Ankle Arthritis Research Articles

Evaluating Failure Mechanisms for Total Talus Replacement: A Case Series

Category: Ankle Arthritis Introduction/Purpose: Talar collapse can occur from a variety of etiologies and may pose a unique challenge to the foot and ankle surgeon due to the complexity of the deformity and associated adjacent joint degenerative change. Total talus replacement (TTR) has emerged as an attractive option to help patients return to activities sooner than with arthrodesis and improve pain and joint mechanics postoperatively. However, there is limited long-term data on the most recent generation of implants. In this multi- institution case series, we present the severe complications that can occur after TTR, including instability, infection, and adjacent joint osteoarthritis. Methods: We present three cases from Duke University Hospital in Durham, North Carolina, and the Hospital for Special Surgery In New York City, New York. All three patients were treated with a total talus replacement (TTR) during their clinical course and experienced subsequent complications. Clinical data and radiographs were collected from chart review under an IRB-exempt protocol. Results: Case 1 demonstrates the risk of ligamentous insufficiency leading to dislocation following placement of a TTR. This case highlights the posterior instability due to soft tissue mobilization and division. Case 2 highlights the risk for adjacent joint degeneration with TTR. Case 3 presents an instance of non-union following a total ankle and total talus replacement (TATTR) with subtalar arthrodesis. To our knowledge, this represents the first case of nonunion following TTR in the literature. Finally, we discuss our institution’s experience with infection following TTR and possible contributing factors to this specific procedural risk. Conclusion: TTR shows promise in the properly selected patient with end-stage talar collapse. However, heterogeneous surgical techniques, implant composition, indications, and patient demographic variables complicate the interpretation of the literature. Moreover, few studies report mid-to long-term outcomes after this procedure and the occurrence of adjacent joint OA is likely underreported in the literature. Thus, until further, high-quality studies with long-term follow-up validate the positive early outcomes of TTR, we urge extreme caution in patient selection, choice of implants, and surgical techniques.

Midterm Survivorship and Complications of the Cadence Total Ankle Arthroplasty

Category: Ankle Arthritis; Ankle Introduction/Purpose: The Cadence total ankle arthroplasty (TAA) system first entered clinical use in 2016. Short-term outcomes with a minimum of two-year follow-up time have demonstrated survivorship between 93.7% and 100% with improvements in patient-reported outcomes measures, coronal alignment, and range of motion1–4. The purpose of this study is to report the midterm survivorship and complications of Cadence TAA patients with a minimum of 4.5-year radiographic follow-up. Methods: A retrospective chart review was conducted to identify a total of 22 TAA patients with the Cadence implant and a minimum follow-up time of 4.5-years. Patient age, sex, body mass index, diabetes mellitus status, rheumatoid arthritis status, smoking status, laterality, and diagnosis for TAA were collected from patient chart reviews. Preoperative FAAM-ADL subscore, FAAM-Sport subscore, and VAS pain scores and the postoperative scores at the last follow-up visit was also collected. 13 out of 22 patients had preoperative FAAM-VAS scores available while 10 out of 22 patients had postoperative FAAM-VAS scores available. Postoperative complications in the form of wound-related issues and those requiring reoperation or revision were noted, with revision defined as removal or exchange of metal component. 5-view radiographs obtained preoperatively and at the last follow-up visit were used to measure coronal alignment, range of motion, evidence of subsidence or loosening, and osteolysis as previously described1. Results: 3 out of 22 patients required a revision surgery, 1 for loosening of tibial component and 2 for infection. 4 out of 22 patients underwent a reoperation, 2 for gutter debridement due to impingement or heterotopic ossification, 1 for periprosthetic medial malleolar fracture, and 1 for removal of painful medial malleolar screws. The average FAAM-ADL, FAAM-Sport, and VAS pain scores improved from 50.6, 26.5, and 59.9 to 69.5, 35.5, and 23.6, respectively. The coronal alignment angle decreased from 5.96 degrees from neutral to 2.31 degrees. The average dorsiflexion and plantarflexion angles were 14.74 and 17.18 degrees, respectively, for an average range of motion of 31.9 degrees. 3 out of 22 patients had evidence of osteolysis while no patients had evidence of loosening or subsidence. Conclusion: The midterm survivorship of Cadence TAA system in 22 patients was 86.4%. Excluding the two cases of infection which are typically not attributed to implant performance, the survivorship was 95.4%. The reasons for reoperation included impingement, heterotopic ossification, periprosthetic fracture, and removal of painful hardware. The average FAAM-ADL, FAAM- Sport, VAS pain scores and coronal alignment improved. Analysis of longer follow-up time in greater patient cohorts is necessary for clearer understanding of this fixed-bearing implant’s performance.

Predictors of Intraoperative and Early Complications in Total Ankle Replacement

Category: Ankle Arthritis; Ankle Introduction/Purpose: Predictors of intra operative and early complications following total ankle replacement (TAR) become more important as the incidence and indications for TAR continue to expand. Talar bone loss whether from avascular necrosis, osteoarthritis, or post traumatic arthritis can be a challenging problem to deal with in TAR. The aim of this study is to report predictors of complications in TAR with talar bone loss. Methods: A retrospective review using CPT codes for four surgeons over a three-year period at an academic institution was performed. A single surgeon reviewed the immediate preoperative plain radiographs for 200 consecutive patients for talar bone loss. The mortise and lateral views were used to calculate talar bone loss and then averaged (Fig 1). 37 patients were identified as having talar bone defects of greater than 20 percent when the two measurements were averaged. Our preoperative variables we looked at were size of talar defect, location, and cause of talar defect and postoperatively, the implant choice. Our primary outcomes were intraoperative fracture, reoperation, subsidence, and revision surgery. Results: The average follow up was 23 months. The average defect size was 54 percent with a range of 20 to 100 percent. Mann U Whitney tests were performed that showed a relationship between the lateral and overall percentage of talar bone loss being predictive of subsidence of the talar component. A Fischer exact test showed a that a chamfered talus cut was protective against subsidence. The mean of the talar bone loss for the chamfered components were 40% versus 58% in flat cut. There were no other significant differences when comparing complications, fracture, reoperation, or wound complications. Conclusion: While TAR for patients with talar bone loss can be a good option for the patient and surgeon it does have a higher complication rate than standard TARs. Careful attention should be given to the percentage of talar bone loss. Flat cut and revision style components were more likely to be used in worse situations, so it is not the authors belief that they are more prone to subsidence. All patients over 20% bone loss need extensive discussion regarding potential complications and additional procedures. Talar bone loss is a difficult problem to deal with but TAR is a viable option.

Intermediate Term Clinical Outcomes in Total Ankle Arthroplasty: The CU Total Ankle Registry

Category: Ankle Arthritis; Ankle Introduction/Purpose: Total ankle arthroplasty (TAA) is a common procedure to treat end stage ankle osteoarthritis. Despite recent increase in popularity, there is limited literature assessing clinical and patient-reported outcomes (PROs) in TAA procedures using 5 current generation implants. These measures are an important tool for physicians to better assess patient performance in daily activities. The purpose of this study is to characterize both PROs and clinical outcomes in primary and revision TAA surgeries using current generation prostheses performed by non-design surgeons at a single institution. Methods: Our institution maintains a prospective outcomes registry for patients undergoing TAA at our institution. Patient demographics, relevant case information, PROs and complications are collected. Collected PROs include PROMIS Physical Function (PF), Pain Interference (PI), Depression, Global Physical Health (GPH), Global Mental Health (GMH), and Foot and Ankle SANE. Records are categorized as a primary TAA, or revision involving either a polyethylene only exchange or complete hardware removal and replacement. Differences between groups were determined non-parametrically using Mann-Whitney U tests. In all statistical tests, a p value of less than 0.05 was considered significant. Results: A total of 259 patients were included for analysis; 223 primary and 36 partial or full revision. Average length of stay was 1.6 ± 1 days. There were 18 reoperations (6.95%), with no implant failures within 1 year. Five patients underwent implant revision at an average of 2.5 years. Of these, one was related to delayed infection at year 3, two due to hardware failure in year 2, and 2 polyethylene exchanges in years 2 and 5. All physical health PRO measures showed significant improvements post-operatively (p < 0.0001). Patients reported significant reductions in pain following TAA at 3-months (Figure 1a), and significant improvement of physical function after 6-months (Figure 1b). There were no significant changes in Depression or GMH (Figure 1d). Conclusion: Total ankle arthroplasty is a safe and effective procedure for end-stage ankle arthritis. Patients experience improvement in all physical health PRO metrics at all post-operative time points after 3 months. Complication and early failure rates are lower than that reported in the literature. Long term outcomes and implant longevity will be tracked using the CU Total Ankle Registry. Total ankle arthroplasty improves quality of life in patients suffering from ankle osteoarthritis. Further follow-up and patient enrollment in the CU Total Ankle Registry will help us to identify risk factors for complications and define implant lifespan.

Does Perioperative use of Bisphosphonate Affect Implant Revision Rate of Total Ankle Arthroplasty?

Category: Ankle Arthritis; Other Introduction/Purpose: It is unknown whether perioperative bisphosphonate (BP) use reduces revision rates in total ankle replacement arthroplasty (TAR) although its effect has been demonstrated to be effective in reducing revision rates in total knee or hip replacement arthroplasty. Therefore, the purpose of this study was 1) to investigate whether there is a relationship between the use of BP and the revision rate of TAR, and (2) to determine the effect of BP medication period on the revision rate of TAR. Our hypothesis was that the use of BP would lower the revision rate of TAR. Methods: We reviewed National Health Insurance Service data based on national health insurance service claim data and health care utilization, health screening, socio-demographic variables, medication history, operation codes, and mortality data for 50 million Koreans. From 2002 to 2014, 6391 of 7300 patients who underwent TAR were BP non-users, while 909 patients were BP users. The revision rate according to BP medication and co-morbidities was investigated. The Kaplan-Meier estimate and extended Cox proportional hazard model were also used. Results: The revision rate of TAR was 7.9% for BP users and 9.5% for BP non-users, which showed no significant difference (p=0.251). Implant survival over time decreased constantly. Adjusted hazard ratio for hypertension was 1.242 (p=0.017), while other co-morbidities such as diabetes had no effect on revision rate of TAR. Conclusion: We found that the perioperative BP use do not reduce the revision rate of TAR. Co-morbidities except hypertension did not affect the revision rate of TAR. More research regarding various factor affecting revision of TAR could be warranted.

Plain Ankle Radiographs Underestimate Valgus Tibiotalar Tilt in Progressive Collapsing Foot Deformity: A Comparative Analysis with WBCT

Category: Ankle Arthritis Introduction/Purpose: Detection and accurate assessment of valgus tibiotalar tilt are important for staging and surgical planning of progressive collapsing foot deformity (PCFD). Plain ankle radiographs (XRs) have been used to evaluate this condition, but recent literature suggests that XRs may underestimate ankle deformities when compared to weightbearing computed tomography (WBCT), which is becoming increasingly utilized in PCFD evaluation. However, the discrepancies between these methods have not been explored. This study aims to: 1) determine the difference in tibiotalar tilt measurements between XRs and WBCTs; 2) compare the prevalence of significant valgus tibiotalar tilt (>4 degrees) between XRs and WBCTs in PCFD patients; and 3) determine the radiographic characteristics of patients who exhibit a discrepancy between XR and WBCT in the presence of significant valgus tibiotalar tilt. Methods: One hundred thirty-eight PCFD patients (Mean age: 55.1 years) having both WBCT and ankle XRs were reviewed. On ankle XRs, tibiotalar tilt (TTXR) and medial distal tibial angle (MDTAXR) were measured. On WBCT, the TTWBCT and MDTAWBCT were assessed at three locations (25% [anterior], 50% [middle], and 75% [posterior] of the sagittal dimension of the distal tibial plafond) in coronal views (Figure 1). The degree of tibiotalar tilt and prevalence of significant valgus tibiotalar tilt were compared between TTXR and the TTWBCT. Bland-Altman plots compared the mean TT and MDTA from XRs to those of the three coronal WBCT images to determine which region in WBCT is most similar to the XRs in each measurement. The radiographic characteristics of patients with and without a discrepancy between XRs and WBCTs for the presence of significant valgus tibiotalar tilt were examined via subgroup analysis. Results: Mean TTXR and TTWBCT were 1.5 (standard deviation [SD] 3) and 4.1(SD 3) degrees, respectively, indicating that XRs underestimate tibiotalar tilt by 63.4%. The prevalence of significant valgus tibiotalar tilt was 10.1% on XRs and 37.7% on WBCTs. Half the patients (4/8) who had bone-on-bone contact with tibiotalar tilt on WBCT didn’t exhibit such findings on XR (Figure 1). Bland-Altman plots showed that TTXR and MDTAXR best correlate with middle TTWBCT and MDTAWBCT (Figure 2). Subgroup analysis revealed that patients who exhibited significant valgus tibiotalar tilt on WBCTs, but not XRs, had smaller anterior TTWBCT and MDTAWBCT than those without such discrepancy (p <.05, Table 1), indicating that patients with a greater varus deformity on the anterior distal tibia are more likely to exhibit the discrepancy. Conclusion: This study demonstrates that ankle XRs underestimate valgus tibiotalar tilt compared to WBCTs in PCFD patients. The ankle XR parameters had the strongest correlation with those of the midpoint of the tibiotalar joint in WBCT and understated anterior side tilt and distal tibial deformity, likely due to beam projection angle and superimposition. Based on the findings of this study, WBCTs may be useful for detecting actual deformities in the ankle joint in PCFD patients; nevertheless, surgeons must be cognizant that they may underestimate the deformity in the anterior ankle when using conventional radiographs to assess ankle deformities in PCFD.

Reliability of Cone Bean Weight-Bearing Measurements of the Postoperative Outcome of Total Ankle Arthroplasties and Inter-Method Reliability with Respect to the Weight Bearing x-rays

Category: Ankle Arthritis; Ankle Introduction/Purpose: Postoperative evaluation of the total ankle arthroplasty (TAA) alignment is a fundamental step in measuring the surgical outcome. The current reference standard, weight-bearing x-ray (WBXR), is subject to technical bias. Weight-bearing cone beam computer tomography (WBCT) allows visualization of the complex three-dimensional (3D) structure of the foot under the influence of its deforming forces. A WBCT-based measurement system to assess postoperative outcomes has yet to be validated. The purpose of this study was (1) to measure the surgical outcome of TAA using semiautomatic generated models, (2) to evaluate the agreement levels between two raters, and (3) to evaluate the inter-method reliability with respect to WBXR. Methods: Fifty-five consecutive patients were retrospectively viewed. Two raters independently created a 3D model using dedicated software. Each rater measured six different measurements: α angle tibiotalar angle, hind foot angle (HFA), β angle, γ angle, and Φ angle using a semiautomatic 3D model and one measurement, the tibiatalar ratio (TTR) using WBCT on sagittal view. Measurements were repeated two months apart in the same independent fashion. Results were compared to standard weight- bearing x-rays. Consequently, interobserver, intraobserver, and intermethod agreements were calculated. Results: All seven measurements showed good to excellent interobserver and interobserver reliability. (ICC 0.85-0.95). The intermethod agreement showed good agreement for the γ angle (0.79) moderate agreement levels for the α angle, TTS angle, β angle, and TTR (ICC 0.68, 0.69, 0.70, 0.69 respectively), a poor agreement for the HFA angle (ICC 0.25), and a negative agreement for the φ angle (ICC -0.2). Conclusion: Postoperative analysis of TAA using WBCT demonstrated good to excellent interobserver and intraobserver agreement and can be reliably used. When compared to WBXR, moderate to good agreement was measured for the sagittal and coronal alignment of the components. A poor agreement was measured for the coronal alignment of the hindfoot, and a negative agreement was measured for the axial rotation angle, indicating that the intermethod comparison is unreliable.

Diabetes is a Potential Predictor of Failure following Total Ankle Arthroplasty: A Systematic Review and Meta-Analysis

Category: Ankle Arthritis; Other Introduction/Purpose: The purpose of this systematic review and meta-analysis was to evaluate potential predictors of failure following total ankle arthroplasty (TAA) for the management of end stage ankle arthritis. Methods: During January 2023, the PubMed, Embase and Cochrane library databases were systematically reviewed to evaluate potential predictors of failure following total ankle arthroplasty for the management of end stage ankle arthritis. Data regarding surgical characteristics, subjective clinical outcomes, radiographic outcomes, odds ratios, hazard ratios, correlation coefficients, failure rates and complications were extracted and analysed. Results: In total, 15117 patients (15198 ankles) underwent TAA at a weighted mean follow-up of 64.0 ± 21.8 months. Pooled Odds ratio found that diabetes was a statistically significant predictor of failures following TAA (OR: 2.1; [1.9861, 2.2284], p = 0.003). Other variables such as age, gender, body mass index, implant type and arthritis aetiology were not associated with failure. Conclusion: This systematic review and meta-analysis found that the presence of diabetes mellitus was a statistically significant predictor of failure following TAA. However, there was marked heterogeneity between the included studies with regards to statistical data collection which significantly limits the robustness of the conclusions of this study. Thus, further higher quality research with more consistent data collection is warranted to identify potential predictors of failure post TAA.

Fusion Rates in Tibiotalocalcaneal Arthrodesis with Tantalum Coated Metal Cup Augmentation

Category: Ankle Arthritis; Ankle Introduction/Purpose: Tantalum coated metal spacers (TCMS) have recently been utilized to fill and provide structure to large bony defects in the hindfoot. TCMS have a porous structure and elastic modulus similar to cancellous bone, increasing resistance to collapse, as well as osteoconductive properties that allow for bony ingrowth. At this time, there is still a paucity of literature assessing the use and outcomes of TCMS in foot and ankle surgery, more specifically as bridging structures for large bony defects when performing tibiotalocalcaneal (TTC) arthrodesis. This study serves to assess clinical outcomes and fusion rates of patients who underwent TTC arthrodesis utilizing intramedullary nailing with tantalum coated metal cup augmentation for large bony defects. Methods: We retrospectively reviewed the charts of 20 patients who underwent TTC fusion with TCMS augmentation at our local tertiary care center between 2015-2021. The CT scans at the six-month post-operative window were reviewed by one orthopaedic surgeon to determine the presence of bony fusion, which was defined as having at least 50% fusion mass. From the initial cohort, we collected the following modified foot function index scores for 13 patients: PROMIS Physical Health (0-20), PROMIS Mental health (0-20), Foot Function Index (0-170), Activity Limitation Scale (0-30), Pain Scale (0-50) and Disability Scale (0-90). Results: The mean age of our cohort was 53.9 (± 12.9) with a mean CCI of 1.54 (± 1.127) and mean follow up of 451.5 days (± 353.3). Mean modified foot function index scores included: PROMIS Physical Health 12.15 (± 3.34), PROMIS Mental health 12.23 (± 4.82), Foot Function Index 91.08 (± 47.59), Activity Limitation Scale 15.00 (± 10.42), Pain Scale 25.00 (± 14.77) and Disability Scale 51.00 (± 25.06). The post-operative complication rate was 30.8% in which 3 patients required a revision surgery via nail dynamization and one patient required a below knee amputation due to an infected nonunion of the TTC arthrodesis. The overall fusion rate at the 6-month postoperative visit was 69.2%. Conclusion: Unlike prior studies, we were able to obtain 6-month post-operative CT scans to delineate successful fusions with a larger number of patients (n=13). Given the paucity of literature looking at TCMS augmented fusions in foot and ankle surgery, our data will contribute to our understanding and efficaciousness of this relatively new use of TCMS in foot and ankle surgery. Further studies are needed to evaluate the efficacy of TCMS augmented fusions as a viable surgical approach as well an alternative to standard nail dynamizations with structural grafts.

Dependence of Total Ankle Tibial Baseplate Stability Upon Bone Density

Category: Ankle Arthritis Introduction/Purpose: The success of total ankle replacement (TAR) in improving patient outcomes is linked to its initial stability after implantation. Limiting early micromotion between implant and bone improves longer-term stability. Tibial component design fixation features play a critical role in determining early stability, with retention of medial and lateral bone sidewalls and interference press-fit both used to supplement fixation. However, tibial component stability is likely also influenced by regional bone density characteristics, and the exact relationship between the two is not adequately understood. The goal of this study was to investigate how bone density affects tibial component stability and bone-implant interface micromotion between the tibial component of a specific TAR and the distal tibia, by using finite element analysis (FEA) during simulated gait. Methods: A commercially available TAR tibial component baseplate was virtually inserted into a computer model of the distal tibia from two patients with end-stage ankle arthritis. These patients were selected based on having different bone density profiles in the affected ankle. The tibia models were generated from patient CT scans, having a CT density-based inhomogeneous material distribution (Fig. 1a) that allowed for bone compaction after press-fit. The tibial component was modeled as titanium alloy material. Two different fixation cases were simulated using FEA: (1) retained medial/lateral sidewalls + line-to-line fit, and (2) retained sidewalls + 50µm interference press-fit. FEA was performed using body weight-scaled kinetic (forces/moments) profiles representing the stance phase of gait, applied to the distal implant surface, while the proximal tibia was held fixed. Press-fit was simulated prior to gait simulation (interference press-fit cases). Micromotions were defined as displacement differences between bone-implant closest nodal pairs, computed from FEA output. Results: For the case with sidewalls+line-to-line fit, micromotions were largest early and late in the stance phase of gait (Fig. 1b), with the largest micromotions observed at heel strike (0% stance). Dorsiflexion and inversion moments dominate in early stance, stressing the anterior edge of the tibia in contact with the implant, leading to relatively large posterior/lateral gapping (Fig. 1b, inset). The observed differences in micromotion between the two patients correlated with differences in bone quality at the tibia contact surface, particularly around the implant pegs (Fig. 1a). However, when interference press-fit was modeled, the differences in micromotion between the two subjects largely disappeared (Fig. 1c), as adequate bone compaction was generated around the interference regions with sufficient bone quality to resist micromotion (Fig. 1d). Conclusion: This study presents novel insight into the effect of TAR fixation features and the associated micromotion at the bone- implant interface in patients with varying distal tibia bone density. We found the stability of the tibial implant to be considerably affected by surrounding bone quality, but the influence of bone quality on implant stability was minimized when interference press- fit was introduced. While a more comprehensive understanding of TAR implant features and their performance is needed, we believe the results of this study clearly demonstrate the importance of bone quality and particularly implant interference press-fit in the stability of TAR implants.

Obesity Significantly Impacts Patient Reported Outcomes after Total Ankle Arthroplasty: Results from 615 Controls and 478 Patients with Obesity

Category: Ankle Arthritis Introduction/Purpose: There is limited data evaluating the effect of obesity on outcomes following total ankle arthroplasty (TAA), especially in adequate sample sizes to detect impacts on patient reported outcomes (PROs). The purpose of this study was to assess the effect of obesity on complication rates and PROs. Methods: This was a single-institution, retrospective study of 1,093 primary TAA performed between 2001 and 2020. Minimum follow-up was 2 years. Patients were stratified by body mass index (BMI) into Control (BMI=18.5-29.9; n=615), Obesity Class I (BMI=30.0-34.9; n=285), and Obesity Class II (BMI>35.0; n=193) groups. Patient information, intraoperative variables, postoperative complications, PRO measures were compared between groups using univariable statistics. Multivariable Cox regression was performed to assess risk for implant failure. Mean follow-up was 5.6 years (sd:3.1). Results: Compared to Control and Class I, Class II patients had the lowest mean age (p=0.001), highest mean ASA score (p < 0.001), and greatest proportion of female sex (p < 0.001) and Black/African American race (p=0.005). There were no statistically significant differences in postoperative complications (infection, implant failure, or impingement) across the BMI classes (p>0.05). Preoperatively, Class II had lower (worse) mean scores for FAOS Pain and ADL subscales than Controls (posthoc pairwise p< 0.001 for both). At final follow-up, both Class II and Class I had lower (worse) mean SMFA (posthoc pairwise p< 0.001 and p=0.030, respectively) and SF36 scores (posthoc pairwise p< 0.001 and p=0.005, respectively) than Controls. Conclusion: At midterm follow-up, obesity was not associated with increased rates of complications after TAA. Patients with obesity reported worse musculoskeletal function and overall quality of life after TAA but there was no differential improvement in PROs across BMI classes. To our knowledge, this is the largest single institution study to date examining the effect of obesity on outcomes after primary TAA.

2023 Roger A. Mann Award Winner: Younger Patients Undergoing Total Ankle Arthroplasty Experience Higher Complication Rates and Worse Functional Outcomes Scores

Category: Ankle Arthritis; Ankle Introduction/Purpose: Although many patients with postraumatic ankle arthritis are of a younger age, studies evaluating the impact of age on outcomes of primary total ankle arthroplasty (TAA) reveal heterogenous results. The purpose of this study is to determine the effect of age on complication rates and patient reported outcomes after TAA. Methods: This was a retrospective study of 1,185 primary TAA divided into 3 age cohorts (Age < 55, n=219; Age55-70, n=688; Age>70, n=278). Patient demographics, intraoperative variables, postoperative complications, and patient reported outcome measures were compared among groups using univariable analyses. Multivariable Cox regression was performed to assess risk for implant failure by age group. Mean follow-up was 5.7 years. Results: Compared to Age55-70 and Age>70 groups, Age < 55 patients had the lowest mean ASA score (2.2 vs 2.4 vs 2.5; p< 0.001) and highest rates of all complications (33.8% vs 23.1% vs 19.8%; p=0.001), implant failure (9.1% vs 6.0% vs 3.2%; p=0.022), and component removal (5.0% vs 2.8% vs 1.1%; p=0.030). Univariable and multivariable cox regression analysis revealed decreased risk for implant failure for Age>70 compared to Age < 55 patients (HR: 0.43 [95%CI: 0.19-0.94], p=0.034; and HR: 0.42 [95%CI: 0.18-0.95], p=0.038, respectively). Across the AOFAS Hindfoot and all FAOS subscales, Age < 55 group reported the lowest (worst) mean pre and postoperative scores (p < 0.001). The age < 55 group had the highest mean VAS score at final follow-up (22 vs 14 vs 14; p< 0.001). Conclusion: Studies involving large sample sizes with mid-to long-term follow up are critical to reveal age-related impacts on outcomes after TAA. Younger patients had higher rates of complications and implant failure and fared worse on patient reported outcome measures in the largest single-institution series to date evaluating the effect of age on outcomes in TAA.

Defining Normal Articular Characteristics of the Primary Joints of the Foot and Ankle: A 3D Hounsfield Algorithm Weight Bearing CT Study

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: To properly treat osteoarthritis-(OA) patients, a grading-system is used to diagnose the stage-of-the- disease. The current gold-standard system, which relies on plain-2D-radiographs, is subjective, categorical, and lacks reliability. Using WBCT-images, 3D-Hounsfield-Unit-(HU) algorithms have been developed to measure the intensity of each image voxel across the joint-space, highlighting transitions between cancellous/subchondral bone and joint-space. The purpose of this study was to analyze and define normal standard values of joint-space-width (JSW) in the four essential joints of the foot-and-ankle (tibiotalar (ankle), subtalar (ST), talonavicular (TN), and first-metatarsophalangeal- (MTP) -joints) using an objective computational WBCT-HU algorithm in healthy non-arthritic feet. We hypothesized that the measurements of JSW and HU distributions across each of the four-essential-joints of the foot-and-ankle would be significantly different from each other, respecting local anatomy and unique functional characteristics of each joint. Methods: Retrospective-comparative-study, we evaluated WBCT-scans of 30 healthy ankle-joints, 28 ST-joints, 26-TN joints, and 30 1st-MTP-joints of control volunteers with no radiographic signs of foot-and-ankle OA. For each-joint, we used dedicated software to define a volume-of-interest (VOI) cube centered on the joint space. Five HU linear search arrays were then defined within this 3D VOI perpendicular to the articular-surface of each-joint, including four projections in each quadrant, and one in the center of the VOI (Figure 1). Image intensity profiles were generated for each search array crossing the transition from cancellous- to-subchondral bone, across the joint-space, back to subchondral-and-cancellous-bone (Figure 2). This profile was used to calculate JSW and to measure HU contrast in the region. Comparisons between the JSW of each joint and within each-joint were accordingly performed using paired t-tests or paired Wilcoxon. Significance was considered for p-values < 0.05. Results: The median-value and 95%-Confidence-Intervals-(CI) for JSW were 4.07mm [CI:3.73–4.20] for the ankle-joint; 4.07mm [3.95–4.44] for the ST-joint; 3.24mm [3.19–3.46] for the TN-joint; and 3.70mm [3.64–4.12] for the 1st-MTP-joint. The TN JSW was significantly narrower than the JSW in the ankle (p=0.0007), ST (p < 0.0002), and 1st-MTP-joints (p=0.0034) (Figure-3). JSW- values were similar across the entire ankle, ST and 1st-MTP-joints. In the TN-joint, the dorsal aspect of the joint was found to be slightly but significantly wider-than the plantar-aspect (p < 0.001). Regarding HU-contrast, we found a progressive increase in the overall contrast from proximal-to-distal (p < 0.001), with a mean HU contrast-value and 95%-CI of respectively 71.8[67.3–76.3] for ankle, 92.4[87.8–97.1] for ST, 84.1[79.2–88.9] for TN, and 101.3[96.9 – 106.8] for 1st-MTP-joints. The only joints with similar HU-contrast were ST and TN. Conclusion: We utilized a novel WBCT-3D-HU measurement algorithm to assess the normal JSW and HU contrast of the four- essential mobile joints of the foot-and-ankle. We found the JSW to be similar (~4mm) in the ankle, ST, and 1st-MTP joints. The TN-joint however, demonstrated a significantly narrower JSW when compared to the other 3 joints. HU-contrast increased progressively from proximal-to-distal, being less prominent in the ankle, similarly increased in TN and ST, and maximum at the 1st-MTP joint. This study's joint characteristic normality data provide a foundation for future-work developing an objective WBCT-based 3D HU-algorithm staging-system for OA-disease-progression in the foot-and-ankle joints.

The Effect of Diabetes Mellitus on Total Ankle Arthroplasty Outcomes

Category: Ankle Arthritis; Ankle Introduction/Purpose: The utility of total ankle arthroplasty (TAA) for management of end-stage ankle arthritis continues to increase. Postoperative infection after TAA is a devastating complication leading to additional surgeries, hospitalizations, long term antibiotics, arthrodesis, and sometimes amputation. Diabetes has been shown to be associated with postoperative infections following other orthopedic procedures. While the majority of literature demonstrates an association between diabetes and post- operative complications following TAA, other studies have demonstrated no such association. The goal of this study was to determine if diabetes influences the outcomes following TAA. Methods: An insurance database was utilized to identify patients undergoing TAA for end-stage ankle arthritis with a concurrent diagnosis of diabetes based on CPT, ICD-9, and ICD-10 diagnosis and procedure codes from 2010 to 2021. The postoperative outcomes of all cause revision, periprosthetic joint infection, periprosthetic joint infection with revision, and aseptic revision were compared between diabetic and nondiabetic patients with a minimum 2-year follow up using Kaplan-Meier and Cox proportional hazards analyses. Patient demographics, comorbidities, and Charlson Comorbidity Index was queried and analyzed via univariate and multivariate analysis, along with 90-day postoperative outcomes. Results: The study population included 8,317 patients who underwent TAA, 345 of which had a concurrent diagnosis of diabetes, with a minimum of 2-year follow up from 2010 to 2021. After multivariate Cox proportional hazards analysis, the 5-year cumulative incidence of PJI was 7.3% in diabetic patients compared to 3.9% in nondiabetic patients, with a 95% increased risk of revision (HR 1.95, 95% CI: 1.15-3.30, P=0.01). Diabetic patients also demonstrated a 5-year cumulative incidence of septic revision rate of 1.4% compared to 0.4% in nondiabetic patients, with a 363% increased risk (HR 4.63, 95% CI: 1.22-17.52, P=0.02). After controlling for differences in demographics and comorbidities through multivariate analysis, diabetes was independently associated with an increased risk for stroke (OR 10.12, P=0.007). Conclusion: The incidence of post-operative complications, including increased risk of 5-year risk of periprosthetic joint infection and septic revision was higher among diabetic patients compared to nondiabetic patients.

Autologous Matrix Induced Chondrogenesis plus Peripheral Blood Concentrate (AMIC+PBC) in Chondral Lesions at the Ankle as Part of a Complex Surgical Approach: 5-Year Follow-up

Category: Ankle Arthritis; Ankle Introduction/Purpose: The aim of the study was to assess 5-year-follow-up (5FU) after Autologous Matrix Induced Chondrogenesis plus Peripheral Blood Concentrate (AMIC+PBC) in chondral lesions at the ankle as part of a complex surgical approach. Methods: In a prospective consecutive non-controlled clinical follow-up study, all patients with chondral lesion at the ankle treated with AMIC+PBC from July 17, 2016 to May 31, 2017 were included. Size and location of the chondral lesions, the Visual-Analogue- Scale Foot and Ankle (VAS FA) and the EFAS Score before treatment and at 5FU were analysed and compared with previous 2- year-follow-up (2FU). Peripheral Blood Concentrate (PBC) was used to impregnate a collagen I/III matrix (Chondro-Gide, Wolhusen, Switzerland) that was fixed into the chondral lesion with fibrin glue. Results: One hundred and twenty-nine patients with 136 chondral lesions were included in in the study. The chondral lesions were located as follows (n (%)), medial talar shoulder only, 62 (46); lateral talar shoulder only, 42 (31); medial and lateral talar shoulder, 7 (10); tibia, 18 (13). The average for lesion size was 1.8 cm2, for VAS FA 45.7 and for EFAS Score 9.8. 2FU/5FU was completed in 105 (81%)/104(81%) patients with 112/111 previous chondral lesions. VAS FA improved to 79.8/84.2 and EFAS Score to 20.3/21.5 (2FU/5FU). No parameter significantly differed 2FU and 5FU. Conclusion: AMIC+PBC as part of a complex surgical approach led to improved and high validated outcome scores at 2FU/5FU. 2FU and 5FU did not differ.

Comparing Rates of Radiographic Baseplate Loosening Between Cement and Cementless INFINITY Total Ankle Prostheses

Category: Ankle Arthritis Introduction/Purpose: Total ankle replacement has risen in popularity as the contemporary treatment-of-choice for end-stage ankle osteoarthritis. INFINITY™ Total Ankle System (Stryker, Kalamazoo, MI) is one of the most frequently used ankle prostheses. Prior studies established positive functional outcomes; however, aseptic baseplate loosening has reported to occur in approximately one-third of patients. Aseptic baseplate loosening is seen radiographically either as shift in talar or tibial components or evidence of periprosthetic lucency. Aseptic baseplate loosening with persistent pain defines prosthesis failure, thus an indication for early surgical revision. Implementing bone cement may fixate and stabilize prostheses, potentially reducing incidence of aseptic baseplate loosening. This study aimed to determine if patients with cemented INFINITY total ankle prostheses had different incidence of aseptic baseplate loosening than those with cementless prostheses. Methods: Patients who underwent total ankle arthroplasty using the INFINITY total ankle prosthesis system between January 2016 and May 2022 (n = 28) were retrospectively identified using keyword search for “infinity” and Current Procedural Terminology (CPT) code 27702. Fourteen patients had prostheses affixed with cement, and fourteen patients had prostheses that were not cemented. Preoperative, immediate postoperative, and most recently available anteroposterior (AP), mortise, and lateral ankle X- rays were reviewed. Tibiotalar angle, talar tilt, and presence of visible postoperative lucency were assessed independently by two reviewers. Wilcoxon rank-sum test on quantitative variables and chi-square test on categorical variables were performed with 0.05 significance level. Results: Inter-rater reliability was above 94% for all measurements. Comparing the cemented to cementless sample group, difference in average age (59.5 years vs. 56.5 years, p=0.32) and sex (57.1% vs. 50.0% female, p=0.70) were not statistically significant. Pre-operative and immediate post-operative tibiotalar and talar tilt angles were not statistically significantly different between cement and cementless groups (p>0.31 for all comparisons). Only one patient in the cement group had evidence of periprosthetic lucency in the immediate postoperative period. Median follow-up was 362.5 days and 544.5 days in the cement and cementless group, respectively (p=0.52). Follow-up tibiotalar angles and talar tilt angle between cement and cementless groups were not significantly different (p>0.51 for all comparisons). Periprosthetic lucency occurred in 50% of both groups in the follow- up period (p=1.0). Conclusion: Patients with cemented INFINITY total ankle prostheses had equal incidence of aseptic baseplate loosening compared to patients with cementless prostheses. Continuing to examine methods for reducing incidence of baseplate loosening is significant for potentially reducing rate of early prosthesis revision and prosthesis failure, consequently improving quality of life for patients.

Outcomes after Bipolar Osteochondral Allograft Transplantation in the Ankle

Category: Ankle Arthritis; Ankle Introduction/Purpose: Surgical treatment options for symptomatic, full-thickness articular cartilage loss in the ankle are not consistently effective in restoring ankle function. Osteochondral allograft transplantation provides a standard-of-care alternative for patients, however, outcomes reported to date have been only fair, with a high incidence of reoperation and revision. However, recent cartilage storage and preservation techniques have significantly improved the percent viable chondrocytes at the time of implantation in OCAs. These high-chondrocyte-viability allografts should lead to improved survivability of OCAs and improved outcome measures. This study aimed to document the initial outcomes for patients undergoing bipolar OCA transplantation in the ankle after advances in tissue preservation, transplantation techniques, and patient management strategies. Methods: Patients with symptomatic tibiotalar arthritis were prospectively enrolled into a registry designed to follow outcomes after OCA surgeries in the ankle. All patients underwent complete OCA replacement of their tibial plafond and talar dome, with most undergoing fibular articular resurfacing. All OCA were size and side matched and preserved in Missouri Osteochondral Allograft Preservation System (MOPS). Patients followed a standardized, procedure-specific rehabilitation protocol after surgery, including remaining non-weight bearing for 8 weeks, weekly therapy visits, limited step count during recovery, and avoidance of high impact activities until 1 year after surgery. Patients followed-up with their physician at regular post-operative timepoints. Radiographs and patient reported outcome measures (VAS, AAOS Foot and Ankle, PROMIS PF, PROMIS Mobility) were obtained at each follow-up visit. Demographic and operative data were collected from the electronic medical record. All reported complications, reoperations, revisions, and failures were recorded in the EMR. Results: 14 patients were included for analyses with 12 undergoing primary OCA transplantation, and 2 undergoing revision OCA transplantation. Mean age and follow up was 36 and 44.1 months, respectively. All patients underwent tibia and talus OCA transplantation, with 10/14 including a fibula OCA transplantation. Initial success was 92.9% with one documented failure (tibial OCA collapse). Radiographic assessments indicated OCA integration and maintenance of joint space in 12 patients (85.7%). AAOS and VAS pain scores improved significantly from preoperative measures at each timepoint (p=.002, p=.03), while postoperative improvements in PROMIS Mobility and PROMIS Physical Function scores did not reach significance (p>0.15) (Table 1). Patients that were non-adherent to postoperative restriction and rehabilitation protocols, all 1-year postoperative PROs were significantly lower than for patients who were adherent. Conclusion: Ankle osteoarthritis in young patients continues to present a challenging dilemma. Previous attempts at large bipolar OCAs in the ankle have yielded fair, to poor, results. However, recent advances in bulk osteochondral allograft preservation has improved chondrocyte viability. Based on the results of our study, the use of high-chondrocyte-viability allografts for OCA transplantation is a viable option for the treatment of symptomatic bipolar osteochondral defects in the ankle joint. However, post operative rehab protocols are equally important in determining outcomes, and patient selection and education is key to ensuring successful outcomes. Longer term follow up is ongoing.

Transient Exposure of Tissue-Engineered Cartilage Analogs to Synovial Fluid Hematoma After Ankle Fracture Promotes Chondrocyte Death and Alters Gene Expression Toward an Osteoarthritic Phenotype

Category: Basic Sciences/Biologics; Ankle Arthritis Introduction/Purpose: The first stage of fracture healing consists of hematoma formation with recruitment of proinflammatory cytokines and matrix metalloproteinases. Unfortunately, when there is an intra-articular fracture, these inflammatory mediators are not retained at the fracture site, but instead, bathe the healthy cartilage of the entire joint via the synovial fluid fracture hematoma (SFFH). These inflammatory cytokines and matrix metalloproteinases are known factors in the progression of osteoarthritis and rheumatoid arthritis. Despite the known inflammatory contents of the SFFH, little research has been done on the effects of the SFFH on healthy cartilage with regard to cell death and alteration in gene expression that could lead to post- traumatic osteoarthritis (PTOA). Methods: SFFH was collected from 12 patients with intraarticular ankle fracture at the time of surgery. Separately, human chondrocytes were three-dimensionally cultured to create scaffold -free cartilage tissue analogues (CTAs) to simulate articular cartilage. Experimental CTAs (n=12) were exposed to 100% SFFH for 3 days, washed, and transferred to complete media for 3 days. Control CTAs (n=12) were simultaneously cultured in complete medium. Subsequently, CTAs were harvested and underwent biochemical, histological, and gene expression analysis. Results: Exposure of CTAs to ankle SFFH 3 days significantly decreased chondrocyte viability by 34% (p = .027). Gene expression of both COL2A1 and SOX9 were significantly decreased after exposure to SFFH (p= .012 and p=.0013 respectively). COL1A1 expression trended upward in the SFFH exposure group while there was no difference in RUNX2 and MMP13 gene expression. Quantitative analysis of Picrosirius red staining demonstrated increased collagen I deposition with poor ultrastructural organization in SFFH exposed CTAs. Conclusion: Exposure of an organoid model of healthy cartilage tissue to SFFH after intraarticular ankle fracture resulted in decreased chondrocyte viability, decreased expression of genes regulating normal chondrocyte phenotype, and altered matrix ultrastructure indicating differentiation toward an osteoarthritis phenotype.

Improved Survival Rates with Fixed Bearing Total Ankle Arthroplasty

Category: Ankle Arthritis Introduction/Purpose: With increasing numbers of total ankle arthroplasty (TAA) procedures being performed and a plethora of new survivorship data available, an updated literature review is needed to better understand the impact of different types of implants on outcomes of TAA. The purpose of this study is to compare the outcomes of fixed vs mobile bearing TAAs in the literature. Methods: A comprehensive search of MEDLINE for all articles published between 2004 and 2021 was conducted with a minimum two-year mean follow-up. Two reviewers evaluated each study to determine whether it was eligible for inclusion and abstracted the data of interest. Meta-analytic pooling of group results across studies was performed, examining implant survival and component failure. Seventy-three implant groups met inclusion criteria (only 3rd and 4th generation implants), composed of STAR (20), Salto (mobile bearing) (10), Salto Talaris (11 ), Hintegra (8), Zimmer (6), INBONE II (6), INBONE I (4), Infinity (4), Cadence (4). 41 groups (56.2%) were implanted with mobile bearing devices and 32 (43.8%) with fixed bearing implants. In total, 6498 subjects were included with a mean age of 61.77 years and mean BMI of 28.5 kg/m2. At mean follow-up of 62.2 months, the overall reoperation rate was 21.13% and metal component revision rate was 10.16%. Results: The mean follow-up of mobile bearing TAA studies (N=41) was 77.8 (range 24-188.4) months and fixed bearing studies (N=32) was 45.3 (range 24-85.2) months. Multivariate analysis of bearing type, controlling for follow-up duration, found fixed bearing implants had statistically significantly higher metal component survival rates (fixed=96.1%, mobile=87.9%, p=.001) ; however, there were no statistically significant differences in rates of reoperation (fixed=17.0%, mobile=24.8%, p=.768). When examining specifically tibial and talar component failure rates, there was no statistically significant difference between bearing type (fixed tibial=1.46%, mobile tibial=2.95%, p=.472) (fixed talar=2.19%, mobile talar=2.79%, p=.966). Overall implant survival rate at one, two, five, and ten years was 96.4%, 96.0%, 92.7%, and 79.4%, respectively, and did not differ by bearing type (Table 1). Conclusion: Implant survival was statistically significantly better for 3rd and 4th generation fixed bearing TAAs as compared to mobile bearing TAAs, controlling for length of follow-up. There was no statistically significant difference in total reoperation rate. This suggests that fixed bearing implants may offer improved implant survival compared to mobile bearing implants, though further research is needed to confirm these findings.

Mid- to Long-Term Outcomes of the STAR Total Ankle Replacement

Category: Ankle Arthritis; Ankle Introduction/Purpose: The Scandinavian Total Ankle Replacement (STAR) is a widely used ankle prosthesis, but mid- to long-term follow up remains limited. In thirteen different studies involving 939 STAR total ankle prostheses, the average duration of follow- up for recipients was 3.9 years. Thus, we sought to evaluate the STAR at the mid- to long-term interval with regards to survivorship, complications, and patient reported outcomes (PROs) in one of the largest series with the longest-term follow up to date. Methods: All patients managed with a primary STAR prosthesis at our institution from March 2002 through January 2017 were included in the analysis. Demographic characteristics including gender, race, age, diabetes status, body mass index (BMI), smoking status, American Society of Anesthesiologist (ASA) score, and surgery time were summarized. The cumulative incidence of implant failure was at 5 years and the last recorded time to event (8 years) were reported with 95% confidence intervals (CI). Paired t- tests were used to compare pre-operative and 5 year post-operative (±1 year) for PROs including Visual Analog Scale (VAS), Short Musculoskeletal Function Assessment (SMFA), Short-form-36 (SF-36), and American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot subscales. Additionally, intra- and post-operative complications were recorded. All statistical analysis were conducted in SAS 9.4 (Cary, NC). Statistical significance was assessed at α = 0.05. Results: 247 patients with a unilateral STAR procedure were included in this analysis. Demographics are listed in Table 1. The average number of years of follow-up was 5.71 ± 4.07 years. The cumulative incidence of implant failure at 5 years was 7.7% (95% CI 4.3%-12.5%). The last failure event occurred at 8 years post-implant. The cumulative incidence of implant failure at 8 years was 11.1% (95% CI 6.3%-17.3%) (Table 2, Figure 1). The most common post-operative complications were impingement (N = 39, 15.8%), ankle pain (N = 22, 8.9%), and implant failure (N = 16, 6.5%) (Table 3). With regards to PROs, patients significantly improved between baseline and 5-year follow up in all measures (all p< 0.001; Table 4). Conclusion: At mid- to long-term follow up, patients receiving the STAR prosthesis experienced a significant and durable improvement in PROs across multiple functional indices. Complication and failure rates were lower than those reported in previous series evaluating the STAR, with an observed survivorship of 88.9% at 8-year follow up.