The <i>in vivo</i> effect of a porous titanium alloy flange with hydroxyapatite, silver and fibronectin coatings on soft-tissue integration of intraosseous transcutaneous amputation prostheses

AIMS: The Intraosseous Transcutaneous Amputation Prosthesis (ITAP) may improve quality of life for amputees by avoiding soft-tissue complications associated with socket prostheses and by improving sensory feedback and function. It relies on the formation of a seal between the soft tissues and the implant and currently has a flange with drilled holes to promote dermal attachment. Despite this, infection remains a significant risk. This study explored alternative strategies to enhance soft-tissue integration. MATERIALS AND METHODS: The effect of ITAP pins with a fully porous titanium alloy flange with interconnected pores on soft-tissue integration was investigated. The flanges were coated with fibronectin-functionalised hydroxyapatite and silver coatings, which have been shown to have an antibacterial effect, while also promoting viable fibroblast growth in vitro. The ITAP pins were implanted along the length of ovine tibias, and histological assessment was undertaken four weeks post-operatively. RESULTS: The porous titanium alloy flange reduced epithelial downgrowth and increased soft-tissue integration compared with the current drilled flange. The addition of coatings did not enhance these effects. CONCLUSION: These results indicate that a fully porous titanium alloy flange has the potential to increase the soft-tissue seal around ITAP and reduce susceptibility to infection compared with the current design

Enhancing the Soft Tissue-Implant Seal and Reducing Bacterial Colonisation around the Intraosseous Transcutaneous Amputation Prosthesis

The Intraosseous Transcutaneous Amputation Prosthesis (ITAP) may improve quality of life for amputees by avoiding soft tissue complications associated with socket prostheses and by improving sensory feedback and function. ITAP relies on a soft tissue seal forming at the skin-implant interface in order to prevent epithelial downgrowth and infection. A successful soft tissue seal is dependent on soft tissue cells winning the ‘race for the surface’ against bacteria. The current ITAP design includes a flange with drilled holes to promote soft tissue attachment. Despite this, infection remains a significant risk. This thesis aimed to investigate the effect of a fully porous titanium alloy (PT) flange with interconnected pores and fibronectin (Fn)-functionalised hydroxyapatite (HA) coatings on soft tissue integration. Silver (Ag) was incorporated into coatings for its antimicrobial properties. In vitro fibroblast viability and bacterial colonisation on HAAgFn coatings was studied. HAAgFn was applied to PT flanges of transcutaneous pins implanted into sheep tibiae. A histological assessment of soft tissue integration was undertaken and bacterial colonisation within the soft tissues and on the flange was quantified. The key original contributions to knowledge from this thesis are that firstly, HAAgFn coatings have antibacterial activity and are cytocompatible after serum- preconditioning in vitro. Secondly, in vivo, PT significantly reduces epithelial downgrowth, increases soft tissue integration and reduces bacterial colonisation compared with the current ITAP drilled-hole flange. Overall, the addition of coatings did not enhance these effects in vivo. HA reduced the favourable effects of PT. Fn and Ag counteracted some of the negative effects of HA suggesting that using these coatings without HA could improve results. In conclusion, a PT flange has the potential to reduce the susceptibility of ITAP to infection compared with the current ITAP design. It is hoped that this finding will be translated into clinical practice

An overview of the key principles and guidelines in the management of pelvic fractures.

Pelvic fractures are complex injuries with a range of different presentations depending on the mechanism of trauma. Due to the morbidity and mortality of pelvic fractures, patients require thorough investigation and timely management with multidisciplinary input. Various surgical and non-surgical techniques can be used to treat pelvic fractures, as well as any associated visceral injuries. Following repair, it is important to remain vigilant for postoperative complications such as infection, sexual and urinary dysfunction, chronic pain and adverse psychological health. This article summarises the relevant UK guidance and literature and presents them in a format that follows the patient's journey. In doing so, it highlights the key perioperative factors that need to be considered in cases of pelvic fracture

Determining the porous structure for optimal soft-tissue ingrowth: An in vivo histological study

The success of osseointegrated transcutaneous prostheses depends on a soft-tissue seal forming at the skin-implant interface in order to prevent infection. Current designs include a flange with drilled holes or a subdermal barrier with a porous coating in an attempt to promote soft-tissue attachment. However, the soft-tissue seal is not reliably achieved despite these designs and infection remains a significant problem. This study investigated soft-tissue integration into fully porous titanium alloy structures with interconnected pores. The study aimed to determine the effect of altering pore and strut size combinations on soft-tissue ingrowth into porous titanium alloy structures in vivo. It was hypothesized that implants with a more open porous structure with larger pore sizes would increase soft-tissue ingrowth more than less open porous structures. Porous titanium alloy cylinders were inserted into sheep paparaspinal muscles (n = 6) and left in situ for four weeks. A histological assessment of soft-tissue ingrowth was performed. Percentage soft-tissue pore fill, cell nuclei density and blood vessel density were quantified. The results showed that larger pore sizes were supportive of soft-tissue ingrowth. A structure with a pore size of 700μm and a strut size of 300μm supported revascularisation to the greatest degree. A flange with this structure may be used in future studies of osseointegrated transcutaneous prostheses in order to enhance the soft-tissue seal

Augmenting the osseointegration of endoprostheses using laser-sintered porous collars: an in vivo study

AIMS: Massive endoprostheses rely on extra-cortical bone bridging (ECBB) to enhance fixation. The aim of this study was to investigate the role of selective laser sintered (SLS) porous collars in augmenting the osseointegration of these prostheses. MATERIALS AND METHODS: The two novel designs of porous SLS collars, one with small pores (Ø700 μm, SP) and one with large pores (Ø1500 μm, LP), were compared in an ovine tibial diaphyseal model. Osseointegration of these collars was compared with that of a clinically used solid, grooved design (G). At six months post-operatively, the ovine tibias were retrieved and underwent radiological and histological analysis. RESULTS: Porous collars provided a significantly greater surface (p < 0.001) for the ingrowth of bone than the standard grooved design. Significantly greater extracortical pedicle formation was seen radiologically around the grooved design (length p = 0.002, thickness p < 0.001, surface area p = 0.002) than around the porous collars. However, the ingrowth of bone occurred from the transection site into the porous structure of both types of collar. A fivefold increase in integration was seen with the SP and a threefold increase in the LP design when compared with G (p < 0.001). CONCLUSION: SLS porous collars allow the direct ingrowth of more bone and are better than current designs which rely on surface ongrowth and ECBB. Cite this article: Bone Joint J 2017;99-B:276-82

Preventing infection of osseointegrated transcutaneous implants: Incorporation of silver into preconditioned fibronectin-functionalized hydroxyapatite coatings suppresses Staphylococcus aureus colonization while promoting viable fibroblast growth in vitro

The success of transcutaneous implants depends on the achievement of a soft tissue seal by enabling fibroblasts to win the race for the surface against bacteria. Fibronectin-functionalized hydroxyapatite coatings (HAFn) have been shown to improve dermal tissue ingrowth and attachment. However, during the early postoperative period before a soft tissue seal has formed, bacterial colonization may occur. This study explored the incorporation of silver, a broad spectrum antimicrobial agent, into HAFn coatings with the aim of reducing bacterial colonization. Silver is known to have dose-dependent cytotoxic effects. Therefore, the effects of silver incorporation into HAFn coatings on both in vitro human dermal fibroblast viability and Staphylococcus aureus colonization were assessed. An electrochemical deposition technique was used to codeposit hydroxyapatite and silver (HAAg) and fibronectin was adsorbed onto this to produce HAAgFn coatings. Surfaces were preconditioned with serum to mimic the in vivo environment. Nonpreconditioned HAAg and HAAgFn coatings suppressed bacterial colonization but were cytotoxic. After serum-preconditioning, more than 90% of fibroblasts that grew on all HAAg and HAAgFn coatings were viable. The highest silver content coatings tested (HAAg100 and HAAgFn100) resulted in a greater than 99% reduction in biofilm and planktonic bacterial numbers compared to HA and HAFn controls. Although HAAg100 had greater antibacterial activity than HAAgFn100, the findings of this study indicate that fibroblasts would win the race for the surface against S aureus on both HAAg100 and HAAgFn100 after serum-preconditioning

Hard-wired epimysial recordings from normal and reinnervated muscle using a bone-anchored device

Background: A combined approach for prosthetic attachment and control using a transcutaneous bone-anchored device and implanted muscle electrodes can improve function for upper-limb amputees. The bone-anchor provides a transcutaneous feed-through for muscle signal recording. This approach can be combined with targeted muscle reinnervation (TMR) to further improve myoelectric control. Methods: A bone-anchored device was implanted trans-tibially in n = 8 sheep with a bipolar recording electrode secured epimysially to the peroneus tertius muscle. TMR was carried out in a single animal: the peroneus tertius was deinnervated and the distal portion of the transected nerve to the peroneus muscle was coapted to a transected nerve branch previously supplying the tibialis anterior muscle. For 12 weeks (TMR) or 19 weeks (standard procedure), epimysial muscle signals were recorded while animals walked at 2 km·h−1. Results: After 19 weeks implantation following standard procedure, epimysial recording signal-to-noise ratio (SNR) was 18.7 dB (± 6.4 dB, 95% CI) with typical recordings falling in the range 10–25 dB. Recoveries in gait and muscle signals were coincident 6 weeks post-TMR; initial muscle activity was identifiable 3 weeks post-TMR though with low signal amplitude and signal-to-noise ratio compared with normal muscle recordings. Conclusions: Following recovery, muscle signals were recorded reliably over 19 weeks following implantation. In this study, targeted reinnervation was successful in parallel with bone-anchor implantation, with recovery identified 6 weeks after surger