Mark Pitkin

Atlanta Prosthetics & Orthotics, Inc., Atlanta, Georgia, United States

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Publications (18)27.8 Total impact

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    ABSTRACT: 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 skindevice 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 reseeding 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.
    Prosthetics and Orthotics International 08/2014; · 0.62 Impact Factor
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    ABSTRACT: 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. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
    Journal of Biomedical Materials Research Part A 09/2013; · 2.83 Impact Factor
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    ABSTRACT: This article presents results on the effectiveness of a new version of the titanium porous composite skin and bone integrated pylon (SBIP). The SBIP is designed for direct skeletal attachment of limb prostheses and was evaluated in a preclinical study with three rabbits. In accordance with the study protocol, a new version of the pylon (SBIP-3) was implanted into the hind leg residuum of three rabbits. The SBIP-3 has side fins that are designed to improve the bond between the bone and pylon. The fins are positioned inside two slots precut in the bone walls; their length can be adjusted to match the thickness of the bone walls. After 13 (animal 1) or 26 (animals 2 and 3) wk, the animals were sacrificed and samples collected for histopathological analysis. The space between the fins and the bone into which they were fit was filled with fibrovascular tissue and woven bone. No substantial inflammation was found. We suggest that if further studies substantiate the present results, the proposed method can become an alternative to the established technique of implanting prostheses into the medullary canal of the hosting bone.
    The Journal of Rehabilitation Research and Development 08/2013; 50(5):709-22. · 1.78 Impact Factor
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    ABSTRACT: 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 microns and Large, 100-160 microns), 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 7 groups. Implant extrusion rate was measured weekly and skin ingrowth into implants was determined histologically after harvesting implants. It was found that all 3 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 three weeks. We concluded that percutaneous porous titanium implants allow for skin integration with the potential for a safe seal.
    Journal of Biomedical Materials Research Part A 05/2013; · 2.83 Impact Factor
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    ABSTRACT: In direct skeletal attachment (DSA) of limb prostheses, a construct is implanted into an amputee's residuum bone and protrudes out of the residuum's skin. This technology represents an alternative to traditional suspension of prostheses via various socket systems, with clear indications when the sockets cannot be properly fitted. Contemporary DSA was invented in the 1990s, and several implant systems have been introduced since then. The current review is intended to compare the design features of implants for DSA whose use in humans or in animal studies has been reported in the literature. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
    Journal of Biomedical Materials Research Part A 04/2013; · 2.83 Impact Factor
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    ABSTRACT: 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 was 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 of 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, 4 months 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 prosthesis. Future studies with this model will help optimize the implant and prosthesis properties.
    Clinical biomechanics (Bristol, Avon) 01/2013; · 1.76 Impact Factor
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    ABSTRACT: Direct recordings were made of electrical signals emanating from the muscles in a rabbit's residuum. The signals were transmitted via wires attached on one end to the muscles, and on the other to an external recording system. The cable was held in a titanium tube inside a pylon that had been transcutaneously implanted into the residuum's bone. The tube was surrounded by porous titanium cladding to enhance its bond with the bone and with the skin of the residuum. This study was the first known attempt to merge the technology of direct skeletal attachment of limb prostheses with the technology of neuromuscular control of prostheses, providing a safe and reliable passage of the electrical signal from the muscles inside the residuum to the outside recording system.
    IEEE transactions on bio-medical engineering 02/2012; 59(5):1349-53. · 2.15 Impact Factor
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    M Pitkin, J Pilling, G Raykhtsaum
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    ABSTRACT: Composite pylons containing a solid titanium core with drilled holes surrounded by a porous sintered titanium shell have been fabricated and tested in bending along with the raw cores and pylons composed of the porous titanium alone. The new pylons were designed with the concept of enhanced in-growth of bone and skin cells and are intended for direct skeletal attachment of limb prostheses considering requirements for long-lasting anchorage to the residuum bone and a need for a safe skin-implant seal. Load-displacement thresholds were determined after which the integrity of the porous component may be compromised. The composite pylons have a flexural strength and stiffness substantially greater than that of pylons composed of the porous titanium alone. The drilled holes in the solid insert have been shown to have virtually no effect on the flexural strength of the pylon, while meeting a requirement for total permeability of the device for unrestricted cell ingrowth. The predicted strength of the pylons and associated failure modes are in close agreement with those measured.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 01/2012; 100(4):993-9. · 2.31 Impact Factor
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    ABSTRACT: The paper presents data on the cultivation of human dermal fibroblasts and rabbit mesenchymal stromal cells on two types of porous titanium implants, i.e., those with irregular pores formed by pressed titanium particles and those with regular pores formed by the cohesion of one-size titanium particles inside the implant. The goal of this study was to determine what type of titanium implant porosity ensured its strongest interaction with cells. Cells were cultivated on implants for 7 days. During this period, they formed a confluent monolayer on the implant surface. Cells grown on titanium implants were monitored by scanning electron microscopy. Fibroblasts interaction with implants depended on the implant porosity structure. On implants with irregular pores cells were more spread. On implants with regular pores fibroblasts enveloped particles and were only occasionally bound with neighboring particles by small outgrowths. There was no tight interaction of particles inside the implant. In implants formed by pressed particles, cells grow not only on surface, but also in the depth of the implant. Thus, we suppose that a tighter interaction of cells with the titanium implant and, supposedly, tissues with the implant in the organism will take place in the variant when the implant structure is formed by pressed titanium particles, i.e., cellular interaction was observed inside the implant. In implants with irregular pores, cells grew both on the surface and in the depth. Thus, cells exhibited more adequate interactions with irregular pore titanium implants in vitro and hopefully the same interaction will be true in tissues after the implantation of the prosthesis into the organism.
    Cell and Tissue Biology 01/2010; 4(6):572-579.
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    ABSTRACT: The data on human dermal fibroblasts and rabbit mesenchymal stromal cells cultivation on porous titanium implants are presented in given paper. Two types of implants were used: type 1--with irregular pores formed by pressed titanium particles and type 2--with regular pores formed by coalescence of one-size titanium particles into implant. The goal of this study was to choose the type of titanium implant porosity which ensures the tightest interaction of titanium implant with surrounding tissue cells after implantation in the body. Cells were cultivated on implants for 7 days and in both cases they formed confluent monolayer on the implants surfaces. That indicated adhesion, migration and proliferation of cells on such implants. Condition of cells cultured on titanium implants was controlled by scanning electron microscopy. The character of fibroblasts interaction with given implants was different depending on porosity type of implants. On implants with irregular pores, the cells were more spread and overlapped the pores spreading over neighbored particles. On implants with regular pores that formed by one-size particles into implant, the fibroblasts covered these particles not overlapping the pores and seldom interacted with neighbored particles by small outgrowths. There was no tight interaction of particles into implant. In implants formed by pressed particles, the cells grew not only on the surface but also in the depth of implant. Thereby, we suppose that more tight interaction of cells with titanium implant and, supposedly, tissues with implant in an organism will take place in the case of implant structure formed by pressed titanium particles.
    Tsitologiia 01/2010; 52(10):835-43.
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    M. R. Pitkin
    07/2009; 20(3):159-171.
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    Mark Pitkin
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    ABSTRACT: Two decades after introducing threaded titanium dental implants, Dr. Per-Ingvar Brånemark used a similar technique in the 1980s to pioneer the direct skeletal attachment (DSA) of limb prostheses. He and his colleagues used convincing clinical experience to overcome the skepticism of their peers, affording a new dimension of prosthetic rehabilitation to almost 100 individuals with amputation. As a result, more research has been initiated worldwide to move DSA to a level of greater safety, longevity, and reliability. This review highlights the trends and milestones in current DSA development. It also identifies ideas from previous studies in various fields that may be useful in future DSA development.
    The Journal of Rehabilitation Research and Development 02/2009; 46(3):345-60. · 1.78 Impact Factor
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    ABSTRACT: This article presents recent results in the development of the skin and bone integrated pylon (SBIP) intended for direct skeletal attachment of limb prostheses. In our previous studies of the porous SBIP-1 and SBIP-2 prototypes, the bond site between the porous pylons and residuum bone and skin did not show the inflammation characteristically observed when solid pylons are used. At the same time, porosity diminished the strength of the pylon. To find a reasonable balance between the biological conductivity and the strength of the porous pylon, we developed a mathematical model of the composite permeable structure. A novel manufacturing process was implemented, and the new SBIP-3 prototype was tested mechanically. The minimal strength requirements established earlier for the SBIP were exceeded threefold. The first histopathological analysis of skin, bone, and the implanted SBIP-2 pylons was conducted on two rats and one cat. The histopathological analysis provided new evidence of inflammation-free, deep ingrowth of skin and bone cells throughout the SBIP structure.
    The Journal of Rehabilitation Research and Development 02/2009; 46(3):315-30. · 1.78 Impact Factor
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    Mark Pitkin
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    ABSTRACT: Direct transcutaneous prosthetic attachment (osseointegration) consists of implanting directly into the residuum bone a metal pylon whose external fraction connects the residuum to the external prosthesis. Since the introduction of osseointegration about 20 years ago, the obvious challenge associated with this technology has been the skin-pylon interface as a source of infections. In comparison, the bone-device interface was considered less problematic because of the knowledge and experience inherited from dental implantology and total joint replacement (arthroplasty). Current methods of pylon fixation in osseointegration follow arthroplasty's paradigm of positioning the pylon's shaft inside the bone's medullary canal. However, adopting the medullary canal as a holding compartment for the pylon's shaft creates the problem of shaft loosening, which has not yet been solved in arthroplasty.
    The Journal of Rehabilitation Research and Development 02/2008; 45(4):vii-xiv. · 1.78 Impact Factor
  • Article: Response.
    Mark Pitkin
    The Journal of Rehabilitation Research and Development 01/2008; 45(9):xii-xiii. · 1.78 Impact Factor
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    Mark Pitkin
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    ABSTRACT: Providing the technical means to prevent collapse or falls in patients with different types of pathology in mo-tion and balance control is one of the traditional problems in rehabilitation engineering. A means of addressing the prob-lem using assistive devices, including prostheses, is to restrict the mobility in certain anatomical or artificial joints by ap-plying corsets, braces, brakes and locks. The restriction of mobility in the joints increases local stiffnesses, and in a sense, tunes the spectrum of oscillations in these joints out of resonantly dangerous zones. So far, these efforts for limiting un-wanted mobility are mostly empirical within rehabilitation technologies, and we suggest that they can be optimized with algorithms for controlling the spectrum of oscillations used in multi-linked technical systems. Further, we suggest that tuning out of resonance is inseparable from the phenomenon of tuning into resonance that is widely recognized in biome-chanics of locomotion. These considerations result in our postulating the principle of spectral reciprocity in locomotion.
    The Open Rehabilitation Journal. 01/2008; 1(1).
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    ABSTRACT: This article presents results of the further development and testing of the "skin and bone integrated pylon" (SBIP-1) for percutaneous (through skin) connection of the residual bone with an external limb prosthesis. We investigated a composite structure (called the SBIP-2) made of titanium particles and fine wires using mathematical modeling and mechanical testing. Results showed that the strength of the pylon was comparable with that of anatomical bone. In vitro and in vivo animal studies on 30 rats showed that the reinforcement of the composite pylon did not compromise its previously shown capacity for inviting skin and bone cell ingrowth through the device. These findings provide evidence for the safe and reliable long-term percutaneous transfer of vital and therapeutic substances, signals, and necessary forces and moments from a prosthetic device to the body.
    The Journal of Rehabilitation Research and Development 02/2007; 44(5):723-38. · 1.78 Impact Factor
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    ABSTRACT: Direct skeletal attachment of limb prostheses is a viable alternative to traditional techniques that are based on a socket-residuum interface. Direct skeletal attachment may be a better or even the only method for patients with a very short residuum and high soft-tissue volume. The problem of integrating the prosthetic pylon with residual skin during direct skeletal attachment of a limb prosthesis has not been solved, and the use of a completely porous prosthetic pylon has not been the subject of focused, systematic research. In this in vivo study, we investigated cell (osteocyte, fibroblast, and keratinocyte) adhesion and penetration into the pores of a titanium pylon implanted in Wistar rats. The porous titanium pylon was implanted in the bone of the thigh residua of four rats. Electronic scanning and morphological analysis demonstrated integration of the pylon with the surrounding skin. These findings support the possibility of developing a natural barrier against the infection associated with direct skeletal attachment of limb prostheses.
    The Journal of Rehabilitation Research and Development 01/2006; 43(4):573-80. · 1.78 Impact Factor

Publication Stats

79 Citations
27.80 Total Impact Points

Institutions

  • 2014
    • Atlanta Prosthetics & Orthotics, Inc.
      Atlanta, Georgia, United States
  • 2013
    • University of Massachusetts Boston
      Boston, Massachusetts, United States
    • Georgia Institute of Technology
      • School of Applied Physiology
      Atlanta, GA, United States
  • 2006–2013
    • Tufts University
      • Department of Physical Medicine and Rehabilitation
      Georgia, United States
  • 2008
    • Tufts Medical Center
      Boston, Massachusetts, United States