Accuracy of a portable lower-limb muscle strength measuring device with a training function.

[Purpose] Quadriceps muscle strength is essential for daily living activities. Therefore, we developed a compact and simple lower limb muscle strength measuring device (LocomoScan [LCS]). This study aimed to compare LCS with other instruments to analyze its simplicity, reproducibility, and accuracy. [Participants and Methods] One hundred and four healthy university students (56 males and 48 females) were included in the study. The knee extension force was measured using LCS, and the knee extension torque was measured using other devices (Cybex). In addition, lower leg muscle mass was measured using a body composition meter. The reproducibility of LCS and the correlation between the knee extension torque and lower leg muscle mass were evaluated. [Results] The measurement reproducibility of LCS was significantly higher. The knee extension force confirmed the proportional relative reliability of Cybex with knee extension torque. A relationship between knee extension force and lower limb muscle mass was also observed, indicating that muscle mass cannot be estimated as muscle strength. [Conclusion] The high reproducibility of the knee extension force measurement using LCS demonstrates its potential as a portable alternative instrument for muscle strength measurement in clinical practice. Therefore, LCS device is a simple and effective tool for assessing muscle strength.

The Matsudai Knee Osteoarthritis Survey showed the longitudinal changes of knee phenotypes in alignment and structure during 23-28 years.

PURPOSE: The longitudinal changes in alignment and structure, including the joint line and cortical bone thickness (CBT) of the femur and tibia, and knee phenotype in patients with knee osteoarthritis (OA) remain unknown. The aim of this retrospective study was to clarify the longitudinal changes in matched healthy subjects. METHODS: The follow-up Matsudai Knee Osteoarthritis Survey was administered between 23 and 28 years. This study included 285 healthy knees from 235 females with an average age of 53 ± 6 years at baseline. The non-OA individuals, with an average age of 79 ± 4 years, were divided into three groups at baseline according to their follow-up radiographic results [the non-OA (n = 52), early OA (n = 131), and advanced OA groups (n = 102)]. Changes in alignment, joint line, CBT, and knee phenotype were assessed at baseline and at follow-up using standing anteroposterior radiographs. RESULTS: This study showed significant varus changes in the alignment (p < 0.001) and tibial and femoral joint line parameters (p < 0.05) in the OA group. Decreased CBT and increased mediolateral CBT ratios were observed in all groups (p < 0.001). The knee phenotypes in the OA groups were changed to varus angles, especially in the alignment and tibial joint line. CONCLUSIONS: The longitudinal changes of knee phenotypes in alignment and structure (CBT and joint line) from baseline to follow-up were shown in the OA groups. In addition, alignment and tibial structural factors at baseline are useful in predicting the incidence of knee OA in daily practice. LEVELS OF EVIDENCE: III.

The medial inclination of the proximal tibia is associated with the external knee adduction moment in advanced varus knee osteoarthritis.

PURPOSE: Whether the inclined articular surface on the medial proximal tibia and the external knee adduction moment (KAM) correlate remains unclear. The hypothesis was that a steeper inclined articular surface correlated with a larger KAM in advanced knee osteoarthritis (OA). METHODS: A total of 44 females (non-OA, 9 knees; early OA, 14 knees; advanced OA, 21 knees; mean age, 58 ± 16 years) were examined. Three-dimensional (3D) assessment was used on biplanar long-leg radiographs and 3D bone models using a 3D to 2D image registration technique. The approximation plane in the proximal tibia was determined using the least-square method. The joint moments were mathematically calculated in a gait analysis, applying a motion capture system and force plates. The main evaluation parameters were the femorotibial angle (FTA), the coronal inclination of the approximation plane in the medial proximal tibia (coronal inclination), and internal knee joint moments. The KAM means the external moments balanced with the internal knee abduction moments. RESULTS: The advanced OA showed a larger internal abduction moment (p = 0.017) at the loading response than the other groups. The larger FTA and steeper coronal inclination correlated with the larger internal abduction moment (FTA, p < 0.001; coronal inclination, p = 0.003) at the loading response. CONCLUSIONS: As the clinical relevance, the association among the coronal inclination of the medial proximal tibia, lower extremity alignment, and KAM is one of the key factors to help better understand the etiology of knee OA. LEVEL OF EVIDENCE: III.

The coronal inclination of the medial tibial plateau affects coronal gait kinematics for varus osteoarthritic knees.

PURPOSE: This study aims to (1) measure the kinematics of lower extremity alignment and the bony position relative to the ground during walking, focusing on the coronal plane, and (2) determine the correlation between the kinematics and coronal inclination of the medial tibial plateau (coronal inclination) for healthy and varus knee osteoarthritis (OA). METHODS: In this study, 43 women (non-OA, 9 knees; early OA, 13 knees; advanced OA, 21 knees; mean age 58 ± 17 years) were examined. The knee phenotypes in varus knee OA were varied. Three-dimensional (3D) knee kinematics were calculated in gait analysis by combining the motion capture system and the 3D lower extremity alignment assessment system via biplanar long-leg X-rays, applying the 3D-2D registration technique. The main parameters were the kinematics of the bony axes relative to the ground in the coronal plane during the stance phase of the gait. The differences in overall kinematics were assessed using repeated measures ANOVA with Tukey's post hoc test. The association between kinematic parameters and coronal inclination was evaluated by multiple linear regression after univariate analysis. RESULTS: The tibia tilted laterally during the loading response, and a plateau area subsequently appeared until the terminal stance phase, whereas the femur slowly tilted laterally until the terminal stance phase. The dynamic alignment showed a relatively large varus angular change during the loading response in all groups. The trend of motion was similar among all groups (p = n.s.), although to varying degrees. The coronal inclination was the more dominant factor than the Kellgren-Lawrence (K-L) grades (ß = - 0.423, p = 0.005) when the change in dynamic alignment was determined. CONCLUSIONS: The TAA plateau area after the loading response implies that the tibial articular surface may become horizontal. The femur slowly tilted laterally until the terminal stance phase in response to the tibial motion. Consequently, the dynamic alignment showed a varus angular change, in which coronal MCT was more involved than K-L grades.

Age- and sex-related characteristics in cortical thickness of femoral diaphysis for young and elderly subjects.

INTRODUCTION: Cortical thickness of the femoral diaphysis is assumed to be a preferred parameter in the assessment of the structural adaptation by mechanical use and biological factors. This study aimed to investigate the age- and sex-specific characteristics in cortical thickness of the femoral diaphysis between young and elderly non-obese people. MATERIALS AND METHODS: This study investigated 34 young subjects (21 men and 13 women; mean age: 27 ± 8 years) and 52 elderly subjects (29 men and 23 women; mean age: 70 ± 6 years). Three-dimensional (3D) cortical thickness of the femoral diaphysis was automatically calculated for 5000-8000 measurement points using the high-resolution cortical thickness measurement from clinical CT data. In 12 assessment regions created by combining three heights (proximal, central, and distal diaphysis) and four areas of the axial plane at 90° (medial, anterior, lateral, and posterior areas) in the femoral coordinate system, the standardized thickness was assessed using the femoral length. RESULTS: As per the trends, (1) there were no differences in medial and lateral thicknesses, while the posterior thickness was greater than the anterior thickness, (2) the thickness in men was higher than that in women, and (3) the thickness in young subjects was higher than that in elderly subjects. CONCLUSIONS: The results of this study are of clinical relevance as reference points to clarify the causes of various pathological conditions for diseases of the lower extremities.

Articular surface of the medial proximal tibia is aligned parallel to the ground in three-dimensional space under weight-bearing conditions in healthy and varus osteoarthritic knees.

PURPOSE: To test the hypothesis that an inclined articular surface on the medial proximal tibia is aligned more parallel to the ground in three-dimensional (3D) space under weight-bearing (WB) conditions (parallel phenomenon) than under non-WB (NWB) conditions in healthy and varus osteoarthritic knees. METHODS: We examined 55 healthy knees (26 women, 29 men; mean age, 70 ± 6 years) and 108 varus osteoarthritic knees (66 women, 16 men; mean age, 74 ± 7 years). For the evaluation under WB conditions, a 3D assessment system was used on biplanar long-leg radiographs and 3D bone models using a 3D-to-2D image registration technique. In addition, the least square method was used to determine the approximation plane. The angles between the normal vector for the approximation plane of an articular surface on the medial proximal tibia and each axis of the tibial or world coordinate system were calculated. RESULTS: Morphologically, the inclination of the approximation plane was steeper in osteoarthritic knees than in healthy knees (p < 0.0001). The approximation plane was aligned more parallel to the ground under WB conditions than under NWB conditions in healthy (p < 0.0001) and osteoarthritic knees (p < 0.0001). CONCLUSIONS: The parallel phenomenon in the medial proximal tibia was confirmed for healthy and varus osteoarthritic knees. The medial proximal tibia plays an important role in the parallel phenomenon, assumingly associated with varus alignment and varus thrust. The inclination of the medial proximal tibia may become a new parameter for imaging investigations. LEVEL OF EVIDENCE: III.

A comparative study of weight-bearing and non-weight-bearing 3-dimensional lower extremity alignment in knee osteoarthritis.

BACKGROUND: Lower extremity alignment is an important variable with respect to the development and progression of knee osteoarthritis. It is very essential for the preoperative planning of realignment surgeries such as total knee arthroplasty and high tibial osteotomy. Nevertheless, there have been no reports comparing 3D lower extremity alignment between weight-bearing upright and non-weight-bearing horizontal states in osteoarthritic knees in the same subject. Therefore, we determined whether the alignment of the lower extremity in the weight-bearing upright state differed from that in the non-weight-bearing horizontal or supine position in patients with knee osteoarthritis. METHODS: Adduction-abduction, flexion-extension, and rotational angle of osteoarthritic knees were assessed in weight-bearing upright and non-weight-bearing supine positions. Knee alignment in the supine position was determined from preoperative computed tomography data. In the weight-bearing upright state, alignment was determined using a technique that utilized 2D-3D image-matching with biplanar computed radiography and 3D bone models of the complete lower extremity rebuilt using computed tomography-based information. RESULTS: We assessed 81 limbs from osteoarthritic knee patients (74 women, 7 men; mean age 75.3 years, range 59-86 years). In the coronal plane, there were varus deformities in both the supine and standing positions, while there was flexion in both the supine upright state and position at the sagittal plane. In the axial plane, the rotation of the tibia to the femur was neutral in the supine position and internal in the upright state. CONCLUSION: Patient position significantly affects lower extremity alignment in osteoarthritic knees. This study provides important data regarding the preoperative evaluation of realignment surgery in total knee arthroplasty and high tibial osteotomy. We believe that these results are an important contribution to the knowledge regarding knee osteoarthritis.

Quadriceps muscle weakness is related to increased risk of radiographic knee OA but not its progression in both women and men: the Matsudai Knee Osteoarthritis Survey.

PURPOSE: The purpose of this study was to investigate the causal relationship between quadriceps muscle strength and radiographic knee osteoarthritis (OA) in a longitudinal study. METHODS: The present study included 976 knees from 488 subjects who participated in both the 5th (2007) and 7th (2013) surveys of the Matsudai Knee Osteoarthritis Survey. Bilateral quadriceps strengths of each subject were measured using the quadriceps training machine (QTM-05F, Alcare Co., Ltd., Tokyo, Japan). Additionally, weight-bearing standing knee radiographs were obtained, and knee OA was graded according to the Kellgren-Lawrence classification system. The relationships between quadriceps strength and the incidence and progression of radiographic knee OA were assessed using multiple logistic regression analysis. RESULTS: After adjusting for age and body mass index (BMI), both female and male knees in the lowest quantile of quadriceps strength had higher risk of the incidence of radiographic knee OA compared with the highest quantile of quadriceps strength (women: OR 2.414, 95% CI 1.098-5.311; men: OR 2.774, 95% CI 1.053-7.309). In contrast, after adjusting for age, BMI and femorotibial angle, both female and male knees in the lowest quantile compared with the highest quantile of quadriceps strength did not differ in risk of the progression of radiographic knee OA (women: OR 1.040, 95% CI 0.386-2.802; men: OR 2.814, 95% CI 0.532-14.898). CONCLUSION: Quadriceps muscle weakness was related to increased risk of the incidence of radiographic knee OA, but not its progression, in both women and men. Therefore, the clinically important finding of this study is that, in both women and men, maintaining higher quadriceps muscle strength may be one of the most effective prevention methods for incident radiographic knee OA. LEVEL OF EVIDENCE: II.

Increasing incidence of fracture and its sex difference in school children: 20 year longitudinal study based on school health statistic in Japan.

BACKGROUND: Studies on the epidemiology of pediatric fractures have been scarce in recent years although fractures are very common in childhood. Boys have a higher incidence of fractures than girls. Currently, societal trends have seemed to influence the difference in activity patterns between boys and girls, but the sex difference regarding longitudinal changes in fracture incidence is not well known. METHODS: We analyzed the school accident report in Niigata city, Japan and compared the incidence of fractures in elementary and junior high school students and the sex-related risk ratio between two 9-year periods separated by 20 years from their start and end points (1999-2007 and 1979-1987). RESULTS: The study included 383,273 students from 1999 to 2007 and 561,109 students from 1979 to 1987. Comparing these periods, the fracture incidence increased significantly by 2.4 times in boys vs 2.1 times in girls from elementary school and by 2.2 times in boys vs 2.9 times in girls from junior high school (all p ï¼œ 0.001). The sex-related risk ratio of boys to girls increased significantly from 1.47 to 1.64 in elementary school students. In contrast, it decreased significantly from 3.29 to 2.52 in junior high school students and the change was markedly significant because of the drastic increase in fracture incidence in junior high school girls. CONCLUSIONS: The reasons proposed for the increase in schoolchildren's fractures were an improvement in diagnosis owing to social background and increased participation in sports activities despite the general decline in children's physical fitness and exercise ability. In junior high school girls, in particular, there was an increase in fracture risk due to increased participation in sports activities.

Sex differences in femoral deformity determined using three-dimensional assessment for osteoarthritic knees.

PURPOSE: To characterize femoral deformities and determine sex differences in varus knee osteoarthritis (OA), femoral morphology and limb alignment were evaluated by using three-dimensional (3D) assessment, comparing healthy, elderly volunteers with osteoarthritic knees. METHODS: A total of 178 lower limbs of 169 subjects with knee osteoarthritis (136 women, 33 men; mean age 74.9 ± 5.2 years) and 80 lower limbs of 45 healthy, elderly subjects (24 women, 21 men; mean age 65 ± 4.9 years) were examined. A 3D extremity alignment assessment system was used to examine the subjects under weight-bearing conditions on biplanar long-leg radiographs using a 3D-to-2D image registration technique. The evaluation parameters were (1) femoral bowing in the coronal plane, (2) femoral bowing in the sagittal plane, (3) femoral neck anteversion, (4) hip-knee-ankle angle, and (5) femoral torsion. RESULTS: Higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis were observed in women with OA compared with healthy subjects. No difference in the higher varus malalignment, no alteration in the femoral anterior bowing, and no difference in the lower femoral neck anteversion were found between men and women when comparing healthy and OA subjects. CONCLUSIONS: The higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis in women are possibly a structural adaptation to mechanical use. The clinical significance is that the femoral deformities and the sex differences in knee OA have the potential to improve the understanding of the aetiology of primary varus knee OA. LEVEL OF EVIDENCE: IV.

External torsion in a proximal tibia and internal torsion in a distal tibia occur independently in varus osteoarthritic knees compared to healthy knees.

INTRODUCTION: The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees. METHODS: In total, 61 limbs in 58 healthy subjects (age: 54 ± 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 ± 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis. RESULTS: The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p < 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group. CONCLUSION: The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees. LEVEL OF EVIDENCE: Level Ⅲ.

The varus alignment and morphologic alterations of proximal tibia affect the onset of medial knee osteoarthritis in rural Japanese women: Case control study from the longitudinal evaluation of Matsudai Knee Osteoarthritis Survey.

BACKGROUND: Relationship malalignment of the knee and the onset of knee OA are unclear. Moreover, it has not been clarified whether malalignment of the knee affects the morphological change of the proximal tibia. The purpose of current study was to investigate whether varus knee alignment and morphological change of the proximal medial tibia influence the onset of medial knee OA and to clarify the relationship between them. METHODS: The subjects comprised 736 knees from 390 women that went under both the first survey in 1979 and the fourth survey in 2000 in the Matsudai district in Niigata Prefecture in Japan. None of the subjects demonstrated radiographic knee OA at the first survey. OA was graded according to the Kellgren-Lawrence classification and the subjects were divided according to the OA grades in the forth survey into the 3 groups (non-OA, early OA, and advanced OA). Age, BMI, Femorotibial angle (FTA), the tibial plateau angle and medial tibial cortical bone thickness (MTCBT) were measured. We performed multivariate logistic regression analysis using the stepwise method to identified the risk factors regarding onset of knee OA and calculated the odds ratio (OR) and 95% confidence intervals (95% CI). RESULTS: Advanced OA had a significantly higher OR compared to non-OA in 1979 with the tibial plateau angle (OR: 1.15) and MTCBT (OR: 2.11). And also advanced OA had a significantly higher OR compared to early-OA in 1979 with the tibial plateau angle (OR: 1.17) and MTCBT (OR: 1.62). CONCLUSIONS: In the advanced OA, varus alignment of the proximal tibia had already existed before the onset of knee OA. In addition, we thought that varus alignment due to the proximal tibia had influenced the morphologic alterations of proximal medial tibia.

Association of mechanical factors with medial knee osteoarthritis: A cross-sectional study from Matsudai Knee Osteoarthritis Survey.

BACKGROUND: Knee osteoarthritis (OA) is a multifactorial disease that is affected by mechanical factors. The aim of present study was to investigate the association between multiple mechanical factors and medial knee OA in a large epidemiological cohort. METHODS: Six hundred and ninety-nine subjects (323 males and 376 females), participating in the Matsudai Knee Osteoarthritis Survey 2010, were included. Twelve mechanical factors were selected and their association with the radiographic grade of knee OA, the Western Ontario and McMaster University Index (WOMAC) pain score, and the WOMAC function score was evaluated. RESULTS: A logistic regression analysis identified varus thrust to be associated with the radiographic grade of knee OA in males (OR: 1.876, 95% CI: 1.332-2.663) and females (2.61, 1.922-3.542), the WOMAC pain score in males (1.997, 1.463-2.672), and the WOMAC function score in females (1.449, 1.12-1.874). Quadriceps muscle strength was associated with the radiographic OA grade in males (0.605, 0.399-0.917) and females (0.636, 0.469-0.863), the WOMAC pain score in females (0.537, 0.445-0.789), and the WOMAC function score in males (0.581, 0.44-0.766). The knee flexion angle was also associated with the radiographic OA grade in males (0.344, 0.19-0.621) and females (0.121, 0.022-0.653), and the WOMAC pain score in males (0.287, 0.156-0.53) and females (0.537, 0.336-0.859). Obesity was associated with the radiographic OA grade in males (1.543, 1.041-2.287) and females (1.589, 1.176-2.146), the WOMAC pain score in female (2.017, 1.517-2.68). Femolo-tibial angle had no significant association with the radiographic knee OA grade or with the WOMAC pain and function scores. CONCLUSION: Among patients with medial knee OA, dynamic mechanical factors, such as varus thrust, quadriceps muscle strength, and range of motion were more likely to be associated with the radiographic grade of knee OA and to be the WOMAC pain and function scores, compared to static mechanical factors.

Three-dimensional in vivo dynamic motion analysis of anterior cruciate ligament-deficient knees during squatting using geometric center axis of the femur.

BACKGROUND: Anterior cruciate ligament (ACL) injury often leads to symptoms of instability, which may cause meniscus injury, osteochondral lesions, and degenerative changes. For thorough evaluation of the effects of abnormal motion of ACL-deficient (ACLD) knees on the meniscus and articular cartilage, it is necessary to assess tibiofemoral motion in the medial and lateral compartments separately. Our aim was to determine if in vivo three-dimensional (3D) dynamic motion of ACLD knees differs from that of contralateral uninjured knees by assessing knee motion in the medial and lateral compartments respectively. METHODS: A total of 22 patients with an isolated ACL-injured knee were examined. 3D to two-dimensional registration was used to determine 3D knee motion during squatting from full knee extension to full flexion for both ACLD and contralateral uninjured knees. The knee motion was evaluated by the movement of the geometric center axis of the femur projected onto the tibial axial plane. RESULTS: In ACLD knees the lateral femoral condyle was located significantly more posteriorly during nearly full extension than in contralateral uninjured knees. The range of anteroposterior translation of the medial femoral condyle was significantly greater than those of contralateral uninjured knees. Almost all of the contralateral uninjured knees demonstrated medial pivot motion, while the ACLD knees showed higher variance. CONCLUSIONS: The ACLD knees exhibited a motion pattern different from those of contralateral uninjured knees with higher variance. During nearly full extension of the ACLD knees, the lateral femoral condyle translated posteriorly and the screw-home movement seemed to be impaired. The ACL might have an important role in maintaining normal knee function, especially during the early flexion phase. The larger range of anteroposterior translation of the medial femoral condyle in ACLD knees may be associated with a risk of secondary meniscal injury and degenerative change in the articular cartilage. LEVEL OF EVIDENCE: Level IV.

Unicompartmental knee arthroplasty cannot restore the functional flexion axis of a living knee to normal.

PURPOSE: The purpose of this study was to investigate the hypothesis that a medial unicompartmental knee arthroplasty might restore the functional flexion axis of a knee to normal. The flexion axis can be indirectly identified by tracking the vertical translation of anatomic landmarks that basically move around the flexion axis during a knee motion. If a unicompartmental knee could help restore the normal flexion axis, the anatomic landmarks after the arthroplasty would show the vertical translation similar to those of normal knees during a knee flexion. METHODS: While performing a squatting motion, the kinematics of 17 knees were determined before and after a medial unicompartmental arthroplasty to calculate the vertical translation of a clinical epicondylar axis, using a three- to two-dimensional registration technique through a single-plane fluoroscopic system incorporating a biplanar static radiography. The results were compared with a normal data, and a statistical analysis including a two-way repeated-measured analysis of variance was performed. RESULTS: For the medial end, from 10° to 100° knee flexion, normal, osteoarthritic, and unicompartmental knees had the average superior vertical translation of 7.3 ± 4.2, 4.3 ± 7.2, and 2.4 ± 3.1 mm, respectively, with statistical significance between normal and unicompartmental knees (p < 0.001). The vertical translation did not return to normal post-implantation. CONCLUSIONS: A unicompartmental knee could not reproduce the normal flexion axis. As for clinical relevance, the changes of the implant design and surgical procedure may be necessary to obtain the normal flexion axis reproducing a normal motion. LEVEL OF EVIDENCE: IV.

Three-dimensional motion analysis and its application in total knee arthroplasty: what we know, and what we should analyze.

INTRODUCTION: This paper will review three-dimensional (3D) motion analysis studies done in my laboratory to present an overview of what we have found. MATERIALS AND METHODS: We have looked at parameters such as roll-back, rotation, the pivot center of rotation etc. using a 2D-3D registration technique by evaluating knees before and after implantation of a total knee arthroplasty. CONCLUSION: This technique allows comparison of preoperative motion to that after total knee surgery. We have found the phenomenon of "reverse screw-home" to be a common motion pattern in osteoarthritis and it is often present after implantation of a total knee prosthesis.

Kinematics of the knee after unicompartmental arthroplasty is not the same as normal and is similar to the kinematics of the knee with osteoarthritis.

PURPOSE: It is common to assert that restoration of normal knee kinematics is essential for the best functional result after knee arthroplasty. Previous studies using the progression of the geometric centre axis have suggested that kinematics after unicompartmental arthroplasty is markedly different from the normal. For this study, the transepicondylar axis was used because this axis is closer to the flexion axis and should be a better reference for motion. The following hypothesis was tested: the transepicondylar axis would again show that the postoperative kinematics does not restore normal motion and is closer to that before replacement. METHODS: Seventeen osteoarthritic knees were tested before and after unicompartmental arthroplasty using a three-dimensional to two-dimensional registration technique tracking the transepicondylar axis to calculate translation and rotation of this axis. Results were compared for the seventeen knees before and after arthroplasty and were compared to the normal knee as measured in our previous study. RESULTS: Similar motion patterns in the pre- and postoperative knees were shown but both the pre- and postoperative motion were markedly different from the normal knee. CONCLUSIONS: This result supported our hypothesis. The clinical relevance is that medial unicompartmental arthroplasty cannot restore the motion of the knee to normal in the living knee. Therefore, it would be expected that the patient for unicompartmental knee might not feel normal. It may not be possible depending on ligaments alone to restore the knee to normal, and the changes in the articular shapes and the surgical procedure may also be necessary.

Change in tibiofemoral rotational alignment during total knee arthroplasty.

BACKGROUND: Rotational mismatch between femoral and tibial components has been recognized as a risk factor of unsuccessful total knee arthroplasty (TKA), but a main cause of rotational mismatch is uncertain. This study aims to evaluate rotational alignment of the knee by measuring both component rotation and version of the knee in TKA. METHOD: Fifty-one TKAs (mean age 73.7 years) were included in this study. The three dimensional, weight-bearing knee alignment was measured before and after TKA. A transepicondylar axis was referenced to femoral component rotation, and an anteroposterior axis of the tibia (middle of posterior cruciate ligament attachment to medial border of patella tendon attachment) was referenced to tibial component rotation. Knee rotational angle was defined as the angle between these two axes. RESULT: The mean preoperative knee rotation angle of 9.7° (±8.5°) internal rotation was significantly reduced to 1.8° (±7.3°) external rotation after TKA. Twenty-one of 51 knees (41%) exhibited rotational mismatch (>10°) preoperatively, and this number was reduced to eight knees (16%) post-TKA. The femoral component was rotationally aligned within 5° of neutral in all knees, while rotational alignment of the tibial component showed a high degree of variability (range 20.7° internal rotation to 17.2° external rotation). CONCLUSION: Rotational malposition of the tibial component was considered to be a main factor of rotational mismatch of the knee after TKA.

Usefulness of urinary CTX-II and NTX-I in evaluating radiological knee osteoarthritis : the Matsudai knee osteoarthritis survey.

BACKGROUND: To assess the usefulness of the urinary crosslinked C-telopeptide of type II collagen (uCTX-II) or crosslinked N-telopeptide of type I collagen (uNTX-I) for evaluating radiological knee osteoarthritis (OA), a cross-sectional study was conducted in the cohorts of the Matsudai knee osteoarthritis survey performed in Niigata, Japan. METHODS: Urine specimens and standing knee AP X-rays were obtained from 1040 subjects who provided informed consent. The relationship between these markers and gender, age (patients aged 40-59 or 60-79 years), use of bisphosphonates, and OA grades (K-L classification) were analyzed. The diagnostic ability of uCTX-II to detect radiological knee OA was confirmed in the over 60-year-old subjects using a ROC curve. RESULTS: The over 60-year-old men with OA grade 3,4 group had significantly higher uCTX-II levels than the other OA grade groups. In the over 60-year-old women, the uCTX-II levels significantly increased according to the progression of the knee OA grade. No significant difference was observed between the uNTX-I levels in the different OA grade groups. From the standpoint of biomarkers, the higher quartiles of the uCTX-II and uNTX-I levels gradually included higher numbers of grade ≥2 OA subjects in the over 60 year-old women. The area under the curve (AUC) in ROC analysis of uCTX-II exhibited a significant association with the diagnosis of knee OA in women (AUC 0.63), although the accuracy was evaluated to be low in the single measurement of our health checkup-based analysis. CONCLUSIONS: This population-based study indicates that the uCTX-II level is strongly correlated with the knee OA grade in women over age 60. A further analysis is needed to clarify its predictive accuracy.

The clinical epicondylar axis is not the functional flexion axis of the human knee.

BACKGROUND: The functional flexion axis (FFA) is the principal axis around which the knee moves and thus, by definition, does not move in vertical displacement relative to the tibia. The transepicondylar axis (TEA) has been reported to coincide with the FFA. If that is not true, the TEA should show vertical displacement during motion, and this hypothesis was investigated. METHODS: Three-dimensional knee kinematics of 20 healthy volunteers were determined during a squatting motion via a 3-dimensional to 2-dimensional image registration technique by calculating the vertical displacement of the clinical epicondylar axis (CEA) through the full range of motion. RESULTS: From 0° to 90° knee flexion, the average vertical displacement of the lateral end of the CEA was <3 mm, whereas that of the medial end was large (7.6 mm). DISCUSSION: The large vertical displacement of the medial end of the CEA suggests that the CEA is not the FFA. This finding implies that the CEA may not be an appropriate axis for a TKA prosthesis having a "single radius" design. EVIDENCE LEVEL: Level IV.