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

Performance-Based Functional Outcomes Twelve and Twenty-Four Months after Transfemoral Osseointegration in Service Members with Traumatic Unilateral and Bilateral Lower Limb Loss

OBJECTIVE

To evaluate functional outcomes at 12-months and 24-months after transfemoral osseointegration (OI), using established performance-based assessments DESIGN: Pre-post observational, single cohort SETTING: Military treatment facility PARTICIPANTS: Forty-seven service members (age=38±9y) with traumatic unilateral (n=22) and bilateral (n=25) lower limb loss. Before OI, n=2 unilateral and n=7 bilateral were not ambulatory on full-length prostheses.

INTERVENTION

Transfemoral OI (two-stage threaded implant) MAIN OUTCOME MEASURES: Six-Minute Walk Test (6MWT), Timed Up and Go (TUG), Four Square Step Test (4SST), [Bilateral] Amputee Mobility Predictor ([B]AMP), Comprehensive High-level Activity Mobility Predictor (CHAMP).

RESULTS

For both unilateral and bilateral cohorts, median performance-based functional outcomes were similar at 12-months and 24-months after vs. before OI: 6MWT (373 and 385 vs. 417m; p>0.31), TUG (9.7 and 9.6 vs. 9.8s; p>0.53), 4SST (9.5 and 10.6 vs. 10.8s; p>0.11), and CHAMP (12.6 and 10.6 vs. 12.3; p>0.44). Median BAMP scores were greater at 12-months (p=0.029) and 24-months (p=0.014) after vs. before OI among the bilateral cohort (30 and 35 vs. 16); median AMP scores were similar (p>0.10) among the unilateral cohort across timepoints (39 and 43 vs. 40). Among the 9 participants not ambulating with full-length prostheses before OI, 8 became capable of ambulation on full-length prostheses after by 24-months after OI.

CONCLUSIONS

While a lack of improvement in these particular outcomes is not exclusively suboptimal, particularly considering median scores at baseline reported here generally exceed other cohorts (both before and sometimes even after OI), these findings contrast with previous self-reported improvements in function after OI among service members with traumatic lower limb loss. As such, these data seemingly emphasize the importance of a comprehensive approach with both subjective and objective (multidisciplinary) outcomes for more fully characterizing OI, particularly within unique patient populations like young service members with traumatic lower limb loss.

Improving quality of life for transfemoral amputees: results from a two-year study of the OPRA implant system and rehabilitation protocol

PURPOSE

Transfemoral amputees face significant functional limitations with traditional socket prostheses. This study evaluates the efficacy and safety of the OPRA (Osseointegrated Prostheses for the Rehabilitation of Amputees) implant system in improving the quality of life for these patients.

METHODS

A retrospective study was conducted on 22 transfemoral amputees (20 male, 2 female; mean age 44.6 years) who underwent OPRA implant surgery between 2019 and 2021. Patients were assessed preoperatively and followed for two years post-surgery. Outcomes were measured using the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA), pain scores, and complication rates.

RESULTS

At two-year follow-up, significant improvements were observed in Q-TFA scores for prosthetic use (30.41 ± 10.90 to 87.68 ± 11.42, p < 0.001), mobility (44.36 ± 15.57 to 71.45 ± 13.72, p < 0.001), problem score (52.40 ± 10.22 to 25.81 ± 9.66, p < 0.001), and global score (43.45 ± 10.87 to 74.95 ± 21.82, p < 0.001). Mean daily prosthesis usage increased from 3.77 ± 2.59 to 13.43 ± 3.76 h (p < 0.001). Complications included minor discharge (67.5%), significant discharge requiring surgical intervention (13.6%), prosthesis removal (9%), and periprosthetic fracture (4.5%).

CONCLUSION

The OPRA implant system significantly improved functional outcomes and quality of life for transfemoral amputees over two years. While complication rates were notable, most were manageable with conservative treatment. These findings suggest that osseointegrated prostheses offer a promising alternative to socket prostheses for suitable candidates, though further research with larger cohorts is warranted to confirm long-term efficacy and safety.

Improved primary stability and load transfer of a customized osseointegrated transfemoral prosthesis compared to a commercial one

BACKGROUND

Transfemoral osseointegrated prostheses, like other uncemented prostheses experience the risk of aseptic loosening and post-operative periprosthetic fractures, with an incidence between 3% and 30%. To date, however, osseointegrated off-the-shelf prostheses are manufactured in a limited number of sizes, and some patients do not meet the strict eligibility criteria of commercial devices. A customized osseointegrated stem was developed and a pre-clinical in vitro investigation of the stem was performed, to evaluate its biomechanical performance.

MATERIALS AND METHODS

Six human cadaveric femurs were implanted with commercial stems, while the six contralateral were implanted with customized stems. Three more femurs that did not meet the eligibility criteria for the commercial stems were implanted with the customized stems. Two different loading scenarios (compression-flexion, and torsion) were simulated to measure the primary implant stability and the load transfer. For both loading scenarios, the displacements of the implant with respect to the host bone, and the strains on the bone surface were measured using digital image correlation (DIC). To measure the pull-out force, a tensile force was applied to the prostheses.

RESULTS

The translational inducible micromotions during the compression-flexion test of the OsteoCustom stem were more than 4 times smaller than the commercial one (p < 0.05). The rotational inducible micromotions of the OsteoCustom stem were more than 3 times smaller than the commercial one (p < 0.05). Similar results were found from the torsional test. The full-field strain distribution of the commercial stem showed a slightly higher strain concentration near the stem tip (maximum principal strain = 1928±127 µɛ) than the OsteoCustom (maximum principal strain = 1758±130 µɛ). Similar results were found for the femurs that did not meet the eligibility criteria for the commercial stems and could be implanted with the OsteoCustom. No statistically significant difference was found in the extraction force between the two groups.

DISCUSSION AND CONCLUSION

These results support the hypothesis that the OsteoCustom stem can offer better primary stability and load distribution compared to commercial implants. The outcome highlighted the potential benefits of the OsteoCustom prosthesis, which is capable of including a wider range of femoral anatomies than the current standard.

Bone-anchored prostheses for transfemoral amputation: a systematic review of outcomes, complications, patient experiences, and cost-effectiveness

Introduction

Bone-anchored prostheses (BAP) are an advanced reconstructive surgical approach for individuals who had transfemoral amputation and are unable to use the conventional socket-suspension systems for their prostheses. Access to this technology has been limited in part due to the lag between the start of a new procedure and the availability of evidence that is required before making decisions about widespread provision. This systematic review presents as a single resource up-to-date information on aspects most relevant to decision makers, i.e., clinical efficacy, safety parameters, patient experiences, and health economic outcomes of this technology.

Methods

A systematic search of the literature was conducted by an information specialist in PubMed, MEDLINE, Embase, CINAHL, Cochrane Library, the Core Collection of Web of Science, CADTH's Grey Matters, and Google Scholar up until May 31, 2023. Peer-reviewed original research articles on the outcomes of clinical effectiveness (health-related quality of life, mobility, and prosthesis usage), complications and adverse events, patient experiences, and health economic outcomes were included. The quality of the studies was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence and ROBINS-I, as appropriate.

Results

Fifty studies met the inclusion criteria, of which 12 were excluded. Thirty-eight studies were finally included in this review, of which 21 reported on clinical outcomes and complications, 9 case series and 1 cohort study focused specifically on complications and adverse events, and 2 and 5 qualitative studies reported on patient experience and health economic assessments, respectively. The most common study design is a single-arm trial (pre-/post-intervention design) with varying lengths of follow-up.

Discussion

The clinical efficacy of this technology is evident in selected populations. Overall, patients reported increased health-related quality of life, mobility, and prosthesis usage post-intervention. The most common complication is a superficial or soft-tissue infection, and more serious complications are rare. Patient-reported experiences have generally been positive. Evidence indicates that bone-anchored implants for prosthesis fixation are cost-effective for those individuals who face significant challenges in using socket-suspension systems, although they may offer no additional advantage to those who are functioning well with their socket-suspended prostheses.

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.

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.

Bone-anchored prostheses for lower limb amputation in a French cohort with 1-15 years of follow-up: implant survival rates, mechanical complications, and reported outcomes

PURPOSE

To evaluate the implant survival rate, mechanical complications, and reported patient outcomes of bone-anchored prostheses for patients with lower limb amputation in France after 1-15 years of follow-up.

METHODS

This retrospective cohort study included patients who underwent surgery at a single center in France between 2007 and 2021. The primary outcomes were the implant survival rate and functional scores assessed by the Questionnaire for Transfemoral Amputees (Q-TFA). Secondary outcomes were adverse events that occurred during follow-up.

RESULTS

The cohort consisted of 20 bone-anchored prostheses in 17 patients. The main level of amputation was transfemoral (82%, n = 14). The main reason for amputation was trauma (n = 15). The mean age at amputation was 32 (range 15-54) years, and the mean age at the first stage of osseointegration was 41 (range 21-58) years. The Kaplan-Meier survival curve showed respective survival rates of 90%, 70%, and 60% at 2, 10, and 15 years. All Q-TFA scores were significantly improved at last the follow-up. Eleven patients (65%) experienced mechanical complications. In total, 37 infectious events occurred in 13 patients (76%), mainly comprising stage 1 infections (68%, n = 25). Only two cases of septic loosening occurred (12%), leading to implant removal.

CONCLUSION

This is the first French cohort of bone-anchored prostheses and among the series with the longest follow-up periods. The findings indicate that bone-anchored prostheses are safe and reliable for amputee patients who have difficulties with classic prostheses.

The Impact of Ultrashort Pulse Laser Structuring of Metals on In-Vitro Cell Adhesion of Keratinocytes

Besides the need for biomaterial surface modification to improve cellular attachment, laser-structuring is favorable for designing a new surface topography for external bone fixator pins or implants. The principle of this study was to observe how bioinspired (deer antler) laser-induced nano-microstructures influenced the adhesion and growth of skin cells. The goal was to create pins that allow the skin to attach to the biomaterial surface in a bacteria-proof manner. Therefore, typical fixator metals, steel, and titanium alloy were structured using ultrashort laser pulses, which resulted in periodical nano- and microstructures. Surface characteristics were investigated using a laser scanning microscope and static water contact angle measurements. In vitro studies with human HaCaT keratinocytes focused on cell adhesion, morphology, actin formation, and growth within 7 days. The study showed that surface functionalization influenced cell attachment, spreading, and proliferation. Micro-dimple clusters on polished bulk metals (DC20) will not hinder viability. Still, they will not promote the initial adhesion and spreading of HaCaTs. In contrast, additional nanostructuring with laser-induced periodic surface structures (LIPSS) promotes cell behavior. DC20 + LIPSS induced enhanced cell attachment with well-spread cell morphology. Thus, the bioinspired structures exhibited a benefit in initial cell adhesion. Laser surface functionalization opens up new possibilities for structuring, and is relevant to developing bioactive implants in regenerative medicine.

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.

Have Surgery and Implant Modifications Been Associated With Reduction in Soft Tissue Complications in Transfemoral Bone-anchored Prostheses?

BACKGROUND

The most frequently occurring adverse events in individuals with a transfemoral amputation treated with a bone-anchored prosthesis are soft tissue infections and stoma-related complications. These soft tissue complications are believed to be influenced by surgical technique and implant design, but little is known about the effect of changes to treatment on these events.

QUESTIONS/PURPOSES

(1) What is the result of surgical technique and implant modifications on the incidence of soft tissue infections and stoma-related complications in transfemoral bone-anchored prosthesis users, depending on whether they had a conventional stoma and a cobalt-chrome-molybdenum (CoCrMo) osseointegration implant (treatment period 2009 to 2013) or a shallower stoma and titanium osseointegration implant (2015 to 2018)? (2) What is the incidence of serious complications, such as bone or implant infection, aseptic loosening, intramedullary stem breakage, and periprosthetic fracture?

METHODS

Between 2009 and 2013, we performed osseointegration implant surgery using a conventional surgical technique and a CoCrMo implant in 42 individuals who had a lower extremity amputation experiencing socket-related problems that resulted in limited prosthesis use. We considered all individuals treated with two-stage surgery with a standard press-fit transfemoral osseointegration implant as potentially eligible for inclusion. Based on this, 100% (42) were eligible, and 5% (two of 42) were excluded because they did not provide informed consent, leaving 95% (40 of 42) for analysis. Between 2015 and 2018, we treated 79 individuals with similar indications with osseointegration implant surgery, now also treating individuals with dysvascular amputations. We used an adapted surgical technique resulting in a shallower stoma combined with a titanium implant. Using the same eligibility criteria as for the first group, 51% (40 of 79) were eligible; 49% (39 of 79) were excluded because they were treated with transtibial amputation, a patient-specific implant, or single-stage surgery and 1% (one of 79) were lost before the 2-year follow-up interval, leaving 49% (39 of 79) for analysis. The period of 2013 to 2015 was a transitional period and was excluded from analysis in this study to keep groups reasonably comparable and to compare a historical approach with the present approach. Hence, we presented a comparative study of two study groups (defined by surgical technique and implant design) with standardized 2-year follow-up. The risk factors for adverse events were similar between groups, although individuals treated with the shallow stoma surgical technique and titanium implant potentially possessed an increased risk because of the inclusion of individuals with dysvascular amputation and the discontinuation of prolonged postoperative antibiotic prophylaxis. Outcomes studied were soft tissue infections and stoma-related complications (hypergranulation or keloid formation as well as stoma redundant tissue) and bone or implant infection, aseptic loosening, implant stem breakage, periprosthetic fracture, and death.

RESULTS

Patients treated with the shallow stoma surgical technique and titanium implant experienced fewer soft tissue infections (13 versus 76 events, absolute risk 0.17 [95% CI 0.09 to 0.30] versus 0.93 [95% CI 0.60 to 1.45]; p < 0.01), which were treated with less invasive measures, and fewer stoma redundant tissue events (0 versus five events, absolute risk 0 versus 0.06 [95% CI 0.03 to 0.14]) than patients treated with the conventional stoma surgical technique and CoCrMo implant. This was contrasted by an increased incidence of surgical site infections occurring between surgical stages 1 and 2, when no stoma was yet created, after the implementation of treatment changes (conventional surgery and CoCrMo implant versus shallow stoma surgery and titanium implant: one versus 11 events, absolute risk 0.01 [95% CI 0.00 to 0.08] versus 0.14 [95% CI 0.08 to 0.25]; p = 0.02). Patients treated with the shallow stoma surgical technique and titanium implant did not experience serious complications, although bone infections occurred (six events in 8% [three of 40] of patients) in the conventional surgery and CoCrMo implant group, all of which were successfully treated with implant retention.

CONCLUSION

Adaptations to surgical technique and newer implant designs, as well as learning curve and experience, have resulted in a reduced incidence and severity of soft tissue infections and stoma redundant tissue, contrasted by an increase in surgical site infections before stoma creation. Serious complications such as deep implant infection were infrequent in this 2-year follow-up period. We believe the benefits of these treatment modifications outweigh the disadvantages and currently advise surgeons to create a shallower stoma with a stable soft tissue envelope, combined with a titanium implant.

LEVEL OF EVIDENCE

Level III, therapeutic study.