Incidence of Nonunion of the First Metatarsophalangeal Joint Arthrodesis After Failed Implant Arthroplasty: A Systematic Review

Joint arthroplasty of the first metatarsophalangeal (MTP) joint is an accepted surgical option for patients with hallux rigidus. However, this procedure has been reported to have a high complication rate and unpredictable survivorship. Implant arthroplasty failure is a devastating complication that results in significant osseous defect with altered biomechanics of the foot. Commonly, salvage options are limited to arthrodesis with bone grafting. However, outcomes are rarely reported. The purpose of this study is to investigate the fusion rates of first metatarsophalangeal joint arthrodesis after conversion from failed implant arthroplasty. A systematic review of electronic databases to find reports of conversion arthrodesis after failed implant arthroplasty was performed. Six studies involving a total of 76 patients with a weighted mean age of 54.9 met the inclusion criteria. Out of the 6 included articles, the nonunion rate was 16.5% at a weighted mean follow-up of 48.1 months. The nonunion rate in the current report is higher than reported nonunion rates of primary arthrodesis. More prospective studies with consistent and standard outcome measures are needed to further determine the success rate of this salvage procedure.Levels of Evidence: 4, Systematic Review of Level 4 Studies.

The Cost-Effectiveness of Smoking Cessation Programs for Prevention of Wound Complications Following Total Ankle Arthroplasty: A Break-Even Analysis

Background

Tobacco use significantly increases the rate of wound complications in patients undergoing total ankle arthroplasty (TAA). Preoperative optimization through smoking cessation programs significantly minimizes the rate of infection and improves wound healing in arthroplasty procedures. Despite its utility, minimal research has examined the cost-effectiveness of preoperative smoking cessation programs to reduce the need for extracapsular irrigation and debridement (I&D) due to wound complications following TAA.

Methods

The cost of an I&D procedure was obtained from our institution's purchasing records. Baseline wound complication rates among tobacco users who have undergone TAA and smoking cessation program cost were obtained from literature. A break-even economic analysis was performed to determine the absolute risk reduction (ARR) to economically justify the implementation of preoperative smoking cessation programs. Different smoking cessation program and I&D costs were tested to account for variations in each factor. ARR was then used to calculate the number needed to treat (NNT) to prevent a single I&D while remaining cost-effective.

Results

Smoking cessation programs were determined to be economically justified if it prevents 1 I&D surgery out of 8 TAAs among tobacco users (ARR = 12.66%) in the early postoperative period (<30 days). ARR was the same at the literature high (27.3%) and weighted literature average (13.3%) complication rates when using the cost of I&D surgery at our institution ($1757.13) and the literature value for a smoking cessation program ($222.45). Cost-effectiveness was maintained with higher I&D surgery costs and lower costs of smoking cessation treatment.

Conclusion

Our model's input data suggest that the routine use of smoking cessation programs among tobacco users undergoing TAA is cost-effective for risk reduction of I&D surgery in the early postoperative period. This intervention was also found to be economically warranted with higher I&D costs and lower smoking cessation program costs than those found in the literature and at our institution.Level of Evidence: Level III, economic and decision analysis.

What Do Patients Report Regarding Their Real-World Function Following Triplane Metatarsophalangeal Joint Arthrodesis for Hallux Valgus?

First metatarsal phalangeal (MTP) joint arthrodesis has been employed for decades for pain related to arthritis and other associated abnormalities. Despite the commonality of the procedure there continues to be questions regarding functional expectations following the procedure especially when employed for correction of hallux valgus deformity. We surveyed 60 patients who had a tri plane MTP joint arthrodesis at mean 28.4 months (median 27.8) regarding their activities of daily living and sports activity through a direct conversation. Secondary endpoints assessed were return to activity, deformity correction and arthrodesis healing rate based on chart review and weightbearing radiographs. The primary outcomes showed robust return to all activities of daily living with 96.7% able to walk without restrictions and or pain, 98.3% were able to walk at a normal pace and 95% responded that loss of motion of their big toe did not affect their daily function. Regarding return to sports all patients that participated in sports before surgery resumed participation after with a trend toward increased sports activity. Early return to walking in a fracture boot was noted in this cohort at mean 4.1 days, return to athletic shoe at mean 6.3 weeks and full unrestricted activity at mean 13.3 weeks with no non-unions identified on radiographic or clinical exam. Deformity correction of the typical components of hallux valgus deformity was similar to previously published studies. This data set supports the hypothesis that patients undergoing first MTP joint arthrodesis can expect rapid and full return to activities of daily living and sports with a low complication rate.

A Study of Tibial Cyst Formation in Modular Stemmed Total Ankle Arthroplasty: Exploring a Possible Relationship to Smooth and Porous Coating on the Stem Segments

Vertical fixation through stemmed components has been a successful strategy in total ankle arthroplasty. Research in hip replacement surgery has demonstrated increased rates of stress shielding, aseptic loosening, thigh pain, and cystic formation around stemmed femoral implants extensively coated with porous surfaces. While some ankle prostheses have integrated porous coating technology with stemmed tibial implants, there is little to no research investigating the potential negative effects of bone bonding to the tibial stems and possible impact on tibial cyst formation. We performed a retrospective cohort study comparing the incidence of periprosthetic tibial cyst formation in smooth versus fully porous-coated stemmed tibial implants after undergoing total ankle implant arthroplasty. Radiographs were compared for postoperative rates of tibial cyst formation and bone bonding to the tibial stems. Relative risk for reoperation between the smooth and porous-coated implants was investigated. The smooth-stem group showed no incidence of tibial cyst formation nor signs of significant bone bonding to the tibial stems; however, the follow-up matched porous-coated group showed a rate of 63% of cystic formation with associated evidence of bone bonding on final radiographic follow-up (p < .01). Relative risk for reoperation was 0.74. Despite a higher incidence of tibial cyst formation in the stemmed ankle arthroplasty groups with porous coating, reoperation rates were similar. We theorize that the proximal bonding to the porous stem surface could impact the distal stems and result in the observed increase in cyst formation.

What Do Patients Report Regarding Their Real-World Function Following Triplane Metatarsophalangeal Joint Arthrodesis for Hallux Valgus?

First metatarsalphalangeal (MTP) joint arthrodesis has been employed for decades for pain related to arthritis and other associated abnormalities. Despite the commonality of the procedure there continues to be questions regarding functional expectations following the procedure especially when employed for correction of hallux valgus deformity. We surveyed 60 patients who had a triplane MTP joint arthrodesis at mean 28.4 months (median 27.8) regarding their activities of daily living and sports activity through a direct conversation. Secondary endpoints assessed were return to activity, deformity correction and arthrodesis healing rate based on chart review and weightbearing radiographs. The primary outcomes showed robust return to all activities of daily living with 97% able to walk without restrictions and or pain, 98% were able to walk at a normal pace and 95% responded that loss of motion of their big toe did not affect their daily function. Regarding return to sports all patients that participated in sports before surgery resumed participation after with a trend toward increased sports activity. Early return to walking in a fracture boot was noted in this cohort at mean 4.1 days, return to athletic shoe at mean 6.3 weeks and full unrestricted activity at mean 13.3 weeks with no non-unions identified on radiographic or clinical exam. Deformity correction of the typical components of hallux valgus deformity was similar to previously published studies. This data set supports the hypothesis that patients undergoing first MTP joint arthrodesis can expect rapid and full return to activities of daily living and sports with a low complication rate.

Maintenance of Correction of the Modified Lapidus Procedure With a First Metatarsal to Second Metatarsal Screw With "Spot Weld" Technique: A Retrospective and Radiographic Analysis

Lapidus first tarsometatarsal (TMT) arthrodesis gained popularity for its ability to correct large deformities especially in cases of medial column instability. Despite solid first TMT fusion, instability between the first and second columns can result in loss of intermetatarsal (IM) angle correction over time. A "spot weld" or fusion between the first and second metatarsal may improve maintenance of correction. This retrospective study reviewed cases of Lapidus arthrodesis with first to second metatarsal base screw fixation for maintenance of IM correction and determine whether a "spot weld" is predictive of maintenance. A total of 90 cases (77 patients) performed by a single surgeon met inclusion with average follow-up of 309 days. First TMT fusion occurred in 87/90 (96.7%) cases with 76 dorsal plate, 10 dorsal staple, and 4 all screws. No incidence of complications related to the 1-2 screw was noted. Mean preoperative IM 1-2 angle 14.90°, mean correction to 6.22° post-operative and final maintained correction at 7.10°, mean loss of correction 0.87°. There were "spot welds" in 65/90 (72.2%) with mean loss of 0.48° versus loss of 1.88° in "no spot weld" subgroup (p < .001). Cases with no spot weld and screw lucency lost 2.25° (p < .001). Loss of IM 1-2 correction can occur due to first and second ray intra-column instability even in cases of solid first TMT arthrodesis. Incorporating a completed "spot weld" with bone grafting and first to second metatarsal screw was found to maintain correction with minimal loss (0.87°).

Hounsfield Unit Assessed Bone Density Amongst Non-Traumatic and Post-Traumatic Arthritic Total Ankle Arthroplasty Patients

Category:

Ankle Arthritis; Ankle; Hindfoot; Trauma

Introduction/Purpose:

The etiology of ankle arthritis is multifactorial and secondary osseous changes to the tibiotalar joint can be variable. The relationship of bone density within the tibia and talus with respect to type of ankle arthritis is not well understood. Improved insight of osseous characteristics amongst ankle arthritis patients is helpful in determining optimal implant selection for total ankle arthroplasty. The purpose of this study is to retrospectively analyze pre-operative total ankle arthroplasty patients' films for osseous characteristics associated traumatic ankle arthritis compared to other forms of arthritis using computed tomography (CT) generated Hounsfield units (HU) to analyze bone mineral density and rate of cyst formation.

Methods:

A retrospective analysis was performed of 440 patients, under a single orthopedic practice, who underwent primary TAA between 2013-2019. Pre-operative HU of tibia and talus were analyzed amongst two groups (Non-traumatic OA, Post- traumatic OA) within one year prior to TAA.

Results:

Forty-nine qualified patients (23 NTA, 26 PTA) with mean follow-up in months of 19.98 (SD 15.22) were analyzed. Cystic changes at level of TAA cuts or retained bone: 5 tibia (10.2%), 7 talus (14.29%), 16 combined (32.65%). Overall tibial HU mean 270.23 (SD 91.28) and talus 463.26 (103.65). HU of the tibia amongst post-traumatic and non-traumatic patients was 257.21 (SD 93.9) and 284.94 (SD 87.9) (p=0.29137) and talus 434.53 (104.7) and 495.75 (94.33) (p=0.0365).

Conclusion:

Our results suggest with tibiotalar arthritis HU is a useful tool to predict bone quality. Clinical results amongst the NTA and PTA groups was comparable. Significantly lower HU values were recorded for the PTA groups. Rate of cystic formation within bone of distal tibia does not necessarily correlate with overall HU measured bone mineral density.

Stress Shielding and Aseptic Loosening in Fully Porous-Coated vs Smooth Stemmed Tibial Implants in Total Ankle Arthroplasty

Category:

Ankle Arthritis; Ankle

Introduction/Purpose:

Porous coating on the osseous interface of implants has gained increased popularity in total ankle replacement surgery. With the integration of porous coating into the newer generation of implants, this theoretically increases the chances of osseous ingrowth and survivorship in total ankle replacements. Alternatively, literature in hip replacement surgery has shown increased rates of stress shielding, aseptic loosening, thigh pain, and cystic formation around stemmed femoral implants extensively coated with porous surfaces. While some ankle prostheses have integrated porous coating technology with stemmed tibial implants, there is little to no research investigating the potential negative effects this may have on longevity or aseptic loosening secondary to a stress shielding effect.

Methods:

Our study identified 9 patients who underwent total ankle arthroplasty via a smooth-stemmed tibial prosthesis and matched these patients based on implant age with patients who received fully porous-coated tibial implants. We reviewed radiographs and compared postoperative rates of backside loosening and cystic formation secondary to stress shielding between the two groups. We also compared rates of heterotopic ossification between the two groups. A homoscedastic t-test was used to identify any statistical significance, which was defined as P < 0.05.

Results:

While the smooth-stem group showed no rates of backside cystic formation or stress shielding, the follow-up matched porous-coated group showed a rate of 55% of cystic formation and potential loosening secondary to stress shielding observed on final radiographic follow up (P < 0.01). There was no statistical difference between the two groups in their rates of heterotopic bone formation (P = 0.37).

Conclusion:

Despite having a relatively small sample size, this data shows that there is some consistency with the hip arthroplasty literature suggesting an increased risk for stress shielding in fully porous-coated stemmed tibial implants compared to smooth- stemmed tibial implants in total ankle arthroplasty.

Calcaneal Osteotomies in Prevention of Deformity-Driven Subtalar Joint Arthritis

Category:

Hindfoot

Introduction/Purpose:

Calcaneal osteotomies (CO) have been described thoroughly in reduction of hindfoot and global deformities of the foot and ankle. Their ability to alter the ground reactive forces and abnormal joint motion in various deformities, realigning the mechanical axes to a more normal alignment has been well-described in the literature. Despite the high volume of studies involving calcaneal osteotomies in the correction of hindfoot deformities, few have investigated the protective nature of them in the prevention of end-stage osteoarthritis of the subtalar joint. The purpose of the present study was to identify the preventative nature of calcaneal osteotomies in the prevention of deformity-driven subtalar joint arthritis.

Methods:

255 patients who underwent various calcaneal osteotomies (medial calcaneal displacement, lateral column lengthening, Dwyer) in a 2-year span were reviewed. Minimum of 3 years of follow up was required for the present study, and patient charts were reviewed to see if any went on to subtalar joint fusion secondary to deformity-driven osteoarthritis. Charts were also evaluated for hardware removal and nonunion rates, while lateral radiographs were evaluated for preoperative and long-term postoperative arthritis based on the Kellgren-Lawrence scale.

Results:

After inclusion criteria was applied, 44 patients were ultimately included in the study with an average follow up time of 51.8 months. In the end, 2.3% of patients underwent subtalar joint arthrodesis for treatment of deformity-driven osteoarthritis (1/44). Hardware removal and nonunion rates were 25% (11/44) and 2.3% (1/44), respectively. Kellgren-Lawrence evaluation showed there was some protective nature of CO's in prevention of subtalar joint arthritis, but the inter-observer coefficient was fair between two observers. ICC was fair for preoperative Kelgren Lawrence scores between the two presenters (ICC = 0.664), and poor for postoperative Kelgren Lawrence scores (ICC = 0.459).

Conclusion:

This is one of the only studies to evaluate the protective nature of calcaneal osteotomies in the prevention of deformity-driven subtalar joint arthritis. Clinical evaluation of this group suggested there is some protective nature in calcaneal osteotomies in the prevention of subtalar joint arthritis requiring arthrodesis, supporting the use of these osteotomies in the correction of hindfoot deformities. While the identified KG scores were not consistent between the two presenters, this is consistent with previous studies who investigated KG in the subtalar joint.

Post-Operative Lucency Formation Amongst Stemmed vs Non-Stemmed Total Ankle Arthroplasty Constructs

Category:

Ankle Arthritis; Ankle; Hindfoot

Introduction/Purpose:

Current available total ankle replacement constructs offer either proximal projecting pegs (non- stemmed) in various shapes or large stem (stemmed) designs to the superior aspect of the tibia component. Each design offers inherent stability and unique function. Periprosthetic radiolucency can develop post-operatively and lead to adverse effects. However, the incidence and clinical significance of lucency formation amongst stemmed and non-stemmed constructs is poorly understood.

Methods:

A retrospective radiographic and chart analysis was performed of 256 patients, under a single orthopedic practice, who underwent primary TAA between 2013-2019 with one of 3 total ankle systems. Pre-operative ankle characteristics, intraoperative procedures, as well as post-operative angles, lucency formation, region of lucency formation, and patient outcomes were analyzed.

Results:

Patients' mean age 65.5 yrs., male n=126 and female n=127, a mean follow-up of 24.3 months for our patient cohort. A total of 149 stemmed and 107 non-stemmed constructs were analyzed. Incidence of periprosthetic tibial lucency formation 33.2%, stemmed implants 10.0%, and 65.4% for non-stemmed implant (p value 0.00001).

Conclusion:

This paper describes the incidence of periprosthetic formation amongst a stemmed and non-stemmed total ankle arthroplasty cohort. Statistical significance was found when analyzing stemmed vs. non-stemmed incidence of radiolucency formation, this did not correlate with increased incidence of post-operative complications.

Emergency Department Visits for Ankle Fractures Through COVID-19: An Analysis of the National Electronic Injury Surveillance System

Background:

Societal changes that occurred during the COVID-19 pandemic may have altered the epidemiology of ankle fractures. The aim of this study was to assess trends in emergency department visits for ankle fractures from 2019 to 2020 in the United States.

Methods:

The National Electronic Injury Surveillance System (NEISS) database is a sample of hospitals in the United States stratified and weighted based on emergency department (ED) size, which was used to generate national estimates (NEs). The NEISS database was queried for patients who sustained an ankle fracture. Patients before COVID-19 (BC) (July 2019–December 2019) were compared to those during COVID-19 (DC) (July 2020–December 2020).

Results:

This study assessed 3350 (NE: 131,672) patients. Of these, 1683 (NE: 67,292) patients presented BC and 1667 (NE: 64,380) DC, representing a 4% decrease. The rate of alcohol-related ankle fractures increased (1.9% BC vs 2.6% DC; P < .001). The fraction of ankle fractures at school (3% BC vs 0.7% DC; P < .001) and during sports (19% BC vs 14% DC; P < .001) decreased. ED visits for ankle fracture leading to hospitalization marginally increased (23% BC vs 24% DC). The top 3 ankle fracture causes during COVID-19 were stairs (NE: 18,026, 28%), floors (ie, falling on floor) (NE: 4635, 7.2%), and skateboards (NE: 2832, 4.40%). The 3 largest increases in ankle fracture causes during COVID-19 were skateboards (+2.80%), floors (+1.10%), and powered scooters (+0.80%).

Conclusion:

There was a decrease in ankle fractures during the COVID-19 pandemic compared to the year before. Alcohol-related fractures increased as did fractures resulting in hospitalization. Ankle fractures caused by skateboards, powered scooters, and mopeds increased during COVID-19, whereas fewer occurred in school or during sports, consistent with restrictions to group activities. These findings may aid in proper health care budgeting in times of national and global crises.

Level of Evidence:

Level III, retrospective comparative study.

CCR2 contributes to host defense against Staphylococcus aureus orthopedic implant-associated infections in mice

C-C motif chemokine receptor 2 (CCR2) is an important mediator of myeloid cell chemotaxis during inflammation and infection. Myeloid cells such as monocytes, macrophages, and neutrophils contribute to host defense during orthopedic implant-associated infections (OIAI), but whether CCR2-mediated chemotaxis is involved remains unclear. Therefore, a Staphylococcus aureus OIAI model was performed by surgically placing an orthopedic-grade titanium implant and inoculating a bioluminescent S. aureus strain in knee joints of wildtype (wt) and CCR2-deficient mice. In vivo bioluminescent signals significantly increased in CCR2-deficient mice compared with wt mice at later time points (Days 14-28), which was confirmed with ex vivo colony-forming unit enumeration. S. aureus γ-hemolysin utilizes CCR2 to induce host cell lysis. However, there were no differences in bacterial burden when the OIAI model was performed with a parental versus a mutant γ-hemolysin-deficient S. aureus strain, indicating that the protection was mediated by the host cell function of CCR2 rather than γ-hemolysin virulence. Although CCR2-deficient and wt mice had similar cellular infiltrates in the infected joint tissue, CCR2-deficient mice had reduced myeloid cells and γδ T cells in the draining lymph nodes. Taken together, CCR2 contributed to host defense at later time points during an OIAI by increasing immune cell infiltrates in the draining lymph nodes, which likely contained the infection and prevented invasive spread.

Dynamic PET-facilitated modeling and high-dose rifampin regimens for Staphylococcus aureus orthopedic implant-associated infections

Staphylococcus aureus is a major human pathogen causing serious implant–associated infections. Combination treatment with rifampin (10 to 15 mg/kg per day), which has dose-dependent activity, is recommended to treat S. aureus orthopedic implant–associated infections. Rifampin, however, has limited bone penetration. Here, dynamic 11C-rifampin positron emission tomography (PET) performed in prospectively enrolled patients with confirmed S. aureus bone infection (n = 3) or without orthopedic infection (n = 12) demonstrated bone/plasma area under the concentration-time curve ratio of 0.14 (interquartile range, 0.09 to 0.19), exposures lower than previously thought. PET-based pharmacokinetic modeling predicted rifampin concentration-time profiles in bone and facilitated studies in a mouse model of S. aureus orthopedic implant infection. Administration of high-dose rifampin (human equipotent to 35 mg/kg per day) substantially increased bone concentrations (2 mg/liter versus <0.2 mg/liter with standard dosing) in mice and achieved higher bacterial killing and biofilm disruption. Treatment for 4 weeks with high-dose rifampin and vancomycin was noninferior to the recommended 6-week treatment of standard-dose rifampin with vancomycin in mice (risk difference, −6.7% favoring high-dose rifampin regimen). High-dose rifampin treatment ameliorated antimicrobial resistance (0% versus 38%; P = 0.04) and mitigated adverse bone remodeling (P < 0.01). Last, whole-genome sequencing demonstrated that administration of high-dose rifampin in mice reduced selection of bacterial mutations conferring rifampin resistance (rpoB) and mutations in genes potentially linked to persistence. These data suggest that administration of high-dose rifampin is necessary to achieve optimal bone concentrations, which could shorten and improve treatments for S. aureus orthopedic implant infections.

Surgical Takedown Approaches to Insertional Achilles Tendinopathy: A Systematic Review

Various techniques of surgical detachment for treatment of insertional Achilles tendinopathy have been described, including lateral release, medial release, central tendon splitting (CTS), and complete detachment. A systematic review of electronic databases was performed, encompassing 17 studies involving 703 patients and 746 feet, to compare outcomes associated with surgical takedown techniques. Observed results include wound complication rates (CTS 2.8%; Lateral 0%; Medial 0.4%; Complete 1.3%), postoperative rupture rates (CTS 0.7%; Lateral 0.8%; Medial 0.7%; Complete 2.6%), rate of revision (CTS 0.4%; Lateral 0.9%; Medial 4.2%; Complete 2.6%), rate of infection (CTS 1.1%; Lateral 1.7%; Medial 3.7%; Complete 6.5%). Lateral takedown group was found to have a statistically significant lower rate of complications compared to the complete takedown group (p = .0029). In light of these results, it is recommended that patient characteristics such as case specific tendon pathology and calcaneal morphology take precedent in determining the surgical approach to Achilles takedown.

Predilection for developing a hematogenous orthopaedic implant-associated infection in older versus younger mice

Background

The pathogenesis of hematogenous orthopaedic implant-associated infections (HOIAI) remains largely unknown, with little understanding of the influence of the physis on bacterial seeding. Since the growth velocity in the physis of long bones decreases during aging, we sought to evaluate the role of the physis on influencing the development of Staphylococcus aureus HOIAI in a mouse model comparing younger versus older mice.

Methods

In a mouse model of HOIAI, a sterile Kirschner wire was inserted retrograde into the distal femur of younger (5–8-week-old) and older (14–21-week-old) mice. After a 3-week convalescent period, a bioluminescent Staphylococcus aureus strain was inoculated intravenously. Bacterial dissemination to operative and non-operative legs was monitored longitudinally in vivo for 4 weeks, followed by ex vivo bacterial enumeration and X-ray analysis.

Results

In vivo bioluminescence imaging and ex vivo CFU enumeration of the bone/joint tissue demonstrated that older mice had a strong predilection for developing a hematogenous infection in the operative legs but not the non-operative legs. In contrast, this predilection was less apparent in younger mice as the infection occurred at a similar rate in both the operative and non-operative legs. X-ray imaging revealed that the operative legs of younger mice had decreased femoral length, likely due to the surgical and/or infectious insult to the more active physis, which was not observed in older mice. Both age groups demonstrated substantial reactive bone changes in the operative leg due to infection.

Conclusions

The presence of an implant was an important determinant for developing a hematogenous orthopaedic infection in older but not younger mice, whereas younger mice had a similar predilection for developing periarticular infection whether or not an implant was present. On a clinical scale, diagnosing HOIAI may be difficult particularly in at-risk patients with limited examination or other data points. Understanding the influence of age on developing HOIAI may guide clinical surveillance and decision-making in at-risk patients.

The impact of different Hormonal Growth Promotants (HGP) on desmin degradation and collagen content of various muscles from pasture and feedlot finished steer carcasses

The impacts of several hormonal growth promotants (HGP) on Warner-Bratzler Shear Force (WBSF), desmin degradation ratio (DDR) and collagen content (COLL) were assessed. Treatments within feedlot and pasture finished steer carcasses (n = 60, n = 40, respectively) were control (CON-100-F and CON-400-P), oestradiol HGPs (OES-100-F and OES-400-P) and trenbolone acetate/oestradiol HGPs (TBA+OES-100-F only). The longissimus lumborum (LL), gluteus medius (GM), infraspinatus (IS), semitendinosus (ST,) and the LL and biceps femoris (BF) were collected from feedlot and pasture finished steers, respectively. All muscles were aged between 3 and 35 days. The LL from TBA+OES-100-F carcasses had increased WBSF and decreased DDR, which varied in magnitude with ageing (P < 0.05). The GM from OES-100-F steers also had lower DDR (P < 0.05). The feedlot HGP treatments had no impact on the WBSF of the IS, ST or GM and no impact on COLL in the LL. The OES-400-P had no impact on WBSF, DDRor COLL for both muscles (P > 0.05).

Posterior Ankle Scope Approach to Symptomatic Os Trigonum Removal

INTRODUCTION

Os trigonum can become symptomatic following acute or chronic repetitive compression of the posterior ankle. Following conservative treatment failure, removal is often warranted. Current surgical options include traditional open resection and endoscopic removal. The purpose of this article is to review a population of patients who underwent endoscopic excision of symptomatic accessory os trigonum through a posterior approach and evaluate the outcomes of the procedure.

METHODS

From May 2009 to September 2018, all patients who underwent excision of a symptomatic os trigonum were reviewed. Outcomes of interest were major and minor complications and time to return to full weight-bearing activities. Postoperative protocol included 5 to 7 days non-weight-bearing and 1 to 2 weeks of protected weight-bearing followed by full release to weight-bearing activities.

RESULTS

Twelve patients who met the inclusion criteria were studied. Mean follow-up was 10.2 (±7.4) months with no major complications and 1 minor wound complication. Average advancement to protected weight-bearing was 7.1 days. Average return to full weight-bearing activities without restriction was 24.4 days.

CONCLUSION

The current study describes the technique and results to minimally invasive os trigonum removal with favorable postoperative outcomes. Results demonstrated minimal complications and postoperative pain, also quick return to weight-bearing and full activity.

LEVEL OF EVIDENCE

Therapeutic, Level IV: Case series.

Does a single adjustment in the meat standards Australia beef grading model cater for different hormonal growth promotant formulations?

This paper investigated whether a single Hormonal Growth Promotant (HGP) adjustment in the Meat Standards Australia (MSA) beef grading model adequately predicted consumer eating quality of beef from cattle treated with different HGP formulations. This paper used consumer sensory data from two experiments. In experiment one, a total of 300 steers were allocated to three treatments; control (CON-100-F), 100 day oestradiol only HGP (OES-100-F), or a combination of trenbolone acetate and oestradiol HGP (TBA+OES-100-F) and finished in a feedlot for 73 days. In experiment two, a total of 200 steers were allocated either control or 400 day oestradiol only HGP treatments and finished on pasture for 389 days. Steers were slaughtered by finishing regime and carcass traits recorded. The anterior and posterior portions of the m. longissimus lumborum (LL-A and LL-P, respectively) and m. gluteus medius (GM) were collected and aged for five or 35 days. Grilled meat samples were scored for tenderness, juiciness, liking of flavour and overall acceptability using untrained consumers. Sensory scores were weighted by 0.3. 0.1, 0.3 and 0.3, respectively and summed to calculate a meat quality (MQ4) score. Residual MQ4 scores were calculated (observed MQ4 minus the predicted MQ4 score). The MSA model accounts for varied impacts of different HGPs on eating quality through a single HGP adjustment, and indirect impacts on carcass traits. For the majority of the HGP treatment samples, the residual MQ4 scores were not different to zero (5/18), or were positive i.e. the MSA model under-predicted these samples (11/18). Under-prediction was predominately for 35 day aged (7/9) and GM HGP treatment samples (6/6) and was considered low, with the majority less than ±5 MQ4 units. Under-prediction could be considered as advantageous through providing an additional safeguard to protect the interests of the consumers, rather than if the model had over-predicted and resulted in a more negative eating quality experience than expected. Some over-prediction was observed in the CON-100-F and TBA+OES-100-F treatment samples, which may be due to factors such as genetic variation and/or production environment. Minimal bias was observed when residual MQ4 was regressed against predicted MQ4 for the range of feeding regimes, muscles, ageing periods and treatment groups. This study showed that a single HGP adjustment in the MSA beef grading model, combined with the indirect effects of the different HGP formulations on carcass traits, provided a reasonable prediction of meat eating quality for different HGP formulations.

Risk Factors for Complications Associated With Minimally Invasive Medial Displacement Calcaneal Osteotomy

BACKGROUND

Few studies have reported the outcomes following minimally invasive medial displacement calcaneal osteotomy (MDCO) for correction of pes planovalgus deformities.

METHODS

Charts were retrospectively reviewed for consecutive patients who underwent minimally invasive MDCO procedures by a single surgeon from 2013 to 2019 with more than 3 months of follow-up. A total of 160 consecutive patients who underwent 189 minimally invasive MDCO procedures were included in the study. Median follow-up was 12 months (interquartile range, 7-25 months).

RESULTS

Osteotomy healing complications were present in 7% of cases during the 6-year study period. A 12-month case cluster of osteotomy healing complications was observed. Healing complication rates were 28% during the cluster and 0.7% outside of the cluster. No definitive cause was found for the case cluster, although heat osteonecrosis from the burr was suspected to be involved. Osteotomy healing complications were significantly associated with higher American Society of Anesthesiologists (ASA) classification, female sex, current tobacco use, and higher body mass index (BMI). Healing complications were not associated with osteotomy technique or fixation type. Other complications included wound dehiscence (3%), surgical site infection (2%), transient nerve symptoms (6%), and persistent nerve symptoms (2%). Nerve symptoms were significantly associated with an increased number of concomitant procedures.

CONCLUSION

Patients with higher ASA classification, current tobacco use, and higher BMI were at higher risk for osteotomy healing complications after minimally invasive MDCO procedures. Patients were also more likely to develop nerve complications with more extensive surgical procedures.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Load to Failure and Stiffness of Interference Screw vs Pulvertaft Weave for Distal Fixation in Peroneal Allograft Reconstruction

BACKGROUND

Allograft reconstruction of the peroneal tendons is an option for treatment of major tears of 1 or both peroneal tendons. No consensus on a superior distal fixation method has been reported. The purpose of the study was to compare load to failure and stiffness of a Pulvertaft weave (PTW) through a residual tendon stump to direct-to-bone interference screw (IS) fixation.

METHODS

Fifteen pairs of long leg cadaver specimens were used. All grafts were secured proximally to the peroneus brevis myotendinous junction via a PTW technique. Distally, the tendons were either sutured to the peroneus brevis stump via PTW or secured to the base of the fifth metatarsal via IS. Stiffness (slope of force/displacement) was measured for the intact tendon and after reconstruction, and finally each specimen was loaded to failure.

RESULTS

Mean load to failure was significantly higher in the PTW group compared with the IS group (373.6 ± 265.5 N vs 150.1 ± 93.1 N; P = .01). The PTW and IS groups had significantly lower stiffness compared with the intact specimens (P < .001). There was no statistical significance in stiffness between the 2 techniques (P = .96).

CONCLUSION

The PTW technique yielded higher load to failure in comparison to IS. There was no difference in overall construct stiffness between both techniques. Both constructs demonstrated 19% decrease in stiffness compared to the intact state.

CLINICAL RELEVANCE

The PTW and IS constructs were biomechanically similar, and these results suggest that both should be moderately overtensioned to compensate for an inherent decreased initial stiffness.

Prediction of consumer palatability in beef using visual marbling scores and chemical intramuscular fat percentage

With development of objective technologies that can predict chemical intramuscular fat percentage (IMF%), there is a need to understand the relationships between existing marbling traits, IMF% and eating quality. This study utilised historical carcass data (n = 9641 observations) from the Meat Standards Australia (MSA) industry research dataset and included MSA grading data, chemical IMF% data and weighted composite eating quality scores (MQ4). Several analyses were performed to assess the prediction of MQ4 by MSA marbling, M. longissimus thoracis et lumborum (striploin) IMF% and cut specific IMF%. Results demonstrated that there was similar precision between chemical IMF% (R² = 0.32, RSE = 11.8) and MSA marbling (R² = 0.28, RSE = 11.9) in the prediction of grilled 14 day aged striploin MQ4, with similar results across other cut by cook by days aged combinations. These results support the development of objective technologies that predict chemical IMF% in parallel with MSA marbling for carcass grading and the prediction of eating quality.

Interleukin-1β and tumor necrosis factor are essential in controlling an experimental orthopedic implant-associated infection

Orthopedic implant-associated infection (OIAI) is a major complication that leads to implant failure. In preclinical models of Staphylococcus aureus OIAI, osteomyelitis and septic arthritis, interleukin-1α (IL-1α), IL-1β, and tumor necrosis factor (TNF) are induced, but whether they have interactive or distinctive roles in host defense are unclear. Herein, a S. aureus OIAI model was performed in mice deficient in IL-1α, IL-1β, or TNF. Mice deficient in IL-1β or TNF (to a lesser extent) but not IL-1α had increased bacterial burden at the site of the OIAI throughout the 28-day experiment. IL-1β and TNF had a combined and critical role in host defense as mice deficient in both IL-1R and TNF (IL-1R/TNF-deficient mice) had a 40% mortality rate, which was associated with markedly increased bacterial burden at the site of the OIAI infection. Finally, IL-1α- and IL-1β-deficient mice had impaired neutrophil recruitment whereas IL-1β-, TNF-, and IL-1R/TNF-deficient mice all had impaired recruitment of both neutrophils and monocytes. Therefore, IL-1β and TNF contributed to host defense against S. aureus OIAI and neutrophil recruitment was primarily mediated by IL-1β and monocyte recruitment was mediated by both IL-1β and TNF.

Rabbit model of Staphylococcus aureus implant-associated spinal infection

Post-surgical implant-associated spinal infection is a devastating complication commonly caused by Staphylococcus aureus. Biofilm formation is thought to reduce penetration of antibiotics and immune cells, contributing to chronic and difficult-to-treat infections. A rabbit model of a posterior-approach spinal surgery was created, in which bilateral titanium pedicle screws were interconnected by a plate at the level of lumbar vertebra L6 and inoculated with a methicillin-resistant S.aureus (MRSA) bioluminescent strain. In vivo whole-animal bioluminescence imaging (BLI) and ex vivo bacterial cultures demonstrated a peak in bacterial burden by day 14, when wound dehiscence occurred. Structures suggestive of biofilm, visualized by scanning electron microscopy, were evident up to 56 days following infection. Infection-induced inflammation and bone remodeling were also monitored using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and computed tomography (CT). PET imaging signals were noted in the soft tissue and bone surrounding the implanted materials. CT imaging demonstrated marked bone remodeling and a decrease in dense bone at the infection sites. This rabbit model of implant-associated spinal infection provides a valuable preclinical in vivo approach to investigate the pathogenesis of implant-associated spinal infections and to evaluate novel therapeutics.

Summary: A model of post-surgical methicillin-resistant Staphylococcus aureus implant-associated spinal infection was created in rabbits, recapitulating acute infection as well as chronic low-burden infection, with structures suggestive of biofilm formation and bone remodeling.

Preclinical Optical Imaging to Study Pathogenesis, Novel Therapeutics and Diagnostics Against Orthopaedic Infection

Preclinical in vivo optical imaging includes bioluminescence imaging (BLI) and fluorescence imaging (FLI), which provide noninvasive and longitudinal monitoring of biological processes in an in vivo context. In vivo BLI involves the detection of photons of light from bioluminescent bacteria engineered to naturally emit light in preclinical animal models of infection. Meanwhile, in vivo FLI involves the detection of photons of a longer emission wavelength of light after exposure of a fluorophore to a shorter excitation wavelength of light. In vivo FLI has been used in preclinical animal models to detect fluorescent-labeled host proteins or cells (often in engineered fluorescent reporter mice) to understand host-related processes, or to detect injectable near-infrared fluorescent probes as a novel approach for diagnosing infection. This review describes the use of in vivo optical imaging in preclinical models of orthopaedic implant-associated infection (OIAI), including (i) pathogenesis of the infectious course, (ii) monitoring efficacy of antimicrobial prophylaxis and therapy and (iii) evaluating novel near-infrared fluorescent probes for diagnosing infection. Finally, we describe optoacoustic imaging and fluorescence image-guided surgery, which are recent technologies that have the potential to translate to diagnosing and treating OIAI in humans. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2269-2277, 2019.

Attitudes and self-reported practices of orthopedic providers regarding prescription opioid use

OBJECTIVE

Orthopedic surgeons are the third-highest opioid prescribers in the United States. Their prescribing practices can significantly affect the quantity of unconsumed opioids available to fuel the current opioid epidemic. The aim of this study was to identify prescribing patterns and knowledge gaps among orthopedic providers for targeted future interventions and investigation.

DESIGN

An online survey describing six common orthopedic surgical scenarios was distributed electronically to determine opioid type and quantity prescribed at discharge, medication disposal instructions, and the use of prescription drug monitoring programs (PDMPs) in the prescription writing process.

SETTING

Tertiary care academic hospitals.

PARTICIPANTS

Orthopedic physicians and mid-level providers practicing at Johns Hopkins Medical Institutions and University of Maryland Medical System. Of 179 providers contacted, 127 (71 percent) completed the survey.

MAIN OUTCOME MEASURES

Quantity of opioid prescribed, utilization of PDMPs, and provision of opioid disposal instructions.

RESULTS

While statistically significant associations were identified between quantity of opioid prescribed and surgical procedure, for five of six scenarios 95 percent of respondents recommended prescribing >55 oxycodone 5 mg pill equivalents (PEs) at discharge. An inverse correlation between years of clinical practice and mean number of PEs prescribed was observed. Fewer than 40 percent of respondents modified prescribing when presented with clinically relevant changes in scenario (history of depression or drug abuse). Over 60 percent of respondents do not use PDMPs, and 79 percent do not provide opioid disposal instructions.

CONCLUSIONS

Our findings support a need for targeted education to mitigate the role of orthopedic postoperative prescribing practices on the current opioid abuse epidemic.

In Vivo Bioluminescence Imaging in a Rabbit Model of Orthopaedic Implant-Associated Infection to Monitor Efficacy of an Antibiotic-Releasing Coating

BACKGROUND

In vivo bioluminescence imaging (BLI) provides noninvasive monitoring of bacterial burden in animal models of orthopaedic implant-associated infection (OIAI). However, technical limitations have limited its use to mouse and rat models of OIAI. The goal of this study was to develop a larger, rabbit model of OIAI using in vivo BLI to evaluate the efficacy of an antibiotic-releasing implant coating.

METHODS

A nanofiber coating loaded with or without linezolid-rifampin was electrospun onto a surgical-grade locking peg. To model OIAI in rabbits, a medial parapatellar arthrotomy was performed to ream the femoral canal, and a bright bioluminescent methicillin-resistant Staphylococcus aureus (MRSA) strain was inoculated into the canal, followed by retrograde insertion of the coated implant flush with the articular surface. In vivo BLI signals were confirmed by ex vivo colony-forming units (CFUs) from tissue, bone, and implant specimens.

RESULTS

In this rabbit model of OIAI (n = 6 rabbits per group), implants coated without antibiotics were associated with significantly increased knee width and in vivo BLI signals compared with implants coated with linezolid-rifampin (p < 0.001 and p < 0.05, respectively). On day 7, the implants without antibiotics were associated with significantly increased CFUs from tissue (mean [and standard error of the mean], 1.4 × 10 ± 2.1 × 10 CFUs; p < 0.001), bone (6.9 × 10 ± 3.1 × 10 CFUs; p < 0.05), and implant (5.1 × 10 ± 2.2 × 10 CFUs; p < 0.05) specimens compared with implants with linezolid-rifampin, which demonstrated no detectable CFUs from any source.

CONCLUSIONS

By combining a bright bioluminescent MRSA strain with modified techniques, in vivo BLI in a rabbit model of OIAI demonstrated the efficacy of an antibiotic-releasing coating.

CLINICAL RELEVANCE

The new capability of in vivo BLI for noninvasive monitoring of bacterial burden in larger-animal models of OIAI may have important preclinical relevance.

Mouse model of Gram-negative prosthetic joint infection reveals therapeutic targets

Bacterial biofilm infections of implantable medical devices decrease the effectiveness of antibiotics, creating difficult-to-treat chronic infections. Prosthetic joint infections (PJI) are particularly problematic because they require prolonged antibiotic courses and reoperations to remove and replace the infected prostheses. Current models to study PJI focus on Gram-positive bacteria, but Gram-negative PJI (GN-PJI) are increasingly common and are often more difficult to treat, with worse clinical outcomes. Herein, we sought to develop a mouse model of GN-PJI to investigate the pathogenesis of these infections and identify potential therapeutic targets. An orthopedic-grade titanium implant was surgically placed in the femurs of mice, followed by infection of the knee joint with Pseudomonas aeruginosa or Escherichia coli. We found that in vitro biofilm-producing activity was associated with the development of an in vivo orthopedic implant infection characterized by bacterial infection of the bone/joint tissue, biofilm formation on the implants, reactive bone changes, and inflammatory immune cell infiltrates. In addition, a bispecific antibody targeting P. aeruginosa virulence factors (PcrV and Psl exopolysaccharide) reduced the bacterial burden in vivo. Taken together, our findings provide a preclinical model of GN-PJI and suggest the therapeutic potential of targeting biofilm-associated antigens.

Use of reprocessed external fixators in orthopaedic surgery: a survey of 243 orthopaedic trauma surgeons

Background

The increasing financial burden of orthopaedic implants on our health care system has prompted cost-control measures, such as implant reprocessing. The purpose of this study was to describe the current usage by orthopaedic trauma surgeons of reprocessed external fixators (EFs) for treatment of complex fractures.

Methods

A 16-question survey about use and perceptions of reprocessed EFs was distributed to 894 Orthopaedic Trauma Association members between August 2016 and June 2017 using a web-based survey system.

Results

The authors received 243 responses (27%). Thirty-seven percent of respondents reported using reprocessed EFs. Nonprofit hospitals used reprocessed EFs more commonly than did for-profit hospitals (41% vs 15%, P = .0004). Eighty-seven percent of respondents believed reprocessing could be cost-effective. The most common reason (32%) for not using reprocessed EFs was coordination/logistics of reprocessing. Concern about litigation was also reported as a main reason for not using (20%) or having recently stopped using (21%) reprocessed EFs.

Conclusions

Many orthopaedic traumatologists are interested in the reprocessing of EF components but few have reprocessing systems in place at their institutions. A major barrier to implementation is concern about litigation, which is likely unwarranted on the basis of Food and Drug Administration approval and a lack of previous litigation. Reprocessing by the original device manufacturers has yielded substantial savings at our institution and is an example of the cost savings that can be expected when implementing an EF reprocessing system.

The effect of packaging on consumer eating quality of beef

This experiment examined 3 packaging systems: overwrap packaging using oxygen permeable film (OWP); vacuum skin packaging (VSP) and modified atmosphere packaging (MAP, 80%O₂ and 20%CO₂) on consumer sensory. Three primals from 48 carcasses were aged in vacuum packs for 5, 12 or 40 days. Steaks from longissimus lumborum, gluteus medius and psoas major muscles were packed in OWP, VSP and MAP for 9 days. Untrained consumers scored grilled steaks for tenderness, juiciness, liking of flavour and overall acceptability. Steaks in MAP had 10-12 points lower sensory scores (on a 100 point scale) compared to the OWP, or VSP systems (P < 0.001). The packaging effect was independent of days aging and muscle. It was concluded that high oxygen MAP has the potential to be included as an input variable in the Meat Standards Australia beef grading model. This would be contingent upon research into when the MAP effect occurred and the effect of using different gas mixtures on eating quality.

Do extended transport times and rest periods impact on eating quality of beef carcasses?

The experiment tested the effect of four extended transport treatments on sensory and objective meat quality in beef. A total of 343 steers (88 steers from each of three properties and 79 from a fourth property) were allocated to four treatments including a 12 hour transport time (T12), 24 hour transport time (T24), 24 h as 12 hour transport time, a 12 hour rest, with a further 12 hour transport (T12 ~ T12), 36 hour transport treatment (T36). Within property departure times of treatments were staggered to arrive at the abattoir together. There were no significant transport effects (P > .05) on live animal, carcass traits, consumer sensory scores, and objective meat quality of the longissimus lumborum. There was large between property variation in the proportions of carcasses excluded from grading on the basis of low ribfat, high ultimate pH and dark meat color scores. Variation in these traits was not associated with transport treatments and was likely related to variation in on-farm factors.

Noninvasive optical and nuclear imaging of Staphylococcus-specific infection with a human monoclonal antibody-based probe

Staphylococcus aureus infections are a major threat in healthcare, requiring adequate early-stage diagnosis and treatment. This calls for novel diagnostic tools that allow noninvasive in vivo detection of staphylococci. Here we performed a preclinical study to investigate a novel fully-human monoclonal antibody 1D9 that specifically targets the immunodominant staphylococcal antigen A (IsaA). We show that 1D9 binds invariantly to S. aureus cells and may further target other staphylococcal species. Importantly, using a human post-mortem implant model and an in vivo murine skin infection model, preclinical feasibility was demonstrated for 1D9 labeled with the near-infrared fluorophore IRDye800CW to be applied for direct optical imaging of in vivo S. aureus infections. Additionally, ⁸⁹Zirconium-labeled 1D9 could be used for positron emission tomography imaging of an in vivo S. aureus thigh infection model. Our findings pave the way towards clinical implementation of targeted imaging of staphylococcal infections using the human monoclonal antibody 1D9.

The Development of Technology for Effective Respiratory-Gated Irradiation Using an Image-Guided Small Animal Irradiator

The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice. Therefore, a new treatment head assembly for the Xstrahl Small Animal Radiation Research Platform (SARRP) has been designed. This includes a fast X-ray shutter subsystem, a motorized beam hardening filter assembly, an integrated transmission ionization chamber to monitor beam delivery, a kinematically positioned removable beam collimator and a targeting laser exiting the center of the beam collimator. The X-ray shutter not only minimizes timing errors but also allows beam gating during imaging and treatment, with irradiation only taking place during the breathing cycle when tissue movement is minimal. The breathing related movement is monitored by measuring, using a synchronous detector/lock-in amplifier that processes diffuse reflectance light from a modulated light source. After thresholding of the resulting signal, delays are added around the inhalation/exhalation phases, enabling the "no movement" period to be isolated and to open the X-ray shutter. Irradiation can either be performed for a predetermined time of X-ray exposure, or through integration of a current from the transmission monitor ionization chamber (corrected locally for air density variations). The ability to successfully deliver respiratory-gated X-ray irradiations has been demonstrated by comparing movies obtained using planar X-ray imaging with and without respiratory gating, in addition to comparing dose profiles observed from a collimated beam on EBT3 radiochromic film mounted on the animal's chest. Altogether, the development of respiratory-gated irradiation facilitates improved dose delivery during animal movement and constitutes an important new tool for preclinical radiation studies. This approach is particularly well suited for irradiation of orthotopic tumors or other targets within the chest and abdomen where breathing related movement is significant.

Effect of excessive gestational weight gain on trial of labour after caesarean: A retrospective cohort study

BACKGROUND

Counselling women for and managing birth after caesarean section are important. Research is needed on evaluation of antenatal factors that predict likelihood of successful trial of labour after caesarean section (TOLAC).

AIM

To evaluate the effect of gestational weight gain on mode of delivery in women having TOLAC.

MATERIALS AND METHODS

A retrospective cohort study of eligible women who underwent TOLAC (January 2012 to July 2015) at a large urban hospital. Gestational weight gain was classified as 'excessive' or 'not excessive' based on calculated pre-pregnancy body mass index. Multivariable logistic regression analysis was performed to estimate the association of gestational weight gain and vaginal birth, adjusting for socio-demographic and pregnancy-related factors.

RESULTS

Of 534 women, those who gained excessive weight were less likely to have a vaginal birth as women who did not (adjusted odds ratio (aOR) 0.48, 95% confidence interval (CI) 0.29-0.81)). Women with previous vaginal birth were more likely to have a vaginal birth (aOR 3.74, 95% CI 1.90-7.36), while women ≥35, women who had an epidural, and women who delivered at 40 weeks, were less likely (aOR 0.58, 95% CI 0.35-0.97, aOR 0.12, 95% CI 0.07-0.22, and aOR 0.53, 95% CI 0.31-0.91, respectively).

CONCLUSIONS

Gaining excessive weight in pregnancy is potentially modifiable, and can be incorporated into individual antenatal counselling, and into risk prediction models, to assist with informed decision making around planned mode of delivery in women with previous caesarean section. Future research could focus on interventions to reduce gestational weight gain in women planning TOLAC.

Staphylococcus aureus alpha-toxin and Clumping Factor A are pathogenic and immunotherapeutic targets against a hematogenous implant-related biofilm infection

Infection is a major impediment to the long-term success of implantable medical devices. Treatment of these infections is complicated by bacteria biofilms, which form on the implants and block penetration of immune cells and antibiotics. Hematogenous implant-related infections following a transient bacteremia are particularly problematic because they can occur at any time in a previously stable implant. To evaluate alternative targeted immune-based therapies against these infections, we developed a hematogenous infection model in which an orthopaedic titanium implant was surgically placed in the legs of mice followed by an intravenous injection of Staphylococcus aureus 21 days later. This resulted in a marked propensity for a hematogenous implant-related infection comprised of septic arthritis, osteomyelitis with neutrophil abscess formation in the bone and biofilm formation on the implants in the surgical legs compared with sham surgical legs without implant placement or contralateral nonsurgical normal legs. Prophylaxis with two neutralizing human monoclonal antibodies directed against S. aureus virulence factors, secreted alpha-toxin (AT) and surface expressed clumping factor A (ClfA) inhibited biofilm formation in vitro and the hematogenous implant-related infection in vivo. Our findings suggest that AT and ClfA are important pathogenic factors that could be targeted as a novel immunotherapeutic against S. aureus hematogenous implant-related infections.

Oral-Only Linezolid-Rifampin Is Highly Effective Compared with Other Antibiotics for Periprosthetic Joint Infection: Study of a Mouse Model

BACKGROUND

The medical treatment of periprosthetic joint infection (PJI) involves prolonged systemic antibiotic courses, often with suboptimal clinical outcomes including increased morbidity and health-care costs. Oral and intravenous monotherapies and combination antibiotic regimens were evaluated in a mouse model of methicillin-resistant Staphylococcus aureus (MRSA) PJI.

METHODS

Oral linezolid with or without oral rifampin, intravenous vancomycin with oral rifampin, intravenous daptomycin or ceftaroline with or without oral rifampin, oral doxycycline, or sham treatment were administered at human-exposure doses for 6 weeks in a mouse model of PJI. Bacterial burden was assessed by in vivo bioluminescent imaging and ex vivo counting of colony-forming units (CFUs), and reactive bone changes were evaluated with radiographs and micro-computed tomography (μCT) imaging.

RESULTS

Oral-only linezolid-rifampin and all intravenous antibiotic-rifampin combinations resulted in no recoverable bacteria and minimized reactive bone changes. Although oral linezolid was the most effective monotherapy, all oral and intravenous antibiotic monotherapies failed to clear infection or prevent reactive bone changes.

CONCLUSIONS

Combination antibiotic-rifampin regimens, including oral-only linezolid-rifampin and the newer ceftaroline-rifampin combinations, were highly effective and more efficacious than monotherapies when used against a preclinical MRSA PJI.

CLINICAL RELEVANCE

This study provides important preclinical evidence to better optimize future antibiotic therapy against PJIs. In particular, the oral-only linezolid-rifampin option might reduce venous access complications and health-care costs.

Rho-associated kinase 1 inhibition is synthetically lethal with von Hippel-Lindau deficiency in clear cell renal cell carcinoma

Clear Cell Renal Cell Carcinoma (CC-RCC) is the most lethal of all genitourinary cancers. The functional loss of the von Hippel-Lindau (VHL) gene occurs in 90% of CC-RCC, driving cancer progression. The objective of this study was to identify chemical compounds that are synthetically lethal with VHL deficiency in CC-RCC. An annotated chemical library, the Library of Pharmacologically Active Compounds (LOPAC), was screened in parallel on VHL-deficient RCC4 cells and RCC4VHL cells with re-introduced VHL cDNA. The ROCK inhibitor, Y-27632, was identified and validated for selective targeting of VHL-deficient CC-RCC in multiple genetic backgrounds by clonogenic assays. Downregulation of ROCK1 by siRNA selectively reduced the colony forming ability of VHL-deficient CC-RCC, thus mimicking the effect of Y-27632 treatment, whereas downregulation of ROCK2 had no effect. In addition, two other ROCK inhibitors, RKI 1447 and GSK 429286, selectively targeted VHL-deficient CC-RCC. CC-RCC treatment with ROCK inhibitors is cytotoxic and cytostatic based on BrdU assay, Propidium Iodide (PI) staining, and growth curves; and blocks cell migration based on transwell assay. Importantly, knockdown of Hypoxia Inducible Factor (HIF) β in the VHL-deficient CC-RCC had a protective effect against Y-27632 treatment, mimicking VHL reintroduction. On the other hand, CC-RCCVHL cells were sensitized to Y-27632 treatment in hypoxia (2% O₂). These results suggest that synthetic lethality between ROCK inhibition and VHL deficiency is dependent on HIF activation. Moreover, HIF1α or HIF2α overexpression in CC-RCCVHL cells is sufficient to sensitize them to ROCK inhibition. Finally, Y-27632 treatment inhibited growth of subcutaneous 786-OT1 CC-RCC tumors in mice. Thus, ROCK inhibitors represent potential therapeutics for VHL-deficient CC-RCC.

Organizational and market factors associated with Medicare dependence in inpatient rehabilitation hospitals

Rehabilitation hospitals in the USA have been excluded from the Medicare Prospective Payment System (PPS) system since 1982, and have received cost-based reimbursement. However, the 1997 Balanced Budget Act mandated a PPS for inpatient rehabilitation, to be implemented by the end of 2002. This study assesses rehabilitation hospitals' dependency on Medicare. Findings show that not-for-profit hospitals, facilities with fewer services, facilities with lower staffing levels, and hospitals with lower operating expenses and profits, have a higher proportion of their inpatient revenue coming from Medicare. These facilities may be vulnerable to the new PPS payment system.

Neurocognitive intra-individual variability in mood disorders: effects on attentional response time distributions

BACKGROUND

Attentional impairment is a core cognitive feature of major depressive disorder (MDD) and bipolar disorder (BD). However, little is known of the characteristics of response time (RT) distributions from attentional tasks. This is crucial to furthering our understanding of the profile and extent of cognitive intra-individual variability (IIV) in mood disorders.

METHOD

A computerized sustained attention task was administered to 138 healthy controls and 158 patients with a mood disorder: 86 euthymic BD, 33 depressed BD and 39 medication-free MDD patients. Measures of IIV, including individual standard deviation (iSD) and coefficient of variation (CoV), were derived for each participant. Ex-Gaussian (and Vincentile) analyses were used to characterize the RT distributions into three components: mu and sigma (mean and standard deviation of the Gaussian portion of the distribution) and tau (the 'slow tail' of the distribution).

RESULTS

Compared with healthy controls, iSD was increased significantly in all patient samples. Due to minimal changes in average RT, CoV was only increased significantly in BD depressed patients. Ex-Gaussian modelling indicated a significant increase in tau in euthymic BD [Cohen's d = 0.39, 95% confidence interval (CI) 0.09-0.69, p = 0.011], and both sigma (d = 0.57, 95% CI 0.07-1.05, p = 0.025) and tau (d = 1.14, 95% CI 0.60-1.64, p < 0.0001) in depressed BD. The mu parameter did not differ from controls.

CONCLUSIONS

Increased cognitive variability may be a core feature of mood disorders. This is the first demonstration of differences in attentional RT distribution parameters between MDD and BD, and BD depression and euthymia. These data highlight the utility of applying measures of IIV to characterize neurocognitive variability and the great potential for future application.

A Systems Pharmacology Model of Erythropoiesis in Mice Induced by Small Molecule Inhibitor of Prolyl Hydroxylase Enzymes

Mammalian erythropoiesis is a conserved process tightly controlled by the hypoxia-inducible factor (HIF1) pathway. In this study, a small molecule inhibitor (PHI-1) of prolyl-hydroxylase-2 (PHD2) enzyme involved in regulating HIF1α levels was orally administered to male BALB/c mice at 10 and 30 mg/kg. A systems pharmacology model was developed based on the measured PHI-1 plasma exposures, kidney HIF1α, kidney erythropoietin (EPO) mRNA, plasma EPO, reticulocyte counts, red blood cells, and hemoglobin levels. The model fit resulted in the estimation of drug potency (IC₅₀: 1.7μM), and systems parameters such as EPO mRNA turnover (k_{deg_EPOmRNA}: 0.43 hr^-1) and mean lifespan of reticulocytes (T_r: 81 hours). The model correctly described the observed 30–40-fold increase in kidney HIF1α protein, ∼1,000 fold increase in EPO mRNA and 2–3-fold increase in the reticulocytes at 30 mg/kg. This study presents the first parsimonious systems model of erythropoiesis to quantitatively describe the in vivo effects of PHD2 inhibition.

Glenoid notch MRI findings do not predict normal variants of the anterior and superior labrum

AIM

To determine (1) the relationship of a glenoid notch to the presence of a normal labral variant in the anterior-superior glenoid labrum; (2) the inter- and intra-observer reliability of recognising a glenoid notch; and (3) whether magnetic resonance arthrography (MRA) is more reliable than non-contrast magnetic resonance imaging (MRI) in visualising a glenoid notch.

MATERIALS AND METHODS

From 1995 through 2010, 104 patients underwent MRI or MRA before diagnostic shoulder arthroscopy by the senior author. Five blinded musculoskeletal radiologists independently read the images twice to evaluate for the presence or absence of a glenoid notch. Fifty-nine (57%) patients had normal anterior-superior labral variants. The authors calculated the relationship of the readings to the arthroscopically determined presence or absence of a normal labral variant and the reading's diagnostic performance and rater reliability.

RESULTS

On average, 38% (range 9-65%) of the glenoid scans were read as notched. The sensitivity, specificity, positive predictive value, and negative predictive value of the notch relative to the presence of a normal variant were 43.1%, 71.2%, 70.2%, and 48% versus 44.3%, 77.5%, 79.4%, and 56.1% for MRI and MRA, respectively. The overall average intra-observer κ-values were 0.438 (range 0.203-0.555) and 0.346 (range -0.102 to 0.570) for MRI and MRA, respectively. The average interobserver intra-class correlation coefficient reliability values were 0.730 (range 0.693-0.760) and 0.614 (range 0.566-0.662) for MRI and MRA, respectively.

CONCLUSIONS

A notched glenoid on MRI lacks sufficient diagnostic performance and rater reliability for the clinical detection and prediction of normal anterior-superior labral variants.

Ruralizing the Canadian Triage and Acuity Scale

L’échelle canadienne de triage et de gravité (ÉTG) a été introduite dans les années 90 et est rapidement en voie de devenir la norme canadienne de triage. Mais depuis 1997, moment où l’Institut canadien d’information sur la santé a commencé à promouvoir l’ÉTG, certains médecins de campagne ont manifesté leurs préoccupations, signalant l’existence de d’autres systèmes de triage et mettant en doute l’efficacité de l’ÉTG dans les milieux ruraux.

Les médecins des milieux ruraux soulèvent divers points: une perception de la complexité de l’ÉTG, un délai de réponse apparemment court pour l’évaluation par le médecin (et les ramifications médico-légales de la définition de ces délais), et une validation inadéquate de l’ÉTG dans les milieux ruraux. Le présent article explore l’historique de cette controverse et ébauche des solutions possibles. Les auteurs concluent que l’ÉTG est un outil malléable qui peut être «adapté» aux milieux ruraux et qu’il permettra par la suite d’améliorer les soins aux patients et les conditions de travail des infirmières et des médecins de ces milieux.

A meta-analysis of zilpaterol and ractopamine effects on feedlot performance, carcass traits and shear strength of meat in cattle

This study is a meta-analysis of the effects of the beta-agonists zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RAC) on feedlot performance, carcase characteristics of cattle and Warner Bratzler shear force (WBSF) of muscles. It was conducted to evaluate the effect of the use of these agents on beef production and meat quality and to provide data that would be useful in considerations on the effect of these agents on meat quality in Meat Standards Australia evaluations. We conducted a comprehensive literature search and study assessment using PubMed, Google Scholar, ScienceDirect, Scirus, and CAB and identification of other studies from reference lists in papers and searches. Searches were based on the key words: zilpaterol, zilmax, ractopamine, optaflexx, cattle and beef. Studies from theses obtained were included. Data were extracted from more than 50 comparisons for both agents and analysed using meta-analysis and meta-regression. Both agents markedly increased weight gain, hot carcase weight and longissimus muscle area and increased the efficiency of gain:feed. These effects were particularly large for ZH, however, fat thickness was decreased by ZH, but not RAC. Zilpaterol also markedly increased WBSF by 1.2 standard deviations and more than 0.8 kg, while RAC increased WBSF by 0.43 standard deviations and 0.2 kg. There is evidence in the ZH studies, in particular, of profound re-partitioning of nutrients from fat to protein depots. This work has provided critically needed information on the effects of ZH and RAC on production, efficiency and meat quality.

Molecular value predictions: associations with beef quality, carcass, production, behavior, and efficiency phenotypes in Brahman cattle

Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australia (WA; n = 135), were used to test molecular value predictions (MVP), generated from commercially available gene markers, on economically important traits of Bos indicus (Brahman) cattle. Favorable tenderness MVP scores were associated with reduced shear force values of strip loin (LM) steaks aged 7 d from Achilles-hung carcasses (P ≤ 0.06), as well as steaks aged 1 (P ≤ 0.08) or 7 d (P ≤ 0.07) from carcasses hung from the pelvis (tenderstretch). Favorable tenderness MVP scores were also associated with improved consumer tenderness ratings for strip loin steaks aged 7 d and either Achilles hung (P ≤ 0.006) or tenderstretched (P ≤ 0.07). Similar results were observed in NSW for rump (top butt; gluteus medius) steaks, with favorable tenderness MVP scores associated with more tender (P = 0.006) and acceptable (P = 0.008) beef. Favorable marbling MVP scores were associated with improved (P ≤ 0.021) marbling scores and intramuscular fat (IMF) content in the NSW experiment, despite low variation in marbling in the Brahman cattle. For the WA experiment, however, there were no (P ≥ 0.71) relationships between marbling MVP and marbling scores or IMF content. Although residual (net) feed intake (RFI) was not associated (P = 0.63) with the RFI (feed efficiency) MVP, the RFI MVP was adversely associated with LM tenderness and acceptability of 7-d-aged Achilles-hung carcasses in NSW (P ≤ 0.031) and WA (P ≤ 0.037). Some other relationships and trends were noted between the MVP and the other traits, but few reached statistical significance, and none were evident in both experiments. Results from this study provide evidence to support the use of the tenderness MVP. The value of the marbling MVP, which was associated with marbling in only 1 herd, warrants further evaluation; however, there appears to be no evidence to support use of the RFI MVP in Brahman cattle.

Neuropsychological testing of cognitive impairment in euthymic bipolar disorder: an individual patient data meta-analysis

OBJECTIVE

An association between bipolar disorder and cognitive impairment has repeatedly been described, even for euthymic patients. Findings are inconsistent both across primary studies and previous meta-analyses. This study reanalysed 31 primary data sets as a single large sample (N = 2876) to provide a more definitive view.

METHOD

Individual patient and control data were obtained from original authors for 11 measures from four common neuropsychological tests: California or Rey Verbal Learning Task (VLT), Trail Making Test (TMT), Digit Span and/or Wisconsin Card Sorting Task.

RESULTS

Impairments were found for all 11 test-measures in the bipolar group after controlling for age, IQ and gender (Ps ≤ 0.001, E.S. = 0.26-0.63). Residual mood symptoms confound this result but cannot account for the effect sizes found. Impairments also seem unrelated to drug treatment. Some test-measures were weakly correlated with illness severity measures suggesting that some impairments may track illness progression.

CONCLUSION

This reanalysis supports VLT, Digit Span and TMT as robust measures of cognitive impairments in bipolar disorder patients. The heterogeneity of some test results explains previous differences in meta-analyses. Better controlling for confounds suggests deficits may be smaller than previously reported but should be tracked longitudinally across illness progression and treatment.

Video image analysis in the Australian meat industry - precision and accuracy of predicting lean meat yield in lamb carcasses

A wide selection of lamb types of mixed sex (ewes and wethers) were slaughtered at a commercial abattoir and during this process images of 360 carcasses were obtained online using the VIAScan® system developed by Meat and Livestock Australia. Soft tissue depth at the GR site (thickness of tissue over the 12th rib 110 mm from the midline) was measured by an abattoir employee using the AUS-MEAT sheep probe (PGR). Another measure of this thickness was taken in the chiller using a GR knife (NGR). Each carcass was subsequently broken down to a range of trimmed boneless retail cuts and the lean meat yield determined. The current industry model for predicting meat yield uses hot carcass weight (HCW) and tissue depth at the GR site. A low level of accuracy and precision was found when HCW and PGR were used to predict lean meat yield (R(2)=0.19, r.s.d.=2.80%), which could be improved markedly when PGR was replaced by NGR (R(2)=0.41, r.s.d.=2.39%). If the GR measures were replaced by 8 VIAScan® measures then greater prediction accuracy could be achieved (R(2)=0.52, r.s.d.=2.17%). A similar result was achieved when the model was based on principal components (PCs) computed from the 8 VIAScan® measures (R(2)=0.52, r.s.d.=2.17%). The use of PCs also improved the stability of the model compared to a regression model based on HCW and NGR. The transportability of the models was tested by randomly dividing the data set and comparing coefficients and the level of accuracy and precision. Those models based on PCs were superior to those based on regression. It is demonstrated that with the appropriate modeling the VIAScan® system offers a workable method for predicting lean meat yield automatically.

Ryanodine receptors are uncoupled from contraction in rat vena cava

Ryanodine receptors (RyR) are Ca(2+)-sensitive ion channels in the sarcoplasmic reticulum (SR) membrane, and are important effectors of SR Ca(2+) release and smooth muscle excitation-contraction coupling. While the relationship between RyR activation and contraction is well characterized in arteries, little is known about the role of RyR in excitation-contraction coupling in veins. We hypothesized that RyR are present and directly coupled to contraction in rat aorta (RA) and vena cava (RVC). RA and RVC expressed mRNA for all 3 RyR subtypes, and immunofluorescence showed RyR protein was present in RA and RVC smooth muscle cells. RA and RVC rings contracted when Ca(2+) was re-introduced after stores depletion with thapsigargin (1μM), indicating both tissues contained intracellular Ca(2+) stores. To assess RyR function, contraction was then measured in RA and RVC exposed to the RyR activator caffeine (20mM). In RA, caffeine caused contraction that was attenuated by the RyR antagonists ryanodine (10μM) and tetracaine (100μM). However, caffeine (20mM) did not contract RVC. We next measured contraction and intracellular Ca(2+) (Ca(2+)(i)) simultaneously in RA and RVC exposed to caffeine. While caffeine increased Ca(2+)(i) and contracted RA, it had no significant effect on Ca(2+)(i) or contraction in RVC. These data suggest that ryanodine receptors, while present in both RA and RVC, are inactive and uncoupled from Ca(2+) release and contraction in RVC.

Effect of electrical stimulation on protease activity and tenderness of M. longissimus from cattle with different proportions of Bos indicus content

The effect of electrical stimulation on protease activity (at approx. 3 h postmortem), sensory tenderness scores and shear force was determined on M. longissimus samples from three Bos indicus genotypes (0% Hereford, 50% Brahman×Hereford and 100% Brahman). The samples were divided and aged for 1 or 30 days. Electrical stimulation resulted in a general reduction in calpastatin activity suggesting that it accelerated proteolysis. Calpastatin activity increased commensurate with increasing Bos indicus content. Several significant interactions were shown, the most relevant of these was the interaction between Bos indicus content×electrical stimulation. In contrast to the other genotypes, calpain I and calpain II activities were shown to increase (significant for calpain II only) following stimulation in the purebred Brahmans (100%). There was a significant reduction in tenderness with increasing Bos indicus content. However, breed differences in shear force were reduced by electrical stimulation. The improvement in shear force following ageing was smaller for stimulated carcasses compared to the controls. This tends to reinforce the premise that electrical stimulation accelerates proteolysis. The results of this study show clear genotypic differences in proteolytic activity and tenderness. However, electrical stimulation can be employed to reduce breed differences in tenderness of the M. longissimus.