Mobile medial pivot (lateral slide)-type total knee arthroplasty exhibited different motion patterns between under anaesthesia and weight-bearing condition.

PURPOSE: Total knee arthroplasty (TKA), which has medial pivot and mobile-bearing mechanisms, has been developed and clinically used. However, the in vivo dynamic kinematics of the mobile medial pivot-type TKA (MMPTKA) is unclear. This study analysed the in vivo kinematics of MMPTKA in weight-bearing and nonweight-bearing conditions. METHODS: The study included 10 knees that underwent primary TKA using MMPTKA. After TKA, lateral view radiographs of the knee in full extension, 90° of flexion and passive full flexion were taken under general anaesthesia in the nonweight-bearing condition. At least 6 months postoperatively, knee motion during squatting from a weight-bearing standing position was observed using a flat-panel detector and analysed using the three-dimensional-to-two-dimensional image registration technique. RESULTS: Under anaesthesia: in passive full flexion, the anteroposterior (AP) locations of the femoral component's medial and lateral distal points were 10.2 and 16.0 mm posterior, and the rotational angles of the femoral component's X-axis (FCX) and insert were 8.1° external rotation and 18.5° internal rotation to full extension, respectively. Squatting: the AP translations of the femoral component's medial and lateral most distal points were 2.2 and 6.4 mm, and the rotational angles of the FCX and insert were 5.7° and 1.6° external rotation, respectively. Significant differences were observed in the AP translation of the femoral component's medial and lateral most distal points and changes in the insert's rotational angle when comparing under anaesthesia and squatting. CONCLUSIONS: The kinematics of the insert in MMPTKA was significantly influenced by loading and muscle contraction. The femoral component exhibited substantial external rotation and posterior translation under anaesthesia, which may contribute to achieving an optimal range of motion. The insert remained relatively stable during squatting and minimal rotation was observed, indicating good stability. MMPTKA was expected to demonstrate rational kinematics by incorporating mobile and medial pivot mechanisms. LEVEL OF EVIDENCE: Level IV, prospective biomechanical case series study.

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.

Reduced somatosensory evoked potentials and paired-pulse inhibition in the primary somatosensory cortex of athletes with chronic pain.

PURPOSE: Chronic pain impedes athletic training and performance. However, it is challenging to identify the precise causes of chronic pain for effective treatment. To examine possible neuroplastic changes in sensory transmission and cortical processing, we compared somatosensory evoked potentials (SEPs) and paired-pulse inhibition (PPI) in primary sensory cortex (S1) between athletes with chronic pain and control athletes. METHODS: Sixty-six intercollegiate athletes (39 males and 27 females) were recruited for this study, 45 control athletes and 21 reporting persistent pain for > 3 months. Sensory-evoked potentials were induced in S1 by constant-current square-wave pulses (0.2-ms duration) delivered to the right median nerve, while PPI was induced by paired stimulation at interstimulus intervals of 30 and 100 ms (PPI-30 and PPI-100 ms, respectively). All participants were randomly presented with total 1,500 (each 500 stimuli) single stimuli and stimulus pairs at 2 Hz. RESULTS: Both N20 amplitude and PPI-30 ms were significantly lower in athletes with chronic pain compared to control athletes, while P25 amplitude and PPI-100 ms did not differ significantly between groups. CONCLUSION: Chronic pain in athletes is associated with substantially altered excitatory-inhibitory balance within the primary somatosensory cortex, possibly due to reduced thalamocortical excitatory transmission and suppressed cortical inhibitory transmission.

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.

Improved responsiveness for JKOOS+ compared to KOOS in Japanese patients undergoing total knee arthroplasty.

BACKGROUND: Existing knee related patient reported outcome measurements (PROMs) have overwhelmingly been developed and validated in western chair-based societies, suggesting a potential for a western bias in PROMs evaluation of patients with knee conditions. We, therefore, endeavor to evaluate the responsiveness of the previously developed culturally relevant Japanese version of the knee injury and osteoarthritis outcome score (JKOOS+). METHODS: We enrolled 114 patients scheduled for total knee arthroplasty (TKA) across 8 knee clinics in Japan. Patients completed the Oxford Knee Score (OKS) and JKOOS + both at the time of enrollment and again 1-year post-TKA. Responsiveness was evaluated using effect size and standardized response mean (SRM). An effect size or SRM >0.8 is considered adequately responsive. We further tested the difference in responsiveness between the original Japanese language KOOS activities of daily living (ADL) domain and the novel Japanese ADL (JADL) domain using the modified Jacknife test. RESULTS: All domains were adequately responsive with the exception of the KOOS sports and recreation domain, which has previously been ignored by TKA researchers due to its lack of applicability to elderly patients undergoing TKA. The JADL domain outperformed the ADL domain in both effect size (1.51 v. 1.45) and SRM (1.67 v. 1.57) (p < 0.001). The novel Knee Flexion (KF) domain was adequately responsive, though less responsive than other domains except sports and recreation (p < 0.01 v. all other PROMs domains). CONCLUSIONS: The JKOOS+ JADL domain is significantly more responsive than the Europe-developed ADL domain to TKA in Japanese knee patients suffering from knee osteoarthritis (OA). The KF domain, unique to the JKOOS+ and intended to assess difficulty with knee flexion, is adequately responsive to TKA in Japanese patients suffering from OA.

Characterization of Leukocyte- and Platelet-Rich Plasma Derived from Female Collage Athletes: A Cross-Sectional Cohort Study Focusing on Growth Factor, Inflammatory Cytokines, and Anti-Inflammatory Cytokine Levels.

Platelet-rich plasma (PRP) has been increasingly used in sports medicine owing to its various advantages. The purpose of our project was to standardize the parameters before performing large-scale clinical trials in the near future to precisely evaluate individual PRP quality. To examine the effects of regular exercise on PRP quality, this study focused on young female athletes, who have been relatively less studied. Blood samples were obtained from female college athletes (n = 35) and ordinary healthy adults (n = 30), which were considered as controls, and leukocyte-rich PRP (L-PRP) was prepared manually. Body composition indices were determined using a bathroom weight scale equipped with an impedance meter. Growth factors and cytokines were quantified using ELISA kits. Platelet-derived growth factor-BB (PDGF-BB) and Transforming-growth factors ß1 (TGFß1) levels (per platelet) in L-PRP were significantly lower in female athletes than in controls. In contrast, Interleukin-1ß and Interleukin 1 receptor antagonist (IL-1RA) levels (per platelet and L-PRP) in L-PRP were significantly higher in athletes, and this difference was more prominent in IL-1RA. These findings suggest that L-PRP from athletes may facilitate the inflammatory phase of the healing process by regulating the pro-inflammatory and anti-inflammatory balance. These chemical compositions can be adopted as "must-check" parameters to characterize individual PRP preparations prior to clinical trials.

Elevated IL-1ß and Comparable IL-1 Receptor Antagonist Levels Are Characteristic Features of L-PRP in Female College Athletes Compared to Male Professional Soccer Players.

Autologous platelet-rich plasma (PRP) therapy has been becoming popular for the treatment of musculotendinous injuries among athletes. However, for individual and practical variations, clinical success is hardly predictable. To overcome this difficulty, we have been exploring possible criterion candidates for monitoring its clinical effectiveness. In this study, we focused on sex-based differences in young elite athletes and compared the biochemical compositions of their PRP. Leukocyte-rich PRP (L-PRP) was manually prepared from blood samples collected from male professional soccer players (mPSPs) (n = 25) and female college athletes (fCAs) (n = 36). Platelet-derived growth factor-BB (PDGF-BB), transforming-growth factor-ß1 (TGFß1), platelet factor-4 (PF4), interleukin-1ß (IL-1ß), and IL-1 receptor antagonist (IL-1RA) were quantified using an enzyme-linked immunosorbent assay. The levels of PDGF-BB, TGFß1, and PF4 in L-PRP were significantly higher in mPSPs than in fCAs. Conversely, IL-1ß and IL-1RA were detected at significantly and slightly higher levels, respectively, in fCAs than in mPSPs. Our findings suggest that, even though L-PRP from fCAs may have lower potential to induce cell growth and differentiation than that of mPSPs, due to the latter's higher capacity to control inflammation, it does not necessarily imply that PRP treatment in fCAs is less effective. Thus, these cytokine levels should be checked before PRP therapy.

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.

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.

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.

Scoring system for optimal management of acute traumatic patellar dislocation: A multicenter study.

BACKGROUND: In first-time acute traumatic patellar dislocations, numerous anatomic and clinical factors are complicatedly associated and should be comprehensively considered for the optimal management of conservative or surgical intervention. The purpose of this study was to establish a scoring system, using a concept that is not complicated and easily used in clinic. METHODS: Of 131 first-time acute traumatic patellar dislocations, 81 patients (51 females, 30 males) with an average age of 19.6 (95%CI, 17.5-21.6) years and an average follow-up duration of 17.1 (95% CI, 12.3-21.9) months, who underwent conservative treatment after first-time dislocations, were reviewed. Based on the odds ratios applying logistic regression analysis, the scoring system was established. RESULTS: The scoring system (total: 10 points) had simple composition of age <20 (2 points), sports injury (1 points), hemarthrosis (1 points), and image findings of a bony fragment (3 points), lateral shift of the patella (1 points), and trochlear dysplasia (2 points). A threshold score of 6.5 was determined using the area under receiver operating characteristic curve of 0.893 (p < 0.0001). In logistic regression analysis, a score of ≥7 was shown to be a dominant factor for recurrence (OR = 27.1, p < 0.0001). Furthermore, the association between the score and recurrence risk was as follows: a score of ≤4 = low risk (1/21 cases, 5%); a score of 5-7 = medium risk (13/27 cases, 48%); a score of ≥8 = high risk (30/33 cases, 91%). CONCLUSIONS: Based on the simple scoring system, patients who scored ≥8 were considered suitable for surgical treatment because of the high rate of recurrence, whereas those who scored ≤4 were considered suitable for conservative treatment because of the low rate of recurrence.

Reference values for the locomotive syndrome risk test quantifying mobility of 8681 adults aged 20-89 years: A cross-sectional nationwide study in Japan.

BACKGROUND: The locomotive syndrome risk test was developed to quantify the decrease in mobility among adults, which could eventually lead to disability. The purpose of this study was to establish reference values for the locomotive syndrome risk test for adults and investigate the influence of age and sex. METHODS: We analyzed 8681 independent community dwellers (3607 men, 5074 women). Data pertaining to locomotive syndrome risk test (the two-step test, the stand-up test, and the 25-question geriatric locomotive function scale [GLFS-25]) scores were collected from seven administrative areas of Japan. RESULTS: The reference values of the three test scores were generated and all three test scores gradually decreased among young-to-middle-aged individuals and rapidly decreased in individuals aged over 60 years. The stand-up test score began decreasing significantly from the age of 30 years. The trajectories of decrease in the two-step test score with age was slightly different between men and women especially among the middle-aged individuals. The two physical test scores were more sensitive to aging than the self-reported test score. CONCLUSION: The reference values generated in this study could be employed to determine whether an individual has mobility comparable to independent community dwellers of the same age and sex.

Development and validation of a culturally relevant Japanese KOOS.

INTRODUCTION: The Knee Injury and Osteoarthritis Outcomes Survey (KOOS) has been translated into 50 languages worldwide. These translations have adhered to guidelines for cross cultural adaptation of health surveys. However, after release of the Japanese KOOS (JKOOS) we discovered the JKOOS was not fully culturally relevant to Japanese patients. Therefore, we undertook the development and validation of the JKOOS+. METHODS: We completed this project in 2 phases across 9 hospitals. In Phase 1, 187 surgically naïve patients with knee pain were asked about activities limited by their knee pain. An expert panel reconciled these activities against existing KOOS items to identify novel items. In Phase 2, 241 surgically naïve patients with knee pain were administered the Japanese Oxford Knee Survey, JKOOS, and these novel items. An iterative Rasch analysis was used to test item fit of these novel items within the KOOS Activities of Daily Living (ADL) domain and a potential new domain. Unidimensionality was assessed using principle component analysis. Internal consistency (Cronbach's alpha) and external validity (Spearman's Correlations) were assessed for Japanese ADL (J-ADL) and the novel domain. RESULTS: Phase 1 identified 4 activities relevant to Japanese knee patients: sitting seiza, using a Japanese toilet, climbing hills, and getting on/off a bus/train. In Phase 2, climbing hills and bus/train were well fit in JADL. Seiza and using a Japanese toilet were not well fit in J-ADL, yet both require deep knee flexion so a knee flexion (KF) domain was constructed by considering all KOOS items that require knee flexion using an iterative Rasch model. An 8 item KF domain emerged. Both J-ADL and KF were deemed to be unidimensional with high internal consistency (Cronbach's alpha >0.92) and external validity (Spearman Correlations 0.723-0.929). CONCLUSIONS: We have successfully developed and validated JKOOS+, a more culturally relevant knee survey for Japanese patients.

Morphological characteristics of the lateral talocalcaneal ligament: a large-scale anatomical study.

PURPOSE: The purpose of this study is to clarify the morphological characteristics of the lateral talocalcaneal ligament (LTCL). METHODS: This study examined 100 legs from 54 Japanese cadavers. The LTCL was classified into three types: Type I, the LTCL branches from the calcaneofibular ligament (CFL); Type II, the LTCL is independent of the CFL and runs parallel to the calcaneus; and Type III, the LTCL is absent. The morphological features measured were fiber bundle length, fiber bundle width, and fiber bundle thickness. RESULTS: The LTCL was classified as Type I in 18 feet (18%), Type II in 24 feet (24%), and Type III in 58 feet (58%). All LTCLs were associated with the anterior talofibular ligament at the talus. There was no significant difference in morphological characteristics by Type for each ligament. CONCLUSIONS: The LTCL was similar to the CFL in terms of fiber bundle width and fiber bundle thickness.

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.

Correction to: Alignment in the transverse plane, but not sagittal or coronal plane, affects the risk of recurrent patella dislocation.

The author would like to correct the errors in the publication of the original article. The corrected detail is given below for your reading.

Alignment in the transverse plane, but not sagittal or coronal plane, affects the risk of recurrent patella dislocation.

PURPOSE: Abnormalities of lower extremity alignment (LEA) in recurrent patella dislocation (RPD) have been studied mostly by two-dimensional (2D) procedures leaving three-dimensional (3D) factors unknown. This study aimed to three-dimensionally examine risk factors for RPD in lower extremity alignment under the weight-bearing conditions. METHODS: The alignment of 21 limbs in 15 RPD subjects was compared to the alignment of 24 limbs of 12 healthy young control subjects by an our previously reported 2D-3D image-matching technique. The sagittal, coronal, and transverse alignment in full extension as well as the torsional position of the femur (anteversion) and tibia (tibial torsion) under weight-bearing standing conditions were assessed by our previously reported 3D technique. The correlations between lower extremity alignment and RPD were assessed using multiple logistic regression analysis. The difference of lower extremity alignment in RPD between under the weight-bearing conditions and under the non-weight-bearing conditions was assessed. RESULTS: In the sagittal and coronal planes, there was no relationship (statistically or by clinically important difference) between lower extremity alignment angle and RPD. However, in the transverse plane, increased external tibial rotation [odds ratio (OR) 1.819; 95% confidence interval (CI) 1.282-2.581], increased femoral anteversion (OR 1.183; 95% CI 1.029-1.360), and increased external tibial torsion (OR 0.880; 95% CI 0.782-0.991) were all correlated with RPD. The tibia was more rotated relative to femur at the knee joint in the RPD group under the weight-bearing conditions compared to under the non-weight-bearing conditions (p < 0.05). CONCLUSIONS: This study showed that during weight-bearing, alignment parameters in the transverse plane related to the risk of RPD, while in the sagittal and coronal plane alignment parameters did not correlate with RPD. The clinical importance of this study is that the 3D measurements more directly, precisely, and sensitively detect rotational parameters associated with RPD and hence predict risk of RPD. LEVEL OF EVIDENCE: III.

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.