Attaching artificial Achilles and tibialis cranialis tendons to bone using suture anchors in a rabbit model: assessment of outcomes

Objective

The purpose of this study was to investigate the factors associated with outcomes of attaching artificial tendons to bone using suture anchors for replacement of biological tendons in rabbits.

Study Design

Metal suture anchors with braided composite sutures of varying sizes (USP #1, #2, or #5) were used to secure artificial tendons replacing both the Achilles and tibialis cranialis tendons in 12 New Zealand White rabbits. Artificial tendons were implanted either at the time of (immediate replacement, n=8), or four weeks after (delayed replacement, n=4) resection of the biological tendon. Hindlimb radiographs of the rabbits were obtained immediately after surgery and approximately every other week until the study endpoint (16 weeks post-surgery).

Results

All suture anchors used for the tibialis cranialis artificial tendons remained secure and did not fail during the study. The suture linkage between the Achilles artificial tendon and anchor failed in 9 of 12 rabbits. In all cases, the mode of failure was suture breakage distant from the knot. Based on radiographic analysis, the mean estimated failure timepoint was 5.3±2.3 weeks post-surgery, with a range of 2-10 weeks. Analysis of variance (ANOVA) tests revealed no significant effect of tendon implantation timing or suture size on either the timing or frequency of suture anchor failure.

Conclusion

Based on the mode of failure, suture mechanical properties, and suture anchor design, we suspect that the cause of failure was wear of the suture against the edges of the eyelet in the suture anchor post, which reduced the suture strength below in vivo loads. Suture anchor designs differed for the tibialis cranialis and did not fail during the period of study. Future studies are needed to optimize suture anchor mechanical performance under different loading conditions and suture anchor design features.

Replacement of tibialis cranialis tendon with polyester, silicone-coated artificial tendon preserves biomechanical function in rabbits compared to tendon excision only

BACKGROUND

Artificial tendons may be an effective alternative to autologous and allogenic tendon grafts for repairing critically sized tendon defects. The goal of this study was to quantify the in vivo hindlimb biomechanics (ground contact pressure and sagittal-plane motion) during hopping gait of rabbits having a critically sized tendon defect of the tibialis cranialis and either with or without repair using an artificial tendon.

METHODS

In five rabbits, the tibialis cranialis tendon of the left hindlimb was surgically replaced with a polyester, silicone-coated artificial tendon (PET-SI); five operated control rabbits underwent complete surgical excision of the biological tibialis cranialis tendon in the left hindlimb with no replacement (TE).

RESULTS

At 8 weeks post-surgery, peak vertical ground contact force in the left hindlimb was statistically significantly less compared to baseline for the TE group (p = 0.0215). Statistical parametric mapping (SPM) analysis showed that, compared to baseline, the knee was significantly more extended during stance at 2 weeks post-surgery and during the swing phase of stride at 2 and 8 weeks post-surgery for the TE group (p < 0.05). Also, the ankle was significantly more plantarflexed during swing at 2 and 8 weeks postoperative for the TE group (p < 0.05). In contrast, there were no significant differences in the SPM analysis among timepoints in the PET-SI group for the knee or ankle.

CONCLUSIONS

Our findings suggest that the artificial tibialis cranialis tendon effectively replaced the biomechanical function of the native tendon. Future studies should investigate (1) effects of artificial tendons on other (e.g., neuromuscular) tissues and systems and (2) biomechanical outcomes when there is a delay between tendon injury and artificial tendon implantation.

Hyperthyroid cats have altered pulmonary arterial hemodynamics but rarely have intermediate or high probability of pulmonary hypertension

OBJECTIVE

Apply the 3-site echocardiographic metrics utilized to assess pulmonary hypertension (PH) probability in dogs and humans to feline echocardiographic examinations to investigate the translatability of this scheme and subsequent enhancement of detection of PH in cats.

ANIMALS

27 client-owned cats (euthyroid [n = 11] and hyperthyroid [16]).

METHODS

This was a single-center, prospective, observational case-control study. Demographic, physical examination, and echocardiographic data from hyperthyroid and euthyroid cats were compared via Fisher exact test and Kruskal-Wallis test.

RESULTS

Hyperthyroid versus euthyroid cats had significantly greater right atrial area index values and were more likely to have late-peaking main pulmonary artery pulsed-wave flow profiles. Two hyperthyroid cats had measurable tricuspid regurgitation tracings (one with a high probability of PH and another with a low probability of PH).

CLINICAL RELEVANCE

Hyperthyroid cats demonstrated altered pulmonary arterial hemodynamics and lacked consistent intermediate or high probability of PH. The 3-site echocardiographic metrics scheme is applicable for the evaluation of right-sided cardiac and pulmonary arterial hemodynamics in cats. Further research is needed to determine reference ranges in larger populations of healthy cats and those with high clinical suspicion for PH.

In Vivo Assessment of High-Strength and Corrosion-Controlled Magnesium-Based Bone Implants

The biodegradable nature of magnesium in aqueous mediums makes it an attractive material for various biomedical applications when it is not recommended that the material stay permanently in the body. Some of the main challenges that hinder the use of magnesium for bone fracture repair are its limited mechanical strength and fast corrosion rates. To this end, we developed a novel Mg-Zn-Ca-Mn-based alloy and post-fabrication methods that can deliver high-strength and corrosion-controlled implant materials to address these challenges. This study is focused on assessing the in vitro corrosion and in vivo biocompatibility of the developed magnesium-based alloy and post-fabrication processes. The developed heat treatment process resulted in an increase in the microhardness from 71.9 ± 5.4 HV for the as-cast Mg alloy to as high as 98.1 ± 6.5 HV for the heat-treated Mg alloy, and the ceramic coating resulted in a significant reduction in the corrosion rate from 10.37 mm/yr for the uncoated alloy to 0.03 mm/yr after coating. The in vivo assessments showed positive levels of biocompatibility in terms of degradation rates and integration of the implants in a rabbit model. In the rabbit studies, the implants became integrated into the bone defect and showed minimal evidence of an immune response. The results of this study show that it is possible to produce biocompatible Mg-based implants with stronger and more corrosion-controlled properties based on the developed Mg-Zn-Ca-Mn-based alloy and post-fabrication methods.

Effect of polyester-based artificial tendons on movement biomechanics: A preliminary in vivo study

Artificial tendons may be valuable clinical devices for replacing damaged or missing biological tendons. In this preliminary study, we quantified the effect of polyester-suture-based artificial tendons on movement biomechanics. New Zealand White rabbits underwent surgical replacement of either the Achilles (n = 2) or tibialis cranialis (TC, n = 2) biological tendons with artificial tendons. Once pre-surgery and weekly from 2 to 6 weeks post-surgery, we quantified hindlimb kinematics and ground contact pressures during the stance phase of hopping gait. Post-surgical movement biomechanics were either consistent or improved over time in both groups. However, the Achilles group had greater overall biomechanical and muscle deficits than the TC group. In the TC group, at 6 weeks post-surgery, foot angles were about 10° greater than those in healthy controls during the first 30 % of stance. At 6 weeks post-surgery, the Achilles group exhibited lesser (i.e., more dorsiflexed) ankle angles (minimum angle = 31.5 ± 9.4°) and vertical ground reaction forces (37.4 ± 2.6 %BW) during stance than those in healthy controls (65.0 ± 11.2° and 50.2 ± 8.3 %BW, respectively). Future studies are needed to quantify long-term biomechanical function with artificial tendons, the effect of artificial tendons on muscle function and structure, and the effect of formal rehabilitation.

Corrigendum: In vitro and In vivo assessment of caprine origin Staphylococcus aureus ST398 strain UTCVM1 as an osteomyelitis pathogen

[This corrects the article DOI: 10.3389/fcimb.2022.1015655.].

In vitro and in vivo assessment of caprine origin Staphylococcus aureus ST398 strain UTCVM1 as an osteomyelitis pathogen

Staphylococcus aureus (SA) is a significant and well-recognized causative organism of bacterial osteomyelitis. Osteomyelitis is an inflammatory bone disease characterized by progressive bone destruction and loss. This disease causes significant morbidity and mortality to the patient and poses therapeutic challenges for clinicians. To improve the efficacy of therapeutic strategies to combat bacterial osteomyelitis, there is a need to define the molecular epidemiology of bacterial organisms more clearly and further the understanding of the pathogenesis of SA osteomyelitis. We conducted in vitro characterization of the pathogenic capabilities of an isolate of SA ST398 derived from a clinical case of osteomyelitis in a goat. We also report a rodent mandibular defect model to determine the ability of ST398 to cause reproducible osteomyelitis. Our results indicate that ST398 can invade and distort pre-osteoblastic cells in culture, induce significant inflammation and alter expression of osteoregulatory cytokines. We also demonstrate the ability of ST398 to induce osteomyelitis in a rat mandibular model. When compiled, these data support ST398 as a competent osteomyelitis pathogen.

Feasibility of Implanting a Foot–Ankle Endoprosthesis within Skin in a Rabbit Model of Transtibial Amputation

Prosthetic limbs that are completely implanted within skin (i.e., endoprostheses) could permit direct, physical muscle–prosthesis attachment to restore more natural sensorimotor function to people with amputation. The objective of our study was to test, in a rabbit model, the feasibility of replacing the lost foot after hindlimb transtibial amputation by implanting a novel rigid foot–ankle endoprosthesis that is fully covered with skin. We first conducted a pilot, non-survival surgery in two rabbits to determine the maximum size of the skin flap that could be made from the biological foot–ankle. The skin flap size was used to determine the dimensions of the endoprosthesis foot segment. Rigid foot–ankle endoprosthesis prototypes were successfully implanted in three rabbits. The skin incisions healed over a period of approximately 1 month after surgery, with extensive fur regrowth by the pre-defined study endpoint of approximately 2 months post surgery. Upon gross inspection, the skin surrounding the endoprosthesis appeared normal, but a substantial subdermal fibrous capsule had formed around the endoprosthesis. Histology indicated that the structure and thickness of the skin layers (epidermis and dermis) were similar between the operated and non-operated limbs. A layer of subdermal connective tissue representing the fibrous capsule surrounded the endoprosthesis. In the operated limb of one rabbit, the subdermal connective tissue layer was approximately twice as thick as the skin on the medial (skin = 0.43 mm, subdermal = 0.84 mm), ventral (skin = 0.80 mm, subdermal = 1.47 mm), and lateral (skin = 0.76 mm, subdermal = 1.42 mm) aspects of the endoprosthesis. Our results successfully demonstrated the feasibility of implanting a fully skin-covered rigid foot–ankle endoprosthesis to replace the lost tibia–foot segment of the lower limb. Concerns include the fibrotic capsule which could limit the range of motion of jointed endoprostheses. Future studies include testing of endoprosthetics, as well as materials and pharmacologic agents that may suppress fibrous encapsulation.

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

Osteomyelitis is an inflammatory bone disease typically caused by infectious microorganisms, often bacteria, which causes progressive bone destruction and loss. The most common bacteria associated with chronic osteomyelitis is Staphylococcus aureus. The incidence of osteomyelitis in the United States is estimated to be upwards of 50,000 cases annually and places a significant burden upon the healthcare system. There are three general categories of osteomyelitis: hematogenous; secondary to spread from a contiguous focus of infection, often from trauma or implanted medical devices and materials; and secondary to vascular disease, often a result of diabetic foot ulcers. Independent of the route of infection, osteomyelitis is often challenging to diagnose and treat, and the effect on the patient's quality of life is significant. Therapy for osteomyelitis varies based on category and clinical variables in each case. Therapeutic strategies are typically reliant upon protracted antimicrobial therapy and surgical interventions. Therapy is most successful when intensive and initiated early, although infection may recur months to years later. Also, treatment is accompanied by risks such as systemic toxicity, selection for antimicrobial drug resistance from prolonged antimicrobial use, and loss of form or function of the affected area due to radical surgical debridement or implant removal. The challenges of diagnosis and successful treatment, as well as the negative impacts on patient's quality of life, exemplify the need for improved strategies to combat bacterial osteomyelitis. There are many in vitro and in vivo investigations aimed toward better understanding of the pathophysiology of bacterial osteomyelitis, as well as improved diagnostic and therapeutic strategies. Here, we review the role of animal models utilized for the study of bacterial osteomyelitis and their critically important role in understanding and improving the management of bacterial osteomyelitis.

Magnetic Particle Imaging: Current and Future Applications, Magnetic Nanoparticle Synthesis Methods and Safety Measures

Magnetic nanoparticles (MNPs) have a wide range of applications; an area of particular interest is magnetic particle imaging (MPI). MPI is an imaging modality that utilizes superparamagnetic iron oxide particles (SPIONs) as tracer particles to produce highly sensitive and specific images in a broad range of applications, including cardiovascular, neuroimaging, tumor imaging, magnetic hyperthermia and cellular tracking. While there are hurdles to overcome, including accessibility of products, and an understanding of safety and toxicity profiles, MPI has the potential to revolutionize research and clinical biomedical imaging. This review will explore a brief history of MPI, MNP synthesis methods, current and future applications, and safety concerns associated with this newly emerging imaging modality.

Paediatric and perinatal HIV/AIDS in Jamaica an international leadership initiative, 2002-2007

BACKGROUND

Paediatric and Perinatal HIV/AIDS remain significant health challenges in the Caribbean where the HIV seroprevalence is second only to Sub-Saharan Africa.

METHOD

We describe a collaborative approach to the prevention, treatment and care ofHIVin pregnant women, infants and children in Jamaica. A team of academic and government healthcare personnel collaborated to address the paediatric and perinatal HIV epidemic in Greater Kingston as a model for Jamaica (population 2.6 million, HIV seroprevalence 1.5%). A five-point plan was utilized and included leadership and training, preventing mother-to-child transmission (pMTCT), treatment and care of women, infants and children, outcomes-based research and local, regional and international outreach.

RESULTS

A core group of paediatric/perinatal HIV professionals were trained, including paediatricians, obstetricians, public health practitioners, nurses, microbiologists, data managers, information technology personnel and students to serve Greater Kingston (birth cohort 20,000). During September 2002 to August 2007, over 69 793 pregnant women presented for antenatal care. During these five years, significant improvements occurred in uptake of voluntary counselling (40% to 91%) and HIV-testing (53% to 102%). Eight hundred and eighty-three women tested HIV-positive with seroprevalence rates of 1-2% each year The use of modified short course zidovudine or nevirapine in the first three years significantly reduced mother-to-child transmission (MTCT) of HIV from 29% to 6% (RR 0.27; 95%0 CI--0.10, 0.68). During 2005 to 2007 using maternal highly active antiretroviral therapy (HAART) with zidovudine and lamivudine with either nevirapine, nelfinavir or lopinavir/ritonavir and infant zidovudine and nevirapine, MTCT was further reduced to an estimated 1.6% in Greater Kingston and 4.75% islandwide. In five years, we evaluated 1570 children in four-weekly paediatric infectious diseases clinics in Kingston, St Andrew and St Catherine and in six rural outreach sites throughout Jamaica; 24% (377) had HIV/AIDS and 76% (1193) were HIV-exposed. Among the infected children, 79% (299 of 377) initiated HAART resulting in reduced HIV-attributable childhood morbidity and mortality islandwide. An outcomes-based research programme was successfully implemented.

CONCLUSION

Working collaboratively, our mission of pMTCT of HIV and improving the quality of life for families living and affected by HIV/AIDS in Jamaica is being achieved.

Evolving care of HIV-infected pregnant women in Jamaica--from nevirapine to HAART

BACKGROUND

The Ministry of Health, Jamaica, is scaling-up programmes to improve the health of HIV-positive pregnant women according to the modified WHO recommended preventative mother to child transmission (pMTCT) regimens of therapy based upon the mother's clinical and immunological status. Highly-active antiretroviral drugs (HAART) can result in successful pMTCT to < 1%. We report the clinical and immunological characteristics of HIV/AIDS in an era of evolving treatment and care of HIV-infected pregnant Jamaican women.

SUBJECTS AND METHOD

Clinical records were reviewed of patients registered in antenatal clinics in Greater Kingston and St. Catherine, Jamaica (annual birth cohort--20,000) between September 2002 and August 2006. Disease status was determined using the Centers for Disease Control and Prevention (CDC) classification system for adult HIV/AIDS. Demographic, clinical and laboratory data were documented and analyzed.

RESULTS

During the four-year period, 571 HIV-infected women were enrolled; 62% from Victoria Jubilee Hospital, 25% from Spanish Town Hospital and 13% from the University Hospital of the West Indies. Mean age was 27-29 (range 15-41) years, median parity was 2 (range 0-9) and 68-70% were unemployed. Ninety-five per cent had live births. CDC categories of illnesses were A--mild disease in 82% (n=473), B--moderate disease in 4.4% (n=24) and C--severe disease in 1.4% (n=8) while 12% (n=66) had insufficient data. During the first three years, CD4+ cell counts were evaluated in only 2.5% (10 of 406) of patients with median of 344 cells/microL, compared to CD4 evaluation in 50% (83 of 165 women) in the last year with median of573 cells/uL. Antiretroviral (ARV) medications primarily for pMTCT were given to 89% (n=506) ofwomen. Of these, uptake of HAART increased during years 1-3 from 2-3% to 62% in year four Within two years post-partum, 24 women died, 92% (n=22)from the direct complications of HIV/AIDS.

CONCLUSION

A comprehensive system of care of HIV in the peripartum period has been developed in Jamaica. Detailed medical evaluation during pregnancy is performed with modern guidelines and increasing laboratory availability of CD4+ cell counts and viral loads. We believe declining HIV infection rates in Jamaican infants and healthier mothers are a direct consequence of increased testing in pregnancy with early diagnosis and initiation of HAART-based pMTCT regimens in pregnant women.

Challenges and successes of HIV voluntary counselling and testing programme in antenatal clinics in greater Kingston, Jamaica

ISSUES

Voluntary counselling and testing (VCT) is a critical issue impacting HIV disease management from a national and global perspective. In Jamaica (population 2.6 million), 2% of women in antenatal clinics are HIV-positive and mother-to-child-transmission (MTCT) accounted for 7% of all reported cases in 2002. Notwithstanding this, VCT was ad hoc and not standardized. In 2003, a structured VCT programme was developed islandwide with over 300 VCT service providers and 16 qualified trainers.

DESCRIPTION

We describe the challenges and successes of VCT provided by five trained research nurses in the Perinatal HIV/AIDS Programme in Kingston which services 19,000 pregnant women per year in three major maternity centres and their 42 feeder antenatal clinics.

LESSONS LEARNED

The VCT model used was group education, opt-out individual testing, individual post-test counselling for seropositives and informing seronegatives of their negative status. Major challenges encountered included lack of quality control of the counselling process and lost opportunities for un-booked women who presented in labour However successes enjoyed included client assessment of risk behaviours with appropriate lifestyle changes, increased uptake of HIV testing and adherence to care for themselves and their infants, as well as reduction in stigma.

RECOMMENDATIONS

VCT has proven to be an important intervention that enabled improvement in the awareness, prevention and control of HIV in Jamaican pregnant women. Nurses who are appropriately trained in VCT can play a pivotal role in successful provision of VCT services.

Increasing prevalence of asthma diagnosis and symptoms in children is confined to mild symptoms

BACKGROUND

The prevalence of childhood asthma is increasing but few studies have investigated trends in asthma severity. We investigated trends in asthma diagnosis and symptom morbidity between an eight year time period in a paired prevalence study.

METHODS

All children in one single school year aged 8-9 years in the city of Sheffield were given a parent respondent questionnaire in 1991 and 1999 based on questions from the International Survey of Asthma and Allergy in Children (ISAAC). Data were obtained regarding the prevalence of asthma and wheeze and current (12 month) prevalences of wheeze attacks, speech limiting wheeze, nocturnal cough and wheeze, and exertional symptoms.

RESULTS

The response rates in 1991 and 1999 were 4580/5321 (85.3%) and 5011/6021 (83.2%), respectively. There were significant increases between the two surveys in the prevalence of asthma ever (19.9% v 29.7%, mean difference 11.9%, 95% confidence interval (CI) 10.16 to 13.57, p<0.001), current asthma (10.3% v 13.0%, mean difference 2.7%, 95% CI 1.44 to 4.03, p<0.001), wheeze ever (30.3% v 35.8%, mean difference 5.7%, 95% CI 3.76 to 7.56, p<0.001), wheeze in the previous 12 months (17.0% v 19.4%, mean difference 2.5, 95% CI 0.95 to 4.07, p<0.01), and reporting of medication use (16.9% v 20%, mean difference 3.0%, 95% CI 1.46 to 4.62, p<0.001). There were also significant increases in reported hayfever and eczema diagnoses.

CONCLUSIONS

Diagnostic labelling of asthma and lifetime prevalence of wheeze has increased. The current 12 month point prevalence of wheeze has increased but this is confined to occasional symptoms. The increased medication rate may be responsible for the static prevalence of severe asthma symptoms. The significant proportion of children receiving medication but reporting no asthma symptoms identified from our 1999 survey suggests that some children are being inappropriately treated or overtreated.