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Postoperative Evaluation of the Total Ankle Arthroplasty

Joseph M. Bestic1, Jeffrey J. Peterson1, James K. DeOrio1,2, Laura W. Bancroft1, Thomas H. Berquist1 and Mark J. Kransdorf1,3

1 Department of Radiology, Mayo Clinic, 4500 San Pablo Rd., Jacksonville, FL 32224-3899.
2 Present address: Department of Orthopedics, Duke University Medical Center, Durham, NC.
3 Department of Radiologic Pathology, Armed Forces Institute of Pathology, Washington, DC.


Figure 1
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  		Fig. 1A —STAR arthroplasty device (Scandinavian Total Ankle Replacement, Waldemar Link) is cementless, three-component (mobile-bearing) design developed by H. Kofoed in 1981. Mobile, ultrahigh-molecular-weight polyethylene (UHMWPE) meniscus (thick black arrow) articulates superiorly with trapezoidal, flat, cobalt–chromium tibial plate (white arrow) and inferiorly with longitudinally ridged, convex, cobalt–chromium talar component (thin black arrow). Talar component possesses fin (asterisk, B) that inserts caudally into talus. Two characteristic cylindric bars (arrowheads) positioned on superior aspect of tibial component serve to anchor implant in subchondral tibia. Photograph of STAR arthroplasty device, oblique lateral view.

 

Figure 2
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  		Fig. 1B —STAR arthroplasty device (Scandinavian Total Ankle Replacement, Waldemar Link) is cementless, three-component (mobile-bearing) design developed by H. Kofoed in 1981. Mobile, ultrahigh-molecular-weight polyethylene (UHMWPE) meniscus (thick black arrow) articulates superiorly with trapezoidal, flat, cobalt–chromium tibial plate (white arrow) and inferiorly with longitudinally ridged, convex, cobalt–chromium talar component (thin black arrow). Talar component possesses fin (asterisk, B) that inserts caudally into talus. Two characteristic cylindric bars (arrowheads) positioned on superior aspect of tibial component serve to anchor implant in subchondral tibia. Anteroposterior radiograph of STAR arthroplasty device.

 

Figure 3
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  		Fig. 2A —Buechel-Pappas total ankle prosthesis (Endotec). Similar to STAR (Scandinavian Total Ankle Replacement, Waldemar Link) device, Buechel-Pappas ankle replacement is cementless, three-component (mobile-bearing) design. Tibial component is stabilized by stem that extends into tibial metaphysis (arrowhead). Ultrahigh-molecular-weight polyethylene meniscus (thick arrow) glides along metallic talar component (thin arrow) stabilized by ridge on its undersurface (asterisk) that articulates with corresponding longitudinal groove on talar component. Design allows limited inversion and eversion of ankle joint without loss of congruity and requires minimal talar bone resection. Photograph of Buechel-Pappas arthroplasty device, frontal view.

 

Figure 4
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  		Fig. 2B —Buechel-Pappas total ankle prosthesis (Endotec). Similar to STAR (Scandinavian Total Ankle Replacement, Waldemar Link) device, Buechel-Pappas ankle replacement is cementless, three-component (mobile-bearing) design. Tibial component is stabilized by stem that extends into tibial metaphysis (arrowhead). Ultrahigh-molecular-weight polyethylene meniscus (thick arrow) glides along metallic talar component (thin arrow) stabilized by ridge on its undersurface (asterisk) that articulates with corresponding longitudinal groove on talar component. Design allows limited inversion and eversion of ankle joint without loss of congruity and requires minimal talar bone resection. Anteroposterior radiograph of Buechel-Pappas arthroplasty device.

 

Figure 5
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  		Fig. 3A —TNK (Japan Medical Materials) ankle prosthesis is cementless, two-component (fixed-bearing) device used almost exclusively in Japan. This device consists of fused ceramic tibial (thin white arrow) and flat ultrahigh-molecular-weight polyethylene tray (thick white arrow) components that articulate with convex ceramic talar component (black arrow). Several bone fixation methods have been used, including hydroxyapatite-coated beads, fixation screws, and biologic coating. This prosthesis requires large amount of bone resection and has been associated with high rate of subsidence. Photograph of TNK device, oblique frontal view.

 

Figure 6
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  		Fig. 3B —TNK (Japan Medical Materials) ankle prosthesis is cementless, two-component (fixed-bearing) device used almost exclusively in Japan. This device consists of fused ceramic tibial (thin white arrow) and flat ultrahigh-molecular-weight polyethylene tray (thick white arrow) components that articulate with convex ceramic talar component (black arrow). Several bone fixation methods have been used, including hydroxyapatite-coated beads, fixation screws, and biologic coating. This prosthesis requires large amount of bone resection and has been associated with high rate of subsidence. Anteroposterior radiograph of TNK device.

 

Figure 7
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  		Fig. 4A —Agility Total Ankle System (DePuy) has been available for use since 1984, making it longest-used total ankle replacement system in United States. Agility ankle is porous-coated, two-piece (fixed-bearing) implant with partially conforming articulation. Modular, concave polyethylene insert (asterisk) locks into tibial component (thin arrow). Talar component (thick arrow) articulates with tibial component with approximately 20° of external rotation. Syndesmotic fusion (double arrowheads, B) increases surface area of tibial component prosthesis–bone interface in attempt to resist subsidence while allowing fibula to share portion of load. Failure of syndesmotic fusion is associated with increased rate of failure [8]. Photograph of Agility device, oblique frontal view.

 

Figure 8
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  		Fig. 4B —Agility Total Ankle System (DePuy) has been available for use since 1984, making it longest-used total ankle replacement system in United States. Agility ankle is porous-coated, two-piece (fixed-bearing) implant with partially conforming articulation. Modular, concave polyethylene insert (asterisk) locks into tibial component (thin arrow). Talar component (thick arrow) articulates with tibial component with approximately 20° of external rotation. Syndesmotic fusion (double arrowheads, B) increases surface area of tibial component prosthesis–bone interface in attempt to resist subsidence while allowing fibula to share portion of load. Failure of syndesmotic fusion is associated with increased rate of failure [8]. Anteroposterior radiograph of Agility device.

 

Figure 9
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  		Fig. 5A —INBONE Total Ankle (INBONE Technologies, formerly Topez Orthopedics) is two-component (fixed-bearing) device with bone ingrowth anchoring stems in both tibial (thin arrow) and talar (arrowhead) components. Polyethylene insert (thick arrow) is attached to tibial component. Modular tibial stem consists of individual segments that can be customized for each patient. Photograph of INBONE device, frontal view.

 

Figure 10
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  		Fig. 5B —INBONE Total Ankle (INBONE Technologies, formerly Topez Orthopedics) is two-component (fixed-bearing) device with bone ingrowth anchoring stems in both tibial (thin arrow) and talar (arrowhead) components. Polyethylene insert (thick arrow) is attached to tibial component. Modular tibial stem consists of individual segments that can be customized for each patient. Anteroposterior radiograph of INBONE device.

 

Figure 11
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  		Fig. 6A —Salto Talaris Total Ankle replacement (Tornier) is two-component (fixed-bearing) device with anatomic design consisting of cobalt–chromium tibial (thick arrow) and talar (thin arrow) components. Slide-on ultrahigh-molecular-weight polyethylene insert (asterisk) is attached to tibial component and shows matching articular geometry with talar implant. Tapered fixation plug (arrowhead) on superior aspect of tibial component serves to secure implant against bone surface. Photograph of Salto Talaris device, lateral view.

 

Figure 12
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  		Fig. 6B —Salto Talaris Total Ankle replacement (Tornier) is two-component (fixed-bearing) device with anatomic design consisting of cobalt–chromium tibial (thick arrow) and talar (thin arrow) components. Slide-on ultrahigh-molecular-weight polyethylene insert (asterisk) is attached to tibial component and shows matching articular geometry with talar implant. Tapered fixation plug (arrowhead) on superior aspect of tibial component serves to secure implant against bone surface. Lateral radiograph of Salto Talaris device.

 

Figure 13
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  		Fig. 7A —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Anteroposterior view of STAR device depicts method of angular evaluation. Alpha angle ({alpha}) is formed by intersection of lines drawn parallel to flat plate of tibial component and long axis of tibial shaft on anteroposterior view (normal = 90°).

 

Figure 14
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  		Fig. 7B —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Lateral view of STAR device depicts method of angular evaluation. Beta angle (β) is formed by intersection of lines drawn parallel to flat plate of tibial component and long axis of tibial shaft (normal = 90°). Gamma angle ({gamma}) is formed by intersection of line drawn through long axis of talar component with line drawn from posterior talar component through middle of talar neck. Gamma angle in postoperative setting has been shown to range from 11.1° to –33.4°, with average measurement of 18.8° [10].

 

Figure 15
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  		Fig. 7C —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Anteroposterior (C) and lateral (D) views of STAR device depict method of linear evaluation of component position. Linear values are established by measuring position of components relative to surrounding osseous structures. Measurement "a" is perpendicular distance between tip of lateral malleolus and line drawn through base of tibial component. Measurement "b" is perpendicular distance from anterior aspect of talar component to line intersecting calcaneal tubercle and dorsal aspect of talonavicular joint. Measurement "c" is perpendicular distance from posterior aspect of talar component to line intersecting calcaneal tubercle and dorsal aspect of talonavicular joint.

 

Figure 16
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  		Fig. 7D —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Anteroposterior (C) and lateral (D) views of STAR device depict method of linear evaluation of component position. Linear values are established by measuring position of components relative to surrounding osseous structures. Measurement "a" is perpendicular distance between tip of lateral malleolus and line drawn through base of tibial component. Measurement "b" is perpendicular distance from anterior aspect of talar component to line intersecting calcaneal tubercle and dorsal aspect of talonavicular joint. Measurement "c" is perpendicular distance from posterior aspect of talar component to line intersecting calcaneal tubercle and dorsal aspect of talonavicular joint.

 

Figure 17
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  		Fig. 7E —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Sequential lateral views of STAR device depict small change ({approx} 4°) in gamma angle over course of approximately 3 years. Such angular measurements, although they are often not routinely used, facilitate detection of subtle changes in component position and can be helpful in providing evidence of quantifiable change to surgeon.

 

Figure 18
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  		Fig. 7F —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Sequential lateral views of STAR device depict small change ({approx} 4°) in gamma angle over course of approximately 3 years. Such angular measurements, although they are often not routinely used, facilitate detection of subtle changes in component position and can be helpful in providing evidence of quantifiable change to surgeon.

 

Figure 19
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  		Fig. 7G —Radiographic measurements for total ankle arthroplasty (illustrated using STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device). Angular and linear values can be defined to evaluate changes in component alignment and position that may signify component migration [8–10]. Coronal CT image obtained at time of follow-up radiograph depicted in F shows thin region of osteolysis involving medial aspect of talar component (arrows). Constellation of findings in this case is concerning for aseptic loosening. Concave undersurface of talar component clearly precludes adequate radiographic evaluation of this region, highlighting usefulness of CT in such circumstances.

 

Figure 20
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  		Fig. 8A —Zonal system (illustrated with STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device) offers advantage of more precise localization of abnormalities of components. In anteroposterior projection, tibial component can be divided into five zones by lines drawn perpendicular to tibial plate. Lines are drawn on each side of cylindric bars, yielding five individual zones (1–5, medial to lateral).

 

Figure 21
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  		Fig. 8B —Zonal system (illustrated with STAR [Scandinavian Total Ankle Replacement, Waldemar Link] device) offers advantage of more precise localization of abnormalities of components. In lateral projection, tibial component can be divided into three zones by lines drawn perpendicular to tibial plate. Lines are drawn at anterior and posterior aspects of cylindric bars, yielding three individual zones (A–C, anterior to posterior).

 

Figure 22
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  		Fig. 9 —Infection in 67-year-old man. Lateral radiograph of STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) shows several pockets of gas (arrows) in soft tissues of ankle secondary to superficial infection.

 

Figure 23
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  		Fig. 10A —Periprosthetic lucencies. Anteroposterior radiograph of STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) in 46-year-old woman shows ovoid radiolucency (circled in white) located in zones 4 and 5 of tibial component. At surgery, this radiolucency was found to represent polyethylene osteolysis. Note lateral migration of tibial component with associated remodeling of fibula (white arrow).

 

Figure 24
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  		Fig. 10B —Periprosthetic lucencies. Initial postoperative anteroposterior radiograph of STAR total ankle in 65-year-old woman shows slight discordance between surgical drill pathways (arrows) and cylindric bars of tibial component. This should not be confused with osteolysis.

 

Figure 25
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  		Fig. 10C —Periprosthetic lucencies. Lateral radiograph of a Buechel-Pappas total ankle (Endotec) in 41-year-old woman shows well-defined radiolucent region located in anterior tibia just above tibial component plate (arrowhead). Cultures were negative at time of implant removal. Note concomitant subsidence of talar component (black arrow) and prominent heterotopic bone extending into ankle joint around anterior and posterior aspects of tibial plate (white arrows).

 

Figure 26
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  		Fig. 11A —Aseptic loosening. Anteroposterior radiograph of STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) in 46-year-old woman shows marked lateral tibial component migration with extensive surrounding osteolysis (thick black arrow) and remodeling of fibula (thick white arrow). Stress fracture is present in medial malleolus (thin black arrow). Note lateral talar suture anchor (thin white arrow) from prior lateral ligamentous reconstruction.

 

Figure 27
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  		Fig. 11B —Aseptic loosening. Anteroposterior radiograph of Agility Total Ankle (DePuy) in 65-year-old woman shows marked subsidence and lateral tilt of talar component (black arrow). Large radiolucent focus is evident in medial malleolus (white arrow) with thin region of periprosthetic radiolucency about lateral aspect of tibial component (arrowhead). These changes have developed despite presence of successful syndesmotic fusion (asterisk). Both components were revised within 1 year of this radiograph, with sparse bone ingrowth evident on removal of components. Cultures were negative at time of surgery.

 

Figure 28
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  		Fig. 12A —Periprosthetic fracture. Alterations in stress distribution related to component size or position may lead to periprosthetic fractures. Malleolar fractures may also occur as result of excessive bone resection or during implantation of prosthesis [5]. Despite presence of medial malleolar screw, periprosthetic fracture (white arrow) can be seen in medial malleolus on anteroposterior radiograph of a STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) in 75-year-old woman. Note tiny round radiolucency (black arrow) related to wire pins used to secure saw guide during placement of device.

 

Figure 29
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  		Fig. 12B —Periprosthetic fracture. Alterations in stress distribution related to component size or position may lead to periprosthetic fractures. Malleolar fractures may also occur as result of excessive bone resection or during implantation of prosthesis [5]. Corresponding coronal CT image confirms periprosthetic fracture (arrow) involving medial malleolus. Extension of fracture line to level of tibial component is clearly shown.

 

Figure 30
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  		Fig. 13A —Migration of polyethylene spacer with ankle subluxation in 72-year-old man. Anteroposterior radiograph of STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) shows ankle subluxation and lateral migration of polyethylene spacer (arrow) with resultant malalignment. Such changes often occur as result of lateral ligamentous instability. Note suture anchor (arrowhead) from lateral ligamentous reconstruction performed at time of STAR device placement.

 

Figure 31
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  		Fig. 13B —Migration of polyethylene spacer with ankle subluxation in 72-year-old man. Coronal CT scan confirms significant lateral migration of polyethylene spacer (arrow) and facilitates more detailed evaluation of morphology and integrity of polyethylene component. Note loss of normally parallel superior and inferior surfaces of polyethylene spacer due to asymmetric wear medially (asterisk).

 

Figure 32
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  		Fig. 14A —Fracture of polyethylene component in 69-year-old man. Anteroposterior radiograph of STAR total ankle (Scandinavian Total Ankle Replacement, Waldemar Link) suggests damage to polyethylene spacer, as evidenced by abnormal lateral migration of wire marker embedded in spacer (arrow).

 

Figure 33
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  		Fig. 14B —Fracture of polyethylene component in 69-year-old man. Axial (B) and sagittal (C) CT images confirm fractured polyethylene component (asterisk). Note concomitant polyethylene osteolysis in tibia (arrow, C) that predominantly involves posterior aspect of zone B.

 

Figure 34
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  		Fig. 14C —Fracture of polyethylene component in 69-year-old man. Axial (B) and sagittal (C) CT images confirm fractured polyethylene component (asterisk). Note concomitant polyethylene osteolysis in tibia (arrow, C) that predominantly involves posterior aspect of zone B.

 

Figure 35
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  		Fig. 14D —Fracture of polyethylene component in 69-year-old man. Gross photograph of resected fractured polyethylene component.

 

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