Published papers

Background: Achievement of very deep knee flexion after total knee arthroplasty (TKA) can play a critical role in the satisfaction of patients who demand a floor-sitting lifestyle and engage in high-flexion daily activities (e.g., seiza-sitting). Seiza-sitting is characterized by the knees flexed >145º and feet turned sole upwards underneath the buttocks with the tibia internally rotated. The present study investigated factors affecting the achievement of seiza-sitting after TKA using posterior-stabilized total knee prosthesis with high-flex knee design. Methods: Subjects comprised 32 patients who underwent TKA with high-flex knee prosthesis and achieved seiza-sitting (knee flexion >145º) postoperatively. Another 32 patients served as controls who were capable of knee flexion >145º preoperatively, but failed to achieve seiza-sitting postoperatively. Accuracy of femoral and tibial component positions was assessed in terms of deviation from the ideal position using a two-dimensional to three-dimensional matching technique. Accuracies of the component position, posterior condylar offset ratio and intraoperative gap length were compared between the two groups. Results: The proportion of patients with >3º internally rotated tibial component was significantly higher in patients who failed at seiza-sitting (41 %) than among patients who achieved it (13 %, p = 0.021). Comparison of intraoperative gap length between patient groups revealed that gap length at 135º flexion was significantly larger in patients who achieved seiza-sitting (4.2 ± 0.4 mm) than in patients who failed at it (2.7 ± 0.4 mm, p = 0.007). Conversely, no significant differences in gap inclination were seen between the groups. Conclusions: From the perspective of surgical factors, accurate implant positioning, particularly rotational alignment of the tibial component, and maintenance of a sufficient joint gap at 135º flexion appear to represent critical factors for achieving >145º of deep knee flexion after TKA.

Discoid lateral meniscus with snapping phenomenon is a rare pathologic condition. The purpose of this article is to present an arthroscopic technique for the treatment of discoid lateral meniscus with snapping phenomenon. The patient is placed in the supine position for confirmation of snapping. As the patient's knee bends, it can be confirmed by arthroscopy that the posterior horn of the discoid lateral meniscus moves posteriorly and the central portion of the discoid lateral meniscus moves anteriorly at the same time with snapping at deep flexion angles. The anterior segment of the discoid lateral meniscus is found to be redundant and is often folded. On the contrary, as the patient's knee extends, the central portion is returned to the original position accompanied by snapping at nearly full extension. After excision of the central portion, the movement of the meniscus is evaluated again and the disappearance of the snapping phenomenon can be confirmed. Although it includes limitations, this application is easy and would certainly help surgeons to treat snapping knee with discoid lateral meniscus.

Background: To date, the knee kinematics of discoid lateral meniscus (DLM) has not been elucidated. The aim was to investigate the three-dimensional knee kinematics in DLM using gait analysis. Methods: Ten patients (mean: 14. years) diagnosed with bilateral DLM and unilaterally symptomatic snapping as well as 10 healthy controls (mean: 23. years) participated in the study. Each patient with DLM had unilaterally snapping knee in full extension and deep flexion. The three-dimensional gait analysis was performed with the point cluster technique. All subjects were asked to walk on a level floor at the speed of their choice. In the sagittal plane, knee excursion was separately evaluated during the weight acceptance phase and the mid-stance phase. In the axial plane, knee excursion during the stance phase was assessed. Finally, knee excursion during the whole gait cycle was evaluated in the frontal plane. Statistical comparison was conducted between groups, and between both sides in the DLM group. Results: In the sagittal plane, knee excursions during the weight acceptance phase and the mid-stance phase were significantly smaller in the DLM group than in the control group; in addition, these were smaller on the symptomatic side than on the asymptomatic side in the DLM group. In the axial plane, knee excursion was also significantly smaller on the symptomatic side than on the asymptomatic side in the DLM group, whereas the frontal knee motion did not differ significantly. Conclusion: Less knee motion in the sagittal plane may prevent snapping during extension and flexion in patients with DLM. Level of Evidence: III.

Purpose: It was hypothesized that surgical time of beginners would be much longer than that of experts. Our purpose was to investigate and clarify the important manoeuvres for beginners to minimize surgical time in primary total knee arthroplasty (TKA) as a multicentre study.Methods: A total of 300 knees in 248 patients (averaged 74.6 years) were enrolled. All TKAs were done using the same instruments and the same measured resection technique at 14 facilities by 25 orthopaedic surgeons. Surgeons were divided into three surgeon groups (four experts, nine medium-volume surgeons and 12 beginners). The surgical technique was divided into five phases. Detailed surgical time and ratio of the time in each phase to overall surgical time were recorded and compared among the groups in each phase. A total of 62, 119, and 119 TKAs were done by beginners, medium-volume surgeons, and experts, respectively.Results: Significant differences in surgical time among the groups were seen in each phase. Concerning the ratio of the time, experts and medium-volume surgeons seemed cautious in fixation of the permanent component compared to other phases. Interestingly, even in ratio, beginners and medium-volume surgeons took more time in exposure of soft tissue compared to experts. (0.14 in beginners, 0.13 in medium-volume surgeons, 0.11 in experts, P < 0.05).Conclusion: Beginners took more time in exposure and closure of soft tissue compared to experts. Improvement in basic technique is essential to minimize surgical time among beginners. First of all, surgical instructors should teach basic techniques in primary TKA for beginners.Level of evidence: Therapeutic studies, Level IV.

This study aimed to assess the effects of down-sizing and lateralizing of the tibial component (reduction osteotomy) on gap balancing in TKA, and the clinical feasibility of an uncemented modular trabecular metal tibial tray in this technique. Reduction osteotomy was performed for 39 knees of 36 patients with knee OA with a mean tibiofemoral angle of 21° varus. In 20 knees, appropriate gap balance was achieved by release of the deep medial collateral ligament alone. Flexion gap imbalance could be reduced by approximately 1.7° and 2.8° for 4-mm osteotomy and 8-mm osteotomy, respectively. Within the first postoperative year, clinically-stable tibial component subsidence was observed in 9 knees, but it was not progressive, and the clinical results were excellent at a mean follow-up of 3.3years.

Background: Symptomatic knee joint effusion is frequently observed after hip fracture, which may lead to postoperative knee pain during rehabilitation after hip fracture surgery. However, unfortunately, very little has been reported on this phenomenon in the literature. The purpose of the current study was to investigate the relationship between symptomatic knee effusion and postoperative knee pain and to clarify the reason of the effusion accompanied by hip fracture. Methods: A total of 100 patients over 65 years of age with an acute hip fracture after fall were prospectively followed up. Knee effusion was assessed on admission and at the operating room before the surgery. If knee effusion was observed at the time of the surgery, synovial fluid was collected into syringes to investigate the cause of the effusion using a compensated polarized light microscope. Furthermore, for each patient, we evaluated age, sex, radiographic knee osteoarthritis (OA), type of the fracture, laterality, severity of the fracture, and postoperative knee pain during rehabilitation. These factors were compared between patients with and without knee effusion at the time of the surgery. As a statistical analysis, we used Mann-Whitney U-test for patients' age and categorical variables were analyzed by chi-square test or Fisher's exact test. Results: A total of 30 patients presented symptomatic knee effusion at the time of the surgery. In patients with knee effusion, numbers of intertrochanteric fracture, radiographic knee OA, and postoperative knee pain were significantly large compared to those without effusion. In terms of synovial fluid analysis, calcium pyrophosphate dihydrate crystals were observed in 80% of patients with knee effusion. Conclusion: From our study, approximately 63% of patients with knee effusion at the time of the surgery had postoperative knee pain. In addition, this effusion was basically related to pseudogout.

Purpose: The aim of this study was to evaluate weight-bearing distribution in patients with bilateral end-stage knee osteoarthritis (OA) and to clarify the gait parameters affecting the weight-bearing distribution during both standing and walking using gait analysis.Methods: Twenty-five patients (averaged 71 years) with symptomatic bilateral end-stage medial knee OA participated in this study. They performed relaxed standing, placing one foot on a force plate and thereafter, level walking. First, knee resultant force was calculated on bilateral knees during standing. The knees in each patient were divided into Higher and Lower force side for the definition of dominant side limb. Second, gait parameters in each subject were compared between both sides.Results: Each patient had large weight-bearing asymmetry, though passive range of motion, subjective pain level, femorotibial angle and radiographic disease severities were not significantly different between both sides. In standing, knees on Higher force side were significantly extended (11.2 ± 6.5°) than on Lower force side (14.4 ± 7.3°, P = 0.0086). Similarly, knees on Higher force side were also significantly extended at heel strike during gait. Besides, peak values of extension moment, knee adduction moment, knee adduction moment impulse and vertical force during gait were significantly greater on Higher force side.Conclusions: Ability to extend the knee in standing was considered to be an essential factor to decide loading condition. It is clinically important to examine the ability to extend the knee in standing when considering loading asymmetry during gait in patients with bilateral knee OA.Level of evidence: III.

Stress fractures after total knee arthroplasty (TKA) occur mainly in patients with considerable deformity of the knee. In addition, the majority of these fractures after TKA involve the hip joint. We present two cases of stress fractures of the first metatarsal after TKA in patients with severe varus deformity. Correction of leg alignment and pain reduction obtained by TKA lead to stress fracture of the bone. Gait analysis was carried out for both cases in order to clarify the gait characteristics of the stress fracture. As a result, side-to-side differences of the distance between first metatarsal and foot center of pressure in the coronal plane were observed using gait analysis in these patients. Fortunately, conservative treatment was successful for these patients. Stress fractures should be considered when a patient who had a considerable severe deformity of the knee preoperatively complains of foot pain on the affected side. Contrary to stress fractures at the hip joint, patients with the fracture of the first metatarsal can be treated without surgery. © 2012 Elsevier B.V.

Unilateral total knee arthroplasty (TKA) would produce asymmetric changes of lower extremity in patients with bilateral varus deformity. Our purpose was to investigate whether asymmetry of the leg alignment would affect trunk bending in the coronal plane after unilateral TKA. Twenty patients (mean 76. years old) with bilateral end-stage knee osteoarthritis (OA) participated. Spine images during relaxed standing were obtained on pre- and postoperative day 21. As a result, the shoulder tilted more to the TKA side and the pelvis inclined more to the contralateral OA side. These results suggested that the trunk would bend away from the contralateral OA side after unilateral TKA in patients with bilateral end-stage knee OA and varus deformity. Asymmetry of the leg alignment led to asymmetric trunk bending. © 2013 Elsevier Inc.

Extraneural pressure in the cubital tunnel is considered to be a major pathophysiological factor for cubital tunnel syndrome. Thus, it has been hypothesised that the higher extraneural pressure in the cubital tunnel should result in a more severe stage of cubital tunnel syndrome. Extraneural pressures in cubital tunnel at elbow maximum flexion of 41 patients with cubital tunnel syndrome were evaluated, and compared with their preoperative disease severity using McGowan's classification and Dellon's staging. Mean extraneural pressure was significantly higher in maximum elbow flexion than in maximum elbow extension (p < 0.001). However, no significant relation was seen between the severity of cubital tunnel syndrome and the extraneural pressure induced by maximum elbow flexion (McGowan's classification: p = 0.62; Dellon's staging: p = 0.92). The results suggested that the progression of disease severity of cubital tunnel syndrome may not be explained simply by dynamic pressure in the cubital tunnel, and other causative factors should also be contributing to the progression. © Informa Healthcare.

Postoperative pseudogout after total knee arthroplasty is rare. If pseudogout attacks are misdiagnosed as periprosthetic sepsis, patients may undergo unnecessary surgical procedures. We report a case of pseudogout in the early postoperative period. The attack ensued shortly after a nonsteroidal antiinflammatory drug was discontinued. The diagnosis was confirmed by aspiration, and the patient improved after readministration of the nonsteroidal antiinflammatory drug. Although rare, pseudogout should be considered in the differential when approaching a suspected infection after total knee arthroplasty. © 2013 Elsevier Inc.

The aim of this study was to evaluate weight-bearing condition after unilateral total knee arthroplasty (TKA) during standing and to examine whether the condition affects knee kinetics during gait in both limbs. Twenty-five patients, who underwent unilateral TKA for symptomatic bilateral osteoarthritis and who were on average 74 years old, participated. As a result, operated limbs became dominant in 80% of the patients. The other 20%, who had lack of knee extension during standing, showed more weight bearing in nonoperated knees. Furthermore, extension limitation in the operated knee in standing led to mechanical overload in the contralateral limb during gait. Therefore, to avoid progression of the osteoarthritis in the contralateral knee, it is important to acquire full extension in the operated knees during standing after unilateral TKA. © 2010 Elsevier Inc. All rights reserved.