7/10 pathogens) generally in the range of 100-750 µg/mL with 24 or 72 hr exposure. MBEC decreased with exposure time for 53.3% of biofilms between 6 and 24 hr, 53.3% of biofilms between 24 and 72 hr, and for 76.7% of biofilms between 6 and 72 hr. MBECs on bone were significantly higher than corresponding MBECs on muscle tissue (p < 0.05). In most cases, tissue MBECs were lower compared to previously published MBECs for the same pathogens on polystyrene tissue-culture plates. Conclusions: The majority of MBECs for orthopaedic infections on bone and muscle are on the order of 100-750 µg/mL of vancomycin+tobramycin when sustained for at least 24 hr, which may be clinically achievable using high-dose antimicrobial-loaded bone cement (ALBC).

Comparison of Time and Cost Savings Using Different Cost Methodologies for Patient-Specific Instrumentation vs Standard Referencing in Total Ankle Arthroplasty.

BACKGROUND: Patient-specific 3-D printing cutting blocks (PSI) have been used instead of traditional intramedullary cutting guides. We hypothesized that PSI would lead to significantly decreased operating room (OR) time and significant cost savings to our institution with noninferior radiographic outcomes and no difference in expected vs actual implant size when compared with standard referencing (SR). METHODS: Patients who had undergone total ankle replacements at our institution from 2013 through 2016 were included in the study. Associations between demographic variables and postoperative alignment in the SR vs PSI group were calculated using the Wilcoxon rank-sum test and the intraclass correlation coefficient. The cost of the operation was calculated using both an institutionally based fixed cost of OR time and using Time Driven Activity Based Cost (TDABC) accounting. A total of 43 patients were included in the study, 13 in the SR group and 30 in the PSI group. RESULTS: Operative time (168 vs 137 minutes) and tourniquet time (123 vs 113 minutes) were significantly lower in the PSI vs the SR group. PSI predictions were accurate 100% of the time for tibial components and 83% of the time for talar components. Average costs of TAA using PSI were significantly reduced by $7597.00 when using traditional OR accounting, whereas PSI was $836.00 more expensive on average using TDABC accounting. CONCLUSION: Further research is needed to determine the cost-effectiveness of PSI vs SR in TAA; however, it does appear to save time intraoperatively. The long-term effect on clinical outcomes requires further study. LEVEL OF EVIDENCE: Level III, case-control study.

PNIPAAm-co-Jeffamine® (PNJ) scaffolds as in vitro models for niche enrichment of glioblastoma stem-like cells.

Glioblastoma (GBM) is the most common adult primary brain tumor, and the 5-year survival rate is less than 5%. GBM malignancy is driven in part by a population of GBM stem-like cells (GSCs) that exhibit indefinite self-renewal capacity, multipotent differentiation, expression of neural stem cell markers, and resistance to conventional treatments. GSCs are enriched in specialized niche microenvironments that regulate stem phenotypes and support GSC radioresistance. Therefore, identifying GSC-niche interactions that regulate stem phenotypes may present a unique target for disrupting the maintenance and persistence of this treatment resistant population. In this work, we engineered 3D scaffolds from temperature responsive poly(N-isopropylacrylamide-co-Jeffamine M-1000® acrylamide), or PNJ copolymers, as a platform for enriching stem-specific phenotypes in two molecularly distinct human patient-derived GSC cell lines. Notably, we observed that, compared to conventional neurosphere cultures, PNJ cultured GSCs maintained multipotency and exhibited enhanced self-renewal capacity. Concurrent increases in expression of proteins known to regulate self-renewal, invasion, and stem maintenance in GSCs (NESTIN, EGFR, CD44) suggest that PNJ scaffolds effectively enrich the GSC population. We further observed that PNJ cultured GSCs exhibited increased resistance to radiation treatment compared to GSCs cultured in standard neurosphere conditions. GSC radioresistance is supported in vivo by niche microenvironments, and this remains a significant barrier to effectively treating these highly tumorigenic cells. Taken in sum, these data indicate that the microenvironment created by synthetic PNJ scaffolds models niche enrichment of GSCs in patient-derived GBM cell lines, and presents tissue engineering opportunities for studying clinically important behaviors such as radioresistance in vitro.

Optical barcoding of PLGA for multispectral analysis of nanoparticle fate in vivo.

Understanding of the mechanisms by which systemically administered nanoparticles achieve delivery across biological barriers remains incomplete, due in part to the challenge of tracking nanoparticle fate in the body. Here, we develop a new approach for "barcoding" nanoparticles composed of poly(lactic-co-glycolic acid) (PLGA) with bright, spectrally defined quantum dots (QDs) to enable direct, fluorescent detection of nanoparticle fate with subcellular resolution. We show that QD labeling does not affect major biophysical properties of nanoparticles or their interaction with cells and tissues. Live cell imaging enabled simultaneous visualization of the interaction of control and targeted nanoparticles with bEnd.3 cells in a flow chamber, providing direct evidence that surface modification of nanoparticles with the cell-penetrating peptide TAT increases their biophysical association with cell surfaces over very short time periods under convective current. We next developed this technique for quantitative biodistribution analysis in vivo. These studies demonstrate that nanoparticle surface modification with the cell penetrating peptide TAT facilitates brain-specific delivery that is restricted to brain vasculature. Although nanoparticle entry into the healthy brain parenchyma is minimal, with no evidence for movement of nanoparticles across the blood-brain barrier (BBB), we observed that nanoparticles are able to enter to the central nervous system (CNS) through regions of altered BBB permeability - for example, into circumventricular organs in the brain or leaky vasculature of late-stage intracranial tumors. In sum, these data demonstrate a new, multispectral approach for barcoding PLGA, which enables simultaneous, quantitative analysis of the fate of multiple nanoparticle formulations in vivo.

PNIPAAm-based biohybrid injectable hydrogel for cardiac tissue engineering.

Injectable biomaterials offer a non-invasive approach to deliver cells into the myocardial infarct region to maintain a high level of cell retention and viability and initiate the regeneration process. However, previously developed injectable matrices often suffer from low bioactivity or poor mechanical properties. To address this need, we introduced a biohybrid temperature-responsive poly(N-isopropylacrylamide) PNIPAAm-Gelatin-based injectable hydrogel with excellent bioactivity as well as mechanical robustness for cardiac tissue engineering. A unique feature of our work was that we performed extensive in vitro biological analyses to assess the functionalities of cardiomyocytes (CMs) alone and in co-culture with cardiac fibroblasts (CFs) (2:1 ratio) within the hydrogel matrix. The synthesized hydrogel exhibited viscoelastic behavior (storage modulus: 1260 Pa) and necessary water content (75%) to properly accommodate the cardiac cells. The encapsulated cells demonstrated a high level of cell survival (90% for co-culture condition, day 7) and spreading throughout the hydrogel matrix in both culture conditions. A dense network of stained F-actin fibers (∼ 6 × 10(4) µm(2) area coverage, co-culture condition) illustrated the formation of an intact and three dimensional (3D) cell-embedded matrix. Furthermore, immunostaining and gene expression analyses revealed mature phenotypic characteristics of cardiac cells. Notably, the co-culture group exhibited superior structural organization and cell-cell coupling, as well as beating behavior (average ∼ 45 beats per min, co-culture condition, day 7). The outcome of this study is envisioned to open a new avenue for extensive in vitro characterization of injectable matrices embedded with 3D mono- and co-culture of cardiac cells prior to in vivo experiments. STATEMENT OF SIGNIFICANCE: In this work, we synthesized a new class of biohybrid temperature-responsive poly(N-isopropylacrylamide) PNIPAAm-Gelatin-based injectable hydrogel with suitable bioactivity and mechanical properties for cardiac tissue engineering. A significant aspect of our work was that we performed extensive in vitro biological analyses to assess the functionality of cardiomyocytes alone and in co-culture with cardiac fibroblasts encapsulated within the 3D hydrogel matrix.

Temperature responsive hydrogels enable transient three-dimensional tumor cultures via rapid cell recovery.

Recovery of live cells from three-dimensional (3D) culture would improve analysis of cell behaviors in tissue engineered microenvironments. In this work, we developed a temperature responsive hydrogel to enable transient 3D culture of human glioblastoma (GBM) cells. N-isopropylacrylamide was copolymerized with hydrophilic grafts and functionalized with the cell adhesion peptide RGD to yield the novel copolymer poly(N-isopropylacrylamide-co-Jeffamine(®) M-1000 acrylamide-co-hydroxyethylmethacrylate-RGD), or PNJ-RGD. This copolymer reversibly gels in aqueous solutions when heated under normal cell culture conditions (37°C). Moreover, these gels redissolve within 70 s when cooled to room temperature without the addition of any agents to degrade the synthetic scaffold, thereby enabling rapid recollection of viable cells after 3D culture. We tested the efficiency of cell recovery following extended 3D culture and were able to recover more than 50% of viable GBM cells after up to 7 days in culture. These data demonstrate the utility of physically crosslinked PNJ-RGD hydrogels as a platform for culture and recollection of cells in 3D.