TL 18052 - Sagittal tibiotalar alignment in fixed-bearing total ankle replacement

Introduction: Implant positioning is critical in total ankle replacement (TAR). However, the effect of sagittal tibiotalar alignment on functional outcomes in fixed-bearing TAR remains unclear. Furthermore, no studies comparing different fixed-bearing implants with respect to the anteroposterior position of the talar component have been performed to date. Methods: A retrospective analysis of 71 primary TARs in a single center was performed. Prostheses included were the INBONE II® (Wright Medical, Memphis, TN) and the Salto Talaris (Integra LifeSciences, Plainsboro, NJ). Radiographic measurements of the tibial-axis-to-talus ratio (T-T ratio) and the anteroposterior offset ratio (AP offset ratio) were performed preoperatively and postoperatively, respectively. Foot and Ankle Outcome Scores (FAOS) and SF-12 MCS and PCS scales were evaluated preoperatively and 2 years postoperatively. Results: Postoperative sagittal tibiotalar alignment was neutral in 39 ankles and anterior in 32 ankles. No significant differences were observed between groups with respect to clinical outcome scores. Patients with a Salto Talaris prosthesis had a greater AP offset ratio (0.12 ± 0.05) than patients with an INBONE II® implant (0.05 ± 0.04) (P < .01); however, this increased translation did not correlate with the outcome scores. Conclusion: At the 2-year follow-up, the INBONE II® TAA showed a more neutral sagittal alignment compared with the Salto Talaris prosthesis. However, no correlation between the postoperative AP offset ratio and functional outcome scores was observed with the use of the two fixed-bearing TAR. Further studies with longer follow-ups are needed to determine if the difference in sagittal alignment may have an effect on functional outcomes in the long-term.

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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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Sagittal Tibiotalar Alignment May Not Affect Functional Outcomes in Fixed-Bearing Total Ankle Replacement: A Retrospective Cohort Study

HSS Journal ® ◽

10.1007/s11420-019-09728-5 ◽

2019 ◽

Vol 16 (S2) ◽

pp. 300-304

Author(s):

Natalie M. Nielsen ◽

Guilherme H. Saito ◽

Austin E. Sanders ◽

Scott J. Ellis ◽

Carolyn M. Sofka ◽

...

Keyword(s):

Cohort Study ◽

Retrospective Cohort Study ◽

Functional Outcomes ◽

Retrospective Cohort ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Ankle Replacement

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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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Evaluation of Hindfoot Alignment After Fixed- and Mobile-Bearing Total Ankle Prostheses

Foot & Ankle International ◽

10.1177/1071100719891160 ◽

2019 ◽

Vol 41 (3) ◽

pp. 286-293

Author(s):

Federico G. Usuelli ◽

Camilla Maccario ◽

Cristian Indino ◽

Luigi Manzi ◽

Fausto Romano ◽

...

Keyword(s):

Anterior Approach ◽

Sagittal Alignment ◽

Mobile Bearing ◽

Lateral Approach ◽

Total Ankle Replacement ◽

Fixed Bearing ◽

Hindfoot Alignment ◽

Ankle Replacement ◽

Temporal Course ◽

Over Time

Background: End-stage ankle arthritis can involve malalignment of the ankle in both the coronal and sagittal planes. Up to 33% to 44% of patients who present for total ankle replacement (TAR) 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 changed over time. Specifically, we measured coronal and sagittal alignment of both the ankle and hindfoot complex. Methods: A retrospective study was performed on 2 independent groups of patients undergoing 2 different systems for total ankle replacement: Zimmer (lateral approach, fixed-bearing) and Hintegra (anterior approach, mobile bearing). Specific demographic data and radiographic data were measured. Within-group comparisons were performed using 1-way repeated measures ANOVA, analyzing the temporal course of clinical data within the Hintegra and Zimmer groups. Results: At the ankle joint, as measured by the α and β angles ( P > .05), the position of the components remained relatively similar in both the fixed- and mobile-bearing TAR at 24-month follow-up. The sagittal alignment, as measured by the TT (tibiotalar) ratio, demonstrated a posterior shifting of the talus in the mobile bearing group ( P = .036). Although the fixed- and mobile-bearing TAR had both significant hindfoot alignment improvement between the preoperative radiographs and at 24 months, over time, the fixed-bearing ankle had a significant increase in both the hindfoot alignment view angle and hindfoot alignment distance ( P < .001), suggesting a possible dynamism of the hindfoot in the fixed-bearing TAR. Conclusion: The lateral-approach fixed and anterior approach mobile-bearing implants maintained coronal and sagittal alignment in the short term; the temporal course of the lateral approach fixed-bearing ankle showed an increase in the valgus positioning of the hindfoot. The anterior approach mobile-bearing implant maintained its hindfoot alignment over the course of the study. Level of Evidence: Level III, case-control study.

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Scaphoid Nonunion Is a Disabling Problem in a Military Population

Hand ◽

10.1177/15589447211003177 ◽

2021 ◽

pp. 155894472110031

Author(s):

Nicholas H. Lake ◽

Rafae Khan ◽

Kyle W. Mombell ◽

Mary Fergus ◽

Dominic Gomez-Leonardelli

Keyword(s):

Functional Outcome ◽

Military Service ◽

Functional Outcomes ◽

High Rate ◽

Scaphoid Nonunion ◽

Military Population ◽

Outcome Scores ◽

The Mean ◽

Return To Duty

Background Scaphoid nonunion can occur in up to 55% of displaced scaphoid fractures. Long-term functional outcomes of this injury are lacking. In addition, no study has published rate of return to active military service after this injury. Our goal was to educate providers and patients on expected functional outcomes and return to duty after treatment of scaphoid nonunion. Methods We conducted a retrospective review of patients who underwent scaphoid nonunion repair at our institution from 2008 to 2017. The primary outcome measures were union rates, return to duty rates, and functional outcome scores obtained by telephone call. A total of 144 patients were included and 40 responded to our call for long-term follow-up. Results A total of 72% of patients achieved union after surgery, 18% required revision surgery, and 74% of patients were able to return to full duty after surgery. However, this number progressively decreased at 1, 2, and 5 years after surgery. At an average of 5.9 years after surgery, the mean Quick Disabilities of the Arm, Shoulder, and Hand (qDASH) score was 23.9. The mean qDASH for patients who achieved union (21.9) was significantly lower than those with persistent nonunion (29.2) ( P = .0115). Conclusion Scaphoid nonunion is a difficult problem in the military. We found a high rate of persistent nonunion often requiring revision to partial or full wrist arthrodesis. In addition, our long-term functional outcome scores demonstrate significant disability after this injury, even when union is achieved. This information can help us better counsel our patients and set expectations after treatment of this injury.

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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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Mid- to long-term results of total ankle replacement in patients with haemophilic arthropathy: A 10-year follow-up

Haemophilia ◽

10.1111/hae.13386 ◽

2017 ◽

Vol 24 (2) ◽

pp. 307-315 ◽

Cited By ~ 7

Author(s):

F. Eckers ◽

D. E. Bauer ◽

A. Hingsammer ◽

R. Sutter ◽

B. Brand ◽

...

Keyword(s):

Total Ankle Replacement ◽

Long Term Results ◽

Haemophilic Arthropathy ◽

Ankle Replacement

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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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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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2019 IFFAS Award for Excellence Winner: Peri-Prosthetic Cysts and Alignment in Total Ankle Replacement: A 3-D, Weight Bearing Topographical Study

Foot & Ankle Orthopaedics ◽

10.1177/2473011419s00049 ◽

2019 ◽

Vol 4 (4) ◽

pp. 2473011419S0004

Author(s):

Francois Lintz ◽

Jef Mast ◽

Nazim Mehdi ◽

Alessio Bernasconi ◽

Cesar de Cesar Netto ◽

...

Keyword(s):

Weight Bearing ◽

Total Ankle Replacement ◽

Coronal Plane ◽

Unequal Distribution ◽

Hindfoot Alignment ◽

Cyst Volume ◽

Ankle Replacement ◽

The Mean ◽

The Difference

Category: Ankle, Ankle Arthritis Introduction/Purpose: Peri-prosthetic cysts (PPC) in Total Ankle Replacement (TAR) are a common failure cause but the mechanisms of their development remains unclear. One possible explanation could be hindfoot malalignment and subsequent unequal distribution of load inside the joint. However, how residual malalignment influences the evolution of PPC remains unclear. Computed tomography (CT) has demonstrated superiority on conventional radiography in the follow up of PPC. Weight Bearing CT (WBCT), by combining 3D imaging and weight bearing measurements seems a valid tool to investigate this further. The objective for this work was to study the effects of residual hindfoot deformity on the distribution of PPC in the coronal plane. We hypothesized that cysts would be found predominantly medially in varus configuration, and laterally in valgus configuration. Methods: Retrospective comparative study, ethics committee approved. Forty-eight cases of TAR were included, with relevant demographics. Inclusion criteria were cases of primary TAR with available WBCT imaging of their ankle as part of normal follow up. Exclusion criteria were subsequent implant revision or cyst grafting. In each case, the localization and size of PPC’s were documented and their volume calculated by approximation of the closest ellipsoid. Hindfoot alignment was evaluated by the percentage Foot Ankle Offset (FAO) (foot-length normalized 3D ratio between the midline of the foot and the center of the ankle) using a WBCT dedicated semi-automatic software. The mean FAO value with 95%CI for the population was calculated. The difference in medial and lateral cyst volume defined by their position relative to the median axis in the coronal plane was compared in varus and valgus cases by a Mann-Whitney non-parametric test for unpaired samples. Results: Demographic distributions of the series were 32% female, mean age 65 (45-85) years. Mean FAO value was 0.12% (95%CI -1.09 to 1.33). Mean follow up was 43 months (6 to 239). The mean total cyst volume per case was 1190,7 mm3. In varus cases (defined by FAO<-1.09%), the volume of medial cysts was greater than laterally by a mean 197 mm3, whereas in valgus cases (defined by FAO>1.33%), the volume of lateral cysts was greater than medially by a mean 332 mm3. The difference was statistically significant (p<0.05). There was a weak, significant positive correlation (r=0.25, p<0,001) between FAO and total cyst volume and a moderate, significant correlation (r=0,56, p<0,001) between time to follow up and total cyst volume. Conclusion: Our hypothesis was confirmed. Periprosthetic cysts volume in this series of primary TAR was found to be relatively greater medially in postoperative varus configurations and vice-versa laterally in valgus. This confirms a possible correlation between the direction of residual hindfoot malalignment and the coronal localization of PPC in TAR, although this is certainly not the only pathophysiologic factor involved in PPC onset. Weightbearing CT may be helpful in Total Ankle Replacement follow up, in order to early detect PPC development and possibly to identify situations at risk of a more rapid evolution.

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