The clinical, radiological, microbiological, and molecular profile of the skin-penetration site of transfemoral amputees treated with bone-anchored prostheses

Infection After Lower-Limb Osseointegration: A Single-Center Retrospective Evaluation of Pathogens, Management, and Outcomes

PURPOSE

Osseointegration (OI) is a novel alternative to traditional socket-suspended prostheses for lower-limb amputees, eliminating the socket-skin interface and allowing for weight bearing directly on the skeletal system. However, the stoma through which the implant attaches to the external prosthesis creates an ingress route for bacteria, and infection rates as high as 66% have been reported. The aims of this study are to classify infection management and long-term outcomes in this patient population to maximize implant salvage.

METHODS

An institutional review board-approved retrospective analysis was performed on all patients who underwent lower-limb OI at our institution between 2017 and 2022. Demographic, operative, and outcome data were collected for all patients. Patients were stratified by the presence and severity of infection. Chi-square and t tests were performed on categorical and continuous data, respectively, using an alpha of 0.05.

RESULTS

One hundred two patients met our study criteria; 62 had transfemoral OI and 40 had transtibial OI. Patients were followed for 23.8 months on average (range, 3.5-63.7). Osteomyelitis was more likely than soft tissue infection to be polymicrobial in nature (71% vs 23%, P < 0.05). Infections at the stoma were mostly (96%) managed with oral antibiotics alone, whereas deeper soft tissue infections also required intravenous antibiotics (75%) or operative washout (19%). Osteomyelitis was managed with intravenous antibiotics and required operative attention; 5 (71%) underwent washout and 2 (29%) underwent explantation. Both implants were replaced an average of 3.5 months after explantation. There was no correlation between history of soft tissue infection and development of osteomyelitis (P > 0.05). The overall implant salvage rate after infection was 96%.

CONCLUSIONS

This study describes our institution's experience managing infection after OI and soft tissue reconstruction. Although infections do occur, they are easily treatable and rarely require operative intervention. Explantation due to infection is rare and can be followed up with reimplantation, reaffirming that OI is a safe and effective treatment modality.

Association between blood markers and the progression of osseointegration in percutaneous prostheses patients-A pilot study

Patients implanted with osseointegrated (OI) prosthetic systems have reported vastly improved upper and lower extremity prosthetic function compared with their previous experience with socket-suspension systems. However, OI systems have been associated with superficial and deep-bone infections and implant loosening due, in part, to a failure of the osseointegration process. Although monitoring the osseointegration using circulating biomarkers has clinical relevance for understanding the progression of osseointegration with these devices, it has yet to be established. Ten patients were enrolled in this study. Blood samples were collected at pre-selected times, starting before implantation surgery, and continuing to 12 months after the second surgery. Bone formation markers, bone resorption markers, and circulating amino acids were measured from blood samples. A linear mixed model was generated for each marker, incorporating patient ID and age with the normalized marker value as the response variable. Post hoc comparisons were made between 1 week before Stage 1 Surgery and all subsequent time points for each marker, followed by multiple testing corrections. Serial radiographic imaging of the residual limb containing the implant was obtained during follow-up, and the cortical index (CI) was calculated for the bone at the porous region of the device. Two markers of bone formation, specifically bone-specific alkaline phosphatase (Bone-ALP) and amino-terminal propeptide of type I procollagen (PINP), exhibited significant increases when compared with the baseline levels of unloaded residual bone prior to the initial surgery, and they subsequently returned to their baseline levels by the 12-month mark. Patients who experienced clinically robust osseointegration experienced increased cortical bone thickness at the porous coated region of the device. A medium correlation was observed between Bone-ALP and the porous CI values up to PoS2-M1 (p = .056), while no correlation was observed for PINP. An increase in bone formation markers and the lack of change observed in bone resorption markers likely reflect increased cortical bone formation induced by the end-loading design of the Utah OI device used in this study. A more extensive study is required to validate the correlation observed between Bone-ALP and porous CI values.

Impact of topography and added TiN-coating on adult human dermal fibroblasts after seeding on titanium surface in-vitro

Complications of transcutaneous osseointegrated prosthetic systems (TOPS) focus on the metal-cutaneous interface at the stoma. Besides pain due to scare tissue as well as undefined neuropathic disorders, there is high evidence that the stoma presents the main risk causing hypergranulation and ascending infection. To restore the cutaneous barrier function in this functional area, soft-tissue on- or in-growth providing a vital and mechanically stable bio-artificial conjunction is considered a promising approach. In this study we assessed viability and proliferation of adult human dermal fibroblasts (HDFa) on modifications of a standard prosthetic titanium surface. Un-coated (TiAl6V4) as well as a titanium-nitrite (TiN) coated additive manufactured porous three-dimensional surface structures (EPORE®) were seeded with HDFa and compared to plain TiAl6V4 and polystyrene surfaces as control. Cell viability and proliferation were assessed at 24 h and 7 days after seeding with a fluorescence-based live-dead assay. Adhesion and cell morphology were analyzed by scanning electron microscopy at the respective measurements. Both EPORE® surface specifications revealed a homogenous cell distribution with flat and spread cell morphology forming filopodia at both measurements. Proliferation and trend to confluence was seen on un-coated EPORE® surfaces with ongoing incubation but appeared substantially lower on the TiN-coated EPORE® specification. While cell viability on both EPORE® specifications was comparable to plain TiAL6V4 and polystyrene controls, cell proliferation and confluence were less pronounced when compared to controls. The EPORE® topography allows for fibroblast adhesion and viability in both standard TiAl6V4 and - to a minor degree - TiN-coated specifications as a proof of principle.

Construction of a Localized and Long-Acting CCN2 Delivery System on Percutaneous Ti Implant Surfaces for Enhanced Soft-Tissue Integration

Soft-tissue integration (STI) plays an essential role in the long-term success of percutaneous Ti implants since it acts as a biological barrier that protects the soft and hard tissue around implants. Surface modification of Ti implants with drug-release properties to achieve soft-tissue regeneration has been proven to be effective in STI. However, the short-acting effect caused by the uncontrolled drug release of the topical delivery system limits long-term STI enhancement. Herein, a long-acting protein delivery system for Ti implants that involved micro-arc oxidation of Ti surfaces (MAO-Ti) and localized immobilization of cellular communication network factor 2 (CCN2) bearing mesoporous silica nanoparticles (MSNs) on MAO-Ti was prepared, namely, CCN2@MSNs-Ti. The CCN2 release study of CCN2@MSNs-Ti demonstrated a sustained-release profile for 21 days, which was able to maintain long-term stable STI. In addition, in vitro cell behavior evaluation results indicated that CCN2@MSNs-Ti could promote the STI-related biological response of human dermal fibroblasts via the FAK-MAPK pathway. More importantly, the system could effectively enhance STI after 4 weeks and proinflammatory factors in the soft tissue decreased significantly in a rat model of implantation. These results denote that CCN2@MSNs-Ti showed an appealing application prospect for enhanced STI around transcutaneous Ti implants, which would ultimately result in an increased success rate of percutaneous Ti implants.

Osseointegrated prostheses for the rehabilitation of patients with transfemoral amputations: A prospective ten-year cohort study of patient-reported outcomes and complications

Background

Methods

Results

Conclusion

Microbiological Profile of the Implantation Zone under Different Mechanical Compression of Percutaneous Implants: Experimental Study

Background. Infection of percutaneous implants in patients with limb amputation is the most common complication. Aim of the study evaluation of the microflora in the implantation zone depending on the mechanical compression of the implant in conditions of its additional external fixation. Methods. The study was performed on 36 male rabbits. The tibia of all the rabbits was sawn at the border of the upper and middle parts. The medullary canal was reamed and a percutaneous implant was placed in the tibial stump. The segment and the implant were fixed with an Ilizarov apparatus. An additional compression device was installed in 30 animals. We used 5 compression modes, accordingly, 6 experimental groups were formed, 6 animals in each: group 1 without compression, group 2 compression on the implant with force of 0.053 N/mm2, group 3 compression on the implant with force of 0.105 N/mm2, group 4 compression on the implant with force of 0.158 N/mm2, group 5 compression on the implant with force of 0.211 N/mm2, group 6 compression on the implant with force of 0.263 N/mm2. The restraint was removed 6 weeks after implantation for a total follow-up of 26 weeks. The microflora of the place where the implant enters the skin (the implant / skin interface) was investigated, the level of blood leukocytes and the level of C-reactive protein in blood serum were determined. Results. On days 9-10 after implantation, significant differences in the microbial landscape were found at the site of the exit of the metal implant in animals of different groups. The largest number of strains was found in animals of groups 1, 5 and 6, the smallest in groups 2 and 3. The most frequently detected strains: S. saprophyticus and Enterococcus spp. It was found that the greatest statistically significant increase in the level of CRP in the blood serum was observed in animals of group 6. The level of leukocytes in animals of all groups did not change statistically significantly relative to preoperative values. Animals with better osseointegration (groups 2 and 3 no cases of implant loss) showed a minimal number of growing strains. Conclusions. The microbiological profile of the implantation zone of percutaneous implants changes depending on the amount of mechanical compression. The optimal mode is 0.053-0.105 N/mm2.

Osseointegration Amputation Reconstruction

Purpose of Review

To review the topic of osseointegration amputation reconstruction, which inserts a transcutaneous metal implant into the remaining intramedullary bone of a person with an amputation to facilitate a direct bone-anchored connection to an external prosthesis, eliminating the molded socket interface.

Recent Findings

Evidence continues to build that patients function better and have a higher quality of life with osseointegration implants compared with traditional socket prosthetics. The indications for osseointegration are expanding to additional patient populations and the long-term outcomes available are favorable which supports the continued refinement and utilization of the technology.

Summary

Osseointegration implants offer people with amputations freedom from burdensome socket prosthetics while improving function and quality of life. Mild infections at the skin interface are common but managed effectively with oral antibiotics and rarely lead to deep infection and implant removal. Other serious complications like hip or implant fracture are also uncommon. Additional long-term outcomes are needed along with technologic refinements, especially at the skin implant interface.

Extramedullary Osseointegration-A Novel Design of Percutaneous Osseointegration Prosthesis for Amputees

The percutaneous osseointegrated (OI) prostheses have greatly improved the overall quality of life for amputees. However, the long-term maintenance of the OI prostheses is still challenging. A major problem is bone resorption around the bone-implant-skin interface, which might cause implant loosening or osteomyelitis. Another problem is the breakage of connecting components between the intramedullary implant and external prosthesis due to excessive stress. We designed a novel osseointegration implant by changing the bone-implant contact from the inner cortex to the outer surface of cortical bone. In the current study, we compared the extramedullary cap-shaped implants with the intramedullary screw-type implants in rabbits. Osteointegration was confirmed at the interface of bone to implant contact (BIC) in both implant types. The external implant induced intramedullary bone regeneration in the medullary canal and increased the cortical bone density at the end of the stump. This study provides a new perspective on the design of osseointegration implants which might prevent the currently reported complications of the intramedullary OI systems.

Achieving stomal continence with an ileal pouch and a percutaneous implant

In this study, a soft-tissue-anchored, percutaneous port used as a mechanical continence-preserving valve in reservoir ileo- and urostomies was functionally and morphologically evaluated in eight dogs. During follow-up, the skin failed to attach to the implant, but the intestine inside the stoma port appeared to be attached to the mesh. After reaching adequate reservoir volume, the urostomies were rendered continent by attaching a lid to the implant. The experiments were ended at different time intervals due to implant-related adverse events. In only one case did the histological evaluation reveal integration at both the implant-intestine and implant-skin interfaces, with a low degree of inflammation and the absence of bacterial colonisation. In the remaining cases, integration was not obtained and instead mucosal downgrowth and biofilm formation were observed. The skin-implant junction was characterised by the absence of direct contact between the epidermis and the implant. Varying degrees of epidermal downgrowth, granulation tissue formation, inflammatory cell infiltration and bacterial growth and biofilm formation were prominent findings. In contrast, the subcutaneously located anchor part of the titanium port was well integrated and encapsulated by fibrous tissue. These results demonstrate the opportunity to achieve integration between a soft-tissue-anchored titanium port, skin and intestine. However, predictable long-term function could not be achieved in these animal models due to implant- and non-implant-related adverse events. Unless barriers at both the implant-skin and implant-intestine junctions are created, epidermal and mucosal downward migration and biofilm formation will jeopardise implant performance.

Immunomodulatory effects exerted by extracellular vesicles from Staphylococcus epidermidis and Staphylococcus aureus isolated from bone-anchored prostheses

Staphylococcus aureus and Staphylococcus epidermidis are the bacteria that most frequently cause osteomyelitis. This study aimed to determine whether staphylococci isolated from osteomyelitis associated with septic loosening of orthopedic prostheses release extracellular vesicles (EVs) and, if so, to determine tentative immunomodulatory effects on the human monocytic cell line THP-1. EVs were isolated from bacterial cultures using filtration and ultracentrifugation and characterized by scanning electron microscopy, nanoparticle tracking analysis and Western Blot. The cytotoxic effect of EVs was analyzed by NucleoCounter and lactate dehydrogenase (LDH) analyses. Confocal laser scanning microscopy was employed to visualize the uptake of EVs by THP-1 cells. Activation of the transcription factor nuclear factor-κB (NF-κB) was determined in THP1-Blue™ NF-κB cells, and the gene expression and secretion of cytokines were determined by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. All investigated strains, irrespective of their biofilm formation ability, were able to secrete EVs in vitro. The S. aureus strains produced significantly more EVs than the S. epidermidis strains. Both S. aureus-derived EVs and S. epidermidis-derived EVs were internalized by THP-1 cells, upregulated Toll-like receptor 3 (TLR3) gene expression, activated NF-κB, and promoted the gene expression and secretion of interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1, matrix metallopeptidase (MMP)-9 and IL-10. Whereas EVs from both staphylococcal species upregulated the proapoptotic DNA damage-inducible transcript 4 (DDIT4) gene and downregulated the antiapoptotic B-cell lymphoma 2 (Bcl-2) gene, cytolysis was preferentially induced in S. aureus EV-stimulated cells, possibly related to the expression of cytolytic proteins predominantly in S. aureus EVs. In conclusion, staphylococcal EVs possess potent cytolytic and immunomodulatory properties.

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.

Multimodal Analysis of the Tissue Response to a Bone-Anchored Hearing Implant: Presentation of a Two-Year Case Report of a Patient With Recurrent Pain, Inflammation, and Infection, Including a Systematic Literature Review

Osseointegration is a well-established concept used in applications including the percutaneous Bone-Anchored Hearing System (BAHS) and auricular rehabilitation. To date, few retrieved implants have been described. A systematic review including cases where percutaneous bone-anchored implants inserted in the temporal bone were retrieved and analyzed was performed. We also present the case of a patient who received a BAHS for mixed hearing loss. After the initial surgery, several episodes of soft tissue inflammation accompanied by pain were observed, leading to elective abutment removal 14 months post-surgery. Two years post-implantation, the implant was removed due to pain and subjected to a multiscale and multimodal analysis: microbial DNA using molecular fingerprinting, gene expression using quantitative real-time polymerase chain reaction (qPCR), X-ray microcomputed tomography (micro-CT), histology, histomorphometry, backscattered scanning electron microscopy (BSE-SEM), Raman spectroscopy, and fluorescence in situ hybridization (FISH). Evidence of osseointegration was provided via micro-CT, histology, BSE-SEM, and Raman spectroscopy. Polymicrobial colonization in the periabutment area and on the implant, including that with Staphylococcus aureus and Staphylococcus epidermidis, was determined using a molecular analysis via a 16S-23S rDNA interspace [IS]-region-based profiling method (IS-Pro). The histology suggested bacterial colonization in the skin and in the peri-implant bone. FISH confirmed the localization of S. aureus and coagulase-negative staphylococci in the skin. Ten articles (54 implants, 47 patients) met the inclusion criteria for the literature search. The analyzed samples were either BAHS (35 implants) or bone-anchored aural epitheses (19 implants) in situ between 2 weeks and 8 years. The main reasons for elective removal were nonuse/changes in treatment, pain, or skin reactions. Most samples were evaluated using histology, demonstrating osseointegration, but with the absence of bone under the implants’ proximal flange. Taken together, the literature and this case report show clear evidence of osseointegration, despite prominent complications. Nevertheless, despite implant osseointegration, chronic pain related to the BAHS may be associated with a chronic bacterial infection and raised inflammatory response in the absence of macroscopic signs of infection. It is suggested that a multimodal analysis of peri-implant health provides possibilities for device improvements and to guide diagnostic and therapeutic strategies to alleviate the impact of complications.

[Transcutaneous osseointegrated prosthetic systems after major amputation of the lower extremity : A retrospective 3-year analysis]

INTRODUCTION

Transcutaneous osseointegrated prosthetic systems (TOPS) are an established optional procedure for the prosthetic treatment of amputations. Under the term endo-exo-prosthesis (EEP), the endosteal adapted exo-prosthesis (Dr. Grundei®) is currently used as the only standard prosthesis for clinical application in Germany. The prosthetic treatment with EEP involves a two-stage surgical procedure. In a first surgical step, the endo-fixed stem is implanted into the bone; in a second operation, approx. 2-6 weeks later, the skin/soft tissue stoma is created, through which the exoprosthetic components can be coupled transcutaneously.

AIM

The aim of this manuscript was to retrospectively collect descriptive 3‑year statistics (2017-2019) from clinical follow-ups and to analyze them with regard to possible effects of TOPS on the mobility level measured by k‑levels. In addition, a brief description of the current standard of care in Germany regarding TOPS will be given.

METHODS

All patients who underwent EEP after major amputation from February 2017 to December 2019 (n = 72, with 76 implants) were included in this study. The data of the EEP patients were collected in standardized follow-ups. K‑levels were compared preoperatively to 6 months postoperatively.

RESULTS

A total of N = 72 patients (N = 76 implantations) was analyzed in the described period. The main cause of amputations was trauma (68.9%). Main complications were myofascial complaints. Implant loosening and deep infections were observed in two cases (2.7%) during this period. Stoma problems occurred with a 3-year average of 25.7%. In terms of K‑levels, there was a high significant increase from preoperative 1.8 ± 0.8 to 3.0 ± 0.4 after a 6-month period.

CONCLUSION

TOPS is an established optional procedure for the treatment of limb loss. In Germany, only one implant is currently regularly implanted (endo-exo prosthesis), and the restoration is currently focused on the lower limb. The restoration of patients with major amputation of the lower extremity by means of TOPS can lead to an increase in mobility and, thus, to an increase in daily activities and participation in daily living.

Advanced techniques in amputation surgery and prosthetic technology in the lower extremity

Bone-anchored implants give patients with unmanageable stump problems hope for drastic improvements in function and quality of life and are therefore increasingly considered a viable solution for lower-limb amputees and their orthopaedic surgeons, despite high infection rates.Regarding diversity and increasing numbers of implants worldwide, efforts are to be supported to arrange an international bone-anchored implant register to transparently overview pros and cons.Due to few, but high-quality, articles about the beneficial effects of targeted muscle innervation (TMR) and regenerative peripheral nerve interface (RPNI), these surgical techniques ought to be directly transferred into clinical protocols, observations and routines.Bionics of the lower extremity is an emerging cutting-edge technology. The main goal lies in the reduction of recognition and classification errors in changes of ambulant modes. Agonist-antagonist myoneuronal interfaces may be a most promising start in controlling of actively powered ankle joints.As advanced amputation surgical techniques are becoming part of clinical routine, the development of financing strategies besides medical strategies ought to be boosted, leading to cutting-edge technology at an affordable price.Microprocessor-controlled components are broadly available, and amputees do see benefits. Devices from different manufacturers differ in gait kinematics with huge inter-individual varieties between amputees that cannot be explained by age. Active microprocessor-controlled knees/ankles (A-MPK/As) might succeed in uneven ground-walking. Patients ought to be supported to receive appropriate prosthetic components to reach their everyday goals in a desirable way.Increased funding of research in the field of prosthetic technology could enhance more high-quality research in order to generate a high level of evidence and to identify individuals who can profit most from microprocessor-controlled prosthetic components. Cite this article: EFORT Open Rev 2020;5:724-741. DOI: 10.1302/2058-5241.5.190070.

Extracellular Vesicles Influence the Growth and Adhesion of Staphylococcus epidermidis Under Antimicrobial Selective Pressure

Staphylococcus epidermidis causes infections associated with orthopedic implants due to its ability to establish persistent biofilms, making infections chronic and hard to treat. Extracellular vesicles (EVs) are part of the bacterial communication system, but the role of S. epidermidis-derived EVs in biofilm formation processes and survival is completely unknown. The aims of this study were (i) to investigate the effect of subinhibitory concentrations of antibiotics on vesiculation in S. epidermidis and evaluate the role of EVs in bacterial survival and adhesion under antimicrobial selective pressure and (ii) to evaluate whether EVs derived from a gentamicin-resistant S. epidermidis strain influence the susceptibility and adhesion of a gentamicin-susceptible strain. A gentamicin-susceptible (GEN^S) strain isolated from implant-associated osteomyelitis was cultured with EVs previously isolated from the same strain growing with subinhibitory concentrations of GEN (0, 0.03, and 0.06 μg × mL^–1) or with EVs from a gentamicin-resistant (GEN^R) strain. EVs were characterized regarding their size, number and protein content. The growth of S. epidermidis cultured with increasing concentrations of GEN (<=> MIC of 0.12 μg × mL^–1) was recorded, viability was determined by quantitative culturing and fluorescence staining, and biofilm biomass on polystyrene was quantified by crystal violet staining. Cells grown in subinhibitory concentrations of GEN produced a larger number of EVs of similar size but with greater protein content than cells grown in control (Ctrl) conditions (0 GEN). Under antimicrobial pressure, EVs promoted different mechanisms of antimicrobial tolerance depending on the EV and GEN concentrations. Cell adhesion to polystyrene decreased in the presence of 0 and 0.03 μg × mL^–1 GEN upon EV stimulation. Compared with Ctrl cells, cells treated with EVs from a GEN^R strain showed increased cell division during the exponential growth phase, faster maximal growth rate, shorter doubling time (8–33 min), and dramatically inhibited cell adhesion. These findings suggest that vesiculation in S. epidermidis is a survival response to subinhibitory concentrations of gentamicin. EVs may contribute to bacterial survival through their involvement (1) in the modulation of the growth rate, affecting cell division, and (2) in cell adhesion, decreasing cell attachment to polystyrene and glass.

Three-year follow-up of changes of cortical bone thickness after implantation of Endo-Exo-Prosthesis (EEP) for transfemoral amputees

Introduction

Transcutaneous Osseointegrated Prosthetic Systems (TOPS) offer a good alternative for patients who cannot be satisfactorily rehabilitated by conventional suspension sockets. The Endo-Exo-Prothesis (EEP, ESKA Orthopaedic Handels GmbH®, Deutschland) is the most implanted TOPS in Germany. Previous studies have shown that cortical thickness increases after implantation of TOPS. The aim of this study is to determine changes of cortical thickness in relation to the time after implantation of the Endo-Fix-Stem.

Patients and methods

All transfemoral amputees treated by EEP from 2007 to 2013 were operated by the last author of this study. X-ray images of 4 follow-up intervals (postoperative, 3 months, 12 months, 3 years) were analyzed retrospectively. The femoral residuum was divided into 3 sections (proximal, middle, distal) with 2 measuring points in each section: medial and lateral. Cortical thickness was measured at these 6 points and compared at regular intervals using the Friedman test for non-parametric dependent variables.

Results

Thirty-seven patients with 40 implants were included. The average age was 52.2 years (30–79 years). 83.7% of the patients were male. No statistical significance could be shown for any of the measuring points of the femoral residual (proximal medial, proximal lateral, middle medial, middle lateral, distal medial, distal lateral) among the mean values of the cortical thickness at the different follow-up times (p > 0.05 for all measuring points). Cortical remodeling processes (> 1 millimeter (mm)) occurred in all implants despite a missing statistical significance. Hypertrophy could be confirmed for 42.5% and atrophy for 37.5%. Twenty percent of the cases showed a parallel occurrence of both entities. Cortical changes greater than 5 mm were only observed at the distal end of the femur.

Conclusion

Even if our results did not show any significant difference, it can be deduced that the osseointegration process leads to a remodeling of the bone structure, both in terms of increased bone formation and bone resorption. However, it has not yet been conclusively clarified which processes lead to hyper- or atrophy. The force transmission between prosthesis and bone and the facultative bacterial colonization of the stoma are still the main factors which may be responsible for the bone remodeling processes.

Clinical Outcomes of Soft Tissue Preservation Surgery With Hydroxyapatite-Coated Abutments Compared to Traditional Percutaneous Bone Conduction Hearing Implant Surgery-A Pragmatic Multi-Center Randomized Controlled Trial

Background: Soft tissue preservation using a hydroxyapatite-coated abutment in bone conduction hearing implant surgery may lead to improved clinical outcomes over the short (1 year) and long term (3 years).

Methods: In this open multi-center, randomized (1:1), controlled clinical trial, subjects with conductive, mixed hearing loss or single-sided sensorineural deafness were randomly assigned to receive the conventional intervention, a titanium abutment with soft tissue reduction surgery (control), or a new intervention, a hydroxyapatite-coated abutment with soft tissue preservation surgery (test). The primary efficacy outcome was the combined endpoint of numbness, pain, peri-abutment dermatitis, and soft tissue thickening/overgrowth after 1 and 3 years.

Results: The Intention-to-treat (ITT) population consisted of 52 control subjects and 51 test subjects. The difference between the groups after 1 year of follow-up as measured by the primary efficacy outcome was not statistically significant (p = 0.12) in the ITT population (n = 103), but did reach statistical significance (p = 0.03) in the per-protocol (PP) population (n = 96). It showed an advantage for the test group, with over twice as many subjects (29%) without these medical events during the first year compared to the control group (13%). After 3 years, the difference between the two groups had declined and did not reach statistical significance (24 vs. 10%, ITT p = 0.45). Secondary outcome measures which showed a statistical significant difference during the first year, such as surgical time (15 vs. 25 minutes, p < 0.0001), numbness (90 vs. 69% of subjects experienced no numbness at 1 year, p < 0.01), neuropathic pain at 3 months (p = 0.0087) and the overall opinion of the esthetic outcome (observer POSAS scale at 3 months, p < 0.01) were favorable for the test group. More soft tissue thickening/overgrowth was observed at 3 weeks for the test group (p = 0.016). Similar results were achieved for the long term follow up.

Conclusions: Soft tissue preservation with a hydroxyapatite-coated abutment leads to a reduction in the combined occurrence of complications over the first year which is not statistically significant in the ITT population but is in the PP population. This effect decreased for the long-term study follow up of 3 years and did also not reach statistical significance.

Efficacy of a topical formulation of henna (Lawsonia inermis L.) in contact dermatitis in patients using prosthesis: A double-blind randomized placebo-controlled clinical trial

BACKGROUND

Contact dermatitis is a common complication in prosthetic limb users. There are no effective, available and cheap treatments for skin problems of these patients. In traditional Iranian medicine, henna (Lawsonia inermis L.) is a plant that has anti-inflammatory, antimicrobial and skin-enhancing properties, all of which are beneficial for people with artificial limbs. The aim of this study was to assess the efficacy of a topical henna preparation in management of contact dermatitis in patients using lower limb prosthetics.

METHODS

The current randomized, double-blind, placebo-controlled clinical trial was conducted on ninety-five participants with lower extremity amputation using limb prosthetics, aged 12-70 years who complained of contact dermatitis. They were randomly assigned to receive either two weeks of topical henna preparation every night as the intervention group, or topical placebo as the control group. Participants were instructed to spread henna preparation on the surfaces of the amputated limb that were in contact with the prosthesis. Severity of contact dermatitis symptoms was set as the primary outcome measure. Edema, papules and erythema were evaluated by a physician using standard color atlas. Secondary outcomes included symptoms such as burning, itching, pain, thickness and skin sweating evaluated by a self-administered questionnaire.

RESULTS

A significant improvement was observed in the symptoms of contact dermatitis including skin edema, itching, sweating, skin thinning and pain (p-value<0.05) in the henna group compared to the placebo group. Skin burning decreased more in the henna group compared to the placebo group, but this was not statistically significant (p-value = 0.052). Moreover, skin redness significantly increased in the henna group (p-value = 0.001).

CONCLUSION

Topical formulation of henna might be a complementary choice for improving contact dermatitis in patients using lower limb prosthetics.

A 15-year follow-up of transfemoral amputees with bone-anchored transcutaneous prostheses

AIMS

The aim of this study was to describe implant and patient-reported outcome in patients with a unilateral transfemoral amputation (TFA) treated with a bone-anchored, transcutaneous prosthesis.

METHODS

In this cohort study, all patients with a unilateral TFA treated with the Osseointegrated Prostheses for the Rehabilitation of Amputees (OPRA) implant system in Sahlgrenska University Hospital, Gothenburg, Sweden, between January 1999 and December 2017 were included. The cohort comprised 111 patients (78 male (70%)), with a mean age 45 years (17 to 70). The main reason for amputation was trauma in 75 (68%) and tumours in 23 (21%). Patients answered the Questionnaire for Persons with Transfemoral Amputation (Q-TFA) before treatment and at two, five, seven, ten, and 15 years' follow-up. A prosthetic activity grade was assigned to each patient at each timepoint. All mechanical complications, defined as fracture, bending, or wear to any part of the implant system resulting in removal or change, were recorded.

RESULTS

The Q-TFA scores at two, five, seven, and ten years showed significantly more prosthetic use, better mobility, fewer problems, and an improved global situation, compared with baseline. The survival rate of the osseointegrated implant part (the fixture) was 89% and 72% after seven and 15 years, respectively. A total of 61 patients (55%) had mechanical complications (mean 3.3 (SD 5.76)), resulting in exchange of the percutaneous implant parts. There was a positive relationship between a higher activity grade and the number of mechanical complications.

CONCLUSION

Compared with before treatment, the patient-reported outcome was significantly better and remained so over time. Although osseointegration and the ability to transfer loads over a 15-year period have been demonstrated, a large number of mechanical failures in the external implant parts were found. Since these were related to higher activity, restrictions in activity and improvements to the mechanical properties of the implant system are required. Cite this article: Bone Joint J 2020;102-B(1):55-63.

Changes in periprosthetic bone mineral density and bone turnover markers after osseointegrated implant surgery: A cohort study of 20 transfemoral amputees with 30-month follow-up

BACKGROUND

The osseointegrated implant system is a treatment option for people with transfemoral amputation, but implant removal is not uncommon. The association between bone mineral density changes or bone turnover markers and the need for implant removal has not previously been investigated.

OBJECTIVES

The aim was to evaluate changes in bone mineral density and bone turnover markers in people with transfemoral amputations treated with osseointegrated implants.

STUDY DESIGN

This is a prospective cohort study.

METHODS

Nineteen patients were followed up for 30 months or until implant removal. Bone mineral density was measured in the lumbar spine, proximal femur and seven periprosthetic regions. 25-hydroxyvitamin (D2 + D3), parathyroid hormone, N-terminal propeptide of type-I procollagen, C-telopeptide of type-I collagen, bone-specific alkaline phosphatase and osteocalcin were measured in blood samples.

RESULTS

Four fixtures and three abutments were removed. Patients with removed implants had a decreased bone mineral density in the seven periprosthetic regions between 27% (95% confidence interval = 6; 43) and 38% (95% confidence interval = 19; 52) at 30-month follow-up compared to baseline (p < 0.02), whereas bone mineral density around non-removed implants normalized to baseline values (p > 0.08). C-telopeptide of type-I collagen was significantly different between the groups at 18- and 24-month follow-up (p < 0.05). None of the measured variables were significant predictors of implant removal (p > 0.07).

CONCLUSION

Implant removal was associated with loss of periprosthetic bone mineral density and increase in C-telopeptide of type-I collagen in the years following osseointegrated surgery.

CLINICAL RELEVANCE

This study offers new insight into changes in bone mineral density and bone turnover markers that precipitate aseptic or septic osseointegrated implant removal. Results of this study could contribute to clinical guidelines for monitoring rehabilitation progress and implant removal through dual-energy X-ray absorptiometry or surrogate markers like C-telopeptide of type-I collagen.

Does migration of osseointegrated implants for transfemoral amputees predict later revision? A prospective 2-year radiostereometric analysis with 5-years clinical follow-up

BACKGROUND

The osseointegrated (OI) prosthesis is a treatment option for transfemoral amputees with a short residual femur and/or difficulties caused by using the prosthetic socket. Implant removal due to aseptic or septic loosening is not uncommon, but the association between implant migration patterns and the need for removal has not previously been studied. We conducted a prospective model-based radiostereometric analysis study to investigate: if the OI implant migration pattern 1) differs between later removed implants and non-removed implants, (2) predicts later implant removal, and (3) if the precision of the method is acceptable.

HYPOTHESIS

Model-based radiostereometric analysis of the OI implant migration pattern can be used to predict later OI implant removal.

MATERIAL AND METHODS

A prospective cohort of 17 consecutive transfemoral amputees suitable for surgery (11 males), mean age 50 (range 32-66) were treated with an OI implant (Integrum AB, Sweden). Postoperative stereoradiographs of the OI implant were obtained during 24-month follow-up. X, Y, and Z translations and total translations were evaluated using CAD-implant models. Implant survival was followed for up to 60 months.

RESULTS

Six total implant removals (fixture and abutment) and four partial removals (abutment) were conducted (10/17 (59%)), and one patient did not use the OI implant. The removed implants group migrated a mean (±standard deviation) 0.55mm±0.75mm (p=0.009) and the non-removed implants group migrated 0.31mm±0.51mm (p=0.22) in total translations from 3 months to last follow-up. Odds ratio for implant removal was 22.5 (95% CI: 1.6 to 314 (p=0.021)) if the OI implants migrated distally.

CONCLUSION

Later removed OI implants migrated from 3 months to last follow-up and more than the non-removed OI implants. Distal implant migration greatly increased the odds of implant removal. Ten out of 17 OI implants were removed within 5 years of follow-up. We advise to use OI implants with caution and close follow-up in consideration of the risk of complications.

LEVEL OF EVIDENCE

IV, Prospective study.

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.

A Comparative Analysis of Standardised Threads for Use in Implants for Direct Skeletal Attachment of Limb Prosthesis: A Finite Element Analysis

The aim of the research was to determine the optimal thread's shape to be used in implants for direct skeletal attachment of limb prosthesis. In addition, by testing appropriate parameters' modification of the suitable thread, an attempt was made to maximise its effectiveness. The analyses included three thread types described in the ISO standards: shallow, symmetrical, and asymmetrical. The obtained results suggest that shallow thread ensures the lowest equivalent and directional stress peaks generated in the bone as well as favourable stress patterns and profiles during implant loading in relation to symmetrical and asymmetrical threads. Moreover, shallow thread ensured the generation of single equivalent and directional stress peaks, while symmetrical and asymmetrical threads provided additional stress peak for equivalent as well as for each of directional peaks. Subsequently, optimisation of the shallow thread's shape was conducted by changing two relevant thread's parameters (flank angle and rounding arc) which influence the generated stress distribution. The highest reduction of stress peaks was obtained while reducing the rounding arc by 0.2 mm. Therefore, it can be stated that the proposed modification of the HA thread can lead to obtaining a higher biomechanical effectiveness of implants for direct skeletal attachment of limb prosthesis.

Cytokine expression profile in the bone-anchored hearing system: 12-week results from a prospective randomized, controlled study

Objective

To study the effect of implanting the percutaneous bone‐anchored hearing system (BAHS) itself and inflammation of the peri‐abutment skin warrant clarification. In this study, we aimed to acquire further insight into the immune responses related to BAHS surgery and peri‐implant skin inflammation.

Materials and Methods

During surgery and 12 weeks post‐implantation, skin biopsies were obtained. If applicable, additional biopsies were taken during cases of inflammation. The mRNA expression of IL‐1β, IL‐6, IL‐8, TNFα, IL‐17, IL‐10, TGF‐ß, MIP‐1α, MMP‐9, TIMP‐1, COL1α1, VEGF‐A, FGF‐2 TLR‐2, and TLR‐4 was quantified using qRT‐PCR.

Results

Thirty‐five patients agreed to the surgery and 12‐week biopsy. Twenty‐two patients had mRNA of sufficient quality for analysis. Ten were fitted with a BAHS using the minimally invasive Ponto surgery technique. Twelve were fitted with a BAHS using the linear incision technique with soft‐tissue preservation. Five biopsies were obtained during episodes of inflammation. The post‐implantation mRNA expression of IL‐1β (P = .002), IL‐8 (P = .003), MMP9 (P = .005), TIMP‐1 (P = .002), and COL1α1 (P < .001) was significantly up‐regulated. IL‐6 (P = .009) and FGF‐2 (P = .004) mRNA expression was significantly down‐regulated after implantation. Within patients, no difference between post‐implantation mRNA expression (at 12 weeks) and when inflammation was observed. Between patients, the expression of IL‐1β (P = .015) and IL‐17 (P = .02) was higher during cases of inflammation compared with patients who had no inflammation at 12‐week follow‐up.

Conclusions

As part of a randomized, prospective, clinical trial, the present study reports the molecular profile of selected cytokines in the soft tissue around BAHS. Within the limit of this study, the results showed that 12 weeks after BAHS implantation the gene expression of some inflammatory cytokines (IL‐8 and IL‐1β) is still relatively high compared with the baseline, steady‐state, expression. The up‐regulation of anabolic (COL1α1) and tissue‐remodeling (MMP‐9 and TIMP1) genes indicates an ongoing remodeling process after 12 weeks of implantation. The results suggest that IL‐1β, IL‐17, and TNF‐α may be interesting markers associated with inflammation.

The clinical outcome and microbiological profile of bone-anchored hearing systems (BAHS) with different abutment topographies: a prospective pilot study

Purpose

In this prospective clinical pilot study, abutments with different topologies (machined versus polished) were compared with respect to the clinical outcome and the microbiological profile. Furthermore, three different sampling methods (retrieval of abutment, collection of peri-abutment exudate using paper-points, and a small peri-abutment soft-tissue biopsy) were evaluated for the identification and quantification of colonising bacteria.

Methods

Twelve patients, seven with machined abutment and five with polished abutment, were included in the analysis. Three different sampling procedures were employed for the identification and quantification of colonising bacteria from baseline up to 12 months, using quantitative culturing. Clinical outcome measures (Holgers score, hygiene, pain, numbness and implant stability) were investigated.

Results

The clinical parameters, and total viable bacteria per abutment or in tissue biopsies did not differ significantly between the polished and machined abutments. The total CFU/mm² abutment and CFU/peri-abutment fluid space of anaerobes, aerobes and staphylococci were significantly higher for the polished abutment. Anaerobic bacteria were detected in the tissue biopsies before BAHS implantation. Anaerobes and Staphylococcus spp. were detected in all three compartments after BAHS installation. For most patients (10/12), the same staphylococcal species were found in at least two of the three compartments at the same time-point. The common skin coloniser Staphylococcus epidermidis was identified in all patients but one (11/12), whereas the pathogen Staphylococcus aureus was isolated in five of the patients. Several associations between clinical and microbiological parameters were found.

Conclusions

There was no difference in the clinical outcome with the use of polished versus machined abutment at 3 and 12 months after implantation. The present pilot trial largely confirmed a suitable study design, sampling and analytical methodology to determine the effects of modified BAHS abutment properties.

Level of evidence

2. Controlled prospective comparative study.

Electronic supplementary material

The online version of this article (10.1007/s00405-018-4946-z) contains supplementary material, which is available to authorized users.

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.

[Transcutaneous osseointegrated prosthesis (TOP) after limb amputation : Status quo and perspectives]

The majority of transfemoral and transtibial amputees can be functionally fitted with conventional suspension sockets; however, due to socket problems using conventional stump care, 60% of the patients have limited function and even in younger patients approximately one sixth are unable to wear the prosthesis daily. After the introduction of transcutaneous osseointegrated prostheses (TOP) the inherent problems of socket-stump care can be avoided for these patients. Against this background this article reviews the recent clinical development of TOP in Sweden, Germany, the Netherlands, Australia and USA currently in nine centers. Unanimously, all groups show that TOP enables physiological weight bearing, improved range of motion in the proximal joint, as well as osseoperceptive sensory feedback and better control of the artificial limb. Likewise, there is agreement that as a rule that there is a clinically less relevant superficial contamination of the stoma. Furthermore, TOP is nowadays also used for transhumeral amputees and after thumb amputation and the development of the indications for this technique are increasing. Future aspects include novel treatment options using implanted intramedullary electrodes allowing permanent and unlimited bidirectional communication with the human body (osseointegrated human-machine gateway). This could possibly realize an innovative form of prosthesis control as well as the combination of TOP and targeted muscle reinnervation (TMR) surgery to create more advanced prosthesis systems for upper and lower extremity amputees.

Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review

Bone-anchored limb prostheses allow for the direct transfer of external loads from the prosthesis to the skeleton, eliminating the need for a socket and the associated problems of poor fit, discomfort, and limited range of movement. A percutaneous implant system for direct skeletal attachment of an external limb must provide a long-term, mechanically stable interface to the bone, along with an infection barrier to the external environment. In addition, the mechanical integrity of the implant system and bone must be preserved despite constant stresses induced by the limb prosthesis. Three different percutaneous implant systems for direct skeletal attachment of external limb prostheses are currently clinically available and a few others are under investigation in human subjects. These systems employ different strategies and have undergone design changes with a view to fulfilling the aforementioned requirements. This review summarises such strategies and design changes, providing an overview of the biomechanical characteristics of current percutaneous implant systems for direct skeletal attachment of amputation limb prostheses.

Staphylococcal biofilm gene expression on biomaterials - A methodological study

The combination of increased healthcare access, universal aging, and infallible therapy demands, synergistically drive the need for the development of biomaterial technologies that mitigate the challenge of biomaterial-associated infections (BAI). Staphylococcus epidermidis and Staphylococcus aureus account for the majority of BAI due to their ability to accumulate in adherent multilayered biofilm. This investigation details the development of gene expression assays to evaluate the genetic processes of attachment, accumulation, maturation, and dispersal phases of biofilms on biomaterials in vitro, while abiding by the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines. The biofilm formation of S. epidermidis on polyurethane (PU) central venous catheters and S. aureus on machined titanium (Ti) was examined in terms of gene expression at early and late time points. The results provided insight into how each stage of biofilm formation is orchestrated over time on these biomaterials in vitro. Furthermore, the results suggested that mechanical RNA extraction, organic solvents, elimination of genomic DNA, and preamplification are advisable strategies to implement for biofilm gene expression analysis. It is concluded that this method can be employed for the assessment of biofilm-biomaterial interactions at the molecular level. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3400-3412, 2017.

The clinical, radiological, microbiological, and molecular profile of the skin-penetration site of transfemoral amputees treated with bone-anchored prostheses

The breach of the skin barrier is a critical issue associated with the treatment of individuals with transfemoral amputation (TFA) using osseointegrated, percutaneous titanium implants. Thirty TFA patients scheduled for abutment exchange or removal were consecutively enrolled. The aims were to determine the macroscopic skin signs, the presence of bacteria and the gene expression in abutment‐adherent cells and to conduct correlative and comparative analyses between the different parameters. Redness and a granulation ring were present in 47% of the patients. Bacteria were detected in 27/30 patients, commonly in the bone canal. Staphylococcus aureus, coagulase‐negative staphylococci, streptococci, and Enterococcus faecalis were the most common. A positive correlation was found between TNF‐α expression and the detection of S. aureus. Staphylococcus aureus together with other bacterial species revealed a positive relationship with MMP‐8 expression. A negative correlation was demonstrated between the length of the residual femur bone and the detection of a granulation ring and E. faecalis. A positive correlation was revealed between fixture loosening and pain and the radiological detection of endosteal bone resorption. Fixture loosening was also correlated with the reduced expression of interleukin‐10 and osteocalcin. It is concluded that several relationships exist between clinical, radiological, microbiological, and molecular assessments of the percutaneous area of TFAs. Further long term studies on larger patient cohorts are required to determine the precise cause‐effect relationships and unravel the role of host‐bacteria interactions in the skin, bone canal and on the abutment for the longevity of percutaneous implants as treatment of TFA. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 578–589, 2017.