Introduction

Positive expectations can increase compliance with treatment and realistic expectations may reduce postoperative dissatisfaction. Recently there are articles regarding expectations of patients from their TKA in western literature and only few articles based on Korean populations which don't encompass the whole spectrum of expectations in Korean patients. In all those articles based on pre-operative expectation, results were applied to whole expectation category uniformly not differentially. We aimed to document the pre-operative expectations in Korean patients undergoing total knee replacement using an established survey form and to determine whether expectations were influenced by socio-demographic factors and socio-demographic factors influences expectation items in particular category uniformly or differentially.

Introduction

Unicompartmental knee arthroplasty (UKA) is becoming an increasingly popular option in single compartment osteoarthritis. As a result, diverse re-operations including revisions to total knee arthroplasty (TKA) has also increase. The objective of this study is to investigate the distribution of causes of re-operations after UKA and to analyze the types of re-operations.

Introduction

Many literatures regarding more specific tests to diagnose the supraspinatus tendon injuries and the best rehabilitation methods to strengthen the supraspinatus have been published. However, conflicting results have been reported. 2-deoxy-2-[18F] fluoro-D-glucose (FDG) positron emission tomography (PET) has been recently used to assess skeletal muscle activities in various fields.

Spontaneous osteonecrosis of the knee (SPONK) usually involves a single condyle or plateau. The medial femoral condyle is most often involved and spontaneous osteonecrosis of medial tibial plateau is a rare condition, representing only 2 % of all necrosis reported in the knee. Therefore, SPONK with both involvement of medial femoral condyle(MFC) and medial tibial plateau(MTP) might be extremely rare. SPONK in each MFC or MTP respectively might be extended into corresponding side of the knee at their advanced final stage, howevere, in that situations, significant degenerative change would accompany and it might be difficult to differentiate final staged SPONK form severe osteoarthritis. To the best of our knowledge, SPONK affecting both medial femoral condyle and medial tibial plateau without significant secondary osteoarthritis changes is not reported, even though it was difficult to know which occurred first. We experienced 3 patients with histologically proven osteonecrosis of the medial tibial condyle and medial tibial plateau, and report their radiologic features. All 3 patients showed similar ridiograhic patterns. Medial portion of medial tibial plateau and lateral portion of medial femoral condyle showed longitudinal fracture like-subchondral collapse. Standing anteroposterior radiograph at 30 degree knee flexion showed well fitted features such as “locked” medial condyle. Varus angulation was present. Significant degenerative changes was not shown except for subchondral sclerosis. T1-weighted coronal and Fat suppressed T2-weighted MR images showed subchondral collapse with ill-defined diffuse bone marrow edema changes on both tibial and femoral condyles. At surgical findings, longitudinal track-like groove was shown in both medial femoral condyle and medial tibial plateau. Articular cartilage was denuded and showed glistening surface with bone defect of lateral side of medial femoral condyle and medial side of tibial articular surface. Histological analysis shows necrotic bone, surrounded by an area of fibrovascular granulation tissue on both femoral and tibial sides. Total knee arthoplasty was performed in all 3 patients. As a result of very low prevalence of both involvement of MFC and MTP and limited number of our cases, we could not conclude that radiologic features in our cases are typical radiologic pattern of both involvement. However, based on our cases, we believe that this characteristic radiologic features may considered as one of the possible various radiologic findings of simultaneous involvement in MFC and MTP and allow diagnosis for SPONK with both involvement in MFC and MTP to be facilitated.

The goal of total knee arthroplasty (TKA) is to relieve pain and restore the function of the knee joint. Recently the number of TKA cases in Korea has increased considerably with increase in elderly population and change in life style. Accordingly, demand for TKA design that is capable of better accommodating anatomical dimensions and life styles of Koreans is also on the rise. During the prototype design process for the Korean-TKA, different stem and keel designs of the tibial base plate have been attempted to improve fixation and longevity of the implant. In this study, we conducted a biomechanical analysis of the tibial base plate using finite element analysis (FEA). Specifically, biomechanical effects of insert positioning in the tibia were assessed to investigate the likelihood of tibial fracture and implant loosening due to mal-positioning of the implant.

A 3-D finite element(FE) models of the left femur, patella, and tibia were developed from computed tomography (CT) scan data (a normal Korean male, 27 years of age, 70 kg). 2-D truss elements were chosen to represent ligamentous structures such as lateral & medial collateral ligament, posterior cruciate ligament, patella tendon and patella ligament. Nonlinear elastic materal properties for the soft-tissue structures were also adopted from literatures. The surgical model was then constructed after inserting Korean-TKA prototype in the intact model. Here, the implant was the posterior cruciate ligament retaining type (CR) with the fixed bearing system. To simulate loading on the knee joint in heel strike and toe off positions, 15° and 45° flexions of the femur orientation were simulated under the compressive load of 3.8 and 5.7 times of body weight (BW= 700N), respectively, in a uniform pressure at the horizontal section of the femur. The tibia was assumed to be completely constrained. The surgical position of the tibial insert was varied from the center either to the medial or to the lateral direction by 3-mm. The peak von mises stresses (PVMS) at the stem and the keel regions of the tibial insert were assessed.

With respect to the central positioning the lateral shift of the tibial plate resulted in higher PVMS than the medial. Particularly, increases of 24.5 %, 29.8%, and 28.4% were observed at the stem, the lateral keel, and the medial keel, respectively, due to lateral mal-positioning of the implant. With the medial shift, on the other hand, PVMS increase remained at around 6% level at the stem and the lateral keel. A decrease of 4.5 % was noted at the medial keel region.

In this study, a computational approach was used to evaluate biomechanical effect of tibial plate positioning on the stress distribution within the implant. The lateral mal-positioning showed more stress concentration than the medial. This may be due to the fact that body weight is transmitted more to the lateral portion of the tibia (5.5:4.5) that is smaller and thinner than its counterpart. These results suggest that the lateral deviation of the implant can be more likely cause TKR loosening and tibial fracture.

Arthrodesis is used most commonly as a salvage procedure for failed total knee arthroplasty (TKA). For successful arthrodesis, a stable fusion technique and acceptable limb mechanical alignment are needed. Although the use of intramedullary alignment rods might be helpful in terms of achieving an acceptable limb mechanical axis, fat embolism and intramedullary dissemination of an infection or reactivation of latent infection might occur in failed TKA cases. However, computer-assisted surgery allows precise cuts to be made without breaching medullary cavities. Here, the authors describe a case of knee arthrodesis performed by computer navigation and the Ilizarov method in a patient with a past history of infection. A 45-year-old man visited our hospital with failed total knee arthroplasy. Fortunately, even though infection was treated by debridement with component retention, mild heating was present over the knee, but ESR(erythrocyte sedimentation rate) and CRP(C-reactive protein) were within normal ranges. X-ray showed subsidence of the femoral component and a radiolucent line around the femoral component. Arthrodesis was planned for this patient due to disabling pain, a long-lasting severe functional deficit, failure of the primary TKA for ankylosed knee, and the patient’s poor economic status and his strong desire for arthrodesis. The computer navigation surgery system and the Ilizarov method were used for two reasons. The first reason was that the patient had a past history of infection. At pre-operative evaluation, even though ESR and CRP levels were within normal range, we could not completely rule out the possibility of latent infection due to suspicious findings such as long lasting disabling knee pain, mild heating over the knee, severe osteolytic radiographic changes around the femoral component. In that situation, inserting an IM rod to achieve acceptable mechanical alignment might have reactivated and disseminated a possible latent infection to the femoral or tibial medullary canals. The second reason was that we wanted to reduce the possibility of fat embolism by using computer navigation without instrumentation within the medullary canal. A CT-free, wireless computer navigation system was applied, with trackers fixed to the femur and tibia and no requirement for the use of an IM rod with component retention. Navigated femoral and tibial bone resections were then performed using Stryker software. The femoral resection was conducted at 0° of flexion to the sagittal axis, and the tibial resection at 7 ° of flexion to the sagittal axis. Arthrodesis was held in proper axial and rotational alignment with bone surfaces compressed together. Finally, knee arthrodesis was completed using the Ilizarov method. Based on our experience of the described case, we believe that arthrodesis for failed TKR, especially failure secondary to intraarticular infection, can be considered as another indication for computer navigation.