[Endo-exo prostheses : Osseointegrated percutaneously channeled implants for rehabilitation after limb amputation]

Transtibial osseointegration following unilateral traumatic amputation: An observational study of patients with at least two years follow-up

IMPORTANCE

Most patients use a traditional socket prosthesis (TSP) to ambulate independently following transtibial amputation. However, these patients generally require prosthesis repairs more than twice annually and an entirely new prosthesis every two years. Furthermore, transtibial amputation patients have four times the skin ulceration rate of transfemoral patients, prompting more frequent prosthesis refitting and diminished use. Trans-Tibial osseointegration (TTOI) is a promising technique to address the limitations of TSP, but remains understudied with only four cohorts totaling 41 total procedures reported previously. Continued concerns regarding the risk of infection and questions as to functional capacity postoperatively have slowed adoption of TTOI worldwide.

OBJECTIVE

This study reports the changes in mobility, quality of life (QOL), and the safety profile of the largest described cohort of patients with unilateral TTOI following traumatic amputation.

DESIGN

Retrospective observational cohort study. The cohort consisted of patients with data outcomes collected before and after osseointegration intervention.

SETTING

A large, tertiary referral, major metropolitan center.

PARTICIPANTS

Twenty-one skeletally mature adults who had failed socket prosthesis rehabilitation, with at least two years of post-osseointegration follow-up.

MAIN OUTCOMES AND MEASURES

Mobility was evaluated by K-level, Timed Up and Go (TUG), and Six Minute Walk Test (6MWT). QOL was assessed by survey: daily prosthesis wear hours, prosthesis problem experience, general contentment with prosthesis, and Short Form 36 (SF36). Adverse events included any relevant unplanned surgery such as for infection, fracture, implant loosening, or implant failure.

RESULTS

All patients demonstrated statistically significant improvement post osseointegration surgery with respect to K-level, TUG, 6MWT, prosthesis wear hours, prosthesis problem experience, general prosthesis contentment score, and SF36 Physical Component Score (p < 0.01 for all). Three patients had four unplanned surgeries: two soft tissue refashionings, and one soft tissue debridement followed eventually by implant removal. No deaths, postoperative systemic complications, more proximal amputations, or periprosthetic fractures occurred.

CONCLUSIONS AND RELEVANCE

TTOI is likely to confer mobility and QOL improvements to patients dissatisfied with TSP rehabilitation following unilateral traumatic transtibial amputation. Adverse events are relatively infrequent and not further disabling. Judicious use of TTOI seems reasonable for properly selected patients.

LEVEL OF EVIDENCE

2 (Therapeutic investigation, Observational study with dramatic effect).

Reliable in vitro method for the evaluation of the primary stability and load transfer of transfemoral prostheses for osseointegrated implantation

Osseointegrated transfemoral prostheses experience aseptic complications with an incidence between 3% and 30%. The main aseptic risks are implant loosening, adverse bone remodeling, and post-operative periprosthetic fractures. Implant loosening can either be due to a lack of initial (primary) stability of the implant, which hinders bone ingrowth and therefore prevents secondary stability, or, in the long-term, to the progressive resorption of the periprosthetic bone. Post-operative periprosthetic fractures are most often caused by stress concentrations. A method to simultaneously evaluate the primary stability and the load transfer is currently missing. Furthermore, the measurement errors are seldom reported in the literature. In this study a method to reliably quantify the bone implant interaction of osseointegrated transfemoral prostheses in terms of primary stability and load transfer was developed, and its precision was quantified. Micromotions between the prosthesis and the host bone and the strains on the cortical bone were measured on five human cadaveric femurs with a typical commercial osseointegrated implant. To detect the primary stability of the implant and the load transfer, cyclic loads were applied, simulating the peak load during gait. Digital Image Correlation was used to measure displacements and bone strains simultaneously throughout the test. Permanent migrations and inducible micromotions were measured (three translations and three rotations), while, on the same specimen, the full-field strain distribution on the bone surface was measured. The repeatability tests showed that the devised method had an intra-specimen variability smaller than 6 μm for the translation, 0.02 degrees for the rotations, and smaller than 60 microstrain for the strain distribution. The inter-specimen variability was larger than the intra-specimen variability due to the natural differences between femurs. Altogether, the measurement uncertainties (intrinsic measurement errors, intra-specimen repeatability and inter-specimen variability) were smaller than critical levels of biomarkers for adverse remodelling and aseptic loosening, thus allowing to discriminate between stable and unstable implants, and to detect critical strain magnitudes in the host bone. In conclusion, this work showed that it is possible to measure the primary stability and the load transfer of an osseointegrated transfemoral prosthesis in a reliable way using a combination of mechanical testing and DIC.

Complications Following Osseointegrated Transfemoral and Transtibial Implants: A Systematic Review

Lower limb amputation is a common orthopedic surgery in the United States and can be performed either above or below the knee. Prosthetics are typically externally fitted to the patient's residual stump; however, osseointegrated implants offer a potential alternative to this process. Transcutaneous limb osseointegration involves the intramedullary anchoring of an implant that can later attach to a prosthetic via a stoma in the residual limb. There are proposed benefits to this, including decreased skin and soft tissue complications as well as an increased sense of stability. As this is a relatively new procedure, the complications and efficacy are not well supported by the literature at this time. The primary aim of this analysis was to synthesize the currently available data on transfemoral and transtibial osseointegration in order to improve our understanding of the potential complications of the procedure. A literature search was performed in the following databases: Biomedical Reference Collection, CINAHL, Cochrane Library, and PubMed/MEDLINE. Articles were screened by three independent reviewers for studies written or available in English, study design, and study outcomes, including complications. No filter was applied for publication date, publication national origin, or sample size. A total of 20 articles were selected for the final qualitative analysis. This review demonstrates an overall low or non-inferior rate of both minor and severe complications in transtibial and transfemoral osseointegration. This procedure should be considered as an option during preoperative planning in the context of above-the-knee and below-the-knee amputations. However, continued studies with larger sample sizes and extended postoperative follow-up are necessary for a greater strength of recommendation.

Transcutaneous Osseointegrated Prosthesis Systems (TOPS) for Rehabilitation After Lower Limb Loss: Surgical Pearls

Background

The biology of osseointegration of any intramedullary implant depends on the design, the press-fit anchoring, and the loading history of the endoprosthesis. In particular, the material and surface of the endoprosthetic stem are designed to stimulate on- and in-growth of bone as the prerequisite for stable and long-lasting integration1-8. Relative movement between a metal stem and the bone wall may stimulate the formation of a connective-tissue interface, thereby increasing the risk of peri-implant infections and implant loss9-12. The maximum achievable press-fit (i.e., the force closure between the implant and bone wall) depends on the diameter and length of the residual bone and thus on the amputation level. Beyond this, the skin-penetrating connector creates specific medical and biological challenges, especially the risk of ascending intramedullary infections. On the one hand, bacterial colonization of the skin-penetrating area (i.e., the stoma) with a gram-positive taxon is obligatory and almost impossible to avoid9,10. On the other hand, a direct structural and functional connection between the osseous tissue and the implant, without intervening connective tissue, has been shown to be a key for infection-free osseointegration11,12.

Description

We present a 2-step implantation process for the standard Endo-Fix Stem (ESKA Orthopaedic Handels) into the residual femur and describe the osseointegration of the prosthesis13. In addition, we demonstrate the single-step implantation of a custom-made short femoral implant and a custom-made humeral BADAL X implant (OTN Implants) in a patient who experienced a high-voltage injury with the loss of both arms and the left thigh. Apart from the standard preparation procedures (e.g., marking the lines for skin incisions, preparation of the distal part of the residual bone), special attention must be paid when performing the operative steps that are crucial for successful osseointegration and utilization of the prosthesis. These include shortening of the residual bone to the desired length, preparation of the intramedullary cavity for hosting of the prosthetic stem, precise trimming of the soft tissue, and wound closure. Finally, we discuss the similarities and differences between the Endo-Fix Stem and the BADAL X implant in terms of their properties, intramedullary positioning, and the mechanisms leading to successful osseointegration.

Alternatives

Socket prostheses for transfemoral or transtibial amputees have been the gold standard for decades. However, such patients face many challenges to recover autonomous mobility, and an estimated 30% of all amputees report unsatisfactory rehabilitation and 10% cannot use a socket prosthesis at all.

Rationale

Transcutaneous osseointegrated prosthetic systems especially benefit patients who are unable to tolerate socket suspension systems, such as those with short residual limbs and/or bilateral limb loss. The use of a firmly integrated endoprosthetic stem allows patients and surgeons to avoid many of the limitations associated with conventional socket prostheses, such as the need to continually fit and refit the socket to match an ever-changing stump6,14-19. Discussion between patients who are considering an osseointegrated prosthesis and those who have already received one ("peer patients") has proven to be a powerful tool to prevent unrealistic expectations. Patients with a transhumeral amputation especially benefit from the stable connection between the residual limb and exoprosthesis. Motion of the affected and even the contralateral shoulder is no longer impaired, as straps and belts are dispensable. Furthermore, transmission of myoelectric signals from surrounding muscles to the prosthesis is fundamentally improved. However, comorbidities such as diabetes mellitus or peripheral arterial disease require careful counseling, even if these conditions were not responsible for the loss of the limb. Transcutaneous osseointegrated prosthetic systems for replacement of an upper or lower limb might not be an option in patients who are unable, for any reason, to take adequate care of the stoma.

Expected Outcomes

Despite subtle differences between the systems utilized for the intramedullary anchoring of the prosthetic stem, all data indicate that mobility and quality of life significantly increase while the frequency of stoma infections is remarkably low as long as the patient is able to follow simple postoperative care protocols2-5,9,10,13-19.

Important Tips

The impaction pressure of the implant depends on the diameter of the implant and the quality of the residual bone (i.e., the time interval between the amputation and the implantation of the prosthetic stem). The extent of reaming of the inner cortex of the residual bone must be adapted to these conditions. The standard Endo-Fix Stem and BADAL X implant are both slightly curved to adapt to the physiological shape of the femur. Thus, the surgeon must be sure to insert the implant in the right position and at the correct rotational alignment. When preparing a short femoral stump, carefully identify the exact transection level in order to obtain enough bone stock to anchor the implant in the correct intramedullary position for an additional locking screw into the femoral neck and head. Depending on the residual length of the humerus and the press-fit stability of the implant, the utilization of locking screws is optional, as a notch at the distal end of the implant guarantees primary rotational stability.

Acronyms and Abbreviations

TOPS = transcutaneous osseointegrated prosthesis systemsEEP = endo-exo prosthesisMRSA = methicillin-resistant staphylococcus aureusa.p. = anteroposteriorK-wire = Kirschner wireCT = computed tomographyDCA = double conus adapterOFP = osseointegrated femur prosthesis.

Force transmission capacity of the lower limb during walking of amputees with bone-anchored prostheses compared with socket prostheses and persons with hip replacements

BACKGROUND

Restoring the ability to walk with a prosthesis is considered a fundamental rehabilitation goal after transfemoral amputation. An essential prerequisite for achieving this goal is adequate force transmission between the prosthesis and the body. Does bone anchorage of an artificial limb permit a more normal force transmission?

METHODS

Data of 15 healthy subjects, nine amputees fitted with bone-anchored prostheses, nine amputees using socket prostheses, and 18 patients with a total hip replacement were included in this multicenter, observational study. Ground reaction force was measured using Kistler force plates. Kinematics was recorded with 12 Vicon Bonita cameras. Subjects were instructed to walk at three different speeds: first at their self-selected, then at slow, and finally at fast speed.

FINDINGS

Self-selected walking speeds of subject groups were significantly different, osseointegrated amputees walked the slowest. The lowest ground reaction force was measured for osseointegrated amputees on the prosthetic side, who also showed the highest force on their contralateral side. Patients with hip replacements showed values similar as healthy subjects. The vertical center of gravity movement was specific for each subject group.

INTERPRETATION

The force transmission capacity of the bone-anchored prosthetic leg is limited during walking and is lower than both in socket prostheses users without symptoms and patients with total hip replacement. Therefore, active amputees well fitted with a socket prosthesis who consider a transition to bone-anchorage should be advised that their walking speed may decrease with high probability, and that their self-selected walking speed may even be slower than 3 km/h.

In vitro and in silico methods for the biomechanical assessment of osseointegrated transfemoral prostheses: a systematic review

The amputee population according to the World-Health-Organization is about 40 million. However, there is a high abandon rate of socket prostheses for the lower limb (25%-57%). The direct connection between the external prosthesis and the patient's bone makes osseointegrated prostheses for transfemoral amputees advantageous (e.g., improvement of the motor control) compared to socket prostheses, which are currently the gold standard. However, similarly to other uncemented prostheses, the osseointegrated ones are at risk of aseptic loosening and adverse bone remodelling caused by stress-shielding. The preclinical assessment of these prostheses has already been evaluated using different methods which did not provide unanimous and comparable evidence. To compare data from different investigations, a clear and detailed overview of the methods used to assess the performance is necessary. In this review 17 studies investigating the primary stability, stress shielding and stress concentration of osseointegrated transfemoral prostheses are examined. Primary stability consists in the biomechanical stability upon implant insertion. Primary stability is assessed measuring extraction force (either with a pull-out or a push-out test) and micromotion at the interface between the implant and the host bone with LVDT (in vitro test) or numerical models. Stress-shielding causes adaptive changes in the bone density around metal implants, and thus in the bone strength and stiffness. Stress-shielding is assessed with strain gauges or numerical models measuring the load transfer and the strain distribution on the surface of the femur, and between the implant and the bone respectively. Stress concentration can lead to the formation of cracks inside the bone, resulting in fractures. The stress concentration is assessed measuring the load transfer and the strain energy density at the interface between the implant and the bone, using numerical models. As a result, a global view and consensus about the methods are missing from all these tests. Indeed, different setup and loading scenario were used in the in vitro test, while different model parameters (e.g., bone properties) were used in the numerical models. Once the preclinical assessment method is established, it would be important to define thresholds and acceptance criteria for each of the possible failure scenarios investigated.

Osseoperception in transcutaneous osseointegrated prosthetic systems (TOPS) after transfemoral amputation: a prospective study

BACKGROUND

Endo-exo prosthetics (EEP), which belongs to the transcutaneous osseointegrated prosthetic systems (TOPS), provides an alternative bone-anchored rehabilitation method for transfemoral amputees. It led to the question of whether transmitted forces from prosthetic feet are perceptible by osseoperception resulting in proprioceptive feedback of ground conditions.

OBJECTIVES

The following hypotheses emerged for our trial with the null hypothesis: EEP fitting after transfemoral amputation does not influence osseoperception. Alternative hypothesis 1: EEP patients achieve better osseoperception results than transfemoral amputees fitted with socket prosthesis. Alternative hypothesis 2: EEP carriers achieve comparable results with regards to their osseoperception as non-amputees.

METHODS

N = 25 patients with EEP (mean age = 50,6 ± 9,4, male/female = 15/10) N = 25 patients with socket prostheses (mean age = 52,6 ± 13,1, male/female = 19/6) and N = 25 healthy volunteers were included in the experimental case-control study. In three blinded test modules (V1, V2, V3), the participants had to identify different degrees of shore hardness (c) of different materials (rubber balls (shore = 5-25c), foam cushions (shore = 5-30c), foam mats (shore = 5-30c) with their prosthetic foot (or a personally defined foot in healthy volunteers) without footwear and had to rank them into the correct order according to their tactile sensation and the degree of hardness. A maximum of 10 points could be scored per run.

RESULTS

This experimental observational study included N = 75 participants. The mean age for the entire cohort was 42.8 ± 16.6 years and the BMI was 26.0 ± 4.8. Our results show a significant level of differences in tactile osseoperception between all groups (p < 0.001). A correlation between the mean values of V1-3 and the PMQ2.0 as well as the mean values of K-Level and the prosthesis wearing time per day showed for PMQ (r = 0.387, p = 0.006) and K-level (r = 0.448, p = 0.001) which is a moderate effect according to Cohen.

CONCLUSION

Our study results suggest that the EEP treatment can lead to an improvement in tactile sensory perception via the bone-anchored implant, which can lead to an increase in quality of life and improved gait safety.

[Functional rehabilitation after transfemoral amputation : Shaft prosthesis or endo-exo prosthesis?]

BACKGROUND

After transfemoral amputation a prosthesis is required to restore autonomous standing and bipedal locomotion. Attachment of the prosthesis can be achieved either classically via socket suspension with a shaft in the stump or directly via implantation of an intramedullary transcutaneous femoral prosthesis (osseointegrated prosthesis).

AIM

A fully instrumented gait analysis should enable objectification of the anticipated advantages of the EEP with respect to the gait pattern and individual mobility.

MATERIAL AND METHODS

In two patients with a unilateral transfemoral amputation a comprehensive gait analysis was carried out prior to and 6 months (patient 1) or 11 and 20 months (patient 2) after switching from a socket prosthesis to an EEP. This was carried out in the Gait Realtime Analysis Interactive Lab (GRAIL), a fully instrumented gait laboratory with virtual reality and enables assessment close to the conditions of daily life.

RESULTS

In both cases the gait analysis confirmed the advantages associated with an EEP for the transmission of force to the prosthesis and the accompanying improvement in gait symmetry.

Comparison of functional outcome and patient satisfaction between patients with socket prosthesis and patients treated with transcutaneous osseointegrated prosthetic systems (TOPS) after transfemoral amputation

PURPOSE

The aim of this retrospective analysis was to investigate and evaluate differences in functional outcome and satisfaction of patients treated with a TOPS and patients using socket prosthesis after transfemoral amputation.

METHODS

This retrospective comprehensive analysis included patients from a single hospital, and was conducted between February 2017 and December 2018. Overall n = 139 patients with prosthesis were included and divided into two comparable groups (socket- and TOPS group). Incomplete data sets were excluded. This led to n = 36 participants for the socket- and n = 33 for the TOPS group. Functional outcome and satisfaction were evaluated by Patient Reported Outcome Measures (PROMs). The used PROMs were: Questionnaire for Persons with a Transfemoral Amputation (Q-TFA), EQ5D-5L, Satisfaction with Prosthesis Questionnaire (SAT-PRO), Prosthesis Mobility Questionnaire (PMQ 2.0) and Functional Independence Measure (FIM).

RESULTS

Significant results in favor of TOPS patients were identified for the EQ-5D 5L (p = 0.004), Q-TFA (p = 0.000), SAT-PRO (p = 0.000) and PMQ 2.0 (p = 0.000). For FIM, no statistical significance was found (p = 0.318).

CONCLUSION

In this study, transfemoral amputees treated with an osseointegrated prosthetic attachment (TOPS) showed significantly higher scores for mobility and satisfaction. This demonstrates the high potential of TOPS in the prosthetic treatment of patients with transfemoral amputation with regard to their functional abilities in daily life.

Rehabilitation of Patients with Osseointegrated Prosthesis after Transfemoral Amputation - Literature-based Recommendation for Postoperative Rehabilitative Procedure

BACKGROUND

Osseointegrative implantation after amputation of the lower extremity is a special treatment option. Physiotherapeutic treatment is important for the functional outcome. This study systematically evaluated existing follow-up treatment protocols to establish a literature-based recommendation for postoperative rehabilitation procedures.

METHODOLOGY

A PubMed literature search was conducted on December 10, 2020, using the following search terms: (osseo-integrat* OR endo-exo OR boneanchored OR bone anchored) AND (prosthe*) AND (leg OR lower limb* OR lower extremit* OR transfem* OR transtib*) AND (rehabilitation). 113 publications were found in this context. 10 of them met inclusion criteria. The Cochrane risk of bias tool was used to determine the publications' quality.

RESULTS

Three systematic rehabilitation protocols have been described: Osseointegrated Prostheses for the Rehabilitation of Amputees protocol, Osseointegration Group of Australia Accelerated protocol and Radboud Amputation: rehabilitation protocol for endo-exo femoral prosthesis. There are clear differences in the duration of the rehabilitation protocols. The quality of published studies is limited due to the high risk of bias and low evidence levels (mainly III - V). A concept for long-term rehabilitation has not been described yet.

CONCLUSIONS

There are various protocols for rehabilitation after treatment with osseointegrative prosthesis. Gradually increasing axial weight bearing started shortly after surgery; step-by-step gait training, adaptation of the prosthesis to the new biomechanics and critical patient selection and pre-operative training have been proven useful for successful rehabilitation. Controlled comparative studies, standardised outcome measurements or comparative studies between different protocols are not available. Models for multi-level long-term care have not been described in the literature so far.

Transtibial Osseointegration for Patients with Peripheral Vascular Disease: A Case Series of 6 Patients with Minimum 3-Year Follow-up

The management of peripheral vascular disease (PVD) can require amputation. Osseointegration surgery is an emerging rehabilitation strategy for amputees. In this study, we report on 6 patients who had PVD requiring transtibial amputation (PVD-TTA) and either simultaneous or subsequent osseointegration (PVD-TTOI).

Methods

Six patients (aged 36 to 84 years) with transtibial amputation and preexisting PVD underwent osseointegration between 2014 and 2016 and were followed for 3 to 5 years. Pre- and postoperative clinical and functional outcomes (pain, prosthesis wear time, mobility, walking ability, and quality of life) and adverse events (infection, fracture, implant failure, revision surgery, additional amputation, and death) were prospectively recorded.

Results

All patients' mobility improved following osseointegration. Three patients initially had required the use of a wheelchair, precluding baseline walking tests; the other 3 were classified as K level 1 or 2, with mean baseline Timed Up and Go (TUG) test = 14.0 ± 2.2 s and 6-Minute Walk Test (6MWT) = 262 ± 75 m. At the time of the latest follow-up, all patients were K level 2 or 3; mean TUG = 12.7 ± 7.2 s and 6MWT = 353 ± 148 m. Four patients wore their prosthesis ≥16 hours daily. Three patients had superficial soft-tissue infections. One other patient experienced recurrent infections 2.8 years after osseointegration requiring debridements and transfemoral amputation; the patient died 2 days following surgery from myocardial infarction caused by coronary atherosclerosis.

Conclusions

All 6 patients who underwent PVD-TTOI in this case series survived through 2 years. Patients who initially had used a wheelchair achieved and maintained independent, unaided ambulation until PVD-related impairments in the contralateral leg occurred in 1 patient. Patients previously using a traditional socket prosthesis reported improvement in mobility and quality of life. One patient's death underscores the importance of careful patient selection. However, marked improvement in the other 5 patients suggests cautious optimism that PVD-TTA is not an absolute osseointegration contraindication. Conscientious further investigation seems appropriate.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Quality of life of persons with transfemoral amputation: Comparison of socket prostheses and osseointegrated prostheses

BACKGROUND

Until recently, no study had compared the quality of life of persons with transfemoral amputation treated with osseointegration to socket prosthesis users.

OBJECTIVES

Comparison of quality of life in two types of prostheses users: a cohort of patients with osseointegration and patients equipped with a socket prosthesis who were group-matched for age, body mass index and mobility grade.

STUDY DESIGN

A cross-sectional study that compared METHODS:: The quality of life of 39 participants (22 in the osseointegration group and 17 in the socket prosthesis group) was measured using the Questionnaire for Persons with Transfemoral Amputation (Q-TFA) and European Questionnaire 5-dimension 3-level (EQ-5D-3L) surveys.

RESULTS

Compared with the socket prosthesis group, the osseointegration group had a significantly higher 'Global' score (p = 0.022) and a significantly lower 'Problem' score (p < 0.001) of the Q-TFA. The 'Mobility' (p = 0.051) and 'Use' scores (p = 0.146) of the Q-TFA, the EQ-5D-3L index (p = 0.723), and EQ-5D visual analog scale (p = 0.497) showed no significant differences between groups.

CONCLUSIONS

Patients with osseointegration experienced less prosthesis-associated problems than socket prosthesis users and had a higher prosthesis-associated quality of life when assessed with the Q-TFA. General quality of life, as assessed with the EQ-5D-3L, was not different between groups.

Preoperative femoral abduction angle correlates with initial postoperative lateral hip pain after transcutaneous osseointegrated prosthetic system (TOPS) in transfemoral amputees

PURPOSE

To analyse whether a preoperative femoral abduction angle (FAA) correlates with postoperative initial lateral hip pain (LHP) in above-knee amputees (AKA) treated with transcutaneous osseointegrated prosthetic system (TOPS).

METHODS

Pre- and postoperative long-leg radiographs of eighteen unilateral AKA (mean age 51.55y ± 12.16) were retrospectively measured. FAA was measured on both sides. Pain intensity of LHP was measured by numeric rating scale (NRS) preoperatively and every week for four weeks from the first day of weight loading. Pearson's r was calculated for correlation. Furthermore, odds ratio for LHP ≥ 5/10 NRS and relative FAA > 13° was calculated.

RESULTS

FAA significantly decreased in the postoperative period (pre/post. 15.33° ± 4.22; p < 0.001). Median LHP was 0/10 NRS (min.0, max.3) preoperatively and 4/10 NRS (min.2, max. 7, p < 0.001) postoperatively after first loading. Interestingly, it decreased within four weeks to a median of 0.5/10 NRS (min.0, max. 3) without intervention. A strong correlation was seen on the amputated side between preoperative FAA and LHP after loading (r = 0.835, p < 0.001), as well as the relative FAA to LHP after loading (r = 0.732, p < 0.001) and between the gap of pre- to postoperative FAA and LHP. Odds ratio for LHP ≥ 5/10 and relative FAA > 13° was 6.4 (95%CI = 0.55; 74.89).

CONCLUSION

The preoperative FAA strongly correlates with postoperative LHP. Surgeons should be aware of high risk of LHP that can limit prosthetic training. High preoperative FAAs should be realised in the decision meeting of TOPS implantation and pre-rehabilitative reduction of the FAA should be taken into consideration.

Osseointegrated reconstruction and rehabilitation of transtibial amputees: the Osseointegration Group of Australia surgical technique and protocol for a prospective cohort study

INTRODUCTION

Lower extremity amputation uniformly impairs a person's vocational, social and recreational capacity. Rehabilitation in traditional socket prostheses (TSP) is associated with a spectrum of complications involving the socket-residuum interface which lead to reduced prosthetic use and quality of life. Osseointegration has recently emerged as a novel concept to overcome these complications by eliminating this interface and anchoring the prosthesis directly to bone. Though the complications of TSPs affect both transfemoral and transtibial amputees, Osseointegration has been predominantly performed in transfemoral ones assuming a greater benefit/risk ratio. However, as the safety of the procedure has been established, we intend to extend the concept to transtibial amputees and document the outcomes.

METHODS AND ANALYSIS

This is protocol for a prospective cohort study, with patient enrolment started in 2014 and expected to be completed by 2022. The inclusion criteria are age over 18 years, unilateral, bilateral and mixed transtibial amputation and experiencing socket-related problems. All patients receive osseointegrated implants, the type of which depend on the length of the residuum and quality of bone, which are press-fitted into the residual bone. Objective functional outcomes comprising 6-Minute Walk Test, Timed Up-and-Go test and K-level, subjective patient-reported-quality-of-life outcomes (Short Form Health Survey 36, daily prosthetic wear hours, prosthetic wear satisfaction) and adverse events are recorded preoperatively and at postoperative follow-up intervals of 3, 6, 12 months and yearly, and compared with the preoperative values using appropriate statistical tests. Multivariable multilevel logistic regression will be performed with a focus to identify factors associated with outcomes and adverse events, specifically infection, periprosthetic fracture, implant fracture and aseptic loosening.

ETHICS AND DISSEMINATION

The Ethics approval for the study has been received from the University of Notre Dame, Sydney, Australia (014153S). The outcomes of this study will be disseminated by publications in peer-reviewed academic journals and scientific presentations at relevant orthopaedic conferences.

Safety and Performance of Bone-Anchored Prostheses in Persons with a Transfemoral Amputation: A 5-Year Follow-up Study

BACKGROUND

For almost 30 years, bone-anchored prostheses have offered an alternative solution to prosthetic sockets by attaching the artificial limb directly to the femoral residuum by means of an osseointegration implant. Osseointegration implant surgery was introduced in our center in 2009. The aim of the present study is to report on safety, prosthesis-wearing time, and health-related quality-of-life (HRQoL) for patients with femoral bone-anchored prostheses during a 5-year follow-up period.

METHODS

All patients who underwent implantation of a press-fit osseointegration implant between May 2009 and November 2013 were eligible for the present study. Implantation was performed in 2 stages. Adverse events included infectious complications (grade 1 to 4), aseptic loosening, breakage, stoma-redundant tissue, and stoma hypergranulation. Prosthesis-wearing time and HRQoL were measured with the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) prosthetic use score and global score, respectively.

RESULTS

Thirty-nine of 42 eligible patients were included. Thirty patients (77%) presented with some kind of infection (156 events in total), with 148 (95%) events being classified as grade 1 or 2 and 8 events (5%) being classified as grade 3; the latter 8 events occurred in 4 patients. There were no instances of septic loosening. The intramedullary stem of the osseointegration implant broke in 2 patients. In total, soft-tissue refashioning had to be done 30 times in 14 patients. The Q-TFA median prosthetic use and global scores improved significantly from 71 to 100 and from 33 to 75, respectively (p < 0.001).

CONCLUSIONS

Despite the adverse events, patient prosthetic use and HRQoL improved significantly. Grade-1 and 2 infections were frequent but could mostly be treated with nonoperative measures. Most infections seemed to occur in the first 2 years and did not lead to deep infections. Two broken intramedullary stems were revised successfully. Current developments focus on reduction of infectious complications and prevention of osseointegration implant breakage.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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.

Safety, prosthesis wearing time and health-related quality of life of lower extremity bone-anchored prostheses using a press-fit titanium osseointegration implant: A prospective one-year follow-up cohort study

BACKGROUND

We described safety and functional one-year follow-up outcomes of individuals with lower limb amputation treated with bone-anchored prostheses using titanium press-fit osseointegration implants.

METHODS

All consecutive individuals treated between March 2015 and June 2018 with curved osseointegration femur implant (OFI-C) indicated for a long femoral remnant, gamma osseointegration femur implant (OFI-Y) indicated for a short femoral remnant, or osseointegration tibia implant (OTI) were eligible for this study. All adverse events were evaluated, infections were graded as follows: grade 1 and 2: low- and high-grade soft tissue infection, respectively, grade 3: deep bone infection, grade 4: septic implant failure. Functional outcome measures included prosthesis wearing time (PUS), health-related quality of life (GS), and the overall situation as an amputee (GS Q3); evaluated with the Questionnaire of persons with trans-femoral amputation (Q-TFA) before surgery and at one-year follow-up.

RESULTS

Ninety of 91 individuals were included (mean age: 54±14 yrs, 26 females); treated with 53, 16 and 21 OFI-C, OFI-Y and OTI, respectively. Soft tissue infections (grade 1: 11 events, grade 2: 10 events) were treated successfully with antibiotics except in two (OFI-C and OFI-Y), who required additional surgery due to recurrent stoma irritation and peri-stoma abscess drainage. One individual with dysvascular amputation (OTI) developed septic implant loosening and occlusion of the femoral artery resulting in a transfemoral amputation. No aseptic loosening's occurred. One individual (OFI-Y) required stoma surgical refashioning due to soft tissue redundancy. At baseline mean ±SD and median (25th to 75th PCTL) Q-TFA PUS and GS were 52±39, 52(7-90) and 40±19, 42(25-50) and improved significantly to 88±18, 90 (90-100) and 71±15, 75 (67-83) at one-year follow-up. The GS Q3 improved over time.

CONCLUSION

Titanium osseointegration implants can be safely used within a one-year follow-up period. The performance improved compared to the use of a socket-suspended prosthesis.

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.

Epidermal growth factor receptor genes are overexpressed within the periprosthetic soft-tissue around percutaneous devices: A pilot study

Epidermal downgrowth around percutaneous devices produce sinus tracts, which then accumulate bacteria becoming foci of infection. This mode to failure is epidermal-centric, and is accelerated by changes in the chemokines and cytokines of the underlying periprosthetic granulation tissue (GT). In order to more fully comprehend the mechanism of downgrowth, in this 28-day study, percutaneous devices were placed in 10 Zucker diabetic fatty rats; 5 animals were induced with diabetes mellitus II (DM II) prior to the surgery and 5 animals served as a healthy, nondiabetic cohort. At necropsy, periprosthetic tissues were harvested, and underwent histological and polymerase chain reaction (PCR) studies. After isolating GTs from the surrounding tissue and extracting ribonucleic acids, PCR array and quantitative-PCR (qPCR) analyses were carried-out. The PCR array for 84 key wound-healing associated genes showed a five-fold or greater change in 31 genes in the GTs of healthy animals compared to uninjured healthy typical skin tissues. Eighteen genes were overexpressed and these included epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR). Thirteen genes were underexpressed. When GTs of DM II animals were compared to healthy animals, there were 8 genes overexpressed and 25 genes underexpressed; under expressed genes included EGF and EGFR. The qPCR and immunohistochemistry data further validated these observations. Pathway analysis of genes up-regulated 15-fold or more indicated two, EGFR and interleukin-10, centric clustering effects. It was concluded that EGFR could be a key player in exacerbating the epidermal downgrowth, and might be an effective target for preventing downgrowth.

Complications of bone-anchored prostheses for individuals with an extremity amputation: A systematic review

BACKGROUND

This study aimed to provide an overview of device-related complications occurring in individuals with an upper or lower extremity amputation treated with a screw, press-fit or other type of bone-anchored implant as well as interventions related to these complications.

METHOD

A systematic literature search was conducted in the MEDLINE, Cochrane, EMBASE, CINAHL and Web of Science databases. The included studies reported on device-related complications and interventions occurring in individuals with bone-anchored prostheses. The outcomes evaluated were death, infection, bone/device breakage, implant loosening, soft tissue complications, systemic events, antibiotic and surgical treatment. Subgroup analyses were performed for the following groups: a) implant type (screw, press-fit and other types of implants) and b) level of amputation (transfemoral, transtibial and upper extremity amputation).

RESULTS

Of 309 studies, 12 cohort studies were eligible for inclusion, all of which had methodological shortcomings and 12 studies were excluded due to complete overlap of patient data. Implant infection were rare in certain transfemoral implants (screw: 2-11%, press-fit: 0-3%, Compress: 0%) but common in transtibial implants (29%). The same was observed for implant loosening, in transfemoral (screw: 6%, press-fit: 0-3%, Compress: 0%), transtibial implants (29%) as well as for upper extremity implants (13-23%). Intramedullary device breakage were rare in transfemoral implants (screw: 0%, press-fit: 1%, Compress: unknown) but frequent in individuals with transradial implants (27%) and absent in transtibial implants. Soft tissue infections and complications were common and underreported in most articles.

CONCLUSIONS

Major complications (e.g. implant infection, implant loosening and intramedullary device breakage) are rare in transfemoral bone-anchored prosthesis and seem to occur less frequently in individuals with press-fit implants. Minor complications, such as soft tissue infections and complications, are common but are substantially influenced by the learning curve, implant design and surgical technique. Data for patients treated with a transtibial, upper extremity or Compress implant are underreported, precluding definitive conclusions. There is a need for either an international database to report on or a standard core set of complications as well as the need to follow classification systems that result in unequivocal data.

[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.

[The endo-exo prosthesis treatment concept : Improvement in quality of life after limb amputation]

Osseointegrated, percutaneous implants as the force bearer for exoprosthetics after limb amputation have been used in individual cases for clinical rehabilitation of amputees during the past years. Most experience in this field in Germany has been accumulated at the Sana Klinik in Lübeck with the so-called endo-exo prosthesis (EEP) system. The two-step implantation procedure can now be considered as reliable. Following a well-documented learning curve initial soft tissue problems concerning the cutaneous stoma can now be regarded as exceptions. The retrospective examination of the results concerning by now more than 100 patients provided with an endo-exo femoral prosthesis (EEFP) showed a very satisfying outcome concerning objective as well as subjective values, such as duration of daily use and wearing comfort of the exoprosthesis. Regaining the ability of osseoperception due to the intraosseous fixation is described by the patients as a great advantage. The step from a socket prosthesis to an EEP is felt to be a big increase in quality of life by nearly all patients included into the follow-up. Nearly all of the patients questioned would choose an endo-exo prosthesis again. Meanwhile, the success of the EEP resulted in the broadening of indications from above-knee amputations to transtibial as well as transhumeral amputations. The results are likewise encouraging. The use of EEP for the upper limbs leads to substantial improvement in the range of motion of the shoulder joint with the intramedullary anchored percutaneous implant. Furthermore, new pathbreaking possibilities in the fixation of myoelectrically controlled arm prostheses may arise from the EEP technique.

[Function of prosthesis components in lower limb amputees with bone-anchored percutaneous implants : Biomechanical aspects]

BACKGROUND

Bone anchorage of an artificial limb has been proven to be an alternative intervention for amputees when prosthesis use is seriously reduced because of stump problems. Little is known about how prosthesis components interact with bone and joints and which potential the optimum use provides with respect to quality of treatment of leg amputees.

OBJECTIVE

Does osseointegration influence the motor activity of residual limbs differently compared with socket prostheses? How should prosthesis components be aligned? What type of prosthetic knee joints should be preferred in transfemoral amputees?

MATERIAL AND METHODS

Transfer of biomechanical knowledge of socket prosthetics to bone-anchored prostheses. Pilot studies with a limited number of amputees.

RESULTS

Force transmission at the interface between the prosthesis and residual limb stump is completely different for osseointegrated fixation and socket design; however, the number of muscles available for control remains unchanged. Because the iliotibial tract is missing, bending moments of the femur are expected to be greater. Prosthetic alignment is very critical for gait pattern and the basic rules seem to be the same as for socket design. The foot position determines the knee function for below-knee amputees. The position of the femur influences the gait pattern of above-knee amputees. The lowest risk of falls and best functional properties are shown by microprocessor controlled knee joints.

CONCLUSION

Osseointegrated leg prostheses have some biomechanical advantages over the socket design. Since rehabilitation quality is clearly affected the prosthetic alignment has to be done carefully and precisely. As a rule microprocessor controlled knee joints are indicated.