Heel Skin Research Articles

Contact Pressures of the Posterior Heel in Lower Extremity Splints: A Biomechanical Study

Category: Basic Sciences/Biologics; Trauma Introduction/Purpose: Immobilization using lower extremity splints is a ubiquitous tool in orthopaedic care in the emergency department, operating room, and outpatient clinic settings. Prolonged use of these splints may result in skin changes or ulceration of the heel if not padded or positioned correctly. There is currently no biomechanical study in the literature measuring posterior heel contact pressure in lower extremity splints. The purpose of our study is to measure the contact pressure differences in the posterior heel with increasing layers of cotton padding, with and without the heel floating. We hypothesize that increased layers of padding will decrease contact pressure, but improvement will plateau. We predict that floating the heel will also considerably offload contact pressure. Methods: Short leg splints were applied to six limbs in three healthy subjects with an underlying pressure transducer (Tekscan I-Scan system) on the skin surface of the posterior heel. Peak contact pressures were measured after 0, 2, 4, and 6 layers of cotton padding were applied behind the heel in positions both with and without the heel freely floating. Each limb served as their own control, as pressure changes were compared to each limb’s baseline measurement (splint applied with all padding removed). Results: Over a 3-fold decrease in peak contact pressure was observed after the application of 4 or 6 layers of cotton padding. This escalated to over a 6-fold decrease with 2, 4, or 6 layers of padding while the splint was positioned with the heel freely floating. Splints with 4 and 6 layers of padding decreased heel contact pressure similarly (reduced to 29% and 28% from baseline, respectively), improved from 2 layers of padding (51% decrease from baseline). The mean contact pressure with 6 layers of padding (28% from baseline) remained higher than the mean contact pressure with 0 layers of padding with the heel floating (21% from baseline). Conclusion: Lower extremity splints with 4 or 6 layers of cotton padding provided a meaningful decrease in peak posterior heel contact pressure. The greatest decrease in heel contact pressure was observed in splints with the heel floating, even with all layers of cotton padding removed. This was more optimal than all layers of cotton padding tested. This study emphasizes the critical nature of patient counseling regarding the importance of proper splint positioning with the heel floating when at rest. Neglecting to do so may put the patient at increased risk for posterior heel skin complications.

Effect of Pressure Loading on Heel Skin Temperature and Moisture in Healthy Volunteers: Preliminary Results.

Recent studies emphasize the significance of skin microclimate in the prevention of pressure injuries (PI). The objective was to evaluate the effect of pressure loading on skin temperature and moisture in the heels of healthy adults. This is a before-and-after study performed at Brazil, in October 2022. Skin temperature (°C) was measured by an infrared digital thermometer, and skin moisture (%) using electrical bioimpedance. Ten individuals/twenty heels were evaluated. The average temperature of the right and left heel was the same at baseline (27.2 °C). It was recognized that after 30 min of pressure loading on the heels, there was a decrease in temperature, and after 15 min of pressure offloading, the temperature decreased again. It was found that at t0, the moisture of the right heel (12.6%) was lower than the left heel (15.6%). The median moisture in the right heel increased from t0 to t1 and decreased in t2, while in the left heel, there was a small variation of the median from t0 to t1, as well as to t2. The pressure loading leads to a decrease in temperature and changes the skin moisture of the heels of healthy individuals.

A mosquito proboscis-inspired cambered microneedle patch for ophthalmic regional anaesthesia

IntroductionOne of the methods for pain management involves the use of local anesthesia, which numbs sensations in specific body regions while maintaining consciousness. ObjectivesConsidering the certain limitations (e.g., pain, the requirement of skilled professionals, or slow passive diffusion) of conventional delivery methods of local anesthetics, developing alternative strategies that offer minimally invasive yet therapeutically effective delivery systems is of great concern for ophthalmic regional anesthesia. Methods and resultsIn this study, a rapidly dissolving cambered microneedle (MNs) patch, composed of poly(vinylpyrrolidone) (PVP) and hyaluronic acid (HA) and served as a delivery system for lidocaine (Lido) in local anesthesia, was developed taking inspiration from the mosquito proboscis’s ability to extract blood unnoticed. The lidocaine-containing MNs patch (MNs@Lido) consisted of 25 microneedles with a four-pronged cone structure (height: 500 μm, base width: 275 μm), arranged in a concentric circle pattern on the patch, and displays excellent dissolubility for effective drug delivery of Lido. After confirming good cytocompatibility, MNs@Lido was found to possess adequate rigidity to penetrate the cornea without causing any subsequent injury, and the created corneal pinhole channels completely self-healed within 24 h. Interestingly, MNs@Lido exhibited effective analgesic effects for local anesthesia on both heel skin and eyeball, with the sustained anesthetic effect lasting for at least 30 min. ConclusionsThese findings indicate that the mosquito proboscis-inspired cambered MNs patch provides rapid and painless local anesthesia, overcoming the limitations of conventional delivery methods of local anesthetics, thus opening up new possibilities in the treatment of ophthalmic diseases.

Effects of a mattress cover with special airflow technology on the structure and function of the sacral and heel skin during loading: A two-arm exploratory crossover trial.

Prolonged mechanical loading of the skin and underlying soft tissue cause pressure ulceration. The use of special support surfaces are key interventions in pressure ulcer prevention. They modify the degree and duration of soft tissue deformation and have an impact on the skin microclimate. The objective of this randomized cross-over trial was to compare skin responses and comfort after lying for 2.5 h supine on a support surface with and without a coverlet that was intended to assist with heat and moisture removal at the patient/surface interface. In addition, physiological saline solution was administered to simulate an incontinence episode on the mattress next to the participants' skin surface. In total, 12 volunteers (mean age 69 years) with diabetes mellitus participated. After loading, skin surface temperature, stratum corneum hydration and skin surface pH increased, whereas erythema and structural stiffness decreased at the sacral area. At the heel skin area, temperature, erythema, and stratum corneum hydration increased. These results indicate occlusion and soft tissue deformation which was aggravated by the saline solution. The differences in skin response showed only minor differences between the support surface with or without the coverlet.

Heel skin microclimate control: Secondary analysis of a self-controlled randomized clinical trial

Objectivethis study was undertaken to evaluate the efficacy of multilayer polyurethane foam with silicone (MPF) compared to transparent polyurethane film (TPF) dressings in the control of heel skin microclimate (temperature and moisture) of hospitalized patients undergoing elective surgeries. Methodthe study took of a secondary analysis of a randomized self-controlled trial, involving patients undergoing elective surgical procedure of cardiac and gastrointestinal specialties in a university hospital in southern Brazil, from March 2019 to February 2020. Patients served as their own control, with their heels randomly allocated to either TPF (control) or MPF (intervention). Skin temperature was measured using a digital infrared thermometer; and moisture determined through capacitance, at the beginning and end of surgery. The study was registered in the Brazilian Registry of Clinical Trials: RBR-5GKNG5. Resultssignificant difference in the microclimate variables were observed when the groups (intervention and control) and the timepoint of measurement (beginning and end of surgery) were compared. When assessing temperature, an increase (+3.3 °C) was observed with TPF and a decrease (−7.4 °C) was recorded with MPF. Regarding skin moisture, an increase in moisture (+14.6 AU) was recorded with TPF and a slight decrease (−0.3 AU) with MPF. ConclusionsThe findings of this study suggest that MPF is more effective than TPF in controlling skin microclimate (temperature and moisture) in heels skin of hospitalized patients undergoing elective surgeries. However, this control should be better investigated in other studies.

Age changes of foot microbiome estimated by microscopy method.

Despite of great number of investigations in the area of tinea pedis, question is opened: to what extent dermatophyte fungi are spread among modern population and does their occurrence interrelated with host age? Investigated group included 99 volunteers from 14 to 73 years old. Skin scales were collected from heel area of foot, and signs of heel skin trouble were expressed in points. In contrast to usual laboratory microscope magnification x900 we worked at x1750, what allowed to estimate not only fungal, but bacterial forms too. Average abundances of microbial morphotypes were expressed in points. Heel skin trouble increased in the process of aging (Pirsons` coefficient r=0.954). Bacilli occurred in all persons independently from age, but their abundance increased with aging (0.821). On the contrary cocci were more common and abundant in young person`s feet (-0.620). Occurrence of dermatophytes increased with age (0.891), at that relatively high values took place in young persons (10.5% with mycelium and 73.7% with spores) and in group without any heel skin trouble symptoms (7.7% and 76.9%), what allow to refer these fungi to normal habitats of foot skin.

Medial plantar artery flap

Background: The unique ability of the thick glabrous skin of the plantar heel to withstand body weight while also providing protective sensory feedback makes soft-tissue coverage of the plantar heel a particularly challenging aspect of foot reconstruction. In this study, we present the outcomes and complications associated with medial plantar artery perforator (MPAP) flap reconstruction of plantar heel. Methods: The study was a retrospective study conducted over four years, and included 22 patients with soft-tissue injury to the plantar heel. All patients underwent MPAP flap for coverage of the defect. We studied the mode of injury, defect size, flap size, duration of the procedure, complications associated with the flap and donor site, time to full weight bearing and return of protective sensation and 2-point discrimination in comparison with opposite heel. Results: We studied 22 cases with soft-tissue defects of the heel that included post-traumatic defects (7), non-healing diabetic ulcers (6), trophic ulcers (4) and post- tumor excision defects (melanoma-3, squamous cell carcinoma-2). Mean flap dimension was 24 sq.cm. 18 flaps had complete survival, while 2 flaps had necrosis of the distal edge and 2 flaps underwent complete necrosis.

Relapsed boyhood tibia polymicrobial osteomyelitis linked to dermatophytosis: a case report

BackgroundRelapsed childhood polymicrobial osteomyelitis associated with dermatophytosis has not been reported in the literature.Case presentationHere we report on a case of a 45-year-old man who had left tibial osteomyelitis for 29 years, accompanied by skin fungal infection of the ipsilateral heel for 20 years, and underwent a second operation due to recurrence of polymicrobial infection 6 years ago. The patient had a history of injury from a rusty object, which penetrated the anterior skin of the left tibia middle segment causing subsequent bone infection, but was asymptomatic after receiving treatments in 1983. The patient was physically normal until dermatophytosis occurred on the ipsilateral heel skin in 1998. The patient complained that the dermatophytosis was gradually getting worse, and the tibial wound site became itchy, red, and swollen. The left tibial infection resurged in May 2012, leading to the patient receiving debridement and antibiotic treatment. H&E and Gram-stained histology was performed on biopsy specimens of sequestrum and surrounding inflammatory tissue. Tissue culture and microbiology examination confirmed polymicrobial infection with Staphylococcus aureus (S. aureus) and Corynebacterium and a fungus. Additionally, the patient also received potassium permanganate for dermatophytosis when he was admitted into the hospital.ConclusionsTogether with longitudinal follow-up of medical history, surgical findings, histopathological and microbiology culture evidence, we conclude that boyhood tibia polymicrobial osteomyelitis with S. aureus and Corynebacterium occurred in this patient, and the fungal activation of dermatophytosis may have led to osteomyelitis relapse.

Imaging study and clinical application of peroneal perforating chimeric tissue flap

To explore the feasibility of peroneal perforating chimeric tissue flap in repairing the composite defects of calf and heel based on lower limb angiography, and the clinical effect. The digital subtraction angiography images of lower limbs of 50 patients met the selection criteria between May 2011 and October 2014 were used as the research object to observe the course of peroneal artery and its perforating vessels. Based on the observation results, between April 2015 and October 2020, the peroneal perforating chimeric tissue flap was designed to repair 7 cases of composite defects of the calf and heel. There were 5 males and 2 females with an average age of 38 years (range, 25-55 years). The causes of injury included traffic accident in 4 cases, falling from height in 2 cases, and machine strangulation in 1 case. There were 5 cases of calf skin defect and tibial defect. The size of skin defect ranged from 5 cm×3 cm to 11 cm×7 cm, and the length of bone defect was 5-8 cm. There were 2 cases of heel skin defect and calcaneal defect. The sizes of skin defects were 5.0 cm×4.0 cm and 7.5 cm×6.5 cm, and the bone defects were 3.0 cm×2.6 cm and 4.0 cm× 3.0 cm. For the calf defect, the size of skin flap ranged from 6 cm×4 cm to 12 cm×8 cm, and the length of the fibula was the same as that of the tibial defect. For the heel defect, the sizes of the skin flaps were 8.5 cm×5.5 cm and 13.0 cm×5.0 cm, and the lengths of the fibulae were 10 cm and 12 cm. Free transplantation was performed in 5 cases and pedicle transplantation in 2 cases. The wound at donor site was repaired with skin grafting or sutured directly. The peroneal artery ran close to the fibula 7.25-8.40 cm below the fibula head and send out 5-7 perforating vessels, with an average of 6.5 vessels. Perforating vessels mainly appeared in four places, which were (9.75±0.91), (13.21±0.74), (18.15±1.22), and (21.40±0.75) cm below the fibular head, with the occurrence rates of 94%, 90%, 96%, and 88%, respectively. Clinical application of 7 cases of peroneal perforating chimeric tissue flap all survived, all wounds healed by first intention. The skin graft at donor site survived and the incision healed by first intention. All patients were followed up 6-36 months, with an average of 12 months. Peroneal perforator chimeric tissue flap had good shape and soft texture. X-ray films showed that the bone graft healed well, and the healing time was 6-11 months (mean, 7 months). No obvious bone resorption was observed during follow-up. Five patients had no pain when walking, and 1 had mild pain with claudication. Postoperative heel ulcers formed in 1 case and healed after wearing custom plantar pressure dispersing shoes. At 6 months after operation, 2 patients were rated as grade Ⅳ and 5 patients as grade Ⅴ according to Holden walking function score. The peroneal perforating vessel distribution is constant and the peroneal perforating chimeric tissue flap is safe and reliable for repairing the composite defects of calf and heel.

Associations between skin structural and functional changes after loading in healthy aged females at sacral and heel skin: A secondary data analysis

Aim of the studyMechanical loading causes skin occlusion and deformation, which influences structural and functional skin properties. Aims of the study were to measure structural and functional skin parameters after loading at the sacral and heel skin and to describe possible associations. Material and methodsA secondary data analysis based on a clinical trial with n = 15 aged women was conducted. Changes of transepidermal water loss, stratum corneum hydration, epidermal hydration, erythema, temperature, structural stiffness, elastic recovery, elastic function, and mean roughness after 120 min loading were described and compared. Spearman's rho (rs) was used to estimate possible associations. ResultsLoading caused an increase of transepidermal water loss, stratum corneum and epidermal hydration, erythema and temperature at sacral and heel skin. There was a decrease of median roughness at the heel skin surface (-8.5 (IQR -10.5 to 5.5) μm). Strongest positive associations were observed between changes of elastic function and elastic recovery (rs = 0.9 at heel and sacral skin) and between changes of epidermal and stratum corneum hydration at both skin areas (rs = 0.7 at sacral skin and rs = 0.5 at the heel). ConclusionTwo hours loading on a standard foam mattress leads to skin occlusion at the skin surface and mechanical deformation. Skin occlusion seems primarily to increase temperature, stratum corneum and epidermal hydration that may affect mechanical skin properties. Mechanical deformation seems to be responsible for the erythematous response of the dermal skin layer.

MR-compatible loading device for assessment of heel pad internal tissue displacements under shearing load.

In the last decade, the role of shearing loads has been increasingly suspected to play a determinant impact in the formation of deep pressure ulcers. In vivo observations of such deformations are complex to obtain. Previous studies only provide global measurements of such deformations without getting the quantitative values of the loads that generate these deformations. To study the role that shearing loads have in the etiology of heel pressure ulcers, an MR-compatible device for the application of shearing and normal loads was designed. Magnetic resonance imaging is a key feature that allows to monitor deformations of soft tissues after loading in a non-invasive way. Measuring applied forces in an MR-environment is challenging due to the impossibility to use magnetic materials. In our device, forces are applied through the compression of springs made of polylactide. Shearing and normal loads were applied on the plantar skin of the human heel through a flat plate while acquiring MR images. The device materials did not introduce any imaging artifact and allowed for high quality MR deformation measurements of the internal components of the heel. The obtained subject-specific results are an original data set that can be used in validations for Finite Element analysis and therefore contribute to a better understanding of the factors involved in pressure ulcer development.

Anterolateral Thigh and Vascularized-tensor Fascia Lata Flaps for Long-gap Achilles Tendon Reconstruction.

Summary:We demonstrated our surgical technique of 8-cm segmental loss Achilles tendon reconstruction and repair of posterior heel skin and soft tissue defects with composite anterolateral thigh and 4-layer folding vascularized-tensor fasciae latae flaps of a 15-year-old adolescent boy’s post-traumatic injury and infection after primary repair. This technique highlights the ease of harvesting the flap, short operative time, and facilitation of the strong and sustainable motion of the Achilles tendon after reconstruction.

Effects of loading and prophylactic dressings on the sacral and heel skin: An exploratory cross-over trial.

Pressure ulcers/injuries are caused by sustained loading and deformation of skin and underlying soft tissues. Prophylactic dressings are recommended as an adjunct to other preventive measures such as repositioning and offloading. The aim of this study was to investigate the effects of prophylactic soft silicone multi‐layered foam dressings on the skin structure and function of the two most common pressure areas, sacrum and heel, with and without loading. An exploratory randomised cross‐over trial using intra‐individual comparisons was conducted. Eight healthy volunteers (mean age 27.5 years) were assigned to three groups and either spent 2.5 hours on a standard hospital mattress lying in supine position with and without dressings or spent 2.5 hours with dressings applied but without loading. Skin temperature, stratum corneum, and epidermal hydration increased in all groups irrespective of wearing a dressing and/or loading. Mean roughness decreased at the heels. Reactive hyperaemia and the release of interleukin 1 alpha were associated with loading only. Results suggest that the occlusive effects of dressings are similar or only slightly greater than those observed with non‐loading or loading without dressings. Thus, a dressing does not cause additional irritation or skin changes during loading but it may reduce the inflammatory response.

Pediatric Calcaneal Tuberosity Avulsion Fracture: A Case Report and Literature Review

Introduction: Calcaneus fractures are rare in the pediatric population, and avulsion fracture of the calcaneal tuberosity is even less common. In adults, those fractures are usually associated with poor bone quality, however, this is not the case in children. It is a fracture that requires emergent intervention to prevent devastating skin and soft-tissue-related complications. Case Report: We report a case of a 9-year-old female who had a displaced calcaneal tuberosity fracture with heel skin impending compromise, after a fall at an indoor gymnastic facility. The child had a history of acute lymphoblastic leukemia, diagnosed at age 4, she was in remission at the time of injury. In the present report, besides reporting a rare injury among the pediatric population, we also describe the operative management, the post-operative course, and we review the literature. Conclusion: Pediatric calcaneal tuberosity fractures, although rare, can lead to devastating complications if not addressed promptly, and should be treated in an expedited fashion. Keywords: Pediatric, calcaneal tuberosity, skin compromise.

Reliability and agreement of instrumental skin barrier measurements in clinical pressure ulcer prevention research.

In skin and wound research the instrumental measurement of skin function is established. Despite the widespread use, empirical evidence about measurement errors is widely lacking. The aim of this study was to measure reliability and agreement of skin temperature, transepidermal water loss, epidermal hydration, and erythema at the heel and sacral skin. Four experienced researchers performed skin measurements in 15 subjects. Lowest reliability was observed for transepidermal water loss at the sacral skin (ICC (1) 0.46 (95% CI 0.00‐0.78)) and highest for skin temperature at the heel skin (ICC (1) 0.99 (95% CI 0.99‐1.00)). Lowest Standard Errors of Measurement were calculated for skin temperature measurements at the heels (0.11°C) and highest for erythema measurements at the sacral skin (26.7 arbitrary units). There was a clear association between variability of estimates and reliability coefficients. Single measurements of skin temperature, stratum corneum, and epidermal hydration at the sacral and heel skin areas can be used in clinical research and practice. Means of at least two measurements should be used for estimating transepidermal water loss and erythema. Evidence is needed to inform researchers about relative and absolute measurement errors of commonly applied instruments and measurements in skin and wound research.

Tongue-Type Calcaneal Fracture due to a Low-Energy Injury

Tongue-type fractures are unusual calcaneal fractures that produce an unique and relatively uncommon injury pattern to the bone and soft tissues, due to the separation of the calcaneal tuberosity into superior and inferior fragments. The displacement of the superior fragment has the potential to tent the skin of the posterior heel and, if not treated emergently, partial or full-thickness skin breakdown can progress quickly, and potential necrosis can occur.

The evaluation of the tendon and muscle changes of lower extremity in patients with acromegaly.

Although it is well known that acromegaly causes enlargement in the extremities, studies investigating the effects of acromegaly on tendons, muscles and soft tissue are limited. The aims of our study were to investigate tendons, the presence of enthesitis, soft tissue, muscle groups in terms of thickness and pennation angle (PA) which is an indicator of microstructure and strength of the muscle, of the lower extremities. Thirty-nine patients with acromegaly and thirty-nine healthy control subjects similar for age, sex and body mass index were enrolled. Lower extremity tendons, skin, muscle groups were evaluated by ultrasound. The thicknesses of heel skin, heel pad, plantar fascia and Achilles tendon were higher in acromegaly than the control group (p < 0.05). The incidence of Achilles enthesitis were increased in the acromegaly group (p < 0.05). The thicknesses of the gastrocnemius medial head, vastus medialis, lateralis muscles for both sides and the left rectus femoris muscle were found to be lower in the acromegaly patients than controls (p < 0.05). However, thicknesses of vastus intermedius, gastrocnemius lateral head and soleus were similar between the acromegaly and control groups (p > 0.05). PA values of the right and left vastus medialis and the right vastus lateralis were found to be decreased in the acromegaly group (p < 0.05). Myostatin levels were lower in acromegaly group (p < 0.05). Acromegaly may cause to an increase in tendon and soft tissue thickness, enthesitis formation, decrease in the thickness of some muscles, and deterioration in microstructures in lower extremity.

Effects of Kakato-tsurutsuru socks on dry heels in healthy volunteer subjects.

Kakato-tsurutsuru (Kt) socks have been selling for almost 30years in Japan. Wearers claim they improve heel dryness despite no scientific evidence. We investigated the effects of Kt socks on heel dryness by questionnaire, clinical scores and non-invasive skin measurements. In a double-blind, randomized cross-over study, 10 healthy volunteers wore control or Kt socks over 2weeks in sequence for 4weeks. Skin hydration and evaporation of the medial and dorsal heel were measured before and every week during the trial. Clinical evaluations of desquamation and cracked skin were scored by a dermatologist. A visual analog scale (VAS) questionnaire of comfort, sock climate humidity and skin dryness was conducted. The VAS of comfort was significantly higher in Kt than controls. Average Δskin dryness in control and Kt groups was -1.63 and 2.22, respectively, showing a significant improvement. In the clinical findings of the dorsal side of the heel, Δdesquamation and Δcracked skin scores were significantly decreased and Δstratum corneum hydration significantly increased in Kt compared with controls. Kt socks may retain evaporated sweat with components of natural moisturizing factors, supporting the water-holding ability of the heel stratum corneum. These findings suggest that Kt socks may improve heel skin dryness.

Chronological changes in rat heel skin following depressurization of pressure ulcer-like dermal lesions

In our previous study, we proposed an animal model in which pressure ulcer-like dermal lesions can be produced by denervation of the sciatic nerve and application of a pressure load to rat heel skin. In the present study, we divided these animals into non-treated and pressure loading groups, and initiated hindlimb unloading (depressurization) by tail suspension at 1, 3, 5, 7, and 14 days after inflicting lesions (1–14d pressurization groups). Chronological changes in heel lesions were examined morphologically in all treatment groups after 1, 3, 7, 14, 28, and 40 days. Open dermal lesions were formed by 14 days in the loading group and numerous macrophages were present. In the 14d pressurization group, numerous macrophages were still distributed in and around lesions and Vascular endothelial cell growth factor (VEGF) expression was strongly detected by 3 days, but a thin germinal layer began to appear and CD68-positive macrophages and VEGF immunoreactions decreased gradually by 7 days later. By 14 days after depressurization, the germinal layer was repaired, and macrophages and immunoreactions of VEGF were similar to those of non-treated skin. These chronological changes were similar to those in human pressure ulcers, but from 5d after depressurization, different chronological changes were observed. Specifically, epidermis was thickened and macrophages were hardly detected at 5 days in the loading group, but the epidermis disappeared by 1 day in the 5d pressurization group. Subsequently, numerous macrophages aggregated and VEGF expression was increased by 3 days, and the remaining healing process was similar to that in the 14d pressurization group. Even when unloading was performed during the early stages (5d pressurization group), the epidermis disappeared and macrophages were then distributed before repair of the lesion was observed. These results suggest that earlier migration of macrophages to skin lesions might be associated with rapid wound healing.

A Differential Innate Immune Response in Active and Chronic Stages of Bovine Infectious Digital Dermatitis.

Digital dermatitis (DD) commonly associated with Treponema spp. infection is a prevalent infectious bovine foot disease characterized by ulcerative and necrotic lesions. Lesions associated with DD are often classified using the M-stage scoring system, with M0 indicating healthy heel skin and M4 indicating chronic lesions. Current treatments utilizing antimicrobials or chemical footbaths are often ineffective and rarely cure DD lesions. Understanding the function of the innate immune response in the pathogenesis of DD will help to identify novel therapeutic approaches. In this study, the expression of the local innate host defense peptides cathelicidins and β-defensins was investigated in cows with DD and associated with the presence of treponemes and inflammatory reactions. Samples from active ulcerative DD lesions (M2) had considerable epidermal neutrophilic infiltration and increased gene expression of β-defensin tracheal antimicrobial peptides compared to control skin. Samples from acute lesions also had elevated local Cxcl-8 and TLR4 gene expression and abundant treponemes as identified by direct visualization, immunohistochemistry, and culture. Conversely, the anti-inflammatory peptide IL-10 was elevated in skin from chronic (M4) lesions, whereas bovine cathelicidin myeloid antimicrobial peptide 28 (Bmap-28) was increased in skin from oxytetracycline-treated M2 lesions. Experiments using cultured human keratinocytes challenged with Treponema spp. isolated from clinical cases of bovine DD showed that structural products from treponemes are able to initiate the innate immune response, in part through TLR2 signaling. These findings indicate that neutrophil influx, Cxcl-8, and β-defensin are key markers of active DD. Cathelicidins and IL-10 seem important in response to treatment or during the chronic proliferative stages of the disease.