Introduction

The low-contact stress (LCS) knee prosthesis is a mobile-bearing design with modifications to the tibial component that allow for meniscal-bearing (MB) or rotating-platform (RP). The MB design had nonconstrained anteroposterior and rotational movement, and the RP design has only nonconstrained rotational movement. The anterior soft tissues, including patellar tendon (PT), prevent anterior dislocation of the MB. The PT may consistently be exposed to overstressing. Therefore, we hypothesized that the PT thickness and width in MB prosthesis revealed more morphological changes than those of RP prosthesis due to degeneration of the PT induced by much mechanical stress of the MB movement. To confirm this hypothesis, we analyze the PT thickness and width induced by mobile-bearing inserts.

The purpose of this study is to analyze what kind of pattern of change in each posterior femoral condyle allows for a greater degree of flexion after total knee arthroplasty (TKA). The flexion angle was assessed pre-operatively, and at 12 months after the surgery in 98 patients (106 knees) who underwent consecutive TKA. We used a quantitative 3 dimensional technique using computed tomography for the assessment of changes in both the medial and lateral femoral condylar offset. There were no significant correlation between changes of each posterior condylar offset and post flexion angle (medial condyle; R=−0.038, p=0.70, lateral condyle; R=−0.090, p=0.36). There were no significant differences between changing patterns and increase rate of flexion (p=0.443). Additionally there were no significant differences between changing patterns and increase of flexion angle (p=0.593). Changes of each posterior condylar offset were no correlation to knee flexion after TKA in the current design prosthesis.

Introduction: Preoperative planning is an important part of the total knee arthroplasty(TKA) surgical procedure.

In joint arthroplasty, the use of a templating system has been recommended and it is routinely used with most designs. The aim of this study was to compare the accuracy of preoperative templating in TKA between conventional two-dimensional (2D) and computed tomography (CT)-based 3D procedures in order to confirm the necessity of using 3D evaluations for preoperative planning.

Method: One-hundred consecutive primary TKAs performed during the period between December 2005 and May 2009 were analyzed. The mean age of the patients was 73.3 years (range, 33 to 90 years). Preoperative templating was performed for each TKA using both conventional 2D radiographs (both anteroposterior and lateral views) which were analyzed by a single senior surgeon. Preoperative CT scans of the knee were performed and a CT-based 3D image model (superimposing the computer aided design model of the implant) was generated using KneeCAS (KneeCAS: Knee Computer-Assisted System) and then was analyzed by a radiology technologist without any knowledge of the 2D procedure. Based on the operation notes, we determined which size implant had been inserted at the time of surgery and used this as the gold standard. The accuracy and reliability were assessed for all measurements of the two different templating procedures (2D and CT-based 3D procedures)

The Chi-square test for independence for paired observations was used to analyze the accuracy. The weighted kappa test was used to analyze reliability.

Results: 56% of the 2D procedures were found to be an exact match. This increased to 98% for the template sizes within one size above or below that used and 2% were two sizes or more adrift. Otherwise, 59% of the CT-based 3D procedures were an exact match; 98% were within one size and 2% were two sizes or more adrift. The CT-based 3D procedure was slightly more accurate than the 2D procedure. However, the difference was not statistically significant (p = 0.67). The weighted kappa coefficient of the 2D procedure was 0.49 (which indicates a moderate agreement), while that of the CT-based 3D procedure was 0.49 (which indicates a moderate agreement). The results of the weighted kappa coefficients were not statistically significant (p = 0.65).

Conclusion: Computer-assisted surgery systems are used often for preoperative planning in TKA. However, our results do not support the superiority of 3D preoperative templating to 2D conventional evaluation in predicting implant size. Thus, 3D templating may not be necessary for preoperative planning in TKA.

Introduction: We performed a randomized, prospective, stress arthrometric study on 60 knees in 60 patients who had received mobile-bearing prostheses to determine the changes in varus–valgus laxity with time using a Telos arthrometer, and to evaluate the relationship between laxity and retention of the posterior cruciate ligament (PCL).

Materials and Methods: Thirty patients received PCL-retaining (PCLR) prostheses with an average of 75 months of follow-up (range: 60–106 months). Another 30 patients received PCL-sacrificing (PCLS) prostheses with an average of 78 months of follow-up (range: 60–109 months). In all patients, the preoperative diagnosis was osteoarthritis. The coronal conformity of the PCLR and PCLS designs was similar. All of the total knee arthroplasty (TKA) procedures were judged to be clinically successful (Hospital for Special Surgery scores: PCLR 92 ±4 points, PCLS 92 ±3 points). The patients had no clinical complications. Varus–valgus laxity was measured with the knee in extension six months, one year, two years, and five years after surgery. The intrasubject error was less than 1°.

Results: Varus laxity measurements with the PCLR prosthesis at six months, one year, two years, and five years were 3.7°, 4.0°, 4.1°, and 4.2°, respectively. With valgus laxity, measurements at the same time periods were 3.5°, 3.5°, 3.5°, and 3.6°, respectively. Varus laxity measurements with the PCLS prosthesis at six months, one year, two years, and five years were 4.3°, 4.3°, 4.3°, and 4.4°, respectively. With valgus laxity, measurements at the same time periods were 3.7°, 3.4°, 3.5°, and 3.6°, respectively. There were no significant differences in varus and valgus laxity between the PCLR and PCLS groups using repeated measure ANOVA methods (p > 0.05).

Discussion: Coronal laxity did not change with time in patients who had good clinical results. There were no significant differences between the PCLR and PCLS groups in changes in the varus-valgus laxity for a long time after the patients received prostheses. Therefore, we conclude that the PCL doesn’t affect coronal stability in extension, and that the characteristics of the component geometry may act as a resistance factor. Our results suggest that surgeons should appreciate the importance of obtaining balanced coronal laxity for long-term success following mobile-bearing TKA.

Introduction: This study prospectively measured fifty consecutive patients who had the preoperative diagnosis of osteoarthritis undergoing total knee arthroplasty (TKA) to evaluate the change of the bone mineral density (BMD) of the calcaneus.

Materials & Methods: Broadband ultrasound attenuation through the calcaneus was measured to assess the BMD of patients. The BMD was measured preoperatively and 1 month (M), 3M, 6M, 1 year, and 2 years after TKA.

Results: The mean BUA at each stage was 47.1, 45.8, 46.7, 46.7, 47.8 and 53.1, respectively. During the first 6 months, the BUA declined inconsistently in most patients, but by 1 year, the BUA recovered to the initial BUA before surgery and by 2 years, the BUA increased than the initial BUA, although there ware not satisfactory different. Despite a predicted age-related loss of 4% during 2 years, 78% of the calcaneus on the operative side had BMD higher than preoperative levels and 85% had BMD that was within the expected 4% age-related loss.

Discussion: These results indicated that TKA might contribute to decrease the age-related BMD loss. The increase with TKA in patient mobility and the increased heel loading may be a mechanism whereby the calcaneus BMD increases.

Conclusion: It is very important for surgeons to recognize the objection beneficial effects of TKA in addition to pain relief.

This study reports the comparison of the clinical use of a new tourniquet system for total knee arthroplasty that can determine its pressure in synchrony with systolic blood pressure (SBP) with the conventional that keeps the initial setting pressure. We prospectively applied the additional pressure of 100 mmHg based on the SBP recorded prior to skin incision to consecutive 72 procedures (conventional; initial 36, new; following 36). Six knees with the conventional and none of 5 with the new showed oozing blood in surgical field after sharp rise in SBP. According to statistically no difference of the perioperative blood loss without any tourniquet-related postoperative complications in both groups, the new system seemed to be much practical device especially for controlling a bloodless surgical field.

A randomized, prospective stress arthrometric study was done on 60 knees in 60 patients, using a Telos arthrometer to determine the changes of varus-valgus laxity with time and to evaluate the relationship between laxity and retention of posterior cruciate ligament (PCL) using mobile bearing prostheses.

Thirty knees had PCL -retaining (PCLR) with an average 75 months follow-up (range; 60–106 months) and 30 had PCL-sacrificing (PCLS) prostheses with an average 78 months (range; 60–109 months). In all patients, the preoperative diagnosis was osteoarthritis. The coronal conformity of the PCLR and PCLS designs was similar. All of the TKA procedures were judged clinically successful (Hospital for Special Surgery scores: PCLR 92 ±4 points, PCLS 92 ±3 points). The patients had no clinical complications. Varus-valgus laxity was measured with the knee in extension at 6 months, 1 year, 2 year and 5 year after surgery. The intrasubject error was less than 1 degree.

Laxity with PCLR at 6 months, 1, 2 and 5 years was 3.7, 4.0, 4.1, 4.2 degrees with varus, 3.5, 3.5, 3.5, 3.6 degrees with valgus laxity. Laxity with PCLS was 4.3, 4.3, 4.3, 4.4 degrees with varus, 3.7, 3.4, 3.5, 3.6 degrees with valgus laxity. The changes of the varus and valgus laxity had no significant differences in both PCLR and PCLS groups using a repeated measure ANOVA methods (p> 0.05).

The coronal laxity has proved to be no changes with time for the patients who have clinical good results. The changes of the varus-valgus laxity for long timehad no significant differences in both PCLR and PCLS groups. Therefore, we conclude that the PCL doesn’t affect coronal stability in Extension and that the characteristics of the component geometry may act as a resistance factor. We surgeons should have a new understanding of the importance to obtain the balanced coronal laxity for successful mobile-bearing TKA for long period.