Potent drug delivery enhancement of betulinic acid and NVX-207 into equine skin in vitro - a comparison between a novel oxygen flow-assisted transdermal application device and microemulsion gels.

BACKGROUND: Gray horses are predisposed to equine malignant melanoma (EMM) with advancing age. Depending on the tumor's location and size, they can cause severe problems (e.g., defaecation, urination, feeding). A feasible therapy for EMM has not yet been established and surgical excision can be difficult depending on the location of the melanoma. Thus, an effective and safe therapy is needed. Naturally occurring betulinic acid (BA), a pentacyclic triterpene and its synthetic derivate, NVX-207 (3-acetyl-betulinic acid-2-amino-3-hydroxy-2-hydroxymethyl-propanoate) are known for their cytotoxic properties against melanomas and other tumors and have already shown good safety and tolerability in vivo. In this study, BA and NVX-207 were tested for their permeation potential into equine skin in vitro in Franz-type diffusion cell (FDC) experiments after incubation of 5 min, 30 min and 24 h, aiming to use these formulations for prospective in vivo studies as a treatment for early melanoma stages. Potent permeation was defined as reaching or exceeding the half maximal inhibitory concentrations (IC50) of BA or NVX-207 for equine melanoma cells in equine skin samples. The active ingredients were either dissolved in a microemulsion (ME) or in a microemulsion gel (MEG). All of the formulations were transdermally applied but the oil-in-water microemulsion was administered with a novel oxygen flow-assisted (OFA) applicator (DERMADROP TDA). RESULTS: All tested formulations exceeded the IC50 values for equine melanoma cells for BA and NVX-207 in equine skin samples, independently of the incubation time NVX-207 applied with the OFA applicator showed a significant time-dependent accumulation and depot-effect in the skin after 30 min and 24 h (P < 0.05). CONCLUSIONS: All tested substances showed promising results. Additionally, OFA administration showed a significant accumulation of NVX-207 after 30 min and 24 h of incubation. Further in vivo trials with OFA application are recommended.

Variable fixation promotes callus formation: an experimental study on transverse tibial osteotomies stabilized with locking plates.

BACKGROUND: A new locking screw technology, named variable fixation, has been developed aiming at promoting bone callus formation providing initial rigid fixation followed by progressive fracture gap dynamisation. In this study, we compared bone callus formation in osteotomies stabilized with standard locking fixation against that of osteotomies stabilized with variable fixation in an established tibia ovine model. METHODS: A 3 mm tibial transverse osteotomy gap was stabilized in three groups of six female sheep each with a locking plate and either 1) standard fixation in both segments (group LS) or 2) variable fixation in the proximal and standard fixation in the distal bone segment (group VFLS3) or 3) variable fixation in both segments (group VFLS6). The implantation site and fracture healing were compared between groups by means of radiologic, micro tomographic, biomechanical, and histological investigations. RESULTS: Compared to LS callus, VFLS3 callus was 40% larger and about 3% denser, while VFLS6 callus was 93% larger and its density about 7.2% lower. VFLS3 showed 65% and VFLS6 163% larger amount of callus at the cis-cortex. There wasn't a significant difference in the amount of callus at the cis and trans-cortex in groups featuring variable fixation only. Investigated biomechanical variables were not significantly different among groups and histology showed comparable good healing in all groups. Tissues adjacent to the implants did not show any alteration of the normal structure in all groups. CONCLUSIONS: Variable fixation promoted the formation of a larger amount of bone callus, equally distributed at the cis and trans cortices. The histological and biomechanical properties of the variable fixation callus were equivalent to those of the standard fixation callus. The magnitude of variable fixation had a biological effect on the formation of bone callus. At the implantation site, the usage of variable fixation did not raise additional concerns with respect to standard fixation. The formation of a larger amount of mature callus suggests that fractures treated with variable fixation might have a higher probability to bridge the fracture gap. The conditions where its usage can be most beneficial for patients needs to be clinically defined.

Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments.

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

A novel, non-adhesive, precipitating liquid embolic implant with intrinsic radiopacity: feasibility and safety animal study.

OBJECTIVES: To evaluate a novel, ready-to-use, iodinated polyvinyl alcohol polymer embolic implant. METHODS: Under good laboratory practice conditions, 26 pigs were investigated. A complex arteriovenous malformation (AVM) model was created in 16 animals, and a simple rete model was used in the remaining 10 animals. The novel material was used for embolization in 22 animals, and a commercially available liquid embolic material in 4 animals as a control group. Animals were killed at 2 days, 3 months and 6 months. Feasibility, efficacy and safety were evaluated radiologically, clinically and histologically. RESULTS: Preparation was easy, without risk of catheter clogging or adhesiveness. Embolic delivery was well controlled under subtracted fluoroscopy. Visibility was homogeneous throughout the injection and the material behaved cohesively upon delivery. Best lesion penetration was obtained with the use of proximal microballoon occlusion. Unforeseen over-dilution of the test material by DMSO prefilled in the microballoon hub changed the material properties and caused inadvertent cerebral embolization leading to death in five animals. This phenomenon was avoided by practical measures. The casts produced no beam-hardening artefacts on CT scans. Histology showed excellent biocompatibility. CONCLUSIONS: Embolization with this novel, iodinated, precipitating polymer was feasible and effective. Care should be taken during delivery to avoid over-dilution of the material by prefilled DMSO. The material is promising for embolization of AVMs and hypervascular lesions. KEY POINTS: • The intrinsically opaque precipitating polymer has adequate fluoroscopic visibility • The polymer does not induce shading or beam-hardening artefacts on CT • The novel liquid embolic material does not require lengthy preparation • Lack of implant adherence reduces the risk of entrapment of the delivery catheter.

Experimental evaluation of four airway devices in anaesthetized New Zealand White rabbits.

OBJECTIVE: To compare airway management during induction of anaesthesia, spontaneous ventilation (SV) and controlled mechanical ventilation (CMV), using an endotracheal tube (ETT), laryngeal mask (LM), rabbit-specific supraglottic airway device (v-gel) or facemask (FM). STUDY DESIGN: Prospective randomized crossover experiment. ANIMALS: Ten New Zealand White rabbits. METHODS: After premedication, rabbits were randomly allocated to four groups: 1) ETT; 2) LM; 3) v-gel or 4) FM. The required dose of propofol, duration and number of attempts to place an airway device and leakage during SV and CMV at different peak inspiratory pressures (6, 10, 12, 14 and 16 cmH2O) were recorded. Computed tomography (CT) of the head, neck and abdomen were performed before and after CMV. RESULTS: Significantly less propofol and time [2.0±0.5 mg kg-1, 82±34 seconds, p<0.001] were needed to place the FM compared to the three other groups [v-gel 5.1±2.1 mg kg-1, 302±124 seconds; LM 4.8±1.2 mg kg-1, 275±89 seconds; ETT 5.5±1.4 mg kg-1, 315±147 seconds]. A leak > 25% of the tidal volume occurred at the lowest pressure in FM [median (range), 6 (6-8) cmH2O], which was significantly lower than with v-gel [16 (6-no leak at 16) cmH2O], LM [>16 (6-no leak at 16)] or ETT [>16 (no leak at 16) cmH2O] (p<0.001). On CT images, the height and width of the larynx were significantly smaller with v-gel in comparison to FM and LM (p=0.004). A significant increase in the amount of gas in the stomach (p=0.007), but not gastric volume, was detected in FM and LM. CONCLUSIONS AND CLINICAL RELEVANCE: The v-gel is a practical alternative to LM and ETT for airway management and CMV, but can compress the larynx. The FM is easily placed, but significant leakage occurs during CMV.

Comparison of two dental implant surface modifications on implants with same macrodesign: an experimental study in the pelvic sheep model.

OBJECTIVES: The aim of this study was to compare two different surfaces of one uniform macro-implant design in order to focus exclusively on the osseointegration properties after 2, 4 and 8 weeks and to discuss the animal model chosen. MATERIAL AND METHODS: In six mature sheep, n = 36 implants with a highly crystalline and phosphate-enriched anodized titanium oxide surface (TiU) and n = 36 implants with a hydrophilic, sandblasted, large grit and acid-etched surface (SLA) were placed in the pelvic bone. TiU implants were custom-made to match the SLA implant design. The implant stability and bone-to-implant contact (BIC) were assessed by resonance frequency (ISQ), backscatter scanning electron microscopy (B-SEM), light microscopy (LM), micro-CT and intravital fluorochrome staining. Biomechanical removal torque testing was performed. RESULTS: Overall, no statistically significant differences in BIC total (trabecular + cortical) between TiU and SLA were found via LM and B-SEM. BIC values (B-SEM; LM) in both groups revealed a steady rise in trabecular bone attachment to the implant surface after 2, 4 and 8 weeks. In the 2- to 4-week time interval in the TiU group (P = 0.005) as well as in the SLA group (P = 0.01), a statistically significant increase in BIC trabecular could be observed via LM. B-SEM values confirmed the statistically significant increase for TiU (P = 0.001). In both groups, BIC trabecular values after 8 weeks were significantly higher (P ≤ 0.05) than after 2 weeks (B-SEM; LM). Biomechanical data confirmed the histological data. CONCLUSION: The two surfaces proved comparable osseointegration in this sheep model.

Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep.

OBJECTIVES: The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time. MATERIAL AND METHODS: In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group). RESULTS: Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5). CONCLUSION: Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found.

A new-generation, low-permeability flow diverting device for treatment of saccular aneurysms.

OBJECTIVES: We report a preclinical comparative study of a 96-strand braided flow diverter. METHODS: The 96-strand braided device was compared with the currently commercially available flow diverter with 48 strands. The devices were implanted across the neck of 12 elastase-induced aneurysms in New Zealand White rabbits and followed for 1 and 3 months (n = 6 respectively). Aneurysm occlusion rates, parent artery stenosis and patency of jailed branch occlusions were assessed by angiography, histology and scanning electron microscopy studies. RESULTS: It was feasible to navigate and implant the 96-strand device over the aneurysm orifice in all cases. At follow-up two aneurysms in the 48-strand vs. one in the 96-strand group were not occluded. This aneurysm from the 96-strand group however had a tracheal branch arising from the sac and showed a reverse remodelling of the vascular pouch at 3 months. In the occluded aneurysms, the parent artery was always completely reconstructed and the aneurysm orifice was sealed with neointimal tissue. No in-stent stenosis or jailed branch artery occlusion was observed. CONCLUSIONS: The 96-strand flow diverter proved to be safe, biocompatible and haemodynamically effective, induced stable occlusion of aneurysms and led to reverse remodelling of the parent artery. KEY POINTS: • Flow diversion has been introduced to improve endovascular treatment of cerebral aneurysms • A new low-permeability flow diverter is feasible for parent artery reconstruction. • The Silk 96 flow diverter appears effective at inducing aneurysm healing. • The covered branches remained patent at follow-up.

Poly(ADP-Ribose) Polymerases-Inhibitor Talazoparib Inhibits Muscle Atrophy and Fatty Infiltration in a Tendon Release Infraspinatus Sheep Model: A Pilot Study.

Structural muscle changes, including muscle atrophy and fatty infiltration, follow rotator cuff tendon tear and are associated with a high repair failure rate. Despite extensive research efforts, no pharmacological therapy is available to successfully prevent both muscle atrophy and fatty infiltration after tenotomy of tendomuscular unit without surgical repair. Poly(ADP-ribose) polymerases (PARPs) are identified as a key transcription factors involved in the maintenance of cellular homeostasis. PARP inhibitors have been shown to influence muscle degeneration, including mitochondrial hemostasis, oxidative stress, inflammation and metabolic activity, and reduced degenerative changes in a knockout mouse model. Tenotomized infraspinatus were assessed for muscle degeneration for 16 weeks using a Swiss Alpine sheep model (n = 6). All sheep received daily oral administration of 0.5 mg Talazoparib. Due to animal ethics, the treatment group was compared with three different controls from prior studies of our institution. To mitigate potential batch heterogeneity, PARP-I was evaluated in comparison with three distinct control groups (n = 6 per control group) using the same protocol without treatment. The control sheep were treated with an identical study protocol without Talazoparib treatment. Muscle atrophy and fatty infiltration were evaluated at 0, 6 and 16 weeks post-tenotomy using DIXON-MRI. The controls and PARP-I showed a significant (control p < 0.001, PARP-I p = 0.01) decrease in muscle volume after 6 weeks. However, significantly less (p = 0.01) atrophy was observed in PARP-I after 6 weeks (control 1: 76.6 ± 8.7%; control 2: 80.3 ± 9.3%, control 3: 73.8 ± 6.7% vs. PARP-I: 90.8 ± 5.1% of the original volume) and 16 weeks (control 1: 75.7 ± 9.9; control 2: 74.2 ± 5.6%; control 3: 75.3 ± 7.4% vs. PARP-I 93.3 ± 10.6% of the original volume). All experimental groups exhibited a statistically significant (p < 0.001) augmentation in fatty infiltration following a 16-week period when compared to the initial timepoint. However, the PARP-I showed significantly less fatty infiltration (p < 0.003) compared to all controls (control 1: 55.6 ± 6.7%, control 2: 53.4 ± 9.4%, control 3: 52.0 ± 12.8% vs. PARP-I: 33.5 ± 8.4%). Finally, a significantly (p < 0.04) higher proportion and size of fast myosin heavy chain-II fiber type was observed in the treatment group. This study shows that PARP-inhibition with Talazoparib inhibits the progression of both muscle atrophy and fatty infiltration over 16 weeks in retracted sheep musculotendinous units.

Studying Edema Formation After Release of the Infraspinatus Muscle as an Experimental Model of Rotator Cuff Lesions in Sheep: A Histological Analysis.

BACKGROUND: Muscle edema formation and inflammatory processes are early manifestations of acute rotator cuff lesions in sheep. Histological analysis of affected muscles revealed edema formation, inflammatory changes, and muscle tissue disruption in MRs. HYPOTHESIS: Edema contributes to inflammatory reactions and early muscle fiber degeneration before the onset of fatty infiltration. STUDY DESIGN: Controlled laboratory study. METHODS: Osteotomy of the greater tuberosity, including the insertion of the infraspinatus tendon, was performed on 14 sheep. These experimental animal models were divided into 2 groups: a nontrauma group with surgical muscle release alone (7 sheep) and a trauma group with standardized application of additional trauma to the musculotendinous unit (7 sheep). Excisional biopsy specimens of the infraspinatus muscle were taken at 0, 3, and 4 weeks. RESULTS: Edema formation was histologically demonstrated in both groups and peaked at 3 weeks. At 3 weeks, signs of muscle fiber degeneration were observed. At 4 weeks, ingrowth of loose alveolar and fibrotic tissue between fibers was detected. Fatty tissue was absent. The diameter of muscle fibers increased in both groups, albeit to a lesser degree in the trauma group, and practically normalized at 4 weeks. Immunohistology revealed an increase in macrophage types 1 and 2, as well as inflammatory mediators such as prostaglandin E2 and nuclear factor kappa-light-chain-enhancer of activated B cells. CONCLUSION: Early muscle edema and concomitant inflammation precede muscle fiber degeneration and fibrosis. Edema formation results from tendon release alone and is only slightly intensified by additional trauma. CLINICAL RELEVANCE: This study illustrates that early edema formation and inflammation elicit muscle fiber degeneration that precedes fatty infiltration. Should this phenomenon be applicable to human traumatic rotator cuff tears, then surgery should be performed as soon as possible, ideally within the first 21 days after injury.

Effects of shape and structure of a new 3D-printed personalized bioresorbable tracheal stent on fit and biocompatibility in a rabbit model.

To date, several types of airway stents are available to treat central airway obstructions. However, the ideal stent that can overcome anatomical, mechanical and microbiological issues is still awaited. In addition, therapeutic effect and self-elimination of these stents are desirable properties, which pose an additional challenge for development and manufacturing. We aimed to create a prototype bioresorbable tracheal stent with acceptable clinical tolerance, fit and biocompatibility, that could be tested in a rabbit model and in the future be further optimized to enable drug-elution and ensure local therapeutic effect. Twenty-one New Zealand White Rabbits received five different types of bioresorbable tracheal stents, 3D-printed from poly(D,L-lactide-co-ε-caprolactone) metacrylates. Various configurations were tested for their functionality and improved until the best performing prototype could undergo detailed in vivo assessment, regarding clinical tolerance, migration and biocompatibility. Previously tested types of 3D printed stents in our preliminary study required improvement due to several problems, mainly related to breakage, unreliable stability and/or migration within the trachea. Abandoned or refined pre-prototypes were not analyzed in a comparative way. The final best performing prototype stent (GSP2 (Group Stent Prototype 2), n = 8) allowed a transoral application mode and showed good clinical tolerance, minimal migration and acceptable biocompatibility. The good performance of stent type GSP2 was attributed to the helix-shaped surface structure, which was therefore regarded as a key-feature. This prototype stent offers the possibility for further research in a large animal model to confirm the promising data and assess other properties such as bioresorption.

Bone augmentation for cancellous bone- development of a new animal model.

BACKGROUND: Reproducible and suitable animal models are required for in vivo experiments to investigate new biodegradable and osteoinductive biomaterials for augmentation of bones at risk for osteoporotic fractures. Sheep have especially been used as a model for the human spine due to their size and similar bone metabolism. However, although sheep and human vertebral bodies have similar biomechanical characteristics, the shape of the vertebral bodies, the size of the transverse processes, and the different orientation of the facet joints of sheep are quite different from those of humans making the surgical approach complicated and unpredictable. Therefore, an adequate and safe animal model for bone augmentation was developed using a standardized femoral and tibia augmentation site in sheep. METHODS: The cancellous bone of the distal femur and proximal tibia were chosen as injection sites with the surgical approach via the medial aspects of the femoral condyle and proximal tibia metaphysis (n = 4 injection sites). For reproducible drilling and injection in a given direction and length, a custom-made c-shaped aiming device was designed. Exact positioning of the aiming device and needle positioning within the intertrabecular space of the intact bone could be validated in a predictable and standardized fashion using fluoroscopy. After sacrifice, bone cylinders (Ø 32 mm) were harvested throughout the tibia and femur by means of a diamond-coated core drill, which was especially developed to harvest the injected bone area exactly. Thereafter, the extracted bone cylinders were processed as non-decalcified specimens for µCT analysis, histomorphometry, histology, and fluorescence evaluation. RESULTS: The aiming device could be easily placed in 63 sheep and assured a reproducible, standardized injection area. In four sheep, cardiovascular complications occurred during surgery and pulmonary embolism was detected by computed tomography post surgery in all of these animals. The harvesting and evaluative methods assured a standardized analysis of all samples. CONCLUSIONS: This experimental animal model provides an excellent basis for testing new biomaterials for their suitability as bone augmentation materials. Concomitantly, similar cardiovascular changes occur during vertebroplasties as in humans, thus making it a suitable animal model for studies related to vertebroplasty.

Combined electric and magnetic field therapy for bone repair and regeneration: an investigation in a 3-mm and an augmented 17-mm tibia osteotomy model in sheep.

BACKGROUND: Therapies using electromagnetic field technology show evidence of enhanced bone regeneration at the fracture site, potentially preventing delayed or nonunions. METHODS: Combined electric and magnetic field (CEMF) treatment was evaluated in two standardized sheep tibia osteotomy models: a 3-mm non-critical size gap model and a 17-mm critical size defect model augmented with autologous bone grafts, both stabilized with locking compression plates. CEMF treatment was delivered across the fracture gap twice daily for 90 min, starting 4 days postoperatively (post-OP) until sacrifice (9 or 12 weeks post-OP, respectively). Control groups received no CEMF treatment. Bone healing was evaluated radiographically, morphometrically (micro-CT), biomechanically and histologically. RESULTS: In the 3-mm gap model, the CEMF group (n = 6) exhibited higher callus mineral density compared to the Control group (n = 6), two-fold higher biomechanical torsional rigidity and a histologically more advanced callus maturity (no statistically significant differences). In the 17-mm graft model, differences between the Control (n = 6) and CEMF group (n = 6) were more pronounced. The CEMF group showed a radiologically more advanced callus, a higher callus volume (p = 0.003) and a 2.6 × higher biomechanical torsional rigidity (p = 0.024), combined with a histologically more advanced callus maturity and healing. CONCLUSIONS: This study showed that CEMF therapy notably enhanced bone healing resulting in better new bone structure, callus morphology and superior biomechanical properties. This technology could transform a standard inert orthopedic implant into an active device stimulating bone tissue for accelerated healing and regeneration.

Osseointegration and biocompatibility of different metal implants--a comparative experimental investigation in sheep.

BACKGROUND: In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep. METHODS: Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically. RESULTS: Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials. CONCLUSION: This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.

Biodegradable sleeves for metal implants to prevent implant-associated infection: an experimental in vivo study in sheep.

OBJECTIVE: To evaluate biocompatibility of biodegradable sleeves containing antimicrobial agents, designed for local drug delivery to prevent implant-related infection. STUDY DESIGN: Synthetic polyester sleeves (a copolymer of glycolide, caprolactone, trimethylene carbonate, lactide) were cast as thin films. The antimicrobial agents incorporated in the sleeves included gentamicin sulfate, triclosan, or a combination of these drugs. ANIMALS: Adult sheep (n = 15). METHODS: Two limited contact dynamic compression plates (LC-DCP) with or without sleeves were implanted on tibiae (bilateral) of 15 sheep. Sleeves were placed over the plates before implantation. Beneath half of the plates, 5-mm drill hole defects were made in the near cortex. Samples were harvested 4 weeks later for histology and microradiography. RESULTS: Macroscopically, no irritation of bone or adjacent tissue was seen. Small remnants of sleeves were visible on histology, and positively correlated with the presence of macrophages and foreign body cells. Thick sections showed no difference between the test samples and controls in terms of fibrous capsule formation, periosteal remodeling, and defect remodeling. Inflammatory cells, macrophages, and foreign body cells were more prominent in sections with sleeves, but were not statistically significantly different from controls. Cell numbers were within normal physiologic limits normally seen as cellular response to foreign bodies consisting of polymers. CONCLUSION: The normal healing response indicated that the biodegradable sleeves demonstrate tissue biocompatibility.

Image-based radiodensity profilometry measures early remodeling at the bone-callus interface in sheep.

Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling.

Biomechanical duality of fracture healing captured using virtual mechanical testing and validated in ovine bones.

Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore rigidity to the bone. Virtual mechanical testing is a promising technique for image-based assessment of structural bone healing in both preclinical and clinical settings, but its accuracy depends on the validity of the material model used to assign tissue mechanical properties. The goal of this study was to develop a constitutive model for callus that captures the heterogeneity and biomechanical duality of the callus, which contains both soft tissue and woven bone. To achieve this, a large-scale optimization analysis was performed on 2363 variations of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep under normal and delayed healing conditions. A piecewise material model was identified that produced high absolute agreement between virtual and physical tests by differentiating between soft and hard callus based on radiodensity. The results showed that the structural integrity of a healing long bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. These findings suggest that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical biomechanical testing.

Effect of an Oxygen-Based Mechanical Drug Delivery System on Percutaneous Permeation of Various Substances In Vitro.

Transdermal drug administration is an elegant method to overcome various side effects of oral or parenteral drug administration. Nevertheless, due to an effective skin barrier, which is provided by the stratum corneum, transdermal drug delivery is sometimes very slow and ineffective. Thus, the effect of a medical device (DERMADROP TDA) for transdermal penetration of drugs in conjunction with a special vehicle emulsion on percutaneous permeation of several substances (with different physicochemical properties) was investigated in Franz-type diffusion cells with porcine skin over 28 h. This medical device disperses pharmaceutical agents via oxygen flow through an application system, which is used in conjunction with specially developed vehicle substances. Substance permeation of various substances with different physicochemical properties (diclofenac, enrofloxacin, flufenamic acid, indomethacin, and salicylic acid) was examined after application with a pipette and with the medical device. Therefore, acceptor media samples were collected up to 28 h after drug administration. Drug concentration in the acceptor medium was determined via high-performance liquid chromatography. Enhanced permeation was observed for diclofenac, enrofloxacin, flufenamic acid, indomethacin, and salicylic acid after oxygen-based administration. This correlates negatively with the molecular weight. Thus, drug administration can effectively be enhanced by a medical device using oxygen.

Studying Edema Formation After Release of the Infraspinatus Tendon as an Experimental Model of Rotator Cuff Tears in Sheep: A Preliminary Imaging and Morphological Analysis.

BACKGROUND: The cause, extent, and role of muscle edema for muscle degeneration are unknown and not considered in the current literature. In vivo experiments were designed to prove muscle edema formation in the early period in a sheep model of acute rotator cuff tears. HYPOTHESIS: Muscle edema occurs after tendon release with or without additional stretching trauma and may be associated with muscle retraction and subsequent muscle degeneration. STUDY DESIGN: Controlled laboratory study. METHODS: A sheep model with acute release of the infraspinatus tendon was used. An osteotomy of the greater tuberosity, including the insertion of the infraspinatus tendon, was performed in 14 sheep. To demonstrate presence of edema, magnetic resonance imaging scans were performed at 0, 2, and 4 weeks using T1-weighted, T2-weighted, proton density-weighted, and Dixon sequences. Excisional biopsy specimens were taken at 0, 3, and 4 weeks (histological results will be reported in a later publication). Two injury models were created: a nontrauma group that consisted of muscle release alone and a trauma group that included additional standardized traction to the musculotendinous unit. Evaluation of T1- and T2-weighted images included calculation of pennation angle, muscle fiber length, signal intensity (edema), and muscle volume. Muscle wet weight and volume were measured at sacrifice. RESULTS: Edema formation was shown in all sheep and slightly more pronounced in the trauma group, where muscle intensity increased significantly between time point 0 (200 Grey Value (GV)) and weeks 2, 3, and 4 (300 GV). Edema formation started early after tendon release with a plateau between 3 and 4 weeks. Deterioration of muscle fiber bundles began also after tendon release with a peak at 4 weeks. Muscle volume decreased steadily over time. CONCLUSION: Muscle edema appeared early after rotator cuff tendon release, was more pronounced in the trauma group, and reached a plateau after 3 to 4 weeks. Muscle fatty content decreased within the short period of 4 weeks owing to a dilution effect. Muscle edema seems to be an essential factor in cuff tears and subsequent muscle retraction and degeneration. CLINICAL RELEVANCE: This study demonstrates a new type of muscle edema of retraction and describes the characteristics of edema associated with a retracted rotator cuff tear.

Comparative performance of two automated machine learning platforms for COVID-19 detection by MALDI-TOF-MS.

The 2019 novel coronavirus infectious disease (COVID-19) pandemic has resulted in an unsustainable need for diagnostic tests. Currently, molecular tests are the accepted standard for the detection of SARS-CoV-2. Mass spectrometry (MS) enhanced by machine learning (ML) has recently been postulated to serve as a rapid, high-throughput, and low-cost alternative to molecular methods. Automated ML is a novel approach that could move mass spectrometry techniques beyond the confines of traditional laboratory settings. However, it remains unknown how different automated ML platforms perform for COVID-19 MS analysis. To this end, the goal of our study is to compare algorithms produced by two commercial automated ML platforms (Platforms A and B). Our study consisted of MS data derived from 361 subjects with molecular confirmation of COVID-19 status including SARS-CoV-2 variants. The top optimized ML model with respect to positive percent agreement (PPA) within Platforms A and B exhibited an accuracy of 94.9%, PPA of 100%, negative percent agreement (NPA) of 93%, and an accuracy of 91.8%, PPA of 100%, and NPA of 89%, respectively. These results illustrate the MS method's robustness against SARS-CoV-2 variants and highlight similarities and differences in automated ML platforms in producing optimal predictive algorithms for a given dataset.