Talar Component Research Articles

An Analysis of 50 Consecutive Total Ankle Replacements Undergoing Preoperative Computerized Tomography Scan-Based, Engineer-Provided Planning From a Single Noninventor, Nonconsultant Surgeon

Preoperative computerized tomography (CT) scan-based, engineer-provided alignment plans and patient-specific pinning blocks for total ankle replacement (TAR) are available for use in the United States. However, nonbiased studies that justify the additional expense associated with this technology through support of the marketed benefits of less procedural complexity, less intraoperative radiation and reduced surgical time, are lacking. Therefore, to verify the manufacturer's proposed benefits, we sought to investigate our experience with this preoperative CT scan-based, engineer-provided plan and patient-specific pinning blocks during primary TAR. In review of our 50 TAR patients, we found that “perfect” radiographic alignment was not consistently achieved and the accuracy of component prediction was modest. Furthermore, the preoperative plans and patient-specific pinning blocks did not simplify the complexity of our operations since the operative time, intraoperative image intensification time and radiation dose per case all exceeded published historical TAR controls. Interestingly, we identified a significant difference in placement accuracy between the arced and flat-top talar component types that were implanted with the arced being more frequently malaligned. We did not find associations between preoperative deformity severity and accuracy of postoperative alignment. These findings suggest that it is imperative to have surgeons continue to rely on their own surgical planning and experience to achieve optimum radiographic alignment rather than depending on engineer-based recommendations or “surface matched” pinning blocks. Ultimately, we were unable to support the purported benefits of this CT scan-based, engineer-provided alignment plan and patient-specific pinning blocks for this manufacturer's primary TAR systems.

Infinity Ankle Arthroplasty Early Latin-America Experience and Patient Outcomes.

The promising data from Ankle Arthroplasty are consequence of the evolution of instruments and implants. Recent studies have shown good results in the short and intermediate follow-up, in addition to high patient satisfaction. The aim of this study is to present the results obtained with 49 cases treated with the Infinity total ankle prosthesis in 2 South America countries. This is a case series of 48 patients (27 women and 22 men), treated with 49 Infinity prostheses in Brazil and Colombia. They underwent surgical treatment between April 1, 2016, and January 18, 2020. We used the visual-analogue pain scale (VAS), the AOFAS score for ankle and hindfoot and the measurement of range of motion (ROM) in the pre- and post-surgical period. The radiological evaluation was performed on ankle radiographs in anteroposterior and lateral views, obtained in orthostasis, measuring the parameters suggested by Hintermann. Average follow-up was 4 years. VAS reduced from an average of 7.94 to 1.98; AOFAS increased from 28.02 to 83.16 and ROM increased from 11.45 to 28.08. Distal Tibial Slope is higher for higher improvements in VAS and lower for higher improvements in AOFAS and ROM. We observed 4 wound infections, 1 intra-op medial malleolus fracture. No bone cysts, tibial or talar components subsidence, polyethylene component wear or failure were observed. No salvation procedures were required in this series. This study results corroborates literature data showing great improvements in pain, functional pattern, and movement. Infinity Ankle Arthroplasty is a safe and reproducible procedure with good outcomes at a short-term follow-up. 4 - Case series.

Malalignment of the total ankle replacement increases peak contact stresses on the bone-implant interface: a finite element analysis

IntroductionMalalignment of the Total Ankle Replacement (TAR) has often been postulated as the main reason for the high incidence of TAR failure. As the ankle joint has a small contact area, stresses are typically high, and malalignment may lead to non-homogeneous stress distributions, including stress peaks that may initiate failure. This study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure.MethodsFinite Element (FE) models of the neutrally aligned as well as malaligned CCI (Ceramic Coated Implant) Evolution TAR implant (Van Straten Medical) were developed. The CCI components were virtually inserted in a generic three-dimensional (3D) reconstruction of the tibia and talus. The tibial and talar TAR components were placed in neutral alignment and in 5° and 10° varus, valgus, anterior and posterior malalignment. Loading conditions of the terminal stance phase of the gait cycle were applied. Peak contact pressure and shear stress at the bone-implant interface were simulated and stress distributions on the bone-implant interface were visualized.ResultsIn the neutral position, a peak contact pressure and shear stress of respectively 98.4 MPa and 31.9 MPa were found on the tibial bone-implant interface. For the talar bone-implant interface, this was respectively 68.2 MPa and 39.0 MPa. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. The highest peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component, and the highest shear stress of 98.5 MPa was found for the 10° posterior malaligned talar model. High contact stresses were mainly located at the edges of the bone-implant interface and the fixation pegs of the talar component.ConclusionsThe current study demonstrates that TAR malalignment leads to increased peak stresses. High peak stresses could contribute to bone damage and subsequently reduced implant fixation, micromotion, and loosening. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure.

97 HINTEGRA ankle prostheses: Results and survival at more than 5 years’ follow-up

BackgroundIn Europe, fixed-bearing implants predominate again in total ankle replacement (TAR). The present single-center single-surgeon study assesses the Hintegra® mobile-bearing implant (NEWDEAL). MethodsBetween November 2008 and November 2015, 97 Hintegra® were implanted in 94 patients: mean age, 62.4±10.9 years (26−83); 59% (57/97) male; normal mean body-mass index (BMI), 27.5 ± 4.3 kg/m2. Indications mainly comprised posttraumatic (40.2%), instability (29.9%) and primary osteoarthritis (16.5%). 17.5% of patients had prior surgery during the previous 6 months (9 fusions, 8 ligament reconstructions, and 4 osteotomies); in 59.8%, other procedures were associated to TAR. Functional, clinical and radiological follow-up was conducted at 1 year, 2 years and last follow-up (>5 years). ResultsNinety-four TARs were analyzed at a mean 81 ± 21.6 months (19−124). Revision-free survival was 76% (95% confidence interval (95%CI): 0.66–0.8), and explantation-free survival 92% (95%CI: 0.85–1) with 10 cases of curettage and 5 explantations.Mean AOFAS score improved from 41.8 ± 12.5 (21−69) to 77.5 ± 16.5 (24−100) up (p < 0.001); 75% of patients had no or only mild pain (p < 0.001). Clinical ranges of motion were 8.0 ± 7.1° dorsiflexion (p < 0.001) and 35.1 ± 9.4° plantar flexion (preoperatively, 34.1 ± 7.9°) (p = 0.71).Radiologically, tibial components were well-positioned; 87% of talar components were well-centered. Global ankle range of motion was 23.5 ± 10.2° (5−48) (p = 0.17). 54.6% of TARs showed posterior tibial calcification at follow-up. Risk of severe cyst (>1 cm) on CT was 36% (95%CI: 23–47) at a mean 77 ± 21.9 months (18−123). ConclusionHintegra® TAR incurred a low risk of revision, and is a reliable option for ankle osteoarthritis. Level of evidenceIV

Patient-Specific Instrumentation vs Standard Referencing in Total Ankle Arthroplasty: A Comparison of the Radiologic Outcome.

Background:Existing literature on the superiority of patient-specific instrumentation (PSI) in total ankle arthroplasty (TAA) over standard referencing (SR) is limited. Advantages presented include better implant alignment, shorter operating times, and increased accuracy of implant size prediction. The aim of this retrospective study was to analyze PSI in the hands of an experienced foot and ankle surgeon new to both PSI and SR for this specific implant, in regard to determining implant alignment, operative times, and radiologic short-term outcome and predicting implant size for tibial and talar components.Methods:Twenty-four patients undergoing TAA using PSI were compared to 25 patients using SR instrumentation. Outcome measures included alignment of the tibial component (α coronal plane, γ sagittal plane), the tibiotalar tilt (β), and the talar offset x on the sagittal view as well as the presence of radiolucent lines, operation time, and wound healing. Postoperative outcome was assessed at 6 weeks, 4 months, and 1 year postoperatively.Results:Implant positioning was similar in both groups, and no advantage in regard to the operative time could be seen when comparing TAA using PSI to SR. Implant size prediction was more reliable for the tibia than for the talus. Three patients (1 from the SR group and 2 from the PSI group) showed radiolucent lines around the tibial component. Two patients (both SR group) suffered delayed wound healing, albeit not requiring any additional measures.Conclusion:The PSI method did not show an advantage over SR in regard to positioning of the components or the duration of the surgery. The current study suggests that no initial advantage of PSI over SR are to be expected in standard total ankle replacement.Level of Evidence:Level III, retrospective study.

Finite element stress analysis of the bearing component and bone resected surfaces for total ankle replacement with different implant material combinations

BackgroundA proper combination of implant materials for Total Ankle Replacement (TAR) may reduce stress at the bearing component and the resected surfaces of the tibia and talus, thus avoiding implant failure of the bearing component or aseptic loosening at the bone-implant interface.MethodsA comprehensive finite element foot model implanted with the INBONE II implant system was created and the loading at the second peak of ground reaction force was simulated. Twelve material combinations including four materials for tibial and talar components (Ceramic, CoCrMo, Ti6Al4V, CFR-PEEK) and three materials for bearing components (CFR-PEEK, PEEK, and UHMWPE) were analyzed. Von Mises stress at the top and articular surfaces of the bearing component and the resected surfaces of the tibia and talus were recorded.ResultsThe stress at both the top and articular surfaces of the bearing component could be greatly reduced with more compliant bearing materials (44.76 to 72.77% difference of peak stress value), and to a lesser extent with more compliant materials for the tibial and talar components (0.94 to 28.09% difference of peak stress value). Peak stresses at both the tibial and talar bone-implant interface could be reduced more strongly by using tibial and talar component materials with smaller material stiffness (7.31 to 66.95% difference of peak stress value) compared with bearing materials with smaller material stiffness (1.11 to 24.77% difference of peak stress value).ConclusionsImplant components with smaller material stiffness provided a stress reduction at the bearing component and resected surfaces of the tibia and talus. The selection of CFR-PEEK as the material of tibial and talar components and UHMWPE as the material of the bearing component seemed to be a promising material combination for TAR implants. Wear testing and long-term failure analysis of TAR implants with these materials should be included in future studies.

Shape Approximation and Size Difference of the Upper Part of the Talus: Implication for Implant Design of the Talar Component for Total Ankle Replacement.

The implant design of the talar component for total ankle replacement (TAR) should match the surface morphology of the talus so that the replaced ankle can restore the natural motion of the tibiotalar joint and may reduce postoperative complications. The purpose of this study was to introduce a new 3D fitting method (the two-sphere fitting method of the talar trochlea with three fitting resection planes) to approximate the shape of the upper part of the talus for the Chinese population. 90 models of the tali from CT images of healthy volunteers were used in this study. Geometrical fitting and morphological measurements were performed for the surface morphology of the upper part of the talus. The accuracy of the two-sphere fitting method of the talar trochlea was assessed by a comparison of previously reported data. Parameters of the fitting geometries with different sizes were recorded and compared. Results showed that compared with previously reported one-sphere, cylinder, and bitruncated cone fitting methods, the two-sphere fitting method presented the smallest maximum distance difference, indicating that talar trochlea can be approximated well as two spheres. The radius of the medial fitting sphere RM was 20.69 ± 2.19 mm which was significantly smaller than the radius of the lateral fitting sphere RL of 21.32 ± 1.88 mm. After grouping all data by the average radius of fitting spheres, the result showed that different sizes of the upper part of the talus presented significantly different parameters except the orientation of the lateral cutting plane, indicating that the orientation of the lateral cutting plane may keep consistent for all upper part of the talus and have no relationship with the size. The linear regression analyses demonstrated a weak correlation (R2 < 0.5) between the majority of parameters and the average radius of the fitting spheres. Therefore, different sizes of the upper part of the talus presented unique morphological features, and the design of different sizes of talar components for TAR should consider the size-specific characteristics of the talus. The parameters measured in this study provided a further understanding of the talus and can guide the design of different sizes of the talar components of the TAR implant.

Prospective Three-Year Outcomes Comparing Cemented and Cementless Fixation in the Trabecular Metal Total Ankle Arthroplasty

Category:Ankle; Ankle ArthritisIntroduction/Purpose:In total ankle arthroplasty (TAA), the implant can be inserted with or without cement. The United States Food and Drug Administration (FDA) requires cement fixation on most TAAs, whereas cementless TAA can be performed in other countries. The laterally placed trabecular metal ankle replacement is inserted using a jig and a fibular osteotomy. The tibia and talus are reamed to match the curved contour of the replacement. Two rails on the tibial and talar component are used to transfix the cementless component onto bone. FDA licensing requires a bead of cement applied on the fixation rails to assist in early component fixation. The purpose of this study was to compare early and three-year results of TAA with and without rail cement performed in six countries.Methods:One hundred and twenty-one patients were prospectively enrolled (from 2014 to 2016) across 11 centers in six countries. Patients were assigned cement or no cement based on the surgeon's practice. EQ5D, AOS, and AOFAS scores were obtained preoperatively, six weeks and six months postoperatively, and yearly thereafter. Secondary endpoints were revision of metal components for infection or loosening. Statistical significance was tested by the Wilcoxon Signed Rank Test and set at p=0.05.Sixty ankles had cement; 61 ankles were press fit. Cement augmentation patients were heavier and older. Cement cases had longer surgical times (173 minutes, 95% CI 162.8 to 183.2, versus 150 minutes, 95% CI 139.9 to 158.4). The sites using cement fixation varied. Of 121 cases, 117 were followed at one year, 96 at two years, and 84 at three years. Three patients underwent revision and five withdrew (one died, two lost to follow-up, and two requested discontinuation).Results:The EQ5D scores demonstrated better outcomes for the press fit component without cement at six weeks (p<0.001), six months (p=0.001), one year (p=0.005), and two years (p=0.02), but not at three years (p=0.132). The AOS Disability scale demonstrated better outcomes for the press fit component at six weeks (p=0.008), six months (p=0.022), one year (p=0.020) and two years (p=0.024). The AOS Pain scale demonstrated better outcomes for the press fit component at six months (p=0.05). The AOFAS score demonstrated better outcomes for the press fit component at six weeks (p<0.001), but no significant differences thereafter. Survivorship for joint replacement (revision of metal components) was 97.4% for the full cohort. Three metal components were revised in three ankles in the cementless group (chi square not significant).Conclusion:Patient-reported outcome measures favored cementless, press fit fixation through two years postoperatively, with outcomes equalizing between the groups at three years postoperatively. Given the better early outcomes with the press fit design, there does not seem to be a need to augment fixation with cement in this total ankle implant design. There were two metal component revisions and one revision associated with loosening in the cementless group. The significant demographic differences between the groups indicate that a randomized clinical trial is needed to comprehensively define differences in early outcomes and to evaluate long-term results.

The INBONE-2 Total Ankle Prosthesis: Outcomes At 5 to 9 Years Follow-Up

Category:Ankle; Hindfoot; OtherIntroduction/Purpose:Short and medium term outcomes of the INBONE I and INBONE II tibial stems have been favorable. The INBONE-2 talus has been shown to have lower reoperation and failure rates compared to its predecessor, INBONE-1 at short term follow-up. The purpose of the present study was to assess mid-term outcomes for the INBONE-2 prosthesis at 5 to 9 years follow-up considering both the tibial and talar components.Methods:All patients who underwent primary total ankle arthroplasty (TAA) with INBONE-2 between July 2010 and July 2014 at a single institution and who were at least 5 years postoperative were included. A total of 15 ankles with a mean follow up 85 (range, 61-113) months met the criteria. Radiographs were assessed using coronal and sagittal alignment parameters preoperatively, at 6 weeks postoperative, and at the most recent follow-up. Medical records were reviewed and revisions, reoperations, and complications were classified according to the criteria established by Vander Griend et al. and Glazebrook at el., respectively.Results:Survivorship for the INBONE-2 at a mean of 85 months was 93.7%. Coronal and sagittal tibiotalar alignment improved after surgery (p=0.081, p=0.15), and was maintained at the most recent follow-up (p=0.684, p=0.837). One ankle (6.7%) required early component revision; while 4 (26.7%) required a non-implant related revision. Six complications (2 high grade, 1 intermediate, and 3 low) in 5 ankles (33.3%) were recorded according to the Glazebrook classification system.Conclusion:The present study is the first to report midterm follow-up after TAA with the INBONE-2. High survivorship, maintenance of correction, and a low incidence of major complications was observed. The most common complication overall was lateral gutter impingement, which accounted for the majority of the non-revisional reoperations.

Effect of Packaging on Polyethylene Fractures, Implant Survivorship and Cyst Formation in Mobile Bearing Total Ankle Replacements

Category:Ankle Arthritis; AnkleIntroduction/Purpose:The Scandinavian Total Ankle Replacement (STAR) is the most widely used mobile bearing total ankle arthroplasty (TAA) in the US. The polyethylene component is ultrahigh molecular weight polyethylene and is designed to articulate with both the tibial and talar component. Initial data on the STAR in the US reported polyethylene fracture rates of greater than 10% as well as a concern for cyst formation due to osteolysis. The manufacturer changed the packaging to foil to prevent potential oxidation of the polyethylene, which could predispose the polyethylene to failure. The objective of the study was to evaluate a cohort of patients with STAR performed before and after converting to foil packaging to determine if there is a difference in polyethylene survivorship and cyst formation.Methods:All primary TARs performed by the senior author from 2010-2017 were reviewed. Patients with a minimum 48 month follow up were included in the study. The two groups were stratified by those performed prior to August 2014 (PRE) and those performed after August 2014 (POST). Preoperative and most recent postoperative alignment was determined on weight bearing radiographs. The outcomes included polyethylene fractures and cyst formation in the two groups. Cysts were defined as those measuring greater than 1cm2 on plain radiographs. Patients were recommended to have surgery if cyst volume was greater than 2cm2. Chi-squared tests were used to detect significant differences in the rate of cyst formation between the two groups. Paired t- tests were used to determine difference in preoperative versus postoperative alignment, follow up length, and polyethylene component thickness and patient age at time of procedure between the two groups.Results:The PRE group had 35 patients with an average follow up of 75 months (range 48-118). The POST group had 15 patients with average follow up 55 months (range 48-60). There was no difference in preoperative versus postoperative radiographic alignment between the groups (p>0.05). Cysts were present in 9 (26%) patients in the PRE group versus 4 patients (26%) in the POST group. Nine patients (26%) needed a second surgery due to cyst formation in the PRE group versus two (16%) in the POST group (p>0.05). Four patients (11%) had a fracture of the polyethylene in the PRE group with an average thickness of 6.7mm (range 6-9) and 77 months (range 68-84) versus zero in the POST group. The average time to polyethylene exchange for cyst(s) or polyethylene fracture was 58.3 months.Conclusion:This study suggests that changes in packaging to limit oxidation of the polyethylene from plastic to foil did not appear to represent a difference in periprosthetic cyst formation. However, there was a trend for additional surgery related to periprosthetic cysts and increased risk for polyethylene fracture in the PRE group. These results could suggest the potential for oxidation changes that alter the wear characteristics and fragility of the polyethylene component. Confounding factors could include postoperative time and component thickness. Further investigation and longer follow-up will be needed to further delineate oxygenation impacts on TAA polyethylene components.

Does Sagittal Tibiotalar Alignment of TAR Predict Failure?

Category:Ankle ArthritisIntroduction/Purpose:The long term outcome of total ankle replacement is contingent on restoring the anatomic tibiotalar alignment of the ankle joint. Prior studies have mainly looked at the effect of coronal and hindfoot alignment of TAR on outcome and failure with few studies focusing on the effect of sagittal tibiotalar alignment. From these, we know that sagittal alignment has a greater impact on joint mechanics and that proper positioning of the talar component in the sagittal plane results in greater postoperative pain relief and better functional outcome, especially ankle range of motion. The goal of this study was to define a sagittal radiographic value that predicts failure in TAR.Methods:We analyzed the data of a retrospective patient cohort of consecutive TAR patients, which were treated from 2004 and 2011. Patients with two types of prosthesis were included, Salto Talaris (fixed bearing) and STAR (mobile bearing). All measurements were completed by two blinded observers, including the sagittal distal tibial articular angle (sDTAA), the lateral talar station (LTS) and the talar component inclination angle (γ angle). A total of 90 patients were included, 51 were male and 39 female patients. Seventy-seven patients received a Salto and 13 patients a STAR prosthesis. The average age was 63.7 years.Results:The mean sDTAA was 83.9 degrees and the mean γ angle was 21 degrees, both without significant difference in the two different prosthesis designs. A significant association (p=0.03) between post-op LTS as a continuous variable per unit increase and clinical failure was demonstrated, which included all the revision cases, with an odds ratio of 1.25. In addition a significant association (p=0.03) between increased LTS and sDTAA change of >5°, which is indicative of anterior subsidence, was shown. This was associated with an odds ratio of clinical TAR failure of 1.27.Conclusion:The abnormal radiographic post-op lateral talar station appears to predict clinical TAR failure and correlates with the abnormal sDTAA; the anterior translated talus loads the anterior tibia leading to anterior subsidence of the prosthesis. Limitation of this study is the inclusion of two different types of prosthesis designs.

Mid-Term Results after Lateral Transfibular Approach Total Ankle Arthroplasty

Category:Ankle Arthritis; AnkleIntroduction/Purpose:Continued improvements in total ankle arthroplasty (TAA) implant design have led to promising clinical outcomes. The lateral transfibular approach TAA allows for excellent visualization of the center of rotation of the ankle and allows for correction of rotational and sagittal deformity by shortening or lengthening of the fibula. Furthermore, the curved implant design allows for minimal bony resection. The purpose of this study is to report the medium-term clinical and radiographic results for consecutive patients who underwent the lateral approach TAA.Methods:IRB approval was obtained for this study. Consecutive patients who underwent lateral approach TAA for tibiotalar arthritis by a single surgeon were enrolled on a prospective basis from January 2013 to June 2015. This time period represented the initial case series of TAA performed by the surgeon. Patient reported outcomes (PROs) were collected including the Ankle Osteoarthritis Scale (AOS), 12-item short-form survey (SF-12), and Visual Analogue Pain Scale (VAS). The need for subsequent procedures was recorded. Radiographs were evaluated for preoperative and postoperative alignment using the lateral distal tibial angle (LDTA), tibiotalar surface angle (TTS), anterior distal tibia angle (ADTA), and the lateral talar station (LTS). Radiographs were also evaluated for the development of peri-implant lucency and subsidence. Data was tested for normality. T-tests were used to determine differences between preoperative data and postoperative data. A p<0.05 was considered significant.Results:53 patients who underwent 59 TAA procedures were included. Average follow-up was 5.7 +/- 0.9 years. Average age was 53 +/- 7.0. Comorbidities included smoking (11/53), diabetes (6/53), and prior procedures (33/53). Sixteen ankles (27%) underwent one or more subsequent procedures including gutter debridement (7/59), debridement for periprosthetic infection (3/59), and removal of hardware (7/59). All fibular osteotomies healed. Four ankles had asymptomatic peri-implant lucency or cysts (4/59). No patients had subsidence or required revision of the tibial or talar components. Coronal and sagittal alignment were significantly improved for all measures (p<0.05). VAS scores improved from a mean of 7.5 preoperatively to 1 at final follow- up (p<0.0001). SF-12 physical component scores improved from 34 to 41.5 (p=0.0227). AOS scores improved from 54.8 to 19.1 (p<0.0001).Conclusion:At medium term follow-up, patient reported outcomes remain significantly improved in patients after lateral approach TAA. There were very few radiographic findings of lucency and cyst formation, and all of these were asymptomatic. No revision of metal implants was required. Excellent deformity correction was achieved. The rate of subsequent procedures was high, although the rate of actual component revision was 0%. Lateral approach TAA appears to have overall good outcomes at medium term follow-up.

Accuracy of Weightbearing CT vs Non-Weightbearing CT Scans for Patient-Specific Instrumentation in Total Ankle Arthroplasty

Category:AnkleIntroduction/Purpose:Total ankle arthroplasty (TAA) is a popular and viable option for end stage ankle arthritis. Accuracy and reproducibility in placing the implant on the mechanical axis has been shown to be paramount in total ankle replacement. Patient specific pre-operative navigation up until this past year has been based off of non-weightbearing computerized tomography (CT). Our institution has created a protocol to use weightbearing CT in the pre-operative patient specific navigation for TAA using the ProphecyTM system. The purpose of our study was to compare the accuracy and reproducibility of implant alignment and size using WBCT versus prior studies using NWBCT for the Prophecy reports.Methods:Patients who underwent TAA using our WBCT protocol for their Prophecy scans had their charts reviewed to see if they met the proper inclusion criteria. Inclusion criteria was a primary TAA with proper follow-up to have first post-operative weightbearing radiographs. The first post-operative weightbearing radiographs were used to measure alignment of the axis of the implant in frontal and sagittal planes comparative to the tibial axis. These results were then compared to the pre-operative prophecy scans to determine reproducibility. The size of the implants components were also recorded for each patient and compared to the pre-operative predicted implant sizes from the patient specific reports. Our results were also compared to previous studies on reproducibility of patient specific navigation when using non-weightbearing CT.Results:Ten patients met our inclusion criteria of WBCT ProphecyTM preoperative planning. 100% of the TAA were within the intended target of less than 50 varus or valgus. The average post-operative coronal alignment was an average of 0.844 degrees. Average sagittal plane deformity was 1.88 degrees post-operative. Tibial component size was properly predicted 100% of the time and talar component in all but one patient.Conclusion:This data supports superior accuracy and reproducibility in pre-operative patient specific navigation when utilizing WBCT for TAA vs published controls with non-weightbearing CT.

Short-Term Efficacy and Safety of Combined Total Talus and Total Ankle Replacement

Category:Ankle; Ankle ArthritisIntroduction/Purpose:The indications for both total talus replacement (TTR) and total ankle replacement (TAR) are expanding. Combined total ankle-total talus (combined TAR) is a novel treatment option for patients with end-stage ankle arthritis and talar avascular necrosis (AVN) and patients with a prior TAR and talar component collapse. End-stage talar AVN with subchondral collapse is a challenging entity to treat. Historically, an alternative treatment option was tibiotalocalcaneal arthrodesis with structural allograft which results in fair outcomes including nonunion rates up to 40%. Combined TAR is a treatment option that theoretically maintains joint range of motion and restores anatomic alignment. The purpose of this study is to evaluate the short-term outcomes for combined TAR including pain, functional outcomes, radiographic outcomes, and complications.Methods:Consecutive patients who underwent combined TAR from 2016-2020 were retrospectively reviewed. All surgeries were performed by one of four fellowship-trained foot and ankle orthopaedic surgeons at a single academic institution. All talus implants were custom 3D printed total tali (Additive Orthopaedics, Little Silver, NJ), composed of an alloy primarily made of cobalt chrome. The implants were sized based on computed tomography scans of the contralateral talus and created to articulate with multiple TAR systems. Patient demographics, comorbidities, and surgical data were collected. Outcomes included the Visual Analog Scale (VAS) scores, radiographic alignment, range of motion, and complications. Data analysis was performed with paired t- tests and a significance level of p<0.05.Results:A total of 66 patients (67 ankles) were included with an average 12-month follow-up. There were 35 (52.2%) men, and the average age was 56.4 years old. The majority of patients (n=42, 62.7%) underwent combined TAR for talar AVN and tibiotalar arthritis while 21 (31.3%) patients were converted from an isolated TAR and 4 patients (6.0%) from an isolated TTR to combined TAR. A total of 23 (34.3%) patients had a previous talus fracture. Significant postoperative improvements compared to preoperative included: VAS (2.8 vs. 8.2; p<0.0001), ankle dorsiflexion (11.0° vs. 4.7°; p=0.0007), ankle plantarflexion (31.9° vs. 23.7°; p<0.0001), talar declination angle (20.7° vs. 11.6°; p=0.0007), Meary’s angle (2.2° vs. 10.4°; p=0.0043), and talocalcaneal height (79.6mm vs. 74.2mm; p <0.0001). There was a total of 10 (14.9%) complications, 7 (10.4%) of which required repeat surgery. There were 3 (4.5%) failures requiring explant, revision, or amputation (Table 1).Conclusion:Combined TAR is an efficacious and safe procedure. Patients experienced improvement in pain, ankle range of motion, and radiographic parameters postoperatively. This technique provides an anatomic treatment with preservation of ankle motion for patients with severely deficient bone stock due to talar AVN with ankle arthritis or failed TAR. To confirm these preliminary positive results, further studies are required including continued longer-term follow-up, prospective cohorts, and comparative analyses to other treatment options.

High Rate of Talar Collapse in STAR Total Ankle

Category:Ankle; Ankle Arthritis; HindfootIntroduction/Purpose:Despite substantial advancements in Total Ankle Arthroplasty (TAA), catastrophic failure due to implant subsidence remains a common and serious problem. While there are many studies of short and some of intermediate term follow- up of TAA, the number of long-term studies, especially with prospectively collected data, is much fewer, and the data on the incidence and impact of talar subsidence on those results is even more limited. Talar subsidence can be especially challenging to manage, given the limited talar bone stock and revision options as compared to the larger tibial bone stock. The purpose of this study was to evaluate the long-term incidence and characteristics of TAA implant failure.Methods:A prospectively collected database of TAAs performed in a tertiary referral center began enrolling in 1999. Medical records/radiographs were reviewed to evaluate outcomes of TAA and final radiographs were reviewed to identify implant failure from 1999-2016. Minimum radiographic follow-up was two years. Pre-operative and post-operative radiographs were measured for ankle, foot, and implant coronal and sagittal alignment Failure and reoperation rates of two different implants, the mobile bearing Scandinavian Total Ankle Replacement (STAR) and the fixed bearing Salto Talaris (Salto) were analyzed. Paired Student t- tests were performed between groups. TAA revision surgeries were excluded if the primary TAA was performed at another institution. Reoperations were recorded according to the Reoperations Coding System (CROCS) classification of the Canadian Orthopaedic Foot and Ankle Society (COFAS). There were 149 TAAs reviewed in 146 patients (136 STARs and 13 Saltos), with an average follow-up of 7.03 years (range 2-20 years).Results:Implant survival was 85.8% at mean 7 years. 25 TAAs demonstrated radiographic catastrophic failures, 21 underwent re- operation, and 4 declined revision surgery (Table 1). One failure was due to infection (CROCS 10), others were aseptic (CROCS 9). 13/25 failures were related to talar subsidence, all STARs (9.6% of all STARs in the series). Nine STARs (6.4%) had less severe talar subsidence but were asymptomatic, The STAR talar component, in total, subsided in 17.6% (24/136) of STARs, requiring revision in 13 (9.6%) of cases at mean 3.8 years post-op. There was no difference in pre-operative/post-operative radiographic alignment between the TAAs that did and did not fail. Twenty-six ankles (17.4%) underwent additional surgery with retention of metal components, bringing the total reoperation rate to 47/149 (31.5%).Conclusion:At long-term follow-up, TAA demonstrates reasonable implant survival rates, especially given the learning curve that includes STARs implanted prior to the Food and Drug approval study. We describe a unique mode of failure in STARs that highlights one of the risk factors for failure in total ankle arthroplasty. This represents the highest reported rate of talar subsidence in the literature with almost 10% of STARs demonstrating talar-sided failure at mean 7-year follow-up. Surgeons who utilize the STAR total ankle should be vigilant for talar subsidence given the high rates reported in this series.

Polka dot cementless talar component in enhancing total ankle replacement fixation: A parametric study using the finite element analysis approach

The primary stability of a total ankle replacement (TAR) is essential in preventing long-term aseptic loosening failure and could be quantified based on micromotion at the bone-prosthesis interface subjected to physiological loading during the normal walking. A 3D finite element analysis was conducted to investigate the current commercial STAR™ Ankle TAR bone-prosthesis interface relative micromotion (BPIRM) with addition of the talus bone minimum principal bone stresses (MPBS). Comparison was made to the proposed polka dot designs with the hemispheric feature that was demonstrated to enhance BPIRM. Parametric studies were conducted on the hemispheric features with changes in its diameter, length and shape. The FE results indicated high BPIRM at the talar component was primarily contributed by de-bonding (in the normal direction) between the talus bone and talar component. The MPBS were found to be most significant in the superior anterior and superior medial regions of the talus bone. When the pin length was increased from 1.5 to 3 mm, the BPIRM was predicted to fall below 50 μm in favour of bone in-growth. Based on the practicality of the prosthesis implantation during the surgical procedure, the final design that incorporated both the initial polka dot and 3 mm pin length in a crisscross manner was deemed to be a favorable design with reduced BPIRM and MPBS hence lowering the risk of long-term aseptic loosening.

Midterm Survivorship of the INBONE II Total Ankle Arthroplasty

The use of total ankle arthroplasty (TAA) in the treatment of ankle arthritis has grown substantially as advancements are made in design and surgical technique. Among the criteria guiding the choice between arthroplasty and arthrodesis, the long-term survival and postoperative outcomes are of crucial importance. Although outcomes of the INBONE I have been published, there is limited midterm survival data for the INBONE II. The purpose of this study was to determine the radiographic and patient-reported outcomes, and survivorship of this prosthesis in patients with a minimum 5-year follow-up. We retrospectively identified 51 ankles (46 patients) from 2010 to 2015 who underwent TAA with the INBONE II prosthesis at our institution. Of these, 44 cases had minimum clinical follow-up of 5 years (mean, 6.4; range 5-9). Median age was 66 years (range 42-81) and median BMI was 27.5 (range 20.1-33.0). A chart review was performed to record the incidence of revision and reoperation. Preoperative and postoperative radiographs were analyzed to assess the coronal tibiotalar alignment (TTA), the talar inclination angle, and the presence of periprosthetic lucencies and cyst formation. Preoperative and minimum 5-year postoperative Foot and Ankle Outcome Score (FAOS) subscales were compared. Survivorship was determined by incidence of revision, defined as removal of a metallic component. The survivorship at 5 years was 98% and the rate of reoperation was 7.8% (n = 4); 2 patients underwent irrigation and debridement for infection, 1 patient underwent a medializing calcaneal osteotomy, and 1 patient underwent open gutter debridement, 1 patient underwent a revision of a subsided talar component at 3.2 years after index surgery. Average postoperative TTA was 88.6 degrees, with 42 rated as neutral (85-95 degrees), 2 varus (<85 degrees), and no valgus (>95 degrees) ankles. At final follow-up, asymptomatic periprosthetic cysts were observed in 8 patients. All FAOS domain scores improved between preoperative and final follow-up. At midterm follow-up, we observed significant improvement in radiographic alignment and patient-reported outcome scores for the INBONE II total ankle prosthesis. In addition, this cohort has had a relatively low reoperation rate and high survivorship. Level IV, case series.

Accuracy of Weightbearing CT Scans for Patient-Specific Instrumentation in Total Ankle Arthroplasty.

Background:Total ankle arthroplasty (TAA) is a popular and viable option for end-stage ankle arthritis. Posttraumatic arthritis is the most common etiology of ankle arthritis, which creates the additional challenge of osseus deformity. Accuracy and reproducibility in placing the implant on the mechanical axis has been shown to be paramount in all joint arthroplasty including total ankle replacement. Patient-specific preoperative navigation is a relatively new technology for TAA, and up until this past year has been based off of nonweightbearing (NWBCT) or simulated weightbearing computed tomography (WBCT). Our institution has created a protocol to use WBCT in the preoperative patient-specific navigation for TAA using the Prophecy system. The purpose of our study was to compare the accuracy and reproducibility of implant alignment and size using WBCT vs prior studies using NWBCT for the Prophecy reports.Methods:All patients from July 2019 through October 2020 who underwent TAA were evaluated. Inclusion criteria consisted of primary TAA using patient-specific preoperative navigation who had postoperative radiographs in the 4-6-week time frame. Prophecy predictions and measurements were then compared to actual implant placement and size.Results:Ten patients met our inclusion criteria of WBCT Prophecy preoperative planning using 2 different implant systems. Preoperative deformities in this cohort were small. The average postoperative coronal alignment was 0.84 degrees, range 0.19 to 2.4 degrees. Average postoperative sagittal plane deformity was 1.9 degrees, range 0.33 to 5.05 degrees. Tibial component size was properly predicted in all patients, talar component in 9 of 10.Conclusion:This initial report supports accuracy and reproducibility in preoperative patient-specific navigation when using WBCT for TAA with these implants. All TAAs were within the intended target of less than 5 degrees varus or valgus.Level of Evidence:Level III, retrospective comparative analysis.

Effect of artificial surface shapes and their malpositioning on the mechanics of the replaced ankle joint for possible better prosthesis designs

BackgroundThe clinical outcomes of total ankle replacement are limited by prosthesis component malpositioning during surgery. The goal of this study is to assess the mechanical impact of this malpositioning in a validated computer model. MethodsIn a previously developed multi-body dynamic model of the human ankle complex three different artificial implants were designed, each one presenting a different approximation of the natural articular surfaces of the corresponding specimen. The most common implant translational and rotational malpositionings were defined and mimicked. Dynamic simulations of joint motion were run for the various surfaces and malpositionings. The same input loading conditions derived from a previous in-vitro experiment on the corresponding natural specimen were applied. FindingsFrom load-displacement graphs it was observed that all three artificial surfaces reproduced well physiological motion between the calcaneus and the tibia/fibula, with a maximum difference of 2°. It was found that antero-posterior translation of either the tibial or the talar component and inclination of the tibial component in the sagittal plane led to considerable increases in the range of motion. Antero-posterior and dorsiflexion of the tibial component resulted in an increased internal-external rotation by up to 3.5° and 4.0°, respectively. The corresponding increase of inversion-eversion was 5.0° and 6.5°. InterpretationThis study showed that relatively small surgical errors have great consequences in replaced joint mechanics. The present model can be used in future studies to analyse the effect of malpositioning with any specific current total ankle prosthesis.

Total ankle replacement along with subtalar joint arthrodesis: In-vitro and in-silico biomechanical investigations.

Total ankle replacement (TAR) and subtalar joint (STJ) fusion, are popular treatments for ankle osteoarthritis (OA). Short endurance limits the former, and movement disability comes with the latter. It is hypothesized here that fusion of the STJ can improve the longevity of the TAR prosthesis. In this study, a fresh human cadaver's ankle joint underwent TAR surgery, and strain patterns in the vicinity of prosthesis were recorded after the application of axial compressive load on tibia, resembling stance phase of the gait. Then, STJ of the same sample fused (FTAR), and a similar test procedure was pursued. The obtained strains in the FTAR were smaller than those of the TAR (p < .01). Finite element models of the tested samples were also made, and validated by experimental strains. The validated FE models were then employed to find stress distribution on the tibial plateau and prosthesis compartments. FTAR demonstrated more regular stress profiles in bone-prosthesis interface. Also, maximum von Mises stress in the talar component of the FTAR is approximately half of that in the TAR (8 and 15 MPa, respectively). Based on the results of this study, having a more symmetric load distribution on the prosthesis after STJ fusion, longevity of the TAR may likely increase.