Evaluation of True Ankle Motion Following Total Ankle Replacement Utilizing XROMM technology

Category: Ankle Arthritis Introduction/Purpose: Total ankle replacement (TAR) is common tool used by the foot and ankle specialist to treat end stage ankle arthritis. Current data about ankle motion following TAR is derived from gait analysis utilizing external markers. Utilizing Xray Reconstruction of Moving Morphology (XROMM), which combines 3-D mapping technology with biplanar fluoroscopy in vivo to visualize true skeletal motion, we can evaluate true motion of TAR implants. Current TAR replacement systems are either mobile bearing or fixed bearing. We hypothesized that subjects implanted with a fixed bearing prosthesis would exhibit less tibiotalar rotation and translation than subjects implanted with a mobile bearing prosthesis. Methods: Six subjects with total ankle replacement at least one-year post implantation gave informed consent before participating (IRB #H16496). Three subjects with a mobile bearing prosthesis with an average age 63.3+-11.1 yrs were compared to three matched subjects with a fixed bearing prosthesis with an average age of 64.7+-1.5 yrs. Utilizing 3D slicer software, lower body CT scans for each subject were evaluated to create 3D models of the foot and ankle bones and implant components. All subjects walked for several trials at a self-selected pace along a walkway while their foot and ankle motions were captured by a high-speed biplanar fluoroscopic x-ray motion analysis (XMA) system. The 3D models were combined with the x-ray images within a 3D animation platform and rotoscoped to resolve accurate kinematic motions at the tibiotalar joint during stance phase of gait. We examined for differences between the two groups using a two-sample t-test (p<0.05). Results: Subjects with a mobile-bearing prosthesis demonstrated mean ROM’s of 7.4+-1.1°, 5.3+-2.3° and 7.1+-4.3° for dorsiflexion/plantarflexion, inversion/eversion, and internal/external rotation, respectively. Subjects with a fixed bearing ankle prosthesis did not exhibit significantly different mean ROM’s for dorsiflexion/plantarflexion (9.1+-4.0°, p=0.35), inversion/eversion (4.4+-2.1°, p=0.42), and internal/external rotation (9.0+-3.4°, p=0.35), respectively. Subjects with a fixed bearing prosthesis displayed significantly more translation along the anteroposterior (3.6+-1.2mm, p<0.01) and mediolateral (2.2+-0.7mm, p<0.01) axes compared to the mobile bearing prosthesis (1.8+-1.2mm and 1.3+-0.8mm, respectively). Conclusion: Our preliminary results indicate that mobile and fixed bearing prosthesis provides similar angular motion at the tibiotalar joint, however, the fixed bearing prosthesis exhibits greater translational motion during walking. Further, there is the same amount of internal and external translation with both component designs. The implications of this work on success or failure of current implant designs is beyond the scope of this study but this work will provide the basis for future studies to help determine optimal future total ankle replacement designs.

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Prospective Randomized Trial Comparing Mobile-bearing and Fixed-bearing Total Ankle Replacement

Foot & Ankle Orthopaedics ◽

10.1177/2473011418s00093 ◽

2018 ◽

Vol 3 (3) ◽

pp. 2473011418S0009

Author(s):

James Nunley ◽

Samuel Adams ◽

James DeOrio ◽

Mark Easley

Keyword(s):

Clinical Outcomes ◽

Mobile Bearing ◽

Cyst Formation ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Ankle Arthritis ◽

Ankle Replacement ◽

Significant Difference ◽

End Stage

Category: Ankle Arthritis Introduction/Purpose: Outcomes of total ankle replacement for the treatment of end-stage ankle arthritis continue to improve. Debate continues whether a mobile-bearing total ankle replacement (MB-TAR) or a fixed-bearing total ankle replacement (FB-TAR) is superior, with successful outcomes reported longterm for MB-TAR and at intermediate-to-longterm follow-up for newer generation FB-TAR. Although comparisons between the two total ankle designs have been reported, to our knowledge, no investigation has compared the two designs with a high level of evidence. This prospective, randomized controlled trial conducted at a single institution compares patient satisfaction, functional outcomes and radiographic results of the mobile-bearing STAR and the fixed-bearing Salto-Talaris in the treatment of end-stage ankle arthritis. Methods: This investigation was approved by our institution’s IRB committee. Between November 2011 and November 2014, adult patients with end-stage ankle osteoarthritis failing nonoperative treatment were introduced to the study. With informed consent, 100 patients (31 male and 69 female, average age 65, range 35 to 85) were enrolled; demographic comparison between the two cohorts was similar. Exclusion criteria included inflammatory arthropathy, neuropathy, weight exceeding 250 pounds, radiographic coronal plane deformity greater than 15 degrees or extensive talar dome wear pattern (“flat top talus”). Prospective patient-reported outcomes, physical exam and standardized weightbearing ankle radiographs were obtained preoperatively, at 6 and 12 months postoperatively, and then at yearly intervals. Data collection included visual analog pain score (VAS), short form 36 (SF-36), foot and ankle disability index (FADI), short musculoskeletal functional assessment (SMFA) and AOFAS ankle-hindfoot score. Surgeries were performed by non-design team orthopaedic foot and ankle specialists with total ankle replacement expertise. Statistically analysis was performed by a qualified statistician. Results: At average follow-up of 4.5 years (range 2-6 years) complete clinical data and radiographs were available for 84 patients; 7 had incomplete data, one had died, 4 were withdrawn after enrolling but prior to surgery and 4 were lost to follow-up. In all outcome measures, the entire cohort demonstrated statistically significant improvements from preoperative evaluation to most recent follow-up. There was no statistically significant difference in improvement in clinical outcomes between the two groups. Radiographically, tibial lucency/cyst formation was 26.8% and 20.9% for MB-TAR and FB-TAR, respectively. Tibial settling/subsidence occurred in 7.3% of MB-TAR. Talar lucency/cyst formation occurred in 24.3% and 2.0% of MB-TAR and FB-TAR, respectively. Talar subsidence was observed in 21.9% and 2.0% of MB-TAR and FB-TAR, respectively. Re-operations were performed in 8 MB-TAR and 3 FB-TAR, with the majority of procedures being to relieve impingement or treat cysts and not to revise or remove metal implants. Conclusion: For the first time, with a high level of evidence, our study confirms that patient reported and clinical outcomes are favorable for both designs and that there is no significant difference in clinical improvement between the two implants. The incidence of lucency/cyst formation was similar for MB-TAR and FB-TAR for the tibial component, but the MB-TAR had greater talar lucency/cyst formation and tibial and talar subsidence. As has been suggested in previous studies, clinical outcomes do not correlate with radiographic findings. Re-operations were more common for MB-TAR and in the majority of cases were to relieve impingement or treat cysts rather than revise or remove metal implants.

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Hindfoot Alignment after Total Ankle Replacement

Foot & Ankle Orthopaedics ◽

10.1177/2473011420s00007 ◽

2020 ◽

Vol 5 (2) ◽

pp. 2473011420S0000

Author(s):

Christopher E. Gross ◽

Federico Guiseppe Usuelli ◽

Christian Indino

Keyword(s):

Sagittal Alignment ◽

Mobile Bearing ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Ankle Arthritis ◽

Hindfoot Alignment ◽

Time Points ◽

Ankle Replacement ◽

Temporal Course ◽

Over Time

Category: Ankle Arthritis; Ankle Introduction/Purpose: End-stage ankle arthritis can involve misalignment of the ankle in both the coronal and sagittal planes as up to reported 33% to 44% of patients who present for total ankle replacement have greater than 10° of coronal plane deformity. Improvements in both the design and surgical technique for total ankle replacements (TAR) have allowed surgeons to tackle the most challenging of multiplanar ankle deformities. Normalization of the sagittal and coronal alignment is key in improving survivorship and functional outcomes in TAR. In the present study, we analyzed how both the ankle and hindfoot alignment for both a fixed-bearing and mobile bearing TAR system changes over time. Specifically, we measured coronal and sagittal alignment of both the ankle and hindfoot complex. We hypothesize that both significant differences would be seen between all time points and pre-operative radiographs, and that these differences would not change over time. Methods: A retrospective study performed by a single orthopaedic surgeon was performed on two independent groups of patients undergoing two different systems for total ankle replacement: Zimmer TAR (lateral-approach, fixed-bearing, n=89) and Hintegra (anterior approach, mobile-bearing, n=81). We noted specific demographic data and radiographic data were measured including: Hindfoot alignment view angle (HAV), Hindfoot alignment distance (HAVD), tibiotalar ratio, α angle and β angle. These were measured pre-operatively, and 6 months, 12 months, and 24 months post-operatively. Within-group comparisons were performed using one-way repeated-measures ANOVA (1-w rANOVA), analyzing temporal course of clinical data (comparisons between different time points, e.g. T0vsT6vsT12vsT24) within the Hintegra and Zimmer groups. To compare the time course of clinical measures between the two groups, 2-w rANOVAs were performed for SA, SD, TT ratio, α and β angle. Specifically, time*group interaction was tested. Results: At the ankle joint itself, as measured by the α and β angles (p>.05), the position of the components remains relatively similar in both the fixed and mobile bearing TAR over the course of 24 months. The sagittal alignment, as measured by the TT ratio, demonstrated a posterior shifting of the talus in the mobile bearing group (p=.036). Though the fixed and mobile- bearing TAR had both significant hindfoot alignment improvement between the pre-op radiographs and twenty-four months, over time, the fixed-bearing ankle had a significant increase in both the HAV and HAVD (p<.001), suggesting a dynamism of the hindfoot in the fixed-bearing ankle. Conclusion: Correcting coronal and sagittal alignment is important for the long-term survivorship of a TAR. The fixed and mobile-bearing implants had maintained coronal and sagittal alignment in the short term, the temporal course of the fixed-bearing ankle showed an increased in the valgus positioning of the hindfoot.

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Hindfoot Alignment after Total Ankle Replacement

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00189 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0018

Author(s):

Christopher Gross ◽

Luigi Manzi ◽

Cristian Indino ◽

Fausto Romano ◽

Camilla Maccario ◽

...

Keyword(s):

Sagittal Alignment ◽

Mobile Bearing ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Ankle Arthritis ◽

Hindfoot Alignment ◽

Time Points ◽

Ankle Replacement ◽

Temporal Course ◽

Over Time

Category: Ankle, Ankle Arthritis Introduction/Purpose: End-stage ankle arthritis can involve misalignment of the ankle in both the coronal and sagittal planes as up to reported 33% to 44% of patients who present for total ankle replacement have greater than 10° of coronal plane deformity. Normalization of the sagittal and coronal alignment is key in improving survivorship and functional outcomes in TAR. In the present study, we analyzed how both the ankle and hindfoot alignment for both a fixed-bearing and mobile bearing TAR system changes over time. Specifically, we measured coronal and sagittal alignment of both the ankle and hindfoot complex. We hypothesize that both significant differences would be seen between all time points and pre-operative radiographs, and that these differences would not change over time. Methods: A retrospective study performed by a single orthopaedic surgeon was performed on two independent groups of patients undergoing two different systems for total ankle replacement: Zimmer TAR (lateral-approach, fixed-bearing, n=89) and Hintegra (anterior approach, mobile-bearing, n=81). We noted specific demographic data and radiographic data were measured including: Hindfoot alignment view angle (HAV), Hindfoot alignment distance (HAVD), tibiotalar ratio, a angle and ß angle. These were measured pre-operatively, and 6 months, 12 months, and 24 months post-operatively. Within-group comparisons were performed using one-way repeated-measures ANOVA (1-w rANOVA), analyzing temporal course of clinical data (comparisons between different time points, e.g. T0vsT6vsT12vsT24) within the Hintegra and Zimmer groups. To compare the time course of clinical measures between the two groups, 2-w rANOVAs were performed for SA, SD, TT ratio, a and ß angle. Specifically, time*group interaction was tested. Results: At the ankle joint itself, as measured by the a and ß angles (p>.05), the position of the components remains relatively similar in both the fixed and mobile bearing TAR over the course of 24 months. The sagittal alignment, as measured by the TT ratio, demonstrated a posterior shifting of the talus in the mobile bearing group (p=.036). Though the fixed and mobile-bearing TARhad both significant hindfoot alignment improvement between the pre-op radiographs and twenty-four months, over time, the fixed-bearing ankle had a significant increase in both the HAV and HAVD (p<.001), suggesting a dynamism of the hindfoot in the fixed-bearing ankle. Conclusion: Correcting coronal and sagittal alignment is important for the long-term survivorship of a TAR. The fixed and mobile-bearing implants had maintained coronal and sagittal alignment in the short term, the temporal course of the fixed-bearing ankle showed an increased in the valgus positioning of the hindfoot. The mobile-bearing implant maintained its hindfoot alignment over the course of the study. More studies are needed to explore the clinical implications of this new data.

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Ankle and Hindfoot Kinematics of a Next Generation Total Ankle Replacement During Simulated Gait

Foot & Ankle Orthopaedics ◽

10.1177/2473011418s00119 ◽

2018 ◽

Vol 3 (3) ◽

pp. 2473011418S0011

Author(s):

Daniel Sturnick ◽

Guilherme Saito ◽

Scott Ellis ◽

Constantine Demetracopoulos

Keyword(s):

Joint Kinematics ◽

Total Ankle Replacement ◽

Foot And Ankle ◽

Next Generation ◽

Fixed Bearing ◽

Ankle Arthritis ◽

Gait Simulation ◽

Ankle Replacement ◽

Significant Difference

Category: Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) has developed as a viable treatment option for end-stage ankle arthritis. The primary benefit proposed with TAA is that allows for maintained motion of the ankle and hindfoot joint compared to the alternative option of an ankle arthrodesis. Consequently, recent TAA systems have focused on designs that advance kinematic function. Cadaveric gait simulation is a valuable tool for investigating the direct effects of surgical procedures and devices on foot and ankle biomechanics. The objective of this study was to assess whether a next generation TAA system permits normal ankle and hindfoot kinematics using cadaveric gait simulation. Methods: Ten mid-tibia cadaveric specimens were secured to a static mounting fixture relative a six-degree of freedom robotic platform to simulate gait in native-intact and TAA conditions. A force plate was moved relative to the stationary specimen through an inverse tibial kinematic path calculated from in vivo data while extrinsic tendons were actuated using physiologic loads (Figure 1A). Ankle and hindfoot kinematics were measured from reflective markers attached to bones via surgical pins. TAA was performed using a next generation, fixed bearing total ankle system by a fellowship trained foot and ankle surgeon using manufacturer described protocol (Cadence Total Ankle, Integra LifeSciences). Ankle and hindfoot joint kinematics were directly measured using the same kinematic inputs and muscle force as the intact condition. Non-parametric, bias-corrected bootstrapping was used to calculate 95% confidence intervals to compare motion between intact and total ankle replacement conditions. Results: Analyses revealed that no significant difference in average ankle or hindfoot joint kinematics were found between intact and TAA conditions (Figure 1B). This result was consistent in each the ankle, subtalar, and talonavicular joints, and in each plane of motion. Conclusion: This study found that normal kinematics were permitted on average by a next generation, fixed bearing TAA. This finding may indicate that improved functional outcomes following could be expected. However, increased variability and some characteristic differences in the paths of motion throughout stance were observed qualitatively. This report represents an initial analysis of preliminary data, future work will include further analyses and investigation on the influence of factors such as component position and alignment on outcomes. That said, the findings of this study are encouraging and may represent improved kinematic performance in new TAA designs.

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Revision Rates After Total Ankle Replacement: A Comparison of Clinical Studies and Arthroplasty Registers

Foot & Ankle International ◽

10.1177/10711007211053862 ◽

2021 ◽

pp. 107110072110538

Author(s):

Georg Hauer ◽

Reinhard Hofer ◽

Markus Kessler ◽

Jan Lewis ◽

Lukas Leitner ◽

...

Keyword(s):

Clinical Studies ◽

Revision Rate ◽

Mobile Bearing ◽

Total Ankle Replacement ◽

Second Step ◽

Fixed Bearing ◽

Inclusion Criteria ◽

Level Of Evidence ◽

Ankle Replacement ◽

Significant Difference

Background: The aim of this study was to assess the outcome of total ankle replacement (TAR) regarding revision rates by comparing clinical studies of the last decade to data displayed in arthroplasty registers. The secondary aim was to evaluate whether dependent clinical studies show a superior outcome to independent publications. Additionally, revision rates of mobile bearing implants (MB-TARs) were compared to those of fixed bearing implants (FB-TARs). Methods: Clinical studies on TARs between 2010 and 2020 were systematically reviewed, with the endpoint being a revision for any reason. The parameter “revision rate per 100 observed component years (CYs)” was calculated for each publication. The pooled revision rate for clinical studies was compared to the data reported in arthroplasty registers. In a second step, revision rates were subdivided and analyzed for independent and dependent publications and for FB-TARs and MB-TARs. Results: A total of 43 publications met the inclusion criteria comprising 5806 TARs. A revision rate of 1.8 per 100 observed CYs was calculated, corresponding to a 7-year revision rate of 12.6%. The 3 arthroplasty registers included showed revision rates ranging from 8.2% to 12.3% after 7 years. No significant difference between dependent and independent publications nor between FB-TARs and MB-TARs was detected. Conclusion: Revision rates of clinical studies and arthroplasty registers are comparable. Surgeons can compare their own revision rates with those from this study. Dependent studies do not seem to be biased, and no superiority for one bearing type can be described. Level of Evidence: Level III, systematic review of level III studies

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Prospective Randomized Trial Comparing Mobile-Bearing and Fixed-Bearing Total Ankle Replacement

Foot & Ankle International ◽

10.1177/1071100719879680 ◽

2019 ◽

Vol 40 (11) ◽

pp. 1239-1248 ◽

Cited By ~ 4

Author(s):

James A. Nunley ◽

Samuel B. Adams ◽

Mark E. Easley ◽

James K. DeOrio

Keyword(s):

Mobile Bearing ◽

Cyst Formation ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Level Of Evidence ◽

Ankle Replacement ◽

Significant Difference ◽

Patient Reported ◽

End Stage

Background: Outcomes of total ankle replacement for the treatment of end-stage ankle arthritis continue to improve. Debate continues whether a mobile-bearing total ankle replacement (MB-TAR) or a fixed-bearing total ankle replacement (FB-TAR) is superior, with successful outcomes reported long term for MB-TAR and at intermediate- to long-term follow-up for newer generation FB-TAR. Although comparisons between the 2 total ankle designs have been reported, to our knowledge, no investigation has compared the 2 designs with a high level of evidence. This prospective, randomized controlled trial conducted at a single institution compares patient satisfaction, functional outcomes, and radiographic results of the mobile-bearing STAR and the fixed-bearing Salto-Talaris in the treatment of end-stage ankle arthritis. Methods: Between November 2011 and November 2014, adult patients with end-stage ankle osteoarthritis failing nonoperative treatment were introduced to the study. With informed consent, 100 patients (31 male and 69 female, average age 65 years, range 35-85 years) were enrolled; a demographic comparison between the 2 cohorts was similar. Exclusion criteria included inflammatory arthropathy, neuropathy, weight exceeding 250 pounds, radiographic coronal plane deformity greater than 15 degrees, or extensive talar dome wear pattern (“flat-top talus”). Prospective patient-reported outcomes, physical examination, and standardized weightbearing ankle radiographs were obtained preoperatively, at 6 and 12 months postoperatively, and then at yearly intervals. Data collection included visual analog pain score, Short Form 36, Foot and Ankle Disability Index, Short Musculoskeletal Functional Assessment, and American Orthopaedic Foot & Ankle Society ankle-hindfoot score. Surgeries were performed by a nondesign team of orthopedic foot and ankle specialists with total ankle replacement expertise. Statistical analysis was performed by a qualified statistician. At average follow-up of 4.5 years (range, 2-6 years) complete clinical data and radiographs were available for 84 patients; 7 had incomplete data, 1 had died, 4 were withdrawn after enrolling but prior to surgery, and 4 were lost to follow-up. Results: In all outcome measures, the entire cohort demonstrated statistically significant improvements from preoperative evaluation to most recent follow-up with no statistically significant difference between the 2 groups. Radiographically, tibial lucency/cyst formation was 26.8% and 20.9% for MB-TAR and FB-TAR, respectively. Tibial settling/subsidence occurred in 7.3% of MB-TAR. Talar lucency/cyst formation occurred in 24.3% and 2.0% of MB-TAR and FB-TAR, respectively. Talar subsidence was observed in 21.9% and 2.0% of MB-TAR and FH-TAR, respectively. Reoperations were performed in 8 MB-TARs and 3 FH-TARs, with the majority of procedures being to relieve impingement or treat cysts and not to revise or remove metal implants. Conclusion: With a high level of evidence, our study found that patient-reported and clinical outcomes were favorable for both designs and that there was no significant difference in clinical improvement between the 2 implants. The incidence of lucency/cyst formation was similar for MB-TAR and FH-TAR for the tibial component, but the MB-TAR had greater talar lucency/cyst formation and tibial and talar subsidence. As has been suggested in previous studies, clinical outcomes do not necessarily correlate with radiographic findings. Reoperations were more common for MB-TAR and, in most cases, were to relieve impingement or treat cysts rather than revise or remove metal implants. Level of Evidence: Level I, prospective randomized study.

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Transfibular Total Ankle Replacement Outcome at 2 Years Follow Up

Foot & Ankle Orthopaedics ◽

10.1177/2473011417s000272 ◽

2017 ◽

Vol 2 (3) ◽

pp. 2473011417S0002

Author(s):

Camilla Maccario ◽

Cristian Indino ◽

Luigi Manzi ◽

Federico Giuseppe Usuelli ◽

Claudia Di Silvestri

Keyword(s):

Normal Values ◽

Short Form ◽

Articular Surface ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Trabecular Metal ◽

Ankle Arthritis ◽

Ankle Osteoarthritis ◽

Ankle Replacement

Category: Ankle, Ankle Arthritis Introduction/Purpose: Primary ankle osteoarthritis is very uncomon, in fact 70-78% of the case ankle arthritis has a post- traumatic cause. Ankle arthrodesis (AA), has been considered a reliable procedure for resolution of ankle osteoarthritis. Recent modifications in Total ankle replacement (TAR) designs have challenged the perception that AA is the treatment of choice for end-stage ankle arthritis. Trabecular Metal Total Ankle system is a fixed-bearing prosthesis. The new design is flanked by use of new materials. The tibial articular surface is constructed of highly crosslinked UHMWPE and Trabecular Metal lining the talar and the tibial base component. The purpose of this retrospective study was to show the preliminary result in 31 patients underwent to ankle replacement using Zimmer Trabecular Metal Total Ankle system. Methods: We retrospectively assessed prospectively collected data on the initial cohort of 31 patients undergoing TAR with this implant. Clinical evaluation was determined pre and postoperatively for a minimum of 24 months after surgery. Pain was rated using the visual analogue scale (VAS). Functional results were assessed as well as ankle range of motion (ROM). Clinical outcomes used where the Short Form SF-12 Quality of Life score, the American Foot and Ankle Society (AOFAS). The imaging follow-up included ankle radiographs done at 6, 12 and 24 months. Radiological parameters were angles??(normal values 90 +- 2),?? (normal value 85 +- 2),??? normal values 20 +- 2) and TTratio? normal values: 27% to 42%). Results: The study included 31 ankles of TM Ankle Replacement in 31 consecutive patients over a period of 2 years (2013–2015). Out of 31 patients, 13 were females and 18 were males (average age 49.4 years, range, 30–75 years). All procedures were performed by a single surgeon. The ROM plantarflexion and dorsiflexion improved significantly (p <0.001) at the last follow up. The mean VAS pain score decreased significantly from 7.42 points (range 4 – 10 points) preoperatively to 1.42 points (range, 0 - 3 points) at the time of the latest follow-up (p <0.001). AOFAS and SF-12 scores both improved from postoperatively to the last follow up. (Table 1). We noted stable implants based on our radiographic parameters, with no corrections loosening. (Table 2) Conclusion: Our study evaluated the new fixed bearing Zimmer TM total ankle replacement approved by the US FDA in 2012 and is the first studies to evaluate the clinical and radiographic outcomes of this prosthesis. Of 31 ankles treated with a new transfibular arthroplasty system, only two asymptomatic fibular delayed union were registered. No implant failure was noted at 24 months postoperatively. Four ankles underwent secondary surgery for symptomatic fibular hardware with good outcome. The findings suggest that this total ankle system is safe and effective at short-term follow-up.

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The Effect of Exchanging a Mobile-Bearing into a Fixed-Bearing Total Ankle Replacement System in Patients with Coronal Plane Instability

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00368 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0036

Author(s):

Roxa Ruiz ◽

Christine Schweizer ◽

Nicola Krähenbühl ◽

Beat Hintermann

Keyword(s):

Tibial Component ◽

Mobile Bearing ◽

Total Ankle Replacement ◽

Coronal Plane ◽

Consecutive Series ◽

Cement Spacer ◽

Tibial Osteotomy ◽

Fixed Bearing ◽

Radiographic Assessment ◽

Ankle Replacement

Category: Ankle, Ankle Arthritis Introduction/Purpose: The interface between the polyethylene (PE) inlay and the tibial component in mobile-bearing total ankle replacement (TAR) systems may allow the talus to seek its position according to the individual anatomy. However, chronic overload and/or incompetence of soft tissue may allow medial and/ or lateral translation of the talar component over time. This typically results in medial and/ or lateral gutter pain as well as pain along the syndesmosis. The purpose of this study was to assess the effect of tibial component exchange and conversion from a mobile-bearing into a fixed-bearing TAR system in patients with coronal plane instabilities TAR. Methods: A consecutive series of 30 ankles (29 patients; age 65.6 [48.9 – 86.1]; male, 23; female, 7) with coronal plane instabilities underwent revision TAR with exchange of a mobile-bearing (Hintermann Series, H3) into a fixed-bearing (Hintermann Series, H2) TAR system. Patients presented with a medial (n = 12) or lateral (n = 9) translation of the talar component, or a varus (n = 4) or valgus (n = 5) instability with subsequent tilt of the talar component. After removing the tibial component and PE inlay, a tibial osteotomy was performed and 1 to 2 mm of the distal tibia removed. A tibial component of the H2 total ankle system was inserted. While holding the foot in neutral position, the PE inlay was locked to the tibial component in the appropriate position. Functional outcome and pain were recorded to evaluate clinical outcome, and standard radiographs under fluoroscopy were taken for radiographic assessment. Results: All but one of the remaining 28 patient showed significant improvement of pain (P<0.05). Preoperative gutter pain disappeared completely in 20 ankles (71.4%), and partially in 8 ankles (18.6%). The AOFAS Hindfoot Score improved from 54.3 (range, 21 to 90) preoperatively to 74.0 (range, 48 to 92) at latest follow-up (P<0.05). Radiographic assessment showed firm osteointegration in all patients with the talar component centralized in the ankle mortise, and a free medial and lateral gutter without tilt of talar component (Figure 1). One patient with bilateral revision TAR was affected by a bilateral deep infection of both ankles 9 months after surgery subsequent to a severe pneumonia. Both ankles were removed and replaced by a cement spacer. Conclusion: Converting a mobile-bearing into a fixed-bearing TAR system has shown to be effective in the treatment of patients with coronal plane instabilities following TAR. Allowing the PE inlay to adapt its position according to the talar component before definitive fixation to the tibial component of the H2 series, saved having to replace the talar component. Future long-term studies however are needed to identify significant benefits of this novel total ankle concept in primary and revision TAR.

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Impact of Articulation Geometry on Contact Mechanics in Total Ankle Replacement Design

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53107 ◽

2011 ◽

Author(s):

Mehul A. Dharia ◽

Jeff E. Bischoff ◽

Duane Gillard ◽

Fred Wentorf ◽

Matt Mroczkowski

Keyword(s):

Lower Risk ◽

First Generation ◽

Polyethylene Wear ◽

Mobile Bearing ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Ankle Replacement ◽

Improved Outcomes ◽

Articulating Surface ◽

Replacement Design

Total ankle replacement designs have evolved since their introduction in the mid 1970s. While the first-generation total ankle replacement (TAR) designs had unacceptably high failure rates, recent designs have demonstrated improved outcomes [1]. Two philosophies are commonly used in TAR design: mobile-bearing and fixed-bearing. Unlike mobile-bearing designs which have two articulating surfaces, fixed-bearing designs have only one articulating surface. While fixed-bearing designs have lower risk of dislocation than mobile-bearing designs, the single articulation feature can produce higher contact stress on the articulating surface, increasing the potential for polyethylene wear [1, 2].

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The Ankle-Hindfoot Kinematics of Current Generation Total Ankle Replacement: A Cadaveric Gait Simulation

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00203 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0020

Author(s):

Thos Harnroongroj ◽

Daniel Sturnick ◽

Scott J. Ellis ◽

Constantine Demetracopoulos ◽

Jonathan Deland

Keyword(s):

Joint Kinematics ◽

Total Ankle Replacement ◽

Patient Specific ◽

Fixed Bearing ◽

Ankle Arthritis ◽

Current Generation ◽

Gait Simulation ◽

Ankle Replacement ◽

Wright Medical Technology ◽

Significant Difference

Category: Ankle Arthritis Introduction/Purpose: Total ankle replacement (TAR) has developed as a standard treatment option for end-stage ankle arthritis with the primary benefit of pain relief and ankle-hindfoot motion preservation. The current generation of TARs features limited bone resection and improved initial fixation of components to restore physiologic constraint and the anatomic articulation of the ankle. However, the ankle-hindfoot kinematics of current TAR designs compared to the baseline native ankle have not yet been extensively studied. Cadaveric gait simulation is a valuable tool for investigating direct effects of surgical procedures on foot and ankle biomechanics. The objective of this study was to assess whether this current generation TAR system could provide normal ankle-hindfoot kinematics as the baseline native ankle using cadaveric gait simulation. Methods: Eleven mid-tibia cadaveric specimens were secured to a static mounting fixture with a six-degree of freedom robotic platform to simulate gait in native-intact and TAR conditions. A force plate was moved relative to the stationary specimen through an inverse tibial kinematic path calculated from in vivo data while extrinsic tendons were actuated using physiologic loads (Figure 1A). Ankle-hindfoot kinematics were measured from reflective markers attached to bones via surgical pins. TAR was performed using a current generation, fixed-bearing system by a fellowship-trained foot-ankle surgeon using the manufacturer described protocol (PROPHECY Patient-specific instrumentation, Infinity, Wright Medical Technology). Ankle-hindfoot joint kinematics were measured using the same tibial kinematic inputs and muscle forces as the intact condition. Non-parametric, bias-corrected bootstrapping was used to calculate 95% confidence intervals to compare motion between intact and total ankle replacement. Results: Analyses demonstrated no significant difference in average ankle-hindfoot joint kinematics between the intact and TAR conditions (Figure 1B). The result was consistent for the ankle, subtalar, and talonavicular joints, in each plane of motion. Conclusion: These findings demonstrate that the current generation of fixed-bearing TAR can recreate normal ankle-hindfoot kinematics patterns seen in normal ankles. Restoring ankle kinematics can be a significant factor in slowing down the progression of adjacent joint arthritis in the foot. However, it is still inconclusive whether ankle-hindfoot kinematics can be restored in patients with long standing ankle arthritis, and this should be addressed in future studies.

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