Modeling of the Effect of Subperiosteal Hydrostatic Pressure Conductivity between Joints on Decreasing Contact Loads on Cartilage and of the Effect of Myofascial Relief in Treating Trigger Points: The Floating Skeleton Theory.

Chronic overloading of the cartilage can lead to its irreversible destruction, as observed in people with osteoarthritis. The floating skeleton model previously introduced postulates that overloading begins and progresses when a joint is isolated from the hydrostatical connection with other joints. Such a connection occurs via the interstitial fluid in subperiosteal space and allows for pressure transmission between synovial capsules modulating intra-articular pressure. In the current study, a simple experiment was performed to model an obstruction in the subperiosteal hydrostatic pressure conductivity between joints to illustrate the effect of that obstruction on loads borne by the joint. When the obstruction was removed, the load experienced by the joint was reduced as it was redistributed throughout the model structure. The experiment demonstrated that contact pressures can be redistributed when the conditions of Pascal's Law are met.

The Moment Criterion of Anthropomorphicity of Prosthetic Feet as a Potential Predictor of Their Functionality for Transtibial Amputees.

The purpose of this paper is to discuss a new quantitative mechanical parameter of prosthetic feet called the Index of Anthropomorphicity (IA), which has the potential to be adopted as an objective predictor of their functionality. The objectives are to present the research findings supporting the introduction of IA and unify previous results into a coherent theory. The IA is founded on the moment criterion of the anthropomorphicity of prosthetic feet. The term "anthropomorphicity" is defined for this application. Studies with a small number of human subjects and prostheses have shown that the value of the parameter is positively correlated with patient comfort and with the restoration of certain normal gait characteristics. Confirmatory studies with controlled human trials and mechanical tests with a wider selection of prosthesis types can give prosthesis manufacturers a new criterion to follow in the design process, and prosthetists may use the IA for selecting more suitable prostheses for a patient's comfort and health.

Electrical Stimulation of Distal Tibial Nerve During Stance Phase of Walking May Reverse Effects of Unilateral Paw Pad Anesthesia in the Cat.

Cutaneous feedback from feet is involved in regulation of muscle activity during locomotion, and the lack of this feedback results in motor deficits. We tested the hypothesis that locomotor changes caused by local unilateral anesthesia of paw pads in the cat could be reduced/reversed by electrical stimulation of cutaneous and proprioceptive afferents in the distal tibial nerve during stance. Several split-belt conditions were investigated in four adult female cats. In addition, we investigated the effects of similar distal tibial nerve stimulation on overground walking of one male cat that had a transtibial, bone-anchored prosthesis for 29 months and, thus, had no cutaneous/proprioceptive feedback from the foot. In all treadmill conditions, cats walked with intact cutaneous feedback (control), with right fore- and hindpaw pads anesthetized by lidocaine injections, and with a combination of anesthesia and electrical stimulation of the ipsilateral distal tibial nerve during the stance phase at 1.2× threshold of afferent activation. Electrical stimulation of the distal tibial nerve during the stance phase of walking with anesthetized ipsilateral paw pads reversed or significantly reduced the effects of paw pad anesthesia on several kinematic variables, including lateral center of mass shift, cycle and swing durations, and duty factor. We also found that stimulation of the residual distal tibial nerve in the prosthetic hindlimb often had different effects on kinematics compared with stimulation of the intact hindlimb with paw anesthetized. We suggest that stimulation of cutaneous and proprioceptive afferents in the distal tibial nerve provides functionally meaningful motion-dependent sensory feedback, and stimulation responses depend on limb conditions.

Temporary Botulinum Immobilization of Residuum Muscles for Facilitation of the Initial Ingrowth of Skin to the Porous Skin and Bone Integrated Pylon in the Technology of Direct Skeletal Attachment: Large Animal Model.

Enhancing the technology of bone-anchored limb prosthetics, we present a modified porcine model for developing an infection-free integration between the skin and a percutaneous bone implant. The deeply porous Skin and Bone Integrated Pylon (SBIP) presented an infection-free skin-implant interface both after implantation into the dorsum and after implantation into the residuum after below-knee amputation. However, deep ingrowth of skin into the porous cladding of the SBIP was achieved better in the dorsal procedure, while implantation to the residuum sometimes developed a stoma, probably due to the high mobility of the skin and soft tissues in the pig's thigh. Uncontrolled high skin mobility during the first week after implantation constituted a limitation for the porcine animal model, which we tried to address in the current study. As our previous studies showed that casting of the leg residuum did not sufficiently limit the skin's movement around the implant, we tested a modified protocol of the implantation, which included injection of botulinum toxin into the thigh muscles. During the course of the study, we identified proper botulinum toxin componentry, dosage, and the period after injections to achieve a maximal effect of immobilization of the muscles affecting skin movements. To verify the immobilization, we used kinetic data on the asymmetry of loading during gait with the Strideway System, Tekscan, Inc., Boston, MA, USA. We found that injections in the four muscles of the distal thigh of the left hind leg with MYOBLOC® (rimabotulinumtoxinB; 5,000 units/muscle) were sufficient to provide noticeable immobilization by the fourth week after the procedure. This conclusion was made based on the analysis of the dynamics of asymmetry in vertical ground reactions on the injected (left hind) and uninvolved (right hind) legs during gait over an instrumented walkway.

Recent Progress in Animal Studies of the Skin- and Bone-integrated Pylon With Deep Porosity for Bone-Anchored Limb Prosthetics With and Without Neural Interface.

INTRODUCTION: The three major unresolved problems in bone-anchored limb prosthetics are stable, infection-free integration of skin with a percutaneous bone implant, robust skeletal fixation between the implant and host bone, and a secure interface of sensory nerves and muscles with a prosthesis for the intuitive bidirectional prosthetic control. Here we review results of our completed work and report on recent progress. MATERIALS AND METHODS: Eight female adult cats received skin- and bone-integrated pylon (SBIP) and eight male adult cats received SBIP-peripheral neural interface (PNI) pylon into the right distal tibia. The latter pylons provided PNI for connection between a powered sensing transtibial prosthesis and electrodes in residual soleus muscle and on residual distal tibial nerve. If signs of infection were absent 28-70 days after implantation, cats started wearing a passive prosthesis. We recorded and analyzed full-body mechanics of level and slope locomotion in five cats with passive prostheses and in one cat with a powered sensing prosthesis. We also performed histological analyses of tissue integration with the implants in nine cats.Four pigs received SBIPs into the left hindlimb and two pigs-into the left forelimb. We recorded vertical ground reaction forces before amputation and following osseointegration. We also conducted pullout postmortem tests on the implanted pylons. One pig received in dorsum the modified SBIPs with and without silver coating. RESULTS: Six cats from the SBIP groups had implant for 70 days. One cat developed infection and did not receive prosthesis. Five cats had pylon for 148 to 183 days, showed substantial loading of the prosthesis during locomotion (40.4% below presurgery control), and demonstrated deep ingrowth of skin and bone tissue into SBIP (over 60%). Seven of eight cats from the SBIP-PNI group demonstrated poor pylon integration without clinical signs of infection. One cat had prosthesis for 824 days (27 months). The use of the bidirectionally controlled prosthesis by this animal during level walking demonstrated increased vertical loading to nearly normal values, although the propulsion force was significantly reduced.From the study on pigs, it was found that symmetry in loading between the intact and prosthetic limbs during locomotion was 80 ± 5.5%. Skin-implant interface was infection-free, but developed a stoma, probably because of the high mobility of the skin and soft tissues in the pig's thigh. Dorsal implantation resulted in the infection-free deep ingrowth of skin into the SBIP implants. CONCLUSIONS: Cats with SBIP (n = 5) and SBIP-PNI (n = 1) pylons developed a sound interface with the residuum skin and bone and demonstrated substantial loading of prosthetic limb during locomotion. One animal with SBIP developed infection and seven cats with SBIP-PNI demonstrated poor bone integration without signs of infection. Future studies of the SBIP-PNI should focus on reliability of integration with the residuum. Ongoing study with pigs requires decreasing the extra mobility of skin and soft tissues until the skin seal is developed within the SBIP implant.

Loading Effect of Prosthetic Feet's Anthropomorphicity on Transtibial Osseointegrated Implant.

INTRODUCTION: Osseointegrated implants for direct skeletal attachment of transtibial prosthesis carry risks that are yet to be fully resolved, such as early loosening, mechanical failure of percutaneous and medullar parts of implant, periprosthetic issues, and infections. Underloading could lead to early loosening and infection. Overloading might compromise the bone-implant interface. Therefore, Goldilocks loading regimen applied by transtibial bone-anchored prostheses is critical for safe and efficient development of osseointegration around the implant during rehabilitation and beyond. We hypothesized that Goldilocks loading could be achieved when ambulating with a so-called anthropomorphic prosthetic ankle showing moment-angle relationship similar to a sound ankle. MATERIALS AND METHODS: Quantitative characteristics of the moment-angle curve of the sound ankle during dorsiflexion phase of a free-pace walking were extracted for 4 able-bodied participants (experiment 1). A slope of the moment-angle curve (stiffness) was calculated twice: for the first half and for the second half of the moment-angle curve. The difference of stiffnesses (those at the second half minus at the first half) was called the index of anthropomorphicity (IA). By definition, positive IA is associated with concave shape of the moment-angle curve, and the negative IA is associated with convex shape. In experiment 2, the same recordings and calculations were performed for 3 participants fitted with transtibial osseointegrated fixation during walking with their usual feet and the Free-Flow Foot (Ohio Willow Wood). The Free-Flow Foot was selected for its anthropomorphicity demonstrated in the previous studies with amputees using traditional socket attachment. RESULTS: The IA was 5.88 ± 0.93 for the able-bodied participants, indicating that the stiffness during the first part of the dorsiflexion phase was substantially fewer than during the second parts, as the calf muscles resisted to angulation in ankle substantially less than during the second part of dorsiflexion phase. For amputees fitted with Free-Flow Foot, IA was 2.68 ± 1.09 and -2.97 ± 2.37 for the same amputees fitted with their usual feet. CONCLUSIONS: Indexes of anthropomorphicity, while of different magnitude, were positive in control able-bodied group and in the amputee group wearing Free-Flow Foot, which was qualitatively associated with concave shape of their moment-angle curves. The 3 usual feet worn by the participants were classified as nonanthropomorphic as their individual moment-angle curves were convex and the corresponding IAs were negative. Furthermore, this study showed that a foot with anthropomorphic characteristics tends to decrease maximal loads at the bone-implant interface as compared to the nonanthropomorphic feet and possibly may minimize the risks to compromise the integrity of this interface.

New Training System Based on the Discovery of Subperiosteal Transmission of Pressures Between Joint Capsules.

BACKGROUND: A new training and rehabilitation methodology called Sanomechanics® is presented based on a recent discovery of the anatomical system called Floating Skeleton System (FSS) responsible for redistributing contact pressures in the joint capsules and thus minimizing the loads on joint cartilages. MATERIALS AND METHODS: The main idea behind the Sanomechanics® methodology (SMM) is that when this system of subperiosteal pressure transmission is disrupted, the overloading of cartilages may occur leading to trauma, osteoarthritis and other related pathologies. Conversely, if functioning of the FSS is adequately restored and continuously maintained, the pathological developments can be effectively stopped. RESULTS: Analysis of existing training systems using mind-body approach revealed that they are lacking the understanding of a physiological mechanism of their success or failure in training. It is postulated that maintaining/restoration of transmission of pressure between the joint capsules is necessary component of preventing overloading of joint cartilages occurring in military training and operations and in civilian life. Visualization of this concept has been suggested as a key element to the SMM training system. CONCLUSIONS: The FSS provides for a guidance for development of scientific approaches to the training and rehabilitation techniques. The SMM is balanced mind-body training system, which can help U.S. Servicemen and Servicewomen be better prepared for extreme load during their service.

Protecting the skin-implant interface with transcutaneous silver-coated skin-and-bone-integrated pylon in pig and rabbit dorsum models.

Implant-associated soft tissue infections at the skin-implant interface represent the most frequent complications in reconstructive surgery and lead to implant failures and revisions. Titanium implants with deep porosity, called skin-and-bone-integrated-pylons (SBIP), allow for skin ingrowth in the morphologically natural direction, thus restoring a reliable dermal barrier and reducing the risk of infection. Silver coating of the SBIP implant surface using physical vapor deposition technique offers the possibility of preventing biofilm formation and exerting a direct antimicrobial effect during the wound healing phase. In vivo studies employing pig and rabbit dorsum models for assessment of skin ingrowth into the pores of the pylon demonstrated the safety of transcutaneous implantation of the SBIP system. No postoperative complications were reported at the end of the follow-up period of 6 months. Histological analysis proved skin ingrowth in the minipig model without signs of silver toxicity. Analysis of silver release (using energy dispersive X-ray spectroscopy) in the model of intramedullary-inserted silver-coated SBIP in New Zealand rabbits demonstrated trace amounts of silver after 3 months of in-bone implantation. In conclusion, selected temporary silver coating of the SBIP implant surface is powerful at preventing the periprosthetic infections without imparing skin ingrowth and can be considered for clinical application.

Inter-participant variability data in loading applied on osseointegrated implant by transtibial bone-anchored prostheses during daily activities.

The data in this paper are related to the research article entitled "Loading applied on osseointegrated implant by transtibial bone-anchored prostheses during daily activities: Preliminary characterization of prosthetic feet" (Frossard et al., 2019: Accepted). This article contains the individual and grouped loading characteristics applied on transtibial osseointegrated implant generated while walking with bone-anchored prostheses including prosthetic feet with different index of anthropomorphicity. Inter-participant variability was presented for (A) the spatio-temporal characteristics, (B) the loading boundaries and (C) the loading local extremum during walking, ascending and descending ramp and stairs. These initial inter-participant variability benchmark datasets are critical to improve the efficacy and safety of prosthetic components for transtibial prostheses as well as the design of future automated algorithms and clinical trials. Online repository contains the files: https://doi.org/10.17632/vhc6sf7ngy.1.

Inter-participant variability data in characterization of anthropomorphicity of prosthetic feet fitted to bone-anchored transtibial prosthesis.

The data in this paper are related to the research article entitled "Automated characterization of anthropomorphicity of prosthetic feet fitted to bone-anchored transtibial prosthesis" (Frossard et al., 2019: DOI: 10.1109/TBME.2019.2904713). This article contains the individual angles of dorsiflexion and bending moments generated while walking with transtibial bone-anchored prostheses including prosthetic feet with different index of anthropomorphicity. Inter-participant variability were presented for the (A) position of the load cell measuring directly to the bending moments, (B) patterns of angles of dorsiflexion and bending moment as well as moment-angle curves and (C) variations of magnitude of angles of dorsiflexion as well as the raw and bodyweight-normalized bending moments between toe contact and heel off. These initial inter-participant variability benchmark datasets are critical to design future automated algorithms and clinical trials. Online repository contains the files: https://eprints.qut.edu.au/127745/1/127745.pdf.

Automated characterization of anthropomorphicity of prosthetic feet fitted to bone-anchored transtibial prosthesis.

OBJECTIVE: This study describes differentiating prosthetic feet designs fitted to bone-anchored transtibial prostheses based on an automated characterization of ankle stiffness profile relying on direct loading measurements. The objectives were (A) to present a process characterizing stiffness using innovative macro, meso and micro analyses, (B) to present stiffness profiles for feet with and without anthropomorphic designs, where anthropomorphicity is defined as a similarity of the moment-angle dependency in prosthetic and in the anatomical ankle, (C) to determine sensitivity of characterization. METHODS: Three participants walked consecutively with two instrumented bone-anchored prostheses including their own prosthetic feet and Free-Flow foot meeting the anthropomorphicity criterion by design. Angle of dorsiflexion was extracted from video footage. Bending moment was recorded using multi-axis transducer attached to osseointegrated fixation. The automated characterization of stiffness involved a 12-step process relying on data-based criterion. RESULTS: The meso analyses confirmed bilinear behavior of moment-angle curves with Index of Anthropomorphicity of -2.966±2.369 Nm/Deg and 2.681±1.089 Nm/Deg indicating a convex and concave shape of usual and Free-Flow feet without and with anthropomorphic designs, respectively. CONCLUSIONS: The proposed straightforward meso analysis of the stiffness was capable to report clinical meaningful differences sensitive to feet's anthropomorphicity. Results confirmed the benefits for clinicians to rely on direct loading measurement providing individualized complementary insight into impact of components. SIGNIFICANCE: This work could assist the developments of standards and guidelines for manufacturing and safe fitting of components to growing population requiring transtibial prostheses with socket or direct skeletal attachment worldwide.

Evaluation of the temporary effect of physical vapor deposition silver coating on resistance to infection in transdermal skin and bone integrated pylon with deep porosity.

Periprosthetic infection via skin-implant interface is a leading cause of failures and revisions in direct skeletal attachment of limb prostheses. Implants with deep porosity fabricated with skin and bone integrated pylons (SBIP) technology allow for skin ingrowth through the implant's structure creating natural barrier against infection. However, until the skin cells remodel in all pores of the implant, additional care is required to prevent from entering bacteria to the still nonoccupied pores. Temporary silver coating was evaluated in this work as a means to provide protection from infection immediately after implantation followed by dissolution of silver layer in few weeks. A sputtering coating with 1 µm thickness was selected to be sufficient for fighting infection until the deep ingrowth of skin in the porous structure of the pylon is completed. In vitro study showed less bacterial (Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa) growth on silver coated tablets compared to the control group. Analysis of cellular density of MG-63 cells, fibroblasts, and mesenchymal stem cells (MSCs) showed that silver coating did not inhibit the cell growth on the implants and did not affect cellular functional activity. The in vivo study did not show any postoperative complications during the 6-month observation period in the model of above-knee amputation in rabbits when SBIP implants, either silver-coated or untreated were inserted into the bone residuum. Three-phase scintigraphy demonstrated angiogenesis in the pores of the pylons. The findings suggest that a silver coating with well-chosen specifications can increase the safety of porous implants for direct skeletal attachment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 169-177, 2019.

Distraction Implantation. A New Technique in Total Joint Arthroplasty and Direct Skeletal Attachment.

BACKGROUND: Using the marrow canal of a tubular bone as a holding compartment for implant stems has been the paradigm in total joint arthroplasty for more than a century, and for direct skeletal attachment of limb prostheses for about forty years. Both interventions rely on the osteogenesis in the inner walls of the marrow canal in a direction radially inwards. It so remains despite the frequent aseptic loosening of the implant stems caused by the resorption of the marrow canal's inner walls which increases the canal's diameter and reduces its capacity to hold the implant. MATERIALS AND METHODS: To improve the bone-device bond, we suggest an implantation methodology that activates positive osteogenic remodeling in the circular direction rather than radially inwards. The rationale is that circular osteogenesis is a component of natural healing of bone fractures and its activating may mitigate the consequences of resorption caused by stress shielding, bone developmental growth and other factors. RESULTS: Circular osteogenesis occurs in response to the distraction of slots precut into the bone tube. We call this methodology distraction implantation (DI) because of its debt to Ilizarov type distraction osteogenesis (DO). The methodology is accompanied by a design of an implant stem, and has been investigated in a previous pilot animal study. CONCLUSION: Distraction implantation is based on a component of natural healing of bone fractures and therefore has merit to be investigated further.

Kinetics of individual limbs during level and slope walking with a unilateral transtibial bone-anchored prosthesis in the cat.

Ongoing animal preclinical studies on transcutaneous bone-anchored prostheses have aimed to improve biomechanics of prosthetic locomotion in people with limb loss. It is much less common to translate successful developments in human biomechanics and prosthetic research to veterinary medicine to treat animals with limb loss. Current standard of care in veterinary medicine is amputation of the whole limb if a distal segment cannot be salvaged. Bone-anchored transcutaneous prostheses, developed for people with limb loss, could be beneficial for veterinary practice. The aim of this study was to examined if and how cats utilize the limb with a bone-anchored passive transtibial prosthesis during level and slope walking. Four cats were implanted with a porous titanium implant into the right distal tibia. Ground reaction forces and full-body kinematics were recorded during level and slope (±50%) walking before and 4-6 months after implantation and prosthesis attachment. The duty factor of the prosthetic limb exceeded zero in all cats and slope conditions (p < 0.05) and was in the range of 45.0-60.6%. Thus, cats utilized the prosthetic leg for locomotion instead of walking on three legs. Ground reaction forces, power and work of the prosthetic limb were reduced compared to intact locomotion, whereas those of the contralateral hind- and forelimbs increased (p < 0.05). This asymmetry was likely caused by insufficient energy generation for propulsion by the prosthetic leg, as no signs of pain or discomfort were observed in the animals. We concluded that cats could utilize a unilateral bone-anchored transtibial prosthesis for quadrupedal level and slope locomotion.

Subperiosteal transmission of intra-articular pressure between articulated and stationary joints.

Hydrostatic pressures can be transmitted between synovial capsules. In each of ten rabbits, we simultaneously measured pressure in two joints, one of which was passively ranged, and the other of which was kept stationary. The intra-articular pressure inside the stationary joint changed every time its companion joint was ranged. But the pressure in the stationary joint did not change when the periosteum was transected above the ranged joint. This phenomenon was observed in all four animals that served as their own controls. The study suggests that the intra-articular pressure was transmitted through the space between the periosteum and the bone surface. Alternative explanations, like measurements of venous blood pressure, did not show correlation with hydrostatic pressure changes in the joints. The Floating Skeleton concept suggests a biomechanical rationale for this newly observed phenomenon: that there exists a subperiosteal hydrostatic connection of synovial joints, and that this "net" distributes excess pressures among joints through the periosteal sheath to sustain the integrity of the joint contacting surfaces over a lifetime.

Application of the skin and bone integrated pylon with titanium oxide nanotubes and seeded with dermal fibroblasts.

BACKGROUND: Direct skeletal attachment of limb prostheses is associated with high rate of transcutaneous infection and loosening of the fixture in the medullary canal prompting for careful assessment of various means for enhancing the skin-device and bone-device interface. The skin and bone integrated pylon system constitutes a technological platform for different modifications being evaluated previously. OBJECTIVES: The current study assessed the combination of nano-treatment skin and bone integrated pylon with its pre-seeding with dermal fibroblasts. We hypothesized that this combination will enhance cell interaction with skin and bone integrated pylon compared to nano-treatment and the fibroblast seeding when done separately. STUDY DESIGN: The feasibility and safety of in-bone implantation of the skin and bone integrated pylon with nanotubes was investigated in vitro and in vivo in the animal model. METHODS: TiO2 nanotubes were fabricated on the skin and bone integrated pylon, and the fibroblasts taken from rabbit's skin were cultured on the pylons before implantation. RESULTS: The in vitro experiments demonstrated higher cellular density in the samples with a nanotubular surface than in the non-modified pylons used as control. There were no postoperative complications in any of the animals during the 6-month observation period. Subsequent scanning electron microscopy of the pylon extracted from the rabbit's femur showed the stable contact between the pylon and soft tissues in comparison to control samples where the patchy fibrovascular ingrowth was detected. CONCLUSION: The promising results prompt further investigation of the integrative properties of the nanotextured skin and bone integrated pylon system seeded with dermal fibroblasts and its optimization for clinical application. CLINICAL RELEVANCE: The study is devoted to the development of more safe and efficient technology of direct skeletal attachment of limb prostheses aimed in improving quality of life of people with amputations.

An animal model to evaluate skin-implant-bone integration and gait with a prosthesis directly attached to the residual limb.

BACKGROUND: Despite the number of advantages of bone-anchored prostheses, their use in patients is limited due to the lack of complete skin-implant integration. The objective of the present study was to develop an animal model that would permit both detailed investigations of gait with a bone-anchored limb prosthesis and histological analysis of the skin-implant-bone interface after physiological loading of the implant during standing and walking. METHODS: Full-body mechanics of walking in two cats were recorded and analyzed before and after implantation of a percutaneous porous titanium pylon into the right tibia and attachment of a prosthesis. The rehabilitation procedures included initial limb casting, progressively increasing loading on the implant, and standing and locomotor training. Detailed histological analysis of bone and skin ingrowth into implant was performed at the end of the study. FINDINGS: The two animals adopted the bone-anchored prosthesis for standing and locomotion, although loads on the prosthetic limb during walking decreased by 22% and 62%, respectively, 4months after implantation. The animals shifted body weight to the contralateral side and increased propulsion forces by the contralateral hindlimb. Histological analysis of the limb implants demonstrated bone and skin ingrowth. INTERPRETATION: The developed animal model to study prosthetic gait and tissue integration with the implant demonstrated that porous titanium implants may permit bone and skin integration and prosthetic gait with a bone-anchored prosthesis. Future studies with this model will help optimize the implant and prosthesis properties.

Effects of pore size, implantation time, and nano-surface properties on rat skin ingrowth into percutaneous porous titanium implants.

The main problem of percutaneous osseointegrated implants is poor skin-implant integration, which may cause infection. This study investigated the effects of pore size (Small, 40-100 µm and Large, 100-160 µm), nanotubular surface treatment (Nano), and duration of implantation (3 and 6 weeks) on skin ingrowth into porous titanium. Each implant type was percutaneously inserted in the back of 35 rats randomly assigned to seven groups. Implant extrusion rate was measured weekly and skin ingrowth into implants was determined histologically after harvesting implants. It was found that all three types of implants demonstrated skin tissue ingrowth of over 30% (at week 3) and 50% (at weeks 4-6) of total implant porous area under the skin; longer implantation resulted in greater skin ingrowth (p < 0.05). Only one case of infection was observed (infection rate 2.9%). Small and Nano groups showed the same implant extrusion rate which was lower than the Large group rate (0.06 ± 0.01 vs. 0.16 ± 0.02 cm/week; p < 0.05). Ingrowth area was comparable in the Small, Large, and Nano implants. However, qualitatively, the Nano implants showed greatest cellular inhabitation within first 3 weeks. We concluded that percutaneous porous titanium implants allow for skin integration with the potential for a safe seal.

Two-stage implantation of the skin- and bone-integrated pylon seeded with autologous fibroblasts induced into osteoblast differentiation for direct skeletal attachment of limb prostheses.

Angio- and osteogenesis following the two-stage (TS) implantation of the skin- and bone-integrated pylon seeded with autologous fibroblasts was evaluated. Two consecutive animal substudies were undertaken: intramedullary subcutaneous implantation (15 rabbits) and a TS transcutaneous implantation (12 rabbits). We observed enhanced osseointegrative properties of the intramedullary porous component seeded with fibroblasts induced into osteoblast differentiation, as compared to the untreated porous titanium pylon. The three-phase scintigraphy and subsequent histological analysis showed that the level of osteogenesis was 1.5-fold higher than in the control group, and significantly so (p < 0.05). The biocompatibility was further proved by the absence of inflammatory response or encapsulation and sequestration on the histology assay. Treatment of the transcutaneous component with autologous fibroblasts was associated with nearly a 2-fold decrease in the period required for the ingrowth of dermal and subdermal soft tissues into the implant surface, as compared to the untreated porous titanium component. Direct dermal attachment to the transcutaneous implant prevented superficial and deep periprosthetic infections in rabbits in vivo.