Hiroaki Kurokawa

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.

Radiographic Morphologic Characteristics of Bunionette Deformity.

Background: Bunionette deformity is characterized as head hypertrophy, lateral bowing, or splaying of the fifth metatarsal, or a combination of these deformities. Most previous studies have focused on the fourth and fifth metatarsals; few have analyzed the radiographic morphologic characteristics of the entire foot. The morphologic characteristics of the entire foot in cases of symptomatic bunionette deformity were analyzed with a radiographic image-mapping system. Methods: The system was used for the morphologic analysis of 112 feet with symptomatic deformity and 123 asymptomatic control feet. The mapping system includes 2-dimensional coordinates. We compared morphologies of both groups on the basis of simple models prepared from x and y coordinates of each reference point, calculated by using the mapping system and various angle measurements. We set cutoff values and categorized cases according to Fallat’s system. We evaluated the characteristics of each type and a new deformity type (type V) wherein no measurement exceeded the cutoff values. Results: The heads of the third, fourth, and fifth metatarsals were more laterally displaced, and the angles between the metatarsal axes were larger in the deformity group. Comparison of deformity types showed that the morphology of the fifth metatarsal might be only one cause of deformity. The intermetatarsal angles between the second and third metatarsals and between the third and fourth metatarsals were larger in deformity type II and type V feet than in control feet. Additionally, the intermetatarsal angles between the third and fourth metatarsals and between the fourth and fifth metatarsals were larger in deformity type III and type IV feet than in control feet. Conclusion: We believe it is necessary to not only focus on the fourth and fifth metatarsals, but also assess the morphologic characteristics of the entire foot in patients with a bunionette, including splaying of all the metatarsals and the forefoot width, when planning surgery. Level of Evidence: Level III, retrospective comparative study.

The etiology of the end-stage varus type ankle arthritis evaluated by weight-bearing simulated computed tomography

Category: Ankle Arthritis Introduction/Purpose: In the patients with the varus type ankle arthritis, the stage of disease was classified according to the narrowing of tibiotalar joint using the weight-bearing ankle radiography. By the Takakura-Tanaka classification, the stage 4 ankle arthritis indicates more than half of the joint space was disappeared in the tibiotalar joint. Inclination of the surface of tibiotalar joint in the patients with stage 4 ranges from neutral to severely varus, that may confuse the etiology of staged ankle arthritis. The purpose of this study was clarifying the etiology of the stage 4 ankle arthritis combined with evaluating the syndesmotic instability using the weight-bearing simulated computed tomography(CT). Methods: Forty nine ankles with stage 4 varus type ankle arthritis were investigated. A weight-bearing simulated CT scan was taken in the neutral position of the ankle with a 300 N pressure from plantar side. In the axial view of the CT at 1 cm proximal to the tibial plafond, the distance between the fibula and the tibia was measured as the fibular clear space (FCS-CT). In the anteroposterior view of the weight-bearing radiography of the ankle, the angle between the tibial shaft and the joint surface of the distal end of the tibia was measured as the tibial anterior surface angle(TAS-Xp). The Pearson correlation coefficient was obtained to identify the correlations between the FCS-CT and the TAS-Xp. P values <0.05 were considered statistically significant. Results: The FCS-CT was 4.3±1.2 mm. The TAS-Xp was 81±4.9°. According to the Pearson correlation coefficient between the FCS-CT and the TAS-Xp, positive correlations were identified (r=0.45; p=0.0011). Conclusion: This study revealed the correlation between the inclination of the distal joint surface of the tibia and distance of the tibiofibular syndesmosis. In the patients with larger FCS-CT, syndesmotic instability may exist, that may lead to the distributed share stress in the tibiotalar joint without the inclination of the joint surface. In the patients with smaller FCS-CT, the varus stress directly transfer to the ankle joint, that may cause to the varus inclination of the distal joint surface of the tibia.

Clinical comparison of ankle arthrodesis with distal tibial oblique osteotomy for the patient with stage 3b ankle arthritis

Category: Ankle Arthritis Introduction/Purpose: Ankle arthrodesis (AA) has been applied for end-stage ankle arthritis. On the other hand, low tibial osteotomy has been applied for mild to moderate ankle arthritis, however distal tibial oblique osteotomy (DTOO) has come to be applied for end-stage arthritis and clinical results were reported to be favorable. The purpose of this study was to compare clinical outcomes after AA and DTOO. Methods: From 2011 to 2014, 37 patients with stage 3b ankle arthritis were treated surgically. In these patients, 25 whose talar tilting angle (TTW) was over 10 degrees with minimum follow-up of 1 year were investigated in this study. Seventeen patients were treated by AA and 8 were treated by DTOO. Clinical outcomes were assessed using the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale before surgery and at the latest follow up. The patient-based evaluation was performed at the latest follow up using Self-administered evaluation questionnaire (SAFE-Q). TTW and range of motion (ROM) of the ankle were also evaluated before surgery and at the latest follow up. In addition, rate of bony union and complications were investigated. Results: The average ages at the surgery were 60(41-77) years old in the AA group and 66(49-75) in the DTOO group. The average follow up periods were 32(15-49) months in the AA group and 29(13-52) in the DTOO group. Scores of the JSSF scale significantly improved at the latest follow up in both groups. In comparison between two groups, “Social functioning” and “General Health and Well-being” scores in SAFE-Q were significantly higher in the AA group than in the DTOO group. In contrast, ROM was higher in the DTOO group than in the AA group. There were no significant differences in TTW, bony union rate and complications. Conclusion: Ankle arthrodesis spoils the joint motion, however it restores stability and activity of the daily living, that leads to the higher levels of social functioning, general health and well-being.

Outcomes of Bilateral vs Unilateral Ankle Arthrodesis

Background: While ankle arthrodesis is a common treatment for severe ankle osteoarthritis, performing bilateral ankle arthrodesis is controversial because of associated problems, such as severe gait abnormality and bilateral loss of talocrural joint motion. Furthermore, few reports exist regarding the detailed outcomes of bilateral ankle arthrodesis. Therefore, we aimed to compare the outcomes of bilateral ankle arthrodesis with those of unilateral ankle arthrodesis, using both subjective and objective assessments. Methods: The data from 20 patients (10 each in the bilateral and unilateral groups), who underwent arthrodesis between 2005 and 2015, were retrospectively reviewed. The minimum follow-up duration was 2 years. Radiographic outcomes were assessed using radiographs and computed tomography. Clinical outcomes were assessed using the Japanese Society for Surgery of the Foot (JSSF) scale and the Self-Administered Foot Evaluation Questionnaire (SAFE-Q). Results: With the numbers available, no significant group differences were observed for any of the patient characteristics or postoperative range of motion. Mean JSSF scale scores significantly improved in both groups (P < .001); however, scores on the SAFE-Q subscale for “social functioning” were significantly lower in the bilateral group compared to the unilateral group (P = .049). Conclusions: Within the limitations of the current study design, bilateral ankle arthrodesis did not appear to be inferior to unilateral ankle arthrodesis, with the possible exception of social functioning ability. Thus, bilateral ankle arthrodesis can be considered a viable treatment option. Level of Evidence: Level III, retrospective cohort study.

Evaluation of Normal Ankle Cartilage by Magnetic Resonance Imaging (MRI) T1ρ Mapping

Category: Ankle Introduction/Purpose: With the recent remarkable progresses in image diagnosis using magnetic resonance imaging (MRI), it could be possible to evaluate articular cartilage in detail. T1ρ mapping by MRI has recently drawn attention as a noninvasive cartilage evaluation method. While its validity has been proven, there are no reports describing T1ρ mapping for the ankle; therefore, in this present study, T1ρ values of the articular cartilage surfaces of the talar dome were measured in healthy individuals. Methods: The study sample comprised 10 ankles from 10 healthy volunteers (4 male and 6 female), with a mean age of 32.2 years. Images taken using a 3.0 T MRI device, manufactured by Philips, were processed using the PRIDE software (Philips, Inc.) and analyzed using Image J, a specialized analysis software. Evaluations were performed using slices in the coronal plane from the trochlear ridge of the talus and slices 10 mm anterior and posterior of the ridge. Each slice was divided into three equal parts including the medial, central, and lateral areas of cartilage on the articular surface of the trochlea tali, to totally yield 9 regions of interests where T1ρ values (ms) were measured. Furthermore, values were measured thrice for each region in each volunteer, and the mean was calculated. Results: T1ρ values for the medial, central, and lateral regions were 31.0 ± 6.4 ms, 31.2 ±7 .2 ms, and 32.2 ± 6.9 ms, respectively for the anterior talus; 24.2 ± 4.2 ms, 21.7 ± 5.6 ms, and 25.1 ± 5.5 ms, respectively for the trochlear ridge of the talus; and 33.8 ± 4.8 ms, 31.9 ± 4.5 ms, and 35.1 ± 4.8 ms, respectively for the posterior talus. T1ρ values were significantly lower in the anterior and posterior areas of the talar dome than in the trochlear ridge of the talus (p < 0.05). Conclusion: Proteoglycan content of articular cartilage in the talar dome was determined to be low in the anterior and posterior areas, that reveals load application might be concentrate on these areas.

A New Surgical Method for the End-Stage Ankle Arthritis–Total Ankle Arthroplasty with Artificial Talus

Category: Ankle Arthritis Introduction/Purpose: Total ankle arthroplasty (TAA) is a popular surgical treatment for the patients with end-stage ankle arthritis. Along with development of the implant, indication for TAA has been extended to the severe deformity due to osteoarthritis or rheumatoid arthritis. However, a certain rate of complication after TAA is still remaining. The main reasons for failed TAA are the complications of talar component such as aseptic loosening or subsidence. We developed artificial talar prosthesis and indicated for the patient with idiopathic necrosis of the talus. This time we applied this new implant combined with tibial component of the TAA for the patient with end-stage ankle arthritis having severe collapse of the talus. The purpose of this study is to evaluate the outcomes of TAA with artificial talus. Methods: 【Materials】Thirteen patients (13 ankles) treated by TAA with artificial talus since 2007 to 2014 were investigated. The mean duration of follow-up was 35 months (range; 12 to 66 months). Twelve patients (12 ankles) were suffering from osteoarthritis of the ankle, and 1 was from rheumatoid arthritis. The mean age at the surgery was 71 year-old(range; 61 to 81 year-old). 【Methods】Clinical outcomes were evaluated by Visual Analog Scale (VAS) scores. Functional outcomes were assessed by scoring system produced by the Japanese Society for Surgery of the Foot (JSSF ankle-hindfoot scale) before surgery and at the final follow- up. Results: Postoperative VAS was improved from 8.9 to 2.3. Postoperative JSSF scale were improved from 41 to 87. There were no case that required the revision surgery due to implant failure or deep infection. Conclusion: The ankle has small joint surface compared with other weight-bearing joints, that causes the complications of talar component. For the patients with severe deformity or osteonecrosis of the talus, indications of TAA should be applied carefully. Patients of end-stage ankle arthritis with poor bone stock in the talus may have been unsatisfied with use of previous implant models of TAA. The artificial talus could be a possible option to solve this problem. In the current study, TAA with artificial talus remained favorable clinical and functional results for the patient with severe deformity or poor bone stock in the talus.