Shinichi Kosugi

In vivo kinematics of two-component total ankle arthroplasty during non-weightbearing and weightbearing dorsiflexion/plantarflexion

Relatively high rates of loosening and implant failure have been reported after total ankle arthroplasty, especially in first and second generation implants. Abnormal kinematics and incongruency of the articular surface may cause increased loads applied to the implant with concomitant polyethylene wear, resulting in loosening and implant failure. The purpose of this study was to measure three-dimensional kinematics of two-component total ankle arthroplasty during non-weightbearing and weightbearing activities, and to investigate incongruency of the articular surfaces during these activities. Forty-seven patients with a mean age of 71 years were enrolled. Radiographs were taken at non-weightbearing maximal dorsiflexion and plantarflexion, and weightbearing maximal dorsiflexion, plantarflexion, and neutral position. 3D-2D model-image registration was performed using the radiographs and the three-dimensional implant models, and three-dimensional joint angles were determined. The implanted ankles showed 18.1±8.6° (mean±standard deviation) of plantarflexion, 0.1±0.7° of inversion, 1.2±2.0° of internal rotation, and 0.8±0.6mm of posterior translation of the talar component in the non-weightbearing activity, and 17.8±7.5° of plantarflexion, 0.4±0.5° of inversion, 1.8±2.0° of internal rotation, and 0.7±0.5mm of posterior translation in the weightbearing activity. There were no significant differences between the non-weightbearing and weightbearing kinematics except for the plantarflexion angle. Incongruency of the articular surface occurred in more than 75% of the ankles. Our observations will provide useful data against which kinematics of other implant designs, such as three-component total ankle arthroplasty, can be compared.

In vivo kinematics and articular surface congruency of total ankle arthroplasty during gait

Relatively high rates of loosening and implant failure have been reported after total ankle arthroplasty. Abnormal kinematics and incongruency of the articular surface may cause increased contact pressure and rotational torque applied to the implant, leading to loosening and implant failure. We measured in vivo kinematics of two-component total ankle arthroplasty (TNK ankle), and assessed congruency of the articular surface during the stance phase of gait. Eighteen ankles of 15 patients with a mean age of 75±6 years (mean±standard deviation) and follow-up of 44±38 months were enrolled. Lateral fluoroscopic images were taken during the stance phase of gait. 3D-2D model-image registration was performed using the fluoroscopic image and the implant models, and three-dimensional kinematics of the implant and incongruency of the articular surface were determined. The mean ranges of motion were 11.1±4.6°, 0.8±0.4°, and 2.6±1.5° for dorsi-/plantarflexion, inversion/eversion, and internal/external rotation, respectively. At least one type of incongruency of the articular surface occurred in eight of 18 ankles, including anterior hinging in one ankle, medial or lateral lift off in four ankles, and excessive axial rotation in five ankles. Among the four ankles in which lift off occurred during gait, only one ankle showed lift off in the static weightbearing radiograph. Our observations will provide useful data against which kinematics of other implant designs, such as three-component total ankle arthroplasty, can be compared. Our results also showed that evaluation of lift off in the standard weightbearing radiograph may not predict its occurrence during gait.

TNK Ankle-The Ceramic 2-Component Total Ankle Prosthesis

The TNK ankle is a total ankle prosthesis which was first used in clinical settings in 1980, and which has been used in Japan for more than 30 years. The TNK ankle is only major model made from alumina ceramic materials, and is a 2-component type prosthesis with semi-constrained sliding surfaces. Due to various improvements in the surfaces in contact with the bone, the TNK ankle has consistently shown stable clinical outcomes, mainly in patients with osteoarthritis (OA) and rheumatoid arthritis (RA), although a loosening or sinking of the prosthesis has been found in some cases. In this review, we review the features and clinical outcomes of the TNK ankle, as well as the recently reported biomechanical research studies; in addition, we describe future perspectives pertaining thereto.

THREE-DIMENSIONAL POSTURE ESTIMATION OF FOOT BONES BY USING PLANTAR PLATE

Purpose: This paper proposes a method to easily and quantitatively estimate the changes in the foot bone three-dimensional (3D) posture from the 3D posture of a plantar plate without using X-ray or computed tomography (CT). Methods: The estimation functions from the posture of the plantar plate attached to the sole of a foot to the posture of the each bone are calculated using multiple regression analysis (MRA). Because we assumed that the posture of the plantar plate is related to each bone posture. Each bone posture can be estimated by substituting the plantar plate posture into the estimation function. Results: The adjusted coefficient of determination of the linear regression model (estimation function) of more than 90% was obtained by the estimation function, which was higher than 0.70. The estimation accuracy root mean square error (RMSE) of the translation and rotation were approximately within ±2.8mm and ±2.9∘, respectively. The RMSE/range of motion (RoM) values of the translation and rotation were approximately within ±22.1% and ±7.1%, respectively. Conclusion: The experimental results suggest that the 3D posture of almost all types of foot bones can be easily estimated using plantar plate posture and the linear regression model. This is an inexpensive, easy-to-apply method that can perform real-time measurement.

Clinical and Radiographic Evaluation of Total Ankle Arthroplasty with Custom Image Measurement Software

Category: Ankle Arthritis Introduction/Purpose: Ceramic 2-component total ankle prosthesis, TNK-Ankle, has been used clinically as standard prosthesis in severe ankle osteoarthritis or rheumatoid arthritis for long years in Japan. Two-component prosthesis would require more precise replacing because of more constraint than mobile type. We would report the outcomes of total ankle arthroplasty (TAA) with TNK-Ankle investigated radiographically using custom image measurement software and compared with clinical scores. Methods: Twenty four cases of total ankle arthroplasty with TNK-Ankle for osteoarthritis in stage 3b and 4 operated by an expert surgeon from 2009 to 2013 have investigated on X-rays of preoperative unaffected and postoperative affected ankles. Clinical outcomes by JSSF score based on AOFAS score and SAFE-Q, patient-based questionnaire, were compared with radiographic measurements. Image analysis performed with custom OpenCV software programmed for this study. This could match translucent X-ray images, an unaffected lateral ankle image and an implanted lateral ankle image with TNK-Ankle, and measure differences in geometry of ankle joint for tibia and talus between two images. Results: Postoperative clinical outcomes were improved from preoperative on JSSF (from 57 to 90) and generally affirmative on each item of SAFE-Q at forty-six months follow-up. But three ankles had some subsidence and loosening of prostheses, two ankles needed revision surgeries. Their ankles were classified for revision and loosening group, and the other ankles were classified for non-loosening group. X-ray image measurements with the custom software had elucidated two dimensional geometry of postoperative implanted ankle compared to preoperative unaffected ankle joint and its differences between two groups. In Revision and loosening group, the top of tibial plafond of tibial component of TNK-Ankle was placed 7 mm anterior to the top of unaffected tibial plafond and more than 4 mm anterior in non-loosening group. Inclination of component in loosening and revision group was a little more than in non-loosening group. Conclusion: In this study it was indicated that a few case may have loosening and revision after TAA even if it was performed on correct indication and by an expert surgeon, and clinical results may be concerned in geometry of implanted ankle. Precise replacing of total ankle prostheses by means of navigation and image-guided surgery may produce better results means. Data accumulation by more radiographic measurements with digital tools must become useful for future navigation system. Custom- made software development suitable to research demand like this study would be more efficient.