Objective: This study investigates the impact of age and knee osteoarthritis (OA) on the coronal plane alignment of the lower extremity in Japanese males and females, utilizing the Coronal Plane Alignment of the Knee (CPAK) classification system. Methods: A cross-sectional analysis was conducted with 150 male and 150 female patients. Participants were divided into three groups according to age and OA progression. The mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA) were measured using standard digital long-leg radiographs. Arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) were calculated, and the CPAK classification was performed to verify the distribution among the three groups. Results: The results showed increased varus alignment of the mean mLDFA correlated with OA in both genders and with aging in males. The mean mMPTA did not change in males but shifted toward varus in females with both aging and OA. Both genders demonstrated a constitutional varus alignment with the progression of osteoarthritis (males: 1.3 ± 2.4° to −3.5 ± 3.7°, p < 0.001; females: −1.2 ± 3.2° to −3.6 ± 2.9°, p < 0.001). However, this trend with aging was observed only in females (0.0 ± 2.5° to −1.2 ± 3.2°, p = 0.018). JLO maintained its apex distal position with aging and OA progression in all subjects. The study further revealed a notable transition from CPAK Type II to Type I with OA progression in both genders, additionally influenced by aging in females. Conclusions: Aging affects coronal alignment and CPAK classification differently across genders. With OA progression, there was a shift toward smaller aHKA, while JLO remained unchanged. Compared to other races, young Japanese people exhibit similar CPAK distributions, but distinct differences appear in OA-affected individuals, highlighting potential racial variations in CPAK classifications.

Orthopedic implants such as arthroplasty prostheses, fracture plates, and intramedullary nails often use materials like Ti6Al4V alloy and commercially pure titanium (CP-Ti), which have Young's modulus significantly higher than that of human cortical bone, potentially causing stress shielding and inhibiting effective fracture healing. TiNbSn alloy, a β-type titanium alloy with a lower Young's modulus (40-49 GPa), has shown promise in reducing stress shielding and enhancing bone healing by promoting effective load sharing with bone. This study used 5-hole plates made from TiNbSn alloy and CP-Ti to investigate their effects on bone healing in a rat femoral fracture model. Micro-CT analysis and mechanical testing were performed six weeks postoperatively to assess bone healing. Additionally, Finite element method (FEM) analysis was employed to evaluate stress shielding and interfragmentary movement (IFM) at the fracture site. Micro-CT analysis revealed significantly higher bone volume and mineral density in the TiNbSn group than in the CP-Ti group. Mechanical testing showed increased maximum load and stiffness in the TiNbSn group (77.2 ± 10.0 N for the TiNbSn alloy plate group versus 53.3 ± 8.5 N for the CP-Ti group (p = 0.002)). FEM analysis indicated that TiNbSn plates reduced stress shielding and allowed for greater displacement and strain, promoting IFM conducive to bone healing. The findings suggest that TiNbSn alloy plates are more effective than CP-Ti plates in promoting bone healing by reducing stress shielding and enhancing IFM. The lower Young's modulus of TiNbSn allows better load distribution, facilitating bone regeneration and strengthening at the fracture site.

Background: This study investigated the impact of total knee arthroplasty (TKA) on the alignment of the ankle joint, focusing on changes in coronal alignment of both ankles. Methods: This retrospective study, conducted at our hospital, included 64 patients older than 70 years who underwent TKA for varus knee osteoarthritis (OA). Using full-length standing radiographs of both lower extremities taken preoperatively and 6 months postoperatively, we assessed ankle OA grading based on the Takakura-Tanaka classification and measured mechanical hip-knee-ankle (mHKA) and the tibiotalar angle (TTA) on both the surgical and contralateral side. Additionally, we examined the impact of ankle OA on postoperative clinical scores, the Knee injury and Osteoarthritis Outcome Score, following TKA. Results: Based on the classification, ankle OA stage 2 or higher was present in 13 cases on the surgical side and 13 cases on the contralateral side. On the surgical side, mHKA changed from 12.2 to 1.8 degrees varus ( P < .001) and TTA from 1.7 to 1.0 degrees varus ( P = .002). On the contralateral side, mHKA changed from 4.0 to 5.4 degrees varus ( P = .04), and TTA from 2.7 to 3.0 degrees varus ( P < .001). In ankle OA stage 2 or higher patients, contralateral TTA changed from 5.2 to 6.5 degrees varus ( P < .001) and unchanged in stage 1 patients. Ankle OA stage 2 or higher patients had worse ADL outcomes than stage 1 patients (score: 67.2 and 78.3, respectively, P = .03). Conclusion: This study suggests an apparent interrelationship between knee and ankle OA and the potential negative influence of TKA on ankle OA.

Jones fractures, stress fractures at the proximal metaphyseal-diaphyseal junction of the fifth metatarsal, are common in sports that involve repetitive jumping and turning, particularly football (i.e., soccer). The incidence among Japanese football players is higher than in Europe, with a high refracture rate, particularly in conservatively managed cases. Although surgical treatment is preferred for athletes, limited data exist on risk factors in youth players. This study aimed to investigate the prevalence and risk factors for Jones fractures among high-level Japanese high school football players through medical examinations. Medical examinations were conducted during the 2024 tournament involving 20 top-level high school teams (567 players). Ultrasound and X-ray imaging identified fractures, and players underwent various physical tests, including hip internal rotation (HIR) and weight-bearing position during a single heel raise (SHR). A questionnaire collected demographic data and fracture histories. Statistical analyses, including the Wilcoxon signed-rank test and Mann-Whitney U test, were conducted to determine associations with fracture risk. Of 232 male players (40.9 % of all), 18 (7.8 %) tested positive on ultrasound, seven (3.0 %) had confirmed fractures on radiography, and 11 reported a history of Jones fractures. Players with restricted HIR <30° and lateral weight-bearing during SHR showed a significantly higher fracture risk (Crude Odds Ratio: 3.74, p = 0.01). Additional lateral weight bearing during SHR increased the risk (Crude Odds Ratio, 4.02; p = 0.007). Restricted HIR and lateral weight-bearing during SHR were identified as risk factors for Jones fractures in youth football players. Recognizing these factors may enable targeted preventive measures to reduce injury risk in high-level athletes.

Background: Lateral ankle sprains frequently result in anterior talofibular ligament (ATFL) dysfunction, leading to chronic lateral ankle instability. The ATFL consists of superior and inferior fascicles; however, the stabilizing role of the superior fascicle remains unclear. We biomechanically evaluated its function using cadaveric models. Methods: Nine frozen cadaveric ankles were tested using a robotic system (FRS2015). The superior fascicle was sequentially transected arthroscopically to simulate cumulative 3 injury types: type 1, partial detachment at the medial margin of the fibular attachment; type 2, proximal detachment; and type 3, complete detachment. Anterior talar translation, internal rotation, and inversion angles relative to the tibia were measured as displacements under the anterior drawer, internal rotation, and inversion loads, respectively, at 15° dorsiflexion and 15° and 30° plantarflexion. In situ forces and ankle kinematics were also measured. Results: Internal rotation displacement at 30° plantarflexion was significantly greater in type 3 than in the intact (mean difference, 2.9°; 95% CI, 0.6°-5.0°; P = .01), type 1 (mean difference, 2.6°; 95% CI, 0.5°-4.8°; P = .02), and type 2 (cumulative with type 1; mean difference, 2.5°; 95% CI, 0.4°-4.5°; P = .02). With the numbers available, no significant differences were found among intact, type 1, and type 2, nor in anterior or inversion displacement across any conditions. The in situ force was greater in type 3 than in type 1 during anterior drawer and internal rotation loading, and ankle kinematics did not differ. Conclusion: Partial injury to the superior fascicle of the ATFL was not associated with a statistically significant difference in ankle instability under the tested conditions, whereas complete injury was associated with significantly greater internal rotational displacement. Clinical Relevance: Injury to the superior fascicle of the ATFL is associated with increased internal rotational laxity, supporting the use of internal rotation testing, such as the anterolateral drawer test, when evaluating suspected ATFL injury.