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

2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0009
Author(s):  
James Nunley ◽  
Samuel Adams ◽  
James DeOrio ◽  
Mark Easley

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complete clinical data and radiographs were available for 84 patients; 7 had incomplete data, one had died, 4 were withdrawn after enrolling but prior to surgery and 4 were lost to follow-up.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.

2019 ◽  
Vol 40 (11) ◽  
pp. 1239-1248 ◽  
Author(s):  
James A. Nunley ◽  
Samuel B. Adams ◽  
Mark E. Easley ◽  
James K. DeOrio

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.


2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0002
Author(s):  
Camilla Maccario ◽  
Ettore Vulcano ◽  
Cristian Indino ◽  
Luigi Manzi ◽  
Federico Giuseppe Usuelli

Category: Ankle, Ankle Arthritis Introduction/Purpose: Total ankle replacement (TAR) is becoming increasingly popular amongst patients with end-stage ankle arthritis. This is in part related to the advances in design, technology, and technique that have improved TAR longevity. The ideal candidate for a TAR is not fully clear. For a long time patients over age 50 years, body mass index (BMI) under 30 kg/m2, and with low functional demands represented selection criteria for many patients. However, these criteria were based off a very limited number of scientific studies on older TAR designs. The aim of this study is to investigate clinical and radiographic outcome in patients of 50 years or less versus patients over 50 years undergoing a Hintegra® total ankle replacement (Integra, Plainsboro, NJ). Methods: This study includes 70 consecutive patients who underwent primary TAR from May 2011 to April 2014. The cohort was divided into 2 groups: the young group (YG) with age less than or equal to 50 years, and the older group (OG) with age above 50 years. Patients were assessed clinically and radiologically preoperatively and at 6, 12 and 24 months postoperatively. Results: A significant increase in the AOFAS and SF-12 and decrease in VAS scores was seen in both groups between preoperative and final followup (p < 0.001). There was a statistically significant difference between the YG and OG for the AOFAS score at final follow-up. The YG had significantly greater improvement compared to the OG (p = 0.046). In addition radiographic results showed no statistically significant difference in the coronal and sagittal alignment between the 2 groups. The mean postoperative angles in either study group demonstrated significant improvements compared to the preoperative alignment. Conclusion: This study demonstrates that total ankle arthroplasty is an effective short-term treatment for young, active patients with symptomatic end-stage ankle arthritis. Our findings are in disagreement with the widespread theory that ankle replacement is a more reliable treatment in the elderly


2021 ◽  
pp. 193864002098092
Author(s):  
Devon W. Consul ◽  
Anson Chu ◽  
Travis M. Langan ◽  
Christopher F. Hyer ◽  
Gregory Berlet

Total ankle replacement has become a viable alternative to ankle arthrodesis in the surgical management of advanced ankle arthritis. Total ankle replacement has generally been reserved for patients who are older and for those who will have a lower demand on the replacement. The purpose of the current study is to review patient outcomes, complications, and implant survival in patients younger than 55 years who underwent total ankle replacement at a single institution. A single-center chart and radiographic review was performed of consecutive patients who underwent total ankle replacement for treatment of end-stage ankle arthritis. All surgeries were performed by 1 of 5 fellowship-trained foot and ankle surgeons at a single institution. A total of 51 patients met inclusion criteria with a mean follow-up of 31.2 months (SD = 16.2). Implant survival was 94%, There were 7 major complications (13%) requiring an unplanned return to the operating room and 8 minor complications (15%) that resolved with conservative care. The results of this study show that total ankle replacement is a viable treatment option for patients younger than 55 years. Levels of Evidence: A retrospective case series


2021 ◽  
pp. 107110072110538
Author(s):  
Georg Hauer ◽  
Reinhard Hofer ◽  
Markus Kessler ◽  
Jan Lewis ◽  
Lukas Leitner ◽  
...  

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


2019 ◽  
Vol 4 (2) ◽  
pp. 2473011419S0000
Author(s):  
James Lachman ◽  
Michel Taylor ◽  
Elizabeth Cody ◽  
Daniel Scott ◽  
James A. Nunley ◽  
...  

Category: Ankle Arthritis Introduction/Purpose: The Scandinavian Total Ankle Replacement(STAR) system and Salto Talaris(ST) total ankle system are two of the more commonly studied total ankle implants. As the STAR is one of the oldest total ankle arthroplasty (TAA) implants still in use today, most studies focus on longevity and survivorship. Reported rates of cyst formation for these two prosthesis in most series vary from 11-22% but no large study has focused on surgical management of these cysts or included patient reported outcomes after surgery. In this series, we aimed to investigate rates of cyst formation between mobile(MB) and fixed-bearing(FB) TAA and examine clinical and patient reported outcomes of bone grafting or cementing of large cysts surrounding the STAR and ST implants. Methods: A prospectively collected database at a high volume total ankle replacement center was retrospectively reviewed to identify patients who underwent TAA with either the STAR or the ST total ankle system between 2007 and 2015. Cysts were identified and measured on standard weight bearing radiographs and confirmed on computed tomography(CT) when available. Visual analog scale (VAS) score, Short Form-36 (SF-36) physical and mental component scores, Short Musculoskeletal Function Assessment(SMFA), and AOFAS hindfoot scores were collected from all patients preoperatively and then at 6 months, 1 year and annually postoperatively. Patients with a minimum 2 years follow-up who underwent revision TAA secondary to catastrophic bone cysts or who were managed with either curettage and bone grafting or curettage and cementing of bone cysts surrounding the TAA prosthesis were included in the patient reported outcomes (PRO) analysis Results: Excluding 53 patients for inadequate follow-up, 232 patients (29% female, 71% male; follow-up 6.7 years) who underwent STAR-TAA and 147 patients (26.6% female, 73.5% male; follow-up 7 years) who underwent ST-TAA were identified. Cysts <20 mm diameter occurred more often in the MB TAAs, and more often in the tibia than talus (table). Cysts >10 mm were identified in 95/232 (41%) STAR and 24/147 (16%) ST ankles. In the STAR group, 24 patients underwent cyst bone grafting (13), cementing (6) or both (8) at a mean 4.8 years. In the ST group, 14 patients underwent cyst bone grafting (6), cementing (4), or both (4) at a mean of 2.7 years. PRO data improved significantly for both the STAR and ST group in all questionnaires (p<0.05 for all). Conclusion: Mobile-bearing total ankle arthroplasty in this cohort had a higher rate of cyst formation greater than 10 mm (95/232 patients, 41%) when compared to a fixed-bearing TAA (24/147, 16.3%). Only 24/95 (25%) of STAR patients and 14/24 (58%) of ST patients required surgical intervention for cyst management. Patient reported outcomes after cyst surgery improved significantly when compared to pre-cyst management surgery and did not differ between MB and FB cohorts (p=0.424). Successful surgical management of large cyst surrounding either mobile-bearing or fixed-bearing total ankle systems can be expected based on the results of this study. [Table: see text]


2020 ◽  
Vol 5 (4) ◽  
pp. 2473011420S0042
Author(s):  
Hatem Salem-Saqer ◽  
Martin Raglan ◽  
Sunil Dhar

Category: Ankle; Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) is increasingly used for treatment of end stage arthritis of the ankle; improvements continue to evolve in implant design and instrumentation. We present our experience of the Infinity Total Ankle Arthroplasty (Wright Medical), a fixed bearing 4th generation implant with improved instrumentation Methods: This is a retrospective review of prospectively collected data. From October 2016 to July 2019, we identified 92 (52M/40F) who had the infinity Total Ankle Replacement. This review is of 70 patients with a minimum of 1 year follow up (33M,37F). The mean age was 67.5 years (33-87); 32 right side and 38 left no bilaterals. The indication for surgery was end stage Osteoarthritis in 52, post traumatic arthritis 12, inflammatory arthritis 4, conversion of fusion to TAR 2. The preoperative deformity was graded according to the COFAS classification. All patients had follow up at 6 weeks, 3,6 and 12 months and then annually, with MOXFQ questionnaire and weight bearing radiographs. Results: TAA was performed with the use of fluoroscopy. 77% (54/70) had concomitant procedures as listed in Table.5% (4/70) had complications consisting of, 1 DVT, 1 intra operative medial malleolus fracture, 1 EHL tendon laceration and 1 wound break down. There were no deep or superficial infections. Improvement in clinical outcome and PROMS data was noted on follow up. The MOXFQ for Pain improved from 72 pre-op to 25 at 1year (p<0.001). The outcome for Walking improved from 83 pre-op to 30 at one year (p<0.001). Radiological alignment was maintained asymptomatic posterior heterotopic ossification was noted in 23(16%) patients, lucent lines under the tibial implant were noted in 4 ankles and 1 fibula erosion. 2 TAA (3%) needed to be revised due to malpositioning. Conclusion: Our results show significant improvement in patient outcomes, a short recovery time and marked improvement in mobility post operatively with a very low complication rate, we had no deep infection to date. Two implants were revised which we attribute to the learning curve at the start of practice. This implant is fluoroscopically navigated allowing precise implantation with dedicated instrumentation and we feel this attributed to the low complication rate and good results in our short-term study [Table: see text]


2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0002
Author(s):  
Camilla Maccario ◽  
Cristian Indino ◽  
Luigi Manzi ◽  
Federico Giuseppe Usuelli ◽  
Claudia Di Silvestri

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.


2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0032
Author(s):  
Andrea Pujol Nicolas ◽  
Jayasree Ramas Ramaskandhan ◽  
Triin Nurm ◽  
Malik Siddique

Category: Ankle, Ankle Arthritis Introduction/Purpose: Total ankle replacement as a valid treatment for end stage ankle arthritis, is gaining popularity and every year there is an increasing number of procedures. With revision rates as high as 21% at 5 years and 43% at 10 years there is a need for understanding and reporting the outcome of revision ankle replacement. Our aim was to study the patient reported outcomes following revision TAR with a minimum of 2 year follow up. Methods: All patients that underwent a revision total ankle replacement between 2012 and 2016 were included in the study. All patients received a post-operative questionnaire comprising of MOX-FQ score, EQ-5D (UK) and Foot and Ankle outcomes scores (FAOS) and patients satisfaction questionnaire with a minimum of 2 years follow up. Results: 32 patients had a revision total ankle replacement between 2012 and 2016. 2 patients were deceased therefore 30 patients were included in the study. 5 patients declined participation for completing questionnaires. We received 21 (66%) completed questionnaires. The mean MOX-FQ average domain score for pain was 58.8, walking/standing 65.8 and social function was 48.2. The mean FAOS scores were 50.7 for pain, 50.6 for symptoms, 54.9 for ADL and 28.2 for quality of life. The mean overall health score today for EQ-5D was 67.8/100. 45% of patients were satisfied with the pain relief and return to sports and recreation obtained following the operation, 48% were satisfied with the improved in daily activities. 52% were overall satisfied with the results from surgery. Conclusion: Revision total ankle replacement gives overall satisfactory results demonstrated from patients reported outcomes at a minimum of 2 years following surgery.


2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0013
Author(s):  
Kevin Wing ◽  
Jason Sutherland ◽  
Timothy Daniels ◽  
Peter Dryden ◽  
Murray Penner ◽  
...  

Category: Ankle Arthritis Introduction/Purpose: There is much interest in the surgical treatment of end-stage ankle arthritis. Our team has previously reported comparisons between ankle fusion and replacement outcomes for 321 ankles at 5.5 years from a prospective cohort. This research extends the observational period for another six years, ending in 2013. Our primary hypothesis is that patient-reported clinical outcomes for ankle fusion and replacements would be similar at last follow up. Methods: Patients in the Canadian Orthopaedic Foot and Ankle Society (COFAS) Prospective Ankle Reconstructive Database were treated with total ankle replacement (involving Agilty, Star, Mobilty, Hintegra, or Inbone) or fusion (open or arthroscopic). Patient characteristics collected included demographics, comorbidities, smoking status and body mass index. Patient-reported outcomes (PROs) completed by patients were the Ankle Osteoarthritis Scale (AOS) and Short Form-36 (SF-36). Pre-operative and most recent patient data, with at least four years follow-up, were analyzed. Sensitivity analyses excluded ankles that had undergone revision. A linear mixed-effects regression model compared scores between total ankle replacement and fusion groups, adjusting for patient characteristics, baseline data and surgeon. Results: The sample included 844 ankles (556 ankle replacements and 284 arthrodesis). The mean follow up period was 8.0 years (standard deviation 3.1 years), with minimum and maximum of 4 and 14 years, respectively. Patients treated with arthrodesis were younger, more likely to be diabetic and smokers, and somewhat less likely to have inflammatory arthritis. Overall, 19.4% of ankle fusion and 30.8% of ankle replacements underwent all-cause re-operation. The mean AOS total score improved from 58.6 points pre-operatively to 31.4 post-operatively (delta 27.2), and from 57.0 to 26.9 points (delta 30.1) in the ankle replacement group. Differences in the change in AOS and SF-36 scores between the arthrodesis and ankle replacement groups were minimal after adjustment for baseline characteristics and surgeon. Conclusion: Clinical outcomes of total ankle replacement and ankle arthrodesis were comparable in a diverse cohort of patients whose follow up period ranged between 4 and 14 years post-operatively.


2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0020
Author(s):  
Thos Harnroongroj ◽  
Daniel Sturnick ◽  
Scott J. Ellis ◽  
Constantine Demetracopoulos ◽  
Jonathan Deland

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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