Chronic lateral ankle instability (CLAI) is treated operatively, whereas acute ligament injury is usually treated nonoperatively. Such treatments have been widely validated. Apoptosis is known to cause ligament degeneration; however, few reports have focused on the possible role of apoptosis in degeneration of ruptured lateral ankle ligaments. The aim of our study is to elucidate the apoptosis that occurs within anterior talofibular ligament (ATFL) to further validate current CLAI treatments by adducing molecular and cellular evidence.

Between March 2019 and February 2021, 50 patients were prospectively enrolled in this study. Ruptured ATFL tissues were collected from 21 CLAI patients (group C) and 17 acute ankle fracture patients (group A). Apoptotic cells were counted using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Western blotting for caspases 3, 7, 8, and 9 and cytochrome c, was performed to explore intrinsic and extrinsic apoptotic pathways. Immunohistochemistry was used to detect caspases 3, 7, 8, and 9 and cytochrome c, in ligament vessel endothelial cells.

More apoptotic cells were observed in group C than group A in TUNEL assay. Western blotting revealed that the apoptotic activities of group C ligaments were significantly higher than those of group A (all p < 0.001). Immunohistochemistry revealed increased expression of caspases 3, 7, 8, and 9, and cytochrome c, in group C compared to group A.

The ATFL apoptotic activities of CLAI patients were significantly higher than those of acute ankle fracture patients, as revealed biochemically and histologically. Our data further validate current CLAI treatments from a molecular and cellular perspective. Efforts should be made to reverse or prevent ATFL apoptosis in CLAI patients.

Purpose

To evaluate the effectiveness of post-operative pain management using the intra-operative peri-articular injection(PAI) and/or electromyography (EMG)-guided preoperative femoral nerve block (FNB) in total knee arthroplasty(TKA).

Purpose

To measure the vitamin D level of the patients who received total knee arthroplasty (TKA) and evaluate the effect of vitamin D level on the results of TKA.

Purpose

The NexGen® legacy posterior stabilized (LPS)-Flex total knee system (Zimmer, Warsaw, IN) is designed to provide 150° of flexion following total knee arthroplasty (TKA). But, recent reports found a high incidence of loosening of the femoral component related to the deep flexion provided. We evaluated 9- to 12-year clinical and radiological follow-up results after NexGen® LPS-Flex TKA.

Purpose

The purpose of this study was to compare the clinical and radiological results after total knee arthroplasty(TKA) with PCL sacrificing (PCS) Medial Pivot Knee (MPK) and PCL Substituting (PS) Nexgen® LPS.

The purpose of this double-blinded prospective study was to evaluate the effectiveness of electromyography (EMG)-guided preoperative femoral nerve block (FNB) for postoperative analgesia in total knee arthroplasty (TKA).

Forty knees of primary TKA by one surgeon were included in our study. One doctor performed a single injection FNB with an EMG guide in EMG group (23 knees) and with a blind maneuver in control group (17 knees). The same 10ml of 0.375% ropivacaine was injected in both groups. Same postoperative rehabilitation protocol was applied to all patients. Continuous passive motion was started at postoperative 1st day and weight bearing was started as soon as possible.

Intravenous patient-controlled analgesics which contained 30mg of morphine were used until postoperative 72 hours and no additional intravenous, intramuscular or oral analgesics were used. Pain was evaluated by Visual Analogue Scale (VAS) and Postoperative Pain Score (PPS) at postoperative 4, 24, 48 and 72 hours. The amount of opioid consumption and complication were compared between two groups. VAS score was 6.8 in EMG group and 8.0 in control group at postoperative 4 hours, 6.2 and 7.1 at postoperative 24 hours, 5.3 and 5.9 at postoperative 48 hours, and 4.6 and 5.7 at postoperative 72 hours, respectively. PPS was 2.2 in EMG group and 2.2 in control group at postoperative 4 hours, 2.1 and 2.1 at postoperative 24 hours, 1.6 and 1.7 at postoperative 48 hours, and 1.4 and 1.6 at postoperative 72 hours, respectively. The amount of opioid consumption was 6.0mg in EMG group and 7.2mg in control group during postoperative 24 hours, 2.7mg and 3.2mg during postoperative 24–48 hours, and 1.7mg and 3.2mg during postoperative 48–72 hours, respectively. There was no complication in either group.

Pain tended to decrease more in EMG group than control group, especially VAS at postoperative 4, 24 and 72 hours (p< 0.05). The demand of opioid was significantly smaller in EMG group during postoperative 24 hours and 48–72 hours (p< 0.05). EMG-guided single FNB before TKA allowed better postoperative pain relief and reduced the demand of pain killer.

The purpose of this prospective study was to investigate the necessity of gender-specific design in total knee arthroplasty (TKA) for Korean women.

One hundred and seventeen women (151 knees) who underwent primary TKA by one surgeon with Nexgen^® LPS (Zimmer, Warsaw, IN) were evaluated. The mean age was 70 (range 52–80) years. The size of the implant was determined by considering anteroposterior (AP) dimension and the amount of posterior condylar resection. Size C was used in 72 knees, size D in 57 and size E in 22. We measured the mediolateral (ML) widths of distal femur at four points (anterior, distal anterior, distal posterior, posterior) intraoperatively after bone cutting, and compared them with the ML widths of the corresponding femoral implants. The ML/AP ratio was calculated in each size group.

The mean ML widths of the distal femur checked at all four points were larger than those of the implants. The ML/AP ratio of the distal femur decreased as the size increased from C to E, especially that of the anterior point. Overhanging occurred in 7 cases (4.6%, size C -2 cases, size D -2 cases, E -3 cases) : Nexgen^® LPS implant was used in 5 cases because there was only minimal antero-lateral overhanging, resulting in no postoperative problem such as pain or limited motion. Gender-specific design was used in only 2 cases (1.3%, size D -1 case, size E -1 case) with trochlear dysplasia due to general overhanging.

In conclusion, gender-specific design of Nexgen^® TKA was rarely necessary in 117 Korean women(151 knees); overhanging occurred in 7 knees (6 women) and gender-specific design was used in only two knees (1.3%) with trochlear dysplasia. Further research is obviously mandatory to assess the necessity of gender-specific design.

We compared the short term follow-up clinical and radiological results after PCL substituting (PS) Medial Pivot Knee and Nexgen^® LPS total knee arthroplasty (TKA).

Seventy knees in 48 patients after TKA with PS ADVANCE^® Medial Pivot Knee (Group I) and sixty seven knees in 45 patients after TKA with Nexgen^® LPS (Group II) were evaluated retrospectively from March 2004 to May 2006. The mean follow up period was 31 months (range: 24–43 months) in group I and 32 month (range: 24–46 months) in group II. All the knees were operated by one surgeon. The evaluations included the preoperative and postoperative range of motion (ROM), Knee society score (KSS), tibiofemoral angle, and postoperative complications.

In group I, ROM increased from preoperative mean flexion contracture of 6.3° and further flexion of 116° to postoperative mean flexion contracture 1.9° and further flexion 121°, KS knee score increased from 46 to 87, KS function score increased from 37 to 83, and tibiofemoral angle changed from preoperative varus 4.0° to postoperative valgus 5.5°. In group II, ROM increased from preoperative mean flexion contracture of 13° and further flexion of 118° to postoperative mean flexion contracture 0.9° and further flexion 123°, KS knee score increased from 50 to 87, KS function score increased from 48 to 83, and tibiofemoral angle changed from preoperative varus 4.1° to postoperative valgus 5.3°. The complications were two periprosthetic patellar fracture and one failure of tibial component in group I, and one early failure of femoral component and one arthrofibrosis in group II. There was no statistical difference in radiological and clinical results between the two groups.

Minimum 2-year follow-up result of PS Medial Pivot Knee TKA was comparable to that of Nexgen^® LPS TKA and longer term follow-up would be necessary.

We evaluated the minimum 3 year follow-up clinical and radiological results after Nexgen^® LPS-flex total knee arthroplasty (TKA).

Two hundred eighteen knees in 166 patients, who could be followed up more than 3 years after Nexgen^® LPS-flex TKA from October 2001 to February 2005, were evaluated retrospectively. The average age was 64.2 years. Twenty-two patients were male and 144 patients were female. The mean follow-up period was 51 months (range 36–73 months). The evaluations included the preoperative and postoperative range of motion (ROM), Knee Society (KS) Score, tibiofemoral angle and postoperative complications.

The ROM increased from preoperative mean flexion contracture of 8.7° and further flexion of 117.3° to postoperative mean flexion contracture of 1.8° and further flexion of 131.3°. The KS knee score and function score improved from 52 and 38 before surgery to 87 and 82 after surgery, respectively. The tibiofemoral angle changed from preoperative varus 5.7° to postoperative valgus 5.4°. The complications were 30 knees (13.8%, 27 patients) of early loosening of the femoral component on X-ray, 2 instabilities, 2 periprosthetic fractures and 1 failure of extensor mechanism. Early loosening (30 knees) was found at mean 24 months after operation. Among these cases, 23 knees were able to squat, 5 knees to flex over 130°, 1 knee upto 115° and 1 knee upto 95°. Seven knees (3.2%, 6 patients) were revised at mean 49 months after index operation.

The results after Nexgen^® LPS-flex TKA were satisfactory in terms of ROM, but relatively high incidence of early loosening of the femoral components occurred, which might be associated with passive-maximal flexion activity, such as squatting or kneeling.

Only limited data exists concerning outcomes after total knee arthroplasty (TKA) using a surgical robot. We conducted this study to evaluate the clinical and radiographical results in robotic-assisted implantation of TKAs with a minimum follow-up of two years.

A total of 50 primary TKAs using ROBODOC were included in this study. The mean duration of follow-up was 28.3 months. The radiographic measurement with regard to the change of mechanical axis, and the inclination of the femoral and tibial components were assessed. The value within ± 3° of optimum was classified to be “acceptable”, and the value exceeding more than ± 3° to be “outlier” results. Also we evaluated clinical results with the range of motion (ROM), Hospital for Special Surgery (HSS) scores, and Western Ontario and McMaster University (WOMAC) scores.

The mechanical axis was changed from 6.57 varus to 0.81 valgus. Mean coronal inclination of the femoral and tibial component were 88.61 and 89.76 at the last follow up. Also, mean sagittal inclination of the femoral and tibial component were 0.82 and 85.49. On the other hand, all prostheses had no radiolucent lines. On the clinical assessment, the range of motion improved from 124.9 to 128.4, and the improvement of HSS score and Womac score were 70.06 to 95.72 and 65.64 to 28.92 in each. No major adverse events related to the use of the robotic system have been observed. However, one case of the formation of seroma around the pin track and two cases of the partial abrasion of patellar tendon occurred in relation to procedures.

A surgical robot system in TKAs provides good clinical and radiographical results at least 2 years follow-up, however further study for the long term follow-up may be needed. A clear advantage of robot-assisted TKA seems to be ability to execute a highly precise preoperative planning and intraoperaive procedures. But current disadvantages such as increased operating times and inability of adjusting the preoperative planning during the procedure have to be resolved in the future.

Navigation was used to achieve a balanced flexion-extension gap for total knee arthroplasty and it’s 3 years clinical results were reported.

From 112 osteoarthritic knees with varus deformity the flexion and extension gap were measured with distraction of 50 lb/inch using special torque wrench following completion of controlled medial release with guidance of navigation system & tibial bone cut. Distal & AP femoral bony cut were finished according to the data of measurement of flexion-extension gap. After confirmation of the balanced flexion-extension gap by navigation total knee arthroplasty was completed.

The differences between flexion and extension gap varied from case to case, and could be classified into 3 kinds; balanced, tight flexion gap and tight extension gap.

HSS score was 96.7, ROM was 128.5 degree. 39 patients (35%) can have comfortable kneeling 75 patients(67%) can sit with cross leg. Gap technique with navigation could provide excellent clinical results of total knee arthroplasty and 3 classifications of flexion and extension gap should be taken into considerations for balanced total knee arthroplasty

Long term successful results of high tibial osteotomy (HTO) strongly depend on the degree of correction, and inadequate intraoperative measurements of the leg axis can lead to under or over correction, and surgeons have to solve these problems based on personal experience.

This study was undertaken to investigate and compare the clinical and radiological results of navigation assisted open wedge high tibial osteotomy (HTO) versus conventional HTO at 12 months after surgery, for unicompartmental gonarthrosis.

Forty navigated open HTOs with an anterior opening gap of approximately 70% of the posterior gap were included and compared with forty open HTOs performed using the conventional cable technique in terms of intraoperative leg axis assess.

Navigated HTOs corrected mechanical axes to 2.9° valgus (range 0.5–6.2) with few outliers (12.5%), and maintained posterior slopes (7.9±2.3° preoperatively and 8.3±2.8° postoperatively) (P> 0.05). However, in the conventional group, only 63% of cases were within the satisfactory range (valgus 2–5°), and tendencies toward undercorrection and an increase in posterior slope were observed. Clinically both groups showed satisfactory results.

Navigated HTO significantly improved the accuracy of postoperative mechanical axis and decreased correction variabilities with fewer outliers.

The navigation system recently introduced in an ACL reconstruction is reported that it would be helpful for determining the accurate tunnel position and better clinical results in. It also provides intra-operative information such as knee kinematics and anteroposterior translation and internal-external rotation of the tibia during the reconstruction. Our hypothesis was that a double bundle reconstruction would provide better anteroposterior and rotational stabilities than a single bundle reconstruction.

The aim of this study was to assess the changes of anteroposterior and rotational stabilities using a navigation system achieved by double bundle reconstruction (20 knees) and compare them with those by single bundle reconstruction (20 knees).

After registering the reference points, anteroposterior ad rotational stability test with 30° knee flexion using a navigation system was carried out and measured before and after reconstruction on both groups.

The anteroposterior stability showed significant improvement from 17.5 mm before the reconstruction to 5.1 mm after the reconstruction in the double bundle group and from 16.6 mm to 6.1 mm in the single bundle group, showing a significant inter-group differences (p< .05). The mean rotation stability of the double bundle group showed more significant improvement after reconstruction than those of the single bundle group (9.8° in single and 6.1° in double bundle group, p< .05).

The double bundle ACL reconstruction tends to be more stable in rotational stability than the single bundle reconstruction, but not so much in anteroposterior stability. Clinically the double bundle ACL reconstruction may provide better rotational stability reducing residual pivot shift phenomenon after reconstruction.

Unexpected findings were sometimes observed such as hyper extension, oversize of femoral component, or anterior notching of anterior femoral cortex in total knee arthroplasty (TKA) using computer system. We conducted this study to evaluate these findings by a virtual simulation using ORTHODOC and then confirmed them on real patients with TKA.

Virtual simulations of distal femoral cut in 50 patients using ORTHODOC system were made by way of being perpendicular to mechanical axis (CAOS way) and to intramedullary guide (manual way) in the same knee and measured the difference of sagittal cutting planes. We compared the maximum AP dimensions of femoral condyle parallel to distal cut plane. We also compared sagittal alignment and size of the femoral component in 30 bilateral TKAs, one side using ROBODOC (CAOS way) and the other side using IM guide (manual way).

On virtual simulation, distal femoral cut was more extended (3.1±1.6°) in CAOS than in manual way and anteroposterior size of the femoral condyle in CAOS way was also larger than in manual way (p=0.001). Radiographic sagittal alignment of femoral component performed using CAOS way was slightly more extended than those using manual way, showing a significant difference (p=0.024). The larger femoral components were required in six patients on CAOS and in two patients on manual way, whereas twenty-two patients showed same size on both side.

CAOS can provide more accurate sagittal cut perpendicular to mechanical axis than manual system, which may lead to slightly extended position or larger femoral component.

In total knee arthroplasty, navigation systems that help achieve accurate alignment of the lower limbs have been applied widely, and these techniques are currently being used in minimally invasive unicondylar knee arthroplasty (MIS UKA) with good alignment results. To the best of our knowledge, there are no studies showing whether or not MIS UKA using a navigation system has a significant influence on the clinical results. This prospective study investigated the hypothesis that minimally invasive uni-compartmental knee arthroplasty using navigation system (NA-MIS UKA) will produce better short-term clinical results than MIS UKA without navigation system.

After a minimum two-year follow-up, the short-term functional results included the ranges of motion, Hospital for Special Surgery (HSS) scores, and WOMAC scores and the alignment accuracy of the components of 31 NA-MIS UKAs (NA-MIS group) compared with those of 33 MIS UKAs without a navigation system (MIS group). The surgery time was also recorded and compared.

The HSS and WOMAC scores showed significant improvement at the final follow-up in both groups, showing no significant inter-group difference (p=0.071, p=0.096, respectively). The ranges of motion also showed significant improvements in both groups, but there was no significant difference between two groups (p=.687). However, the surgery time was longer in MIS group than in NA-MIS group. NA-MIS UKA produces significant improvement in the desired mechanical axis with prosthetic alignment outliers compared with that without the navigation system.

However, at the final follow-up, there were no significant differences in any of the functional parameters between the two groups.

This prospective study was undertaken to compare the clinical and radiological results achieved using navigation assisted minimally invasive (NA-MIS) and conventional (CON) techniques in bilateral total knee arthroplasty (TKA).

Forty-two bilateral patients with a minimum 2-year follow-up who were available for study after NA-MIS TKA were included in this study. Clinical evaluations (ROM, HSS and WOMAC scores) were performed at 3 and 6 months and at 1 & 2 year postoperatively. Patient subjective preferences and radiological accuracies were compared at 1 year postoperatively.

Preoperative HSS scores were 68.5 in the NA-MIS group and 66.5 in the CON group, and these scores improved to 93.6 and 92.5 at 1 year postoperatively, respectively. Knees had a higher average HSS score in NA-MIS group than in the CON group till six months, but not after nine months postoperatively. In terms of WOMAC scores, pain scores in the NA-MIS group were better up to nine months postoperatively, but not at one & 2 year postoperatively, and total WOMAC scores were better up to six months, but not after nine months postoperatively. ROM was comparable in both groups at all times. However, more patients preferred NA-MIS sides than CON sides. Radiological results demonstrated no difference between the mean values of the two groups, although the NA-MIS group contained fewer outliers than the CON group.

NA-MIS TKA results in better functional scores than CON-TKA over the first or nine months postoperatively. However, no differences in any functional parameters were evident at one & two year postoperatively.

Computer based navigation system improved the accuracy of limb and component alignment and decreased the incidence of outliers. The majority of previous studies were based on the infrared navigation system. We evaluate the availability and accuracy of the electromagnectic(EM) navigation system in total knee arthroplasty

From July 2006 to January 2007, 40 patients (50 TKAs) with osteoarthritis were participated in this study. AxiEM(Medtronics) was used and Nexgen CR(26 cases), and Nexgen CR flex(24 cases) were used. We analyzed the failure mode of navigation (7 cases), operation time and radiologic results (limb and component alignment)

Total registration time was 4 minutes 45 seconds in average (Range : 3 minutes 45 seconds ~ 6 minutes 55 seconds). Failures in clinical applications resulted from non-recognition of EM tracker or paddle by metallic interference in 4 cases and from informational changes during surgery by fixation loss or loosening of the tracker in 3 cases. Radiologically, the mechanical axis changed from −11.2±7.21 (Range : −25.8~3.1) to 1.0±1.25(Range : −2.1~4.0) and 1 case of outlier occurred (valgus 4°). Component alignment is measured as followed: 89.3±1.6° of Theta angle, 89.9±1.5° of Beta angle, 1.8±2.5° of Gamma angle, 86.1±2.9 of Delta angle°. There were no complications related to the EM navigation.

The EM navigation system helped to achieve accurate alignment of component and lower leg axis without any complications. It had several advantages such as relatively less invasiveness in fitting small instruments, not disturbing operation field, no interrupted line of sight, portable use, and applicability to any implant. However, metallic interference may be still problematic.

The EM navigation had advantages; less invasiveness, no disturbing operation field, no interrupted line of sight, portable use and applicability to any implants. But metallic interference may be still problematic.

Correct alignment of the leg and positioning of the implant has shown to be an important factor in the successful long term outcome of total knee arthroplasty and navigation systems enable an accuracy of corrections and alignment within intervals of 1 mm or 1 degree. This study is to test if there is any discrepancy in accuracy which was sometimes observed in clinical trials between Orthopilot (Aesculap, Tuttlingen, German) and AxiEM (Medtronic Navigation, CoalCreek, Colo., USA).

A synthetic bone model (Sawbones, Pacific Laboratories, Vashon, Washington) including pelvis and leg with mobile joint made up of titanium which does not affect the electromagnetic field was constructed. Mechanical axis was checked by ORTHODOC system (Integrated Surgical System, CA, USA) that is a preplanning system for ROBODOC (ISS, CA, USA) assisted total knee arthroplasty (TKA) and total hip arthroplasty (THA). The CT images were scanned with 1.25 mm or less slice interval. The CT images were converted to 3-dimensional (3D) volume-rendered model in ORTHODOC. Two orthopaedic surgeons measured it ten times independently.

For the measurement of mechanical axis using navigation, 4 orthopaedic surgeons (two experts having more than 100 navigation experiences and two residents) registered anatomical landmarks and kinematic center of bone model ten times using Orthopilot as well as AxiEM. After that, one surgeon intentionally registered the wrong anatomical landmarks (10 mm medial and lateral to the center of distal femur, proximal tibial and ankle, and both malleoli) in both navigation system and observed the change of mechanical axis.

True mechanical axis was varus 1.25° using Orthodoc, Orthopilot displayed varus 1.10±0.64° and AxiEM did varus 1.78±0.79°. The difference of mechanical axis between two navigations was not observed (P=0.12) and there were no intra and inter-observer variation in statistical analysis (Correlation=0.934, P=0.00). In the case of erroneous identification of the anatomical landmarks, Orthipilot showed much less variation compared to AxiEM. AxiEM altered the mechanical axis more in palpating center of the distal femur and ankle center and Orthopilot did in palpating the center of ankle.

Both navigation systems provide high accuracy and reproducibility of mechanical axis of lower limb in experimental condition. But both were affected by the wrong identification of the anatomical landmarks. AxiEM had more variations. So surgeon should pay attention to register the precise anatomical landmarks.

Bilateral sequential total knee replacement with a Zimmer NexGen prosthesis (Zimmer, Warsaw, Indiana) was carried out in 30 patients. One knee was replaced using a robotic-assisted implantation (ROBOT side) and the other conventionally manual implantation (CON side). There were 30 women with a mean age of 67.8 years (50 to 80).

Pre-operative and post-operative scores were obtained for all patients using the Knee Society (KSS) and The Hospital for Special Surgery (HSS) systems. Full-length standing anteroposterior radiographs, including the femoral head and ankle, and lateral and skyline patellar views were taken pre- and post-operatively and were assessed for the mechanical axis and the position of the components. The mean follow-up was 2.3 years (2 to 3).

The operating and tourniquet times were longer in the ROBOT side (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). Mean mechanical axes were not significantly different in the two groups (p = 0.815). However, there were more outliers in the CON side (8) than in the ROBOT side (1) (p = 0.013). In the coronal alignment of the femoral component, the CON side (8) had more outliers than the ROBOT side (1) (p = 0.013) and the CON side (3) also had more outliers than the ROBOT side (0) in the sagittal alignment of the femoral component (p = 0.043). In terms of outliers for coronal and sagittal tibial alignment, the CON side (1 and 4) had more outliers than the ROBOT side (0 and 2).

In this series robotic-assisted total knee replacement resulted in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement.

The aim of study was to provide normal value of anteroposterior and rotational stability of knee joints using navigation system.

From March 2007 to November 2007, 35 patients (23 men, 12 women) with a mean age of 36.1(16–57) years, who were treated with arthroscopy, without ligament injury of knee were included in our study. We measured amount of anteroposterior displacement and rotation of the knee in 0, 30, 60 and 90 degrees of flexion position using Orthopilot navigation system. All tests were performed by same single surgeon under manual maximal force.

The mean anterior displacement was 3.7±2.0, 6.6±2.2, 5.8±2.0 and 4.7±1.8 mm in 0, 30, 60 and 90 degrees of flexion respectively. The amount of anterior displacement at 30 degree of flexion was significantly larger than those of other degrees. The mean posterior displacement was 2.0±0.5, 2.2±0.4, 2.1±0.4 and 2.0±0.6 at each degree. There was no statistical difference in posterior displacement. The mean internal rotation was 10.3±2.7, 14.6±3.3, 16.2±2.9 and 15.0±4.3 degree at each degree. The amount of internal rotation at 0 degree of flexion was significantly smaller than those of other degrees. The mean external rotation was 8.4±3.4, 16.5±3.3, 13.3±3.8 and 15.0±4.3 degree at each degree. The amount of external rotation at 0 degree of flexion was significantly smallest and that of 30 degree was largest.

In the measurement of laxity using navigation, we could acquire previously mentioned results. The measurement of stability of knee will be useful in diagnosing ligament injury and evaluating degree of postoperative symptomatic improvement.